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 31 of 114
4.5. 8 Channel Squelch Gated BDA 60-228704
8 Ch. Squelch Gated BDA 60-228704 is built into an 8U, 19” rack-mount case
60-228704 utilizes Software Defined Radio (SDR) technology to digitally process the signal to define the
required channel frequencies and bandwidth (eight channels in the Downlink path and eight in the Uplink
path). As part of the digital signal processing function the signal amplitude is monitored to apply squelch
functionality to the signal path to attenuate unwanted noise when the input signal level is low. The unit is
pre-programmed with the 8 required duplex frequencies and channel bandwidths as indicated in section
4.5.2., these can be modified by the use of RMC software.
Band 1 Downlink RF from Quadplexer (Base) 60-228706 enters the BDA via the N type port labeled “A”
(annotated “A” in section 4.5.4.) and the Downlink signal passes through the Downlink path of UHF SDR
Module E931030 to define the 8 required Downlink channels.
After passing through the SDR module the Band 1 Downlink signal is split into two equal paths by 3dB
Splitter/Combiner 05-002603; The first path passes through the Downlink 25W Power Amplifier 12-026902
which provides 37dB of signal gain and then the signal exits the BDA via the N type port labeled “C”
(annotated “B” in section 4.5.4.) on its way to the local DAS by way of Quadplexer (DAS) 60-228706.
The second path from 3dB Splitter/Combiner 05-002603 exits the BDA for Splitter/Combiner Unit 60-228702
(and ultimately the Gallery Place Station CRAS System) via the N type port labeled “F” (annotated “C” in
section 4.5.4.)
Band 1 Uplink RF from the local DAS (by way of Quadplexer (DAS) 60-228706) enters the BDA via the N
type port labeled “D” (annotated “D” in section 4.5.4.) and passes through 15dB Directional Coupler 90-
852315 before entering UHF SDR Module E931030.
Band 1 Uplink RF from Splitter/Combiner Unit 60-228702 (from the Gallery Place Station CRAS System)
enters the BDA via the N type port labeled “E (annotated “E” in section 4.5.4.) and also passes
through15dB Directional Coupler 90-852315 where it is coupled onto the main Uplink signal path which
passes through the Uplink path of UHF SDR Module E931030 which utilizes SDR technology to digitally
process the signal to define the 8 required Uplink channels. After passing through the SDR module the
Band 1 Uplink signal passes through the Uplink 25W Power Amplifier 12-026902 which provides 37dB of
signal gain and then the signal exits the BDA via the N type port labeled “B” (annotated “F” in section 4.5.4.)
on its way to the BTS by way of Quadplexer (Base) 60-228706.
8 Ch. Squelch Gated BDA 60-228704 is powered by a 24V DC supply from the Redundant PSU Modules
96-300091 in PSU Housing Shelf 96-300090, The 24V DC supply powers the Power Amplifiers and an on-
board DC/DC converter J1421001 steps down the 24V supply to provide 6.45v and 15v DC to power the
SDR, Controller and Ext. Alarm/battery modules within the BDA.
Each Power Amplifiers have alarm outputs which are summed at the 9 way “D” panel plug labeled “ALARM
on the front panel (annotated J” in section 4.5.4.), the alarm data is connected to the External Alarm and
Battery Module J1161030 (annotated “K” in section 3.6.3.), from where the summary alarm data is fed to the
Krone terminal block located near the top of the rack (see section 4.3.2.).
The SDR controller module H561003 is used to control and supervise the SDR functionality, two ports are
provided where an operator may connect into the system, a local serial port, (a 9 way D” panel socket
annotated “N” in section 4.6.4.) is used with a laptop PC running suitable terminal-emulation software to
interrogate and control the equipment using GET and SET commands. Alternatively the equipment can be
configured using RMC software via the RJ45 ethernet port (annotated “O” in section 4.6.4.) To ensure
synchronous communications between the SDR and the H56 controller, a high stability 10MHz reference
generator, R031002 is incorporated in the equipment backplane.