Design of 5-Channel C-Band Input Multiplexer for Communication Satellites

In a multi user communication environment such as communication satellites, inter-channel isolation is provided by channelizing/multiplexing networks that splits composite wideband signal into various narrowband RF signals corresponding to each user. In a communication satellite transponder, input multiplexing network is placed at the output of low noise receiver. It divides the composite received signal into various narrowband signals and controls the interference among the channels below certain level. The stringent isolation requirements of these networks require the channel filters to have transmission zeros to be placed just outside the passband. This paper describes the electrical design of a 5-channels C-band input multiplexer (IMUX). Comparative analysis of different multiplexer configurations is described in detail. Among different available filter technologies for realization, dual mode circular waveguide technology is an optimum choice. In order to meet the in-band performance requirements, 10th order channel filters were realized with four transmission zeros for stopband rejection and four transmission zeros for group delay equalization (10-4-4). System-level simulation of of the multiplexer is performed and the simulation show good agreement with design requirements.