Satellite up-link fade control

A method of providing up-link fade control for a satellite not having AGC, said up-link having a modulator in a transmitting station, including the steps of determining plural characteristics for correcting channel non-linearity, each characteristic being determined for a different value of up-link fade, determining a signal representative of up-link fade by beacon receiver means, associating said signal with a correction characteristic for said up-link fade, applying said correction characteristic associated with said signal to corrector means of said modulator, whereby said corrector means changes the modulator characteristics to modify constellation parameters at a satellite receiver, and said corrector means performs dynamic pre-correction by pre-distorting a signal which has been modulated to carry signals representative of digital data so as to reduce non-linear distortion in a signal channel containing root Nyquist bandpass filters in transmission and reception portions of said channel, there being provided a series connection of a static pre-distortion section configured to represent an inverse function of magnitude and phase distortion estimated to occur in said channel, and at least one dynamic pre-distortion section, the or each dynamic pre-distorting section including a forward model configured to represent magnitude and phase distortion in said channel, said signal being passed through cascaded sections whereby each successive dynamic pre-distorting section receives input from an output of a preceding dynamic pre-distorting section so that distortion in said channel is successively reduced to zero with each successive dynamic pre-distorting section.

A system for providing up-link fade control for a satellite not having AGC, said system including a modulator in a transmitting station of said up-link, means for determining plural characteristics for correcting channel non-linearity, each characteristic being determined for a different value of up-link fade, means for determining a signal representative of up-link fade by beacon receiver means, means for associating said signal with a correction characteristic for said up-link fade, means for applying said correction characteristic associated with said signal to corrector means of said modulator, whereby said corrector means changes the modulator characteristics to modify constellation parameters at a satellite receiver, and said corrector means performs dynamic pre-correction by pre-distorting a signal which has been modulated to carry signals representative of digital data so as to reduce non-linear distortion in a signal channel containing root Nyquist bandpass filters in transmission and reception portions of said channel, there being provided a series connection of a static pre-distortion section configured to represent an inverse function of magnitude and phase distortion estimated to occur in said channel, and at least one dynamic pre-distortion section, the or each dynamic pre-distorting section including a forward model configured to represent magnitude and phase distortion in said channel, said signal being passed through cascaded sections whereby each successive dynamic pre-distorting section receives input from an output of a preceding dynamic pre-distorting section so that distortion in said channel is successively reduced to zero with each successive dynamic pre-distorting section.