A modulation index estimation algorithm for multi-h CPM signals

Abstract

Continuous Phase Modulation (CPM) signal has been widely used in modern satellite, mobile communication and military communication system due to its good spectrum and power utilization and constant envelope characteristics. The premise of demodulation or jamming of CPM signal intercepted in military communication confrontation is the accurate estimation of signal parameters. Aiming at the difficulty and complexity of multi-h CPM signal modulation index estimation, this paper puts forward a kind of blind estimation algorithm of the modulation index based on first order cyclic moment and the second-order cyclic cumulants, using the first and second order cyclic properties in frequency domain on the spectral properties to signal parameter estimation. The estimation algorithm is suitable for both single h CPM signals and multi-h CPM signals, where the multi-h CPM requires the synchronization of the guidance sequence. Simulation results show that the algorithm has better performance under low signal-to-noise ratio with less symbols required. When the number of symbols is 128 and the signal-to-noise ratio is 15 dB, the accurate recognition rate of the multi-index CPM signal can reach 98% and the recognition rate can reach 99% with the allowable error of 1/32.