Research On Multi-h CPM Signal Parameter Estimation And Blind Demodulation Technologies For Satellite Communication

Continuous Phase Modulation(CPM)signal conforms to the development trend of modern communication to improve data transmission rate and reduce power consumption due to its good constant envelope characteristics and high bandwidth and power utilization.It has a high adoption value in space,telemetry and other ultra-long distance high-speed data transmission system.With the development of CPM technology becoming more mature,multi-CPMh technology developed on this basis has almost all the advantages of single-CPMh signal,while showing more excellent characteristics in frequency band utilization than single-CPMh signal.Multi-CPMh signals have two or more modulation indices that change in a certain period,which not only increases the concealment,but also increases the structural complexity and difficulty of blind demodulation,and blocks the promotion and development of multi-h CPM signal.Aiming at the effective processing of CPM signals in MIL-STD-188-181 C in noncooperative receiving environment,this paper studies the parameter estimation and synchronous demodulation technology of CPM system,mainly including the following three aspects:Firstly,the principle of single-h and multi-CPMh signal is studied respectively,including signal modulation model and phase state analysis.In the CPM modulation system,the data to be transmitted is attached to the phase of time change,and the CPM signal phase is memorizable.Based on this,the research content of phase characteristics and phase grid diagram are given.Then,the linear decomposition,spectrum and cyclic spectrum characteristics of CPM signal are analyzed.Secondly,the modulation parameter estimation algorithms for single-h and multi-h CPM signals are studied.This paper studies the estimation methods of modulation order,correlation length,pulse type and other parameters of single-CPMh signal,and next mainly analyzes four algorithms for modulation index estimation,which are periodic estimation algorithm,high-order cumulant estimation algorithm,cyclic spectrum estimation algorithm and a new improved algorithm.The improved algorithm uses the spectral characteristics of CPM signal’s first-order cyclic moment at a specific cyclic frequency interface to estimate the modulation index.In this part,the algorithm principle and formula verification are given,and the performance of modulation parameter estimation is analyzed.Through comparison,it is found that the improved algorithm can accurately estimate single-CPMh signals at very low SNR.For multi-CPMh signals,the SNR requirement of multi-CPMh is 5d B higher than that of existing algorithms.Finally,the demodulation algorithm of CPM signal is studied.In this paper,a synchronization algorithm based on pilot sequence is proposed,including carrier frequency estimation,frequency offset estimation,guidance sequence decision,and frame synchronization.Correct parameter estimation and signal synchronization are the premise of successful blind demodulation.Based on the above,for MIL-STD-188-181 C protocol and the requirements of the subject,the maximum likelihood demodulation algorithm based on Viterbi decoding is firstly adopted.Then,in order to pay less cost for more reliable and more stable communication,the optimal sequence detection algorithm and the suboptimal sequence detection algorithm based on Laurent decomposition are analyzed.The experimental simulation results show that the complexity of the optimized algorithm is greatly reduced compared with the original algorithm,and the time required for demodulation is significantly reduced.