Research On Baseband Processing Techniques Of Telemetry Multi-h CPM Signals

As spacecraft and launch vehicles perform more and more complex tasks in the field of telemetry,the problem of limited spectrum resources and channel bandwidth in wireless communication becomes more and more serious,and the traditional modulation method has been slightly inadequate.Multi-h continuous phase modulation has the advantages of high spectral efficiency,constant envelope and quick attenuation out of band,which makes it the research object of the new generation telemetry system.However,the application of the multi-h CPM signal is limited by the high demodulation complexity,and thus the research of low-complexity demodulation algorithms for the Multi-h CPM signal is necessary.This dissertation focuses on the modulation principle and low complexity demodulation algorithm of Multi-h CPM signal.The main contents are as follows:(1)In order to reduce the complexity of Multi-h CPM signal demodulation,a joint demodulation algorithm,called Laurent-FPT-RSSD is proposed,where Laurent decomposition,frequency pulse Truncation(FPT)and Reduce state sequence detection algorithm are combined in this algorithm.Laurent decomposition and the FPT algorithm are used to reduce the number of matched filters.Reduce state sequence detection algorithm and FPT algorithm are used to simplify the grid state.The front-end matched filter and back-end grid state are simplified.The simulation results show that the complexity of the proposed algorithm is reduced to 1/16 of that of the MLSD algorithm,while the performance of the proposed algorithm is only reduced by about0.7 d B compared with the MLSD algorithm.(2)A Multi-h CPM universal modulator with variable modulation scale and symbol rate is designed to meet the general needs of the telemetry system.In this modulator,the phase pulse with a large amount of calculation is stored in a ROM table,and the correlation phase and accumulation phase are realized by real-time calculation.The calculation of the correlation phase and accumulation phase of this modulator is independent of modulation scale and rate,and has good universality.The results of the function simulation and timing test show that the output waveform,frequency spectrum,and theoretical analysis of the modulator are consistent,which verifies that the modulator designed is correct.(3)A low complexity demodulator based on the sub-optimal solution of Laurent decomposition and frequency pulse truncation is designed and implemented on the FPGA hardware platform.The demodulator consists of a matched filter module based on a three-stage pipeline,a measurement calculation module based on the full parallel integration branch and a Viterbi backtracking decoding module based on the shift register.The results of the function simulation and timing test show that the demodulation performance of the demodulator is close to the simulation results,which verifies that the demodulator designed is correct.