U.S. patent application number 10/459048 was filed with the patent office on 2003-10-23 for apparatus for energizing a remote station and related method.
Invention is credited to Emahizer, Chad, Gorodetsky, Dmitry, Mats, Leonid, Mi, Minhong, Mickle, Marlin, Neureuter, Lorenz, Taylor, Carl.
Application Number | 20030199778 10/459048 |
Document ID | / |
Family ID | 25491180 |
Filed Date | 2003-10-23 |
United States Patent
Application |
20030199778 |
Kind Code |
A1 |
Mickle, Marlin ; et
al. |
October 23, 2003 |
Apparatus for energizing a remote station and related method
Abstract
Apparatus for remote interaction with an object of interest
includes a remote station for obtaining information from the object
of interest, a base station for transmitting energy in space to and
communicating with the remote station and the remote station having
conversion means for energizing the remote station responsive to
receipt of the transmitted energy. The energy may be of any
suitable type including RF power, light, acoustic, magnetic energy
or other form of space transmitted or "radiant" energy. The remote
station does not have to contain a source of stored energy or a
wired connection to a source of energy. The remote station receives
the energy transmission and data transmission from the base station
and transmits data to the base station. Microprocessor controllers
may be provided for the base station and the remote station The
remote station may receive information from sensors and through one
or more transponders sequentially communicate information to the
base station An associated method is provided. In other embodiments
which are suited for use in miniaturized electronic chip systems,
power enhancement and increased effective antenna size are
provided.
Inventors: |
Mickle, Marlin; (Pittsburgh,
PA) ; Gorodetsky, Dmitry; (Pittsburgh, PA) ;
Mats, Leonid; (Pittsburgh, PA) ; Neureuter,
Lorenz; (Lancaster, PA) ; Mi, Minhong;
(Pittsburgh, PA) ; Taylor, Carl; (Pittsburgh,
PA) ; Emahizer, Chad; (Pittsburgh, PA) |
Correspondence
Address: |
Arnold B. Silverman
Eckert Seamans Cherin & Mellott, LLC
44th Floor
600 Grant Street
Pittsburgh
PA
15219
US
|
Family ID: |
25491180 |
Appl. No.: |
10/459048 |
Filed: |
June 11, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10459048 |
Jun 11, 2003 |
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09951032 |
Sep 10, 2001 |
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6615074 |
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09951032 |
Sep 10, 2001 |
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09218322 |
Dec 22, 1998 |
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6289237 |
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Current U.S.
Class: |
600/509 |
Current CPC
Class: |
A61B 5/0031 20130101;
G06K 19/0723 20130101; G06K 19/07779 20130101; A61B 5/002 20130101;
H02J 50/20 20160201; Y10S 128/903 20130101; H02J 50/30 20160201;
A61B 2560/0219 20130101; G06K 19/07775 20130101; G06K 19/0701
20130101; G06K 7/0008 20130101; H02J 50/80 20160201 |
Class at
Publication: |
600/509 |
International
Class: |
A61B 005/04 |
Claims
In the claims:
1. Apparatus for remote interaction with an object of interest
comprising a remote station for obtaining information from said
object of interest, a base station for transmitting energy in space
to and communicating with said remote station, said remote station
having conversion means for energizing said remote station
responsive to receipt of said transmitted energy, said remote
station not having a power storage device for energizing said
remote station after termination of base station energy
transmission to said remote station, first antenna means
operatively associated with said base station for transmitting
signals to and receiving signals from said remote station, second
antenna means operatively associated with said remote station for
receiving signals from said first antenna means and transmitting
signals to said first antenna means, and said second antenna means
having at least one antenna having an effective antenna area
greater than its physical area.
2. The apparatus of claim 1 including said remote station having an
electronic chip on which said second antenna means is formed.
3. The apparatus of claim 2 including, said second antenna means
including a plurality of said second antennas.
4. The apparatus of claim 3 including at least two of said second
antennas structured to receive different frequencies.
5. The apparatus of claim 4 including said first antenna means
having a separate antenna for transmitting at each said
frequency.
6. The apparatus of claim 2 including said base antenna having
means for transmitting said energy as RF power.
7. The apparatus of claim 6 including said remote station having at
least one voltage doubler.
8. The apparatus of claim 7 including said remote station having at
least two said voltage doublers in series.
9. The apparatus of claim 7 including each said voltage doubler
having at least one capacitor electrically interposed between said
second antenna means and a diode.
10. The apparatus of claim 3 including, said second antennas formed
on said electronic chip.
11. The apparatus of claim 10 including an LC link circuit formed
in said second antenna means.
12. The apparatus of claim 2 including said remote station is an
RFID tag.
13. The apparatus of claim 1 including said effective antenna area
is at least 300 times the antenna's physical area.
14. The apparatus of claim 2 including said chip is a devise
selected from the group consisting of a CMOS device and a MEMS
device.
15. The apparatus of claim 2 including a power supply for
energizing said base station.
16. The apparatus of claim 2 including first controller means for
controlling operation of said base station.
17. The apparatus of claim 16 including said first controller means
having microprocessor means.
18. The apparatus of claim 1 including said remote station having
means for converting said transmitted energy into DC power for
energizing said remote station.
19. The apparatus of claim 18 including said remote station having
second controller means for processing information received from
said base station and for transmitting information to said base
station.
20. The apparatus of claim 19 including said second controller
means having means for receiving information from sensor means
monitoring said object of interest.
21. The apparatus of claim 19 including said object of interest
being a patient.
22. The apparatus of claim 21 including said sensor means having
apparatus to monitor a body condition or body function of said
patient.
23. The apparatus of claim 1 including said remote station not
having a power storage device physically secured thereto.
24. The apparatus of claim 1 including said base station and said
remote station having no wired connection therebetween.
25. The apparatus of claim 18 including said base station
transmitting both power signals and data signals to said remote
station.
26. The apparatus of claim 2 including said remote station having
converter means for converting said RF power into DC or AC
power.
27 The apparatus of claim 1 including said remote station being
sealed within a resinous plastic material.
28. A method for remote interaction with an object of interest
comprising providing a remote station and a base station
operatively associated therewith, transmitting energy in space from
said base station to said remote station, converting said energy
received by said remote station into electrical power to energize
said remote station, effecting said energy received by said remote
station into electrical power to energize said remote station,
effecting said remote interaction without requiring such remote
station to have a power storage device secured thereto for
energizing said remote station after termination of said base
station transmission and said energy conversion, employing antenna
means for communication of said electrical power in space between
said base station and said remote station, said antenna means
having first antenna means operatively associated with said base
station and second antenna means operatively associated with said
remote station, and said second antenna means having at least one
antenna having an effective antenna area greater than the physical
area.
