具有近似线性相位特性的多相波数字滤波器的设计

不考虑相位失真,而要求满足比较苛刻的振幅特性的时候,和FIR滤波器比较起来,采用 IIR 滤波器,计算量要小很多.但对某些IIR滤波器,采取适当的方法,也可以使其相位失真变得很小.本文提出一种新的设计方法,用来设计振幅响应完全满足设计要求,而相位特性用Chebyshev 近似来实现的多相波数字滤波器.这种方法的关键在于确定通带中的若干衰减零点.文中对需要的最小衰减零点数作了估计.实例表明,用这种方法设计的滤波器,时延小,相位特性非常接近线性.

DESIGN OF POLYPHASE WAVE DIGITAL FILTERS WITH APPROXIMATELY LINEAR PHASE

It is well known that 1IR filters require very few computations, comonred with FIR filters, in order to meet stringent magnitude specifications when the phase distortion can be tolerated. An approximately linear phase, however, can be also obtained with the IIR filter by making use of a technique without increasing complexity. Based on a certain number of attenuation zeros in the pass band, a new approach is developed for the design of polyphase wave digital filters with exact magnitude responses and Cheby.shev approximation of the desired phase responses. The minimum number of attenuation zeros is estimated, and two examples are given.