Mobile satellite CDMA system robust to Doppler shift

摘要

This paper suggests a dual-channel PSK demodulator for LEOnsatellite DS/CDMA communications, whose performance is absolutelyninvariant to time-variant Doppler offset of a carrier and localnoscillator instability. The demodulator does not require any preamblen(pilot signal) for carrier recovery, differential encoder/decoder, andncarrier recovery circuit such as PLL and Costas loop, thereby resultingnin high transmission efficiency and system complexity reduction. In anCDMA channel with the demodulator, the transmitted CDMA signal isncomposed of two orthogonal linear polarized components, which are spreadnby different spreading codes, and only one of which is modulated by thendata stream. At the receiver, one of the two components despread by thencorresponding matched-filter is utilized as a pilot reference carriernfor the demodulation. Thereby, the Doppler offset is completelyneliminated from the received signal since both these components exhibitnthe same Doppler and local oscillator instability