400CH SCPC SIGNAL DEMODULATOR USING CHIRP TRANSFORM AND CORRELATION DETECTION SCHEME.

A group demodulator for PSK-FDMA (phase-shift-keyed frequency-division multiple access) signals using a chirp transform is proposed for hardware and power consumption reduction of demodulators at a hub station. The proposed demodulator uses a chirp filter for FDM/TDM transform of received PSK-FDMA signals and demodulates TDM transform signals by recovering each channel carrier and clock. Since the chirp filter works as an analog correlator, the transform TDM signals have the maximum S/N (signal-to-noise) ratio at the sampling instant, achieving 2 b/s/Hz frequency utilization efficiency with a QPSK (quadrature phase-shift keyed) modulation scheme. The feasibility test results on the prototype 400-channel demodulator show a good agreement with theory. The proposed group demodulator can contribute to reduce significantly hardware size and power consumption of hub stations.