Abstract: Embodiments of the present invention comprise a signal processing method and apparatus for use in a satellite payload in which an input RF signal received at a receiver antenna is modulated by using a single optical carrier at the input of an optical modulator. The optical domain signal is processed and is subsequently combined with a single unmodulated optical LO tone to provide an output RF signal for radiation by a transmitter antenna or for further digital processing by an on-board processor. This results in a clean generation of the frequency-converted RF signal at the output of the opto-electrical conversion stage.

Abstract: Embodiments of the present invention comprise a signal processing method and apparatus for use in a satellite payload in which an input RF signal received at a receiver antenna is modulated by using a single optical carrier at the input of an optical modulator. The optical domain signal is processed and is subsequently combined with a single unmodulated optical LO tone to provide an output RF signal for radiation by a transmitter antenna or for further digital processing by an on-board processor. This results in a clean generation of the frequency-converted RF signal at the output of the opto-electrical conversion stage.

Abstract: There is provided an apparatus for a satellite communication system comprising: a processor to determine at least one out of a phase offset for a frequency channel of a plurality of frequency channels demultiplexed from a carrier to compensate for group delay variation within the carrier and a gain offset for the frequency channel to compensate for gain variation within the carrier, wherein the processor is further configured to apply the at least one out of the determined phase offset and gain offset to the frequency channel before the carrier is reformed from said plurality of frequency channels. The invention therefore provides a way of digitally compensating for any undesired gain and group delay introduced by, for example, analogue components such as filters in the satellite communication system.

Abstract: Apparatus for a satellite communication system, comprising: a processor arrangement to monitor a plurality of frequency channels demultiplexed from a signal comprising one or more carriers, identify at least one frequency channel of the plurality of frequency channels comprising interference and remove the at least one identified frequency channel before the one or more carriers are reformed. By removing the frequency channels comprising interference, the signal-to-noise ratio of a carrier can be improved. Also, if the interference occurs within a carrier, the carrier is usable as long as the removed frequency channels are considerably narrower than the carrier.

Abstract: There is provided an apparatus for a satellite communication system comprising: a processor to determine at least one out of a phase offset for a frequency channel of a plurality of frequency channels demultiplexed from a carrier to compensate for group delay variation within the carrier and a gain offset for the frequency channel to compensate for gain variation within the carrier, wherein the processor is further configured to apply the at least one out of the determined phase offset and gain offset to the frequency channel before the carrier is reformed from said plurality of frequency channels. The invention therefore provides a way of digitally compensating for any undesired gain and group delay introduced by, for example, analogue components such as filters in the satellite communication system.

Abstract: A signal pre-processor, for at least partially correcting non-linear performance of a high power amplifier (“HPA”), operates on an over-sampled signal in complex form in the digital domain. By converting the over-sampled signal to amplitude values, the pre-processor is enabled to apply correction values, based on the amplitude values, which correction values incorporate both amplitude and phase correction in respect of distortion generated in the HPA. The use of an over-sampled signal allows out-of-band correction values to be applied to correct out-of-band distortion arising in the signal processing path, for instance in the linearization process itself. The out-of-band distortion can otherwise alias back in-band, creating noise at the HPA.