29. The method of claim 28 including said remote station employing
an electronic chip on which said second antenna means is
formed.
30. The method of claim 29 including employing a plurality of
second antennas as said second antenna means.
31. The method of claim 31 including at least two of said second
antennas structured to receive different frequencies.
32. The method of claim 31 including said first antenna means
having antennas for transmitting at each said frequency.
33. The method of claim 29 including transmitting said energy from
said base station as RF power.
34. The method of claim 33 including employing in said remote
station at least one voltage doubler.
35. the method of claim 34 including employing in said remote
station at least two said voltage doublers in series.
36. The method of claim 34 including providing in each said voltage
doubler at least one capacitor electronically interposed between
said second antenna means and a diode.
37. The method of claim 30 including said second antennas formed on
said electronic chip.
38. The method of claim 37 including providing an LC link circuit
in said second antenna.
39. The method of claim 29 including employing as said remote
station an RFID tag.
40. The method of claim 28 including said effective antenna area is
at least 300 times the antennas physical area.
41. The apparatus of claim 29 including employing as said chip a
device selected from type group consisting of a CMOS device and a
MEMS device.
42. The method of claim 28 including transmitting said energy as RF
power.
43. The method of claim 28 including energizing said base station
by a power supply.
44. The method of claim 43 including converting said transmittal
energy to DC power at said remote station.
45. The method of claim 28 including employing said method on an
object of interest which is a patient.
46. The method of claim 28 including sealing said remote station
within a resinous plastic material.
47. The method of claim 45 including employing said method to
monitor a body condition or body function of said patient.
48. The method of claim 28 including transmitting both power
signals and data signals from said base station to said remote
station.
49. The method of claim 48 including transmitting data signals from
said remote station to said base station.
50. The method of claim 36 including employing a said remote
station not having a power storage device.
51. The method of claim 50 including employing first microprocessor
means to control operation of said base station.
52. The method of claim 51 including employing second
microprocessor means to control said remote station.
53. The method of claim 45 including positioning said remote
station within 20 feet of said base station.
54. The method of claim 38 including employing said method to
confirm identification of an object of interest.
55. The method of claim 54 including employing said method in a
security system.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application is a continuation-in-part of U.S.
Application Ser. No. 09/218,322 filed Dec. 22, 1998, now U.S. Pat.
No. 6,289,237.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to apparatus and an associated method
for energizing a remote station through energy transmitted in space
and, more specifically, it relates to such a system wherein data
with respect to an object of interest may be obtained by the remote
station and transmitted to the base station upon interrogation by
the base station.
[0004] 2. Description of the Prior Art
[0005] It has long been known in various applications to monitor
conditions of a physical system or a patient and provide
information in the nature of real-time readouts of certain
conditions. Such systems typically have been connected by a
suitable wire to a source of electricity at the desired voltage
such as line current or batteries.
[0006] It has also been known to provide such systems in the
medical environment in respect of monitoring characteristics such
as patient respiration, heart beat, electrocardiograms and
temperature, for example. See, generally, U.S. Pat. Nos. 4,129,125;
4,308,870; 4,443,730; 4,889,131; and 5,335,551.
[0007] It has also been known in the medical environment to monitor
physiological parameters by employing sensors, a battery powered
system, and digital processing means to effect comparison between
the measured conditions and stored values and displaying the
results. See U.S. Pat. No. 4,356,825.
[0008] U.S. Pat. Nos. 5,230,342 and 5,586,555 disclose blood
pressure monitors employing a pressurizable pressure transducing
bladder with particular emphasis on measuring blood pressure in a
supraorbital artery.
[0009] U.S. Pat. No. 4,576,179 discloses the use of a chest motion
transducer and associated heart rate monitoring apparatus.
Cooperating electronics are provided. Alarm means may be triggered
under appropriate conditions of the individual being monitored or
an indication that the battery voltage has fallen below a preset
level. There is an allusion to making provision for short range
radio transmission of the signals to remote monitoring stations.
See also U.S. Pat. No. 5,022,402.
[0010] U.S. Pat. No. 4,494,553 discloses a battery powered
respiratory and cardiac monitor wherein a pair of inductance coils
are employed along with VHF/FM transmission of signals.
[0011] It has been known to suggest the use of a wireless
communication link between a base station and transponders in a
radio frequency identification system employing modulated
back-scattered waves separate attachment of an antenna to a tag
integrated current is disclosed. See Rao, an overview of Bulk
Scattered Radio Frequency Identification System (RFID) I EEE
(1999).
[0012] It has been suggested to employ a silicon chip in a
transponder having a change pump on voltage doubler current.
Hornby, RFID Solutions for the express parcel and airline baggage
industry, Texas Instruments, Limited (Oct. 7, 1999).
[0013] In spite of the foregoing known systems, there remains a
need for a remote unit usable in various environments and at
various distances from the base station which remote unit will be
adapted to be remotely energized so as not to require hard wired
systems or batteries on the remote unit. There is also lacking such
systems wherein the remote unit may be miniaturized so as to have
numerous potential uses.
SUMMARY OF THE INVENTION
[0014] The present invention has met the above-described needs. In
the present invention, apparatus for remote interaction with an
object of interest includes a remote station for obtaining
information from the object of interest and a base station for
transmitting energy in space to the remote station and
communicating with the remote station. The remote station has
conversion means for energizing the remote station by employing the
transmitted energy. The base station may transmit the energy as RF
power, light, acoustic, magnetic, or in other suitable forms of
space transmitted or "radiant" energy.
[0015] A power supply is provided for energizing the base station
with first antenna means being provided on the base station and
second antenna means being provided on the remote station. Sensor
means or other information providing means permits the remote
station when energized by the base station to transmit information
to the base station regarding the object of interest and certain
conditions of the remote station. This may be done in real-time.
The remote station may be provided with a plurality of transponders
each of which may be interrogated by the base station sequentially
to provide separate informational packets.
[0016] A method of the present invention provides for remote
interaction with an object of interest, including providing the
remote station and a base station operatively associated therewith,
with energy being transmitted in space from the base station to the
remote station, and the energy so transmitted being converted by
the remote station into electrical power to energize the remote
station.
[0017] The remote station may be provided with a plurality of
transponders each of which will be a source of different
information from the other.
[0018] The system eliminates the need for batteries on the remote
station or the use of hard wired systems.
[0019] The invention also provides systems which employ voltage or
power enhancing units on the remote station. When employed on
electronic chips, antennas having a greater effective area than
physical area may be employed advantageously.
[0020] The system is adapted for use on system on a chip (SOC)
miniaturized unit.
[0021] It is object of the present invention to provide a remote
station which is adapted to provide information to a base station
when interrogation by the base station is initiated.
