Research On The Low-complexity Demodulation And Synchronization Technology Of CPM Signals For Space-based Tracking Telemetry And Command System

Continuous Phase Modulation(CPM)is an advanced modulation technique with high-power and bandwidth occupancy.The power efficiency of the CPM signals could be improved by the memory effect,which is similar to Trellis Coded Modulation(TCM).The bandwidth efficiency also could be improved by the smooth effect among the symbols.Additionally,the constant-envelope property of CPM can improve the efficiency of nonlinear power amplifier.With lots of excellent features,CPM is very suitable for Space-based telemetry system,where the transmitting power and channel bandwidth are both limited.With the rapid development of Space-based telemetry technology,various CPM signal is introduced to different standards,however,CPM is still limited to few simple cases because of detection and synchronization complexity problem.In this thesis,we study intensively on the CPM's reduced-complexity transmission techniques from three aspects: the optimum design of CPM signal in different situations,low complexity demodulation and synchronization technology.The research achievements are as follows:1.We summarized the current application status of CPM signals in different telemetry standards and data chains;we then stated the research status of low complexity demodulation and synchronization technology;the advantages and disadvantages of existing detection algorithms are also analyzed.2.We studied the general approaches to present CPM signal and discussed the influence on signal with the different parameters;by contrast performance of different CPM and linear modulation signal in nonlinear satellite channel,we drawed the conclusion that the CPM has outstanding advantages and a great potential in Space-based telemetry.3.The optimum signal in high-speed telemetry case is presented through analysis and simulation;based on the special property of Shaped Offset Quadriphase Shift Keying-Type A(SOQPSK-A)signal,several detection algorithms(with and without channel coding)with low complexity are proposed.Compared with traditional detection algorithm,the proposed algorithms can reduce the implementation complexity effectively,while the performance loss is negligible.4.We obtained the overall channel capacity of CPM in multiple-users telemetry case by improving algorithm of the channel with memory;an interference suppression algorithm is proposed by simplifying the factor graph,the complexity of the resulting algorithm is significantly reduced with respect to that of optimal coherent algorithm with negligible performance loss;through recovering the non-linear phase,a detector employing the simple single pulse detector is proposed,the problem of adjacent channel interference is well avoided.5.For high-speed case and multiple-users case,synchronization algorithm based on feedback loop and pilot assisted are proposed respectively,the performance of the two algorithms are also analyzed in detail.