Simplified coherent detection of bandwidth-efficient CPFSK/CPM modulations

A new unified approach is taken in which simple low-pass filters are used after quadrature demodulation, and are followed by a sampler and reduced-computation sequence estimation algorithm. As the number of samples per baud increases, optimal performance is closely approached. The computational complexity can be minimized by choosing a narrow filter that actually modifies the received signal shapes; the sequence estimation algorithm accounts for introduced ISI. It is shown for representative modulations that near-optimal performance can be achieved with simple low-pass filtering, just two samples per baud, and trellis search with only a few survivor paths.<>