United States Patent (19)
`Schuermann
`
`||||||||||||III
`US005287112A
`5,287,112
`11
`Patent Number:
`Feb. 15, 1994
`(45) Date of Patent:
`
`54 HIGH SPEED READ/WRITE AVI SYSTEM
`(75) Inventor: Josef H. Schuermann, Oberhummel,
`Fed. Rep. of Germany
`73) Assignee: Texas Instruments Incorporated,
`Dallas, Tex.
`(21) Appl. No.: 48,541
`22 Filed:
`Apr. 14, 1993
`51) int. Cl. .............................................. G01S 13/74.
`52) U.S. Cl. ......................................... 342/42: 342/.51
`58) Field of Search .................................... 342/42, 51
`(56)
`References Cited
`U.S. PATENT DOCUMENTS
`3,689,885 9/1972 Kaplanet al..................... 342/42 X
`4,042,970 8/1977 Atkins ...............
`... 342/42 X
`4,713, 148 1/1973 Cardulio et al. ...................... 342/42
`4,912,471 3/1990 Tyburski et al. ...................... 342/42
`4,926, 182 5/1990 Ohta et al. ............
`... 342/S X
`4,963,887 10/1990 Kawashima et al. .
`342/42 X
`5,053,774 10/1991 Schuerman et al. .................. 342/44
`5,073,781 12/1991 Stickelbrocks ........................ 342/.51
`OTHER PUBLICATIONS
`U.S. application Ser. No. 07/981,635, Meier et al.
`Primary Examiner-Mark Hellner
`
`Attorney, Agent, or Firm-Brian C. McCormack; James
`C. Kesterson; Richard L. Donaldson
`57)
`ABSTRACT
`A transponder (14) for communicating with an interro
`gator (12) has a high Q-factor resonant circuit (34) of
`frequency f1 for receiving RF powering signals. The
`transponder also has a tuning circuit (56,58) which
`when in electrical communication with the resonant
`circuit (34) is operable to form a lower Q-factor reso
`nant circuit (60) of frequency f. for receiving RF com
`munications from the interrogator unit. The transpon
`der also includes a demodulator (66) which is in electri
`cal communication with said resonant circuit (34). Ad
`ditionally, the transponder (14) also included a control
`circuit (40) which receives a demodulated data signal
`from the demodulator (66). The control circuit (40) is
`further connected to the tuning circuit (56,58) and is
`operable to connect the tuning circuit (56,58) to the
`high Q-factor resonant circuit (34) in order to form the
`lower Q-factor resonant circuit (60). Control circuit
`(40) also converts the RF powering signals to a DC
`current for storing energy. The energy is stored in an
`energy storage device such as a storage capacitor (46).
`Other devices, methods and systems are disclosed.
`
`16 Claims, 1 Drawing Sheet
`
`
`
`Ex.1007
`APPLE INC. / Page 1 of 7
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`

`

`U.S. Patent
`U.S. Patent
`
`Feb. 15, 1994
`Feb. 15, 1994
`
`5,287,112
`5,287,112
`
`8969egpoly
`LY99
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`Ex.1007
`APPLE INC./ Page 2 0f 7
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`_
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`Ex.1007
`APPLE INC. / Page 2 of 7
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`

`

`1.
`HIGH SPEED READ/WRITE AVI SYSTEM
`CROSS-REFERENCE TO RELATED PATENTS
`The following coassigned patent applications are
`hereby incorporated herein by reference:
`
`Pat No./Serial No.
`5,053,774
`O7/98,635
`
`Filing Date
`2/13/91
`11/25/92
`
`T Case No.
`T-12797A
`T-6688
`
`5
`
`O
`
`25
`
`35
`
`40
`
`5,287, 112
`2
`cost, size and power efficiency. The resonant circuit in
`each of the interrogator and the transponder is used for
`both communication and power transfer in this prior
`art. For optimal power transfer the prior art device uses
`highly tuned, high Q-factor resonant circuits.
