U.S. patent application number 13/696020 was filed with the patent office on 2013-02-28 for antenna placement in degenerate modal cavities of an electromagnetic energy transfer system.
The applicant listed for this patent is Yoel Biberman, Denis Dikarov, Pinchas Einziger, Arnit Rappel, Michael Sigalov. Invention is credited to Yoel Biberman, Denis Dikarov, Pinchas Einziger, Arnit Rappel, Michael Sigalov.
Application Number | 20130048880 13/696020 |
Document ID | / |
Family ID | 44318163 |
Filed Date | 2013-02-28 |
United States Patent
Application |
20130048880 |
Kind Code |
A1 |
Einziger; Pinchas ; et
al. |
February 28, 2013 |
ANTENNA PLACEMENT IN DEGENERATE MODAL CAVITIES OF AN
ELECTROMAGNETIC ENERGY TRANSFER SYSTEM
Abstract
Antenna placement in degenerate modal cavities of an
electromagnetic energy transfer system, an apparatus and method for
applying electromagnetic energy to an object are disclosed in a
degenerate energy application zone via a source of electromagnetic
energy. The apparatus may include at least one processor configured
to regulate the source to apply electromagnetic energy at a
predetermined frequency that excites a plurality of resonant modes
in the degenerate energy application zone. The plurality of
resonant modes are of the same transverse type.
Inventors: |
Einziger; Pinchas; (Haifa,
IL) ; Rappel; Arnit; (Ofra, IL) ; Dikarov;
Denis; (Hod Hasharon, IL) ; Sigalov; Michael;
(Beer-Sheva, IL) ; Biberman; Yoel; (Haifa,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Einziger; Pinchas
Rappel; Arnit
Dikarov; Denis
Sigalov; Michael
Biberman; Yoel |
Haifa
Ofra
Hod Hasharon
Beer-Sheva
Haifa |
|
IL
IL
IL
IL
IL |
|
|
Family ID: |
44318163 |
Appl. No.: |
13/696020 |
Filed: |
May 3, 2011 |
PCT Filed: |
May 3, 2011 |
PCT NO: |
PCT/IB11/01377 |
371 Date: |
November 2, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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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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61282986 |
May 3, 2010 |
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61282985 |
May 3, 2010 |
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61282984 |
May 3, 2010 |
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Current U.S.
Class: |
250/492.1 |
Current CPC
Class: |
H05B 6/686 20130101;
H05B 6/72 20130101; B01J 2219/1206 20130101; H05B 6/6447 20130101;
H05B 6/70 20130101; H05B 6/64 20130101; H05B 6/705 20130101; F26B
3/347 20130101; B01J 19/126 20130101; H05B 6/68 20130101; B01J
2219/0871 20130101; B01J 19/129 20130101; Y02B 40/00 20130101; B01J
2219/1203 20130101 |
Class at
Publication: |
250/492.1 |
International
Class: |
G21K 5/00 20060101
G21K005/00 |
Claims
1.-42. (canceled)
43. An apparatus for applying electromagnetic energy to an object
in a degenerate energy application zone via at least one source of
electromagnetic energy, the apparatus comprising: at least one
processor configured to: determine a weight to be associated with
at least one resonant mode in the degenerate energy application
zone, among a plurality of resonant modes within a mode family,
wherein the weight is associated with an amount of energy to be
used to excite the resonant mode, and regulate the at least one
source to apply electromagnetic energy based on the determined
weight.
44. The apparatus of claim 43, wherein the at least one processor
is further configured to determine the weight to be associated with
the at least one resonant mode based on feedback received from the
degenerate energy application zone having the object therein.
45. The apparatus of claim 43, wherein the weight is associated
with a power level of the electromagnetic energy for exciting the
resonant mode.
46. The apparatus of claim 43, wherein the weight is associated
with a time duration over which the electromagnetic energy is
applied for exciting the resonant mode.
47. The apparatus of claim 43, wherein the at least one processor
is further configured to regulate the at least one source to
control a phase difference between two electromagnetic waves at a
same frequency to excite a desired resonant mode in the degenerate
energy application zone.
48. The apparatus of claim 47, wherein the at least one processor
is further configured to change weights associated with at least
two resonant modes, to cause an angular shift of a field pattern
excited by the two electromagnetic waves,
49. The apparatus of claim 48, wherein the at least two resonant
modes are orthogonal to each other.
50. The apparatus of claim 43, wherein the at least one processor
is further configured to change weights associated with at least
two resonant modes, to cause an angular shift of a field pattern
excited in the electromagnetic energy application.
51. The apparatus of claim 50, wherein the at least two resonant
modes are orthogonal to each other.
52. The apparatus of claim 50, wherein the at least one processor
is configured to change the weights of the at least two resonant
modes to rotate the excited field pattern,
53. The apparatus of claim 50, wherein the at least one processor
is configured to change the weights dynamically.
54. The apparatus of claim 43, wherein the at least one processor
is further configured to determine the weight to be associated with
the at least one resonant mode such that differing amounts of
electromagnetic energy are applied to differing predetermined
regions in the degenerate energy application zone.
55. The apparatus of claim 43, wherein the at least one processor
is configured to: select at least two radiating elements from a
plurality of radiating elements; and control electromagnetic energy
application to the selected radiating elements such that at least
one desired resonant mode is excited.
56. The apparatus of claim 55, wherein the at least one processor
is configured to; select the at least two radiating elements from
the plurality of radiating elements such that at least one resonant
mode is rejected.
57. The apparatus of claim 43, wherein the plurality of resonant
modes within the mode family are of a same transverse type.
58. The apparatus of claim 43, wherein the degenerate energy
application zone includes at least one of a circular cross-section
or a square cross-section.
59. The apparatus of claim 43, further comprising at least two
radiating elements, wherein the at least two radiating elements are
positioned to reject at least one resonant mode.
60. The apparatus of claim 59, wherein the at least one processor
is configured to: select at least two radiating elements from a
plurality of radiating elements; and control electromagnetic energy
application to the selected radiating elements such that at least
one desired resonant mode is excited and at least one other
resonant mode is rejected.
61. The apparatus of claim 43, further comprising at least two
radiating elements, wherein the at least two radiating elements are
positioned to excite at least one resonant mode.
62. The apparatus of claim 61, wherein the at least one processor
is configured to: select at least two radiating elements from a
plurality of radiating elements; and control electromagnetic energy
application to the selected radiating elements such that at least
one desired resonant mode is excited and at least one other
resonant mode is rejected.
63. The apparatus of claim 43, further comprising a plurality of
radiating elements, wherein the at least one processor is
configured to control at least one of location, orientation, or
polarization of at least one radiating element from the plurality
of radiating elements.
64. A method of applying electromagnetic energy to an object in a
degenerate energy application zone, the method comprising:
determining a weight to be associated with at least one resonant
mode in the degenerate energy application zone, among a plurality
of resonant modes within a mode family, wherein the weight is
associated with an amount of energy to be used to excite the
resonant mode; and applying electromagnetic energy based on the
determined weight.
65. The method of claim 64, further comprising; receiving feedback
from the degenerate energy application zone having the object
therein; and determining the weight to be associated with the at
least one resonant mode based on the received feedback.
66. The method of claim 64, wherein the applying includes
controlling a phase difference between two electromagnetic waves at
a same frequency to excite a desired resonant mode in the
degenerate energy application zone,
67. The method of claim 66, further comprising changing weights
associated with at least two resonant modes, to cause an angular
shift of a field pattern excited by the two electromagnetic
waves.
68. The method of claim 64, wherein the weight is associated with a
time duration over which the electromagnetic energy is applied for
exciting the resonant mode.
69. The method of claim 64, further including determining the
weight to be associated with the at least one resonant mode such
that differing amounts of electromagnetic energy are applied to
differing predetermined regions in the degenerate energy
application zone.
70. The method of claim 64, further including controlling at least
one of location, orientation, or polarization of at least one
radiating element from a plurality of radiating elements located in
the degenerate energy application zone.
71. An apparatus for applying electromagnetic energy to an object
in a degenerate energy application zone, comprising: at least one
source of electromagnetic energy; a degenerate energy application
zone; and at least one processor configured to: determine weights
to be associated with a plurality of resonant modes in the
degenerate energy application zone; and regulate an application of
electromagnetic energy, at predetermined frequencies, to excite the
plurality of resonant modes based on the determined weights;
wherein at least some of the plurality of resonant modes fall
within a common mode family.
Description
[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] The present invention relates to apparatuses and methods for
applying electromagnetic energy to objects.
BACKGROUND
[0003] Electromagnetic waves are commonly used to apply energy to
various types of objects. One example of an electromagnetic
wave-generating device is a microwave oven. 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 phenomenon known as "standing waves." A standing wave is
characterized by local electrical field peaks and valleys where the
absolute values of the electrical field intensity are the greatest,
and zeroes where the absolute values are the smallest. The absolute
value of an electrical field intensity may be referred to as the
magnitude of the field. As the field intensity varies over the
length of a standing wave, so too does its heating capacity.
[0004] Conventional microwave ovens typically use a microwave
source (e.g., a magnetron) to generate microwaves at a single
frequency (e.g., 2.45 GHz). Accordingly, a single field
distribution may be formed in the conventional microwave ovens.
Therefore, if a portion of an object is covered by areas with low
field magnitudes, it may be difficult to heat that portion no
matter how much power is used for heating. One way to reduce hot
spots and cold spots in a microwave oven is to cause various field
distributions in the oven, such that the combination of these field
distributions may include less hot or cold spots. An electrical
field distribution (e.g., the locations of the peaks, valleys and
zeros of the standing waves) in the oven is determined by the
frequency of the electromagnetic energy applied. Therefore, some
conventional microwave ovens attempt to introduce variations in the
field distribution in the microwave ovens, for example, by
generating microwaves at multiple frequencies.
SUMMARY
[0005] Some exemplary aspects of the invention may be directed to
an apparatus for applying electromagnetic energy to an object in a
degenerated energy application zone via at least one source of
electromagnetic energy. The apparatus may include at least one
processor. The at least one processor may be configured to
determine a weight of at least one resonant mode, among a plurality
of resonant modes sharing a mode family and regulate
electromagnetic energy application in the at least one resonant
mode according to the determined weight.
[0006] Another exemplary aspect of the invention may be directed to
a method of applying electromagnetic energy to an object in an
energy application zone. The method may include determining a
weight of at least one resonant mode, among a plurality of resonant
modes sharing a mode family; and regulating electromagnetic energy
application in the at least one resonant mode according to the
determined weight.
