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
8
of
35
After leaving the Power Amplifiers the 800MHz Downlink signal path passes through an AGC
Detector Module 17-019801 (annotated “S” in section 3.6.3.) 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 800MHz Downlink passes through a second bandpass
filter 02-007201 (annotated “T” in section 3.6.3.) which is tuned to pass the 800MHz Downlink
passband and to further reject out-of-band noise. Upon leaving the Bandpass Filter 800MHz Downlink
signal passes into a second Crossband Coupler 07-004814 (annotated “U” in sections 3.6.2. & 3.6.3.)
which combines the 800MHz Downlink with the UHF 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.)
Uplink
Uplink signals are received from the DAS and enter the case of the BDA at the N type port labelled
“ANT. FACING MOBILES” (annotated “B” in section 3.5.).
The Uplink signal then passes through a Crossband Coupler 07-004814 (annotated “B” in sections
3.6.4. & 3.6.5.) which splits the UHF band signal from the 800MHz band signal.
UHF Uplink
The UHF branch then passes through the Uplink path of Bandpass Duplexer Module 16-041402
(annotated “C” in section 3.6.4.) which is tuned to pass the UHF Uplink passband and to reject out-of-
band noise and then passes through the first of two amplification stages.
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 “D” in section 3.6.4.) and each path passes through one of the LNAs (annotated
“E” and “F” in section 3.6.4.) before being recombined by a second 2 way splitter/combiner 05-002603
(annotated “G” in section 3.6.4.).
The UHF Uplink then passes through Variable Switched Attenuator 10-000701 (annotated “H” in
section 3.6.4.) which can provide up to 30dB 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 UHF Uplink passes through AGC Attenuator Module 17-016401
(annotated “I” in section 3.6.4.) which is controlled by UHF Uplink AGC Detector Module 17-019802
and is capable of providing up to 15dB of signal attenuation.
The UHF Uplink then passes through a Bandpass Filter 02-010501 to further reject out-of-band noise
and then through the second stage of amplification, the second stage is composed of two 1W Low
Power Amplifiers 12-030301 arranged in parallel (each providing 33dB of signal gain). The signal is
split into two equal paths by a 3dB Splitter/Combiner 05-002603 (annotated “K” in section 3.6.4.) and
each path passes through one of the PAs (annotated “L” and “M” in section 3.6.4.) before being
recombined by a second 2 way splitter/combiner 05-002603 (annotated “N” in section 3.6.4.).
After leaving the Low Power Amplifiers the UHF Uplink signal path passes through an AGC Detector
Module 17-019802 (annotated “O” in section 3.6.4.) 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.