Abstract: Aspects and features of this disclosure include operating an RFID reader to identify targeted tags and background tags from among a population of RFID tags. The background tags are then monitored by reading the background tags at a background rate and the targeted tags are tracked by reading the targeted tags at an enhanced rate. The enhanced rate is significantly greater than the background rate. The tags from a large population can be segregated into the two subpopulations based on read measurements stored in a tag database. A tag may become “targeted” by moving towards or appearing near a portal of interest. Tag detection, and therefore an alarm message or some other desired result, can be provided quickly due to the higher, enhanced read rate being applied to the targeted tags.

Abstract: Aspects and features of this disclosure use an RFID tag or other transponder embedded in an RFID antenna to provide a smart RFID antenna. The smart antenna can have a unique identity, at least in its system environment, and the identity can be readable by the RFID reader through a large insertion loss, providing the reader with the capability to accurately detect the antenna. A method of detecting a smart RFID antenna includes applying a transmit signal at a configured power level, and selectively increasing the configured power level of the transmit signal until detection. In some examples, the process also includes storing location and other useful information for the RFID antenna. In some examples, any or all of this location or other information can be written to a memory in the RFID antenna in addition to a database in the system.

Abstract: Aspects and features of this disclosure include an RFID reader with an integrated noise-canceling RFID receiver. The receiver includes a baseband converter configured to receive an RFID signal and a cancelation signal. The baseband converter acts as a received signal mixer and also provides noise cancelation using the cancelation signal. A modulated feedback signal completes closed-loop signal path that automatically provides noise control, both noise shaping and noise filtering, improving the receiving performance by efficiently reducing or eliminating noise that would otherwise be produced by the transmitter of the RFID reader.

Abstract: Certain aspects and features of the present disclosure relate to a system that improves the localization and interrogation of RFID tags in an environment with many tags. Suppression antennas are used to create suppression zones around large background tag populations around or near the portal. The suppression antennas quiet the tags in a suppression zone to prevent erroneous tracking of these tags at nearby RFID portal antennas. Optionally, a suppression RFID reader can communicate with neighboring readers, including a portal RFID reader, to provide information that can be used for expedited tracking of a tag that may be approaching an RFID portal.

Abstract: Aspects and features of this disclosure include operating an RFID reader to identify targeted tags and background tags from among a population of RFID tags. The background tags are then monitored by reading the background tags at a background rate and the targeted tags are tracked by reading the targeted tags at an enhanced rate. The enhanced rate is significantly greater than the background rate. The tags from a large population can be segregated into the two subpopulations based on read measurements stored in a tag database. A tag may become “targeted” by moving towards or appearing near a portal of interest. Tag detection, and therefore an alarm message or some other desired result, can be provided quickly due to the higher, enhanced read rate being applied to the targeted tags.

Abstract: Aspects and features of this disclosure include a radio frequency identification (RFID) antenna multiplexer. An RFID reader and an RFID system using the RFID antenna multiplexer are also disclosed. The multiplexer includes multiple output ports. Each of at least some of the output ports is connectable to an antenna or another device. In some aspects, a logic circuit in the multiplexer is configured to cause a radio frequency (RF) switch to select an output port from the multiple output ports to connect to the input port based upon a reduction in RF power at the input port. In some aspects, the multiplexer includes an energy harvester connected to the input port to harvest signal energy from the RFID reader and a storage device connected to the energy harvester to store the signal energy and supply power to the multiplexer using the signal energy.

Abstract: Aspects and features of this disclosure include a radio frequency identification (RFID) antenna multiplexer. An RFID reader and an RFID system using the RFID antenna multiplexer are also disclosed. The multiplexer includes multiple output ports. Each of at least some of the output ports is connectable to an antenna or another device. In some aspects, a logic circuit in the multiplexer is configured to cause a radio frequency (RF) switch to select an output port from the multiple output ports to connect to the input port based upon a reduction in RF power at the input port. In some aspects, the multiplexer includes an energy harvester connected to the input port to harvest signal energy from the RFID reader and a storage device connected to the energy harvester to store the signal energy and supply power to the multiplexer using the signal energy.

Abstract: A polar transmitter for an RFID reader and a system using the polar transmitter are disclosed. An RFID system according to at least some embodiments of the invention includes a polar transmitter, a receiver to receive responses from RFID tags, and a coupler connected to the polar transmitter, the receiver and one or more antennas. In at least some embodiments, the polar transmitter of the RFID system includes an envelope amplifier and a power amplifier. In some examples, a polar transmitter includes direct conversion of baseband data to provide angle modulation plus drive modulation. In addition to the envelope amplifier and power amplifier, the polar transmitter in such an example includes a quadrature modulator connected to the power amplifier to provide modulation for the transmitter output signal using a Cartesian input signal.

Abstract: An RF system using amplitude modulation (AM) with orthogonal offset is disclosed. The orthogonal offset generator can shift the AM signal trajectory away from the origin while maintaining the time domain requirements for an RFID signal, such as waveform edge rise and fall times. In some embodiments stored waveforms incorporating the controlled orthogonal offset are used to synthesize a sequence of symbols. The stored waveforms may also include nonlinear and/or linear predistortion to reduce computational complexity. The waveforms can be represented in Cartesian coordinates for use in a direct conversion transmitter or polar coordinates for use in a polar modulation transmitter. An RFID system can also include a receiver to receive incoming RFID signals.