[0007] Another exemplary aspect of the invention may be directed to
an apparatus for applying electromagnetic energy to an object. The
apparatus may include at least one source of electromagnetic
energy. The apparatus may further include an energy application
zone. In addition, the apparatus may include at least one
processor. The processor may be configured to determine a weight of
at least one resonant mode and regulate an application of
electromagnetic energy at a predetermined frequency that excites a
plurality of resonant modes at the determined weights in the energy
application zone. At least some of the plurality of resonant modes
share a mode family.
[0008] Another exemplary aspect of the invention may be directed to
an apparatus for exciting at least one desired field pattern in an
energy application zone comprising at least two radiating elements.
The apparatus may comprise a first radiating element poisoned to
excite at a given frequency the desired field pattern and one or
more non-desired field pattern. The apparatus may also comprise a
second radiating element poisoned to reject at the given frequency
the one or more of non-desired field patterns.
[0009] Another exemplary aspect of the invention may be directed to
a method for exciting at least one desired field pattern in an
energy application zone comprising at least two radiating elements.
The method may comprise selecting a first radiating element to
excite at a given frequency the desired field pattern and one or
more non-desired field pattern. The method may also comprise
selecting a second radiating element to reject at the given
frequency the one or more of non-desired field patterns. Moreover,
the method may include supplying EM energy at the given frequency
to the first and second radiating elements.
[0010] Another exemplary aspect of the invention may be directed to
an apparatus for applying electromagnetic energy to an object in an
energy application zone. The apparatus may comprise a source of
electromagnetic energy, and one or more radiating element(s) in
communication with the source and positioned to excite only a
single dominant mode within the energy application zone for a
particular frequency. The apparatus may further comprise at least
one processor configured to control at least one of location,
orientation, and polarization of the radiating element.
[0011] As used herein, an object (e.g., a processor) is described
to be configured to perform a task (e.g., cause application of
electromagnetic energy at a frequency that excites a plurality of
modes), if, at least in some embodiments, the object performs this
task in operation. Similarly, when a task is described to be in
order to establish a target result (e.g., in order to excite a
plurality of modes at a single frequency) this means that, at least
in some embodiments, the task is carried out such that the target
result is accomplished.
[0012] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] 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:
[0014] FIG. 1 is a schematic diagram of an apparatus for applying
electromagnetic energy to an object, in accordance with some
embodiments of the present invention;
[0015] FIGS. 2A-2D illustrate degenerate cavities, in accordance
with exemplary embodiments of the present invention;
[0016] FIG. 3A illustrates a rectangular cavity in a Cartesian
coordinate system, in accordance with exemplary embodiments of the
present invention;
[0017] FIG. 3B illustrates a cylindrical cavity in a cylindrical
coordinate system, in accordance with exemplary embodiments of the
present invention;
[0018] FIGS. 4A-4C illustrates cross-section views of a resonant
modes excited in a rectangular cavity, in accordance with exemplary
embodiments of the present invention;
[0019] FIG. 5A-5C illustrate cross-sectional views of three field
patterns excited in a degenerate rectangular cavity at a single
frequency, in accordance with exemplary embodiments of the present
invention;
[0020] FIG. 6A is a schematic diagram of an apparatus configured to
vary the frequency of the electromagnetic waves supplied to the
energy application zone, in accordance with some embodiments of the
invention;
[0021] FIG. 6B is a schematic diagram of an apparatus configured to
vary the phase difference between two electromagnetic fields
supplied to the energy application zone, in accordance with some
embodiments of the invention;
[0022] FIG. 6C illustrates an exemplary modulation space;
[0023] FIGS. 7A-7B illustrate exemplary antenna placement/selection
strategies, in accordance with exemplary disclosed embodiments;
[0024] FIGS. 8A-8E illustrate exemplary antenna placement/selection
strategies in a degenerate cavity, in accordance with exemplary
disclosed embodiments;
[0025] FIGS. 9A-9D illustrate exemplary energy application zone
discretization strategies in accordance with the invention;
[0026] FIG. 10A is an exemplary flow chart of a method for applying
electromagnetic energy to the degenerate energy application zone,
in accordance with some embodiments of the invention;
[0027] FIG. 10B is another exemplary flow chart of a method for
applying electromagnetic energy to the degenerate energy
application zone, in accordance with some embodiments of the
invention.
[0028] FIG. 11 provides an exemplary flow chart of a method for
applying electromagnetic energy to an energy application zone, in
accordance with exemplary disclosed embodiments; and
[0029] FIG. 12 provides another exemplary flow chart of a method
for applying electromagnetic energy to the energy application zone,
in accordance with exemplary disclosed embodiments.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0030] 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.
[0031] Reference is now made to FIG. 1 illustrating an apparatus
for applying electromagnetic energy to an object, in accordance
with some embodiments of the invention. Some embodiments of the
invention may involve a source of electromagnetic energy (e.g.,
including a power supply 12 and at least one radiating element 18),
regulated by a processor 30. For simplicity of the drawing, the
source is not explicitly marked in the figure. The electromagnetic
energy may be applied to an energy application zone, e.g., cavity
20. The energy application zone may be configured in a degenerate
shape, for example those shapes illustrated in FIGS. 2A-2D. As
employed in accordance with some embodiments of the invention, the
degenerate shape, as described later in greater detail, is used to
enable multiple resonant modes to be excited using a single
frequency. That is, a frequency of electromagnetic radiation
emitted by the source may be held constant, and yet two or more
distinct resonant modes may be achieved. This may occur using
processor 30 which may control the way energy is applied, as will
described later in greater detail.
[0032] Conceptually, the result of such control is exemplified in
FIGS. 5A and 5B. FIG. 5A conceptualizes one resonant mode
(TE.sub.104) achieved using a predetermined frequency, while FIG.
5B conceptualizes a second and distinct resonant mode (TE.sub.401)
achieved using the same predetermined frequency. FIGS. 5A and 5B
illustrate the field intensities of TE.sub.104 and TE.sub.401
respectively. In the example of FIGS. 5A and 5B, while the
frequency was held constant, another variable (e.g., phase or
relative amplitude or position of the radiating element emitting
the energy) was varied in order to achieve the second mode.
[0033] Because the modes exhibit predictable areas of energy
intensity, the ability to generate and control the modes permits
control of energy applied in the energy application zone. And with
some embodiments of the invention, this predictability may exist
with multiple modes achieved using a common frequency.
[0034] In some embodiments, the modes of FIGS. 5A and 5B may be
applied simultaneously, in which case the dashed areas
(illustrating higher energy regions, which may also be referred to
as "hot spots"), may be obtained in a different angle respective to
the x axis. For example, when the two modes are applied at equal
amplitudes, a "diagonal" field pattern, as illustrated in FIG. 5C
may be obtained. The "diagonal" field pattern is a linear
combination of the two modes TE104 and TE401. Thus, if we denote
the electrical field pattern shown in FIG. 5A as E5A, the
electrical field pattern shown in FIG. 5B as E5B, and the
electrical field pattern shown in FIG. 5C as E5C, then
E5C=1/2E5A+1/2E5B. FIG. 5C illustrates the field intensities of
ESC. If the weights are different, the angle will be different. If
the weights are varied in time in an appropriate manner, the field
pattern may rotate (e.g., angular shift) in the energy application
zone. For example, if E3C changes in time according to the equation
E5C=sin(.alpha.t) ESA+cos(.alpha.t) ESB, the field rotates at
constant angular frequency of a rounds per second. Such rotation of
the field pattern may be useful to achieve a more uniform
time-averaged heating in the energy application zone than is
achievable with a combination that is constant over time. Replacing
the weights sin(.alpha.t) and cos(.alpha.t) with constants, which
do not vary in time, may freeze the field pattern to achieve a
desired non-uniformity, for example, of the kind illustrated in
FIG. 5C.
[0035] In some embodiments the excitation of at least one desired
mode may be determined by the positioning or location in the energy
application zone of at least one radiating element 18. A single
radiating element may excite in an energy application a plurality
of modes. As used herein, the term "excited" is interchangeable
with "generated," "created," and "applied". Some of the excited
modes may be resonant modes. A radiating element may excite all the
modes supported by the energy application zone as long as the
radiating element is not coinciding with the null (i.e., zero field
intensity) mode. Some of the modes are more "effectively" excited
than others. With the energy supplied from the power supply, modes
that are effectively excited in the zone may apply higher amounts
of energy to the zone than modes that are not effectively excited.
When the radiating element is located close to the intensity maxima
and in particular when the radiating element coincides with the
intensity maxima, the mode is effectively excited in the energy
application zone. When at least two radiating elements are used,
non-desired modes may be rejected by applying the same amount of
energy using the same frequency but in opposite directions, as will
be discussed in greater detail with respect to FIGS. 8D and 8C. In
some embodiments, it may be advantageous to reject undesired modes
in order to have better control of the modes excited in the energy
application zone.
[0036] In some respects, 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" as broadly used herein may refer only to a
processor, such as processor 30, as illustrated, for example, in
FIGS. 1, 6A, and 6B. Alternatively, an "apparatus" may include a
combination of a processor and one or more radiating elements, such
as elements 18 in FIG. 1 and elements 32 and 34 in FIGS. 6A and 6B;
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.
[0037] The term electromagnetic energy, as used herein, includes
energy within 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, respectively. 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.
[0038] 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 also be
applied to an object for heating, combusting, thawing, defrosting,
cooking, drying, accelerating reactions, expanding, evaporating,
sintering, 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.
[0039] Moreover, reference to an "object" (also known as a "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 the invention is
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 apply, even nominally, electromagnetic
energy.
[0040] In accordance with the invention, an apparatus or method may
further involve the use of an "energy application zone". An energy
application zone may be 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.
[0041] The energy application zone may be located in an oven,
chamber, tank, dryer, thawer, dehydrator, reactor, engine, chemical
or biological processing apparatus, furnace, incinerator, material
shaping or forming apparatus, conveyor, combustion zone, or any
area where it may be desirable to apply energy. Thus, consistent
with some embodiments, the electromagnetic energy application zone
may be an electromagnetic resonator (also known as cavity
resonator, resonant cavity, or simply "cavity" for short). The
electromagnetic energy may be applied to an object when the object
or a portion thereof is located in the energy application zone.
