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t=0:2:4; x=cos(0.5*pi*t); plot(t,x) hold on; stem(t,x) t=0:0.5:4; x=cos(0.5*pi*t); plot(t,x) hold on; stem(t,x) wm=1; %升余弦脈沖信號帶寬 wc=wm; %頻率 Ts=pi/wm; %周期 ws=2.4*pi/Ts; %理想低通截止頻率 n=-100:100; %定義序列的長度是201 nTs=n*Ts %采樣點 f=sinc(nTs/pi); %抽樣信號 Dt=0.005;t=-20:Dt:20; fa=f*Ts*wc/pi*sinc((wc/pi)*(ones(length(nTs),1)*t-nTs'*ones(1,length(t)))); %信號重建 t1=0:0.5:4; f1=sinc(0.5*pi*t1); subplot(211); stem(t1,f1); xlabel('t1'); ylabel('f(t)'); title('f(t)的臨界采樣信號'); subplot(212); plot(t,fa) xlabel('t'); ylabel('x(t)'); title('由f(t)的臨界采樣信號重構x(t)'); grid;
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