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function xn=dconv(x1,x2) %ÈÎÒâÁ½ÐòÁоí»ý x11=-5:length(x1)-6; %É趨x1(n)µÄʱ¼äÏòÁ¿ x22=-5:length(x2)-6; %É趨x2(n)µÄʱ¼äÏòÁ¿ subplot(131),stem(x11,x1,¡¯fill¡¯),grid on; %»x1(n)µÄͼÏñ title('x1(n)=u(n)-u(n-4)'); xlabel('n'); ylabel('x(n)'); set(gca,'xtick',-20:20);
axis([(min(x11)-1),(max(x11)+1),(min(x1)-1),(max(x1)+1)]) subplot(132),stem(x22,x2,¡¯fill¡¯),grid on; %»x2(n)µÄͼÏñ title('x2(n)=u(n)-u(n-4)'); xlabel('n');ylabel('x(n)');
set(gca,'xtick',-20:20);
axis([(min(x22)-1),(max(x22)+1),(min(x2)-1),(max(x2)+1)]) xmin1=min(x11); xmax1=max(x11); xmin2=min(x22); xmax2=max(x22);
t=(xmax2+xmax1)-(xmin2+xmin1)+1; xx=-10:(t-6-5); %É趨x(n)µÄʱ¼äÏòÁ¿ xn=conv(x1,x2) %Çóx(n)=x1(n)*x2(n)
subplot(133),stem(xx,xn,¡¯fill¡¯),grid on; %»x(n)µÄͼÏñ title('x(n)=x1(n)*x2(n)') xlabel('n'); ylabel('x(n)');
set(gca,'xtick',-100:100);
axis([(min(xx)+5),(max(xx)-7),(min(xn)-0.5),(max(xn)+0.5)]) end
£¨2£©ÔÙ±àÖÆÒ»¸öMº¯Êýddconv(n),ÇóÁ½¸öÁ¬Ðøʱ¼äÐźŵľí»ý£¬ÄÜÊÇʵÏÖÁ½¸öÁ¬ÐøÐźŵľí»ýºÍ£¬²¢»æÖÆÕâÁ½¸öÐźŵÄʱÓò²¨ÐÎͼºÍ¾í»ýÖ®ºóµÄ²¨ÐÎͼ¡£±à³Ì˼·Èç¿òͼ2:
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function ft=ddconv(ft1,ft2) %ÈÎÒâÁ½¸öÁ¬ÐøÐźží»ý x1=-3:0.001:4;
x2=-3:0.001:4;
subplot(131),plot(x1,ft1),grid on; title('f1(t)=u(t+1/2)-u(t-2)');
axis([(min(x1)),(max(x1)),(min(ft1)-1),(max(ft1)+1)]) ; set(gca,'xtick',-3:1/2:4); xlabel('t'); ylabel('f(t)')
subplot(132),plot(x2,ft2),grid on; title('f2(t)=t/2[u(t)-u(t-2)]');
axis([(min(x2)),(max(x2)),(min(ft2)-1),(max(ft2)+1)]) ; xlabel('t'); ylabel('f(t)'); xmin1=min(x1); xmax1=max(x1); xmin2=min(x2); xmax2=max(x2);
t=(xmax2+xmax1)-(xmin2+xmin1);
xx=0-6:0.001:t-6; %×÷¾í»ýºóµÄʱ¼äÏòÁ¿£¬Òª¼õÈ¥Ôö¼ÓµÄÇø¼ä³¤¶È ft=0.001*conv(ft1,ft2); subplot(133),plot(xx,ft),grid on; title('f1(t)*f2(t)');
set(gca,'xtick',min(xx):1/2:max(xx)); xlabel('t'); ylabel('f(t)');
axis([(min(xx)+3),(max(xx)-3),(min(ft)-0.5),(max(ft)+0.5)]) end
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ÕâÁ½¸öÐòÁеľí»ýºÍ¡£ÔÚÕâ֮ǰÎÒÃDz»·ÁÔÙ±àÖÆÒ»¸öMº¯Êýrectanglestem(),ÈÃËü²úÉúxn=un-a-u(n-b)ÐòÁУ¬±àÖƵÄʱºòҪעÒâËüÊǸ¨Öúddconv()º¯Êý£¬ËùÒÔËüµÄÆðʼµãÒªÓëddconv()µÄÒ»Ö£¬ËùÒÔÆä³ÌÐòÈçÏ£º
function f= rectanglestem( a,b) k1=a-5;