Explain the importance of demultiplexer at the receiver to reduce the non-co-channel interference

10. Explain the importance of demultiplexer at the receiver to reduce the non-co-channel interference.

The main theme of using de multiplexer at the receiver end is to reduce the non co-channel interference. A 16:1 de multiplexer is used in between the pre-amplifier stage and filter stage as shown in figure below.

Particularly, 16:1 demultiplexer is used in order to receive 16 channels from a single antenna. The output of each antenna reaches demultiplexer after passing through a 25 dB gain amplifier. The total split loss of demultiplexer output and due to 16 channels is given by.

S =10 log 16

= 12.04

S =12.04 dB

Care must be taken such that the inter modulation product at the de multiplexer output is 65 dB down and the space diversity antennas connected to an umbrella filter must have a 55 dB rejection from other systems band, otherwise in case. if a dummy mobile unit is close to the cell site then the pre amplifier generates inter modulation frequency at the amplifiers output which may lead to cross talk.