Cross Point b.v. CP301MAXRXA Manual De Usuario
Technical Manual AM Systems
AM operating principle
v4.4
Page 12 of 72
5
AM operating principle
The AM system 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.
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 tag was present within detection range during the transmission burst, the resonance
of this tag will be detected in the receiver window and an alarm will be triggered.
of this tag will be detected in the receiver window and an alarm will be 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.
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.
compared with the signal received in the receiver window and allows the software to
properly distinguish a tag signal from a noise signal.
Figure 1 shows the AM operating principle (at 50Hz, with
a default delay of 200μs) during
one 50Hz cycle.
Figure 1: AM operating principle
Tr
a
a
n
s
mi
s
s
s
ion
b
b
u
rs
t
R
e
c
e
iv
e
r w
ind
o
o
w
R
e
fe
re
n
c
e
w
in
d
o
w
Phase C
Phase B
Phase A