[0022] It is another object of the present invention to provide
such a system wherein the remote station is not required to contain
an energy storage device, such as a battery, or to be part of a
hard wired or printed circuit system.
[0023] It is a further object of the present invention to provide
such a system wherein energy transmitted in space, such as RF power
or light, will be converted into DC power or AC power on the remote
station to operate the remote station.
[0024] It is a further object of the present invention to provide
such a system wherein RF power may be employed to initiate
operation of the remote station regardless of whether light is
present.
[0025] It is a further object of the present invention to provide
such a remote station which will transmit dynamic real-time
measurements to a base station.
[0026] It is another object of the present invention to provide
such a system wherein the remote station may be miniaturized and
does not require frequent maintenance.
[0027] It is another object of the present invention to provide
such systems wherein enhanced energy harvesting on a remote station
is provided.
[0028] It is a further object of the present invention to provide
such a system wherein use on miniaturized Systems on a Chip (SOC)
is facilitated.
[0029] It is yet another object of the present invention to provide
such systems wherein the effective antenna area exceeds the
physical antenna area.
[0030] It is a further object of the present invention to provide
such systems which may be employed effectively in Radio Frequency
IDentification (RFID) devices.
[0031] It is a further object of the present invention to provide
such a system wherein the remote station may have a plurality of
passive intelligent transponders.
[0032] These and other objects of the invention will be more fully
understood from the following description of the invention on
reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is a schematic illustration of a form of the present
invention showing a base station, a remote station, and a plurality
of information providing sensors.
[0034] FIG. 2 is a schematic illustration of a base station usable
in the present invention.
[0035] FIG. 3 is a schematic illustration of a remote station and
associated sensor usable in the present invention.
[0036] FIG. 4 is a schematic illustration of an embodiment of the
present invention employing a plurality of transponders in the
remote station.
[0037] FIG. 5 is a schematic illustration of the base station
interrogator and the corresponding time sequence of interrogating a
plurality of transponders.
[0038] FIG. 6 is a schematic view of a plurality of
electrocardiogram sensors and associated transponders, as well as
the base station, which is in space communication therewith.
[0039] FIG. 7 is a schematic illustration of a base station in
space communication with a sensor and remote station combination
secured to an individual's hand to provide monitoring of the
patient.
[0040] FIG. 8 is an example of a circuit of a voltage doubler on
change pump of an embodiment of the invention.
[0041] FIG. 9 is an example of a series of voltage doublers of the
present invention.
[0042] FIG. 10 is a schematic illustration of a chip on a remote
station and related energy transfer.
[0043] FIG. 11 is a plot of power as a function of antenna
volume
[0044] FIGS. 12(a) and 12(b) respectively show a conventional or
balanced voltage doubler circuit and a cascade form of voltage
doubler circuit.
[0045] FIG. 13 illustrates a detection circuit employing a Schottky
diode.
[0046] FIG. 14 is a voltage doubler equivalent circuit.
[0047] FIG. 15 is a plan view of an antenna layout for use on an
electronic microchip.
[0048] FIG. 16 is a plan view of a fabricated die chip containing
an on-board antenna of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0049] As employed herein, the term "object of interest" means any
animate or inanimate item from which information is to be obtained
by the remote station.
[0050] As employed herein, the term "in space" means that energy or
signals are being transmitted through the air or similar medium
regardless of whether the transmission is within or partially
within an enclosure, as contrasted with transmission of electrical
energy by a hard wired or printed circuit boards.
[0051] As employed herein, the term "patient" means members of the
animal kingdom including humans.
[0052] Referring to FIG. 1, there is shown a schematic illustration
of the apparatus of the present invention which facilitates remote
measurement and/or sensing. A base station 2 is within
communication distance D of a remote station 4. In a manner to be
described hereinafter, the base station 2 transmits energy which
may be RF power, light, acoustic, magnetic or other suitable forms
of space transmitted or "radiant" energy, for example, and is
indicated generally by the dashed line 8 to remote station 4.
Within the remote station 4, the received energy is converted into
DC power which serves to operate the remote station 4. In the form
illustrated, an object of interest 12 has a plurality of sensors
16, 18, 20 operatively associated therewith, and delivering sensor
readings over lines 24, 26, 28, respectively, to the remote station
4 which, in turn, in a manner to be described herein, transmits
data through space as indicated by double-headed arrow 30 to base
station 2. The power delivered to remote station 4 may also
energize sensors 16, 18, 20 through wires 24, 26, 28. The RF energy
may also be employed to energize sensors 16, 18, 20 without wires
24, 26, 28. The distance D will vary in accordance with design
parameters of the system and may, depending upon the application,
be a few millimeters, several feet, or several light years. Dashed
arrow 30 also shows data being transmitted from base station 2 to
remote station 4.
[0053] One of the advantages of the present invention is that the
source of power for the remote station 4 is the base station 2 and,
therefore, there is no need for hard wiring or printed circuit
physical connections with remote station 4. There is also no need
for remote station 4 to carry an electrical storage device such as
a battery. As a result, activation and powering of the remote
station 4 will be achieved through activation of the base station
2. As a result, there will be no need for periodic maintenance on
the remote station 4 in order to check battery strength and replace
the battery or other power source. This also facilitates the remote
station being encapsulated within a suitable protective material,
such as a resinous plastic. Homopolymers (including thermoplastic
polymers), elastomers and silicon dioxide, for example, are
suitable materials for such purposes. Further, this facilitates
miniaturization of the remote station and placing the remote
station in functionally desirable locations which need not be
readily accessible. The remote station, for example, could be
implanted in a patient.
[0054] It will be appreciated that the remote station 4 can be
interrogated by the base station 2, for example, to provide through
the remote station 4 a reading of an electronic or mechanical
sensor, such as 16, 18, 20 which is operatively associated with the
remote station 4.
[0055] Referring to FIG. 2 in greater detail, there is shown a
schematic diagram of a form of base station 2 usable in the present
invention. The base station 2 is, in the form shown, energized by a
120 VAC utility power source 40, although other power sources, such
as batteries, alternators and inverters, for example, may be
employed, if desired. The power source is in communication with and
supplies power to power supply 42 which, in turn, emits DC power at
the desired level for operation of the base station 2. If desired,
AC power could be employed to energize the remote station 4. A
microcontroller 50, which may take the form of a microprocessor or
intelligent microchip, which receives input from an analog to
digital converter, a transducer employing an electronic means (such
as sound, light, temperature, moisture or the like) or a program in
memory, hard wired logic, an Application Specific Integrated
Circuit (ASCI), from a wireless link, a satellite or cable, as in
TV, for example.
