Satellite communication apparatus
View Patent ↗A satellite communication apparatus has a corrector for reducing distortion of a signal in a communication channel. The corrector is formed by a forward model representative of a pre-calculated estimate of non-linearity and group delay of the satellite transmission/reception channel from the input to the up sampler through to the output of the down sampler. The forward model may also comprise a model of magnitude response of a satellite input multiplexer filter and output multiplexer filter. Cascaded identical stages of the corrector may be provided so that distortion in the channel is successively reduced towards zero by each successive stage. An initial approximator which is substantially the inverse of the distorting function of the forward model may be provided.
1. A satellite communication apparatus including successive cascaded identical stages of corrector means for reducing distortion of a signal in a satellite communication channel, each stage of said corrector means providing pre-correction required for counteracting distortion of said signal in said channel and including a forward model, wherein said forward model is a pre-calculated estimate of non-linearity and group delay in said channel, and further wherein distortion in said channel is successively reduced towards zero by each successive stage.
2. An apparatus as claimed in claim 1 , wherein said channel includes a satellite having a cascaded input multiplexer filter, a power amplifier an output multiplexer filter, and said forward model further comprises a model of magnitude response of said input multiplexer filter and output multiplexer filter, whereby magnitude response of said channel may be corrected.
3. An apparatus as claimed in claim 1 , wherein said forward model comprises a series connection of an up-sampler, a model representative of magnitude and phase of:
a transmission side root Nyquist filter,
a transmission side high power amplifier,
a satellite input multiplexer filter,
a satellite power amplifier,
a satellite output multiplexer filter,
a receiver side root Nyquist filter,
and a down sampler.
4. An apparatus as claimed in claim 3 , wherein said satellite power amplifier is one of a travelling wave tube and a solid state amplifier.
5. An apparatus as claimed in claim 1 , wherein an initial approximator is connected in an input path to said corrector means, said initial approximator comprising a static pre-distortion approximation model representative of at least one of channel magnitude and phase non-linearity and group delay of said channel.
6. An apparatus as claimed in claim 5 , wherein said initial approximator is substantially an inverse function of the forward model of said corrector means.
7. An apparatus as claimed in claim 1 , wherein said signal is modulated in accordance with one of 16 QAM, 32 QAM, 8 PSK and 16 PSK.
8. An apparatus as claimed in claim 5 , wherein one initial approximator and three successive corrector means stages are provided.
9. An apparatus as claimed in claim 1 , wherein six successive corrector means are provided.
10. A method for reducing distortion of a signal in a satellite communication channel including the step of providing successive cascaded identical stages of a corrector providing pre-correction to counteract distortion of said signal in said channel, said pre-corrector being formed as a forward model modelling non-linearity and group delay in said channel, wherein distortion in said channel is successively reduced towards zero by each successive stage.
11. A method as claimed in claim 10 , wherein said channel includes a satellite having a cascaded input multiplexer filter, a power amplifier and an output multiplexer filter and said forward model further model further comprises a model of magnitude response of said input multiplexer filter and output multiplexer filter, whereby magnitude response of said channel may be corrected.
12. A method as claimed in claim 10 , wherein said forward model comprises a series connection of an up-sampler; a representation of magnitude and phase distortion produced by a transmitting side root Nyquist filter, a transmitting side high power amplifier, a satellite input multiplexer filter, a satellite power amplifier, a satellite output multiplexer filter, a receiving side root Nyquist filter; and a down sampler.
13. A method as claimed in claim 10 , wherein a static pre-distorter approximation model representative of at least one of channel magnitude and phase non-linearity and group delay of said channel is evaluated and said signal passed through said initial approximator prior to passage to said forward model.
14. A method as claimed in claim 13 , wherein said approximation model is substantially an initial approximation arranged to be an inverse function of the forward model.
15. A satellite communication apparatus including corrector means for reducing distortion of a signal in a satellite communication channel, said corrector means comprising a forward model providing pre-correction required for counteracting distortion of said signal in said channel, said forward model being a pre-calculated estimate of non-linearity and group delay in said channel comprising a series connection of an up-sampler, and a model representative of magnitude and phase of:
a transmission side root Nyquist filter,
a transmission side high power amplifier,
a satellite input multiplexer filter,
a satellite power amplifier,
a satellite output multiplexer filter,
a receiver side root Nyquist filter,
and a down sampler.