[0042] By way of example, an energy application zone, e.g., cavity
20, is illustrated schematically in FIG. 1, where 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] An energy application zone may have a predetermined
configuration (e.g., cavity shape) or a configuration that is
otherwise determinable, so long as physical aspects of its
configuration are known at a time of energy application. In some
respects, an energy application zone may assume any shape that
permits electromagnetic wave propagations 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, toroidal, circular, triangular, oval,
pentagonal, hexagonal, octagonal, elliptical, or any other shape or
combination of shapes. In some respects, the energy application
zone may have particular shape such as degenerate shapes (e.g., as
illustrated in FIGS. 2A-2D) as described later. It is also
contemplated that the energy application zone may be closed, i.e.,
completely enclosed by conductor materials, bounded at least
partially, or open, i.e., having non-bounded openings. The
invention in its broadest sense is not limited to any particular
degree of closure, although in some applications, a high degree of
closure may be preferred.
[0044] In accordance with the invention, an apparatus or method may
involve the use of a source of electromagnetic energy for applying
electromagnetic energy to the object. A "source" may include any
components suitable for generating and/or applying and/or modifying
electromagnetic energy, including at times one or more of each of
the following components: power supply, signal generator, signal
modulator (for example phase and/or frequency modulators),
amplifier and radiating element. Consistent with the invention,
electromagnetic energy may be applied to the energy application
zone in the form of propagating electromagnetic waves at any
wavelengths or frequencies (also known as electromagnetic
radiation). As used herein, "propagating electromagnetic waves" may
include resonating waves, evanescent waves, and 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.
[0045] By way of example, the apparatus may include at least one of
a power supply 12, a modulator 14, an amplifier 16, one or more
radiating elements 18, and a detector 40, as illustrated in FIG. 1.
In some embodiments, one or more of power supply 12, modulator 14,
amplifier 16, one or more radiating elements 18, and detector 40
may be part of the source. Power supply 12 may be configured to
generate electromagnetic waves that carry electromagnetic energy.
For example, power supply 12 may include electromagnetic energy
generating components, for example, a magnetron configured to
generate microwave waves at a predetermined wavelength or
frequency. 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 another type of waveforms with
alternating polarities. Alternatively or additionally, a source of
electromagnetic energy may include any other power supply, such as
electromagnetic field generator, electromagnetic flux generator, or
any mechanism for generating vibrating electrons.
[0046] In some embodiments, the apparatus may include at least one
modulator 14 configured to modify one or more characteristic
parameters of the electromagnetic waves generated by power supply
12, in a controlled manner. For example, modulator 14 may be
configured to modify one or more parameters of a periodic waveform,
including amplitude (e.g., an amplitude difference between
different radiating elements), phase, and frequency. The process of
modifying is known as "modulation".
[0047] In some embodiments, modulator 14 may include, for example,
at least one of a phase modulator, a frequency modulator, and an
amplitude modulator configured to modify the phase, frequency, and
amplitude of the AC waveform, respectively. Exemplary phase
modulator and amplitude modulator are discussed in greater detail
later, for example in connection with FIGS. 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 varying amplitude over time.
[0048] 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 be, for example, a power amplifier
including one or more power transistors. As another example,
amplifier 16 may be a step-up transformer having more turns in the
secondary winding than in the primary winding. In other
embodiments, amplifier 16 may also be a power electronic device
such as an AC-to-DC-to-AC converter. 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.
[0049] The apparatus may also include at least one radiating
element 18 configured to transmit (apply) the electromagnetic
energy to object 50. The radiating element 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. Alternatively,
radiating element 18 may also include waveguides or antennas of any
other kind or form, or any other suitable structure from which
electromagnetic energy may be emitted.
[0050] Power supply 12, modulator 14, amplifier 16, and radiating
element(s) 18 (or portions thereof) may be separate components or
any combination of them may be integrated as a single component.
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 used as power supply 12 to generate
electromagnetic energy, and a waveguide may be physically attached
to the magnetron for applying the energy to object 50.
Alternatively, the radiating element may be separate from the
magnetron. Optionally, other types of electromagnetic generators
may be used where the radiating element may be for example either
physically separate from or part of the generator or otherwise
connected to the generator.
[0051] In some embodiments, more than one radiating element may be
provided. The radiating elements may be located on one or more
surfaces of the energy application zone. Alternatively, radiating
elements may be located inside and/or outside the energy
application zone. When the radiating elements are located outside
the zone, they may be coupled to elements that would allow the
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, or dynamically
adjusted using a processor while applying energy. The invention in
its broadest sense 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. It is noted that the
terms "region" and "area" are used herein interchangeably, to refer
to any particular extent of space or surface.
[0052] In addition to radiating (emitting) electromagnetic energy,
one or more radiating element(s) 18 may also be configured to
receive electromagnetic energy. In other words, as used herein, the
term "radiating element" broadly refers 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 the purposes of radiating or receiving
energy, and regardless of whether the structure serves any
additional function. Thus, 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, detector 40 may be
coupled to radiating elements 18 that, when functioning as
receivers, receive electromagnetic waves from cavity 20.
[0053] As used herein, the term "detector" may include an electric
circuit that measures or senses one or more parameters associated
with electromagnetic waves. For example, such a detector may
include a power meter configured to detect a level of the power
associated with the incident, reflected and/or transmitted
electromagnetic wave (also known as "incident power," "reflected
power," and "transmitted power," respectively), 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. As used herein, incident power may be
supplied to a radiating element functioning as a transmitter by the
source, and then emitted (applied) into the energy application zone
20 by the transmitter. Of the incident power, a portion may be
dissipated by the object (referred to herein as "dissipated
power"). A portion of the dissipated power may be dissipated in the
energy application zone (e.g., cavity walls and/or cavity
entrance). This portion, however, may be substantially small in
comparison to the power that is dissipated in the object and,
therefore, may be neglected in some embodiments. Another portion
may be reflected at the radiating element (i.e., "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 retained
by the port of the transmitter (i.e., power that is emitted by the
antenna but 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 radiating element functioning as
receivers (i.e., "transmitted power.").
[0054] The detector may be a directional coupler, configured to
allow signals to flow from the amplifier to the radiating elements
when the radiating elements function as transmitters (e.g., when
the radiating elements radiate energy), and to allow signals to
flow from the radiating elements to the amplifier when the
radiating elements function as receivers (e.g., when the radiating
element receive energy). Additionally, the directional coupler may
be further configured to measure the power of a flowing signal. The
detector may also include other types of circuits that measure the
voltage and/or current at the ports.
[0055] As previously mentioned, an energy application zone may be
of a degenerate shape (referred herein as a "degenerate energy
application zone"). A degenerate energy application zone may
typically have at least two symmetric dimensions, and such symmetry
may exist about an axis, for example, as in the case of a cylinder,
a cube, any other prism that has a square, hexagonal or octagonal
or other symmetrical cross-section, or other volumes with a round
cross-section. Alternatively, symmetry may exist about a point, for
example, in the case of a sphere. Due to such symmetry, a
degenerate energy application zone may look identical after being
rotated by a certain degree around its axis of symmetry or point of
symmetry.
[0056] Thus, degenerate energy application zones may include
volumes having at least one of a square cross-section and a
circular cross-section, such as the exemplary degenerate cavities
shown in FIGS. 2A and 2B, respectively. In these cases, the energy
application zone is known to have one dimension of degeneracy, that
is, a cross-section is degenerate. The degenerate energy
application zone may also be a sphere or a cuboid, such as the
exemplary degenerate cavities shown in FIGS. 2C and 2D,
respectively. These cavities are symmetric about a central point.
In particular, the spherical cavity shown in FIG. 2C is degenerate
by nature because any cross-section is inherently symmetric.
[0057] A degenerate energy application zone may support two or more
resonant modes that share a mode family, at a single resonant
frequency. The term "resonant", "resonating" or "resonance" refers
to the tendency of electromagnetic waves to oscillate in the energy
application zone at larger amplitudes at some frequencies (known as
"resonant frequencies" or "resonance frequencies") than at others.
Energy application zones 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). Electromagnetic waves
resonating at a particular resonance frequency may have a
corresponding "resonance wavelength" that is inversely proportional
to the resonance frequency, determined by .lamda./=c/f, where
.lamda. is the resonance wavelength, f 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, c may
not be uniquely defined. Nevertheless, the resonance wavelength may
be uniquely determined using a slightly different relation,
including, for example, using an estimation based on c of the major
component or an average of the c of miscellaneous components, or
any other technique known in the art.
[0058] When the electromagnetic waves are emitted at some specific
frequencies, special field patterns, known as "modes," may be
excited. A mode of electromagnetic radiation is a particular
electromagnetic field pattern of radiation measured in a plane
perpendicular to the propagation direction of the wave. The
propagation of electromagnetic waves may be described by a wave
equation. The wave equation is a second-order linear partial
differential equation of waves, including electromagnetic waves. A
mode may correspond to a solution of the wave equation for a
particular set of boundary conditions. A set of boundary conditions
characterizes the behavior of the electromagnetic field at the
boundaries of any wave propagating media. For example, on the
boundary between a dielectric medium and a perfect electric
conductor (PEC), the tangential component of the electric field and
the normal component of the magnetic field are both zero. In other
words, modes include a set of spatial 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 can be of any known type, including
propagating, evanescent, and resonant. In particular, the inventors
have recognized that energy application may be more effectively
controlled by exciting a variety of different resonant modes in the
energy application zone. Any field pattern that may be excited in
an energy application zone 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 some embodiments, the
excited field pattern may include a combination of mainly resonant
modes. More descriptions of modes, the wave equation, and boundary
conditions may be found in references, such as Collin, Robert E.
Foundations for Microwave Engineering, 2nd Edition,
Wiley-Interscience 2001.
[0059] Resonant modes are modes that are excited in an energy
application zone at resonant frequencies associated with the zone.
Consistent with presently disclosed embodiments, the degenerate
energy application zone may support two or more resonant modes that
share a mode family. For a given cavity, the wave equation may
yield a set of modes in the same mode families, i.e. modes that
correspond to the same set of boundary conditions. If a cavity can
support more than a single mode at a same frequency in the same
family, it is a degenerate cavity.
[0060] In some embodiments, modes in a same mode family may be of a
same transverse type. A resonant mode may be of any known
transverse type, including transverse electromagnetic (TEM),
transverse electric (TE), transverse magnetic (TM), and hybrid. A
"transverse mode" of electromagnetic radiation, as referred herein,
is a particular electromagnetic field pattern of radiation measured
in a plane perpendicular (i.e. transverse) to the propagation
direction of the electromagnetic wave. For example, in a TE mode,
the electric field is zero in the direction of propagation. In a TM
mode, the magnetic field is zero in the direction of propagation.
In a TEM mode, both electric field and magnetic field are zero in
the direction of propagation, while in a hybrid mode, both electric
field and magnetic field may be non-zero in the direction of
propagation.
