Research Of Adaptive Equalization Algorithm In Microwave Channel

Transmission channels are usually unideal in actual microwave communication systems.Multipath transmission is the main factor of many adverse factors which produce the Inter Symbol Interference(ISI).In order to improve communication quality,mitigate ISI.Equalization techniques are usually used at the receiver to offset the effects of the channel response.Because the channel response changes over time,the method is to use equalization technology to compensate the transmission characteristics of the channel.Engineering applications usually use adaptive equalizers at the receiver to process the received signals.Traditional adaptive equalization algorithms include Least Mena-Square(LMS),Recursive Least-Squares(RLS),Constant Module Algorithm(CMA).The first two algorithms require some priori knowledge of channel;but the last one dosen't,which belonged to blind equalization(BE).QAM modulation is widely used in long distance microwave communication,Adaptive equalization can solve many adverse effects of the channel response,for example,some components in the channel have excessive delay,inter symbol interference,multipath effect,etc.Due to the time-varying of wireless transmission environment,the equalization technology must have adaptive ability to adapt to the time-varying multi-path transmission of channel.My work item belongs to special communication.Regular communication and special use environments are bose important.In some special communication situations,it is necessary for the receiver equipment to complete the blind equalization of QAM signal when it cannot accept the training sequence.Realize passive reception of microwave signal at only one end.So,an efficient blind equalizer which can be used in engineering is necessary.In addition,there are many more application fields of adaptive equalization and blind equalization technology.For example,many wireless point-to-point networks such as seismic monitoring system.Firstly,thesis briefly introduced the theory of adaptive equalization algorithm,including the introduction of the digital microwave channel model,the causes of ISI and common solutions;After that,the structures of several common adaptive equalizers are introduced,including the linear transverse equalizer,Decision feedback equalizer and Score interval equalizer,etc;Then focus on the analysis of typical adaptive equalization and blind equalization algorithms,include Least Mena-Square,Recursive Least-Squares and Constant Module Algorithm.Channels with multipath and white noise effects and test signal are simulated by matlab,then the convergence and steady-state performance of these algorithms are studied when the signal passes through the channel.The characteristics and application environment of these algorithms are obtained.This thesis studies the new improvement algorithm of constant mode blind equalization algorithm by combining traditional adaptive equalization algorithm and blind equalization algorithm,also with some more effective engineering optimization methods.The required environment and QAM signal are simulated by matlab.Then we verified the new improved algorithm.Theoretical analysis and simulation show that the improved algorithm has better balance effect and lower computational complexity.That is to say,it has more engineering practical significance.Not just in the field of special communication,at present,the technology of long distance digital microwave transmission link is developing to high speed and large capacity.Blind equalization algorithm which without relying on training sequence can improve the utilization of effective bandwidth.In addition,the problem of inter-code crosstalk caused by complex application environment and large capacity itself is more complex.Therefore,the study of blind equalization class equalization algorithm has important theoretical and practical significance.It is a research subject with great development prospect.