《DSP using MATLAB》示例Example7.25

今天清明放假的第二天，早晨出去吃饭时天气有些阴，十点多开始“清明时节雨纷纷”了。

母亲远在他乡看孙子，挺劳累的。父亲照顾生病的爷爷……

我打算今天把《DSP using MATLAB》第7章结束，剩下的几个例子看不懂了，先跳过去。

ch7最后一个：

代码：

ws = 0.6*pi; wp = 0.75*pi;
Rp = 0.5; As = 50;
[delta1, delta2] = db2delta(Rp, As);
f = [ws, wp]/pi; m = [0, 1]; delta = [delta2, delta1];
delta

[N, f, m, weights] = firpmord(f, m, delta); N

h = firpm(N, f, m, weights);
[db, mag, pha, grd, w] = freqz_m(h, [1]);
delta_w = 2*pi/1000;
wsi = ws/delta_w; wpi = wp/delta_w;

Asd = -max(db(1:1:wsi))

N = N + 2
h = firpm(N, f, m, weights);
[db, mag, pha, grd, w] = freqz_m(h, [1]);
[Hr, ww, a, L] = Hr_Type1(h);
Asd = -max(db(1:1:wsi))

M = N + 1

　　运行结果：

注意：代码中让N+2，是为了保证滤波器阶数为偶数。最优M=29。