APPARATUS AND METHOD FOR DETECTING MAGNETIC ELECTRONIC ARTICLE SURVEILLANCE MARKERS

摘要

Method and apparatus for detecting the presence of a magnetic marker in a dual frequency interrogation zone. A dual frequency field is generated to produce an interrogation zone wherein the higher frequency is substantially higher than the lower frequency. The signal generated by the magnetic marker is detected filtered and amplified. Time windows are selected at the expected pulse locations of the signal. The signals detected at the time windows are multiplied by a window function. The product resulting therefrom is averaged to produce a demodulated signal and the presence of a marker in the interrogation zone is determined by detecting the demodulated signal at the lower frequency of the dual frequency interrogation zone.