[0056] A computer 52, which may be any sort of personal computer or
modem if the unit is on a network, through serial interface 54
provides two-way communication with microcontroller 50. The
datalogger memory 58 is in two-way communication with the
microcontroller 50 and functions to provide the microcontroller 50
with any desired comparison standards, basic data, and calibration
information. The keypad and display 60 is in two-way communication
with microcontroller 50 and provides for keypad input into the
microcontroller 50 and display of information obtained by the base
station 2.
[0057] The base station 2 has an ISM (Industrial, Scientific,
Medical) band antenna 70 which transmits RF signals emitted by the
ISM power transmitter 72 responsive to signals received from
microcontroller 50.
[0058] This serves to transmit the RF power in space to the remote
station 4. In the event that light were to be the transmitted
energy. The transmitted energy source may be the sun, room light,
(incandescent or fluorescent) or laser light, for example. This
one-way transmission is shown by the dashed arrow line 8 in FIG.
1.
[0059] The base station 2 has data transmitter 74 which has data
transmitted by data band antenna 76 to the remote station 4. The
data transmitted may be control, configuration, identification and
processed versions of such data. Microcontroller 50 controls data
transmitter 74. Data receiver 80 receives data from the remote
station 4 through data band antenna 76 and introduces the same into
microcontroller 50.
[0060] It will be appreciated that in this manner the power
supplied to the base station 2 not only serves to operate the base
station 2, but provides the means for transmitting energy in space
to remote station 4 to operate the same and transmit data to and
receive data from remote station 4.
[0061] Referring to FIG. 3 in greater detail, there is shown a form
of remote station 4 which, in the form shown, cooperates with a
measurement sensor 90 which senses an object of interest, through a
sensor interface 92, interacts with microcontroller 94 which
preferably has a non-volatile memory and through an analog to
digital converter, direct digital measurement device or other
sampling device, provides for digital input into the
microcontroller 94. This microcontroller 94 controls operation of
the remote station 4. A dual band resonant antenna 100 receives
both the power transmissions and data transmissions from the base
station 2. The power transmission is received in the converter 102,
which converts the RF power to DC power, which serves to energize
the remote station 4. In the alternative, a device for converting
the RF power into AC power could be employed to power the remote
station 4. This substitutes for the need to provide a hard wired
system or to have a power storage device on the remote station. The
data received from the base station 2 is delivered by the antenna
100 to data receiver 108 which, in turn, delivers the same to the
microcontroller 94. This data initiates a cycle of operation of the
remote station 4 and serves as the interrogation means. The data
could also be data for controlling other functions such as ON/OFF
switching, calibration, remote control or configuration
control.
[0062] Data processed by the microcontroller 94 and received in the
form shown from measurement sensor 90 is transmitted by data
transmitter 110 through a double band resonant antenna 100 to base
station 2 as indicated by the double-headed dashed arrow 30 in FIG.
1. It will be appreciated, therefore, that positioning of the
remote station 4 with respect to the base station 2 will be heavily
dependent on the application intended and will involve design of
the system to provide adequate RF power and sufficient antenna
capability to maintain the desired level of power for the remote
station 4 and efficient communication of data between the remote
station 4 and base station 2.
[0063] Numerous end use applications will be apparent to those
skilled in the art. For example, in many applications the distance
D ill FIG. 1 will be less than 20 feet. In medical applications
such as, for example, where the sensors 16, 18, 20 might be EKG
sensors, a plurality of remote stations each having a sensor built
into it or operatively associated therewith may be applied to the
object of interest 12 which, in that case, would be a patient, such
that no wires need be provided. In the alternative, in the form
shown in FIG. 1, no wires need to be provided between the remote
station 4 and the base station 2. Many other types of medical
applications wherein sensors or information gathering apparatus is
employed, such as cardiac monitors, brain monitors, pulse monitors,
blood pressure monitors, oxygen monitors, as well as monitors which
monitor the performance of patient support equipment, such as
ventilators, intravenous delivery systems, renal dialysis machines,
oxygen supplementing devices and heart bypass devices may
beneficially employ the invention. Depending upon the end use, it
might also be desirable to have an alarm triggered in addition to
the visual presentation or computer storage or hard copy
presentation of information obtained from the system.
[0064] In an alternate embodiment of the invention, uses in
manufacturing processes so as to monitor equipment performance or
product manufacture may advantageously find uses for the present
invention. The system may also be employed for noise monitoring of
equipment and providing communication for Computer Numeric Control
(CNC), for example.
[0065] In some instances, where identification is desired, such as
for security purposes, the remote unit might provide information to
enable the base unit to confirm that an article or an individual is
as represented.
[0066] In retail stores, products may have remote stations of the
present invention secured thereto which at the cash register will
deliver information to a base station thereby eliminating the need
for bar codes and the like. This could be employed to total the
charges for a specific customer as well inventory control and keep
records of customer preferences.
[0067] There also may be applications involving outer space wherein
the remote station provides information to an earth mounted base
station.
[0068] Other uses will be apparent to those skilled in the art. A
key feature is that the present system obviates the need to depend
on batteries and hard wired systems as a source of energizing a
remote station. Both power delivery to the remote station and
two-way data transmission between the base station and the remote
station are facilitated.
[0069] Referring to FIG. 4, there is shown a system wherein the
base station 120 and its associated microprocessor 122, which may
be a personal computer or modem, cooperates with antenna 124 to
provide for power delivery and two-way data communication with the
remote station 130. As shown in FIG. 4, this embodiment
contemplates the use of a plurality of transponders, such as 140,
142 which, in the form shown, total 16 in number It is contemplated
in this embodiment that each transponder will be operatively
associated with a sensor receiving one type of information and will
facilitate the base station sequentially interrogating each
transponder 140, 142 to receive real-time information therefrom
with a suitable time interval between each interrogation. Depending
on the application, in lieu of sensor information, the
interrogation may be to determine product codes or personal
identification of an individual.
[0070] Referring to FIG. 5 there is shown a suitable communications
protocol for use in the system of the present invention. The base
station 120 provides means for identifying the specific transponder
which is the source of the data being received and does so by
polling each transponder in sequence. The power signal sent by the
base station 120 may be employed as a means of providing a signal
to identify the start of the polling operation. Depending upon the
system address of the transponder, the data sent back will be sent
at a unique time. The ISM power interrogator 148 after an initial
delay period indicated generally by the reference number 149, each
transponder such as transponder 140 which will be interrogated
between times t.sub.1 and t.sub.2 and transponder 142 will be
interrogated between times t.sub.2 and t.sub.3. In this manner, the
discrete data packets received from the various transponders will
be provided sequentially with identification as to source. It is
preferred that a short dead time be provided between successive
transponder data packets in order to avoid collisions. The data
packets from the transponder may contain both sensor data and
status information. The sensor data will be the information
provided from the sensor through the system described hereinbefore.