[0061] By way of example, FIG. 3A illustrates a rectangular
resonant cavity 62 having physical dimensions of a, b, and c, in
the x, y, and z directions, respectively. A standing wave pattern
in cavity 62 may have integer number of half-wavelengths along each
of the three directions. Therefore, a resonant mode excited in
cavity 62 may be uniquely identified using its transverse type
(e.g., TE, TM, TEM, etc.), and a combination of three integers (m,
n, l), where m, n, l refer to the number of half-wavelengths in the
standing wave pattern in the x, y, z directions, respectively. FIG.
4A-4C show three cross-sectional views of mode TE.sub.234 in the
x-y plane, x-z plane, and y-z plane, respectively. The shaded ovals
represent areas where magnitudes of field intensity are higher than
a certain threshold value. It is hereby noted that while shaded
ovals may be diagrammatically illustrated as having a clear and
defined border, in reality the intensity changes in a more gradual
manner.
[0062] The resonant frequency corresponding to a specific resonant
mode may be uniquely determined based on the geometry (e.g., shape
and dimensions) of the energy application zone (e.g., cavity
shape). For example, the resonant frequencies of cavity 62, as
shown in FIG. 3A, may be determined mathematically as:
f mnl = c 2 .pi. .mu. r r ( m .pi. a ) 2 + ( n .pi. b ) 2 + ( l
.pi. c ) 2 ( 1 ) ##EQU00001##
where .mu..sub.r and .epsilon..sub.r are the relative permeability
and relative permittivity of the material in cavity 62. In one
embodiment, if .mu..sub.r=.epsilon..sub.r=1, a=0.3 m, b=0.4 m, and
c=0.5 m, accordingly to equation (1), the resonant frequencies of
modes TM.sub.102, TE.sub.213, and TM.sub.111 are approximately 781
MHz, 1.396 GHz, and 693 MHz, respectively.
[0063] By way of another example, FIG. 3B illustrates a cylindrical
resonant cavity 64 having physical dimensions of r, and d,
corresponding to the radius and length, respectively. The resonant
frequencies of the TE.sub.nml modes and TM.sub.nml modes in cavity
64 may be determined mathematically as:
f nml ( TE ) = c 2 .pi. .mu. r r ( .rho. nm r ) 2 + ( l .pi. d ) 2
( 2 ) f nml ( TM ) = c 2 .pi. .mu. r r ( .rho. nm ' r ) 2 + ( l
.pi. d ) 2 ( 3 ) ##EQU00002##
where .rho..sub.nm refers to the m-th zero of Bessel function of
the first kind J.sub.n(x), and .rho.'.sub.nm refers to the m-th
zero of the derivative of the Bessel function of the first kind
J'.sub.n(x). In one embodiment, if .mu..sub.r=.epsilon..sub.r=1,
and r=0.3 m, d=0.5 m, accordingly to equations (2) and (3), the
resonant frequencies of modes TM.sub.102, TE.sub.213, and
TM.sub.111 are approximately 1.343 GHz, 1.772 GHz, and 2.007 GHz,
respectively.
[0064] Generally, for a given energy application zone, at most one
resonant mode of a transverse mode may be supported at each
resonant frequency, because of the unique mapping relationship
between a resonance frequency and a particular combination of m, n,
and l. However, for a degenerate energy application zone, two or
more resonant mode of a same transverse mode may be supported at a
single resonance frequency. For example, assuming that the
cross-section in the x-y plane is degenerate, then any frequency
that can excite TE.sub.mnl mode in the cavity can also excite
TE.sub.nml mode in the cavity.
[0065] Using rectangular cavity 62 of FIG. 3A as an example, when
a=b, that is, the cross-section of cavity 62 in the x-y plane is
square, cavity 62 becomes a degenerate cavity. For example,
assuming .mu..sub.r=.epsilon..sub.r=1, a=b=0.3m and, c=0.5m, cavity
62 may support two TE modes (TE.sub.213 and TE.sub.123) at the
frequency of 1.436 GHz. In comparison, when a>b>c, cavity 62
is a non-degenerate cavity. For example, assuming
.eta..sub.r=.epsilon..sub.r=1, and a=0.3m, b=0.4m, c=0.5m, cavity
62 may support only one TE mode (TE.sub.213) and one TM mode
(TM.sub.213) at the frequency of 1.396 GHz. Cylindrical cavity 64
of FIG. 3B is degenerate by nature as the result of its circular
cross-section which is symmetric about a central axis.
[0066] An apparatus or method of the invention may further 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.
[0067] 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, a 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.
[0068] If more than one processor is employed, all may be of
similar construction, or they may be of differing constructions
electrically connected or disconnected from each other. 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.
[0069] 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.
[0070] The at least one processor may regulate the one or more
components of the source or apparatus according to a predetermined
energy delivery scheme. For example, as depicted in FIG. 1, an
exemplary processor 30 may be electrically coupled to various
components, for example, power supply 12, modulator 14, amplifier
16, and radiating elements 18. One or more of power supply 12,
modulator 14, amplifier 16, and radiating elements 18 may be a
component of the source. 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. Processor 30 may also regulate the amplification
ratio of amplifier 16, by switching for example 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. In another example,
processor 30 may alternatively or additionally regulate at least
one of location, orientation, and configuration of each radiating
element 18, for example 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
simultaneously match the radiating element that acts as a
transmitter to reduce coupling to the other radiating elements that
act as receivers.
[0071] The at least one processor may be configured to regulate
application of electromagnetic energy at a predetermined frequency.
For example, processor 30 may regulate a frequency modulator in
order to set 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 be a semiconductor
oscillator, e.g., oscillator 22 schematically depicted in FIG. 6A,
and configured to generate an AC waveform oscillating at a
determined frequency. The determined 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. The AC waveform may be amplified by an amplifier, e.g.,
amplifier 24 schematically depicted in FIG. 6A, to a desired
amplitude/power, before input to one or more radiating elements,
e.g., antennas 32 and 34 illustrated in FIG. 6A.
[0072] The determined frequency may satisfy a "modal condition."
The "modal condition" can be expressed as a relationship between
the applied frequency f.sub.1 and the lowest resonant wavelength
f.sub.0 that may excite a mode in the energy application zone. In
some embodiments, the modal condition may be expressed as
f.sub.1.ltoreq.4f.sub.0, that is, the electromagnetic energy may be
applied at a determined frequency that is lower than about four
times the lowest resonance frequency in the energy application
zone. When the modal condition is satisfied, energy application to
the object may be better controlled and more efficient.
[0073] The lowest resonant frequency f.sub.0 may be determined as a
function of the largest resonant wavelength .lamda..sub.0 supported
by the energy application zone, using f.sub.0=c/.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. For example, for the cubic cavity of FIG.
2D, which is of dimensions a.times.a.times.a, the largest resonant
wavelength .lamda..sub.0 may be given by {square root over (2)}a.
As another example, for the spherical cavity of FIG. 2C, with a
radius r, the largest resonant wavelength .lamda..sub.0 may be
given by
2 .pi. r 2.744 . ##EQU00003##
As yet another example, for cylindrical cavity 64 of FIG. 3B, with
a radius r and a length d, then if 2r>d the largest resonant
wavelength .lamda..sub.0 may be given by
2 .pi. r 2.405 , ##EQU00004##
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 . ##EQU00005##
As yet another example, for rectangular cavity 62 of FIG. 3A, 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 . ##EQU00006##
Once me largest resonant wavelength .lamda..sub.0 and its
corresponding lowest resonant frequency f.sub.0 are determined, the
determined frequency f.sub.1 to be used for applying the
electromagnetic energy to the energy application zone, according to
the modal condition f.sub.1<4f.sub.0.
[0074] 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.times.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). In some embodiments, the apparatus
may be configured to operate only in a range of wavelengths that
satisfy the modal condition of its cavity. In some embodiments, the
apparatus may be configured to operate both in wavelengths that
satisfy the modal condition, and in wavelengths that do not satisfy
this condition.
[0075] The determined frequency may be a resonant frequency
associated with the energy application zone. For example, in
rectangular degenerate cavity 62, the determined frequency may be
one that satisfies equation (1). As another example, in cylindrical
degenerate cavity 64, the determined frequency may be one that
satisfies equation (2) or (3).
[0076] The resonant frequencies in a cavity may vary in a presence
of a load (e.g., object 50) in the energy application zone. The
load presence may change the boundary conditions in the cavity and
may cause a shift in the resonance frequencies, such that the
frequencies may no longer satisfy equations (1), (2) or (3). The
resonant frequencies in the presence of the load may be determined
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
reflected/transmitted electromagnetic energy from cavity 20 at each
of a plurality of frequencies in a working band, in the presence of
the load in the cavity (e.g., energy that is reflected back to the
radiating element acting as transmitter and/or energy that is
transmitted back to radiating element(s) acting as receivers). The
resonant frequencies may be determined, as the frequencies having
lowest reflected electromagnetic energy picks when the reflected
energy is plotted against the frequencies. Optionally, processor 30
may be configured to determine a value indicative of the energy
absorbable in the load based on the portion of the incident energy
that is reflected and/or the portion that is transmitted. The
resonant frequencies may be determined, as the frequencies having
the highest energy absorbable picks when the value is plotted
against the frequency.
[0077] The resonant frequencies may be predicted and may satisfy
equations (1), (2) or (3) in a presence of a load when the load is
homogeneous and fills substantially the entire energy application
zone.
[0078] A load may be considered to fill substantially the entire
energy application zone if the effect of the unfilled regions is
negligible. For example, a load filling substantially the entire
energy application zone may fill at least 80%, 85% or 90% of the
zone. In some embodiments, the load fills the entire zone except
for some excluded volumes that may be occupied, for example, with
radiating elements (e.g., RF feeds), detectors, thermometers, or
other equipment that may be useful for the operation of the
apparatus. Some marginal volumes that are not filled with the
object, for example, at corners of a cavity, may also exist in a
substantially filled energy application zone.
[0079] An example of a homogeneous load is one with no
dielectric-boundaries. A dielectric boundary is a line or surface
that separates between two regions, each having a significantly
different dielectric constant (.epsilon..sub.r). A characteristic
size of each of the regions may be of the order of at least about a
wavelength in the load. The wavelength in the load may be
approximated by an average between the wavelength in both sides of
the lines or surface that separates between the regions. A
difference in dielectric constant may be considered significant,
for example, if the difference is of about 10%. One example of a
homogeneous load is a body of water. It is noted that if different
portions of the body of water are at different temperatures, for
examples, because of non-uniform heating, the dielectric constant
of the different portions may differ. If this difference is larger
than 10%, however, the body of water may be considered
inhomogeneous.
