User Manual

Axell Wireless Limited
Technical Literature
Dual Band Fiber Fed BDA 60-232301
Document Number
60
-
232301HBK
Issue No.
2
Date
22
/
12
/
2009
Page
7
of
35
After leaving the attenuator the UHF Downlink passes through AGC Attenuator Module 17-016401
(annotated “J” in section 3.6.2.) which is controlled by UHF Downlink AGC Detector Module 17-
019802 and is capable of providing up to 15dB of signal attenuation.
The UHF Downlink then passes through two stages of amplification; the first stage is composed of
two Low Noise Amplifiers 11-007402, arranged in parallel (each providing 30dB of signal gain). The
signal is split into two equal paths by a 3dB Splitter/Combiner 05-002603 (annotated “K” in section
3.6.2.) and each path passes through one of the LNAs (annotated “L” and “M” in section 3.6.2.) before
being recombined by a second 2 way splitter/combiner 05-002603 (annotated “N” in section 3.6.2.).
The second stage is composed of two 5W Power Amplifiers 12-021601 arranged in parallel (each
providing 30dB of signal gain). The signal is split into two equal paths by a 3dB Splitter/Combiner 05-
002603 (annotated “O” in section 3.6.2.) and each path passes through one of the PAs (annotated “P”
and “Q” in section 3.6.2.) before being recombined by a second 2 way splitter/combiner 05-002603
(annotated “R” in section 3.6.2.).
After leaving the Power Amplifiers the UHF Downlink signal path passes through an AGC Detector
Module 17-019801 (annotated “S” in section 3.6.2.) which regulates the gain level by adjusting AGC
Attenuator Module 17-016401; The AGC Detector module monitors the RF level being delivered by
the power amplifier, and when a certain threshold is reached it begins to increase the value of the
AGC Attenuator Module to limit the RF output to the (factory set) threshold. Therefore overloading of
the power amplifier is avoided.
After leaving the AGC Detector Module the UHF Downlink passes through the Downlink path of
Bandpass Duplexer Module 16-041402 (annotated “T” in section 3.6.2.) to further reject out-of-band
noise. Upon leaving the Duplexer module the UHF Downlink signal passes into a second Crossband
Coupler 07-004814 (annotated “U” in sections 3.6.2. & 3.6.3.) which combines the UHF Downlink with
the 800MHz band Downlink path and the combined signal exits the BDA for the DAS via the N type
port labelled “ANT. FACING MOBILES” (annotated “B” in section 3.5.)
800MHz Downlink
After passing through Crossband Coupler 07-004814 (annotated “G” in sections 3.6.2. & 3.6.3.) the
800MHz branch then passes through a bandpass filter 02-007201 (annotated “H” in section 3.6.3.)
which is tuned to pass the 800MHz Downlink passband and to reject out-of-band noise and then
passes through Variable Switched Attenuator 10-000901 (annotated “I” in section 3.6.3.) which can
provide up to 15dB of attenuation in 1dB steps if required, the attenuation is controlled by a set of four
toggle switches on the body of the attenuator; each switch is clearly marked with the attenuation it
provides, and the total attenuation in-line is the sum of the values switched in.
After leaving the attenuator the 800MHz Downlink passes through AGC Attenuator Module 17-016401
(annotated “J” in section 3.6.3.) which is controlled by 800MHz Downlink AGC Detector Module 17-
019802 and is capable of providing up to 15dB of signal attenuation.
The 800MHz Downlink then passes through two stages of amplification; the first stage is composed of
two Low Noise Amplifiers 11-006702, arranged in parallel (each providing 30dB of signal gain). The
signal is split into two equal paths by a 3dB Splitter/Combiner 05-002602 (annotated “K” in section
3.6.3.) and each path passes through one of the LNAs (annotated “L” and “M” in section 3.6.3.) before
being recombined by a second 2 way splitter/combiner 05-002602 (annotated “N” in section 3.6.3.).
The second stage is composed of two 20W Power Amplifiers 12-023301 arranged in parallel (each
providing 37dB of signal gain). The signal is split into two equal paths by a 3dB Splitter/Combiner 05-
002602 (annotated “O” in section 3.6.3.) and each path passes through one of the PAs (annotated “P”
and “Q” in section 3.6.3.) before being recombined by a second 2 way splitter/combiner 05-002602
(annotated “R” in section 3.6.3.).