`Generally in prior art circuits using highly tuned,
`high Q-factor resonant circuits for communication, the
`preferred modulation technique is 100% amplitude shift
`keying (ASK) modulation or another modulation tech
`nique where the frequency is not modulated (e.g., PSK,
`QPSK). These modulation techniques allow the link to
`continue to operate within its tuned frequency. The
`modulation percentage in ASK refers to the percentage
`by which the amplitude of the carrier is reduced from
`its maximum. For example, On-Off Keying (OOK), also
`called 100% ASK, means that one logic level will be
`represented by maximum carrier while the other logic
`level will be represented by an absence of a carrier.
`Further illustrating, 50% ASK means that one logic
`level will be represented by maximum carrier while the
`other logic level will be represented by a carrier having
`an amplitude of 50% of maximum.
`The reason that frequency shift keying (FSK) is diffi
`cult to use for communicating between two highly
`tuned, high Q-factor resonant circuits is that the power
`transfer between two high Q-factor resonant circuits
`drops off rapidly as the carrier frequency deviates from
`the tuned frequency. Inherently the carrier frequency
`within FSK modulation deviates from the tuned fre
`quency. ASK modulation can be used with high Q-fac
`tor tuned circuits and where high data transmission
`speed is not the primary consideration. Within a high
`Q-factor circuit, however, the ringing of the resonant
`circuit takes a significant time period to subside, thereby
`limiting the data transfer rate. Ringing can be reduced
`by reducing the modulation percentage or reducing the
`Q-factor.
`SUMMARY OF THE INVENTION
`The preferred embodiment of the present invention
`overcomes the difficulties described above in that it
`allows the use of a single set of circuitry in each of the
`interrogator and the transponder for transmission and
`reception of both powering and communication signals.
`In the preferred embodiment, as in the '774 patent by
`Schuermann, a single resonant circuit is implemented in
`each of the interrogator and the responder for maxi
`mum efficiency of cost, size, and power consumption.
`The preferred embodiment of the present invention,
`however, also provides a circuit and method for using
`other than ASK or PSK modulation for both the uplink
`and the downlink. Preferably FSK is used for both the
`uplink and the downlink transmissions allowing higher
`data transmission speeds. The conflicting needs for effi
`cient power transfer and fast FSK communication are
`met in preferred embodiments of the present invention.
`First the interrogator sends a powering burst to the
`transponder during which the interrogator and tran
`sponder are tuned with high Q-factor resonant circuits.
`The interrogator then begins to transmit WRITE data
`to the transponder using FSK modulation. The tran
`sponder then adapts itself to receive the larger band.
`width FSK signal by damping (i.e., lowering the Q-fac
`tor) of its tuned circuit. The transponder's tuned circuit
`preferably is tuned to the center of the FSK frequencies.
`The data transfer rates achieved using FSK modulation
`exceeds that using other modulation techniques. Yet
`
`FIELD OF THE INVENTION
`15
`This invention generally relates to a fast read/write
`Radio Frequency Identification (RFID) System. A
`transponder is operable to receive powering signals
`over an antenna that is tuned with a high Q-factor to the
`antenna of an interrogator. The transponder preferably
`20
`adapts itself for reception of FSK communications from
`the interrogator by sideband detuning of its antenna,
`thus facilitating reception of FSK communications hav
`ing a wide frequency band relative to the narrow band
`powering signal.
`BACKGROUND OF THE INVENTION
`Heretofore, in this field, a powering antenna has often
`been provided with the interrogator in addition to the
`communicating antenna. This powering antenna is pro
`vided for the powering of a transponder not having its
`30
`own internal power supply. The powering antenna may
`be a high Q-factor antenna to effect maximum power
`transfer to the transponder. Because of the flexibility
`afforded by having a spearate power antenna in the
`interrogator which may be optimized for power trans
`fer to the transponder, the transponder antenna may be
`optimized for communicating with the interrogator's
`communicating antenna. An example of this type of
`system is given in U.S. Pat. No. 4,550,444 by Uebel and
`in U.S. Pat. No. 4,912,471 by Tyburski et al. In such
`systems the RF coupling can be separately designed for
`the power transfer link and the communications link.
