Transponders, Interrogators, systems and methods for elimination of interrogator synchronization requirement

A Radio Frequency Identification (RFID) system, said system comprising an interrogator and a transponder wherein said interrogator and transponder are in wireless communication with each other through RF interrogations by said interrogator to said transponder and through RF responses from said transponder to said interrogator, wherein:

• a) said interrogator comprises
• i) an RF oscillator,
• ii) a programmable divider in electrical communication with said RF oscillator and operable to selectively divide the oscillations thereof such that a first division factor causes a communication frequency signal to be output from said divider and a second division factor causes a factor causes a powering frequency signal to be output from said divider,
• iii) a first tuned circuit in electrical communication with said programmable divider, said first tuned circuit having a resonant frequency of said powering frequency, said first tuned circuit operable to send a powering burst,
• iv) a second tuned circuit in electrical communication with said programmable divider, said second tuned circuit having a selected bandwidth encompassing an RF response about said communication frequency, said selected bandwidth not substantially overlapping said powering frequency,
• v) a transmit antenna in electrical communication with said first tuned circuit and operable to transmit said powering burst as a wireless signal to said transponder and to transmit said RF interrogation thereto,
• vi) a receive antenna in electrical communication with said second tuned circuit, said receive antenna operable to receive said RF response,
• vii) a demodulator for receiving said RF response from said second tuned circuit and providing RF response data therefrom, and
• viii) a controller in electrical communication with said programmable divider, said demodulator, and said tuned circuits, said controller operable to enable said first tuned circuit to send said powering burst during a first time period and to enable said demodulator in electrical communication with said second tuned circuit to demodulate RF response data from said RF response during a second time period, said controller further operable to receive said RF response data from said demodulator;
• and
• b) a transponder, said transponder having
• i) a tuned circuit operable to oscillate with a carrier having a frequency equal to the resonance frequency of said tuned circuit,
• ii) a tuning circuit in electrical communication with said tuned circuit for modifying the frequency characteristics of said tuned circuit such that the tuned circuit is operable to be tuned during said powering burst to said powering frequency and to be tuned during said RF response to said communication frequency, said powering signal causing tuning circuit to oscillate with a carrier having said powering frequency,
• iii) a demodulator in electrical communication with said tuned circuit for receiving said RF interrogation therefrom and for demodulating interrogation data from said RF interrogation,
• iv) a modulator in electrical communication with said tuned circuit for modulating said RF response data upon said carrier, and
• v) a controller in electrical communication with said modulator, said demodulator, and said tuning circuit, said controller operable to control said tuning circuit to modify the frequency characteristics of said tuned circuit, to receive said interrogation data from said demodulator, and to provide said RF response data to said modulator.

A method for communicating between an interrogator and transponder, the method comprising the steps of:

• a) tuning a transponder tuned circuit to a powering frequency;
• b) sending a powering burst of said powering frequency to said transponder by an interrogator tuned circuit, said powering burst causing said tuning circuit to oscillate with a carrier having said powering frequency;
• c) rectifying said powering burst in said transponder to supply power to the operating circuitry thereof;
• d) upon termination of said powering burst, tuning said transponder to have a communicating frequency whereby the oscillation of said carrier will be at said communicating frequency, further selecting the bandwidth of said tuned circuit to be a selected width and not substantially encompassing said powering frequency;
• e) entering a Read mode during which said modulator modulates data upon said carrier to form an RF response, said RF response having a bandwidth such that a substantial portion thereof lies within the bandwidth of said tuned circuit;
• f) transmitting said RF response by said tuned circuit in electrical communication with said modulator;
• and
• g) receiving by a receiver circuit said RF response.

A transponder for a Radio Frequency Identification (RFID) system using an interrogator which sends RF interrogations to said interrogator and receives RF responses therefrom, said transponder comprising:

• a) a tuned circuit operable to oscillate with a carrier having a frequency equal to the resonance frequency of said tuned circuit;
• b) a tuning circuit in electrical communication with said tuned circuit for modifying the frequency characteristics of said tuned circuit such that the tuned circuit is operable to be tuned during said a powering burst to a powering frequency and to be tuned during said RF response to a modulation frequency;
• and
• c) a modulator in electrical communication with said tuned circuit for modulating the carrier therein with said RF response data to form said RF response, said modulated RF response not substantially overlapping said powering frequency.

An interrogator for sending RF interrogations and receiving RF responses from a transponder, said interrogator comprising:

• a) a carrier wave generator for generating a powering burst of a powering frequency;
• b) a demodulator for demodulating response data from an RF response from a transponder, said RF response being a wireless, modulated carrier signal;
• c) a tuned circuit in electrical communication with said demodulator, said second tuned circuit having a selected bandwidth about a communication frequency, said selected bandwidth not substantially overlapping said powering frequency and encompassing the bandwidth of the modulated carrier of said RF response;
• and
• d) a controller in electrical communication with said receiver circuit, said tuned circuit, and said demodulator, said controller operable to enable said carrier wave generator to send said powering burst during a first time period and to enable said demodulator in electrical communication with said tuned circuit to receive said RF response during a second time period.