| Signal in the process of acquisition and transmission will be subject to all kinds of noise, in order to reduce noise, conducive to the subsequent signal analysis, the need for signal denoising. During transmission, the signal using the conventional PSK and QAM modulation techniques can be more efficient use of scarce bandwidth resources at the receiving, in the receiver using a common software demodulator for the reception of the signal demodulation.In the aspect of signal denoising, several common signal denoising algorithms are studied, focusing on wavelet threshold denoising algorithm and wavelet packet threshold denoising algorithm. On the basis of common threshold functions, a new threshold function is presented. A speech denoising algorithm based on LMS adaptive noise cancellation and wavelet threshold is proposed to reduce the noise of speech signal. Firstly, use LMS adaptive noise cancellation to eliminate some noises to get a higher SNR speech signal and then denoise it with wavelet threshold algorithm. The experimental results show that the performance of the algorithm is good.In the aspect of signal demodulation, research on carrier synchronization algorithm based on phase locked loop,and give the nonlinear baseband processing functions of PSK and QAM modulation.Study on general symbol synchronization algorithm based on square method. The improved symbol synchronization algorithm use PLL purification to effectively overcome the jitter of the symbol clock after band pass filtering.For blind equalization technology, the variable step size of the modified constant modulus algorithm decision feedback equalizer is studied, which has fast convergent speed and smaller steady-state error, and correct the phase deflection.The AGC and demodulation correlation algorithms are connected into a whole loop to achieve the correct demodulation of several common PSK and QAM signals.After the wavelet packet threshold denoising is adopted, the demodulation error rate is lower. |
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