U.S. patent application number 13/695963 was filed with the patent office on 2013-06-13 for spatially controlled energy delivery.
The applicant listed for this patent is Eran Ben-Shmuel, Alexander Bilchinsky, Pinchas Einziger, Amit Rappel. Invention is credited to Eran Ben-Shmuel, Alexander Bilchinsky, Pinchas Einziger, Amit Rappel.
Application Number | 20130146590 13/695963 |
Document ID | / |
Family ID | 44318163 |
Filed Date | 2013-06-13 |
United States Patent
Application |
20130146590 |
Kind Code |
A1 |
Einziger; Pinchas ; et
al. |
June 13, 2013 |
SPATIALLY CONTROLLED ENERGY DELIVERY
Abstract
Apparatuses and methods are disclosed for applying radio
frequency (RF) energy from a source of electromagnetic energy to an
object in an energy application zone. At least one processor may be
configured to acquire information indicative of electromagnetic
energy loss associated with at least a portion of the energy
application zone. The processor may be further configured to
determine a weight to be applied to each of a plurality of
electromagnetic field patterns each having a known electromagnetic
field intensity distribution and cause the source to supply each of
the plurality of electromagnetic field patterns to the energy
application zone at the determined weights.
Inventors: |
Einziger; Pinchas; (Haifa,
IL) ; Ben-Shmuel; Eran; (Ganei Tikva, IL) ;
Bilchinsky; Alexander; (Monosson-Yahud, IL) ; Rappel;
Amit; (Ofra, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Einziger; Pinchas
Ben-Shmuel; Eran
Bilchinsky; Alexander
Rappel; Amit |
Haifa
Ganei Tikva
Monosson-Yahud
Ofra |
|
IL
IL
IL
IL |
|
|
Family ID: |
44318163 |
Appl. No.: |
13/695963 |
Filed: |
May 3, 2011 |
PCT Filed: |
May 3, 2011 |
PCT NO: |
PCT/IB2011/001387 |
371 Date: |
November 2, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61282986 |
May 3, 2010 |
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61282985 |
May 3, 2010 |
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61282984 |
May 3, 2010 |
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61282983 |
May 3, 2010 |
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61282981 |
May 3, 2010 |
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61282980 |
May 3, 2010 |
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Current U.S.
Class: |
219/709 ;
219/748 |
Current CPC
Class: |
H05B 6/64 20130101; H05B
6/72 20130101; H05B 6/6447 20130101; B01J 2219/0871 20130101; H05B
6/705 20130101; B01J 19/129 20130101; H05B 6/686 20130101; Y02B
40/00 20130101; B01J 2219/1203 20130101; G01S 13/89 20130101; B01J
19/126 20130101; Y02B 40/146 20130101; H05B 6/70 20130101; Y02B
40/143 20130101; B01J 2219/1206 20130101; H05B 6/68 20130101; F26B
3/347 20130101 |
Class at
Publication: |
219/709 ;
219/748 |
International
Class: |
H05B 6/64 20060101
H05B006/64 |
Claims
1.-35. (canceled)
36. An apparatus for applying radio frequency (RF) energy from a
source of electromagnetic energy to an object in an energy
application zone via at least one radiating element, the apparatus
comprising: at least one processor configured to: acquire
information indicative of electromagnetic energy loss associated
with at least a portion of the energy application zone; determine,
based on the acquired information indicative of electromagnetic
energy loss, a weight for each of a plurality of electromagnetic
field patterns; and cause the source to excite each of the
plurality of electromagnetic field patterns in the energy
application zone at the determined weights, wherein each weight is
associated with a time duration, a power level, or a combination
thereof.
37. The apparatus of claim 36, wherein the processor is further
configured to: acquire volumetric energy transfer information
associated with at least a portion of the energy application zone;
and determine the weight based on the volumetric energy transfer
information.
38. The apparatus according to claim 36, wherein each of the
plurality of electromagnetic field patterns is associated with a
unique electromagnetic field intensity distribution.
39. The apparatus according to claim 36, wherein the acquired
information indicative of electromagnetic energy loss contains a
three-dimensional distribution of absorption data.
40. The apparatus according to claim 36, wherein the acquired
information indicative of electromagnetic energy loss is
predetermined based on known characteristics of the object.
41. The apparatus according to claim 36, wherein the acquired
information indicative of electromagnetic energy loss is based on
feedback from the object.
42. The apparatus according to claim 36, wherein the processor is
configured to receive signals indicative of feedback from the
object, and determine the acquired information indicative of
electromagnetic energy loss based on the signals.
43. The apparatus according to claim 36, wherein the acquired
information indicative of electromagnetic energy loss includes a
loss profile.
44. The apparatus according to claim 43, wherein the loss profile
is dynamically created.
45. The apparatus according to claim 43, wherein the processor is
configured to generate the loss profile based on feedback from the
object.
46. The apparatus according to claim 36, wherein the processor is
configured to determine the weight based on thermodynamic
characteristics of the object.
47. The apparatus according to claim 46, wherein the thermodynamic
characteristics of the object include at least one of heat
conduction, heat capacity, and a specific mass of at least a
portion of the object.
48. The apparatus according to claim 36, wherein the at least one
radiating element includes two or more radiating elements.
49. The apparatus of claim 48, wherein the processor is configured
to simultaneously employ at least two of the radiating elements in
order to achieve a predetermined field pattern.
50. The apparatus according to claim 36, wherein the at least one
radiating element includes two or more radiating elements, and
wherein the processor is configured to select one or more of the
radiating elements to excite each one of the plurality of
electromagnetic field patterns.
51. The apparatus according to claim 36, further comprising the
source of electromagnetic energy.
52. The apparatus according to claim 36, further comprising the
energy application zone.
53. The apparatus according to claim 36, further comprising the at
least one radiating element.
54. The apparatus according to claim 36, wherein the processor is
further configured to regulate the source to repetitively apply
energy to the energy application zone at an interval of between
about 0.5 seconds and about 5 seconds.
55. An apparatus for applying radio frequency (RF) energy from a
source of electromagnetic energy to an energy application zone via
at least one radiating element, the energy application zone
comprising an object to be processed by the RF energy, the
apparatus comprising a processor configured to: acquire information
indicative of electromagnetic energy loss associated with at least
a portion of the energy application zone; determine a weight to be
applied to each of a plurality of modulation space elements (MSEs),
based on the acquired information indicative of electromagnetic
energy loss; and cause the source to supply RF energy at each of
the plurality of MSEs to the energy application zone at the
determined weights, wherein each weight is associated with a time
duration, a power level, or a combination thereof.
56. The apparatus according to claim 55, wherein each of the
plurality of MSEs is associated with an electromagnetic field
intensity distribution; and the processor is configured to
determine the weight to be applied to each of the plurality of MSEs
based on the electromagnetic field intensity distributions.
57. The apparatus according to claim 55, wherein the processor is
further configured to: acquire a target energy distribution across
at least a portion of the energy application zone; and determine
the weight to be applied to each of the plurality of MSEs based on
the target energy distribution.
58. The apparatus according to claim 55, wherein the processor is
configured to: acquire a target energy distribution across at least
a portion of the energy application zone; and determine the weight
to be applied to each of the plurality of MSEs, such that the sum
of the electromagnetic field intensities associated with each of
the plurality of the MSEs, when weighted by the respective weights,
is substantially equal to the target energy distribution.
Description
OTHER APPLICATIONS
[0001] The present application claims the benefit of priority to
U.S. Provisional Patent Application No. 61/282,980, filed on May 3,
2010; U.S. Provisional Patent Application No. 61/282,981, filed on
May 3, 2010; U.S. Provisional Patent Application No. 61/282,983,
filed on May 3, 2010; U.S. Provisional Patent Application No.
61/282,984, filed on May 3, 2010; U.S. Provisional Patent
Application No. 61/282,985, filed on May 3, 2010; and U.S.
Provisional Patent Application No. 61/282,986, filed on May 3,
2010. Each of these applications is fully incorporated herein in
its entirety.
TECHNICAL FIELD
[0002] This is a provisional application that relates to
apparatuses and methods for applying electromagnetic energy to an
object.
BACKGROUND
[0003] Electromagnetic waves are commonly used to apply energy to
objects. Typically, such objects are located in a cavity configured
to receive electromagnetic energy. However, because the
electromagnetic field distribution may be dependent on the
properties (e.g., size of the object), location, and orientation,
of the object as well as characteristics of the source from which
the energy is applied, it is often difficult to apply
electromagnetic energy in a controllable manner. One example of an
electromagnetic energy application device is a microwave oven. In a
microwave oven, microwaves are used to apply electromagnetic energy
from an energy source to the object through air. The
electromagnetic energy is then absorbed by the object and converted
to thermal energy, causing the temperature of the object to rise.
While typical microwave ovens heat faster than conventional ovens,
a microwave oven will often exhibit hot and cold spots in the
object being heated due to a phenomena known as "standing waves". A
standing wave, also known as a stationary wave, remains in a
constant position and is characterized by local maximum and minimum
amplitudes of electrical field intensity. Because the amplitude of
electrical field intensity is often proportional to the heating
capability of microwaves when an object is present, standing waves
often result in uneven heating of the object, which is usually an
undesirable result.
[0004] Conventional microwave ovens may include designs intended to
reduce uneven heating caused by the standing wave effect. For
example, some conventional microwave ovens utilize field
disturbance elements to disrupt standing waves in a random manner.
In another example, some conventional microwave ovens attempt to
reduce the standing wave effect by rotating the object to be
heated.
SUMMARY
[0005] An aspect of some embodiments of the invention concerns
application of EM energy to an energy application zone in a
controlled manner. In some embodiments, the energy is applied
uniformly, such that all locations within the energy application
zone or an object placed in the energy application zone receive
substantially the same amount of EM energy. In some embodiments,
the energy is applied in a non-uniform manner, such that some
selected regions in the energy application zone or the object
receive more energy than others.
[0006] EM energy is applied to the zone by EM waves. Each wave may
excite in the energy application zone a different field pattern,
and a corresponding field intensity distribution in the energy
application zone.
[0007] In some embodiments, EM energy is applied to the EM zone by
applying selected EM waves to the zone, each with a different field
intensity distribution (may also be referred to as energy profile).
The waves may be selected such that the sum of the intensities of
all the selected waves is substantially the same all over the
energy application zone or the object, although in each point in
space, the field intensity of each wave is different from that of
the others. This kind of energy application may result in uniform
or substantially uniform spatial energy application with respect to
the energy application zone or the object.
[0008] In some embodiments, the waves may be selected such that in
some selected regions of the zone the sum of the intensities of the
selected waves is larger than in other regions. This kind of energy
application may result in non-uniform energy application, where
more energy may be applied to the selected regions.
[0009] It is noted that the energy profile of an EM wave may change
over time, for example, the field intensity may decay with time in
all places. Additionally or alternatively, the field intensity may
oscillate with time, for example, in sinusoidal manner. Other time
evolutions of field patterns are also known to exist.
[0010] Consistent with some embodiments, EM waves may be selected
such that the time average of the energy profile spatially
distributes as required, for example, uniformly. Consistent with
some embodiments, EM waves may be selected such that at each time
the sum of the energy profiles is the same, although the energy
profile of each wave changes with time.
[0011] Some embodiments of the invention may include an apparatus
for applying electromagnetic energy to an object. The apparatus may
include a source of electromagnetic energy and an energy
application zone. At least one processor may be configured to
acquire information indicative of electromagnetic energy loss
associated with the object. The processor may also be configured to
determine a weight to be applied to each of a plurality of
electromagnetic field patterns. Additionally, the processor may be
configured to cause the source to apply each of the plurality of
electromagnetic field patterns to the energy application zone at
the determined weights.
[0012] As used herein, an object (e.g., a processor) is described
to be configured to perform a task (e.g., determine a weight to be
applied to each of a plurality of electromagnetic field patterns),
if, at least in some embodiments, the object performs this task in
operation. Similarly, when a task (e.g., control a distribution of
electromagnetic energy) is described to be in order to establish a
target result (e.g., in order to apply a plurality of
electromagnetic field patterns to the object) this means that, at
least in some embodiments, the task is carried out such that the
target result is accomplished.
[0013] An aspect of some embodiments of the invention includes an
apparatus for applying electromagnetic energy from a source to an
object in an energy application zone via at least one radiating
element. The apparatus may include at least one processor
configured to acquire volumetric energy transfer information
associated with at least a portion of the energy application zone;
determine a weight to be applied to each of a plurality of
electromagnetic field patterns; and cause the source to excite each
of the plurality of electromagnetic field patterns to the energy
application zone at the determined weights. In some embodiments,
each of the field patterns may have a known electromagnetic field
intensity distribution.
[0014] An aspect of some embodiments of the invention may include
an apparatus comprising a processor configured to acquire
indication of amounts of energy to be transferred to at least two
regions in the energy application zone. The processor may further
be configured to determine a weight to be applied to each of a
plurality of MSEs based on the acquired indication. Each of the
MSEs may be associated with an electromagnetic field pattern
distribution, and the weights may be determined such that the
weighted sum of the associated distributions is substantially equal
to the indicated amounts of energy. The processor may be further
configured to cause a source of electromagnetic energy to supply
each of the plurality of MSEs to the energy application zone at the
determined weights.
[0015] An aspect of some embodiments of the invention may include a
method for applying electromagnetic energy from a source of RF
energy to an energy application zone via at least one radiating
element. The method may include acquiring information indicative of
electromagnetic energy losses, each of the losses being associated
with a different portion of the energy application zone; and
determining a weight to be applied to each of a plurality of
electromagnetic field patterns based on the acquired information.
The method may further include exciting each of the plurality of
electromagnetic field patterns in the energy application zone at
the determined weights.
[0016] The preceding summary is merely intended to provide the
reader with a very brief flavor of a few aspects of the invention,
and is not intended to restrict in any way the scope of the claimed
invention. In addition, it is to be understood that both the
foregoing general description and the following detailed
description are exemplary and explanatory only and are not
restrictive of the invention, as claimed.
[0017] It is noted that the term exemplary is used herein in the
sense of serving as an example, instance, or illustration, and not
necessarily as deserving imitation or excellent.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate various
embodiments and exemplary aspects of the present invention and,
together with the description, explain principles of the invention.
In the drawings:
[0019] FIG. 1 provides a diagrammatic representation of an
apparatus for applying electromagnetic energy to an object, in
accordance with some exemplary embodiments of the present
invention;
[0020] FIG. 2 provides a diagrammatic representation of a
rectangular cavity in a Cartesian coordinate system, a cylindrical
cavity in a cylindrical coordinate system, and a spherical cavity
in a spherical coordinate system;
[0021] FIGS. 3A and 3B represent exemplary field patterns in a
modal cavity consistent with principles of the invention;
[0022] FIG. 4A provides a diagrammatic representation of an
apparatus configured to perform frequency modulation on
electromagnetic waves supplied to an energy application zone, in
accordance with some exemplary embodiments of the invention;
[0023] FIG. 4B provides another diagrammatic representation of an
apparatus configured to perform frequency modulation on
electromagnetic waves supplied to an energy application zone, in
accordance with some exemplary embodiments of the invention;
[0024] FIG. 5 provides a diagrammatic representation of an
apparatus configured to perform phase modulation on electromagnetic
waves supplied to an energy application zone, in accordance with
some exemplary embodiments of the invention;
[0025] FIG. 6A provides a diagrammatic representation of an
apparatus configured to perform amplitude modulation on
electromagnetic waves supplied to an energy application zone, in
accordance with some exemplary embodiments of the invention;
[0026] FIG. 6B provides another diagrammatic representation of an
apparatus configured to perform amplitude modulation on
electromagnetic waves supplied to an energy application zone, in
accordance with some embodiments of the invention;
[0027] FIGS. 7A-7C illustrate exemplary energy application zone
discretization strategies in accordance with exemplary embodiments
of the invention;
[0028] FIG. 8 represents an exemplary loss profile in accordance
with some embodiments of the invention;
[0029] FIGS. 9A and 9B represent exemplary spatially controlled
energy delivery methods in accordance with some embodiments of the
invention;
[0030] FIG. 10 is a flow chart of exemplary steps of implementing a
spatially controlled energy delivery method in accordance with some
embodiments of the invention;
[0031] FIG. 11 is a simplified block diagram of a processor
configured to construct a loss profile based on feedback from an
energy application zone, according to some embodiments of the
invention;
[0032] FIGS. 12A, 12B, and 12C illustrate field intensity
distributions of modes that may be excited in an energy application
zone according to some embodiments of the invention; and
[0033] FIGS. 13A and 13B show calculated values of normalized
electric field magnitude of two modes excitable at the same
frequency in a cavity, along an X axis on a cross-section
perpendicular to the Z axis.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0034] Reference will now be made in detail to exemplary
embodiments of the invention, examples of which are illustrated in
the accompanying drawings. When appropriate, the same reference
numbers are used throughout the drawings to refer to the same or
like parts.
