Abstract: Exemplary embodiments are directed to a reconfigurable system for the analogue processing of radio frequency signals in a satellite communications system. The system receives a pre-selected first intermediate frequency and selects one or more first frequency channels from the input signal, to amplify and provide automatic gain control of the selected first channel signals and to translate the selected first channels to one or more second frequency channel signals within a pre-selected second intermediate frequency band. The first and second intermediate frequencies are selected to minimize conversion of the uplink and downlink signals. The system provides a generic flexible communications satellite payload architecture based on single channel agile conversion and provides adjustable frequency conversion and bandwidth to individual satellite channels, allowing in-orbit flexible reconfiguration of payload frequency plan and operation.

Abstract: A system which provides frequency conversion and continuously variable bandwidth control is implemented using first and second filter networks that exhibit a generalised Chebyshev transfer function. The first and second filter networks may comprise a pseudo-high-pass type filter in combination with a pseudo-low-pass type filter, or in a particularly efficient embodiment, a pseudo-high-pass type filter in combination with an elliptic low pass type filter. The effective frequency response overlap of first and second filter networks produces a composite band-pass filter response which is highly selective by nature and is determined only by the steep band edge transition region of the individual filter networks. The maximum pass-band of the first and second filter networks can be tailored to precisely fit the maximum band-pass bandwidth required by a channelised radio communications system.

Abstract: A multiplexer comprises a number of directional filters 17.sub.n connected to a transmission line feeding an antenna 2, 3. Signals to be multiplexed fed to the filters 17.sub.n may be sent via respective switches 16.sub.n. Unlike prior multiplexers where each directional filter defines a respective channel of the multiplex, the channels of the multiplexer of the invention, apart from one at the end, are defined by the band pass response of one directional filter and the band stop response of another directional filter, since the band pass responses of the directional filters from the input connected to the switch to the output connected to the transmission line, and the corresponding band stop responses between the two output ports connected to the transmission line, overlap each other. The same arrangement may be used for demultiplexing.