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 20 of 114
4. 60-228701 - WMATA Carmen Turner Facility CRAS System
The WMATA Carmen Turner Facility CRAS System consists of the following equipment mounted in a 41U,
19” equipment housing rack
Part No. 96-300090 PSU Housing Shelf
Contains Qty. 2, Part No. 96-300091 PSU Modules
Part No. 60-228703 Dual Fiber Optic Unit
Part No. 60-228702 Splitter/Combiner Unit
Part No. 60-228706 Quadplexer (Base)
Part No. 60-228706 Quadplexer (DAS)
Part No. 60-228704 8 Ch. Squelch Gated BDA (Band 1)
Part No. 60-228705 8 Ch. Squelch Gated BDA (band 2)
The Carmen Turner Facility CRAS System provides the Redundant Downlink to and receives the
Redundant Uplink signal from the Gallery Place Station CRAS System. In addition, the Carmen Turner
Facility CRAS System also provides a Downlink to and receives an Uplink from a local Distributed Antenna
System within the Carmen Turner Facility building
Downlink RF from a remote off-air BTS is received and the signal is split into two paths; each path consists
of a pair of frequencies, Downlink and Uplink, within the overall operating passband which can be processed
together While allowing the easy rejection of opposing frequencies. For the sake of convention, within the
Carmen Turner Facility CRAS System, the descriptions “Band 1” and “Band 2” will be used to refer to the
two Downlink and Uplink pairs according to the following table:
Band 1
Downlink 489.5MHz to 491.0MHz
Uplink 492.5MHz to 494.0MHz
Band 2
Downlink 496.3MHz to 496.7MHz
Uplink 499.3MHz to 499.7MHz
The Downlink signals are then processes utilizing SDR technology to define the eight operating channels.
and then amplified. The two paths are re-combined and then fed to the distributed antenna system.
RF Uplink from the distributed antenna system is split into two paths, for the reasons outlined above, which
are processed utilizing SDR technology to define the eight operating channels and amplified. The two paths
are then re-combined and then fed to the BTS.
In the Downlink path the signal is split by means of a directional coupler and fed to a fiber optic transmitter
which modulates the RF signal on to an optical signal which is then fed to the Gallery Place Station CRAS
System.
Optical Uplink signals from the Gallery Place Station CRAS System are received and demodulated to RF
and coupled onto the Uplink path to the remote off-air BTS.
Provision is made for a redundant standby path in both the Downlink and Uplink to and from the Gallery
Place Station CRAS System; these are referred to as the “Main Redundant” and “Standby Redundant”
paths.