`The disadvantage in such a system is the inherently
`greater cost and size involved in a transponder having
`two separate circuits for powering and communicating.
`45
`Another known technique allowing for somewhat opti
`mized powering and communication links is to provide
`separate transmit and receive antennas in the transpon
`der. In this way the downlink (i.e., the communication
`link from the interrogator to the transponder) can be
`50
`designed for efficient power transfer. Because the tran
`sponder is desirably compact and power-efficient, the
`uplink (i.e., the communication link from the transpon
`der to the interrogator) can be optimized to the tran
`sponder's transmit antenna. Communication can still be
`effectively carried out over the downlink because of the
`lesser need for power and cost efficiency in the interro
`gator transmitter design. An example of this type of
`system can be found in U.S. Pat. No. 3,713, 148 by Car
`dullo et al. As before, the disadvantage in such a system
`60
`is the inherently greater cost and size involved in a
`transponder having two separate circuits, this time for
`receiving and transmitting.
`Yet another known technique is described in U.S.
`Pat. No. 5,053,774 by Schuermann, et al. In this tech
`65
`nique, communication and power transfer is preferably
`accomplished by a single resonant circuit in each of the
`interrogator and the transponder thereby minimizing
`
`55
`
`Ex.1007
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`20
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`30
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`35
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`5,287, 112
`4.
`3
`The first phase is the Powering phase or phase "A" and
`other advantages provided by the present invention
`lasts from time to to t1. The second phase is the Down
`include greater data security owing to the greater con
`link phase or phase "B" and lasts from time t to t2. The
`plexity and redundancy of decoding FSK signals and
`third phase is the Memory Write phase or phase "C"
`the lesser sensitivity to the Q-factor of the resonant
`and lasts from time t2 to t3. The fourth phase is the
`circuits.
`Uplink phase or phase "D' and lasts from time t3 to t3.
`BRIEF DESCRIPTION OF THE DRAWINGS
`The number of phases and the actions undergone during
`them is to illustrate one embodiment contemplated by
`In the drawings:
`the inventor. Various modifications and combinations
`FIG. 1 is a block circuit diagram of the preferred
`of the phases, also other embodiments of the invention,
`system embodiment;
`will be apparent to persons skilled in the art upon refer
`FIG. 2 is a graph of the transponder power supply
`ence to the description. It is therefore intended that the
`voltage, VCL, vs. time;
`appended claims encompass any such modifications or
`FIG. 3 is a frequency spectrum illustrating the power
`spectrums for the highly tuned and detuned configura
`embodiments.
`FIG. 3 is a frequency spectrum illustrating the power
`tions of the transponder (graphs A and B, respectively);
`15
`spectrums for the highly tuned and detuned configura
`FIG. 4 is a block circuit diagram of a preferred FSK
`tions of the transponder (graphs A and B, respectively).
`demodulation circuit; and
`Now that the phases and frequency spectrums have
`FIG. 5 is a frequency spectrum illustrating the filter
`been named and listed and an overview of the main
`characteristics of the slope detector of FIG. 4.
`components of the transponder system has been de
`DETAILED DESCRIPTION OF PREFERRED
`scribed, the remaining components and their uses dur
`EMBODIMENTS
`ing each phase will be described.