The status information may include information such as the specific
transponder address identification, the internal DC bus voltage
and, if desired, discrete digital inputs. The base interrogator
will use the status information to verify the integrity of the
communication links and have the capability of altering the ISM
power if necessary.
[0071] Referring to FIG. 6, there is shown the outline of a patient
180 with a plurality of sensors and associated remote stations 190,
198, 204, with a symbolic representation of the space
communications as by RF signals 192, 200, 206 with the base station
184. In the R/X and X/R representations, the "R" indicates
receiving capability and the "X" indicates transmitting
capability.
[0072] Referring to FIG. 7, there is shown a schematic of a base
station 220 in space contact as by transmission of RF power shown
schematically at 230 to hand 222 which contains a sensor for
medical information such as pulse, blood pressure or temperature,
for example, operatively associated with the remote station
224.
EXAMPLE
[0073] In order to provide additional insight into the invention an
example will be provided.
[0074] A system of the type discussed in connection with FIGS. 1-3
may have a base interrogator unit or base station powered by
standard commercial 120 VAC utility or equivalent UPS. If the ISM
power is limited to 16 watts, then the total input power need not
exceed 20 watts. The ISM power transmitter 72 will preferably be
capable of outputting less than 1 watt or 1, 2, 4, 8, or 16 watts
of RF energy as determined by the microcontroller 50. This will
facilitate flexibility in respect of power for the program
instructions and set-up parameters. An asynchronous serial port
serves to connect the base station to the personal computer or
modem 52 by way of an RS232 type interface. A suitable
microcontroller 50 would be that marketed under the trade
designation "Intel 8051. "The keypad and display 60 permits users
to monitor measurement data and status from the system's
transponders. The keypad switches allow the user to step through a
menu driven display at various parameters. The keypad may also have
a password function to provide for security for restricted set up
of the system parameters.
[0075] The datalogger memory 58 permits the base station to have
the capability to pole multiple transponder devices in a typical
system configuration. A non-volatile memory facilitates logging
tune stamped transponder data in a file storage buffer which can be
used for data trending and uploaded by way of the serial interface
54. The non-volatile memory can be interfaced directly to the
microcontroller bus as SRAM module with a real-time clock. The
serial interface 54 allows connection either to a personal computer
or modem. Software, firmware, ASCI or wired logic resident in the
base station may include drivers for an ASCII station communication
protocol in order that the system can be configured by way of a PC
GUI menu system. The modem drivers will allow the base station to
stand alone and accept, as well as generate telephone
communications. The system firmware, non-volatile parameters and
datalogger memory are all accessible by way of the serial interface
54. The power supply 42 serves to convert the 120 VAC utility input
to low voltage DC to operate the control circuitry and RF
transmitter. The power supply should output a well regulated 5 VDC
(.+-.5%) for the logic circuits and a 12-24 VDC output to operate
the ISM power transmitter 72.
[0076] The remote station, as shown in FIG. 3, can be miniaturized
and preferably has maximum dimensions of about 5 inches by 2 inches
by 1 inch. The size may be reduced to the point where the remote
station may implanted into the human body. One limiting factor in
miniaturization is the antenna and as a result, it is preferred to
raise the operating frequency as high as practical. The
transponders may be about 0.5 inch in diameter and have a thickness
of about 0.03215 inch.
[0077] The remote station contains no power storage device as all
power is derived from the base station. Experimental results have
indicated that at least 20 mw of usable DC power can be obtained in
the remote station through the system described herein. The
transponder has a direct-coupled analog input for interfacing with
the measurement sensors. The analog to digital converter may have
an input range of 0-2.5 VDC. The ISM E-field at the remote station
may be approximately 3 V/m with the specific field depending upon
the effective antenna gain. With respect to the telemetry link,
data is returned by way of a communication link that operates
outside the ISM band. The base station data receiver may have a
sensitivity on the order of 0.5 uv/m. The remote station datalink
RF output will generally be less than 10 mw which facilitates
reliable communications over the required range. The converter
serves to transform the ISM RF power into DC bus voltage on the
order of 3 VDC. The RF energy coupled into the remote station
antenna is an AC voltage varying at the carrier frequency. The RF
to DC converter circuit rectifies and filters the RF AC voltage
into a usable DC form. The rectifier and filter circuit preferably
has an impedance several times lower than the overall antenna with
the antenna having a characteristic impedance on the order of 377
ohms and the rectifier circuit having an impedance less than 10
ohms. A suitable microcontroller for use in the remote station is
that sold under the trade designation Microchip PIC.
[0078] In a further refinement of the invention, features which are
adapted for use in, but not limited to, use in miniaturized
electronics and the integration of Systems on a Chip (SOC) will be
considered. In such a system inherent problems regarding supplying
adequate power and efficiency of communication between a base
station and a remote station occur. An example of such systems is
the Radio Frequency IDentification (RFID) where the device is
passive with the power being supplied from a remote source which is
a Radio Frequency (RF) radiator. The remote station converts the
radiator RF power to DC current to drive commercially available
electronics of a single chip system, for example. With increased
miniaturization, the physical area of any on-board antenna or
energy capturing device decreases. The present invention has
structures for providing enhanced power and antennas with an
effective size greater than their physical size which may
advantageously be employed.
[0079] While for simplicity of disclosure, reference will be made
herein to the RFID device, it will be appreciated that these
features of the present invention may be employed advantageously in
other systems.
[0080] An RFID device may provide a simple electronic replacement
for the conventional printed bar code used in many industrial and
commercial environments including customer checkout in retail
stores and related inventory control. As cost is a very important
item due to the bar code system being relatively inexpensive on a
per item basis, the RFID tags employed on the articles as a chip
attached to an antenna that is attached to a product container or
product, must be competitive economically. Employing an antenna of
this embodiment of the invention as an integral part CMOS
(Complementary Metal Oxide Semiconductor) contributes to reduced
cost of manufacture. As a result of the reduced size chips, which
may be on the order of about 2.2 mm by 2.2 mm in area, for example,
attention must be directed not only to enhanced power efficiency,
but also the effective size of the antenna as compared with its
physical size.
[0081] A feature of the embodiments is the use of a voltage doubler
(charge pump) to provide sufficient voltage for certain CMOS or
other fabrication technologies to function efficiently.
[0082] With reference to FIG. 8 there is shown a voltage source V1
which represents the antenna on the remote station for receiving
the RF signal. In the form shown, the circuit contains two diodes
D1, D2 and three capacitors C1, C2, C3, with capacitor C1 being
interposed between voltage source V1 and diodes D1 and D2. This
circuit serves to increase the voltage and power emerging from
output 190.
