NON-RECURSIVE IN-PHASE AND QUADRATURE DISCRETE FILTER

摘要

ABSTRACT:A non-recursive discrete filter for simultaneouslyrealizing for example two band-pass filter characteristicsstarting from a given lowpass transfer characteristic, whereinone bandpass filter has an in-phase transfer characteristicand the other filter the quadrature transfer characteristicof this in-phase filter. The central frequency of thesefilters is fo and the output sampling frequency is fs =8fo.This discrete filter comprises multiplying means in whichinput signal samples x(n) are modified by an associatedfilter coefficient a(i) for generating modified input signalsamples z(n,i) = a(i)x(n-i). The coefficients a(i) arethe same for both transfer characteristics and are given by:a(i) = h1(i) ¦ cos (.pi.i/4) ¦ for cos(.pi.i/4) ? 0a(i) = h1(i) ¦ sin (.pi.i/4) ¦ for cos(.pi.i/4) = 0wherein h1(i) represents the discrete impulse response ofthe lowpass filter.To realize the in-phase transfer characteristicthe samples z(n,i) are thereafter multiplied by a factorsgn[cos (.pi.i/4)] and the products thus obtained are accumulated.This results in the output signal sampleTo realize the quadrature transfer characteristicthe samples z(n,i) are thereafter multiplied by a factorsgn[sin(.pi.i/4)] and the products thus obtained areaccumulated. This results in the output signal sample- 22 -