Differential detection of correlative encoded continuous phase modulation schemes using decision feedback

The authors generalise a differential detection technique, introduced elsewhere for a Gaussian minimum shift keying (GMSK) scheme, to include any correlative encoded continuous phase modulated (CECPM) signalling format. The proposed symbol-by-symbol receivers employ decision feedback to partially remove the effects of the destructive intersymbol interference (ISI) which corrupts the differentially detected CECPM signal. After achieving wider eye opening with the decision feedback, the outputs of the two or more differential detectors are jointly utilised to further improve the performance. As a typical example of the CECPM family of signals and because of its excellent spectral characteristics, the new receiver configurations employing up to 3-bit differential detectors have been applied to a tamed frequency modulation (TFM) signal. Bit error rate (BER) performance evaluation results have indicated that performance improvements of more than 5 dB (at BER=10 ^-4) over a conventionally differential detected TFM scheme are possible.<>