Apparatus for use in a
communications satellite to select signals in a first frequency range from a received multiplexed
signal comprises a first mixer arranged to mix the received
signal with a first
local oscillator LO
signal to down-convert the received signal so that a signal within the received signal at a centre frequency of the first frequency range is converted to an
intermediate frequency IF, a bandpass filter arranged to filter the mixed signal such that the
filter bandwidth defines the width of the first frequency range, the bandpass filter having a
passband with a centre frequency at the IF, and a second mixer arranged to mix the filtered IF signal with a second LO signal to up-convert the IF signal to the output frequency range. One of the first and second LO signals is a mixed LO signal obtained by mixing the other one of the first and second LO signals with a third LO signal, and the output frequency range is different to an input frequency range in which the multiplexed signal was received. The first LO signal is controllable to change the frequency that is converted to the
intermediate frequency by the mixer, to select a different frequency range as the first frequency range. A
system is also disclosed for flexibly routing signals in a
communications satellite. The
system comprises an input arranged to send the received signal to each one of a plurality of frequency-conversion modules comprising the apparatus, a plurality of amplifiers for amplifying converted signals outputted by the frequency-conversion modules, and an output module arranged to receive the amplified signals and form a plurality of downlink beams, each downlink beam including one or more of the amplified converted signals. The amplifiers can be variable-power amplifiers to amplify each converted signal to a transmit power according to the bandwidth occupancy. The
system can be used in forward or return path payloads.