Abstract: A system is described for measuring distance between an RFID reader and an RFID backscatter tag, including an adaptive linear combiner, which is a tapped delay line with controllable weights on each tap, and outputs that are summed and subtracted from a reference to produce an error signal. After a sufficient number of cycles, the weight distribution indicates the delay of the received signal with respect to the reference, and by extension determines the distance between the tag and receiver.

Abstract: A system is described for measuring distance between an RFID reader and an RFID backscatter tag, including an adaptive linear combiner, which is a tapped delay line with controllable weights on each tap, and outputs that are summed and subtracted from a reference to produce an error signal. After a sufficient number of cycles, the weight distribution indicates the delay of the received signal with respect to the reference, and by extension determines the distance between the tag and receiver.

Abstract: The a system for measuring distance between an RFID reader and tag, including an adaptive linear combiner, which is a tapped delay line with controllable weights on each tap, and outputs that are summed and subtracted from a reference to produce an error signal. After a sufficient number of cycles, the weight distribution indicates the delay of the received signal with respect to the reference, and by extension determines the distance between the tag and receiver.

Abstract: A system and method are disclosed for synchronizing two RFID readers. The system includes a modulation detector to detect a modulated signal produced by a first of the two reader and produces a synchronization signal. The second of the two readers initiates transmission of a signal in response to the synchronization signal.

Abstract: The a system for measuring distance between an RFID reader and tag, including an adaptive linear combiner, which is a tapped delay line with controllable weights on each tap, and outputs that are summed and subtracted from a reference to produce an error signal. After a sufficient number of cycles, the weight distribution indicates the delay of the received signal with respect to the reference, and by extension determines the distance between the tag and receiver.

Abstract: The a system for measuring distance between an RFID reader and tag, including an adaptive linear combiner, which is a tapped delay line with controllable weights on each tap, and outputs that are summed and subtracted from a reference to produce an error signal. After a sufficient number of cycles, the weight distribution indicates the delay of the received signal with respect to the reference, and by extension determines the distance between the tag and receiver.

Abstract: The a system for measuring distance between an RFID reader and tag, including an adaptive linear combiner, which is a tapped delay line with controllable weights on each tap, and outputs that are summed and subtracted from a reference to produce an error signal. After a sufficient number of cycles, the weight distribution indicates the delay of the received signal with respect to the reference, and by extension determines the distance between the tag and receiver.

Abstract: A system and method are disclosed for synchronizing two RFID readers. The system includes a modulation detector to detect a modulated signal produced by a first of the two reader and produces a synchronization signal. The second of the two readers initiates transmission of a signal in response to the synchronization signal.

Abstract: The system utilizes a vehicle's knowledge of its own travel speed and the time between the vehicle's intersecting two light beams that issue from the same location. The light beams can be generated using a retro-reflector illuminated by the vehicle itself, or can be generated with a split beam laser or other light source located at the road side. The vehicle detects the two beams and measures the time between the two detections. Using the vehicle travel speed, it is then possible to determine the vehicle's distance from the road side equipment and thus the lane of travel of the vehicle.

Abstract: One or more secondary data channels are added to existing RFID protocols within the existing bandwidth, data clock rate and message frame times of the protocols. An RFID system is described having at least one reader and at least one tag includes communication between the reader and the tag using a radio frequency carrier signal modulated by a modulation signal to provide a modulated carrier signal conveying digital data in either direction. The modulation signal includes a first encoded modulation signal perturbed by encoded perturbations, the first encoded modulation signal being produced from a first data string. The encoded perturbations are produced from a second data string. The modulation signal modulates the radio frequency signals to transfer data representative of the first and second data strings simultaneously between the reader and the tag. The modulation signal modulates the amplitude, phase, frequency or any combination of the radio frequency carrier signals.

Abstract: One or more secondary data channels are added to existing RFID protocols within the existing bandwidth, data clock rate and message frame times of the protocols. An RFID system is described having at least one reader and at least one tag includes communication between the reader and the tag using a radio frequency carrier signal modulated by a modulation signal to provide a modulated carrier signal conveying digital data in either direction. The modulation signal includes a first encoded modulation signal perturbed by encoded perturbations, the first encoded modulation signal being produced from a first data string. The encoded perturbations are produced from a second data string. The modulation signal modulates the radio frequency signals to transfer data representative of the first and second data strings simultaneously between the reader and the tag. The modulation signal modulates the amplitude, phase, frequency or any combination of the radio frequency carrier signals.