`Again referring to Flo. 1, now together with FIG. 2
`FIG. 1 shows a transponder arrangement 10 compris
`and FIG. 3, the remaining components, timing, and
`ing an interrogator 12 and a responder or transponder
`frequency spectrum of the preferred embodiment will
`14. The interrogator 12 preferably comprises a control
`be described. During the "A" phase, within the interro
`circuit 16 which controls the actions of the interrogator
`gator 12 a carrier wave generator 24 operates to pro
`circuitry. The control circuit 16 causes the modulator
`vide a reference frequency to a programmable divider
`48 to generate either the powering frequency for a
`25. A buffer or amplifier 26 receives a divided carrier
`second frequency f2. In the illustrated embodiment the
`having a first or second frequency, for f2, from the
`second frequency f2 is used to represent one state of the
`programmable divider 25 and passes the signal to an
`WRITE data while the powering frequency f is used
`interrogator tuned circuit 28. Tuned circuit 28 is prefer
`during data transmission to represent the other state of
`ably tuned to f although it is well known that a hat
`the WRITE data. This FSK keying is accomplished by
`monic of the resonant frequency for another frequency
`control circuit 16 controlling modulator 48 to open and
`could be used if design needs dictated. In this embodi
`close a switch 50 thereby changing the resonant fre
`ment, the modulator 48 further acts to select the reso
`quency of the resonant circuit 28. The modulator 48
`nant frequency of the tuned circuit 28 to coincide with
`further changes the division factor of the programmable
`the corresponding frequency selected by the modulator
`divider 25 to divide the reference carrier by a selectable
`48 using the programmable divider 25. The mechanism
`ration (n1, n2) to one of two selectable frequencies (f,
`that modulator 48 uses to select the resonant frequency
`f2). When the switch 50 is open, the resonant circuit 28
`of tuned circuit 28 is a switch 50 that is open or closed
`oscillates at frequency f. When the switch 50 is closed
`depending on the output of modulator 48. The tuned
`and the capacitor 52 is connected in parallel, the reso
`circuit 28 preferably comprises the parallel combination
`nant circuit 28 resonates at frequency f2. The interroga
`of a coil 30 and a capacitor 32. The switch 50 when
`tor 12 might be a standalone unit, or alternatively, might
`closed forms a parallel connection of another capacitor
`be connected by a host connection 18 to a host com
`45
`52 across tuned circuit 28 thus lowering the resonant
`puter. The control circuit 16 is preferably connected to
`frequency of resonant circuit 28 to f. A series resonant
`a memory 20 that is operable to maintain, among other
`circuit could also be used as tuned circuit 28 if the anp
`things, a list of instructions for the control circuit 16 to
`26 is to drive a low impedance tuned circuit (e.g., a
`execute, information regarding various transponders 14
`series resonant circuit). The oscillation of this tuned
`and groups of transponders for addressing. The mem
`50
`circuit 28 transmits RF energy that is received by the
`ory 20 is also operable to receive information written to
`transponder 14. A transponder resonant circuit 34 that
`it by control circuit 16. This information may be gained
`also is tuned ideally to fl receives this energy. The tran
`from inquiries of the transponder 14 and may include
`sponder resonant circuit 34 preferably comprises the
`data and addresses returned by the transponder 14. Yet
`parallel combination of a coil 36 and a capacitor 38. A
`another component preferably operating under the con
`55
`transponder control circuit 40 is connected to this reso
`trol of the control circuit 16 is a display 22 that may
`nant circuit 34 at a reference connection 42 and at a
`visually express to a user the results of an interrogation
`signal connection 44. The control circuit 40 receives its
`or communicate status information.
`energy from the resonant circuit 34, rectifies the re
`Referring now to FIG. 2, a graph is shown of the
`ceived signals, and stores the energy on a storage capac
`relative transponder operating voltage VCL on the ver
`itor 46. The mechanisms for rectifying signals and stor
`tical scale and time on the horizontal scale. The vertical
`ing energy are well known to one of ordinary skill in the
`scale is in volts, with the preferred operating voltage
`art. Examples of circuitry for performing these func
`VCL=5V. No units are provided for the horizontal
`tions can be found in U.S. Pat. No. 5,053,774, incorpo
`scale as the figure is intended solely to provide informa
`rated by reference in this application.
`tion regarding the general operational characteristics of 65
`During the "B" phase the control circuit 16 sends
`the communication between the transponder 14 and
`data to a modulator 48. An FSK modulator 48 under
`interrogator 12. As shown on the graph of FIG. 2, the
`direction of control circuit 16 operates to control pro
`preferred communications protocol has four phases.