[0083] The series connection of two or more voltage doublers to
increase the voltage even further is exemplified in FIG. 9. The
cumulative effect of voltage sources V1 and V2 provides enhanced
output at 194 substantially greater than the output of the single
voltage doubler in FIG. 8. The voltage sources V1 and V2 supplies
are simply the two antennas with any necessary impedance
matching.
[0084] Another feature of this embodiment of the invention is the
use of antennas such that the effective antenna is larger than the
physical antenna. The use of multiple (small) antennas in a given
region to increase the energy harvest is also provided.
[0085] If the antenna efficiency is less than or equal to 50%, 2
(or more) antennas could theoretically harvest 100% of the energy.
If they were of 25% efficiency, one may use 4 antennas and so on.
This facilitates effecting the equivalent of the fabrication of
100% efficient antennas which, at this time, is a goal somewhat
difficult to achieve.
[0086] If the antenna efficiency is greater than 50%, 2 antennas
could be used with 2 different frequencies from two sources of
different frequencies. This could be expanded to 3, 4, or more
antennas and frequencies. A further advantage of doing this is the
FCC limitation on power. If one needs 2 watts, and the maximum
allowed is 1 watt at 418 MHz or 433 MHz, then one may use 2
antennas with two 1 watt transmitters satisfying the FCC and the
power requirements of the device that is being powered. This is
essentially a superposition of the two frequencies that
theoretically could be expanded across a whole frequency band. The
limitation on how many could be superimposed would be dependent on
the spectrum of each transmitter and the selectivity of the tank
circuit on the device receiving the energy.
[0087] Turning to the relationship between the antenna's effective
area and the antenna's physical size, consider the continuous
transmission of radio frequency (RF) energy from a transmitting
antenna at a fixed-base location and orientation. An object of
interest placed in the energy field of the transmitter scatters the
incident energy possibly in many directions. Some of the energy at
the object of interest is scattered in the direction of the
antenna.
[0088] Consider the straight line between the "bore sight" of the
transmitting antenna and the center of the object. The scattered
energy in this direction is termed a monostatic scattering or the
backscattering of the incident energy.
[0089] In the case of a passive object, the backscatter has an
energy density that is a function of a number of factors including
size, shape and composition of the object. The object is generally
assumed to behave as an antenna with some effective capture area or
simply effective area, A.sub.e. The power reflected by this object
thus acts as an antenna and is given by relationship (1), where
W.sub.T is representative of the power transmitted by the source
transmitting antenna; A.sub.e is the effective area of the object,
and P.sub.R is the power reflected by the object.
P.sub.R=A.sub.eW.sub.T wherein W.sub.T is in watts per square meter
(1)
[0090] The device of this embodiment "harvests" the power
received.
[0091] FIG. 10 represents schematically a device for receiving,
on-chip functioning and retransmission of energy. In FIG. 10, the
source of power is a base station that transmits power, P.sub.TB
The remote station device receives a certain amount of power,
P.sub.RD, uses some of the power, P.sub.U, and retransmits power
P.sub.TD. A base station, P.sub.RB, which may be collocated with
the original source of power, receives the retransmitted power,
Collocation would likely be the case in radar and many Radio
Frequency IDentification (RFID) systems, for example.
[0092] If the function of the device is RFID, P.sub.TD is important
to communicate information to a base station. If the function of
the device (remote station) is strictly energy harvesting, P.sub.TD
is to be minimized, i.e., maximize P.sub.U. This is also the case
when the device does not want to be recognized, i.e., a stealth
device.
[0093] Obviously, the power leaving the device (transmitted or
scattered), P.sub.TD, is less than the incident power, P.sub.RD. By
conservation analysis, we can form equation (2).
P.sub.RD=P.sub.U (Power Used)+P.sub.TD(Power Transmitted/Scattered
by the Device) (2)
[0094] For power leaving the device, the power density
(watts/meter.sup.2) of the transmitted or scattered power is
W.sub.TD. The subscripts used here are to maintain consistency with
FIG. 10. 1 W TD = [ P RD - P U ) / ( 4 R 2 ) ] = [ ( A e Y 0 E TB 2
) / ( 8 R 2 ) ] - [ ( P U ) / ( 4 R 2 ) ] = [ ( A e Y 0 E TB 2 - 2
P U ) / ( 8 R 2 ) ] ( 3 )
[0095] In equation (3) "R" is the distance between the base station
and the remote station "Y.sub.o" is the admittance of free space
and "E.sub.TD" and "E.sub.TB" the electric field strength in
volts/meters. Equation (3) assumes the device is an isotropic
radiator. The area, A.sub.e, will be discussed hereinafter. The
reflected power density from the device in the case (with
P.sub.U=0), W.sub.TD, is also given where P.sub.U=0:
W.sub.TD=[(Y.sub.0.vertline.E.sub.TD.vertline..sup.2)/2] (4)
[0096] Note that WT in (4) is the incident (received) power at the
device thus equating (3)and (4). In the present case, this is
simply another form for the source energy density.
[(Y.sub.0.vertline.E.sub.TD.vertline..sup.2)/2]=[(A.sub.eY.sub.0.vertline.-
E.sub.TB.vertline..sup.2-2P.sub.U)/(8.pi.R.sup.2)] (5)
(4.pi.R.sup.2)Y.sub.0.vertline.E.sub.TB.vertline..sup.2=A.sub.eY.sub.0.ver-
tline.E.sub.TB.vertline..sup.2-2P.sub.U (6)
A.sub.eY.sub.0.vertline.E.sub.TB.vertline..sup.2=(4.pi.R.sup.2)Y.sub.0.ver-
tline.E.sub.TD.vertline..sup.2+2P.sub.U (7)
A.sub.e=[(4.pi.R.sup.2.vertline.E.sub.TD.vertline..sup.2)/.vertline.E.sub.-
TB.vertline..sup.2]+[(2P.sub.U)/(Y.sub.0.vertline.E.sub.TB
.vertline..sup.2)] (8)
[0097] As more and more power, P.sub.U, is used by the device, the
ratio,
.vertline.E.sub.TD.vertline..sup.2/.vertline.E.sub.TB.vertline..sup.2,
will approach zero. From the standpoint of the effective area of
the device, from (8), the following inequality can be seen to be
true.
A.sub.e.gtoreq.[(2P.sub.U)/(Y.sub.0.vertline.E.sub.TB.vertline..sup.2)]
(9)
[0098] The effective area can be calculated by measuring R, E.sub.T
(E.sub.TD) and E.sub.TB. A remote device that (1) consumes a
certain amount of the power received, P.sub.U, and (2) transmits
the balance of the received power, P.sub.TD, through a second
antenna on the device will be considered.
