Research On Key Techniques For Receiving The Short Burst Qam Signals Uncooperatively

With the development of communication technology, the demodulation for short burst signal both have extremely important theoretic and practical values, not only in the civil field but in the military field. Because of QAM signals being increasingly widely used, the uncooperative reception to the short burst QAM signals has become an important research subject in the uncooperative communication. This dissertation mainly probes into the study of key technology in the uncooperative reception. The primary contents are as follows:1 The feedforward timing error estimation algorithm for short burst QAM signal. At first, the timing error estimation methods under the mini rolloff-factor is studied, based on the constant norm characteristics to QAM signals, the timing error estimation algorithm on constant modulus property is extending can reason out the timing error estimation algorithm to the constant norm. In addition, that using optimal non-linear transformation in carrier synchronization transforms the QAM signals into that with Constant Modulus Property, can also achieve a new timing error estimation algorithm based on the signal constant modulus property. It is showed that, through simulation analysis, the improved algorithm in this article has greater advantage under the condition of the smaller rolloff-factor.2. The timing-error correction technique for short-term burst QAM signal. With high realization precision and low calculation complexity, Farrow Structure often become a good choice. The Langrange fractional space time-delay filtering is always acttracted by people, because it is easy to be realized and has better amplitude frequency response. Emulation reveals that interceptive Lagrange interpolation timing error correction filter has broader bandwidth, while it losses the performance of amplitude frequency fesponse.3. Analysis on fast algorithm for blind equalization based on restriction optimizatioin theory for short-term burst QAM signal. According to signal detection algorithm of Semidefinite programming, aiming at 16QAM signal, and combining withε-blind equalization criterion, this article provides a new direct blindchannel equalization algorithm. This algorithm will realize the blind channel equalization to 16QAM signal. Eventually, the KKT(Karush-Kuhn-Tucker) condition based on the optimization theory, a looser sufficient and necessary condition than traditional one will be put forward to realize the blind channel optimum equalization for 16QAM.4. Feedforward frequency offset estimation algorithm for short burst QAM signal. Aiming at short burst signal and combining with the feature of uncooperation reception, this article analyses the carrier frequency offset Estimation Algorithm of forward non-data aided in high order QAM signal carrier wave synchronization. Classic feedforward frequency offset estimation based on maximum likelihood can be approached via frequency offset estimation algorithm of least squares under a certain condition. The frequency offset estimation based on least squares has more application range than that directly based on maximum likelihood. The last emulation shows that because of fully using the constellation message of modulation signal, the frequency offset estimation algorithm based on non-linear least squares can approach to MCRB well with its estimation variance.5. Analysis of feedforward carrier wave phase-error algorithm of short burst QAM signal. At first, based on the CPS phase-error estimation algorithm and using local symmetry of cyclic cross-correlation function, this article considers that symmetry search algorithm can further improve the performance of original algorithm. But the emulation indicates that on the impact of phase quantization and threshold alternation, the improvement of the algorithm performance is unconspicuous, which has little increase only under low signal-to-noise and with less performance than original algorithm under high signal-to-noise. Whereafter using some character of wavelet transform in cyclic cross-correlation function, this article puts forward improved phase-error estimation algorithm. Emulation analysis shows that if right wavelet function is chosen, the performance of phase-error estimation algorithm based on signal constellation phase character can be improved obviously.