Ericsson RBS 2106 Hardware Reference Manual page 285

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CDU-F has four filter cavities grouped internally two and two. The two filters
form a combiner for two TX signals and can be combined with a Combining
Network Unit (CNU) to a combiner for four signals, or connected to another
CDU-F to form a combining network for six signals.
The combined signals are fed through a lowpass TX filter to a duplex filter.
The duplex filter allows the use of a single antenna both for transmitting and
receiving. The duplex filter is connected directly to the antenna connector on
top of the CDU.
All necessary connections for the TX combining network are done on the front
of the CDU with the CNU.
Tuning the filter cavities is controlled by the Measurement Receiver (MR) and
the Central Processor Unit (CPU).
A small part of the output and reflected power is distributed by the
Measurement Coupler Unit (MCU) to four outputs. The signals are then
connected to the MR in the same CDU-F, or the MR in another CDU-F,
depending on the configuration.
The MR measures the input signal to the filter combiners and also the
outgoing signal to the antenna. These two signals are used in the CPU to
control the stepper motors, one for each filter cavity. Moving parts in the filter
cavity, tune the combiner to the correct frequency.
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The duplex filter filters out the RX signal arriving to the antenna. This filtered
signal is amplified in a two-stage low noise amplifier and then filtered in a
lowpass filter.
CDU-F also has an extra RX chain for diversity reception. This extra RX chain
is similar to the duplex RX chain.
Distribution of RX signals is performed in the Configuration Switching Unit
(CXU).
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EN/LZT 720 0237 R1A