Abstract: A system and method for providing a fuel dispenser with radio frequency customer identification capabilities. The system and method determines whether a transponder containing customer identification data is within range of a dispenser, the dispenser requiring activation by the customer to initiate a transaction and including a reader associated therewith for emitting radio frequency signals within the dispenser range, and for receiving customer identification data from the transponder responsive to the emitted radio frequency signals received by the transponder. When the transponder is within range of the dispenser, an in-range indication is provided to the customer. A determination is made whether the dispenser has been activated by the customer following a determination that the transponder is within the dispenser range.

Abstract: A real-time location system for identifying and locating tagged items. The system may include an identification protocol that tracks in-network transponders and assigns dynamic in-network identification numbers to in-network transponders. The system includes a locator function that employs time-of-arrival analysis. Rather than attempt to synchronize the time base at each reader, the system and process eliminate the need to sync the readers and also eliminate the impact of differential receive delays in the respective readers. Both the transponder and a master reader transmit locate signals, which are measured at slave readers. The system relies on differences in time-of-arrival of the two signals at the respective slave readers to determine the likely location of the transponder.

Abstract: A method for use in a RFID reader, the method comprising providing an output signal from an amplifier of a transmitter, attenuating the output signal via a step attenuator, detecting and comparing the attenuated output signal to a reference value, and adjusting power to the amplifier until the attenuated output signal is substantially equal to the reference value. The attenuated output signal drives a local oscillator signal of a receiver thereby canceling noise generated by the transmitter in the receiver.

Abstract: An RFID circuit comprises an RF carrier signal source, a hybrid coupled to the RF carrier signal source operable to generate an in-phase and a quadrature phase component of the RF carrier signal, a switch coupled to the hybrid operable to pass one of the in-phase and quadrature phase components of the RF carrier signal to its output, and a mixer coupled to the output of the switch operable to multiply one of the in-phase and quadrature phase component of the carrier signal and a received modulated carrier signal and generate a baseband signal.

Abstract: An RFID circuit comprises an RF carrier signal source, and a hybrid coupled thereto operable to generate first, second and third phase-shifted RF carrier signals. The circuit further comprises first, second, and third mixers coupled to the hybrid each operable to multiply one of the first, second and third respective carrier signals and a backscattered modulated carrier signal and generate first, second and third baseband signals, respectively. The circuit further comprises first, second, and third delay lines respectively coupled to the first, second, and third mixers and operable to generate first, second and third delayed baseband signals. The circuit further comprises logic coupled to the first, second, and third mixers and the first, second, and third delay lines and operable to detect substantially simultaneous data transitions in at least two of the first, second, and third baseband signals, and generating a reconstructed signal having a data transition in response thereto.

Abstract: An RFID circuit comprises an RF carrier signal source, a hybrid coupled to the RF carrier signal source operable to generate an in-phase and a quadrature phase component of the RF carrier signal, a switch coupled to the hybrid operable to pass one of the in-phase and quadrature phase components of the RF carrier signal to its output, and a mixer coupled to the output of the switch operable to multiply one of the in-phase and quadrature phase component of the carrier signal and a received modulated carrier signal and generate a baseband signal.

Abstract: An RFID circuit comprising an RF carrier signal source, a hybrid coupled to the RF carrier signal source operable to generate first and second phase-shifted RF carrier signals, first and second mixers coupled to the hybrid each operable to multiply a respective one of the first and second carrier signals and a received backscattered modulated carrier signal and generate first and second baseband signals, respectively, and first logic coupled to the first and second mixers operable to select one of the first and second baseband signals having a larger amplitude as a demodulated RFID output signal.

Abstract: An RFID circuit comprises an RF carrier signal source, a hybrid coupled to the RF carrier signal source operable to generate an in-phase and a quadrature phase component of the RF carrier signal, a switch coupled to the hybrid operable to pass one of the in-phase and quadrature phase components of the RF carrier signal to its output, and a mixer coupled to the output of the switch operable to multiply one of the in-phase and quadrature phase component of the carrier signal and a received modulated carrier signal and generate a baseband signal.

Abstract: A method for use in a RFID reader, the method comprising providing an output signal from an amplifier of a transmitter, attenuating the output signal via a step attenuator, detecting and comparing the attenuated output signal to a reference value, and adjusting power to the amplifier until the attenuated output signal is substantially equal to the reference value. The attenuated output signal drives a local oscillator signal of a receiver thereby canceling noise generated by the transmitter in the receiver.

Abstract: An RFID reader, comprising a high-efficiency Class-C power amplifier having an input, an output, and a supply voltage, a modulator coupled to the supply voltage of the Class-C power amplifier, and an RF carrier signal coupled to the input of the Class-C power amplifier. The modulator changes the supply voltage of the Class-C power amplifier resulting in highly controlled amplitude modulation of the RF carrier signal at the output of the Class-C power amplifier.

Abstract: An antenna comprises a square patch element having first and second feed points and lying in a first plane, the first feed point being disposed near a first edge of the square patch element and substantially bisecting the first edge, and the second feed point being disposed near a second edge of the square patch element and substantially bisecting the second edge. The antenna further comprises a feed structure lying in a second plane parallel with the first plane and having a first segment coupled between a signal point and the first feed point, and a second segment coupled between the signal point and the second feed point, where the first and second segments of the feed structure have unequal lengths. The antenna further comprises a ground plane supporting the feed structure and square patch element.

Abstract: An RFID circuit comprising an RF carrier signal source, a hybrid coupled to the RF carrier signal source operable to generate first and second phase-shifted RF carrier signals, first and second mixers coupled to the hybrid each operable to multiply a respective one of the first and second carrier signals and a received backscattered modulated carrier signal and generate first and second baseband signals, respectively, and first logic coupled to the first and second mixers operable to select one of the first and second baseband signals having a larger amplitude as a demodulated RFID output signal.

Abstract: An RFID circuit comprises an RF carrier signal source, and a hybrid coupled thereto operable to generate first, second and third phase-shifted RF carrier signals. The circuit further comprises first, second, and third mixers coupled to the hybrid each operable to multiply one of the first, second and third respective carrier signals and a backscattered modulated carrier signal and generate first, second and third baseband signals, respectively. The circuit further comprises first, second, and third delay lines respectively coupled to the first, second, and third mixers and operable to generate first, second and third delayed baseband signals. The circuit further comprises logic coupled to the first, second, and third mixers and the first, second, and third delay lines and operable to detect substantially simultaneous data transitions in at least two of the first, second, and third baseband signals, and generating a reconstructed signal having a data transition in response thereto.

Abstract: An RFID circuit comprises an RF carrier signal source, a hybrid coupled to the RF carrier signal source operable to generate an in-phase and a quadrature phase component of the RF carrier signal, a switch coupled to the hybrid operable to pass one of the in-phase and quadrature phase components of the RF carrier signal to its output, and a mixer coupled to the output of the switch operable to multiply one of the in-phase and quadrature phase component of the carrier signal and a received modulated carrier signal and generate a baseband signal.

Abstract: Apparatus and methods for locating an RFID transponder in space is described. The invention includes an RFID transponder for broadcasting identification data and a plurality of antenna for receiving identification data broadcast by the RFID transponder. The plurality of antenna are associated with the plurality of support members or shelves and control circuitry connected to the plurality of antenna determines which of the plurality of antenna receives identification information broadcast from the RFID transponder to determine the location of the transponder.