[0035] Embodiments of the invention may involve apparatuses and
methods for applying electromagnetic energy to an object in an
energy application zone. As used herein, the term apparatus may
include any component or group of components described herein. For
example, an apparatus may refer only to a processor, such as
processor 30, as illustrated in FIG. 1. Alternatively or
additionally, an apparatus may include a combination of a processor
and one or more radiating elements; a processor, a cavity, and one
or more radiating elements; a processor and a source of
electromagnetic energy; a processor, a cavity, one or more
radiating elements, and a source of electromagnetic energy; or any
other combination of components described herein.
[0036] The term electromagnetic energy, as used herein, includes
any or all portions of the electromagnetic spectrum, including but
not limited to, radio frequency (RF), infrared (IR), near infrared,
visible light, ultraviolet, etc. In some cases, applied
electromagnetic energy may include RF energy with a wavelength of
100 km to 1 mm, which is a frequency of 3 KHz to 300 GHz. In some
cases, RF energy within a narrower frequency range, e.g., 1 MHz-100
GHz, may be applied. Microwave and ultra high frequency (UHF)
energy, for example, are both within the RF range. Even though
examples of the invention are described herein in connection with
the application of RF energy, these descriptions are provided to
illustrate a few exemplary principles of the invention, and are not
intended to limit the invention to any particular portion of the
electromagnetic spectrum. Electromagnetic energy in the RF band may
be referred to as RF energy.
[0037] Similarly, for exemplary purposes, this disclosure contains
a number of examples of electromagnetic energy used for heating.
Again, these descriptions are provided to illustrate exemplary
principles of the invention. The invention, as described and
claimed, may provide benefit for various products and industrial,
commercial, and consumer processes involving the application of
energy, regardless of whether the application of energy results in
a temperature rise. For example, electromagnetic energy may be
applied to an object for heating, combusting, thawing, defrosting,
cooking, drying, accelerating reactions, expanding, evaporating,
fusing, causing or altering biologic processes, medical treatments,
preventing freezing or cooling, maintaining the object within a
desired temperature range, or any other application where it is
desirable to apply energy.
[0038] Moreover, reference to an object (or load) to which
electromagnetic energy is applied is not limited to a particular
form. An object may include a liquid, solid, or gas, depending upon
the particular process with which one or more embodiments of the
invention are utilized, and the object may include composites or
mixtures of matter in one or more differing phases. Further,
although the term object is in the singular, it may refer to
multiple items or detached parts or components. Thus, by way of
non-limiting example, the term object may encompass such matter as
food to be thawed or cooked; clothes or other material to be dried;
frozen material (e.g. organs) to be thawed; chemicals to be
reacted; fuel or other combustible material to be to be combusted;
hydrated material to be dehydrated; gases to be expanded; liquids
to be thawed, heated, boiled, or vaporized; blood or blood
components (e.g. blood plasma or red blood cells) to be thawed
and/or warmed; materials to be manufactured; components to be
connected; or any other material for which there is a desire to
even nominally apply electromagnetic energy.
[0039] In accordance with certain disclosed embodiments, an
apparatus or method may involve the use of an energy application
zone. An energy application zone may include any void, location,
region, or area where electromagnetic energy may be applied. It may
include a hollow, and/or may be filled or partially filled with
liquids, solids, gases, or combinations thereof. By way of example
only, an energy application zone may include the interior of an
enclosure, interior of a partial enclosure (e.g. conveyor belt
oven), interior of a conduit, open space, solid, or partial solid,
which allows for the existence, propagation, and/or resonance of
electromagnetic waves. The zone may be permanent or may be
temporarily constituted for purposes of energy application. For
ease of discussion, all such alternative energy application zones
may alternatively be referred to as cavities, with the
understanding that the term cavity implies no particular physical
structure other than an area in which electromagnetic energy may be
applied.
[0040] The energy application zone may be located in an oven,
chamber, tank, dryer, thawer, dehydrator, reactor, furnace,
cabinet, engine, chemical or biological processing apparatus,
incinerator, material shaping or forming apparatus, conveyor,
combustion zone, or any area where it may be desirable to apply
energy. Thus, the electromagnetic energy application zone may
include an electromagnetic resonator (also known as a cavity
resonator, a resonant cavity, or a cavity). The electromagnetic
energy may be delivered to an object when the object or a portion
thereof is located in the energy application zone.
[0041] An energy application zone may have a predetermined shape
(e.g., a shape determined beforehand) or a shape that is otherwise
determinable. The energy application zone may assume any shape that
permits electromagnetic wave propagation inside the energy
application zone. For example, all or part of the energy
application zone may have a cross-section that is spherical,
hemisphere, rectangular, circular, triangular, oval, pentagonal,
hexagonal, octagonal, elliptical, or any other shape or combination
of shapes. It is also contemplated that the energy application zone
may be closed (e.g., completely enclosed by conductor materials),
bounded at least partially, open, (e.g., having non-bounded
openings), or any other suitable configuration. The general
methodology of the embodiments of the invention is not limited to
any particular cavity shape, configuration, or degree of closure of
the energy application zone, although in some applications, a high
degree of closure may be preferred.
[0042] By way of example, an energy application zone, such as
cavity 20, is represented diagrammatically in FIG. 1, where an
object 50 is positioned in cavity 20. It is to be understood that
object 50 need not be completely located in the energy application
zone. That is, object 50 is considered "in" the energy application
zone if at least a portion of the object is located in the
zone.
[0043] Consistent with some of the presently disclosed embodiments,
electromagnetic waves of at least one wavelength may resonate in
the energy application zone. In other words, the energy application
zone may support at least one resonant wavelength. For example,
cavity 20 may be designed with dimensions permitting it to be
resonant in a predetermined range of frequencies (e.g., the UHF or
microwave range of frequencies, for example, between 300 MHz and 3
GHz, or between 400 MHz and 1 GHZ). It should be noted that, as
used herein, "predetermined" can mean "determined beforehand."
Depending on the intended application, the dimensions of cavity 20
may be designed to permit resonances in other ranges of frequencies
in the electromagnetic spectrum. The term "resonant" or "resonance"
refers to the tendency of electromagnetic waves to oscillate in the
energy application zone at larger amplitudes at some frequencies
(known as "resonance frequencies") than at others. Electromagnetic
waves resonating at a particular resonance frequency may have a
corresponding "resonance wavelength" that is inversely proportional
to the resonance frequency, determined via)=c/f, where .lamda. is
the resonance wavelength, is the resonance frequency, and c is the
propagating speed of the electromagnetic waves in the energy
application zone. The propagating speed may change depending on the
medium through which the wave propagates. Therefore, when the
energy application zone comprises more than one material (for
instance, load and void), c may not be uniquely defined.
Nevertheless, the resonance s may be determined using a slightly
different relation, including, for example, using an estimation
based on c of the major component, an effective c weighted by
different components, an average of the c of miscellaneous
components, or any other technique known in the art.
[0044] Electromagnetic waves in the energy application zone may
exhibit a certain field pattern. A "field pattern" may refer to a
spatial distribution of electromagnetic field. A field pattern may
be characterized by, for example, the amplitude of electric field
intensity distribution in the energy application zone. In general,
electromagnetic field intensity is time varying and spatially
dependent. That is, not only may the field intensity differ at
different spatial locations, but for a given location in space, the
field intensity can vary in time, for example, it may oscillate,
often in a sinusoidal fashion. Therefore, at different spatial
locations, the field intensities may not reach their maximum values
(e.g., their amplitude values, between which the field intensities
may oscillate in time and/or in space) at the same time. Because
the field intensity amplitude at a given location can reveal
information regarding the electromagnetic field, for example
electromagnetic power density and energy transfer capability, the
field pattern referred to herein may include a profile representing
the amplitude of field intensity at one or more spatial locations.
Such a field intensity amplitude profile may be the same as or
different from a snapshot of the instant field intensity
distribution at a given time in the zone. As used herein, the term
"amplitude" is interchangeable with "magnitude".
[0045] A field pattern may be excited by applying electromagnetic
energy to the energy application zone. For example, radiating an
electromagnetic wave of certain frequency and phase may excite in a
given energy application zone a certain electromagnetic field
pattern. As used herein, the term "excited" is interchangeable with
"generated," "created," and "applied". In general, a field pattern
in an energy application zone may be uneven (e.g., non-uniform).
That is, the field pattern may include areas with relatively high
amplitudes of field intensity and other areas with relatively low
amplitudes of field intensity. The rate of energy transfer
(application) from an electromagnetic source to a region in an
energy application zone may depend upon the amplitude of field
intensity excited by the source in the region. For example, energy
transfer may occur faster at areas with higher amplitude of field
intensity than in areas with lower amplitude of field intensity. As
used herein, the term "energy transfer" is interchangeable with
"energy delivery" and "energy application".
[0046] When resonating waves (e.g., standing waves) are present in
the zone, the excited field pattern may be substantially stable in
space over time (e.g., the excited field pattern may exhibit a
static amplitude of field intensity at any given position of the
zone). As a result, the areas with relatively high amplitudes of
field intensity and areas with relative low amplitudes of field
intensity may stay substantially unchanged over time. Such relative
stability of different areas with different characteristics may
allow identification, localization, and utilization of them. For
example, by identifying a location of one or more areas with
relatively high amplitudes of field intensity associated with a
particular field pattern, one may purposely excite this field
pattern and utilize such areas, for example, to transfer
electromagnetic energy to an object by placing the object in such
areas, avoid energy transfer by placing the object outside of such
areas, or transfer energy to certain regions of the object by
controlling the overlap between the object and such areas.
Alternatively, the object itself may stay the same, and the control
of energy transfer may be achieved by exciting different field
patterns and manipulating different areas of high/low amplitude of
field intensity (with known locations, orientations, and/or other
properties) to overlap with the object. Therefore, by controlling
field patterns (e.g., by exciting selected field patterns), the
amount of energy applied to certain regions in an object may be
controlled. This process can be referred to as electromagnetic
spatial filtering.
[0047] A field pattern may be represented as a linear combination
of base field patterns known as "modes." Modes are a set of special
field patterns that are linearly independent from each other. A
mode or a combination of modes (e.g., a general field pattern), can
be of any known type, including propagating, evanescent, and
resonant. In some embodiments of the invention, the excited field
pattern may include a combination of modes. Energy application may
be more effectively controlled by exciting a variety of different
modes in the energy application zone. In some embodiments, a set of
field patterns, or more specifically, modes, may collectively have
substantial field intensity at substantially the entire working
volume of the zone.
[0048] In certain embodiments, an apparatus or method may involve
the use of a source configured to deliver electromagnetic energy to
the energy application zone. A source may include any component or
components suitable for generating and supplying electromagnetic
energy. For example, electromagnetic energy may be supplied to the
energy application zone in the form of electromagnetic waves (also
known as electromagnetic radiation) at predetermined wavelengths or
frequencies. Electromagnetic waves may include propagating waves,
resonating waves, standing waves, evanescent waves, and/or waves
that travel through a medium in any other manner. Electromagnetic
radiation carries energy that may be imparted to (or dissipated
into) matter with which it interacts.
[0049] Referring to FIG. 1, the source may include a power supply
12, which includes one or more components configured to generate
electromagnetic energy. For example, power supply 12 may include a
magnetron configured to generate microwaves at one or more
predetermined wavelengths or frequencies. In some embodiments, the
magnetron may be configured to generate high power microwaves.
Alternatively or additionally, power supply 12 may include a
semiconductor oscillator, such as a voltage controlled oscillator,
configured to generate AC waveforms (e.g., AC voltage or current)
with a constant or varying frequency. AC waveforms may include
sinusoidal waves, square waves, pulsed waves, triangular waves, or
other types of waveforms with alternating polarities. Alternatively
or additionally, a source of electromagnetic energy may include any
other power supply, such as an electromagnetic field generator,
electromagnetic flux generator, or any mechanism for generating
electromagnetic energy.
[0050] In some embodiments, the apparatus may also include at least
one modulator 14 configured to modify one or more characteristics
associated with the electromagnetic energy generated by the power
supply 12. The modulator may or may not be part of the source. For
example, modulator 14 may be configured to modify one or more
characteristics of a waveform, including amplitude (e.g., an
amplitude difference between different radiating elements), phase,
and/or frequency.
[0051] In some embodiments, modulator 14 may include at least one
of a phase modulator, a frequency modulator, or an amplitude
modulator configured to modify the phase, frequency, or amplitude
of the AC waveform, respectively. These modulators are discussed in
greater detail later, in connection with FIGS. 4A, 4B, 5, 6A, and
6B. In some embodiments, modulator 14 may be integrated as part of
power supply 12 or the source, such that the AC waveforms generated
by power supply 12 may have at least one of a varying frequency, a
varying phase, and a varying amplitude.
[0052] The apparatus may also include an amplifier 16 for
amplifying, for example, the AC waveforms before or after they are
modified by modulator 14. The amplifier may or may not be part of
the source. Amplifier 16 may include, for example, a power
amplifier including one or more power transistors. Amplifier 16 may
include a step-up transformer having more turns in the secondary
winding than in the primary winding. In other embodiments,
amplifier 16 may also include one or more power electronic devices
such as bipolar transistors, MOSFETs, thyristors, insulated-gate
bipolar transistors (IGBTs), integrated gate-commutated thyristors
(IGCTs), and any other power electronic devices suitable for
amplifying RF signals. The amplifier may include one or more signal
converters, such as AC-to-AC converters, AC-to-DC-to-AC converters,
or any other suitable type of converters. Alternatively or
additionally, amplifier 16 may include any other device(s) or
circuit(s) configured to scale up an input signal to a desired
level.
[0053] The apparatus may also include at least one radiating
element 18 configured to transfer or apply electromagnetic energy
to object 50. The radiating element(s) may or may not be part of
the source. Radiating element 18 may include one or more waveguides
and/or one or more antennas (also known as power feeds) for
supplying electromagnetic energy to object 50. For example,
radiating element 18 may include slot antennas, dipole antennas,
wire antenna, horn antenna, patch antennas, and other types of
antennas. Additionally or alternatively, radiating element 18 may
include waveguides or antennas of any other kind or form, or any
other suitable structure from which electromagnetic energy may be
emitted.
[0054] Power supply 12, modulator 14, amplifier 16, and radiating
element 18 (or portions thereof) may be separate components or any
combination of them may be integrated together to form a single
unit. Power supply 12, modulator 14, amplifier 16, and radiating
element 18 (or portions thereof) may be parts of the source. For
example, a magnetron may be included in power supply 12 to generate
electromagnetic energy, and a waveguide may be physically attached
to the magnetron for transmitting energy to object 50.
Alternatively or additionally, radiating element 18 may be separate
from the magnetron. Similarly, other types of electromagnetic
generators may be used where the radiating element may be, for
example, physically separate from- or part of the generator or
otherwise connected to the generator.
[0055] In some embodiments, more than one radiating element may be
provided. The radiating elements may be located adjacent to, on, or
in one or more surfaces defining the energy application zone.
Alternatively or additionally, radiating elements 18 may be located
inside and/or outside the energy application zone. When radiating
elements 18 are located outside the zone, they may be coupled to
elements that enable radiated energy to reach the energy
application zone. Elements for allowing the radiated energy to
reach the energy application zone may include, for example, wave
guides and/or antennas. The orientation and configuration of each
radiating element may be distinct or the same, as may be required
for obtaining a target goal, for example, application of a desired
energy distribution in the energy application zone. Furthermore,
the location, orientation, and configuration of each radiating
element may be predetermined before applying energy to object 50.
In certain embodiments, these parameters may be dynamically
adjusted, e.g., using a processor, while applying energy. The
invention is not limited to radiating elements having particular
structures or which are necessarily located in particular areas or
regions. However, placing radiating elements in certain places, or
selecting amplitudes of waves emitted from different radiating
elements in accordance with their location, orientation, and/or
configuration may be used in practicing the invention.
[0056] One or more of radiating element(s) 18 may be configured to
receive electromagnetic energy, optionally, in addition to
radiating electromagnetic energy. In other words, as used herein,
the term radiating element may broadly refer to any structure from
which electromagnetic energy may radiate and/or by which
electromagnetic energy may be received, regardless of whether the
structure was originally designed for purposes of radiating or
receiving energy, and regardless of whether the structure serves
any additional function. An apparatus or method in accordance with
some embodiments of the invention may involve the use of one or
more detectors configured to detect signals associated with
electromagnetic waves received by the one or more radiating
elements. For example, as shown in FIG. 1, a detector 40 may be
coupled to radiating elements 18 that, when functioning as
receivers, receive electromagnetic waves from cavity 20.
