Research On The Key Technology Of Satellite Communication Blind Demodulation Based On PCMA

Because of the doubled bandwidth efficiency and the strong ability to resist interception, Paired Carrier Multiple Access(PCMA) is being wildly used in military satellite and civil satellite communication. Based on actual data and many references, this thesis mainly focuses on modulation recognition, parameter estimation and blind separation of MPSK modulated PCMA signals,and then analyze and simulate the main algorithms. Considering the similarity of mixed BPSK signals and a QPSK signal,this thesis propose an approximate segments from signals based on ICA.The specific research work is as follows:(1)Aiming at the high similarity between PCMA signal and single-modulated signal in time domain and frequency domain, this thesis constructs a feature of similarity in high-order cumulants of signal-mixed signals. Then it uses the feature to distinguish PCMA signal from single-modulated signals. After that the thesis focuses on the modulation recognition of PCMA signals. The simulation used QPSK, 8PSK and 16 QAM single-mixed signals as inputs. Digital simulation result shows that the recognition rate is above 95% for signal whose CNR is more than 15 dB.(2)For the parameter estimation of PCMA signals, this thesis’ s main research work is focused on symbol rate estimation, carrier frequency estimation and initial phase estimation. Aiming at the symbol rate estimation the thesis researches on a cyclic autocorrelation based algorithm. The algorithm utilizes a spectral-peak enhanced process to get rid of interference peaks. Simulation result shows that the for PCMA signals whose CNR are above 5dB, the algorithms presents a ideal performance. As for the carrier parameter estimation of PCMA signals, the thesis starts with single modulated signals, studying the estimation algorithms of single signals, simulating the algorithm and analyzing the difference between single signal and PCMA signal, and then the thesis makes a comparison of single signals and PCMA signals. For example, for the estimation of carrier frequency, this thesis makes a transition from single signal’s zeros-crossing estimation to M times estimation; As for the estimation of initial carrier phase, the thesis firstly studies the V-V algorithm for single signals, and then simulates the supplementary data based algorithm of M times. The simulation shows that to mixed signals who have a better CNR than 18 dB, the estimation of carrier frequency and initial phase has a good performance.(3)As for the blind separation of PCMA signals, this thesis is inspired by the similarity of mixed BPSK and single QPSK. It studies an approximate transition from single channel to double channel for mixed BPSK signals which is supposed to have an accurate estimation of carrier frequency. Then the ICA algorithm is applied to the processed BPSK signal to separate the two components among. Simulation result shows that to equal-power mixed BPSK signals the BER can reach 0.4% at CNR 20 dB. Finally, the thesis constructs a state space model of PCMA signals, apply particle filter algorithm to PCMA signals and makes an simulation of BPSK,QPSK modulated PCMA signals.