Abstract: A transmitting earth station for a satellite communications system in which the channel capacity of a two-carrier-per-transponder transmitter is greatly enhanced. The transmitting station is provided with an equalizer at the input to the high power amplifier (HPA). The transfer function of this equalizer assists in the reduction (in the first order approximation) of the intelligible crosstalk due to the non-linearities of the HPA, the travelling wave tube amplifier (TWTA) and the input transponder multiplexer. With the intelligible crosstalk reduced, the input backoff of the transponder TWTA may be reduced from -12dB to -6dB, which increases the channel capacity in the order of 500 channels.

Abstract: A PSK modulator employs a waveform of the overlapped raised cosine type which results in reduced adjacent channel interference. Waveforms of the overlapped raised cosine type include the overlapped raised cosine waveform itself as well as waveforms substantially similar thereto. Such waveforms can be produced, in a PSK modulator, by employing a Thomson filter with a single attenuation pole. Employing such a filter with a time bandwidth product (BT) of 1.2 provides the overlapped raised cosine waveform. However, changing the Thomson filter's BT product to 1.0 to thereby generate a waveform of the overlapped raised cosine type provides even further improvements in adjacent channel interference.