Radio frequency identification reader antenna having a dynamically adjustable q-factor

Abstract

Turning now to the drawings, systems and methods for reading RFID transponders utilizing readers in which the Q-factor of the resonant antenna of the reader shifts over the course of the reader's interrogation cycle in response to the detection of data from FDX and HDX RFID transponders in accordance with embodiments of the invention are illustrated. One embodiment having a dynamically adjustable Q-factor, wherein the reader transmits an activation signal configured to activate half duplex and full duplex transponders includes a signal source configured to drive a resonant antenna and a dynamic switching circuit configured to set the Q-factor of the resonant antenna to a first value during the transmission of the activation signal. In addition, the dynamic switching circuit is configured to set the Q-factor of the resonant antenna to a second value below the first value during and/or in response to detection of a data signal from a full duplex transponder, the dynamic switching circuit is also configured to set the Q-factor of the resonant antenna to a third value below the second value when the RFID reader is not transmitting the activation signal, and the resonant antenna is multi-filar and the dynamic switching circuit is configured to control the Q-factor of the multi-filar resonant antenna by controlling the filars that are incorporated into the resonant antenna circuit.