User's Manual

10.3.5 ACP/ARP encoder
GTX-A188
Optical quadrature azimuth and heading
line encoder
The sealed ACP/ ARP encoder is situated inside the gearbox housing and is located around the
rotating joint shaft. It outputs 1024 pulses (two azimuth streams 90deg phase shifted and two inverse
azimuths) per revolution.
The encoder also outputs a heading line pulse and an inverse heading line pulse for each revolution
of the antenna. The azimuth, heading line output signals and DC power input are connected to TB1
which is internally located in the base of the gearbox.
The encoder is supplied with +15V DC supply from the transceiver enclosure.
The Quadrature ACP comprises of two 90° phase shifted square wave pulse trains ACP1 & ACP2
whose frequency is dependent on antenna rotation rate.
- 1024 ACP pulses are required per 360° antenna rotation from each pulse train.
- ACP2 lags ACP1 by 90° for an antenna rotating clockwise when viewed from above.
- The output pulses have an amplitude of +15V.
Each rising or falling edge is decoded from these two pulse trains to provide 4096 ACPs per antenna
revolution.
The ARP pulse width is required to be equal to at least one 4096 decoded period but does not have to
have any specific timing in relation to ACPs i.e. it can be asynchronous w.r.t ACPs.
Polarity : Positive
Stabilisation : Relative
Format :1024 bi-phase quadrature
ACP & ARP
Ratio : 1:1 with scanner rotation
Amplitude : 5V to 15V differential
Impedance 9 Hhni 0e|
')$8 # %$&(
*.-%
*+-&
-3/61 63427
Note: The azimuth encoder is a sealed unit and contains no field serviceable or repairable parts.