[0099] The receiving antenna on the remote device is termed the
harvesting antenna, and the second antenna is termed the
transmitting antenna. This type of device has been termed an Active
Remote Sensor or ARS device [ARS].
[0100] Consider equation (8) in relation to inequality (9). For
100% conversion, P.sub.U=P.sub.RD and
.vertline.E.sub.TD.vertline.=0. Thus, in (8)
A.sub.e=(2P.sub.RD)/(Y.sub.0.vertline.E.sub.TB.vertline.2)
[0101] giving
2 P.sub.RD=A.sub.eY.sub.0.vertline.E.sub.TB.vertline..sup.2
P.sub.RD=A.sub.e(Y.sub.0/2).vertline.E.sub.TB.vertline..sup.2
[0102] From (1),
P.sub.R=P.sub.RD=A.sub.eW.sub.T
[0103] substituting for WT,
P.sub.RD=A.sub.e[Y.sub.0.vertline.E.sub.TB.vertline..sup.2/2]
[0104] which is a consistent result.
[0105] From (9), the lower bound on the effective area can be
calculated by knowing the power used, P.sub.U and the field
strength of the transmitted power,
.vertline.E.sub.TB.vertline..sup.2.
[0106] The focus of this embodiment is the effective area of the
harvesting antenna. The lower bound on the effective area will be
considered. Jn particular, A.sub.e in (9) can be calculated simply
from, P.sub.U, and .vertline.E.sub.TB.vertline.. The value to
obtain in (9) is E.sub.TB.
EXAMPLE
[0107] An antenna termed Delta 1 was fabricated using the AMI_ABN
process through MOSIS [C]. The total die size was 2200
.mu.M.times.2200 .mu.M with a square spiral antenna slightly more
than 3 inches in total conductor length, i.e., 1/4 wavelength at
915 MHz.
[0108] Experiments were completed where the power measured at the
chip, at a variety of orientations, was on the order of 5 mW. The 5
mW value was the power used, P.sub.U, by the remote device
(object). The electric field at the Delta 1 antenna was determined
through simulation to be 55.52 volts/meter. In the relationship
(9), there are three variables A.sub.e, P.sub.U and E.sub.TB.
[0109] From the experiments, we have:
[0110] (a) A P.sub.U measured value of 5 mW
[0111] (b) A calculated/simulated value of E.sub.R=55.52
volts/meter
[0112] (c) An unknown value for A.sub.e
[0113] In addition, the transmitted power, P.sub.TB, from the base
station antenna was known. From the antenna radiation pattern and
the directive gain, the power density at the device antenna can be
calculated.
[0114] (d) Power Density at the remote station or device=5.989
watts/meter.sup.2
[0115] First, (a) and (d) were employed in a straightforward manner
to determine an effective area, A.sub.e, (c) assuming the energy is
harvested at 100% efficiency.
A.sub.e=(5.times.10.sup.-3 watts)/(5.989
watts/meter.sup.2)=8.349.times.10- .sup.-4 meter.sup.2 (10)
[0116] Next, using (a) and (b) to determine the effective area
(c)
A.sub.e.gtoreq.[(2*5*10.sup.-3 watts)/(0.00265
mhos.vertline.E.sub.TB.vert- line..sup.2)]=12.242.times.10.sup.-4
meter.sup.2 (11)
[0117] Next, using (10) and (b), to calculate an electric field
strength from (9) as a check on (b). 2 E TB 2 = ( 2 * 5 * 10 - 3
watts ) / ( 0.00265 mhos * 8.349 .times. 10 - 4 meter 2 ) ] = 4519
volts 2 ( 12 )
.vertline.E.sub.TB.vertline.=[4519 volts].sup.1/2=67.2 volts
(13)
[0118]
1 Case 1 Case 2 Effective area, A.sub.e 8.349 .times. 10.sup.-4
meter.sup.2 12.242 .times. 10.sup.-4 meter.sup.2 Electric Field
Strength, 55.52 volts 67.2 volts .vertline.E.sub.TB.vertline.
[0119] Based on the relatively close agreement of the above
results, the antenna effective area is at least
8.349.times.10.sup.-4 meter.sup.2. From the chip dimensions, the
total antenna area is actually 2.4.times.10.6 meter.sup.2. Thus,
the effective area, A.sub.e, is 8.349.times.10.sup.-4
meter.sup.2/2.4.times.10.sup.-6 meter.sup.2=347.8 times the
physical antenna area.(14)
[0120] From (14), it is clear that the effective area of the
antenna is much greater than the physical area and within these
parameters is more than 300 times greater. This facilitates
effective use of the present invention on microchips on remote
stations.
[0121] From the relationship in (8), it is assumed that the power
used and the power radiated by the device can be considered as
separable, P.sub.U and P.sub.TD The device is simultaneously
receiving and radiating power. The received power is consumed on
the device with the radiated power giving some sort of an effective
area or aperture as in the case of backscatter. In essence, there
are two areas involved, A.sub.e(P.sub.U) and Ae(P.sub.TD). There is
a separability of areas, i.e.,
A.sub.e=A.sub.e(P.sub.U)+A.sub.e(P.sub.TD). (15)
[0122] As an optimization problem, it is desirable to increase
A.sub.e(P.sub.U) and decrease A.sub.e (P.sub.TD). As a result, the
more power used, the less of an RF signature that will be produced.
However, as a stealth device, this may not be desired as the
infrared (IR) signature will be increased.
[0123] In very small antennas, certain physical advantages are not
gleaned from Maxwell's Equations. A 1/4 wavelength whip antenna
with ground plane was compared with the small die/antenna on the
basis of simply physical volume occupied. The volume around the 1/4
wavelength antenna and ground plane in this case occupies
1.897.times.10.sup.-3 meter.sup.3. The die/device occupies
1.473.times.10.sup.-9 meter As a result, the volume reduction is
greater than 6 orders of magnitude. The 1/4 X antenna harvests"
about 50 mW of power compared to about 5 mW of power for the Delta
1 die/antenna, which is a decrease of 1 order of magnitude. The
reduction in size is obviously a benefit in numerous
applications.
[0124] This comparison is based on a die antenna fabricated with a
CMOS process where the dielectric is strictly a function of the
process available with no opportunity for size adjusting in
separating the antenna from the ground plane.
[0125] The 1/4 wavelength antenna used is a widely used commercial
device. The Delta 1 die antenna was designed with a number of tools
for producing an integrated tank circuit, but the fabrication was
strictly a straightforward submission to MOSIS using the AMI-ABN
1.5 .mu. process. The distance and dielectric between the antenna
(Metal 2) and the ground plane (bottom of the silicon substrate)
were not controlled. However, with this fabrication, the relative
volume comparison made in FIG. 11 supports the achieving a harvest
of sufficient power to perform useful functions on a CMOS or MEMS
device.
