零阶保持器（ZOH）的幅频特性

零阶保持器

脉冲响应

syms x   %  Sample Time = 1

fplot(heaviside(x)-heaviside(x-1), [-2, 2])

脉冲响应的传递函数

s = tf('s');

G = (1-exp(-2*s))/s ;%  采样周期T=2s

bode(G)

w = 0:0.001:500;

T = 0.1;

G = T*sin(w*T/2).*exp(-1j*w*T/2)./(w*T/2);

plot(w,abs(G))

title("ZOH的相频特性")

xlabel('w/(rad/s)')

ylabel('|G(jw)|')

figure

plot(w,angle(G))

title("ZOH的幅频特性")

xlabel('w/(rad/s)')

ylabel('\angleG(jw)')

w = logspace(1,3,1000);

T = 0.1;

G = T*sin(w*T/2).*exp(-1j*w*T/2)./(w*T/2);

plot(w,[abs(G);angle(G)])

axis([0 1000 -5 0.2])

title('the Frequency Characteriistic of ZOH')

xlabel('w (rad/s)')

ylabel('Amplitude-Phase-frequency characteristic') 

w = logspace(1,3,1000);

T = 0.1; %sample time

G = T*sin(w*T/2).*exp(-1j*w*T/2)./(w*T/2);

figure % new figure

[hAx,hLine1,hLine2] = plotyy(w,abs(G),w,angle(G));

title('the Frequency Characteriistic of ZOH')

xlabel('w (rad/s)')

ylabel(hAx(1),'Amplitude-frequency characteristic') % left y-axis 

ylabel(hAx(2),'Phase-frequency characteristic') % right y-axis

由上可以总结：

零阶保持器的相频特性呈锯齿状，也被称为ZOH的开关特性；另外，ZOH有许多小旁瓣，整体呈低通滤波

零阶保持器的滞后特性