QPSK BURST DEMODULATOR FOR SATELLITE-COMMUNICATIONS SYSTEMS

This paper describes a digital signal processing quadrature phase shift keying (QPSK) burst demodulator for satellite communications that uses a new technique which sequentially changes the receive filter. By changing the filter bandwidth according to the signal preamble pattern, the proposed technique improves the recovered carrier S/N and the recovered symbol clock S/N. The demodulator's low unique word miss probability (P(miss)) and its low cycle-skip rate for the recovered carrier and symbol clocks at very low E(b)/N0 (3 dB or less) will ease the design of very small aperture terminal (VSAT) systems. A governmental communications application for the system is briefly discussed.