Data Modulation for a Direct Sequence Pseudonise Spread Spectrum Communication System
MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
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This report considers the incoherent demodulation performance of M- ary orthogonal keying MOK and M-ary differential phase shift keying MDPSK in the presence of a Doppler frequency shift of the carrier. It is shown that MOK has a significant performance improvement over MDPSK for values of M greater than four in terms of the required signal-to-noise ratio per information bit. The choice of the orthogonal signaling set is important in evaluating the sensitivity of MOK to Doppler frequency shift. If Walsh function signaling sets are to be chosen, then the ultimate performance in Doppler is limited by the lowest frequency Rademacher function in the signaling set. A single M segment can be used to implement the M-ary matched filter. By increasing the number of convolver segments, signaling sets with better performance in the presence of a Doppler frequency shift can be implemented.
- Command, Control and Communications Systems