[0080] A suspension of oil in water (or of any other two materials)
may be considered homogeneous, provided the oil droplets (or
particles of other suspended medium) are smaller than the
wavelength at the frequency (e.g., smaller than tenth of the
wavelength), in the suspension as a whole. This may be so despite
of the large difference in dielectric constant between oil and
water.
[0081] The processor may be configured to regulate the source to
apply electromagnetic energy that result in a plurality of resonant
modes in the energy application zone at a single determined
frequency, wherein the plurality of resonant modes may share a mode
family. For example, the plurality of resonant modes may all be of
the same transverse type as one another. This phenomenon is
facilitated by cavity degeneracy.
[0082] A plurality of modes that exist at the same frequency need
not occur simultaneously in the zone. Rather, in accordance with
some embodiments of the invention, they may occur at differing
times or at the same time, so long as more than one resonant mode
is excitable with a single frequency.
[0083] In accordance with some embodiments of the invention, the at
least one processor may be further configured to regulate the
source to vary a phase difference between two electromagnetic
fields applied at a single predetermined frequency, wherein each
resonant mode excited in the degenerate energy application zone
corresponds to a phase variation. The source may be regulated to
apply electromagnetic energy using two synchronized radiating
elements. As referred herein, two radiating elements are
"synchronized" if the electromagnetic waves emitted by the two
radiating elements have a known phase difference. For example, two
radiating elements, e.g., radiating elements 32 and 34 illustrated
in FIG. 6A, may apply energy at phases .phi..sub.1 and .phi..sub.2,
respectively, where the phase difference .DELTA..phi. is
constant.
[0084] In some embodiments, processor 30 may regulate the source to
vary the phases .phi..sub.1 and/or .phi..sub.2 such that energy is
applied at differing phase differences. For example, the source may
be regulated to apply energy at one phase difference during a first
time period, and another phase difference during a second time
period. In one example, the phase differences may be so chosen that
energy applied at each phase difference may excite one mode, among
the plurality of modes. For example, the source may be regulated to
apply electromagnetic energy at two phase differences that are
180.degree. apart from each other, so that each phase difference
may excite one of two orthogonal modes in a rectangular cavity. As
referred herein, two modes 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. Using the
example shown in FIGS. 5A and 5B, .DELTA..phi.=0.degree. may be
used to excite TE.sub.104 and .DELTA..phi.=180.degree. may be used
to excite TE.sub.401 in a rectangular degenerate cavity.
[0085] In some exemplary embodiments, 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, illustrated in
FIG. 6B. 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. Alternatively or additionally, the processor 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 (e.g., detected) 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.
[0086] 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.
[0087] As illustrated in the example depicted in FIG. 6B, 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."
[0088] Because the split signals 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 a, 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.]. As illustrated in FIG.
6B, the phase shifted AC signals may be amplified by amplifiers 24
and 28, respectively, and in this manner radiating elements 32 and
34 may be caused to excite electromagnetic waves having a shared AC
waveform. Radiating elements 32 and 34 may be positioned at 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).
[0089] As with the other examples provided, FIG. 6B is exemplary.
It is to be understood that one, two, or more phase shifters can be
used applying similar principles of some embodiments of the
invention.
[0090] As previously mentioned, the at least one processor may
regulate the source to apply electromagnetic energy at a plurality
of frequencies, e.g., resonant frequencies. For example, processor
30 may be configured to regulate oscillator 22 to sequentially
generate AC waveforms oscillating at various frequencies of cavity
20. This sequential process may be referred to as "frequency
sweeping." In some embodiments, processor 30 may be configured to
select one or more frequencies, and regulate oscillator 22 to
sequentially generate AC waveforms at these selected frequencies.
In some other embodiments, processor 30 may also regulate more than
one sources to apply electromagnetic energy at differing resonant
frequencies.
[0091] An apparatus for applying electromagnetic energy, for
example the apparatus of FIGS. 1, 6A and 6B, may be configured to
control application of electromagnetic energy at a frequency that
excites a plurality of modes in the energy application zone. The
plurality of modes may share a mode family. Such control may occur
through the selection of "MSEs" (as described later). Choices of
MSE selection may influence 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 can 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.
[0092] In some embodiments, in order to further simplify the energy
application control, it may be desired to excite only small number
of desired modes and to reject the entire undesired mode. Choices
of MSE selection may influence the rejection of undesired modes. An
MSE may include the number and location of radiating elements in
the energy application zone and application of selected MSEs may
result in excitation of only the desired modes.
[0093] 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.
[0094] Examples of energy application zone-related MSs may include
the dimension, and shape of the energy application zone and the
materials from which the energy application zone is constructed.
Examples of energy source-related MSEs may include amplitude (e.g.,
an amplitude difference between different radiating elements),
frequency, and phase of the energy applied. Examples of radiating
element-related MSEs may include the type, number, size, shape,
configuration, orientation and placement of radiating elements.
[0095] Each variable parameter associated with the MS is referred
to as an MS dimension. By way of example, FIG. 6C illustrates a
three dimensional modulation space 400, with three dimensions
designated as frequency (F), phase (.phi.), and amplitude (A). That
is, in MS 400, frequency, phase, and amplitude of the
electromagnetic waves are capable of being 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 energy
delivery, or any other higher-dimensional where more than one
parameters are varied. In FIG. 6C, the modulation space is depicted
in three dimensions for ease of discussion only. The MS may have
many more dimensions.
[0096] 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. For example, FIG. 6C shows an MSE 401 in the
three-dimensional MS 400. MSE 401 has a specific frequency F(i), a
specific phase .phi.(i), and a specific amplitude A(i). If even one
of these MSE variables change, then the new set defines another
MSE. For example, (3 GHz, 30.degree., 12 V) and (3 GHz, 60.degree.,
12 V) are two different MSEs, although only the phase component
changes. 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 differ significantly from MSE to MSE, possibly
with no logical relation between them, however in the aggregate, a
group of working MSEs may achieve a desired energy application
goal. A plurality of MSEs that can be executed sequentially or
simultaneously to excite a particular field pattern in the energy
application zone may be collectively referred to as an "energy
delivery scheme." For example, an energy delivery scheme may
consist of three MSEs (F(1), .phi.(1), A(1)), (F(2), .phi.(2),
A(2)), (F(3), .phi.(3), A(3)). Since there are a virtually infinite
number of MSEs, there are a virtually infinite number of different
energy delivery schemes, resulting in virtually infinite number of
differing field patterns in any given energy application zone
(although different MSEs may at times cause highly similar or even
identical field patterns). Of course, the number of differing
energy deliver schemes may be, in part, a function of the number of
MSEs that are available. The invention, in its broadest sense, is
not limited to any particular number of MSEs or MSE combinations.
Rather, the number of options that may be employed could be as few
as two or as many as the designer desires, depending on factors
such as intended use, level of desired control, hardware or
software resolution and cost.
[0097] In some embodiments, the at least one processor may regulate
the source to apply electromagnetic energy using "frequency
sweeping" and "phase sweeping" in an alternating manner. For
example, resonant frequency f.sub.1 may be used first, and at
frequency f.sub.1, two or more phase differences may be executed
for applying the energy. Then resonant frequency f.sub.2 may be
used secondly, at which the same or different phase differences as
those used at f.sub.1 may be executed for applying the energy. Each
combination of frequency and phase difference that is used for
exciting the modes is referred to as an "excitation scheme," and
the various excitation schemes used for a particular energy
application is referred to as an "energy delivery scheme." By using
such an energy delivering scheme involving alternating frequency
sweeping and phase sweeping, a plurality of resonant modes may be
excited at each different resonant frequency.
[0098] The plurality of resonant modes excited by a particular
energy delivery scheme may result in an accumulated effect of
electromagnetic energy application over time. In some instances,
the accumulated energy application may be viewed as a linear
combination of energy applications via various resonant modes, and
the accumulated energy application may be controlled by varying a
weight of one or more resonant modes in the linear combination.
[0099] In some embodiments, processor 30 may be configured to
regulate several components simultaneously, including, for example,
phase shifter 54, oscillator 22, splitter 52 and amplifiers 24 and
28, to sequentially cause the application of various MSEs (e.g., by
sequentially sweeping over frequencies, phases and/or
amplitudes)--a process known as "MSE sweeping." MSE sweeping may be
performed relative to any other parameters applicable to the MS,
including, for example, the number, location and/or orientation of
antennas, the dimensions of the energy application zone, the
location and number of the field adjusting elements, etc. The MSE
sweeping of amplitude, frequency and phases is described herein as
an example only and is not intended to limit the invention to those
particular parameters. Any parameter that defines the MS may be
swept during "MSE sweeping."
[0100] In accordance with some embodiments of the invention, the at
least one processor may be further configured to change a weight of
a resonant mode, among the plurality of resonant modes. The
intensity of a resonant mode may be proportional to the amplitude
of electromagnetic waves that excite that resonant mode. Therefore,
the weight of the resonant mode may be changed, for example, by
adjusting an amount of the applied electromagnetic energy exciting
the resonant mode. For example, processor 30 may be configured to
regulate amplifier 24 to adjust the power level at which the
electromagnetic energy is applied for exciting a resonant mode.
Alternatively or additionally, processor 30 may be configured to
adjust the time duration over which the energy is applied for
exciting a resonant mode.
[0101] In accordance with some embodiments of the invention, the at
least one processor may be further configured to determine the
weight of the resonant mode such that differing targeted amounts of
electromagnetic energy are applied to differing predetermined
regions in the object. The term "region" may include any portion of
the object, such as a cell, sub-volume, sub-division, discrete
sub-space, or any sub-portion of a cavity. For example, the object
may include two regions that have differing energy absorption
characteristics within the object. For example, in a cup of chunky
soup, the first region may contain mostly water at the top layer of
the soup, and the second region may contain mostly potato chunks
toward the bottom layer of the soup. Because of their differing
energy absorption characteristics, it may be beneficial to apply
differing amounts of energy to these two regions.
[0102] In some embodiments, the processor may determine weights
dynamically and/or adaptively, optionally based on feedback from
the energy application zone, optionally in the presence of the
object. For example, processor 30 may be configured to receive an
analog or digital feedback signal from detector 40, indicating an
amount of reflected and/or transmitted electromagnetic energy from
cavity 20 when a particular resonant mode is excited in the cavity.
Processor 30 may then dynamically determine the weight for this
particular resonant mode based on the feedback. The processor 30
may, for example, be configured to assign a smaller weight to a
resonant mode when the corresponding reflected/transmitted energy
is low.
