User Manual

Axell Wireless Limited
Technical Literature
15 Channel UHF Hybrid Select Repeater
Document Number 50-157401HBK Issue No. 1 Date 26/03/2008 Page 14 of 50
4.1. Downlink Splitter/Combiner 50-157402
Downlink Splitter/Combiner 50-157402 is housed in an 8U rack mount chassis.
Downlink signals are received from the RX antenna via the port labelled “RX ANT” in the top of the
rack and are fed down to enter the Downlink Splitter/Combiner via the port labelled “RX ANT”
The downlink signal is first passed through a bandpass filter (02-011204) to reject out-of-band noise
and then a 30dB Low Noise Amplifier (11-007402). Next the signal; passes through a switched
attenuator (10-000701) which provides up to 30dB of signal attenuation in 2dB steps. The adjustment
switches for this attenuator are accessible on the back panel of the shelf. After leaving the attenuator
the signal is passed through a second Low Noise Amplifier (11-007302) this time providing 20dB of
signal gain.
After leaving the second Low Noise Amplifier the signal is split into three equal paths by a
Splitter/Combiner (05-003803) each of the three signal paths then leaves the Downlink
Splitter/Combiner for the Channel Module Shelves (50-157403 & 50-157404), via the SMA ports
labelled “A”, “B” and “C”.
Port A takes the signal to Channel Module Shelf 1 (50-157403) which houses the channel selectivity
modules for channels 1 to 6.
Port B takes the signal to Channel Module Shelf 2 (50-157403) which houses the channel selectivity
modules for channels 7 to 12.
Port C takes the signal to Channel Module Shelf 3 (50-157404) which houses the channel selectivity
modules for channels 13 to 15.
The signals from the Channel Module Shelves re-enter the Downlink Splitter/Combiner via the SMA
ports labelled “D”, “E” and “F”.
Port D is the input from Channel Module Shelf 1, channels 1 to 6.
Port E is the input from Channel Module Shelf 2, channels 7 to 12.
Port F is the input from Channel Module Shelf 3, channels 13 to 15.
After the three signal paths from the Channel Module Shelves re-enter the Downlink Splitter/Combiner
they are combined by a second Splitter/Combiner (05-003803), the combined signal then passes
through a second switched attenuator (10-000701); this attenuator is factory pre-set to its required
value, is not accessible and requires no adjustment. After leaving the attenuator the signal is passed
through a 1W Power Amplifier (12-021801) providing 15dB of gain.
The Downlink signal now exits the Downlink Splitter/Combiner shelf again via the SMA port labelled
“RF O/P” on the front panel, this output goes to the 100W Amplifier shelf (80-245103), after leaving
the 100W Amplifier shelf the signal re-enters the Downlink Splitter/Combiner shelf via the SMA port
labelled “RF I/P” on the front panel. The signal is then passed through a second bandpass filter (02-
011204) to further reject out-of-band noise and then the signal enters 4 Port Hybrid Coupler (05-
000101) where the signal is split into two paths, each path then leaves the Downlink Splitter/Combiner
shelf via the ports labelled “LCX 1” and “LCX 2” and are fed up to the ports in the top of the rack, also
labelled “LCX 1” and “LCX 2”, from here the connection is made to the LCX Cables.
The Uplink signals are received from the two LCX Cables at the ports labelled “LCX1” and “LCX2” in
the top of the rack and fed down to enter the Downlink Splitter/Combiner 50-157402 via the Ports
labelled “LCX 1” and “LCX 2”, the signal enters 4 Port Hybrid Coupler (05-000101) where the two
signal paths are combined into a into a single path which then leaves the Downlink Splitter/Combiner
for the first of the Uplink Triplexer Shelves 50-157405 via the port labelled “N”