[0057] As used herein, the term "detector" may include one or more
electric circuits configured to measure, sense, monitor, etc. at
least one parameter associated with an electromagnetic wave. For
example, such a detector may include a power meter configured to
detect a level of power associated with an incident, reflected
and/or transmitted electromagnetic wave (also known as "incident
power," "reflected power," and "transmitted power", respectively).
Such a detector may also include an amplitude detector configured
to detect an amplitude of the wave, a phase detector configured to
detect a phase of the wave, a frequency detector configured to
detect a frequency of the wave, and/or any other circuit suitable
for detecting a characteristic of an electromagnetic wave.
[0058] In certain embodiments, the source may supply incident power
to a radiating element. In turn, this incident power may be
supplied into the energy application zone by the radiating element.
Of the incident power, a portion may be dissipated by the object
and other structures associated with the zone. This portion of the
incident power dissipated by the object may be referred to as
dissipated power. Another portion of the incident power may be
reflected. This portion of the incident power may be referred to as
"reflected power". Reflected power may include, for example, power
reflected back to the radiating element via the object and/or the
energy application zone. Reflected power may also include power
reflected at the interface between the radiating element and the
zone (e.g., power that is reflected directly at the radiating
element and does not flow into the zone). The rest of the incident
power, other than the reflected power and dissipated power, may be
transmitted to one or more receivers, which, in some embodiments,
may also function as radiating elements. This portion of the
incident power may be referred to as transmitted power. Some energy
(power) may also leak to other places, such as into the walls of
the cavity, through the door, etc. for simplicity, these portions
of the energy (power) are not discussed herein, In some
embodiments, it may be estimated that these portions of the energy
(power) are substantially low and may be negligible.
[0059] In some embodiments, detector 40 may include a directional
or a bi-directional coupler, configured to allow signals to flow
from amplifier 16 to the radiating elements when the radiating
elements function as transmitters (e.g., when radiate to apply
energy to the zone), and to allow signals to flow from the
radiating elements to the detector when the radiating elements
function as receivers (e.g., when the radiating element receive
energy). Additionally or alternatively, the directional coupler may
be further configured to measure the power of a flowing signal. In
some embodiments, the detector may also include other types of
circuits that measure the voltage and/or current of a flowing
signal.
[0060] An apparatus or method of some embodiments of the invention
may involve the use of a processor. As used herein, the term
"processor" may include an electric circuit that executes one or
more instructions. For example, such a processor may include one or
more integrated circuits, microchips, microcontrollers,
microprocessors, all or part of a central processing unit (CPU),
graphics processing unit (GPU), digital signal processors (DSP),
field-programmable gate array (FPGA) or other circuit suitable for
executing instructions or performing logic operations.
[0061] The instructions executed by the processor may, for example,
be pre-loaded into the processor or may be stored in a separate
memory unit such as a RAM, a ROM, a hard disk, an optical disk, a
magnetic medium, a flash memory, other permanent, fixed, or
volatile memory, or any other mechanism capable of providing
instructions to the processor. The processor(s) may be customized
for a particular use, or can be configured for general-purpose use
and perform different functions by executing different
software.
[0062] If more than one processor is employed, all may be of
similar construction, or they may be of differing constructions
electrically connected or independent from one another. They may be
separate circuits or integrated in a single circuit. When more than
one processor is used, they may be configured to operate
independently or collaboratively. They may be coupled electrically,
magnetically, optically, acoustically, mechanically, wirelessly or
in any other way permitting at least one signal to be communicated
between them.
[0063] A single or multiple processors may be provided for the sole
purpose of regulating the source. Alternatively, a single or
multiple processors may be provided with the function of regulating
the source in addition to providing other functions. For example,
the same processor(s) used to regulate the source may also be
integrated into a control circuit that provides additional control
functions to components other than the source.
[0064] In some embodiments, the processor may regulate the source
to generate or excite a desired field pattern in the energy
application zone. For example, the processor may determine and/or
select one or more modulation space elements to generate a desired
field pattern in the energy application zone.
[0065] The term "modulation space" or "MS" is used to collectively
refer to all the parameters that may affect a field pattern in the
energy application zone and all combinations thereof. In some
embodiments, the "MS" may include all possible components that may
be used and their potential settings (either absolute or relative
to others) and adjustable parameters associated with the
components. For example, the "MS" may include a plurality of
variable parameters, the number of antennas, their positioning
and/or orientation (if modifiable), the useable bandwidth, a set of
all useable frequencies and any combinations thereof, power
settings, phases, etc. The MS may have any number of possible
variable parameters, ranging between one parameter only (e.g., a
one dimensional MS limited to frequency only or phase only--or
other single parameter), two or more dimensions (e.g., varying
frequency and amplitude together within the same MS), or many
more.
[0066] Examples of energy application zone-related factors that may
affect the modulation space include the dimensions and shape of the
energy application zone and the materials from which the energy
application zone is constructed. Examples of energy source-related
factors that may affect the modulation space include amplitude,
frequency, and phase of energy delivery. Examples of radiating
element-related factors that may affect the modulation space
include the type, number, size, shape, configuration, orientation
and placement of the radiating elements.
[0067] Each variable parameter associated with the MS may be
thought of as an MS dimension. By way of example, a three
dimensional modulation space may include the three dimensions
designated as frequency (F), phase (.phi.), and amplitude (A). That
is--frequency, phase, and amplitude of the electromagnetic waves
may be modulated during energy application, while all the other
parameters may be predetermined and fixed during energy
application. An MS may also be one dimensional where only one
parameter is varied during the energy application, or may contain
many dimensions that are varied.
[0068] The term "modulation space element" or "MSE" may refer to a
specific set of values of the variable parameters in MS. Therefore,
the MS may also be considered to be a collection of all possible
MSEs. For example, two MSEs may differ one from another in the
relative amplitudes of the energy being supplied to a plurality of
radiating elements. Sequentially swept MSEs may not necessarily be
related to each other. Rather, their MSE variables may differ
significantly from MSE to MSE (or may be logically related). In
some embodiments, the MSE variables may differ significantly from
MSE to MSE, possibly with little or no logical relation among them,
however in the aggregate, a group of working MSEs may achieve a
desired energy application goal.
[0069] The processor may be configured to regulate the source in
order to transfer (apply) different predetermined amounts of energy
to different regions in the energy application zone. For example,
within an energy application zone, it may be desirable to supply a
certain amount of energy in one or more particular regions of the
zone and, at the same time, supply a different amount of energy in
one or more other regions of the zone. The term "region" may
include any portion of the energy application zone, such as a cell,
sub-volume, sub-division, discrete sub-space, or any sub-portion of
a cavity. In one example, the energy application zone may include
two regions. In another example, the energy application zone may
include more than two regions. The regions may or may not overlap
with each other, and the size of each region may or may not be the
same. The terms "region" and "area" are used herein
interchangeably.
[0070] The processor may also be configured to determine and/or
adjust the locations of the regions within the energy application
zone and also to adjust how much energy is supplied to each of
those regions. In some embodiments, the processor may be configured
to determine and/or adjust the locations of the regions according
to the location of an object in the energy application zone. For
example, processor 30 may be configured to monitor a feedback,
e.g., reflective feedback, from the energy application zone to
obtain information about a location of an object in the zone. In
some embodiments, processor 30 may acquire this type of information
through the use of one or more imaging devices. In some
embodiments, the processor may be configured to determine the
location of the regions in correspondence to the location of the
object or to locations of different portions of the object.
Optionally, processor 30 may be configured to cause differing
amounts of electromagnetic energy to be transferred (applied) to
these different portions of the object. The amount of energy
actually dissipated in each region may depend on the field
intensity at that region and the absorption characteristics of the
corresponding portion of the object at that particular region.
[0071] Two regions may be located adjacent to one another within
the energy application zone. For example, the energy application
zone may include a region occupied by an object or a portion of an
object, and another region defining an area distinct from the area
of the object. In this case, these two regions may be adjacent to
each other and separated by a boundary. As an example, the first
region may correspond to a volume of soup within a cup, and the
second region may include the cup that holds the soup and the space
surrounding the cup.
[0072] In another example, the energy application zone may include
two or more regions corresponding to regions within the object that
exhibit differing absorption characteristics. For example, the
first region may correspond to a top layer of soup that contains
mostly water, and the second region may correspond to a bottom
layer of the soup that contains a higher concentration of solids
(e.g., potatoes and/or meat). Because of their differing energy
absorption characteristics, it may be beneficial to excite field
patterns with differing electrical field intensities within these
two regions. Based on the difference in the local field intensities
and the energy absorption characteristics of the two regions, the
dissipated energy in each of the regions may be determined,
optionally predetermined. Accordingly, the dissipated energy may be
made substantially equal or different, as desired, across differing
regions in the object, by selecting and controlling MSEs for
constructing a suitable energy deliver scheme for applying the
energy.
[0073] In order to apply differing targeted amounts of
electromagnetic energy to differing regions (e.g., which may be
defined or known before energy application) in the energy
application zone, processor 30 may select a plurality of MSEs
corresponding to a desired energy delivery scheme. For example, to
transfer more energy to a first region than to a second region, a
selected MSE may excite a field pattern having a higher field
intensity in the first region than in the second. In some
embodiments, in order to transfer more energy to a first region
than to a second region, a selected group of MSEs may excite a
corresponding group of field patterns, the field intensities of
which sum to a higher value in the first region than in the second.
An MSE may include one or more of amplitude, phase, and frequency
of the radiated electromagnetic wave, a location, orientation, and
configuration of each radiating element, or a combination of any of
these parameters and any other controllable or selectable feature
of the apparatus that is capable of affecting the electrical field
pattern.
[0074] For example, as depicted in FIG. 1, an exemplary processor
30 may be electrically coupled to various components of the
apparatus, for example, power supply 12, modulator 14, amplifier
16, and radiating elements 18. These components may or may not form
part of the source. Processor 30 may be configured to execute
instructions to provide physical conditions corresponding to one or
more unique MSEs. For example, processor 30 may be configured to
execute instructions that regulate one or more of these components.
For example, processor 30 may regulate the level of power supplied
by power supply 12. Alternatively or additionally, processor 30 may
also regulate the amplification ratio of amplifier 16, by, for
example, switching the transistors in the amplifier. Alternatively
or additionally, processor 30 may perform pulse-width-modulation
control of amplifier 16 such that the amplifier outputs a desired
waveform. Processor 30 may regulate modulations performed by
modulator 14. Alternatively or additionally, processor 30 may
regulate at least one of location, orientation, and configuration
of each radiating element 18, for instance, through an
electro-mechanical device. Such an electromechanical device may
include a motor or other movable structure for rotating, pivoting,
shifting, sliding or otherwise changing the orientation or location
of one or more radiating elements 18. Processor 30 may be further
configured to regulate any field adjusting elements located in the
energy application zone, in order to change the field pattern in
the zone. For example, the field adjusting elements may be
configured to selectively direct the electromagnetic energy from
the radiating element, or to reduce coupling to other radiating
elements, e.g., radiating elements that act as receivers.
[0075] In accordance with some embodiments of the invention,
processor 30 may regulate the one or more components of the source
and parameters associated with the components, according to a
predetermined scheme. For example, when a phase modulator is used,
it may be controlled to perform a predetermined sequence of time
delays on the AC waveform, such that the phase of the AC waveform
is increased by a number of degrees (e.g., 10 degrees) for each of
a series of time periods. Alternatively or additionally, the
processor may dynamically and/or adaptively regulate apparatus
components, e.g. to regulate modulation, based on feedback from the
energy application zone. For example, processor 30 may be
configured to receive an analog or digital feedback signal from
detector 40, indicating an amount of electromagnetic energy
received from cavity 20, and processor 30 may dynamically determine
a time delay at the phase modulator for the next time period based
on the received feedback signal.
[0076] Processor 30 may also be configured to regulate a frequency
modulator in order to alter a frequency of at least one
electromagnetic wave supplied to the energy application zone. Such
a frequency modulator may be configured to adjust the frequency of
an AC waveform. By way of example, the frequency modulator may
include a semiconductor oscillator, for example oscillator 22
illustrated in FIG. 4A, and may be configured to generate an AC
waveform oscillating at a predetermined frequency. The
predetermined frequency may be in association with an input
voltage, current, or other analog or digital signals. For example,
a voltage controlled oscillator may be configured to generate
waveforms at frequencies proportional to the input voltage,
current, or other suitable input signals.
[0077] In some embodiments, the source may be configured to
transfer electromagnetic energy at a predetermined wavelength that
satisfies a modal condition. The modal condition can be expressed
as a relationship between the applied wavelength .lamda..sub.1 and
the largest resonant wavelength .lamda..sub.0 that may excite a
mode in the energy application zone.
[0078] When the modal condition is satisfied, energy delivery
(transfer) to the object may be better controlled and made more
efficient. In some embodiments, the modal condition may correspond
to a condition in which electromagnetic energy is being delivered
at a wavelength larger than one fourth of the largest resonance
wavelength .lamda..sub.0 in cavity 20, i.e.,
.lamda..sub.1.gtoreq..lamda..sub.0/4. In other embodiments, a
different relationship between the wavelength of the applied
electromagnetic energy supplied by the source and the largest
resonant wavelength supported by the energy application zone may be
applied in order to meet the modal condition. In some embodiments,
the modal condition is met when low order modes are excited, e.g.,
m*n is below 30, 40, or 50 (wherein m and n are integers
representing the mode number in different axes, e.g., x and y).
[0079] Processor 30 may be configured to determine the largest
resonant wavelength .lamda..sub.0. In some embodiments, the largest
resonant wavelength may be known in advance (e.g., programmed into
the processor). The largest resonant wavelength .lamda..sub.0 may
be determined uniquely based on the geometry of cavity 20.
Consistent with some embodiments, the largest resonant wavelength
of any given energy application zone may be determined or estimated
experimentally, mathematically, and/or by simulation. For example,
if the energy application zone corresponds to rectangular cavity
200 (FIG. 2), which is of dimensions a.times.b.times.c, and
a>b>c, then the largest resonant wavelength .lamda..sub.0 may
be given by
2 ab a 2 + b 2 2 ab a 2 + b 2 . ##EQU00001##
As another example, if the energy application zone corresponds to
cubic cavity, which is of dimensions a.times.a.times.a, then the
largest resonant wavelength .lamda..sub.0 may be given by 2a. As
yet another example, if the energy application zone corresponds to
cylindrical cavity 202 (For example as illustrated in FIG. 2) of
radius r and length d, then if 2r>d, the largest resonant
wavelength .lamda.0 may be given by
2 .pi. r 2.405 , ##EQU00002##
and if 2r<d, the largest resonant wavelength .lamda..sub.0 may
be given by
2 .pi. r 1.841 2 + ( .pi. r d ) 2 2 .pi. r 1.841 2 + ( .pi. r d ) 2
. ##EQU00003##
As yet another example, if the energy application zone corresponds
to spherical cavity 204 of radius r, then the largest resonant
wavelength .lamda..sub.0 may be given by
2 .pi. r 2.744 2 .pi. r 2.744 . ##EQU00004##
Once the largest resonant wavelength associated with the energy
application zone is determined, the at least one processor may be
configured to determine the wavelength or wavelengths to be used
for transferring the electromagnetic energy to the energy
application zone, according to the modal condition.
[0080] Alternatively or additionally, the modal condition may be
expressed in terms of frequency. Because there is a relationship
between wavelengths .lamda..sub.1 and .lamda..sub.0 and their
corresponding frequencies f.sub.1 and f.sub.0, such that
f.sub.1=c/.lamda..sub.1 and f.sub.0=c/.lamda..sub.0. The modal
condition may be expressed as f.sub.1<4f.sub.0. That is, the
electromagnetic energy may be applied at a predetermined frequency
that is lower than about four times the lowest resonance frequency
in the energy application zone. In some embodiments, the largest
resonant wavelength may be known in advance (e.g., programmed into
a processor).
[0081] In addition, because the largest resonant wavelength
.lamda..sub.0 has a unique relationship with the dimensions of the
energy application zone, the modal condition may also be expressed
as a relationship between the dimensions of the energy application
zone and the applied wavelength .lamda..sub.1. For example, for a
cubic cavity having dimensions a.times.a.times.a, the modal
condition may be expressed as .lamda..sub.1.gtoreq. 2a/4. As
another example, for spherical cavity 204 (for example as
illustrated in FIG. 2 having radius r, the modal condition may be
expressed as
.lamda. 1 .gtoreq. .pi. r 5.488 .gtoreq. .pi. r 5.488 .
##EQU00005##
A cavity whose dimensions satisfy the modal condition in respect of
electromagnetic energy supplied to the cavity, is referred to
herein as a modal cavity.
