《数字信号处理》课程教学课件（2020讲稿）第五章 数字滤波器 §5-1 概述

h(t)yltconvolutionanalogfilterH(j2)Y(j2)X(j2)multiplication22digitalizationFromanalogfiltertodigital filtera(n)h(n)convolutiondigitalfilternnT!!HewX(emultiplicationMA2元2元2元wuTTT

x(t) t y(t) t analog filter convolution t h(t) X(j)  H(j)  multiplication Y(j)  digital filter convolution multiplication x(n) n y(n) n n h(n) digitalization X(e j )  2  H(e j )  2  Y(e j )  2  From analog filter to digital filter

Try NOT to be simple and naive!X(K)(nr0.6置零0.40.2X(n)IDFT230.8DTFT并没有真正完成滤波0.60.40.20.2200.40.60.83

0 0.2 0.4 0.6 0.8 1 0 2 4 6 8 X’(e j ) 0 1 2 3 4 5 6 7 8 9 0 0.2 0.4 0.6 0.8 1 1.2 1.4 X’(n) 0 1 2 3 4 5 6 7 8 9 0 2 4 6 8 X(k) Try NOT to be simple and naive! 置零 0 1 2 3 4 5 6 7 8 9 0 0.2 0.4 0.6 0.8 1 并没有真正完成滤波 IDFT DTFT x(n)