代码:
M = 33; alpha = (M-1)/2; Dw = 2*pi/M; l = 0:M-1; wl = Dw*l; %Hdr = [0, 0, 1, 1]; wdl = [0, 0.6, 0.8, 1]; % Ideal Amp Res for plotting k1 = 0:floor((M-1)/2); k2 = floor((M-1)/2)+1:M-1; Hrs = [j*Dw*k1, -j*Dw*(M-k2)]; angH = [-alpha*Dw*k1, alpha*Dw*(M-k2)]; H = Hrs.*exp(j*angH); h = real(ifft(H, M)); %[db, mag, pha, grd, w] = freqz_m(h, 1); [Hr, ww, c, L] = Hr_Type3(h); %Plot figure('NumberTitle', 'off', 'Name', 'Exameple 7.19') set(gcf,'Color','white'); subplot(2,2,1); plot(wl(1:16)/pi, abs(Hrs(1:16))/pi, 'o', ww/pi, Hr/pi); axis([0, 1, -0.5, 1.5]); grid on; xlabel('frequency in pi nuits'); ylabel('Hr(k) in pi units'); title('Differentiator, frequency sampleing design: M=33'); subplot(2,2,2); stem(l, h); axis([-1, M, -1.1, 1.1]); grid on; xlabel('n'); ylabel('h(n)'); title('Impulse Response'); subplot(2,2,3); plot(w/pi, pha/pi); axis([0, 1, -1.5, 1.5]); grid on; xlabel('frequency in pi units'); ylabel('pha(w)'); title('Phase Response'); subplot(2,2,4); plot(w/pi, db); axis([0, 1, -60, 10]); grid on; xlabel('frequency in pi units'); ylabel('Decibels'); title('Magnitude Response');
运行结果:
从图看出,不是全频带(full-band)差分。