Abstract: Apparatus and methods are described which are useful for determining a location characteristic between an RFID tag and an RFID tag reader or a second RFID tag. In various embodiments, signals backscattered from a singulated tag over a range of frequencies are evaluated for in-phase I and in-quadrature Q signal components. The I-Q data is processed to determine phase delay angles associated with each signal frequency. The phase delay data can be processed by a sum of squared errors method or Fourier transform method to determine a distance to the singulated tag. The methods can also be used to determine any of a location, a radial velocity, a directional velocity of the singulated tag, and proximity of the singulated tag to a second tag.

Abstract: An RFID reader analog front end architecture employs multiplexed use of a single analog to digital converter in order to digitize the inphase and quadrature components of the incoming signal from the reader's receiving antenna. The Type 1 architecture includes an analog I/Q switch that controls which of the baseband signals will be digitized by a single Analog to Digital Converter. In the Type 2 architecture, the I/Q switch is moved so that it is directly adjacent to the receive mixers, requiring only one antialiasing filter block and gain block. In the Type 3 architecture, one mixer and its associated filtering chain are eliminated. The Type 4 architecture provides for selection of transmitter phase basis by means of an I/Q switch operating under control of the DSP that phase-shifts the transmitter with respect to the receiver.

Abstract: Systems and methods for placing RFID tags on objects are shown and described. The method includes scanning an object and analyzing one or more reflected signals from the to determine a suggested location for placement of an RFID tag. The scan can be accomplished using a scanning device having an antenna that operates in the near field of the object to measure at least one RF property of the reflected signal from the object.

Abstract: A transceiver circuit includes an input to receive an RF mode control signal, multiple ports, and path circuitry disposed between the multiple ports. The path circuitry can be configured to create different low impedance conductive paths between the multiple ports depending on a state of the RF mode control signal. For example, depending on a mode as specified by the RF mode control signal, the transceiver circuit and corresponding path circuitry enables a half-duplex mode and a full-duplex mode.

Abstract: A dynamically reconfigurable antenna system for an RFID (Radio Frequency Identification) reader/encoder includes a plurality of antenna elements; and a mechanism constructed and adapted to dynamically and selectively configure said plurality of antenna elements during operation thereof. The antenna elements may be arranged in a pattern of conductive areas, and each antenna element is switchably connectable to ground or to a transmission line connectable to the RFID reader/encoder. Each antenna element may be square, rectangle, circular, or diamond shaped. The antenna elements may located on an inner layer of the multi-layer printed circuit and wherein regions above the antenna elements are a dielectric layer or a slot aperture. The antenna system may be incorporated into an RFID encoder/reader.

Abstract: Apparatus and methods are described which are useful for determining a location characteristic between an RFID tag and an RFID tag reader or a second RFID tag. In various embodiments, signals backscattered from a singulated tag over a range of frequencies are evaluated for in-phase I and in-quadrature Q signal components. The I-Q data is processed to determine phase delay angles associated with each signal frequency. The phase delay data can be processed by a sum of squared errors method or Fourier transform method to determine a distance to the singulated tag. The methods can also be used to determine any of a location, a radial velocity, a directional velocity of the singulated tag, and proximity of the singulated tag to a second tag.

Abstract: Apparatus and methods are described which are useful for determining a distance between an RFID tag and an RFID tag reader. In various embodiments, signals backscattered from a singulated tag over a range of frequencies are evaluated for in-phase I and in-quadrature Q signal components. The I-Q data is processed to determine phase delay angles associated with each signal frequency. The phase delay data can be processed by a sum of squared errors method or Fourier transform method to determine a distance to the singulated tag. The methods can also be used to determine any of a location, a radial velocity, a directional velocity of the singulated tag, and proximity of the singulated tag to a second tag.

Abstract: Systems and methods for providing active noise cancellation in an RFID tag reader are described. In one aspect, the method features increasing the signal-to-noise-plus-interference ratio of a radio frequency tag response. The method includes receiving, with a first antenna element of a radio frequency tag reader, a radio frequency tag response having a noise-plus-interference portion and a response portion, receiving a noise-plus-interference signal with a second antenna element of the radio frequency tag reader, and processing the received radio frequency tag response and the noise-plus-interference signal to increase a signal-to-noise-plus-interference ratio of the received radio frequency tag response.

Abstract: Systems and methods for placing RFID tags on objects are shown and described. The method includes scanning an object and analyzing one or more reflected signals from the to determine a suggested location for placement of an RFID tag. The scan can be accomplished using a scanning device having an antenna that operates in the near field of the object to measure at least one RF property of the reflected signal from the object.

Abstract: A circuit for transmitter-receiver isolation that is useful in a monostatic (combined transmitting and receiving) antenna configuration is shown and described. In addition, methods and systems are shown for automatically adjusting the circuit in response to changes in antenna configuration, external signal reflectors, and jamming energy (e.g., self jammer energy) by adjusting the circuit to tune out these sources of jammer energy to yield an increase in RFID reader receiver sensitivity when compared to measurements of the receiver sensitivity when the jammer energy is not present.

Abstract: An RFID (Radio Frequency Identification) reader system has a sensor system associated with its antenna system. The sensor system determines one or more of an orientation, position, velocity, motion and acceleration of antenna elements in said antenna system. The reader system uses the sensor data to control the antenna system based.

Abstract: A dynamically reconfigurable antenna system for an RFID (Radio Frequency Identification) reader/encoder includes a plurality of antenna elements; and a mechanism constructed and adapted to dynamically and selectively configure said plurality of antenna elements during operation thereof. The antenna elements may be arranged in a pattern of conductive areas, and each antenna element is switchably connectable to ground or to a transmission line connectable to the RFID reader/encoder. Each antenna element may be square, rectangle, circular, or diamond shaped. The antenna elements may located on an inner layer of the multi-layer printed circuit and wherein regions above the antenna elements are a dielectric layer or a slot aperture. The antenna system may be incorporated into an RFID encoder/reader.

Abstract: An RFID (Radio Frequency Identification) reader system has a sensor system associated with its antenna system. The sensor system determines one or more of an orientation, position, velocity, motion and acceleration of antenna elements in said antenna system. The reader system uses the sensor data to control the antenna system based.

Abstract: An RFID protection scheme includes monitoring an output signal of a least one receiver mixer of the reader, and, based at least in part on said monitoring, when said output signal exceeds a predetermined threshold, performing one or more of the following: removing an RF signal from a transmitter power amplifier (PA); removing a bias from the PA; causing a protection switch to divert transmitter power away from an antenna circuit; and signaling a processor to reduce transmitter power.

Abstract: A method of operating a plurality of Radio Frequency Identification (RFID) readers includes operating the readers according to a spatial-division and time-division synchronization schedule. Each reader may be associated with a reader group, and the schedule may specify a duration of time that all of the readers in a group may be active. Readers in different reader groups may be scheduled independent of readers in other reader groups.

Abstract: A simulated RFID tag may be combined with other such tags to form a population of simulated tags. A method of testing an RFID reader includes providing at least one population of simulated RFID tags; configuring tags in the at least one population of simulated RFID tags; and querying the at least one population of simulated RFID tags with the RFID reader. The simulated RFID tags may be configured by assigning arbitrary static IDs to at least some of the simulated RFID tags; assigning a sequence of tag IDs to at least some of the simulated RFID tags; assigning a sequence of time-varying IDs to at least some the population of simulated RFID tags; and assigning arbitrary timing/persistence to at least some of the simulated RFID tags.