High speed read/write AVI system

• US 5,287,112 A
• Filed: 04/14/1993
• Issued: 02/15/1994
• Est. Priority Date: 04/14/1993
• Status: Expired due to Fees

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Schuermann, Josef H.
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US08/048,541
• Time in Patent Office: 307 Days
• Field of Search: 342/42, 342/51
• US Class Current: 342/42
• CPC Class Codes: G01S 13/758 using a signal generator powered by the interrogation signal
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer

Abstract

A transponder (14) for communicating with an interrogator (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 resonant circuit (60) of frequency f₃ for receiving RF communications from the interrogator unit. The transponder also includes a demodulator (66) which is in electrical communication with said resonant circuit (34). Additionally, 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.

Claims

1. A transponder for communicating with an interrogator unit, said transponder comprising:

a) a high Q-factor resonant circuit of frequency f₁ for receiving RF powering signals;

b) a tuning circuit which when in electrical communication with said resonant circuit is operable to form a lower Q-factor resonant circuit of frequency f₃ for receiving RF communications from said interrogator unit;

c) a control circuit which is in electrical communication 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 circuit, said control circuit further operable to convert 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 circuit.

2. The transponder of claim 1 wherein frequency f₁ is the same as f₃.

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 combination of a coil and a capacitor.

6. The transponder of claim 5 wherein said tuning circuit comprises a capacitor whose parallel combination with said high Q-factor resonant circuit forms said lower Q-factor resonant circuit having said resonant frequency f₃ being lower than said resonant frequency f₁.

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.

8. The transponder of claim 1 wherein said high Q-factor resonant circuit continues to oscillate in absence of said RF powering signals.

9. The transponder of claim 8 and further comprising a modulator which is operable to modulate the continued oscillations of said high Q-factor resonant circuit with data provided to said modulator by said control circuit.

15. The method of claim 8 and further comprising the step of sending another powering signal to said transponder prior to said responding step.

16. The method of claim 9 and further comprising the step of writing by said transponder control circuit to a transponder memory simultaneously with said step of sending another powering signal.

10. An interrogator for communicating with a transponder, said interrogator comprising:

a) a programmable carrier wave generator capable of providing a carrier of a first frequency, f₁, or a second frequency, f₂ ;

b) a first resonant circuit having a resonant frequency of said first frequency, f₁ ;

c) a tuning circuit which when in electrical communication with said resonant circuit is operable to form a second resonant circuit having a resonant frequency of said second frequency, f₂ ; and

d) a modulator which is in electrical communication with said tuning circuit and said programmable carrier wave generator, said modulator operable to toggle the frequency of said carrier wave generator in response to a received data stream and to synchronously enable or disable said tuning circuit such that when said programmable carrier wave generator is providing frequency f₁, said tuning circuit is disabled and said first resonant circuit is tuned to said resonant frequency, f₁, and when said programmable carrier wave generator is providing frequency, f₂, said tuning circuit is enabled and said second resonant circuit is tuned to said resonant frequency, f₂.

11. The resonant frequency of claim 10 wherein said programmable carrier wave generator comprises a carrier wave generator and a programmable divider whereby said first and second carrier frequencies are generated by said programmable divider as submultiples of said reference carrier under direction from said modulator.

12. The transponder of claim 10 wherein said tuning circuit comprises a capacitor whose parallel combination with said first resonant circuit forms said second resonant circuit having said second carrier frequency.

13. The transponder of claim 12 wherein said tuning circuit is enabled by providing a switch under control of said modulator in series with said capacitor, the series combination of said switch and said capacitor being parallel to said first resonant circuit.

14. A method for communicating between an interrogator and a transponder, said method comprising the steps of:

a) sending by said interrogator a powering signal from a first high Q-factor resonant circuit having a resonant frequency of f₁ ;

b) receiving by said transponder said powering signal on a second high Q-factor resonant circuit having a resonant frequency of f₁ ;

c) receiving by a transponder control circuit said powering signal from said second high Q-factor resonant circuit;

d) storing energy from said powering signal in an energy storage device;

e) connecting by said transponder control circuit a tuning circuit to said second high Q-factor resonant circuit to form a lower Q-factor resonant circuit having a resonant frequency of f₃ ;

f) transmitting by said interrogator unit a FSK-modulated communicating signal with a center frequency of f₃, said FSK-modulated communicating signal having an occupied frequency spectrum which falls substantially within the frequency response of the lower Q-factor resonant circuit, said communicating signal generated by modifying the resonant frequency of said first high Q-factor resonant circuit;

g) receiving by said transponder lower Q-factor resonant circuit said FSK-modulated communicating signal;

h) demodulating by said transponder control circuit said FSK modulated communicating signal;

i) disconnecting by said transponder control circuit said tuning circuit to re-establish said second high Q-factor resonant circuit; and

j) responding to said interrogator by said transponder by modulating said second high Q-factor resonant circuit.