16. A satellite communication apparatus including corrector means for reducing distortion of a signal in a satellite communication channel, said corrector means comprising a forward model providing pre-correction required for counteracting distortion of said signal in said channel, said forward model being a pre-calculated estimate of non-linearity and group delay in said channel comprising a series connection of an up-sampler, a model representative of magnitude and phase of:
a transmission side root Nyquist filter,
a transmission side high power amplifier,
a satellite input multiplexer filter,
a satellite power amplifier,
a satellite output multiplexer filter,
a receiver side root Nyquist filter,
and a down sampler,
and wherein an initial approximator is connected in an input path to said corrector means, said initial approximator comprising a static pre-distortion approximation model representative of at least one of channel magnitude and phase non-linearity and group delay of said channel.
17. A method for reducing distortion of a signal in a satellite communication channel including the step of modelling distortion of said signal in said channel caused by non-linearity and group delay and providing said model as a forward model in a corrector for counteracting said distortion, and wherein said forward model comprises a series connection of an up-sampler; a representation of magnitude and phase distortion produced by a transmitting side root Nyquist filter, a transmitting side high power amplifier, a satellite input multiplexer filter, a satellite power amplifier, a satellite output multiplexer filter, a receiving side root Nyquist filter; and a down sampler.
18. A method for reducing distortion of a signal in a satellite communication channel including the step of modelling distortion of said signal in said channel caused by non-linearity and group delay and providing said model as a forward model in a corrector for counteracting said distortion, and wherein said forward model comprises a series connection of an up-sampler; a representation of magnitude and phase distortion produced by a transmitting side root Nyquist filter, a transmitting side high power amplifier, a satellite input multiplexer filter, a satellite power amplifier, a satellite output multiplexer filter, a receiving side root Nyquist filter; and a down sampler, and further wherein a static pre-distorter approximation model representative of at least one of channel magnitude and phase non-linearity and group delay of said channel is evaluated and said signal passed through said initial approximator prior to passage to said forward model.
19. A satellite communication apparatus including corrector means for reducing distortion of a signal in a satellite communication channel, said corrector means comprising a forward model providing pre-correction required for counteracting distortion of said signal in said channel, said forward model being a estimate of non-linearity and group delay in said channel, wherein said forward model includes a satellite power amplifier which is one of a travelling wave tube and a solid state amplifier.
20. A satellite communication apparatus including corrector means for reducing distortion of a signal in a satellite communication channel, said corrector means comprising a forward model providing pre-correction required for counteracting distortion of said signal in said channel, said forward model being a pre-calculated estimate of non-linearity and group delay in said channel, wherein an initial approximator is connected in an input path to said corrector means, said initial approximator comprising a static pre-distortion approximation model representative of at least one of channel magnitude and phase non-linearity and group delay of said channel.
21. A satellite communication apparatus including corrector means for reducing distortion of a signal in a satellite communication channel, said corrector means comprising a forward model providing pre-correction required for counteracting distortion of said signal in said channel, said forward model being a pre-calculated estimate of non-linearity and group delay in said channel, wherein an initial approximator is connected in an input path to said corrector means, said initial approximator comprising a static pre-distortion approximation model representative of at least one of channel magnitude and phase non-linearity and group delay of said channel, and further wherein said initial approximator is substantially an inverse function of the forward model of said corrector means.
22. A method for reducing distortion of a signal in a satellite communication channel including the steps of modelling distortion of said signal in said channel caused by non-linearity and group delay and providing said model as a forward model in a corrector for counteracting said distortion, wherein a static pre-distorter approximation model representative of at least one of channel magnitude and phase non-linearity and group delay of said channel is evaluated and said signal passed through said initial approximator prior to passage to said forward model.
23. A method for reducing distortion of a signal in a satellite communication channel including the steps of modelling distortion of said signal in said channel caused by non-linearity and group delay and providing said model as a forward model in a corrector for counteracting said distortion, wherein a static pre-distorter approximation model representative of at least one of channel magnitude and phase non-linearity and group delay of said channel is evaluated and said signal passed through said initial approximator prior to passage to said forward model, and further wherein said approximation model is substantially an initial approximation arranged to be an inverse function of the forward model.