[0082] In some cases, the energy application zone may have a
particular region being covered by areas with relatively high
amplitudes of field intensity (e.g., from a certain set of field
patterns) and also by areas with relatively low amplitudes of field
intensity (e.g., from another set of field patterns). Field
patterns may be selectively chosen to target energy application to
selected regions of the energy application zone. For example,
energy applications to any two regions in the energy application
zone may be differentiated from one another by taking advantage of
non-uniform distributions of maximal and minimal amplitudes of
field intensity in each field pattern. In certain embodiments, the
source may be configured and/or controlled to supply
electromagnetic energy in a manner such that relatively low
amplitude field intensities are supplied to predetermined areas of
the energy application zone and higher amplitude field intensities
are supplied to other predetermined areas of the energy application
zone.
[0083] As used herein, an area with relatively high amplitude field
intensity may be referred to as a "hot spot," and an area with
relatively low amplitude field intensity may be referred to as a
"cold spot." Although "hot spots" and "cold spots" may refer to
spatial locations with different temperatures within an object due
to uneven absorption of electromagnetic energy, the same terms may
also refer to spatial locations where the electromagnetic field
intensities have different amplitudes, regardless of whether an
object is present.
[0084] In modal cavity 60, as illustrated in FIGS. 3A and 3B, field
patterns may be excited, such that each has a plurality of hot
spots 62 and 64 (shaded areas) and cold spots (non-shaded areas).
Some of the field patterns excitable in an energy application zone
are named "modes." Modes form a set of special field patterns that
are linearly independent from each other and orthogonal to one
another. As referred herein, two field patterns are orthogonal to
each other if the integral of the scalar product of the two fields
associated with the two modes over the energy application zone is
zero. A mode or a combination of modes (e.g., a general field
pattern), can be of any known type, including propagating,
evanescent, and resonant. In some embodiments, the excited field
pattern includes a combination of modes.
[0085] It is hereby noted that while FIGS. 3A-3B diagrammatically
illustrate hot spots as having a clear and defined border, in
reality the intensity may change in a more gradual manner between
hot spots and cold spots. Furthermore, different hot spots may have
different field intensity amplitudes and/or may have areas with
different field intensity amplitudes within a hotspot. Energy
transfer to the object may occur in all regions of the object that
coincide with regions of the field pattern, where the field pattern
has non-zero field intensity, and is not necessarily limited to
areas coinciding with hot spots. The extent of heating may depend,
among other things, on the intensity of the field to which the
object is exposed and the duration of exposure.
[0086] A field pattern that is excited with a wave having a given
frequency may be represented mathematically as a linear combination
of modes. The modes may include an infinite number of evanescent
modes and a finite number of propagating modes (some of which may
be resonant modes). In general, fewer propagating modes may be
excited in a modal cavity than in a non-modal cavity. Again, some
of the supported propagating modes may be resonant modes. By
nature, the evanescent modes have a very small percent of power (or
energy) out of the total power (or energy) used to excite the field
pattern, and the vast majority of the total power (and energy) is
carried by propagating modes.
[0087] As explained in more detail below, in some embodiments, one
or more radiating elements may be placed such that some undesired
modes may be rejected. For example, many times two or more
propagating modes are effectively excited in an energy application
zone by a single frequency. If the radiating element emitting an
electromagnetic wave at that frequency is positioned at a null of
one of the modes (i.e. at a location wherein one of the modes has
zero field), this mode may be eliminated (i.e., rejected).
[0088] The modal condition and the corresponding modal cavity (i.e.
a cavity that meets the modal condition) may exhibit advantages in
controlling field patterns, or more specifically, modes, in the
energy application zone. As discussed above, in a modal cavity, the
number of propagating modes may be fewer than that in a non-modal
cavity. Therefore, control of these propagating modes may be
relatively easier, for example as the number and density of
antennas used to eliminate undesired modes may be lower if the
modal condition is met. Moreover, minor inaccuracies in control may
have a less prominent overall effect on the hot spot selection in a
modal cavity than in a non-modal cavity, where a relatively higher
number of modes may require finer control in order to achieve a
condition in which one propagating mode is excited and others are
not.
[0089] In one respect, some aspects of the invention involve
selecting an MSE in order to achieve hot/cold spots according to a
desired pattern in an energy application zone. The cold spots
permit controlled application of energy because when it is desired
to avoid applying energy to a portion of an object, a cold spot may
be aligned with that portion. When it is desired to apply energy to
a portion of an object, a hot spot may be aligned with that
portion.
[0090] If a user desires to apply twice the amount of energy to
object 66 than to object 68, the fields patterns of both FIG. 3A
and FIG. 3B may be used, with the former being applied for double
the amount of time at the same power level, at double the power
level for the same amount of time, or for any other time/power pair
that corresponds supplying twice the energy via the field pattern
of FIG. 3A than via the field pattern of FIG. 3B (assuming the
electromagnetic field intensity within hot spot 62 is the same as
that within hot spot 64 and the properties of object 66 are similar
to object 68). This can occur by simultaneously or sequentially
exciting the field patterns of FIGS. 3A and 3B. If the field
intensities differ in the shaded areas, the difference may be taken
into account in order to achieve a desired energy application
profile in the energy application zone or the object, e.g., a
desired energy absorption distribution in the energy application
zone or the object.
[0091] When two field patterns are excited sequentially, the time
average of the field pattern formed in the energy application zone
is the sum of the two excited field patterns. If the field patterns
are excited simultaneously, interference may occur, and then the
time average may be different from the sum. However, if the two
field patterns are orthogonal to each other, as modes are,
sequential and simultaneous application may have the same
result.
[0092] The apparatus of FIG. 1 may be configured to control a
distribution of hot and cold spots in the energy application zone,
thus applying differing target amounts of energy to any two (or
more) particular regions in a an energy application zone, for
example, a cavity or modal cavity. Such control can occur through
the selection and control of MSEs. Choices of MSE selection may
impact how energy is distributed in regions of the energy
application zone. When the modal condition is not met, it may be
more difficult to achieve a desired energy application distribution
through the control of MSEs due to the more complex mathematics
sometimes needed to describe the electromagnetic field and/or more
complicated control schemes required to selectively or effectively
excite a desired field pattern (mode). Thus, the modal condition
may be used in combination with MSE control to achieve a desired
energy distribution. While the modal condition may be used in
combination with MSE control, the modal condition may also provide
benefits even if not used with MSE control. Conversely, MSE control
may be applied even if the modal condition is not met.
[0093] In some embodiments, processor 30 may be configured to
acquire information indicative of electromagnetic energy loss
associated with the object. In some embodiments, "loss" associated
with the object may include any electromagnetic energy that is
applied to the energy application zone in the presence of the
object, but is not reflected back to the transmitting radiating
element and/or transmitted to another receiving element or by any
other detector that detects energy leaking from the zone. In some
embodiments, "loss" associated with the object may be associated or
derived from the energy dissipated by the object.
[0094] In some embodiments, the "loss" associated with the object
is the ability of the object to absorb energy, an ability which is
sometimes indicated by an "absorption coefficient". The loss may
include electromagnetic losses due to ionic conduction (denoted by
.di-elect cons..sub..sigma.''); electromagnetic losses due to
dipole rotation (denoted by .di-elect cons..sub.d''); and/or a
combination of these or other loss components, wherein the total
loss may be denoted as .di-elect cons.'' and characterized, for
example, by:
.di-elect cons.''=.di-elect cons..sub.d''+.di-elect
cons..sub..sigma.''=.di-elect
cons..sub.d''+.sigma.'/(.omega..di-elect cons..sub.0)
where subscripts d and .sigma. stand for contributions of dipole
rotation and ionic conduction, respectively, .sigma.' is the
electric conductivity, .omega. is the angular frequency of the
applied EM wave, and .di-elect cons..sub.0 is the permittivity of
free space or vacuum. Hereinafter, as a shorthand, the total loss
may be denoted by ".sigma.". However, as used herein, the term
"loss" is broadly used to encompass contributions of both .sigma.'
and .di-elect cons..sub.d'', as well as other losses that may be
characterized by an absorption coefficient. By way of example, if
an electromagnetic energy absorbing object is located in the energy
application zone, the loss may represent the electromagnetic energy
absorbing ability of the object. Alternatively, the loss may
represent the electromagnetic energy loss on the boundary of the
energy application zone, regardless of whether there is any object
located in the energy application zone.
[0095] Losses may be characterized in terms of their profiles,
e.g., in terms of their spatial and/or time distribution, generally
referred herein as a loss profile. The term "profile," which also
may be referred to as a pattern, image, distribution, etc., may
include any spatial and/or temporal distribution of loss in the
energy application zone. For example, a loss profile may be a
representation of any absorption coefficient as a function of
location in space. For example, a loss profile may be a map,
showing areas of different absorption coefficient in different
colors. In another example, a loss profile may be a matrix, wherein
each cell represents a volume cell in the energy application zone,
and the value inside the matrix cell is a value of an absorption
coefficient characterizing the medium in at volume cell.
[0096] The loss profile may be represented in various ways that
convey information about the distribution of energy loss in the
energy application zone. For example, the loss profile may be
represented as an image, analytic expressions, a set of numbers, a
table, or any other mechanism capable of reflecting a distribution
of energy loss in the energy application zone or in a portion
thereof.
[0097] When represented as an image or using any imaging
techniques, the loss profile may include a black and white image,
gray-scale image, color image, surface profile image, volumetric
image, or any other graphical depiction. In graphical terms, the
loss profile may be represented, for example, in one-, two-,
three-, and/or four-dimensions, wherein the forth-dimension may
refer to the 3D spatial loss profile over time.
[0098] When represented in tablature, the loss profile may assume
the form of a table, each entry of which may contain an indication
of correlation between a portion of the energy application zone and
the energy absorbed at that portion.
[0099] When represented analytically, a loss profile may, for
example, be written in terms of one or more equations. For example,
such equations may be written as a function of one or more of time,
space, power, phase, frequency, or any other variables that may be
correlated to energy losses.
[0100] When represented numerically, the loss profile may be
expressed as a number or a series of numbers.
[0101] Regardless of the manner of representation, a loss profile
may be expressed in either digital and/or analog formats. For
example, the loss profile may include a digital file stored in a
memory and loadable into a processor. In another example, the loss
profile may be printed on paper or film, or may be represented by a
model made of physical material.
[0102] A loss profile or other information indicative of
electromagnetic energy loss may be acquired by the processor in
numerous ways. For example, the processor may be configured to
receive the information. The information may be encoded in a
machine readable element, for example, a barcode or an RFID tag,
associated with the object, and the processor may be configured to
obtain the information, directly or indirectly, from the machine
readable element. In another example, the information may be
preprogrammed in the processor. For example, the processor may be
preprogrammed with information indicative of electromagnetic energy
loss associated with different objects, and the processor may
receive an image of the object, for example, an image acquired by a
CCD associated the energy application zone, recognize the imaged
object using image recognition techniques, and acquire the relevant
information based on the recognized image.
[0103] In some embodiments, the processor may be configured to
acquire the information by measuring electromagnetic feedback from
the energy application zone (e.g., by receiving signals indicative
of feedback from the object for example from a detector), and by
analyzing the feedback (e.g., signals) to obtain the information.
For example, the processor may be configured to receive an
indication that a field pattern generated by a given MSE was
absorbed particularly well by the object. The processor may be
further configured to determine that the object is located in one
of the high field intensity areas corresponding to that particular
MSE. The more MSEs that are applied to the energy application zone,
the more information the processor may obtain about the location
and the absorptive properties of the object in the energy
application zone. Over a series of such measurements with differing
MSEs, the processor can narrow-in on the location of the object in
the space and/or the spatial distribution of absorptive properties
in the energy application zone, thus acquiring information
indicative of electromagnetic energy loss associated with the
object, portions of the object, and/or empty regions of the energy
application zone. It should be noted that, as used herein, a
processor can include any type of device or equipment that can be
used to receive one or more signals associated with feedback and
perform at least one operation based on the received signals. In
some embodiments, the processor may include a computational device,
such as a mainframe computer, a PC, a digital signal processor, a
microprocessor, or any other type of computing device.
[0104] By way of example only, a loss profile may include a 2D
image, as shown in FIG. 8. It should be understood that the 2D
image shown in FIG. 8 is a simplified example for ease of
discussion. The same general principles explained below with regard
to the simplified 2D image are equally applicable to 3D and 4D
representations. It should also be understood that in the context
of 2D space, the size of the energy application zone is
characterized by area instead of volume.
[0105] FIG. 8 illustrates an energy application zone 810. A loss
profile 820, which may or may not have the same shape and/or size
as the energy application zone, may characterize energy loss (e.g.,
absorption and/or dissipation) in zone 810. The loss profile 820
may reflect the spatial distribution of loss (.sigma.) in the
energy application zone 810. For example, if an object 830 is
located in the energy application zone 810, loss profile 820 may
reflect the energy absorption property of object 830. Additionally
or alternatively, loss profile 820 may reflect the energy
absorption property outside object 830. The loss profile may be
obtained independently of the energy application zone, or the loss
profile may be obtained by taking into account the properties of
the energy application zone. In one example, the loss profile may
be obtained in advance for a known object. In another example, the
loss profile may be dynamically obtained for any object located in
the energy application zone.
[0106] By way of example only, loss profile 820 and energy
application zone 810 may be associated by superposition,
registration, mapping, correlation, zooming, or any other
association methods.
[0107] The loss profile of the energy application zone may be
predetermined (i.e., determined beforehand). Processor 30 may be
configured to determine the loss profile for any given object
placed in the energy application zone. Such a determination may be
accomplished, for example, by implementing a series of steps to
dynamically create a loss profile. For example, the processor may
first determine one or more MSEs to be applied along with a
discretization strategy. Then, the processor may regulate the
source to apply the selected MSEs and generate their corresponding
field patterns in the energy application zone. While applying each
MSE and generating the corresponding field pattern in the zone, the
processor may detect feedback from the zone. For example, the
processor may perform measurements of various quantities, for
example incident power, reflected power, and transmitted power for
each applied MSE/field pattern. Based on this feedback, a set of
equations may be constructed and the processor may be configured to
solve the equations to dynamically create loss profile 820. In
addition or alternatively to dynamically created loss profiles,
processor 30 may be configured to access any other suitable type of
predetermined loss profile. For example, processor 30 may access
loss profiles that are preloaded onto a system as part of a
manufacturing process, generated and stored by the system as part
of a calibration process, generated and stored as a result of any
intermediate or operational process of the system, and/or provided
to the system via a connection to an external memory unit (e.g.,
portable hard drive, optical disk, Internet or other data
connection, memory stick, etc.).
[0108] Processor 30 may be configured to determine a weight to be
applied to each of a plurality of electromagnetic field patterns
each having a unique electromagnetic field intensity distribution.
In some cases the unique electromagnetic field intensity
distributions may be known for one or more of the corresponding
plurality of electromagnetic field patterns. The terms "known
electromagnetic field intensity distribution", "known field
patterns", and the like, may include distributions, field patterns,
etc. that are known, estimated, approximated, or associated with
the field patterns or MSEs based on some features that an
electromagnetic field intensity distribution and the field pattern
may have in common.
[0109] Additionally or alternatively, processor 30 may be
configured to determine a weight to be applied to each of a
plurality of MSEs, based on known electromagnetic field intensity
distributions of the field patterns excited in the energy
application zone with these MSEs.
[0110] The processor may determine the weight and apply the weight
to the corresponding MSE of the field pattern, thereby achieving
weighted field patterns in the energy application zone. Application
of the weight may be, for example, by way of determining a power
level, time duration, or combination thereof, to be proportional to
the weight. For example, field patterns may be applied all in the
same power level, and patterns with larger weight may be applied
for a longer duration. In other examples, field patterns may be
applied all for the same duration, and patterns with larger weight
may be applied at higher power. Still in other examples, both
duration and power may change from one field pattern to another,
and field patterns with larger weight may be applied at such powers
and durations that the product of the power by the time duration is
larger than that at which a field pattern of smaller weight is
executed.
[0111] The field pattern may be a function of the physical
characteristics of the energy application zone, controllable
aspects of the energy source, the type, number, size, shape,
configuration, orientation, location, and/or placement of the
radiating elements, the presence of field altering structures such
as field adjusting elements (FAEs) and/or dielectric lenses, and/or
any other variable that may affect the field pattern. For any
particular energy application zone, a set of known field patterns
may be achieved, for example, by supplying energy to the energy
application zone at different MSEs, which may differ from each
other by frequency, phase, and/or amplitude of one or more energy
sources; by the type, number, size, shape, configuration,
orientation, location, and/or placement of one or more radiating
elements; by operation of field adjusting elements, for instance,
by adjustments of dielectric lenses or other field adjusting
elements; or by other variable components that affect MSEs.
