PSK GROUP MODEM FOR SATELLITE COMMUNICATIONS.

A PSK group modem which modulates and demodulates multiple PSK signals en bloc will play an important role in realizing a cost-effective satellite communications system based on the narrowband multicarrier PSK/FDMA technique. Its possible applications are briefly discussed, and a developed PSK group modem is presented, including its algorithm, hardware design, and implementation. In the algorithm, filtering of respective PSK signals is effectively carried out by digital signal processing techniques applied to the digital transmultiplexer. Furthermore, in order to compensate for the difference between the operation timing of the PSK group modem and the symbol timing of each input/output data signal, digital signal processing based on a table-look-up method using ROM and a rate-conversion filter with adaptive weighting are proposed for the modulator and demodulator, respectively. An experimental four-phase PSK group modem has been developed, and experiments have been conducted under various conditions. The measured performance of the developed hardware is also demonstrated.