`
`Ex.1007
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`10
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`35
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`5,287, 112
`5
`6
`28,60 are no longer tightly coupled during phase "B"
`grammable frequency divider 25 to pass either a first
`frequency, f, or a second frequency, f2, on to buffer
`the energy transmission from the interrogator 12 to the
`transponder 14 is reduced. Thus, the storage capacitor
`/amplifier 26. The frequencies f and f2 are selected
`46 must supply energy to the transponder circuitry for
`submultiples of the reference frequency. The carrier
`wave generator 24 is preferably a crystal oscillator. As
`the transponder 14 to remain operational. As shown in
`an example, one polarity of the WRITE data might be
`FIG. 2, the storage capacitor 46 voltage VCL drops
`during this phase as it supplies this energy to the tran
`the reference carrier divided by ration (f), while the
`other polarity of the WRITE data might be represented
`sponder circuitry. As an option at the end of this phase
`by another frequency that is the reference carrier di
`a short handshake can be added to verify data reception
`vided by ratio n2 (f2). The modulator 48 controls a
`without bit errors.
`switch 50 that can connect a capacitor 52 in parallel
`Referring to FIG. 1, upon receipt and demodulation
`with tuned circuit 28.
`of the downlink signal the control circuit 40 during
`Connecting the capacitor 52 in parallel with this
`phase "C" writes to memory 62. In some embodiments
`phase "C" may be optional. However, even if memory
`tuned circuit 28 forms a new tuned circuit 29 with a
`new, lower resonant frequency f2. By opening and clos
`62 is not written to during this phase, this phase may be
`15
`ing switch 50 in synchronism with the control of pro
`used to restore energy to the storage capacitor 46. In
`grammable divider 25 the resonant circuit 28 or new
`the instance where phase "C" is used to restore the
`resonant circuit 29 remains optimally tuned to the trans
`storage capacitor 46, the interrogator 12 again opens
`mitted frequencies f and f2. By choosing f to represent
`switch 50 such that the tuned circuit 28 again resonates
`one logic level and f2 to represent another it is possible
`at fl. The transponder opens switch 54 such that the
`to transmit information from the interrogator 12 to the
`resonant circuit 34 again resonates with a high Q at fi
`transponder 14. Data is received in the transponder 14
`and maximum transmission of power from the interro
`by the transponder's resonant circuit 34. A downlink
`gator to the responder can resume. Since the storage
`signal is passed on to demodulator 66 that in turn trans
`capacitor 46 is presumably not fully discharged the time
`mits a received data stream to the control circuit 40.
`required to charge is greatly reduced. The time re
`25
`The received WRITE data is typically FSK demodu
`quired is on the order of 15-20% of the original power
`lated by the demodulator 66. Techniques and circuits
`ing time.
`for FSK demodulation are well known in the art.
`Again referring to FIG. 1, during phase "D" interro
`An illustrative FSK demodulation circuit 66 is shown
`gator tuned circuit 28 is damped to enable downlink
`in FIG. 4. In this circuit, a filter 67 is provided to re
`30
`FSK reception. Phase "D" also is an optional phase,
`ceive the downlink signal on signal line 44. This filter 67
`since a transponder response or unlink might not be
`may be either a lowpass or a highpass filter which acts
`necessary in all instances. In the event that reception of
`as a slope detector where the FSK signal is converted to
`a transponder response or uplink is desired, the interro
`an ASK signal. The slope detector operates by having
`gator tuned circuit 28 might be damped by the control
`each of the FSK frequencies (f1, f2) lie on the filter
`circuit 16 by disabling the carrier wave generator 24
`roll-off so the amplitude of the output will be different
`and by shunting a switch/resistor series combination
`depending on the input FSK frequency. The signal on
`across the resonant circuit. This damping of the carrier
`line 69 corresponding to the output of the filter is shown
`wave generator 24 is described in the '774 patent by
`in FIG. 5. FIG. 5 shows a frequency plot of the rolloff
`Schuermann et al. Once the oscillation of resonant cir
`of filter 67 with the position of f and f shown on the
`40
`cuit 28 is damped, the interrogator 12 is free to receive
`frequency (horizontal) scale. As can be seen from FIG.
