分数延时滤波器在宽带阵列雷达中应用

Application of Fractional Delay Filters in Wideband Array Radar

阵列雷达常采用移相法形成波束,但在宽带情况下,此方法形成的波束存在波束空间色散问题。解决此问题最基本的方法是基于时域多抽头数字延时法和频域波束形成方法,本文介绍采用时域多抽头数字延时法来改善波束空间色散问题。文中分析了为何采用时域多抽头数字延时法能解决此问题的缘由。时域数字延时方法的延时滤波器设计有很多种方法,文中给出了频域设计(海宁窗)和最大平坦方法两种设计滤波器方法的特性,对比两种方法的优劣,并用Matlab仿真对比了在延时相同,阶数相同情况下,选择频域设计(海宁窗)方法比最大平坦度方法滤波器特性要好,但工程实现时,频域设计(海宁窗)方法比最大平坦度方法计算复杂,所以要根据算法要求的实时性及运算平台选择不同的方法。工程实现时还可采用子阵划分对阵列进行简化处理。

The phase shift method is usually used by array radar for beam forming.However,the beams generated through phase shift have spatial dispersion when the involved radar signals have large bandwidth.The most basic methods to solve the dispersion problem are time-domain multi-tap digital delay method and frequency-domain beam-forming method.The former method is adopted in this paper.Firstly,the reason why the time-domain multi-tap digital delay method can solve the spatial dispersion problem is given.There are many delay filter designs that can be employed by the time-domain digital delay method.In this paper,the characteristics of both frequency domain filter design(Hanning window)and maximally-flat filter design are discussed.In addition,the two filter designs are compared.The Matlab simulation results show that the frequency domain filter design is better than the maximally-flat filter design under same delay and filter order conditions.However,the frequency domain filter design requires more complex computation in engineering implementation.Therefore,the filter design should be selected based on actual real-time requirements and computing platform.In addition,subarray division can be employed to simplify the array in engineering implementation.