[0112] Different MSEs may lead to differing field patterns, which
affect the distribution of energy across the energy application
zone. Because an infinite number of MSEs may be available, there
may be an infinite number of different field patterns and resulting
energy distributions that can be achieved in a particular energy
application zone. The number of different energy distribution
options in practice, however, may be related to the number of MSEs
and/or the number of combinations of MSEs that are practically
useable.
[0113] A particular MSE may correspond to a particular field
pattern. For many MSEs, their corresponding field patterns may be
known or determined in advance. For example, if a set of MSEs is
chosen to be applied to a rectangular energy application zone, and
frequency is the only controllable variable of each MSE, then the
field pattern corresponding to each MSE may be obtained by
calculating equations using the dimensions of the energy
application zone, frequencies of the MSEs, and other necessary
parameters. Alternatively or additionally, such field patterns may
be determined by conducting simulations using computer programs.
Other methods including measurements (e.g., real-time measurements)
may also be used to determine the field patterns corresponding to
the set of MSEs. The measurements may be obtained `on the fly`,
e.g., during a heating process, for example by detecting one or
more inputs from one or more sensors (detectors) provided in the
energy application zone. These inputs (measurements) may be used to
predict an actual field pattern (e.g., the excited field
pattern).
[0114] On the other hand, a particular field pattern may correspond
to more than one MSE. For example, a particular field pattern may
be achieved by using a single radiating element or multiple
radiating elements. Further, the same field pattern may also be
achieved by using more than one source with certain phase
differences. Other MSEs may also be used to achieve the same field
pattern. Therefore, there may be multiple choices of MSEs to
generate a desired field pattern, and the selection of MSE(s) may
be dependent on factors such as ease of implementation,
controllability, cost, and other design considerations.
[0115] Processor 30 may implement the steps as shown in FIG. 10 to
implement a particular exemplary method for achieving spatial
control over energy delivery (application). In step 1020, the
processor may determine a set of MSEs to be used in the process. As
discussed previously, an MSE may correlate to a known field
pattern. Therefore, by determining a set of MSEs, the processor may
control the source to apply electromagnetic energy to the energy
application zone and generate a set of known field patterns in the
zone. In some embodiments, step 1020 may be omitted, and all the
available MSEs may be considered for purpose of generating a
desired field pattern in the energy application zone. It may be
expected that, at least in some cases, one or more of the available
MSEs will be assigned negligible weights, and therefore will not be
used in practice, even if step 1020 is omitted.
[0116] The method of constructing a controlled field pattern inside
the energy application zone from a predetermined set of field
patterns is termed as "spatial filtering." The term "filtering"
refers to an ability to discriminate spatial locations and the
field intensities applied to them in terms of a set of known field
patterns. Because the controllable MSEs are related to the
predetermined set of field patterns, it may be possible to
represent any field pattern in terms of one or more MSEs, at least
to some level of accuracy. As discussed previously, there may be
more than one MSE available to achieve a particular field pattern.
Therefore, the choice of MSE to achieve a particular field pattern
may be application dependent.
[0117] Returning to step 1020, the processor may determine and
implement the MSEs in a variety of ways depending of the
requirements of a particular application. In one example, the
processor may control the energy source to supply EM energy at a
plurality of selected frequencies. In this case, frequency may
serve as controllable variable that can be used to provide a
desired MSE. Alternatively or additionally, the processor may
control the energy source to supply EM energy in a plurality of
selected amplitudes. In this case, amplitude may serve as a
controllable MSE variable.
[0118] In some embodiments, an MSE is a combination of variables
and it may be possible to change the MSE by altering a single
variable or multiple variables. By way of a simplified example, the
processor may control the energy source to supply EM energy with
two frequencies: f.sub.1 and f.sub.2; and two amplitudes: A.sub.1
and A.sub.2. In this case, the available MSEs may be [(f.sub.1,
A.sub.1), (f.sub.1, A.sub.2), (f.sub.2, A.sub.1), (f.sub.2,
A.sub.2)]. That is, the processor may control the energy source to
supply a first EM energy at frequency f.sub.1 and amplitude
A.sub.1, a second EM energy with frequency f.sub.1 and amplitude
A.sub.2; a third EM energy with frequency f.sub.2 and amplitude
A.sub.1; and a fourth EM energy with frequency f.sub.2 and
amplitude A.sub.2. The available MSEs can be represented in matrix
form as:
[(f.sub.1,A.sub.1),(f.sub.1,A.sub.2)(f.sub.2,A.sub.1),(f.sub.2,A.sub.2)]-
.
In this simple example, only two frequencies and two amplitudes are
available and, therefore, the MSE matrix is a 2.times.2 matrix. If
more frequencies and amplitudes are available, the MSE matrix may
be expanded accordingly. For example, if 10 frequencies and 5
amplitudes are available, the MSE matrix may become a 10.times.5
matrix, with each row of the matrix having the same frequency value
but different amplitude values, and each column of the matrix
having the same amplitude value but different frequency values. If
more or less types of controllable MSE variables are available, the
dimension of the MSE matrix may be changed accordingly. For
example, if the phase (P) of the EM energy is also controllable,
the MSE matrix may become a 3D matrix, with each element of the
matrix in a form of (fi,Aj,Pk). Here the subscripts i, j, and k
represent indices of available frequency, amplitude, and phase,
respectively. The size of the matrix may be represented as
N.sub.f.times.N.sub.A.times.N.sub.P, where N.sub.f, N.sub.A, and
N.sub.P represent the available number of controllable frequencies,
amplitudes, and phases, respectively. If only one controllable
parameter is available, the matrix may degenerate to a 1D
vector.
[0119] In addition to the frequency, amplitude, and phase, any
controllable parameter that may effectively change the field
pattern inside the energy application zone may be part of the MS.
For example, the number of radiating elements for radiating
(applying) EM energy to the energy application zone may constitute
another controllable parameter, which corresponds to an additional
dimension of the MS. In another example, the
placement/location/orientation of the radiating element(s) may
constitute additional dimensions of the MS. In this case, the
placement/location/orientation of the radiating element(s) may be
physically changed in space by mechanical, electrical, or other
suitable means. Alternatively, there may be provided an array of
radiating elements, and the desired placement/location/orientation
may be achieved by selecting a particular radiating element or any
subset of the radiating elements in the array. The
placement/location/orientation of radiating element(s) may also be
adjusted by any combination of the aforementioned methods. In yet
another example, there may be provided a field adjusting element
(FAE), such as a conducting structure, inside the energy
application zone. The placement/location/orientation of the FAE may
be adjusted in the similar manner as that of the radiating element.
Processor 30 may be configured to select from among the full range
of available MSEs and assemble a set of MSEs such that the
resulting combination of field patterns may satisfy the energy
application requirements of a particular application.
[0120] For any combination of MSE variables that constitutes an
MSE, those variables in the combination should represent physically
attainable conditions. For example, if in a given apparatus only
one antenna and one source are available, and the source can only
output EM waves at a single frequency, then a valid MSE cannot
include more than one frequency in its MSE variables, as multiple
frequencies cannot coexist in this example. Instead, an MSE in the
given apparatus may include waves of the given frequency, at
different phases, and/or amplitudes as its valid MSE variables. In
another exemplary apparatus, two antennas and two sources (or more)
are available, an MSE may include different frequencies for
different antennas/sources. In this example, more than one
frequency could be included among the valid MSE variables. In
general, an MSE may include, among other controllable quantities
and/or parameters, one or more of amplitude, phase, and frequency
of the applied electromagnetic wave; a location, orientation, and
configuration of each radiating element; or the combination of any
of these parameters that may coexist.
[0121] MSE selection may impact how energy is distributed in
regions of the energy application zone. Processor 30 may control
one or more MSEs in order to achieve a field pattern that targets
energy to a specific predetermined region in the energy application
zone. A selection of MSEs that result in standing waves may provide
an added measure of control because standing waves exhibit
predictable and distinctly defined hot spots and cold spots. While
use of MSEs to control energy distribution may have benefits in a
non-modal cavity, a modal cavity may provide a medium especially
suitable for achieving MSE control. In another example, when a
phase modulator is used, it may be controlled to perform a
predetermined sequence of time delays on an AC waveform (emitted by
a radiating element), such that the phase of the AC waveform is
increased by a number of degrees (e.g., 10 degrees) for each of a
series of time periods. Alternatively or additionally, processor 30
may dynamically and/or adaptively regulate modulation based on
feedback from the energy application zone. For example, processor
30 may be configured to receive an analog or digital feedback
signal from detector 40, indicating an amount of electromagnetic
energy received from cavity 20 (e.g., an amount of energy reflected
to the transmitting radiating element and/or amount of energy
transmitted to other receiving radiating element(s)), and processor
30 may dynamically determine a time delay at the phase modulator
for the next time period based on the received feedback signal. The
processor may also be configured to regulate a frequency modulator
in order to alter a frequency of at least one electromagnetic wave
supplied to the energy application zone. Such a frequency modulator
may be configured to adjust the frequency of an AC waveform. By way
of example, the frequency modulator may include a semiconductor
oscillator, such as oscillator 22 diagrammatically depicted in FIG.
4A, configured to generate an AC waveform oscillating at a
predetermined frequency. The predetermined frequency may be
associated with an input voltage, current, or other analog or
digital signals. For example, a voltage controlled oscillator may
be configured to generate waveforms at frequencies proportional to
the input voltage.
[0122] Consistent with some embodiments, processor 30 may be
configured to regulate oscillator 22 to generate AC waveforms of
time-varying frequencies. For example, oscillator 22 may generate a
sinusoidal signal cos[.omega.(t)t]. The AC signal may be amplified
by amplifier 24 and cause radiating elements, e.g., antennas 32 and
34 (illustrated for example in FIG. 4A), to excite frequency
modulated electromagnetic waves in cavity 20.
[0123] Processor 30 may be configured to regulate oscillator 22 to
sequentially generate AC waveforms oscillating at various
frequencies within a predetermined frequency band. This sequential
process may be referred to as "frequency sweeping". More generally,
processor 30 may be configured to regulate the source to
sequentially generate waveforms at various MSEs, e.g. at various
frequencies, phases, amplitudes, and/or selections of radiating
elements. Such a sequential process may be referred as "MSE
sweeping". Sequentially swept MSEs may not necessarily be related
to each other. Rather, their MSE variables may differ significantly
from MSE to MSE (or may be logically related). In some embodiments,
the MSE variables may differ significantly from MSE to MSE,
possibly with little or no logical relation among them, however in
the aggregate, a group of working MSEs may achieve a desired energy
application goal.
[0124] In such exemplary embodiments (e.g., in frequency sweeping),
each frequency may be associated with a feeding scheme (e.g., a
particular selection of MSEs). In some embodiments, based on the
feedback signal provided by detector 40, processor 30 may be
configured to select one or more frequencies from the frequency
band, and regulate oscillator 22 to sequentially generate AC
waveforms at these selected frequencies.
[0125] Alternatively or additionally, processor 30 may be further
configured to regulate amplifier 24 to adjust amounts of energy
delivered via antennas 32 and 34, based on the feedback signal.
Consistent with some embodiments, detector 40 may detect an amount
of energy reflected from the energy application zone at a
particular frequency, and processor 30 may be configured to cause
the amount of energy delivered at that frequency to be high when
the reflected energy is high. That is, processor 30 may be
configured to cause one or more radiating elements to deliver
energy at a particular frequency over a longer duration when the
reflected energy is high at that frequency. For example, when the
reflected energy measured indicates that a certain frequency is
absorbed relatively poorly in the object, it may be desirable to
apply more energy at that frequency to compensate for the poor
absorption. Alternatively or additionally, processor 30 may be
configured to cause one or more radiating elements to apply energy
at a particular frequency over a longer duration when the reflected
energy is low at that frequency. Other relationships between
amounts of reflected and applied energy may also be used.
[0126] As depicted in FIG. 4B, some embodiments of the invention
may include a source with more than one EM energy generating
component, such as oscillators 22 and 26 for generating AC
waveforms of differing frequencies. The separately generated AC
waveforms may be amplified by amplifiers 24 and 28, respectively.
Accordingly, at any given time, antennas 32 and 34 may be caused to
simultaneously apply electromagnetic waves at two differing
frequencies to cavity 20. One or both of these two frequencies may
be time-varying. FIG. 4B illustrates two oscillators for exemplary
purposes only, and it is contemplated that within the scope of the
invention more than two oscillators (and/or more than two
amplifiers and/or more than two antennas) may be used.
[0127] Processor 30 may be configured to regulate a phase modulator
in order to alter a phase difference between two electromagnetic
waves supplied to the energy application zone. By way of example,
the phase modulator may include a phase shifter, such as phase
shifter 54, as illustrated in FIG. 5. Phase shifter 54 may be
configured to cause a time delay in the AC waveform in a
controllable manner within cavity 20, delaying the phase of an AC
waveform anywhere from between 0-360 degrees. Phase shifter 54 may
include an analog phase shifter configured to provide a
continuously variable phase shift or time delay, or phase shifter
54 may include a digital phase shifter configured to provide a
discrete set of phase shifts or time delays.
[0128] A splitter 52 may be provided to split the AC signal
generated by oscillator 22 into two AC signals (e.g., split
signals). Processor 30 may be configured to regulate phase shifter
54 to sequentially cause various time delays such that the phase
difference between the two split signals may vary over time. This
sequential process may be referred to as "phase sweeping."
[0129] In general, processor 30 may sweep various parameters,
alternatively or additionally to the above-described frequency
sweeping and phase sweeping, to perform MSE sweeping. MSE sweeping
may include sequential change of any parameter that affects the
field pattern generated in the energy application zone.
[0130] Processor 30 may be configured to regulate an amplitude
modulator in order to alter an amplitude of at least one
electromagnetic wave supplied to the energy application zone. By
way of example, the amplitude modulator may include a mixer
circuit, e.g., mixer 42 illustrated in FIG. 6A, configured to
regulate an amplitude of a carrier wave with another modulating
signal. For example, oscillator 22 may be configured to generate a
higher frequency AC signal, and oscillator 26 may be configured to
generate a lower frequency AC signal. The two AC signals may be
mixed by mixer 42 into one AC signal oscillating at the higher
frequency, and the amplitude of the mixed AC signal may vary
according to the lower frequency AC signal. For example, if the
higher frequency signal is a sinusoidal signal cos[.omega..sub.1t]
and the lower frequency signal is another sinusoidal signal
cos[.omega..sub.2t], then the mixed signal may become
cos[.omega..sub.1t] cos[.omega..sub.2t]. The mixed signal may then
be amplified by amplifier 44 so that antennas 32 and 34 may radiate
electromagnetic waves in the amplified waveform.
[0131] Consistent with some embodiments, the amplitude modulator
may include one or more phase shifters, such as phase shifters 54
and 56, as shown in FIG. 6B. In accordance with some embodiments of
the invention, amplitude modulation may be implemented by combining
two or more phase shifted electromagnetic waves. For example,
splitter 52 may split the AC signal generated by oscillator 22 into
two AC signals, for example sinusoidal waves cos[.omega.t]. Because
they are split from a single signal, the two split AC signals may
share substantially the same frequencies. One split AC signal may
be shifted by phase shifter 54 for phase .alpha., so that the AC
signal becomes cos[.omega.t+.alpha.]. The other split AC signal may
be shifted by phase shifter 56 for phase -.alpha. (or equivalently
360.degree.-.alpha.), so that the AC signal becomes
cos[.omega.t-.alpha.].
[0132] As illustrated in FIG. 6B, the phased shifted AC signals may
be amplified by amplifiers 24 and 28 respectively, and in this
manner, antennas 32 and 34 may be caused to excite electromagnetic
waves having a shared AC waveform. Antennas 32 and 34 may be
positioned a predetermined distance from each other so that the two
electromagnetic waves excited by the antennas may form an amplitude
modulated wave, according to the trigonometric identity
cos[.omega.t-.alpha.]+cos[.omega.t+.alpha.]=2 cos(.alpha.)
cos(.omega.t). As with the other examples provided, FIG. 6B is
exemplary only, as one, two, or more phase shifters can be employed
depending on the requirements of a particular application.
[0133] Although FIGS. 4A-4B, 5, and 6A-6B illustrate circuits for
altering frequency, phase, and amplitude modulations individually,
components of these circuits may be combined in order to enable
multiple MSE variable combinations. Moreover, a plurality of
radiating elements may be employed, and the processor may select
combinations of MSEs through selective use of radiating elements.
By way of example only, in an apparatus having three radiating
elements A, B, and C, amplitude modulation may be performed with
radiating elements A and B, phase modulation may be performed with
radiating elements B and C, and frequency modulation may be
performed with radiating elements A and C. Alternatively or
additionally, amplitude may be held constant and field changes may
be caused by switching between radiating elements. Further,
radiating elements 32 and 34 may include a device that causes their
location or orientation to change, thereby causing field pattern
changes. The combinations are virtually limitless, and the
invention is not limited to any particular combination, but rather
reflects the notion that field patterns may be altered by altering
one or more MSEs.