`signals from the transponder 14. Within the transponder
`5, a different amplitude corresponds on the vertical
`14, the resonant circuit 34 continues to oscillate until the
`scale with each of the different FSK frequencies. An
`energy stored therein is dissipated. The transponder 14
`AM demodulator 68 receives this amplitude modulated
`can now respond to the interrogator 12 by using a
`signal and provides a data signal or WRITE signal to
`45
`switch 70 to connect another capacitor 72 across the
`the control circuit 40.
`resonant circuit 34. Now in the transponder's 14 re
`In order for the transponder resonant circuit 34 to be
`sponse to the interrogator 12 READ data is represented
`properly tuned to the FSK modulated signal from the
`upon the uplink signal by a first frequency that might be
`interrogator 12, the control circuit 40 closes a switch 54
`the resonant frequency of resonant circuit 34 and by a
`that connects a capacitor 56 and a resistor 58 in parallel
`SO
`second frequency that might be the resonant frequency
`with the resonant circuit 34 to form a new resonant
`of capacitor 72 in parallel with resonant circuit 34.
`circuit 60. The effect of this is to lower the frequency of
`Thus, the first frequency might represent the transmis
`the resonant circuit to f from f, where f3 is the central
`sion from the transponder to the interrogator of a digital
`frequency between the two FSK carriers f and f2. In
`ZERO and the second frequency might represent the
`order for the new resonant circuit 60 that is the parallel
`transmission of a digital ONE. This uplink is then de
`combination of the capacitors 34,56 and coil 36 to have
`modulated by the interrogator demodulator 64 and
`a sufficient bandwidth to take in both FSK carriers f
`supplied to control circuit 16 that may store the data in
`and f2, the resonant circuit 60 is damped by the resistor
`memory 20, transmit the data to a host via the connec
`58.
`tion 18, or display status information or data to an oper
`The effect of these changes is shown in FIG. 3.
`ator on a display 22.
`Graph. A shows the frequency response of the resonant
`The sole table, below, provides an overview of the
`circuits 28,34. Because these resonant circuits 28,34
`embodiments and the drawings:
`have a high Q, the graph has a very narrow base and a
`high peak. Graph B shows the effect on resonant circuit
`TABLE
`34 in closing switch 54 to form new resonant circuit 60.
`Preferred or
`Graph B is centered at f between f and f2 and has a
`Specific Term
`broad base which does have a significant frequency
`response at both fi and f2. Because the resonant circuits
`
`Drawing Generic
`Element Term
`10
`Transponder
`Arrangement
`
`55
`
`65
`
`Alternate Terms
`
`Ex.1007
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`7
`TABLE-continued
`Drawing Generic
`Preferred or
`Specific Term
`Element Tern
`Interrogator
`12
`Interrogator
`14
`Transponder Transponder
`6
`Control
`Interrogator
`Circuit
`Control Circuit
`Connection
`Host Computer
`Connection
`Interrogator
`Memory
`
`18
`
`20
`
`22
`
`24
`
`26
`28
`
`30
`32
`34
`
`36
`38
`40
`
`42
`
`44
`46
`
`48
`50
`52
`
`S4
`S6
`58
`
`60
`
`62
`
`64
`
`66
`
`67
`
`68
`
`69
`
`70
`
`72
`
`Memory
`
`Display
`
`Carrier Wave Carrier Wave
`Generator
`Generator
`Buffer
`Buffer/Amplifier
`Resonant
`Interrogator fi
`Circuit
`Resonant circuit
`Coil
`Capacitor
`Resonant
`Circuit
`Coil
`Capacitor
`Control
`Circuit
`Reference
`Line
`Signal Line
`Energy
`Storage
`Device
`Modulator
`Switch
`Resonant
`Circuit
`Switch
`Capacitor
`Damping
`Element
`Resonant
`Circuit
`Memory
`
`FSK Modulator
`
`Interrogator f.
