Wideband partial response CPM demodulation via multirate frequency transformations and decision feedback equalization

Abstract

Continuous phase modulation (CPM) is a popular frequency modulation technique used in mobile communications due to its power efficiency and constant modulus properties. Conventional narrowband CPM demodulation employs the Viterbi algorithm after phase demodulation and requires that the phase states be rational and contain additive white noise. The complexity of the Viterbi approach further increases with the number of phase states. Frequency discrimination approaches that estimate the instantaneous frequency provide a simpler suboptimal approach but are primarily for full response CPM and are not well known for wideband partial response CPM. In this paper, we investigate an approach that combines multirate frequency transformations for wideband CPM demodulation with decision feedback equalization for memory removal. This combined approach avoids the problems of complexity and restrictive requirements of the Viterbi approach. Simulation results are used to demonstrate the validity of the combined approach.

Research on an Optimization Method for a Partially Responsive Continuous Phase Modulated (CPM) Signal Based on an Optimal Generic Function

“…The partial response waveform artificially introduces inter-symbol interference at the symbol sampling time in order to improve the frequency band utilization and accelerate attenuation of the "tail" of the transmitted signal waveform [7][8][9][10]. The interference is then eliminated before the receiver generates the decision waveform to improve the spectral signature.…”