外文文獻(xiàn)及翻譯：基于lms自適應(yīng)濾波器在直達(dá)波消除中的運(yùn)用usinglmsadaptivefilterindirectwavecancellation(編輯修改稿)
2024-12-22 19:42 本頁面
【文章內(nèi)容簡介】 ed the target’s echo as well as the wave from the broadcast station through multipath propagation effect. As the radar crosssection(RCS) of the target is uaually very small, the echo wave of the target is very weak pared with the multipath propagation wave. This is the reason why the target detection bees a challenging task under this circumstance. The existent experiments of passive radar used some different ways[2,3], all of which need to use special hardware to perform direct entering wave cancellation, to solve this problem. However, it is possible to make this task by software. Over the last several years, the adaptive signal processing has been an active area of research, more and more theories were introduced into practical applications. Examples of some important area include linear prediction, echo wave cancellation, channel equalization, etc. Those examples remind us how to use the adaptive signal processing into direct wave cancellation. After analyzing the behavior of the direct wave, the leastmeansquare (LMS) adaptive filter is applied to solve this problem. 1 The Mode of Direct Wave To analyze this problem in detail, it is necessary to set up a correct model of direct wave. The behavior of the direct wave is very like the multipath propagation of radio channel, both of them are posed of distributed amplitude at different time delays in parison of the first arriving ray, so the model of mutipath propagation of the radio channel can be introduced, thus the impulse response of the direct wave can be expressed as[4] 10( ) ( )nN jnnnh a e?? ? ? ?????? (1) Where na is the amplitude,τnis the time delay, n? isthe phase shift, andN is the total number of multipath propagation ponents. Because we have ( c os si n )njn n n na e a j? ???? (2) Equation (1) can be considered as a continuous time FIR filter’s impulse response. In the passive radar system, the output of the receiver is digitalized at the digital radar signal processor. By introducing a new plex parameteraito substitute the value of Eq.(2), Eq.(1) is changed toztransform representation given as 10()N nnnH z a z? ???? (3) This is the model of the direct wave inZdomain, if Eq.(3) is taken as the transfer function of an FIR filter. The impulse response is known, and the direct wave could be estimated. Thus the problem of adaptive direct wave cancellation bees a problem of how to get the factoranin Eq.(3), . how to identify the model of direct wave. There are several different ways to plete this task. Because of its FIR structure, the LMS adaptive filter method can be introduced to solve the problem. 2 Implementing LMS Adaptive Filter In Direct Wave Cancellation Since Widrow and Hoff developed the LMS arithmetic[5]in 1960, LMS arithmetic has been widely used in adaptive filters. A significant feature of the LMS
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