NEXUS AM Deactivator
AM operating principle
v2.1
Page 12 of 26
5
AM operating principle
The NEXUS AM Deactivator operates on the pulse-listening principle. Using the zero
crossing of the 50Hz mains frequency as a trigger, a short burst of 58kHz signal is
transmitted and a receiver window is ‘opened’ after the transmission burst has stopped.
If a label/tag was present within detection range during the transmission burst, the
resonance of this label/tag will be detected in the receiver window and a deactivation
burst is triggered.
A single 50Hz mains frequency cycle is dived into three phases; phase A, B and C. Each
phase covers 1/3 of the 50Hz cycle duration.
A noise reference window is opened to detect the environmental noise. This signal is
compared with the signal received in the receiver window and allows the software to
properly distinguish a tag signal from a noise signal.
Figure 5
shows the AM operating principle (at 50Hz, with a default delay of 200μs) during
one 50Hz cycle.
Figure 5: AM operating principle
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Phase C
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