[0126] Note in FIG. 11, that the Delta 1 antenna is comparable with
the volume of Smart Dust when compared with the commercial antenna.
Smart Dust is a combination MEMS/Electronic device on the order of
1 mm.times.1 mm.times.1 mm.
[0127] Turning again to the power enhancement through the use of a
voltage doubler circuit, comparisons will be made between incident
power and output voltage. Also, the use of multiple voltage
doublers will be considered in further detail. Many RF products
such as portable RIFD tags are too small to contain a battery.
Their small demand for power, however, makes it possible to power
them with ambient RF energy which may come from a base station
interrogator and be captured by an antenna on the remote station.
It is important, however, in converting the RF power into DC power
at the remote station, to enhance the efficiency as the amount of
RF energy captured by the antenna may be limited due to the
antenna's relatively small size.
[0128] The voltage doubler presents a way of getting high DC output
voltage from an AC source. It has two forms, which may be the
conventional form is shown in FIG. 12(a) or the cascade form as
shown in FIG. 12(b). In both forms, shown in FIGS. 12(a) and 12(b)
the RF wave is rectified by D.sub.1, C.sub.1 in the positive cycle
and by D.sub.2, C.sub.2 in the negative cycle. When the load
R.sub.L is large, the output voltage is roughly two times the peak
voltage V.sub.g of the RF source minus the turn-on voltage V.sub.D0
of the diode.
[0129] A voltage doubler circuit, therefore, may be considered to
be two single diode detector circuit in series connection.
[0130] For RF applications, Schottky Diode is often employed as the
detector diode as a result of its low turn-on voltage and small
junction capacitance. It is modeled as an ideal exponential diode
with the junction capacitance C.sub.1 in series with a resistor
R.sub.S as shown in FIG. 13. The ideal diode is supposed to satisfy
the exponential i-v relationship. 3 i = I s [ exp ( v n ) - 1 ] (
16 )
[0131] wherein I.sub.S is the reverse saturation current, n is
diode ideality factor, .LAMBDA.=q/(kT), q is electronic charge, k
is Boltzmann's constant, T is temperature in Kelvin degrees.
[0132] It is apparent that three key parameters of the diode,
I.sub.S, C.sub.J and R.sub.S, determine the power conversion
efficiency of the voltage doubler circuit. The larger I.sub.S helps
to lower down V.sub.D0 and increases output voltage as V.sub.D0 is
approximately equal to Vg minus V.sub.D0. Junction capacitance
diverts the diode current only to produce voltage drop on R.sub.S,
in order that large C.sub.J and R.sub.S will reduce the output
voltage, particularly when frequencies are high. The parameters
I.sub.S, C.sub.J and R.sub.S are related to each other due to
physical properties of the diodes. 4 I 0 ( n 8 R g P inc ) = ( 1 +
I h I s + V n R L I s ) exp { [ 1 + R g + R s R L ] n V n + n R s I
n } ( 17 )
[0133] I.sub.0 is the zero-order modified Bessel function of the
first kind, R.sub.g is the source impedance, R.sub.L is the output
load resistance, I.sub.o is bias circuit current for the circuit
which is equal to 0 in power conversion applications.
[0134] Equation 17 describes the relationship between incident
power P inc on the detector Circuit and the output voltage
V.sub.0.
[0135] In FIG. 14, which is a voltage doubler equivalent circuit,
equation 17 can be applied. It will be seen that the output voltage
of the voltage doubler is two times that of a detector circuit with
one half the original load.
[0136] Equation 17 is a good approximation of output voltage of a
voltage doubler when C.sub.J is small or the operating frequency is
low.
[0137] For some applications the output voltage of a single voltage
doubler may not be adequate to operate the remote device. One may
employ multiple RF sources and add them together to achieve higher
output voltage. If each independent source, with the voltage double
circuit dedicated to it is seen as a battery with an open circuit
output voltage V.sub.0 and an internal resistance R.sub.L, the
output voltage on a load with resistance RL will be 5 V out = nV 0
nR 0 + R L R L = V 0 1 R 0 R L + 1 n ( 18 )
[0138] when n of them are put together.
[0139] As seen in equation 18, the output voltage V.sub.out is
determined by the total of capital R.sub.0/R.sub.L and 1/n if
V.sub.0 is fixed. When the load is close to or smaller than the
internal resistance of the voltage doubler R.sub.0/R.sub.L becomes
dominant when increasing n will not assist much in getting higher
output voltage.
[0140] In summary, it is desirable to increase the I.sub.S and
reduce the C.sub.J of the Schottky Diode in order to increase the
power conversion efficiency of a voltage doubler. Adding multiple
voltage doublers in series is a way of getting higher output
voltage subject to the gain decreasing when the load becomes
heavy.
[0141] With reference to FIG. 14, it will be noted that a further
advantage of the present invention is that in connection with
miniaturized electronics chips, the antenna may be provided within
the rather small dimensions of the chip but have an effective
antenna size greater than the physical antenna size. FIG. 14 shows
such an antenna and FIG. 15 shows the antenna incorporated into an
electronic microchip. Another advantage of the present system is
that the system has the ability to incorporate an LC "tank" circuit
in the antenna designs This is accomplished through the use in the
antenna of inter-electrode capacitance and inductance to form the
LC tank circuit.
[0142] It will be appreciated, therefore, that the present
invention provides an effective means for establishing a system
wherein a base station cooperates with a remote station by
exchanging data in both directions with the base station serving to
provide transmitted energy which serves to energize the remote
station to permit functioning thereof. As a result, there is no
need to have a wired system connecting the remote station with a
source of power or for it to carry a power storage unit. This
permits low or no maintenance remote systems which may be implanted
in individuals, used for other medical purposes, used in space,
industry, security and a wide range of other uses. All of this is
accomplished in a simple, efficient manner employing the apparatus
and methods of the present invention.
[0143] While for simplicity of disclosure primary attention herein
has been directed toward a system employing RF power as the source
of energy delivered to the remote station, and such is currently
the preferred approach, it will be appreciated that alternate
sources of power may be employed. A light beam, for example, with
suitable means for receiving the light on the remote station and
converting it to responsive electrical output, such as an
appropriate DC voltage may be employed. The converter devices, such
as CMOS or TTL, could provide voltages at desired levels and
currents on the order of milliamps to power the device.
[0144] Whereas particular embodiments of the invention have been
described above for purposes of illustration, it will be
appreciated by those skilled in the art that numerous variations of
the details may be made without departing from the invention as
described in the appended claims.
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