Patent ID: 7696877

Claim:
A method of operation of a transponder detection device, the method comprising: during each of a plurality of detection cycles, receiving electromagnetic signals during a noise detection portion of the detection cycle; determining a value indicative of a noise level based at least in part on the electromagnetic signals received during the noise detection portion of the detection cycle; adjusting a detection threshold based at least in part on at least one determined value indicative of the noise level; emitting at least one electromagnetic interrogation signal during a transmit portion of the detection cycle; receiving electromagnetic signals during a receive response portion of the detection cycle that follows the transmit portion of the detection cycle; and determining the presence or absence of a transponder based at least in part on the electromagnetic signals received during the detection cycle and the adjusted detection threshold, wherein determining a value indicative of a noise level based at least in part on the electromagnetic signals received during the noise detection portion of the detection cycle includes averaging the values indicative of the noise level over each of the detection cycles, and wherein adjusting a detection threshold based at least in part on the determined value indicative of the noise level includes adjusting the detection threshold based at least in part on an average of the values indicative of the noise levels over multiple samples or measurements of at least one of the detection cycles, wherein averaging a sufficient number of the values indicative of the noise level over each of the detection cycles includes averaging the values indicative of the noise level over each of the detection cycles sufficient to provide a signal to noise ratio greater than approximately 1.93.