Abstract: A reader for an RFID system has an exciter circuit for generating an excitation signal and a feedback circuit coupled to the exciter circuit for automatically tuning the exciter circuit. The exciter circuit has at least one retunable component providing the exciter circuit with adjustable component values and a plurality of signal generating states. The exciter circuit is initially tuned to a first signal generating state, but is retunable to additional signal generating states by adjusting the component value of the retunable component. The feedback circuit includes a circuit evaluator coupled to the exciter circuit for determining a value of an operational parameter of the exciter circuit. A decision-making circuit is coupled to the circuit evaluator for formulating a decision in response to the value of the operational parameter.

Abstract: A reader unit for use in a radio frequency identification (RFID) system delays the initiation of an interrogation operation when potentially interfering radio frequency (RF) energy is detected within an operational frequency range of the system. The reader unit waits a quasi-random period of time after the detection and then senses the spectral environment again to determine whether the energy is still present. If the energy is still present, the reader unit waits another quasi-random period and the process repeats. If there is no energy present or the energy is below a threshold value, the reader unit immediately initiates the interrogation operation. By delaying the initiation of the interrogation operation until the operative frequency range is free of potential interferers, the likelihood of harmful interference effects is significantly reduced.