Swept frequency electronic article surveillance system having enhanced facility for tag signal detection

摘要

A periodic pulse discrimination system particularly suitable for use with electronic article surveillance systems is capable of detecting valid tag pulses while discriminating against periodic pulses caused by resonances and interfering carriers as well as random noise. Circuitry that determines the periodicity of a pulse signal and is responsive to amplitude differences between successive detected pulses controls an adaptive threshold and sampling window to discriminate against signals having an incorrect periodicity and an inadequate envelope rise time. A notch circuit notches out pulse trains that have the correct or substantially correct periodicity but persist for a longer time period than the time period required for a tag to pass through the detection zone.