A Research Of Adaptive Equalizer In Digital Microwave Transmission System

For digital microwave communication systems exist at this stage due to the ISI channel attenuation problem, this thesis through the study of adaptive equalizer, the decision feedback equalizer and fractionally spaced equalizer to improve the structure design of a That the interval of sampling points with a decision feedback equalizer interval, the channel for distortion compensation. And analyzing and comparing the advantages and disadvantages of various adaptive algorithms, the constant modulus algorithm (CMA) do not need to send a training sequence, save spectrum resources, improve channel utilization, while CMA low computational complexity, the actual self-To adapt to the application of more and more balanced. However, the inherent shortcomings of constant modulus algorithm is slow convergence, step size selection in relatively small when the need for tens of thousands of iterations to gradually converge. Therefore, for lack of CMA algorithm, we use the correlation between the input signal vector of the characteristics of the CMA algorithm is improved, improved CMA algorithm is essentially a solution related to the adaptive algorithm, while the improved algorithm based on the input signal Feature to adjust the algorithm step size, it has a faster convergence rate, and have a good future in the convergence of the tracking performance.To a new fractionally spaced decision feedback equalizer structure, combined with the improved CMA algorithm, after the simulation, the improved communication system to join CMA fractionally spaced decision feedback equalizer, the signal reduction capability and convergence speed have a very Greatly improved.Finally, the characteristics of digital microwave system, using Simulink for digital microwave communication system and structure simulation, in this based on the introduction of different equalizer, concentrate on the different channels the performance of several equalizers, through the bit error rate And SNR performance of the simulation analysis, and further verify the new CMA equalizer in digital microwave communication system superiority.