[0103] In some instances, the processor may determine the weights
based on characteristics of the target energy distribution. For
example, a spatial distribution of target energy application in the
object may be uneven. On the other hand, each of the excited
resonance modes may include some areas with relatively high
magnitude of field intensity and some other areas with relatively
low magnitudes of field intensity. Thus, in some embodiments, the
processor may assign a greater weight to a resonant mode having
high intensity areas aligned with areas demanding high energy
application.
[0104] In some embodiments, the processor may determine two
different weights for at least two known modes in order to cause a
desired angular shift in the field pattern exited by the two modes.
An angular shift may be defined as a change in angle of the EM
field intensity maxima relative to the location of the maxima when
the two modes are excited with substantially similar weights. The
angular shift is measured around the central symmetry axis created
by the excitation of the at least two modes. In some embodiments
the two modes may be orthogonal to each other and the symmetry axis
may be substantially located in the center of the energy
application zone. Applying different known weights to the two
orthogonal modes may result in a rotation of the maxima intensity
area in the field pattern around a central symmetry axis at a
desired angle to achieve a desired angular shift. The desired
angular shift may continuously change the weights of the modes to
cause a complete rotation of the field intensity maxima around the
central symmetry axis. Continuous angular shift may result in
rotating of the field intensity maxima, which may yield more
uniformity in application of EM energy application.
[0105] For example, two signals supplied to two radiating elements,
respectively, may be represented by A.sub.1cos(.omega.t) and
A.sub.2sin(.omega.t), wherein A.sub.1 and A.sub.2 are the
amplitudes (which may correspond to the weight of that mode/signal)
of the two signals and may be controlled by the processor 30 to
vary in such a manner: A.sub.1=cos(.alpha.) and
A.sub.2=sin(.alpha.). According to trigonometric identity, the
combination of the two amplified signals are
A.sub.1cos(.omega.t)+A.sub.2sin(.omega.t)=cos(.alpha.)cos(.omega.t)+sin(.-
alpha.)sin(.omega.t)=cos(.omega.t-.alpha.). Therefore, the
processor may control the phase of the combined signal supplied to
the cavity by controlling the amplitude of the individual signals
supplied to each of the antennas. Changing the weight (e.g.,
amplitudes A1 and A2) of each signal may result in different phase
shift.
[0106] The processor may determine the weights using linear
algebra. For example, the excited modes may be used to construct a
targeted energy delivery pattern (scheme), and the weights of the
excited modes may be solved based on the targeted energy delivery
pattern. The excited modes may be predicted, for example, through
testing, simulation, or analytical calculation. Using the testing
approach, sensors (e.g., small antenna(s)) may be placed in an
energy application zone, to measure the field distribution of each
mode. The distribution can then be stored in, for example, a
look-up table. In a simulated approach, a virtual model may be
constructed so that the modes can be excited in a virtual manner.
For example, a simulation model of an energy application zone may
be performed in a computer. A simulation engine such as CST by CST
Germany or HFSS by Ansoft Corp. USA may be used to numerically
calculate the field distribution inside the energy application
zone. This simulated approach can occur in advance and the known
combinations may be stored in a look-up table, or the simulation
may be conducted on an as-needed basis during an energy application
operation.
[0107] Similarly, as an alternative to testing and simulation,
calculations may be performed based on an analytical model in order
to predict the excited modes based on excitation schemes. For
example, given the shape of an energy application zone with known
dimensions, the at least one processor may be configured to
calculate modes corresponding to a given excitation schemes from
analytical equations. As with the simulated approach, the
analytical approach may occur well in advance and the known
combinations stored in a look-up table, or may be conducted on an
as-needed basis during an energy application operation.
[0108] In some embodiments, two or more antennas may be used to
reject a mode even when they are not positioned at nulls of the
mode. For example, at least one of the antennas may be at a
non-null position such that the superposed weight of the antennas
on the mode is zero. In some other embodiments, a single antenna or
an array antenna at a non-null position of a mode may also be
configured to reject the mode.
[0109] FIGS. 7A and 7B further illustrate various positions where
an antenna may be placed to excite or not excite a particular mode,
in accordance with some embodiments of the invention. For example,
in FIG. 7A, a cavity 700 may support a TM.sub.320 mode. The mode is
characterized by local maximum and minimum amplitudes of field
intensity. As shown in FIG. 7A, the dash lines correspond to nulls
(i.e., zero amplitude of field intensity) of the mode, while the
six oval structures correspond to regions where the amplitude of
the field intensity is higher than a threshold. More specifically,
the amplitude of the field intensity is higher in the center of
each of the oval structures and decreases gradually toward the
peripheral area. An antenna may be placed at positions 702, 704,
706, or 708 to either excite or not excite this particular mode.
For example, when the antenna is placed at position 702, the mode
may be excited to a maximum degree, because position 702
corresponds to the location where the amplitude of the field
intensity reaches its maximum. As a result, an antenna placed at
position 702 will enable application of electromagnetic energy from
the antenna to cavity 700 at a maximal rate.
[0110] In contrast, when the antenna is placed in position 704 or
706, the mode cannot be excited. Because these two positions
correspond to the nulls of the mode, antennas placed at such nulls
cannot excite the TM.sub.32 mode within the cavity. An intermediate
position, such as position 708, however, may also be used to excite
the mode. Such an intermediate position is neither located at the
maximum nor the nulls of the amplitude of field intensity. By
placing an antenna in the intermediate position, the mode can be
excited, but not to the maximal degree. Therefore, the excitation
of mode TM.sub.32 using an antenna placed in position 708 may be
referred to as a regular excitation.
[0111] FIG. 7B shows another example of mode excitation. In FIG.
7B, cavity 700 may support a mode TM.sub.24. According to the nulls
and maximums of the amplitude of field intensity, an antenna placed
at position 710 or 720 may achieve maximal excitation of mode
TM.sub.24, an antenna placed at position 712 may achieve regular
excitation of mode TM.sub.24, and an antenna placed at position
714, 716, or 718 may not excite mode TM.sub.24.
[0112] In certain embodiments, radiating element (e.g., radiating
element 18) may be positioned such that only a single dominant mode
at a given frequency may be excited in the energy application zone.
For example, referring to FIGS. 8A-8D, two dominant modes 802
(TM.sub.21) and 806 (TM.sub.12) may be excited in a cavity 800 at a
given frequency if cavity 800 is degenerated in the x-y plane
having a=b. Cavity 800 may not need to be degenerated also in the z
direction for the excitation of 802 and 806 modes. Modes 802
(TM.sub.21) and 806 (TM.sub.12) may be excited in the cavity 800 by
any single frequency equal to or higher than the cutoff frequency
f.sub.12=f.sub.21 of TM.sub.21/TM.sub.12. Some of the frequencies
that may excite modes 802 and 806 may be resonant in cavity 800
while other may be propagating or evanescent. In FIG. 8A, an
antenna 804 may be placed in the upper wall of cavity 800 in 1/4 of
the cavity dimension a in the y direction and 1/4 of cavity
dimension a in the x direction, as illustrated in FIGS. 8A and 8C,
while in FIG. 8B, two antennas 808 and 810 may be placed at the
upper wall of the cavity 800, in 1/2 of the cavity dimension a in
the x direction and 1/4 and 3/4 of the cavity dimension a in the y
direction as illustrated in FIGS. 8B and 8D. Although both modes
802 and 806 may be excited in cavity 800, when antenna 804 is
placed as shown in FIG. 8A, mode 802 may be excited and mode 806
may not be excited. This is because the location of antenna 804
coincides with the null (i.e., zero field intensity) of mode 806,
thereby mode 806 cannot be excited. Similarly, when two antennas
808 and 810 are used and placed as shown in FIG. 8B, only mode 806
may be excited and mode 802 may not be excited, because two
antennas 808 and 810 are placed at the nulls of mode 802. As used
herein, the term "position" may include any one of location,
orientation, and polarization, or any combination thereof. Mode 806
of the type TM.sub.12 may be excited using either antenna 808 or
antenna 810, or both.
[0113] In some embodiments, antennas 808 and 810 may be used to
excite modes other than TM.sub.12. For example, when the excitation
from the two antennas is in the same frequency having substantially
the same amplitude and the same dipole, mode 812 of the type
TM.sub.11 may be excited, as illustrated in FIG. 8E. The excitation
from both antennas may contribute to the intensity maximum at the
center of plane x-y. In some other embodiments, antennas 808 and
810 may reject the excitation of mode 812. In case the excitation
from the two antennas is at the same frequency having substantially
the same amplitude but with opposite sign, the contribution from
one antenna may cancel the contribution from the other antenna and
mode TM.sub.11 may be rejected. However, mode 806 (TM.sub.12) may
be excited having two maxima intensities each correspond to
excitation from different antennas, as illustrated in FIG. 8B.
[0114] An energy application zone may include a degenerate cavity.
For example, cavity 800 in FIGS. 8A-8D represents a degenerate
cavity, and modes 802 and 806 may be orthogonal to each other. By
placing antennas 804 or 808 and 810 in the positions illustrated in
FIGS. 8A-8D, only one dominant mode may be excited and the other
orthogonal mode may not be excited.
[0115] A plurality of radiating elements may be configured to
supply electromagnetic energy from the source to the zone, and the
radiating elements may be positioned to reject at least one mode.
For example, using two antennas 808 and 810, at the positions
illustrated in FIG. 8B, may be employed to reject mode 812,
illustrated in FIG. 8E, while optionally exciting mode 806. The
rejection or excitation of mode 812 may be facilitated by selecting
antennas 808 and 810 to supply energy at the same frequency and at
the same amplitude but at opposite directions (phases)--rejection
of mode 812 may be obtained.
[0116] In another example, in FIGS. 7A and 7B, multiple antennas
may be placed simultaneously at various positions shown in the
figures. The number and location of antennas used in a specific
application may depend on desired mode(s) to be excited, mode(s) to
be rejected or not excited, purity of the excited mode(s), control
complexity, cost, or other considerations.
[0117] The plurality of radiating elements may be associated with a
single wall of the energy application zone. For example, in FIG.
8B, two antennas 808 and 810 are placed on the upper wall of cavity
800. By placing antennas on a single wall, the construction of the
cavity and antennas may be simplified. In other embodiments,
however, antennas may be placed on multiple walls of the cavity,
depending on design considerations. For example, to place antennas
in multiple walls, the coupling between antennas may be reduced,
controllability may be enhanced and noise immunity may be
increased.