[0134] Although changes in MSE selection may result in significant
changes in field patterns, field patterns corresponding to a given
set of MSEs may be predictable. The field patterns that result from
any particular set of MSEs may be determined, for example, through
testing, simulation, or analytical calculation. Using the testing
approach, sensors (e.g., small antennas) can be placed in an energy
application zone to measure the electromagnetic field distributions
that result from a given set of MSEs. The field patterns can then
be stored in, for example, a look-up table. The testing approach
may be conducted in factory or on site. In a simulated approach, a
virtual model may be constructed so that field patterns
corresponding to a set of MSEs can be tested in a virtual manner.
For example, a simulation model of an energy application zone may
be performed in a computer based on a set of MSEs inputted to the
computer program. A simulation engine such as CST or HFSS may be
used to numerically calculate the field distribution inside the
energy application zone for any given MSE, e.g., based on the
inputs provided. The resulting field pattern may be visualized
using imaging techniques or stored in a computer as digital data.
The correlation between MSE and resulting field pattern may be
established in this manner. This simulated approach can occur in
advance, and the known field patterns may be stored in a look-up
table. Alternatively or additionally, the simulation can be
conducted on an as-needed basis during an energy application
operation.
[0135] As an alternative or addition to testing and simulation,
calculations may be performed based on an analytical model in order
to predict field patterns based on selected set of MSEs. For
example, given the shape of an energy application zone with known
dimensions, the basic field pattern corresponding to a particular
MSE may be calculated from analytical equations. As with the
simulated approach, the analytical approach may occur in advance,
and the known field patterns may be stored in a look-up table.
Additionally or alternatively, the analytical approach may be
conducted on an as-needed basis during an energy application
operation.
[0136] Returning to FIG. 10, as shown in step 1030, processor 30
may acquire a loss profile of the energy application zone. In some
embodiments, the loss profile may be pre-determined. The loss
profile may be stored in a memory unit and acquired by the
processor by reading the stored profile from the memory unit. For
example, if the energy application zone is dedicated for applying
energy to a known object, the loss profile of the object may be
acquired by pre-measurement, simulation, or calculation.
Additionally or alternatively, the loss profile may be dynamically
determined by the processor, as discussed in previous sections. For
example, an initial loss profile may be acquired by
pre-measurement; and during processing, updated loss profiles may
be dynamically determined. In addition to acquiring a loss profile,
step 1030 may also include a sub-step to determine discretization
strategy. If the loss profile includes discretization information
of the energy application zone, the processor may use the same
discretization strategy as the loss profile.
[0137] Alternatively, the processor may determine a different
discretization strategy. For example, in step 1030, the processor
may be configured to determine a discretization strategy to divide
the energy application zone into a plurality of regions. The term
discretization may refer to any division, separation, and/or
partitioning of the energy application zone or a representation
thereof into regions. The discretization of the energy application
zone into regions may be predetermined. In one case, the processor
may acquire the predetermined discretization information, through,
for example, a look up table, information stored in memory, or
information encoded in the processor. Alternatively or
additionally, discretization may occur dynamically. For example, an
initial discretization may be predetermined, and changed
dynamically, for instance, to improve the stability of a solution
of a set of equations.
[0138] In some embodiments, the discretization may be in a
predetermined manner, for instance, denser at the center of a tray
positioned in the energy application zone, where an object is
likely to be positioned, and sparser near the edges of the energy
application zone. In some embodiments, discretization may be in
accordance with information about the object, for example, in
accordance with the following logic. At first, the processor may
receive, for example, from a user, information regarding positions
of objects within the energy application zone, and the spatial
distribution of their dielectric property, for example, a given
volume is occupied by water, and in another location there is a
piece of bread. Each volume characterized by essentially uniform
dielectric properties (in the above example the water or the bread)
may be defined as one region for purpose of discretization. At
times, an object of uniform dielectric properties and irregular
shape is discretized to several regions, each with a more regular
shape. Alternatively or additionally, the discretization may be set
in accordance with the amount of energy to be applied to different
regions. For example, if a temperature gradient is required along a
given volume, this volume may be discretized to many regions, to
facilitate designing a combination of MSEs that result in the
required temperature gradient. Additionally or alternatively, the
discretization strategy is chosen considering the required
computation time and/or the accuracy and reliability required by
the user, and/or the stability of the mathematical solution of
equations 4 and/or 5 below. For example, too large a number of
discrete regions might reduce the stability of the mathematical
solution. On the other hand, if the number of discrete regions is
too small, it may be impossible to find a solution at all. In some
embodiments, the processor starts with a first discretization
scheme where the number of regions is minimal, and if solution is
found to be impossible, the number of regions may be increased. If
a solution is possible, the equations are solved. If the solution
is not sufficiently accurate (for example, the differences between
the obtained energies and the target energies is close to the upper
allowed limit), discretization to more regions may be tried.
Alternatively or additionally to the number of regions, in some
embodiments the processor may be configured to change the shape
and/or location of borders between regions. It is noted that if a
given set of equations is found not solvable, alternatively or
additionally to changing the discretization strategy or scheme,
other options may exist. For example, deleting an equation that has
a major contribution to the instability but has small contribution
to the solution, and other methods known per se in the art of
solving sets of linear equations numerically.
[0139] To further illustrate the discretization principle, energy
application zone 810 in FIG. 8 may be divided in such a manner that
object 830 occupies a single region. In another example, energy
application zone 810 may be divided in such a manner that object
830 occupies multiple regions, as shown in FIG. 8. The
discretization strategy may depend on many factors, including but
not limited to a desired resolution, properties of the loss
profile, and/or available field patterns.
[0140] In some embodiments, a resolution of the different regions
(for example, to which different amounts of energy are applied)
and/or a resolution of a discretization of the zone (e.g., the zone
may be divided into a plurality of regions) may be a fraction of
the wavelength of the applied EM energy, e.g., on the order of
.lamda./10, .lamda./5, .lamda./2. For example, for 900 MHz, the
corresponding wavelength (.lamda.) in air (.di-elect cons.=1) is
33.3 cm and the resolution may be on the order of 3 cm, e.g., (3
cm).sup.3 or 1 (mm).sup.3resolution. In water, for example, the
wavelength is approximately 9 times shorter at the same frequency
(900 MHz), thus the resolution may be in the order of 0.33 cm,
e.g., (0.33 cm).sup.3. In meat, for example, the wavelength
corresponding to frequency of 900 MHz is about 7 times shorter than
in air and the resolution may be in the order of 0.4 cm, e.g., (0.4
cm).sup.3. Using higher frequencies may allow for higher
resolution. For example, in other frequencies, the resolution may
be in the order of: 0.1 cm, 0.05 cm, 0.01 cm, 5 mm, 1 mm, 0.5 mm,
0.1 mm, 0.05 mm or less.
[0141] For example, if the size of object 830 is S.sub.L (a.u.),
and a desired resolution may require the object to include at least
100 regions, then the average size of each region may be, for
example, S.sub.L/100. The size of different regions may or may not
be the same. In certain locations of the object, the size of the
divided regions may be smaller than in other locations. In other
words, the density of regions may vary across the entire
object.
[0142] For example, the dividing strategy may vary depending on
whether a region corresponds to a portion of an object in the
energy application zone that is targeted for energy application;
whether the region corresponds to a region of the zone where no
portion of the object is located; or to a region comprising a
portion of the object that is not targeted for energy application
(each of the two latter regions may be termed as "void zones"). For
example, in one optional strategy, the entire void zone may be
treated as a single region. In another exemplary strategy, the void
zone may be divided into a plurality of regions in a similar manner
as inside the object. In this case, the dividing may be carried out
in the entire energy application zone, regardless of the spatial
occupation of the object. Alternatively, the dividing may be
carried out separately for the zone occupied by the object and the
void zone. In yet another example, the void zone may be divided
into a plurality of regions in a different manner than that in the
object. For example, the average size of regions in the void zone
may be larger than that inside the object. In other words, the
density of regions in the void zone may be lower than that inside
the object (e.g., object 50). As illustrated in FIG. 7C, the
discretization is denser in the object but sparser in the void
space. The regions may be of a regular or irregular shape. For
example, in 3D cases, the regions may be regular cubic- or
rectangular-shaped, as illustrated in FIG. 7A. Alternatively, the
regions may include any irregular-shape depending on particular
needs. For example, the energy application zone may be divided into
somewhat random regions as shown in FIG. 7B.
[0143] While the discussion above describes examples of
discretization strategies that may be employed, any suitable
discretization strategy can be used. A discretization strategy in
accordance with some embodiments of the invention, for example, may
include any suitable method for causing the processor to represent
the energy application zone as multiple regions, regardless of
whether those regions are uniform in size or shape, and regardless
of whether the discretization results in any recognizable
pattern.
[0144] An exemplary process for constructing a loss profile is
discussed below in connection with FIG. 8, where energy application
zone 810 may be divided into multiple regions, with each region
having substantially the same regular squared shape. However, it is
contemplated that the method described below may be applied to
discretizations where zone 810 is divided into regions of irregular
shapes and/or unequal sizes. The regions may be labeled from the
upper left corner to lower right corner as 1, 2, 3, . . . ,
N.sub.d. Object 830, which may occupy multiple regions, e.g.,
regions R.sub.a and R.sub.b, may include two kinds of materials
having differing loss parameters .sigma..sub.a and .sigma..sub.b.
The void region R.sub.0, which is outside the object but inside the
energy application zone, has the loss parameter .sigma..sub.0. The
objective of the process is to create a loss profile of energy
application zone 810 that approximates the real loss profile
characterized by .sigma..sub.a, .sigma..sub.b, and .sigma..sub.0.
To achieve this objective, the processor assigns each region (1 to
N.sub.d) an unknown loss parameter .sigma..sub.i (i=1, 2, 3, . . .
, N.sub.d). Such discretized .sigma..sub.i is a numerical
representation of the real loss profile with a resolution
characterized by N.sub.d. For example, if N.sub.d is large, there
may be a large number of regions inside the energy application
zone, and the size of each region may be small.
[0145] In FIG. 8, there may be provided two radiating elements 840
(for example antennas) to apply EM energy to energy application
zone 810. In some embodiments, the MSEs determined in step 1020
are, for example, phase differences between two radiating elements
840, and the MSEs are represented by [.theta..sub.1, .theta..sub.2,
. . . .theta..sub.Nm]. The same notation may be used also for any
other kind of MSE. As discussed earlier, each MSE may correspond to
a known field pattern inside the energy application zone (e.g.,
zone 810). Because the energy application zone has been discretized
into N.sub.d regions, for each MSE .theta..sub.j, a corresponding
known field pattern may be represented by a series of local
electrical field intensities [I.sub.1j, I.sub.2j, I.sub.3j, . . . ,
I.sub.Ndj]. The electrical field intensity at a particular region
of the zone is proportional to the square of the electrical field
amplitude at that region. For all MSEs, the field patterns may be
collectively written in matrix form as:
[I.sub.11,I.sub.21,I.sub.31, . . . , I.sub.Nd1;
I.sub.12,I.sub.22,I.sub.32, . . . , I.sub.Nd2; . . .
I.sub.1Nm,I.sub.2Nm,I.sub.3Nm, . . . , I.sub.NdNm]
This matrix, referred to as the I matrix, may be determined after
the MSEs and the discretization approach are determined. If
discretization changes, the values of the I matrix may change, even
if the field patterns remain the same.
[0146] In some embodiments, the processor may be configured to
determine a weight to be applied to each of a plurality of
electromagnetic field patterns, through the control of MSEs. For
example, as shown in step 1040 of FIG. 10, the processor may
acquire the desired amount of energy to be delivered to or absorbed
in at least one region in the energy application zone, generally
referred to herein as volumetric energy transfer information W.
Such information may be predetermined, dynamically determined by
the processor for a particular goal, and/or input by a user of the
apparatus. The term "volumetric," as used herein refers to any
characteristic that could depend, for example, on more than one
spatial dimension. For example, "volumetric" may refer to a
characteristic related to a three-dimensional space, whether
physically bounded or unbounded, associated with the energy
application zone. Thus, as introduced above, volumetric energy
transfer information W may refer to a three dimensional spatial
energy distribution profile corresponding to a desired amount of
energy to be delivered or absorbed over a volumetric region of the
energy application zone.
[0147] The volumetric energy transfer information may include the
desired amount of energy to be transferred to and/or absorbed in at
least one region in the energy application zone. For example, a
user may determine to transfer energy of 100 Joules to the meat
portion of a sandwich, and 20 Joules to the bread portion of the
sandwich. In order to implement this desired energy application
pattern, the user may select a spatial location from an image of
the energy application zone, a list of different spatial locations,
or by any other means capable of specifying volumetric locations.
The user may then specify the amount of energy to be delivered to
each specified region, through any interface to the apparatus.
After the processor acquires the volumetric energy transfer
information, the processor may construct matrices based on such
information, as shown in step 1050 of FIG. 10. For example, the
processor may construct an I matrix, as discussed previously, based
on the discretization and the field patterns associated with the
MSEs. The processor may further determine another matrix based on
the I matrix and loss profile, hereinafter termed as "P matrix."
The P matrix may be constructed as follows:
P=.sigma.I,
where .sigma. is the loss profile. Because the energy absorbed in a
region depends on the field intensity and on the loss at the
region, the P matrix may represent the amount of energy absorbed in
each region when each MSE is applied. The volumetric energy
transfer information W may represent a target distribution of
absorbed energy, specifying an amount of energy is to be absorbed
by at least one region in the energy application zone as a result
of the energy transfer (application). The desired result
represented by W may be achieved by a combination of selected MSEs.
Therefore, the processor may determine a weight vector T
representing the contribution of each MSE to an energy delivery
scheme that may result in the desired energy transfer (e.g.,
volumetric energy transfer information W). Thus, the relationship
between the weights of each field pattern or corresponding MSE (T),
the energy absorption associated with each field pattern or
corresponding MSE (P) and the desired energy transfer (W) may be
expressed as W=TP. The weight may be calculated from this equation
as follows:
T=WP.sup.-1,
where P.sup.-1 represents the inversion of the P matrix. After the
matrices are constructed, the method may include a step of checking
if the matrices represent solvable equations (step 1060). If so
(1060: yes), the method may include solving the equations (step
1080), and applying energy to the energy application zone in
accordance with the solution, for example, applying energy at the
different MSEs, weighted according to the weights found by solving
the equations (step 1090). If the equations are not solvable, for
example, if a solution does not exist or is not sufficiently
stable, (step 1060: no), the method may include modifying the MSEs
that participate in the solution and/or the discretization applied
(step 1070), and control may return to step 1040 with the new MSEs
and/or discretization.
[0148] The weight T, which may be found by solving the equations,
may represent, for example, the time duration of energy
application, the power of energy application, or some other energy
application characteristic that may dictate the contribution of
each MSE to the desired result. For example, if the power to be
applied at each MSE is substantially the same, energy application
duration may be dictated by the weight. For example, if a first MSE
is assigned a weight that is twice as large as the weight of a
second MSE, the first MSE may be applied for twice the time than
the second MSE.
[0149] In another example, if the time duration of applying each
MSE is substantially the same, the weight may correspond to the
power level during each energy application period. For example, if
a first MSE is assigned a weight that is twice as large as the
weight of a second MSE, the first MSE may be applied at twice the
power than the second MSE.
[0150] In yet another example, if a first MSE is assigned a weight
that is three times as large as the weight of a second MSE, the
first MSE may be applied for twice the time and at 150% of the
power at which the second MSE is applied. Thus, the weight may
correspond to a power level. Additionally or alternatively, the
weight may correspond to a time duration.
[0151] Application of each of the MSEs at the determined weight may
be referred to herein as an energy application scheme or energy
delivery scheme.
[0152] The processor may be configured to implement the energy
delivery scheme, that is, to cause the source to supply each of the
plurality of electromagnetic field patterns to the energy
application zone at the determined weights. As discussed
previously, the processor may control the application of MSEs to
cause their corresponding field patterns to be generated in the
energy application zone. Such field patterns may contain hot and
cold spots as previously discussed. Because of the correlation
between a particular MSE and its corresponding field pattern, the
properties of the field pattern, including its hot and cold spots,
are predictable. In a particular example, the location and field
intensity of the hot and cold spots are predictable for a given
MSE. With such knowledge of the field patterns, the processor may
apply energy to an object in a controllable manner.
[0153] FIGS. 9A and 9B illustrate an example of spatially
controlled energy delivery. In FIG. 9A, an energy application zone
910 may be discretized into a set of regions, labeled from 1 to 36.