`Resonant Circuit
`
`Resistor
`
`Transponder f3
`Resonsant Circuit
`Transponder
`Memory
`Denodulator Interrogator
`Demodulator
`Demodulator FSK
`Demodulator
`Filter
`
`Slope
`Detector
`Demodulator Transponder
`Demodulator
`
`Signal Line
`
`Switch
`
`Capacitor
`
`Slope Detector
`Output
`Transponder
`Modulator Switch
`Transponder
`Modulator
`Capacitor
`
`A few preferred embodiments have been described in
`detail hereinabove. It is to be understood that the scope
`of the invention also comprehends embodiments differ
`ent from those described, yet within the scope of the
`claims.
`For example, "microcomputer' is used in some con
`texts to mean that microcomputer requires a memory
`and "microprocessor' does not. The usage herein is that
`these terms can also be synonymous and refer to equiva
`lent things. The phrase "processing circuitry" or "con
`trol circuitry" comprehends ASICs (application spe
`cific integrated circuits), PAL (programmable array
`logic), PLAs (programmable logic arrays), decoders,
`memories, non-software based processors, or other cir
`cuitry, or digital computers including microprocessors
`and microcomputers of any architecture, or combina
`tions thereof. Memory devices include SRAM (static
`
`Alternate Terms
`Reader
`Responder, Tag
`
`SRAM, DRAM,
`EEPROM
`LCD, CRT, LED
`display, VF display
`Oscillator, Crystal
`Oscillator
`
`Antenna
`
`Antenna
`
`Transponder fi
`Resonant Circuit
`
`Microprocessor,
`Transponder
`Microcontroller
`Control Circuit
`Reference Voltage
`Reference
`Connection
`Voltage
`Reference Signal
`Signal Line
`Connection
`Storage Capacitor Rechargeable
`Battery
`
`EEPROM, SRAM,
`ROM
`
`PLL FSK
`Demodulator
`Lowpass Filter,
`Highpass Filter
`AM Demodulator
`(w/High or
`Lowpass filter)
`
`5,287, 112
`8
`random access memory), DRAM (dynamic random
`access memory), pseudo-static RAM, latches, EE
`PROM (electrically-erasable programmable read-only
`memory), EPROM (erasable programmable read-only
`memory), registers, or any other memory device known
`in the art. Words of inclusion are to be interpreted as
`nonexhaustive in considering the scope of the invention.
`Implementation is contemplated in discrete compo
`nents or fully integrated circuits in silicon, gallium arse
`nide, or other electronic materials families, as well as in
`optical-based or other technology-based forms and em
`bodiments. It should be understood that various en
`bodiments of the invention can employ or be embodied
`in hardware, software or microcoded firmware.
`While this invention has been described with refer
`ence to illustrative embodiments, this description is not
`intended to be construed in a limiting sense. Various
`modifications and combinations of the illustrative en
`bodiments, as well as other embodiments of the inven
`tion, will be apparent to persons skilled in the art upon
`reference to the description. It is therefore intended that
`the appended claims encompass any such modifications
`or embodiments.
`What is claimed is:
`1. A transponder for communicating with an interro
`gator unit, said transponder comprising:
`a) a high Q-factor resonant circuit of frequency f. for
`receiving RF powering signals;
`b) a tuning circuit which when in electrical communi
`cation with said resonant circuit is operable to form
`a lower Q-factor resonant circuit of frequency fs
`for receiving RF communications from said inter
`rogator unit;
`c) a control circuit which is in electrical communica
`tion with said high Q-factor resonant circuit and
`said tuning circuit and is operable to connect said
`tuning circuit to said high Q-factor resonant circuit
`in order to form said lower Q-factor resonant cir
`cuit, said control circuit further operable to con
`vert said RF powering signals to a DC current for
`storing energy, said control circuit still further
`operable to demodulate signals received by said
`lower Q-factor resonant circuit; and
`d) an energy storage device for storing the energy
`received in said DC current from said control cir
`cuit.