[0118] Processor 30 may be configured to select a subset of the
plurality of radiating elements to reject at least one mode. For
example, an array of antennas may be provided and processor 30 may
be configured to select one or more antennas in the array to excite
or reject one or more modes. The array of antennas may occupy a
portion of the energy application zone with each antenna in the
array corresponding to a spatial location in the zone. The
processor may select one or more antennas to supply electromagnetic
energy to the zone in accordance with the relationship between the
position of the selected antenna(s) and the mode(s). For example,
in FIGS. 8A-8E, antennas 804, 808, and 810 may constitute an
antenna array or a portion of an antenna array. When mode 802 is to
be excited and mode 806 to not be excited, processor 30 may select
antenna 804 to supply electromagnetic energy and deselect antennas
808 or 810 by, for example, disconnecting them from the source or
putting them in idle mode. When mode 806 and/or mode 812 are to be
excited and mode 802 to not be excited, the processor may select
antennas 808 and 810 and deselect antenna 804. The antenna array
may be placed on a single wall of the cavity or on multiple walls
on the cavity as discussed above.
[0119] In some instances, the calculation of modes may be made
without considering the existence of the object in the energy
application zone. This may be based on the assumption that the
existence of object in the energy application zone does not change
the intensity distribution of the modes in the zone (known as "Born
approximation.) Born approximation is particularly helpful when the
location, size and electromagnetic characteristics of the object
are unknown before the energy application. When the properties of
the object are known before hand, the calculation may also be made
with consideration of the object.
[0120] The processor may be further configured to discretize each
resonant mode corresponding to spatial field distribution (e.g.,
field intensity distribution) in the energy application zone, by
mapping the resonant mode to a discretized energy application zone.
An energy application zone may be discretized, such that a unique
memory address of the processor is associated with each discretized
subregion. FIGS. 9A-9C illustrate examples of discretization
strategies for energy application zone 20. The term discretization
may also be referred to as, for example, division, separation, or
partition. The discretization of an energy application zone into
subregions may be predetermined. In some embodiments, a 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, discretization
may occur dynamically using at least one processor (e.g., processor
30 illustrated in FIG. 1). For example, when known dimensions of
the zone are provided to the processor, the processor may overlay a
regular or irregular division pattern on the volume, divide the
zone into subregions, and assign a memory address to each
subregion.
[0121] The discretization strategy may depend on many factors,
including but not limited to: desired resolution, properties of a
loss profile, and available field patterns. A loss profile may be
understood as any representation of the energy application zone or
the object ability to absorb energy across its volume, for example,
a 3D (3 dimension) map of a cavity, with or without an object to be
heated, wherein each portion of the map is colored in accordance
with the ability of that portion to absorb energy. The regions may
be of a regular or irregular shape. For example, the division of
the zone into subregions may occur through the application of a
regular pattern, such as is the case with the division in FIG. 9A.
Alternatively, the regions may be any irregular-shape depending on
particular needs. For example, the energy application zone may be
divided into somewhat random regions as shown in FIG. 9B. In some
embodiments, the division may occur by taking into account the
location of an object in the zone and/the characteristics of a
specific field pattern applied to the zone.
[0122] In certain locations of the object or zone, 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 or
zone. For example, the dividing strategy may vary depending on
whether a region corresponds to a portion of an object, for example
object 50, in the energy application zone that is targeted for
energy application or 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 can be termed "void
zone"). In some circumstances, the targeted portion of the object
may include the entire object. In some circumstances, non-occupied
portion of the zone may be treated as part of the void zone.
According to an exemplary 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 the targeted portion 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 or the spatial
location of the targeted portion of the object. Alternatively, the
dividing may be carried out separately for the portion of the zone
occupied by the targeted portion of 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
targeted portion of the object. For example, the average size of
regions in the void zone may be larger than that inside the
targeted portion of object 50, as illustrated in FIG. 9C. In other
words, the density of regions in the void zone may be lower than
that inside the targeted portion of the object. The illustrations
of FIGS. 9A-C are exemplary only. An infinite number of
discretization strategies are contemplated within the scope of the
invention, depending on the designer's choice.
[0123] An example of a discretized energy application zone 820 is
discussed below in connection with FIG. 9D. A 2D (two dimension)
model is illustrated for simplicity; however the same method may be
applied to a 3D (three dimension) model. In FIG. 9D, energy
application zone 820 may be divided into multiple regions with each
region having substantially the same regular squared shape.
However, it is contemplated that the methods described below
applies to discretizations where zone 820 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. An object 830 may include more than one region,
e.g., regions R.sub.a and R.sub.b. Excited modes may be mapped to
the regions of the discretized energy application zone, assuming
that N.sub.m different field patterns are excited in the zone.
Since the energy application zone has been discretized into N.sub.d
regions, the j.sup.th 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 may be proportional to the square of
the electrical field magnitude at that region. Therefore, for all
excited modes, the local intensities may be collectively written in
matrix form as:
[ I 11 , I 21 , I 31 , , I Nd 1 ; I 12 , I 22 , I 32 , , I N d 2 ;
I 1 Nm , I 2 Nm , I 3 Nm , , I NdNm ] ##EQU00007##
This matrix may be referred to as the I matrix.
[0124] In some instances, processor 30 may determine a targeted
spatial distribution of energy application. For example, the
distribution may be determined based on the spatial distribution of
absorption characteristics (also referred to herein as a "loss
profile" or "values indicative of energy absorbable in the object")
in cavity 20. As another example, the targeted distribution of
energy application may be provided by a user of the apparatus.
Additionally or alternatively, the targeted distribution of energy
application may be provided by other means, for example a readable
tag (e.g., an RF/bar-code associated with an object to be
processed). In some embodiments, both the targeted distribution of
energy application and the loss profile may be mapped to the
subregions of the discretized energy application zone. For example,
the targeted energy application may be written as a vector
W=W.sub.1, W.sub.2, W.sub.3, . . . , W.sub.Nd], and the loss
profile may be written as a vector .SIGMA.=[.sigma..sub.1,
.sigma..sub.2, .sigma..sub.3, . . . , .sigma..sub.Nd]. Therefore,
for each discretized region i, a linear equation can be
constructed:
.sigma..sub.i(I.sub.i1.tau..sub.1+I.sub.i2.tau..sub.2+I.sub.i3.tau..sub.-
3+ . . . +I.sub.iNm.tau..sub.Nm)=W.sub.i (4)
where .GAMMA.=[.tau..sub.1, .tau..sub.2, .tau..sub.3, . . . ,
.tau..sub.Nm], is the unknown weight vector, with .tau..sub.j being
the weight of the j.sup.th excited mode. Accordingly, in some
embodiments, the following equation may be constructed in matrix
form:
.GAMMA.P=W (5)
where P is a matrix (referred to as the P matrix) with
P.sub.ij=.sigma..sub.iI.sub.ij. The P matrix represents a modified
I matrix due to the presence of the object. In other words, P
matrix represents the applicable amount of energy to each region
via a particular mode, e.g., taking into account loss properties of
that region, e.g., its dielectric loss.
[0125] Consistent with some embodiments, the at least processor may
be further configured to solve the unknown weight vector .GAMMA.
mathematically. For example, .GAMMA. may be solved by inverting
matrix P and multiplied by vector W as follows:
.GAMMA.=WP.sup.-1 (6)
[0126] While inverting P may be the most efficient method for
solving the equation, other mathematical methods may be used,
including various stationary iterative methods such as the Jacobi
method, the Gauss-Seidel method and the Successive over-relaxation
method, etc, and various Krylov subspace methods, such as conjugate
gradient method (CG), generalized minimal residual method (GMRES)
and the biconjugate gradient method (BiCG), etc. Alternatively, the
equation may also be solved using optimization approaches, i.e.,
minimizing the residual |.GAMMA.P-W|. Iterative methods and
optimization methods may be particularly helpful when it is
difficult to directly invert P, or when inverting P may cause large
inaccuracies in the solution (e.g., when the equation system is
mathematically ill-conditioned, ill-posed, and/or singular).
[0127] Some embodiments of the invention may further include a
method for applying electromagnetic energy to an object. Such an
energy application may be accomplished, for example, through at
least one processor implementing a series of steps of process 900
such as the one set forth in the flow chart of FIG. 10A.
[0128] In accordance with some embodiments of the invention, the
method may involve placing the object in a degenerate energy
application zone in step 902. For example, object 50 (or a portion
thereof) may be placed in cavity 20. Cavity 20 may be a degenerate
cavities such as those illustrated in FIG. 2A-2D. Some embodiments
may omit this step, and are effective once the object is in the
energy application zone.
[0129] In accordance with some embodiments of the invention, the
method may further involve applying electromagnetic energy at a
determined frequency that excites a plurality of resonant modes in
the energy application zone, wherein the plurality of resonant
modes share a mode family, such as of the same transverse type. For
example, the at least one processor may regulate the source to
apply the electromagnetic energy at one or more determined
frequencies in step 904. By way of one example, the source may be
configured to apply energy at particular frequencies (or
wavelengths) that meet the modal condition in the zone (i.e., where
the applied frequency is less than about four times of the lowest
resonant frequency of the energy application zone). By way of
another example, the source may be configured to apply energy at
resonant frequencies of the degenerate energy application zone. Yet
in another example, the source may be configured to apply energy at
resonant frequencies determined, for example, by processor 30 based
on feedback received from the energy application zone via detector
40, for example.
[0130] In step 906, the at least one processor may regulate the
application of electromagnetic energy to excite a plurality of
resonant modes of the same mode family in the energy application
zone. For example, the source may include two or more synchronized
radiating elements configured to radiate electromagnetic energy at
a constant phase difference. The source may be regulated to vary
the phase differences in order to excite a plurality of resonant
modes at a single determined frequency. In some instances, the
phase differences may be chosen such that orthogonal modes are
excited in the degenerate energy application zone. For example, two
orthogonal resonant modes TE.sub.104 and TE.sub.401 may be excited
in the degenerate rectangular cavity, as shown in FIG. 5. The
plurality of resonant modes excited at the determined frequency may
be of the same transverse type, for example, either transverse
electric (TE) or transverse magnetic (TM). In some embodiments, one
or more modes (e.g., dominant modes) of the same mode family may be
selected to be excited while other modes of the same mode family
may be selected to be rejected.
[0131] FIG. 10B illustrates another exemplary process 1000 for
apply electromagnetic energy to an object in an energy application
zone, in accordance with some embodiments of the invention. In step
1002, an object may be placed in a degenerate energy application
zone, similar to step 902 as described above. Some embodiments may
omit this step, and are effective once the object is in the energy
application zone. In step 1004, the processor may determine a
frequency or a set of frequencies, at which the electromagnetic
energy may be applied to the degenerate energy application zone. In
some examples, the processor may first determine the lowest
resonant frequency associated with the degenerated energy
application zone, based on the geometry of the zone. Alternatively,
the processor may determine the lowest resonant frequency
associated with an object placed in the energy application zone.