Three radiating elements 960, 962, and 964 may be placed on the
boundary of energy application zone 910. An object 920 is located
in the zone, occupying regions 8, 9, 14, and 15. Three field
patterns may be generated by applying appropriate MSEs. The first
field pattern may include a hot spot 930, located in regions 8, 9,
10, and 11 (shaded area marked by lines going from upper right to
lower left). The second field pattern may include a hot spot 940,
located in regions 14, 20, and 26 (shaded area marked by lines
going from upper left to lower right). The third field pattern may
include a hot spot 950, located in regions 15, 16, 21, and 22
(shaded area marked by crossed lines). It should be understood that
the illustration of FIG. 9A is a highly simplified representation
of an exemplary application of principles consistent with the
present invention. In practice, the discretization of the
application zone may include less or many more regions, and the
size of different regions may be different. Also, in practice, the
energy application zone may be three-dimensional. A two-dimensional
example is provided for simplicity of representation. The regions
may be of irregular shapes, and may be labeled or identified
differently. An object may be located in one or more regions, and
may also only partially occupy some regions. The field patterns may
include one or more hot spots, each of which may be located in one
or more regions, or they may be located only partially in some
regions. The hot spots of different field patterns may be
overlapped entirely or partially with each other. There may be
different number of radiating elements, and they may be located at
different locations inside, partially inside, or outside of the
energy application zone.
[0154] For simplicity, it is assumed that in FIG. 9A, the first
field pattern (including hot spot 930) is generated by applying
electromagnetic energy through radiating element 960. Likewise, the
second and third field pattern (including hot spots 940 and 950,
respectively) are generated by applying electromagnetic energy
through radiating elements 962 and 964, respectively. Therefore,
the processor may choose to generate hot spot 930 by causing the
source to supply electromagnetic energy through radiating element
960 into the energy application zone; generate hot spot 940 by
causing the source to supply electromagnetic energy through
radiating element 962; and generate hot spot 950 by causing the
source to supply electromagnetic energy through radiating element
964.
[0155] The information indicative of electromagnetic energy loss
associated with object 920 may be acquired through any available
method discussed previously. For example, as shown in FIG. 9B,
object 920 may include three parts: 922, 924, and 926. Part 922 may
be located in regions 8 and 9; part 924 may be located in region
14; and part 926 may be located in region 15. The three parts may
have different loss properties, which may be denoted by
.sigma..sub.922, .sigma..sub.924, and .sigma..sub.926,
respectively. For simplicity, it is assumed that the three parts
have the same loss property, e.g., .sigma..sub.920.
[0156] Hot spots 930, 940, and 950 may have different field
intensities. In reality, the field intensity is a function of
spatial location, and it is often non-uniform, even inside a
hot/cold spot. Indeed, due to standing wave phenomenon, the
amplitudes of the field intensity, in other words, the envelop of
the maximum field intensities, in an energy application zone often
vary from a local maxima to a local minima. Such variation often
has a sinusoidal shape. That is, the amplitudes of the field
intensity are continuously changing from one location to another.
Therefore, a hot spot may often be defined as a spatial region
where all the amplitudes of field intensity inside the region are
above a threshold, while a cold spot may be defined as a spatial
region where all the amplitudes of field intensity inside the
region are below a threshold. It should be understood that inside a
hot/cold spot, the amplitudes of field intensity at different
locations are not necessarily the same. However, for simplicity and
ease of discussion, it is assumed that in FIG. 9A, the amplitudes
of field intensities inside all three hot spots 930, 940, and 950
are the same when supplying the same power to their corresponding
excitation radiating element, and increase/decrease linearly as the
power supplied to their corresponding excitation radiating element
changes.
[0157] The present invention may make it possible to apply a
desired amount of energy to a particular part of the object within
some spatial or energy error tolerance. There are virtually an
infinite number of energy delivery schemes for specifying how much
energy to be applied to which parts of the object. For simplicity,
it is assumed that the energy delivery plan is to achieve uniform
energy delivery to object 920. In other words, the plan is to
deliver the same amount of energy to each of the regions 8, 9, 14,
and 15 of the object. To achieve this goal, the processor may first
determine the power to be supplied to each of radiating elements
960, 962, and 964. Because the assumptions are that the loss
properties of all three parts of the object 920 are the same, and
the amplitude of field intensities inside all three hot spots 930,
940, and 950 are also the same when supplying the same power to
their corresponding excitation radiating element, the processor
determines that in order to achieve uniform energy delivery, the
power supplied to the radiating elements should be the same as
well. That is, the weights to be applied to the field patterns
should be the same. The processor may then cause the source to
supply power P.sub.960 for time duration t.sub.960 to radiating
element 960 to generate the first field pattern in which
electromagnetic energy is delivered to the part 922 of the object
920 through hot spot 930. After that, the processor may supply
power P.sub.962 for time duration t.sub.962 to radiating element
962 to generate the second field pattern in which electromagnetic
energy is delivered to part 924 of the object 920 through hot spot
940. Finally, the processor may supply power P.sub.964 for time
duration t.sub.964 to radiating element 964 to generate the third
field pattern in which electromagnetic energy is delivered to the
part 926 of the object 920 through hot spot 950. In the above
process, when the power levels P.sub.960=P.sub.962=P.sub.964 and
t.sub.960=t.sub.962=t.sub.964, the amounts of energy delivered to
the locations 8, 9, 14, and 15 of the object are the same.
[0158] In another example, if the delivery plan is to deliver twice
the amount of energy to part 922 (occupying regions 8 and 9) that
is delivered equally to parts 924 and 926, the processor may double
the power level P.sub.960=2.times.P.sub.962 and keep the power
levels P.sub.962=P.sub.964. The time durations, however, remain
unchanged. Alternatively, the processor may keep all the power
levels unchanged and prolong the energy supplying duration to be
t.sub.960=2.times.t.sub.962=2.times.t.sub.964. Still alternatively,
the processor may control the radiating elements such that
P.sub.960=1.5P.sub.962=1.5P.sub.964 and
t.sub.960=1.333t.sub.962=0.333t.sub.964 Any other way may also be
used to ascertain that the amount of energy delivered to part 922
is twice the amounts of energy delivered to parts 924 and 926, and
the amounts of energy delivered to parts 924 and 926 are the
same.
[0159] In some embodiments, the discretization of the energy
application zone may be different from the one shown in FIGS. 9A
and 9B. For example, object 920 may be discretized into a plurality
of regions (e.g., three), where regions 8 and 9 shown in FIG. 9B
may be united as a single region. In this case, part 922, which has
the same loss properties across original regions 8 and 9, may
occupy a single region (8+9).
[0160] In some embodiments, hot spots in the energy application
zone may overlap with one another. For example, hot spots 930 and
940 in FIG. 9A may overlap with each other in region 8. In this
case, the energy delivery control strategy may be different. For
example, such a distribution of hot spots may be particularly
suitable for delivering more energy to region 8, because region 8
may receive energy deposition when both hot spots 930 and 940 are
applied. Alternatively or additionally, such hot spots may be used
to compensate the field intensity non-uniformity within each hot
spot. For example, region 8 in hot spot 930 may have a lower
amplitude of field intensity than that in region 9. Similarly,
region 8 in hot spot 940 may also have a lower amplitude of field
intensity than that in region 14. Therefore, by applying additional
energy in region 8 during application of 930 and 940, such
non-uniformity in the amplitude of field intensity in hot spots 930
and 940 may be compensated and uniform energy delivery may be
achieved in object 920. Based on similar principles, a target
non-uniform heating pattern may be obtained.
[0161] In some embodiments, the acquired information, e.g., loss
profile, may be predetermined based on known characteristics of the
object. For example, in the case of a dedicated oven that
repetitively heats products sharing the same physical
characteristics (e.g., identical hamburger patties), the processor
may be pre-programmed with the energy absorption parameters of the
object. In another example, an oven may be configured to heat
several different, but predetermined objects, each of different
absorption characteristics (for example, various food items
distributed by a certain distributor) and the processor may be
programmed to load the energy absorption parameters of the object
from a database. In some embodiments, the database may be internal
to the apparatus, for example, to the processor. In some
embodiments, the database may be external, for example, on the
Internet, and the processor may be configured to download the
information from the external database.
[0162] In some embodiments, the acquired information may be based
on feedback from the object. For example, various measurement
methods may be employed to determine the information indicative of
electromagnetic energy loss associated with the object. One
particular exemplary method may include measuring the reflected
energy from the object by applying electromagnetic energy to the
object, e.g., by measuring energy reflected to the transmitting
radiating element, and/or by measuring energy transmitted from the
transmitting radiating element to other detectors, for example, to
other receiving radiating element(s). Based on the feedback
information of the reflected energy, the information indicative of
electromagnetic energy loss associated with the object may be
determined.
[0163] The processor may be configured to generate the loss profile
based on feedback from the object. For example, when the loss
profile is not available in advance or the prior acquired loss
profile needs to be refined or re-determined, the processor may be
configured to generate the loss profile through a series of steps.
In a particular example, the processor may be configured to cause
the source to apply electromagnetic energy to the object and
measure the reflected energy from the object. Based on the feedback
information of the reflected energy, the information indicative of
electromagnetic energy loss associated with the object may be
determined. In another example, one or more predetermined
indicators associated with loss profiles may be stored in advance,
and the processor may cause the source to apply electromagnetic
energy to the object and detect feedback electromagnetic energy
from the object. Based on such feedback information, the processor
may generate a loss profile from the one or more predetermined
indicators associated with loss profiles.
[0164] In some embodiments, the weight to be applied to each of a
plurality of electromagnetic field patterns may be determined based
on the acquired information. For example, as illustrated in FIGS.
9A and 9B, when the loss properties of parts 922, 924, and 926 are
different, in order to achieve a given energy delivery plan, the
weight to be applied needs to be adjusted accordingly. For example,
if part 922 has a loss property
.sigma..sub.922=2.times..sigma..sub.924=2.times..sigma..sub.926,
using hot spot 930 to deliver energy to part 922 may be more
efficient than using hot spots 940 and 950 to deliver energy to
parts 924 and 926, respectively, when the amplitudes of field
intensity of all hot spots are the same. Therefore, the weight for
applying the first field pattern to generate hot spot 930 needs to
be reduced compared to the case where the loss properties of all
parts of object 920 are the same, for a given energy delivery plan.
The processor may be configured to determine the weight to be
applied to each of a plurality of electromagnetic energy patterns
based on a predetermined energy distribution in the energy
application zone. For example, in FIG. 9A, predetermined energy
distributions, including three field patterns having different hot
spots, are used to determine the weight. If the amplitudes of field
intensity for different hot spots are different, the weight needs
to be adjusted accordingly. For example, if hot spot 930 has a
higher amplitude of field intensity than those of hot spots 940 and
950, the power level supplied to radiating element 960 may be
reduced and/or the time duration for supplying power may be
shortened. In this example, hot spot 930 has a higher power density
than hot spots 940 and 950 and, therefore, hot spot 930 is capable
of applying more energy to part 922, assuming all other conditions
are equal. When determining the weight, such differences may be
considered. In some applications, solving the equation provided
above for T may be a useful route to find the appropriate weights
that may result in a target field delivery scheme (e.g., to obtain
the volumetric energy transfer information).
[0165] The processor may be configured to take into account
thermodynamic characteristics of the object. For example, during
the energy delivery process, the temperatures of different parts of
the object may be different. This may be an intentional result
according to a particular energy delivery plan, or may be, for
example, due to the fact that energy may be delivered to different
parts of the object at different times, or may be due to the
non-uniform nature of the filed intensity inside a hot/cold spot.
In any case, when there is a temperature difference, thermal energy
may diffuse from higher temperature regions to lower temperature
regions. As a result, the amount of energy initially delivered to a
given region may be lost in that region and gained in another
region due to thermal diffusion. Additionally, the heat capacity
properties of different objects, or among different parts of a
given object, may be different. The heat capacity, also known as
specific heat, is a measure of heat or thermal energy required to
increase the temperature of a unit quantity of a substance by one
temperature unit, and may be measured, for instance by calorie per
gram per .degree. C. Therefore, when the heat capacities of two
objects, or two parts of an object, are different (assuming they
have the same mass), the temperature rises of these two objects or
parts may be different even if the same amount of energy is applied
to them. Therefore, thermodynamic characteristics of the object,
such as heat conduction, heat capacity, and a specific mass of at
least a portion of the object may be taken into consideration
during the energy delivery process.
[0166] As noted above, the apparatus may include multiple radiating
elements, and the processor may be configured to employ a subset of
the multiple radiating elements in order to achieve a predetermined
field pattern. For example, in FIG. 9A, multiple radiating elements
are employed, and each of them corresponds to a predetermined field
pattern. In this example, the processor may be configured to select
a subset of the three radiating elements in order to achieve a
desired field pattern.
[0167] In some embodiments, radiating elements may be selected for
exciting a certain mode in accordance with the positioning of the
radiating elements in the energy application zone. The position of
the radiating element may be selected to effectively excite a
desired mode and/or to reject an undesired mode. This and other
optional features of some embodiments are explained below in
reference to FIGS. 12A, 12B, 12C, 13A, and 13B.
[0168] The concept of rejecting modes may be illustrated by FIGS.
12A and 12B, which show X-Y cross sections of two modes 1802 and
1806 excitable in cavity 1800. Mode 1802 is a TM.sub.11 mode and
mode 1806 is a TM.sub.21 mode. Mode TM.sub.11 may be excitable at
every frequency that is equal to or greater than a lower cutoff
frequency f.sub.11 and TM.sub.21 may be excitable at every
frequency that is equal to or greater than a higher cutoff
frequency f.sub.21. Thus, at intermediate frequencies between
f.sub.11 and f.sub.21, TM.sub.11 may be excited without exciting
TM.sub.21, but there is no frequency at which TM.sub.21 is
excitable and TM.sub.11 is not. Therefore, if one desires exciting
TM.sub.11 at a frequency higher than f.sub.2i without exciting
TM.sub.21, TM.sub.21 may have to be rejected. In the present
discussion, rejecting a mode may refer to preventing or
substantially decreasing the excitation of the mode.
[0169] In some embodiments, a desired mode may be excited and an
undesired mode may be simultaneously rejected by selecting for the
excitation a radiating element positioned at or near a null of the
undesired mode, and at or near a maximum of the desired mode. A
null of a mode is any location in the energy application zone where
the field intensity of the mode is permanently (or in all phases)
zero, and a maximum of a mode is any location where the field
intensity of the mode reaches an overall maximal value at all
phases (or at every instant). A radiating element positioned at the
null of a mode does not excite the mode (regardless of the
frequency applied), and a radiating element positioned near the
null may excite the mode only to a small degree. For example, in
FIG. 12B line 1803 is a collection of null points of mode
TM.sub.21; thus, a radiating element positioned at any point along
this line may not excite mode TM.sub.21, even at frequencies higher
than f.sub.2i. However, since point 1809 (which is along line 1803)
is not at a null of mode TM.sub.11 (1802), mode 1802 may be excited
by a radiating element positioned at point 1809. It is noted that
line 1803 is actually a plane, going all along the cavity.
Similarly, point 1809 is a line, going all along the cavity, from
the upper to the lower base, perpendicularly to the bases. In
practice, the radiating element may be positioned anywhere on plane
1803 without exciting mode 1806. In some embodiments, however, the
radiating elements may be positioned at the upper (and/or lower)
base of the cavity, at a position in the XY plane.
[0170] Another way to reject a mode may include using two or more
radiating elements, positioned at two or more locations where the
magnitude of the electric field of the mode to be rejected is of
opposite signs. For example, FIG. 13A depicts the (normalized)
magnitude of the electric field of mode 1806 along line 1805. As
shown in the figure, at x=0.5 (which is a point on line 1803), the
field is zero, at x=0.25 the field is +1 and at x=0.75 the field is
-1. Thus, in some embodiments, two radiating elements, one at
x=0.25 and the other at x=0.75 (or at any other two points where
the field has opposite signs and equal magnitudes) may be selected
to radiate RF waves at the same amplitude and phase, to cancel each
other, and thus reject an undesired mode. If the fields at the
locations of the two radiating elements have opposite signs and
different absolute values, they may still be used for rejecting the
undesired mode, if, for instance, their amplitudes are tuned such
that sum of the products of field and amplitude at each radiating
element location is zero. It is noted that while the above
discussion is focused on different points along the X axis, similar
considerations may be applied also for points having different y
values and/or z values.
[0171] In some embodiments, a desired mode may be excited by
emitting energy via two antennas that are oriented anti parallel to
each other, or that are oriented parallel to each other but emit
waves at a phase shift of 180.degree. between each other, and
located at points where the field pattern has opposite sign.
