FMP: a new digital FM scheme with optimized noncoherent detectability and inherent insensitivity to fadings

The author describes frequency modulation with pulse spreading (FMP) by a chirp filter, a method that optimizes the free Euclidian distance and noncoherent detectability of conventional digital FM schemes. In contrast to conventional schemes, a limiter discriminator receiver with dechirp filter and MLSE (maximum-likelihood sequence estimation) asymptotically approaches the performance of the coherent maximum-likelihood receiver at all modulation indices. A novel threshold extension receiver is proposed, which extends the superior asymptotic performance of the limiter discriminator by 6 to 8 dB, to E_b/N_o<4 dB. The error performance of this receiver is analyzed for an uncoded binary scheme with threshold decoding. The best system outperforms phase-shift keying by 5.8 dB at E _b/N_o=5 dB. Due to the time diversity introduced by the transmit chirp filter, the modulation scheme is inherently insensitive to fading