The processor may then determine one or more frequencies according
to the modal condition, based on the lowest resonant frequency. In
other examples, the processor may determine the frequencies as
resonant frequencies of the degenerate energy application zone,
such as based on equations (1)-(3), referred to earlier. In some
configurations of the invention, resonant frequencies that satisfy
the modal condition may be determined and in others, the processor
may be configured to receive user selected frequencies. In some
embodiments, step 1004 may be performed once for a given energy
application zone, e.g., to a given cavity dimension.
[0132] In step 1006, the processor may determine a plurality of
phase differences to apply energy at each of the selected
frequencies. The phase differences may be determined, for example,
according to the shape of the degenerate energy application zone.
For example, in a degenerate cavity that has an octagonal
cross-section (e.g., cavity 62), .DELTA..phi.=0.degree.,
90.degree., 180.degree., and 270.degree. may be determined. In some
configurations of the invention, phase differences may be
determined such that energy applied at each phase difference may
excite resonant modes that are orthogonal to each other. For
example, in a rectangular cavity with a square cross-section (e.g.,
cavity 62), two phase differences that are 180.degree. apart from
each other may be determined to excite two orthogonal modes.
Alternatively, the processor may be configured to receive
user-selected phase differences.
[0133] In step 1008, the processor may determine a targeted energy
application. The targeted energy application may be a distribution
of energy applicable to the object. Targeted energy application may
be determined based on the energy absorption characteristics or
other properties associated with differing regions of the object.
Targeted energy application may include differing amounts of energy
at differing regions of the object. For example, if a dish contains
vegetables on one side and meat on another side, the targeted
energy application may be determined such that a larger amount of
energy is applied to the meat than that applied to the
vegetables.
[0134] Regions and differing amounts of energy may be specified by
a user as a function of known characteristics of the object. In
other embodiments, regions and differing amounts of energy may be
specified by other means, for example a readable tag (e.g., an
RF/bar-code associated with an object to be processed).
Alternatively or additionally, processor 30 may be configured to
sense the location of the object and energy absorption
characteristics within the object. Processor 30 may then determine
to which regions energy will be applied and the targeted amount of
energy that should be applied to each region. For example, in
connection with FIG. 1, processor 30 may determine the
characteristics of object 50 using feedback signals acquired via
radiating elements 18, and detected by detector 40. In some
instances, the targeted energy application may be discretized using
discretization strategies such as those shown in FIG. 9A-9C. For
example, the targeted energy application may be discretized into a
vector W.
[0135] In step 1010, the processor may determine weights of the
resonant modes to be excited in the zone, e.g., in order to achieve
the targeted energy application. Alternatively or additionally, the
processor may determine weights of the resonant modes in order to
obtain angular shift in the field pattern exited by the two modes
(as discussed above). Each combination of frequencies, as
determined in step 1004, and phase differences, as determined in
step 1006, may be referred to as an energy delivery scheme. Each
energy delivery scheme, when executed to regulate the source to
apply energy to the object, may excite a resonant mode or a
combination of resonant modes in the energy application zone. The
processor may predict the field distributions of these resonant
modes through testing, simulation, or analytical calculation. For
example, an I matrix may be constructed which records the various
resonant modes in a discretized manner. In some embodiments, the
weights, i.e., vector .GAMMA., may be calculated mathematically
based on linear algebra, such as equations (6) referred to
earlier.
[0136] In step 1012, the processor may regulate the source to apply
energy to the object according to the determined energy delivery
schemes (e.g., combinations of frequencies and phase differences),
and the respective weights. For example, the source may be
regulated as described in connection with FIGS. 6A and 6B.
[0137] Some embodiments of the invention may further include a
method for applying electromagnetic energy to an object. Such an
energy application may be accomplished, for example, through at
least one processor implementing a series of steps of process 1100
such as the one set forth in the flow chart of FIG. 11.
[0138] The method of FIG. 11 may include placing an object in an
energy application zone (step 1102). In some embodiments, the
energy application zone may be a degenerate energy application
zone. For example, object 50 (or a portion thereof) may be placed
in cavity 20. In some embodiments, cavity 20 may include a
degenerate cavity, for example those illustrated in FIGS. 2A-2D.
Some embodiments may omit this step, and are effective once the
object is in the energy application zone.
[0139] In some embodiments, the method may further involve
determining a dominant mode to be excited in the energy application
zone, in step 1104. For example, mode 802 (as shown in FIG. 8A) may
be the desired dominant mode to be excited. In some embodiments,
the modes and their respective weights may be determined as
discussed in reference to step 1010 of FIG. 10B.
[0140] In step 1106, the antenna placement/selection/orientation
strategy may be determined. The antenna placement may be
predetermined for a specific mode excitation or may be dynamically
determined during an energy application process. The desired
placement of antennas may also be achieved by selecting one or more
antennas in an antenna array, e.g., by disconnecting or connecting
one or more antennas. In some embodiments, disconnecting may be
obtained by not supplying EM energy to the antenna to be
disconnected. Processor 30 may determine the selection strategy
depending on a specific mode to be excited or rejected.
[0141] The method may further involve applying electromagnetic
energy at a predetermined frequency (step 1108) that excites one or
more modes in the energy application zone. For example, processor
30 may regulate the source to apply the electromagnetic energy at
one or more predetermined frequencies. In some embodiments, the
source may be configured to apply energy at resonant frequencies of
the degenerate energy application zone.
[0142] In step 1110, processor 30 may regulate the source to excite
a dominant mode (e.g., the dominant mode determined in step 1104)
in the energy application zone. For example, by supplying
electromagnetic energy through a specific antenna or antenna
combination at particular locations, the dominant mode may be
excited and one or more other modes may be rejected.
[0143] FIG. 12 illustrates another exemplary process 1200 for
applying electromagnetic energy to an object in an energy
application zone in accordance with some embodiments of the
invention. In step 1202, an object may be placed in an energy
application zone, similar to step 1102, as described above. The
energy application zone may be a degenerate energy application
zone. Some embodiments may omit this step, and are effective once
the object is in the energy application zone. In step 1204,
processor 30 may determine a frequency or a set of frequencies at
which electromagnetic energy may be applied to the energy
application zone. In some embodiments, processor 30 may first
determine the lowest resonant frequency associated with the energy
application zone, based on the geometry of the zone. Processor 30
may then determine one or more frequencies based on the lowest
resonant frequency. In other embodiments, processor 30 may
determine the frequencies as resonant frequencies of the degenerate
energy application zone based on equations (1)-(3), for example.
Processor 30 may also determine frequencies based on user input.
Additionally or alternatively, processor 30 may determine
frequencies based on other inputs, e.g., from a tag (e.g., a
barcode) associated with the object. In some embodiments, step 1204
may be performed once for a given energy application zone, e.g., to
a given cavity dimension.
[0144] In step 1206, processor 30 may determine one or more antenna
placement/selection/orientation strategies at each selected
frequency. For example, processor 30 may determine a desired
dominant mode corresponding to each of the selected frequencies and
determine appropriate antenna locations to excite the desired
dominant modes and/or to reject one or more undesired modes.
[0145] In step 1208, processor 30 may determine a targeted energy
delivery or a targeted field pattern corresponding to a desired
energy application or delivery profile in the energy application
zone. The targeted energy delivery profile may include a
distribution of energy applicable to the object. In some
embodiments, the targeted energy delivery profile may be determined
based on the energy absorption characteristics or other properties
associated with differing regions of the object. In some
embodiments, the targeted energy delivery profile may include
differing amounts of energy at differing regions of the object. For
example, if a dish includes vegetables on one side and meat on
another side, the targeted energy delivery profile may be
determined such that a larger amount of energy is applied to the
meat than to the vegetables.
[0146] A desired energy delivery profile can be achieved by
manipulating one or more MSEs to generate one or more targeted or
desired field patterns through which a desired amount of energy may
be applied to specific locations in the cavity one by one. That is,
each successive field pattern application may apply a certain
amount of energy to certain locations within the energy application
zone. After a series of field pattern applications, the overall
/net/time integrated amount of energy applied to an object or
region within the energy application zone may correspond to the
desired energy delivery profile.
[0147] In some embodiments, regions within the energy application
zone and specific amounts of energy to be applied to those regions
may be specified by a user as a function of known characteristics
of the object. Alternatively or additionally, processor 30 may be
configured to sense the location of the object and energy
absorption characteristics within the object. Processor 30 may then
determine the regions to which energy will be applied and the
targeted amount of energy that should be applied to each region.
Processor 30 may then compile an energy delivery profile to provide
a certain amount of energy to the volume that corresponds to object
50 (or even to various portions of object 50) and another amount of
energy to the volume surrounding object 50. Processor 30 would then
determine the combination of field patterns to apply in order to
provide the desired energy delivery profile.
[0148] In some embodiments, the targeted energy delivery profile
may be discretized according to a discretization of cavity 20,
using discretization strategies such as those shown in FIG. 9A-9C.
For example, the targeted energy delivery profile may be
discretized into a vector W.
[0149] In step 1210, processor 30 may determine weights of the
modes to be excited in the zone, in order to achieve the targeted
energy delivery profile or targeted field patterns. Each
combination of frequencies, as determined in step 1204, and
optionally phase differences, may be referred to as an energy
delivery scheme. Each energy delivery scheme, when executed to
regulate the source to apply energy to the object, may excite a
mode or a combination of modes in the energy application zone.
Exciting and/or rejecting one or more modes may be achieved by
antenna placement/selection/orientation strategies, as determined
in step 1206. Processor 30 may predict the field distributions of
these modes through testing, simulation, or analytical calculation.
For example, an I matrix may be constructed which records the
various modes in a discretized manner. In some embodiments, the
weights, i.e., vector F, may be calculated mathematically based on
linear algebra using, e.g., equation (6).
[0150] In step 1212, processor 30 may regulate the source to apply
energy to the object according to the determined energy delivery
schemes (e.g., combinations of frequencies and antenna
placement/selection strategies), and the respective weights. For
example, the source may be regulated as described in connection
with FIGS. 6A and 6B.
[0151] The utilization of antenna location to excite or reject
modes may significantly enhance the noise immunity and resolution
capability of the spatially controlled energy delivery technique.
By using one or more antennas placed in specific positions relative
to the desired or undesired modes, an additional degree of freedom
may be available to control energy delivery.
[0152] Various examples of the invention are described herein in
connection with energy application performed in cavity 20. 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.
[0153] 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.
[0154] 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.
* * * * *