User Manual

Axell Wireless Limited
Technical Literature
L.A. M.T.A. Remote Sites
Document Number 80-301401HBKM Issue No. 1 Date 13/06/2008 Page 56 of 148
3.6. 800MHz BDA UNIT (80-301405)
800MHz BDA UNIT (80-301405) provides the amplification stages for the 800MHz paths, The unit is
housed in a wall mount case 600x600x250mm (24” x 24” x 10” approx).
The Downlink 800MHz signal is received at the port labelled “D/L INPUT” (Annotated A in the picture
in section 3.6.4.2.). The Downlink 800MHz path passes through a bandpass filter to remove out of
band noise and then a switched attenuator providing 0 to 30 dB of RF signal attenuation, after the
Attenuator the signal passes through the first of two amplification stages. This first stage is provided
by a low noise amplifier which gives approx. 19dB of gain.
After the Low Noise Amplifier the Downlink 800MHz signal passes through the second amplification
stage; the signal is first split into two equal paths and then each path is passed through a 20W power
amplifier and then the two signal paths are re-combined. The second stage amplifiers are straddled
by an Automatic Gain Control assembly providing limiting to the output signals in the case of high
input signals.
After leaving the second stage amplifiers the Downlink 800MHz signal path passes through a second
bandpass filter before exiting the BDA via the port labelled “D/L OUTPUT” (B in section 3.6.4.2.).
The Uplink 800MHz signal is received at the port labelled “U/L INPUT” (C in section 3.6.4.2.). The
Uplink 800MHz path passes through a bandpass filter to remove out of band noise and then into the
first of two amplification stages, the first stage is provided by a low noise amplifier which gives approx.
19dB of gain; after leaving the Low Noise Amplifier the signal passes through a switched attenuator
providing 0 to 30 dB of RF signal attenuation,
After leaving the switched attenuator the Uplink 800MHz path passes through the second stage of
amplification which is provided by a 5W power amplifier giving approx. 30db of gain; this second
amplification stage is straddled by an Automatic Gain Control assembly providing limiting to the output
signals in the case of high input signals.
After leaving the second amplification stage the Uplink 800MHz path passes through a second
bandpass filter before exiting the BDA via the port labelled “U/L OUTPUT” (D in section 3.6.4.2.).
800MHz BDA UNIT (80-301405) is provided with a 24V DC input to power the amplifier modules
within and those amplifier modules are configured to provide alarm status reports.