The development of a forward error correcting (FEC) modem forlow-bit-rate satellite communication systems using direct-sequencespread-spectrum multiple-access (DS-SSMA) communication techniques isdescribed. Utilizing a digital correlator and a convolutionalencoder/Viterbi decoder, the modem achieves rapid acquisition time andlow bit error rate performance under very low carrier-to-noise (C/N)ratios. Experimental results indicate a mean acquisition time of 220 msand bit error rate of less than 1×10-7 at the receivedintermediate frequency C/N ratio of -31 dB. The digital matched filter,digital correlator LSI, delay lock loop, and binary phase-shift keyingmodulator used in the modem are described
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