`2. The transponder of claim 1 wherein frequency f is
`the same as f.
`3. The transponder of claim 1 wherein said energy
`storage device is a storage capacitor.
`4. The transponder of claim 1 wherein said energy
`storage device is a rechargeable battery.
`5. The transponder of claim 1 wherein said high Q
`factor resonant circuit comprises the parallel combina
`tion of a coil and a capacitor.
`6. The transponder of claim 5 wherein said tuning
`circuit comprises a capacitor whose parallel combina
`tion with said high Q-factor resonant circuit forms said
`lower Q-factor resonant circuit having said resonant
`frequency f. being lower than said resonant frequency
`fl.
`7. The transponder of claim 6 wherein said tuning
`circuit comprises a damping resistor for lowering the
`Q-factor of said resonant circuit in combination with
`said tuning circuit.
`
`10
`
`15
`
`20
`
`25
`
`35
`
`40
`
`45
`
`SO
`
`55
`
`65
`
`Ex.1007
`APPLE INC. / Page 6 of 7
`
`

`

`5
`
`5
`
`30
`
`5,287, 112
`10
`combination of said switch and said capacitor being
`8. The transponder of claim 1 wherein said high Q
`parallel to said first resonant circuit.
`factor resonant circuit continues to oscillate in absence
`14. A method for communicating between an interro
`of said RF powering signals.
`gator and a transponder, said method comprising the
`9. The transponder of claim 8 and further comprising
`steps of:
`a modulator which is operable to modulate the contin
`a) sending by said interrogator a powering signal
`ued oscillations of said high Q-factor resonant circuit
`from a first high Q-factor resonant circuit having a
`with data provided to said modulator by said control
`resonant frequency of f;
`circuit.
`b) receiving by said transponder said powering signal
`10. An interrogator for communicating with a tran
`on a second high Q-factor resonant circuit having a
`sponder, said interrogator comprising:
`10
`resonant frequency of f;
`a) a programmable carrier wave generator capable of
`c) receiving by a transponder control circuit said
`providing a carrier of a first frequency, f, or a
`powering signal from said second high Q-factor
`second frequency, f2;
`resonant circuit;
`b) a first resonant circuit having a resonant frequency
`d) storing energy from said powering signal in an
`of said first frequency, f;
`energy storage device;
`c) a tuning circuit which when in electrical communi
`e) connecting by said transponder control circuit a
`cation with said resonant circuit is operable to form
`tuning circuit to said second high Q-factor resonant
`a second resonant circuit having a resonant fre
`circuit to form a lower Q-factor resonant circuit
`quency of said second frequency, f2; and
`having a resonant frequency offs;
`d) a modulator which is in electrical communication
`f) transmitting by said interrogator unit a FSK
`with said tuning circuit and said programmable
`modulated communicating signal with a center
`carrier wave generator, said modulator operable to
`frequency offs, said FSK-modulated communicat
`toggle the frequency of said carrier wave generator
`ing signal having an occupied frequency spectrum
`in response to a received data stream and to syn
`which falls substantially within the frequency re
`25
`chronously enable or disable said tuning circuit
`sponse of the lower Q-factor resonant circuit, said
`such that when said programmable carrier wave
`communicating signal generated by modifying the
`generator is providing frequency fl, said tuning
`resonant frequency of said first high Q-factor reso
`circuit is disabled and said first resonant circuit is
`nant circuit;
`tuned to said resonant frequency, f, and when said
`g) receiving by said transponder lower Q-factor reso
`programmable carrier wave generator is providing
`nant circuit said FSK-modulated communicating
`frequency, f2. said tuning circuit is enabled and said
`signal;
`second resonant circuit is tuned to said resonant
`h) demodulating by said transponder control circuit
`frequency, f2.
`said FSK modulated communicating signal;
`11. The resonant frequency of claim 10 wherein said
`i) disconnecting by said trans