Baseband pulse shaping to reduce intersymbol interference in narrowband M-ary CPFSK signaling

Baseband pulse shaping is proposed to reduce intersymbol interference of M-ary Continuous Phase Frequency Shift Keyed (CPFSK) signals in narrowband channels. It is shown that the error rate performance of M-ary CPFSK signals with modulation index 1/M can be significantly improved by using a raised cosine baseband pulse. Three symbol by symbol detection techniques, namely, limiter discriminator detection, differentially coherent detection, and coherent detection with differential decoding, are considered separately for signal detection. A synchronization structure which is similar to one that is available for CPFSK signals is also suggested for M-ary pulse shaped signals with modulation index 1/M