Read/write transponder arrangement and method of communication

• US 5,548,291 A
• Filed: 06/07/1995
• Issued: 08/20/1996
• Est. Priority Date: 11/25/1992
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments Deutschland Gesellschaft Mit Beschrã¤Nkter Haftung (Texas Instruments, Inc.)
• Inventors: Sellmeir, Martin, Meier, Herbert
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/475,115
• Time in Patent Office: 440 Days
• Field of Search: 342/42, 342/44, 342/50, 342/51, 340/825.54, 340/825.32, 340/825.34
• US Class Current: 340/10.34
• 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 arrangement is described having an interrogator unit (10) which transmits at least one RF programming sequence and at least one RF interrogation pulse. The responder unit (12) includes a responder unit receiver (130) for receiving data transmitted by the RF programming sequence from the interrogator unit (10). The responder unit (12) then upon receipt of the RF interrogation pulse transmits data, which may have been modified by the programming sequence from the interrogator unit (10), back to the interrogator unit (10) in the form of a modulated RF carrier. The responder unit (12) further comprises a responder unit energy accumulator (136) which stores energy contained in the RF interrogation pulse and a responder unit end of burst detector (142) which upon detection of a decreasing power level of the RF interrogation pulse sends a RF threshold signal. Further contained within the responder unit (12) is a responder unit RF carrier wave generator (130) operating with the frequency contained in the RF interrogation pulse, which is excited upon receipt of a signal from the pluck circuit (196). The responder unit (12) further comprises a responder unit circuitry means (198,200) for providing from the output signal of the RF carrier wave generator a control signal which is utilized to maintain the RF carrier wave and to modulate the RF carrier to be sent back with the stored data.

Claims

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

a. storing energy in a transponder energy accumulator in a contactless fashion by RF energy transmitted from said interrogator unit to said transponder;

b. transmitting at least one RF programming sequence from said interrogator to said transponder, said RF programming sequence comprising a first set of data pulses having at least a first and a second state, at least one of said first and second states having an "on" and an "off" phase, the "on" phase of said data pulse having a first modulation characteristic, and the "off" phase of said data pulse having a second modulation characteristic and having a duration of less than the "Pre-Bit-Time" that initiates a transponder read period;

c. receiving at said transponder said first set of data pulses; and

d. transmitting a pause from said interrogator to said transponder, said pause comprising a signal having said second modulation characteristic, but having a duration approximately equal to the "Pre-Bit-Time" whereby said transponder is notified of the beginning of the read period.

2. The method of claim 1 wherein said first and second modulation characteristics are first and second amplitudes of said signal.

3. The method of claim 1 wherein said second amplitude is the absence of modulating signal altogether.

4. The method of claim 3 wherein said transponder detects the beginning of the read period by detection of a decreasing power level in the transponder energy accumulator, which accompanies the "Pre-Bit-Time" pause transmitted by the interrogator.

5. The method of claim 1 and further comprising the step of activating an RF carrier wave in said transponder upon detection of the beginning of said read period.

6. The method of claim 5 and further comprising the step of modulating said RF carrier wave with read data.

7. The method of claim 6 and further comprising the step of transmitting said modulated RF carrier wave from said transponder to said interrogator.

8. The method of claim 1 wherein said transponder has a counter which will begin to decrement from a set value when said transmissions from said interrogator are in an "off" phase.

9. The method of claim 8 wherein said counter enables an RF response from said transponder to said interrogator upon said counter fully decrementing from its set value, and wherein if said counter does not decrement fully during the "off" phase, the counter is reset during the following "on" phase.

10. The method of claim 8 wherein the "Pre-Bit-Time" is greater than the amount of time required for the counter to fully decrement from its set value.

11. The method of claim 8 wherein said counter is a shift register, wherein the output of said shift register serves to modulate an RF carrier wave in said transponder when the output of said shift register is asserted, and wherein the output of said shift register is not asserted until said shift register has been clocked for a time period greater than said "Pre-Bit-Time".

12. The method of claim 1 wherein said first and second states of said RF programming sequence each have an "on" and an "off" phase, where the duration of the "off" phase during said first state differs from said second state and wherein the "off" phase in each of said states is less than the "Pre-Bit-Time" that initiates said transponder read period.

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

a. storing energy in a transponder energy accumulator in a contactless fashion by RF energy transmitted from said interrogator unit to said transponder;

b. transmitting at least one RF programming sequence from said interrogator to said transponder, said RF programming sequence comprising a first set of data pulses having at least a first and a second state, at least one of said first and second states having an "on" and an "off" phase, the "on" phase being characterized by the presence of signal, and the "off" phase being characterized by the absence of signal, said "off" phase having a duration of less than a "Pre-Bit-Time," which initiates a transponder read period;

c. receiving at said transponder said first set of data pulses; and

d. transmitting a pause from said interrogator to said transponder, said pause being characterized by an absence of signal and but having a duration of the "Pre-Bit-Time" whereby said transponder is notified of the beginning of the read period;

e. decrementing a counter in said transponder from a set value, the set value being such that said counter will fully decrement if the duration of a received "off" phase is equal to the "Pre-Bit-Time," but if the duration of the "off" phase is substantially less than the "Pre-Bit-Time" said counter will be reset to its fixed value.