Similarly, in some embodiments, modes may be rejected by emitting
energy via two antennas that are oriented anti parallel to each
other, or that are oriented parallel to each other but emit waves
at a phase shift of 180.degree. between each other, and located at
points where the field pattern has the same sign.
[0172] FIG. 13B depicts the (normalized) magnitude of the electric
field of mode 1802 along line 1805. As shown in the figure, at
x=0.5, the field is maximal, and the field at x=0.25 is equal (both
in magnitude and in sign) to the field at x=0.75. Thus, two
antennas, one at x=0.25 and the other at x=0.75 that emit at the
same amplitude and phase may tend to excite mode 1802. However, two
antennas that are oriented anti parallel to each other, or that are
oriented parallel to each other but with a phase shift of
180.degree. between each other, may reject mode 1802. Consequently,
the latter combination of antennas and phases may excite mode
TM.sub.21 and rejects mode TM.sub.11.
[0173] In some embodiments, a desired and/or an undesired mode is a
resonant mode. A resonant mode may be excited when the frequency f
of the electromagnetic wave corresponds to the dimensions of the
energy application zone in a manner known in the art. For example,
in an energy application zone that is a rectangular cavity, a
resonant mode may be excited when the dimension, along which the
electromagnetic wave propagates, referred to herein as h.sub.z, is
equal to N*(.lamda./2), where N is a whole number (e.g. 0, 1, 2, 3)
and .lamda. is the wavelength, given by the equation .lamda.=c/f,
where c is the light velocity in the cavity. A resonant mode is
usually marked with three index numbers, where the third index
number is N.
[0174] When a single resonant mode is excited at a given frequency,
a great majority of the power carried with the excitation may be
carried by the resonant mode, and other modes, which may be
propagating or evanescent, may carry a smaller portion of the
power, which may be negligible. Thus, when a single resonant mode
is excited, there may be little or no need to reject non-resonating
modes.
[0175] For example, when h.sub.z=c/f.sub.21 (i.e. when N=2) the
antennas and frequency may be selected to excite mode TM.sub.21
there may be little need to reject, for example, mode TM.sub.11,
because, although mode TM.sub.11 may be excitable at the applied
frequency, it may carry only a small amount of the power, in
comparison to the amount of power carried by the resonant mode
TE.sub.212.
[0176] Thus, in some embodiments, resonant modes may be used for
achieving a target field intensity distribution. This may
facilitate control over the excited modes, provided sufficient
bandwidth and frequency control.
[0177] In some embodiments, mode excitation may be further
facilitated, (e.g., by easing the requirements from bandwidth and
frequency control), by using a degenerate cavity. A degenerate
cavity is one in which at least one cut off frequency is a cut off
frequency of two or more modes of the same family (e.g., two TE
modes). Similarly, each resonant frequency (except for, sometimes,
the lowest one) may excite two or more resonant modes of the same
family. Some shapes of degenerate cavities may include, for
example, cylinder and sphere.
[0178] In some embodiments, one desired resonant mode and one or
more undesired resonant modes may be excited at a same frequency,
and the non-desired modes may be rejected as described above.
[0179] For example, the same frequency that excites mode
TM.sub.212, a cross section of which is shown as 1806 in FIG. 12B
may excite also mode TM.sub.212, a cross section of which is
illustrated as 1808 in FIG. 12C. However, if the excitation is via
a radiating element positioned at a null of mode 1808, which is not
a null of mode 1806, only mode 1808 may be excited. For example, if
the radiating element radiates at frequency f.sub.12=f.sub.21 at
point 1809, shown in FIGS. 12B and 12C, only mode 1808 may be
excited.
[0180] Thus, in accordance with some embodiments of the invention,
there is provided an apparatus for exciting multiple modes (e.g. 3,
4, 5, 6, 7, or higher number), and controlling which of the modes
is effectively excited at each given instance. The apparatus may
include a processor, configured to determine which of the multiple
modes is to be effectively excited at some instance and at which
weight; and may select excitation scheme that may effectively
excite only the determined mode. The excitation scheme may include,
for example, identity of radiating elements to participate in the
excitation (and optionally shortcutting non-selected radiating
elements), setting the phase difference between two or more the
selected radiating elements, and setting amplitude differences
between them, such that the predetermined mode may be effectively
excited, and other modes may be rejected. In some embodiments, the
processor may be configured to determine the modes to be excited so
as to excite a target field intensity distribution in the energy
application zone, considering a given loss profile of the energy
application zone or a portion thereof. The given loss profile may
be acquired by the processor.
[0181] FIG. 11 is a simplified block diagram of a processor 630
configured to apply electromagnetic energy in accordance with some
embodiments of the invention. Processor 630 may be the same as, may
include, or may be part of processor 30. Additionally or
alternatively, processor 630 may be in addition to processor
30.
[0182] Processor 630 is shown to include storage 632 (which also
may be referred as memory), for storing data, and several
processing modules for processing data, for example, data stored on
storage 632. Storage 632 may be continuous, segmented, or may have
any other configuration as known in the art of storing data
electronically. Storage 632 may also be separate from processor
630, for example, on a disk. The modules may be implemented using
hardware and/or software and may include, for example, software
routines. In some embodiments, two or more of the modules shown in
the figure may be united to a single module, which performs the
tasks of the two modules shown, or may be spread between several
modules.
[0183] Optionally, processor 630 may be connected to an interface
610, for receiving data via the interface. For example, field
patterns that may be obtained with different MSEs may be received
from the interface, and stored on storage 632, for example, in
dedicated storage space 634. Storage space 634 may also store the
MSEs, such that each stored MSE may be associated with a stored
field pattern, predicted to be excited in the energy application
zone when energy is applied to the zone at that MSE. Optionally,
the field patterns associated with the MSEs may be obtained with
empty energy application zone, and/or the energy application zone
may have a standard load in it (for example, a piece of meat at the
center of the zone, a toast at one side of the zone and salad on
another side, etc). Optionally, the standard load may be similar to
typical loads known to be used in the energy application zone (for
example one or more foods that are usually cooked in the oven, or
that the oven is expected to cook often).
[0184] Additionally or alternatively, a target field intensity
distribution (e.g., a volumetric energy transfer information) may
be received via the interface. Such target field intensity
distribution may be stored on storage 632, for example, in
dedicated storage space 635.
[0185] In some embodiments, storage 632 may also have storage space
636, for storing a loss profile or other information indicative of
RF energy loss associated with at least a portion of the energy
application zone or the object. For example, storage space 636 may
store a loss profile of the energy application zone obtained in a
preceding loss profile reconstruction cycle. Additionally or
alternatively, storage space 636 may store a predicted loss
profile. The prediction may be obtained based on knowledge of the
object in the energy application zone, its composition, location,
orientation, temperature, and/or any other parameter that may
affect the loss profile. The stored loss profile may be sent to
storage space 636, for example, from interface 610, from another
interface (not shown), or from an equation solving module 648
described below. For example, the stored loss profile may be
calculated or otherwise predicted by another apparatus and/or at an
earlier date, and sent to storage space 636 via interface 610.
[0186] Optionally, storage 632 may also have a storing space 638
for storing energy distributions and/or field intensity
distributions obtained in the energy application zone during energy
application.
[0187] Processor 630 is shown to include an MSE determination
module 642. Module 642 may be configured (optionally, by running a
suitable software) to determine which of the available MSEs are to
be used at any stage of operation, e.g., during an energy
application process. In some embodiments, all the available MSEs
may be used by default, and MSE determination module 642 may be
omitted. In other embodiments, module 642 may determine MSEs to be
used, for example, based on the predicted loss profile and/or based
on the target field intensity distribution. For this, module 642
may be allowed to retrieve predicted loss profile data and/or data
concerning a target field intensity distribution stored on storage
space 636 and/or 635. Alternatively or additionally, module 642 may
select MSEs that are relatively easier to excite and/or control,
and may select other MSEs only if, for example, the easily excited
MSEs do not provide satisfactory results.
[0188] Optionally, module 642 is connected to control module 660,
which may control source 650 of electromagnetic energy to excite
the selected MSEs. Control module may control source 650 to excite
the selected MSEs at the respective weights (which may be
determined by equation solving module 648 as described below). A
power supply, a modulator, an amplifier, and/or radiating
element(s) (or portions thereof), for example power supply 12,
modulator 14, amplifier 16, and radiating element 18 illustrated in
FIG. 1, may be parts of source 650. In some embodiments, the energy
distribution obtained in the energy application zone as a result of
the excitation may be measured. The measurements may be carried out
by one or more detectors, shown collectively as 640. One or more of
detectors 640 may be a part of source 650, and the others, if any,
may be separate and/or independent from source 650. It is noted
that in FIG. 11 source 650 and detector 640 are shown at two sides
of processor 630, although in practice they may be embodied in the
same parts, for example, the same antennas may be used for
supplying energy to the energy application zone and for measuring
excited field patterns, even if not necessarily at the same time.
The results of the measurements may be stored on storage space
638.
[0189] Processor 630 is also shown to include a discretization
module 644, configured to divide the energy application zone to
regions, for example, as depicted in FIG. 7A, 7B, or 7C.
Optionally, discretization module 644 may divide the energy
application zone in accordance with a loss profile stored in
storage space 636. For example, module 644 may divide the zone more
densely where more abrupt loss changes are present in the predicted
loss profile.
[0190] Additionally or alternatively, discretization module 644 may
divide the energy application zone in accordance with a target
field intensity distribution stored in storage space 635. For
example, module 644 may divide the zone more densely where more
abrupt field intensity changes are present in the target field
intensity distribution.
[0191] In some embodiments, the predicted loss profile and/or the
target field intensity distribution may be provided in accordance
with a given discretization, for example, as a matrix of values,
each associated with one portion of the energy application
zone.
[0192] Module 644 may then discretize the energy application zone
in accordance with the discretization by which the predicted
profile and/or target distribution are provided. For this, module
644 may be allowed to retrieve data from storage spaces 635 and/or
636, saving the predicted profile and the target distribution. For
example, module 644 may divide the energy application zone such
that volumes characterized by similar losses will be included in a
single region. Additionally or alternatively, module 644 may divide
the energy application zone such that volumes wherein similar field
intensity is desired will be included in a single region.
Discretization module 644 may also divide the energy application
zone in accordance with a predetermined discretization scheme, for
example, a default discretization scheme. One possible default
discretization scheme is illustrated in FIG. 7A.
[0193] Processor 630 is also shown to include equation constructing
module 646, configured to construct equations according to, for
example, the equation T=WP.sup.-1, discussed above, in order to
obtain the target field intensity distribution. For this, module
646 may define the field intensity of each of the MSEs which may be
selected by module 642, in each region to which the energy
application zone is divided by module 644, and may take into
account measurement results stored at storage space 638, loss
values associated with the regions, and target field intensity
associated with each of the regions.
[0194] Once the equations are constructed by module 646, equation
solving module 648 may solve the equations, for example, by linear
programming or any other means known in the art for solving linear
equations. Equation solving module 648 may solve the equations in
order to obtain the respective weights of each MSEs or field
pattern. If equation solving module 648 determines that the
equations are not solvable or that the solution is not
satisfactory, for example is not sufficiently stable, module 648
may trigger module 642 and/or module 644 to amend the selected MSEs
and/or the discretization.
[0195] If the equations are solved, the obtained weights may be
saved, for example, at storage 635, for guiding energy application
to the energy application zone at the present operation stage, or
at as input for the equation solving module in a later stage.
[0196] The correlation between field pattern and amount of energy
applied may be determined by the energy absorption profile of the
object at issue. That is, once an object's ability to absorb energy
throughout its volume is determined, then energy can be applied to
the object in a controlled manner in order to achieve a desired
goal. For example, if the goal is to uniformly apply energy across
an object's volume, then the processor might select combinations of
MSEs that result in uniform energy application. If on the other
hand, non-uniform energy application is desired, then the processor
might apply predetermined amounts of energy using selected field
patterns in order to achieve the desired non-uniformity.
[0197] A coordinate system may be established to represent the
spatial locations of hot/cold spots. As discussed earlier, each MSE
may result in a predictable field pattern with predictable hot/cold
spots. Based on these principles, the processor may discretize the
energy application zone or portion thereof by causing the processor
to be preprogrammed with the coordinates of each hot/cold spot in
each field pattern corresponding to each MSE.
[0198] With information relating to the spatial locations of hot
and cold spots within the energy application zone, the processor
may determine information about an object within the zone,
including, for example, the shape and/or the position of the
object. During operation, when the processor receives an indication
that the detector has received feedback indicative of energy
absorption during a particular MSE condition, the processor may be
configured to recognize that an object may be located in one or
more of the hotspots corresponding to that MSE condition. Based on
the feedback information available, the processor may determine
whether an object is located in some combination of hot and cold
spots associated with an MSE condition. The more MSEs that are
tested for feedback, the more information the processor can use to
learn about the location and the absorptive properties of the
object in the energy application zone. Over a series of such
measurements with differing MSEs, the processor may continually
refine a feedback-derived location of the object in the zone. Using
this feedback, the processor may be able to determine the
absorptive properties of discrete regions within the object as well
as the spatial locations of those regions within the object.
[0199] In some exemplary embodiments, the processor may regulate
the source to apply energy repetitively to the energy application
zone. For example, the processor may apply an MSE and cause its
corresponding field pattern in the energy application zone for a
predetermined time period, then apply another MSE and cause another
field pattern in the energy application for another predetermined
time period. Such energy application duration and/or energy
application rate may vary. For example, in some embodiments, energy
may be applied to the energy application zone 120 times per second.
Higher (e.g. 200/second, 300/second) or lower (e.g., 100/second,
20/second, 2/second, 1/second, 30/minute) rates may be used, as
well as uneven energy application rates.
[0200] In some embodiments, a set of MSEs may be applied
sequentially during a period of time (herein referred to as "a
sweep"). And the sweep may also be repeated at a predetermined rate
or after a predetermined interval. At times, a sweep sequence
(e.g., one or more sweeps) may be performed once every 0.5 seconds
or once every 5 seconds or at any other rate, such as higher, lower
or intermediate. It is to be understood that the MSE selection in
different scans may or may not the same.
[0201] In some embodiments, the processor may control the
performance of one or more sweeps in order to acquire information
on the loss profile, and then perform one or more sweeps to process
(e.g. heat) the object based on the acquired loss profile. In some
embodiments, the loss profile may change during heating, and
sequences of loss-profile acquisition and heating sweeps may be
repeated. Optionally, a loss profile acquisition sweep may use
lower energy (or power) levels than a heating sweep.
[0202] After a given amount of energy (e.g., 10 kJ or less or 1 kJ
or less or several hundreds of joules or even 100 J or less were
applied or dissipated into the object or into a given portion of
the object (e.g., by weight such as 100 g or by percentage, such as
50% of load)), a new scan may be performed.
[0203] In exemplary embodiments of the invention, the rate of
energy application or the rate of scan (for example, the duration
of energy application at each MSE within a scan, the total duration
of each scan, energy application interventions between scans, etc)
may depend on the rate of change in spectral information between
energy applications or between scans. For example, a threshold of
change in dissipation and/or frequencies (e.g., a 10% change in sum
integral) may be provided or different change rates associated with
different energy application/scan rates, for example using a table.
In another example, what is determined is the rate of change
between energy applications/scans (e.g., if the average change
between energy applications/scans is less than the change between
the last two energy applications/scans). Such changes may be used
to adjust the period between energy applications/scans once or more
than once during energy application process. Optionally or
alternatively, changes in the system (e.g., movement of the object
or structure for hold the object) may affect the energy
applications/scans rate (typically major changes increase the rate
and minor or no changes decrease it).
[0204] Various examples of the invention are described herein in
connection with spatially controlled energy delivery. Persons of
ordinary skill in the art will appreciate that core, inventive
principles of energy application discussed herein may be applied
across various forms of energy application zones, and for a variety
of purposes other than or including heating. In many respects, it
is these broader principles that are the subject of the appended
claims.
[0205] In the foregoing Description of Exemplary Embodiments,
various features are grouped together in a single embodiment for
purposes of streamlining the disclosure. This method of disclosure
is not to be interpreted as reflecting an intention that the
claimed invention requires more features than are expressly recited
in each claim. Rather, as the following claims reflect, inventive
aspects lie in less than all features of a single foregoing
disclosed embodiment. Thus, the following claims are hereby
incorporated into this Description of the Exemplary Embodiments,
with each claim standing on its own as a separate embodiment of the
invention.
[0206] Moreover, it will be apparent to those skilled in the art
from consideration of the specification and practice of the present
disclosure that various modifications and variations can be made to
the disclosed systems and methods without departing from the scope
of the invention, as claimed. Thus, it is intended that the
specification and examples be considered as exemplary only, with a
true scope of the present disclosure being indicated by the
following claims and their equivalents.
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