Handbook
Axell Wireless Limited
Technical Literature
WMATA CRCS Redundant Antenna System
General Overview
Document Number 60-228701HBK Issue No. 3 Date 28/05/2010 Page 62 of 114
RF/Optical
RF
Relay
16 Ch. DSP U/L
Squelch Gate 1
16 Ch. DSP U/L
Squelch Gate 26
Primary Downlink Optical Input from
Jackson Graham Building system
Redundant Downlink Optical Input
from Carmen Turner Facility system
Primary Uplink Optical Output to
Jackson Graham Building system
Redundant Uplink Optical Output to
Carmen Turner Facility system
RF Downlink Output
to CRCS Donor Unit
RF Uplink Input
from CRCS Donor Unit
RF Uplink Input
from CRCS Donor Unit
RF Combiner
16 Ch. DSP U/L
Squelch Gates 2 to 25
The Gallery Place Station CRAS System receives a Primary optical Downlink from the Jackson Graham
Building CRAS System and a Redundant optical Downlink from the Carmen Turner Facility CRAS System,
both optical Downlink feeds enter the Gallery Place Station CRAS System and are demodulated to RF.
Normally the Primary Downlink signal from the Jackson Graham Building is passed on to the CRCS Donor
Unit but if the signal strength of the Primary Downlink path falls below a pre-set threshold then RF relays in
the Gallery Place Station CRAS System automatically switch to the Redundant signal path from the Carmen
Turner Facility CRAS System.
26 Uplink paths are received from the CRCS Donor Unit; each path is fed into a Channelized DSP U/L
Squelch Gate and the outputs from those 26 units are combined and modulated onto optical signals, the
Primary optical Uplink being fed to the Jackson Graham Building CRAS System and in the event that the
main signal path is switched out, the Redundant optical Uplink path is fed to the Carmen Turner Facility
CRAS System
5.1. Simplified System Sketch