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ͼ2.4(a) ͼ2.4(b)

½á¹ûͼ·Ö±ðÈçͼ2.4(a), (b)Ëùʾ£¬ÓÐͼ¿É¼ûÕâÁ½ÖÖ·½·¨ÊǵÈЧµÄ¡£µ«·½·¨2 ÏԵøüΪ¼òµ¥¡£ 5¡¢µ¥Î»Âö³åÐòÁÐ

¼È¿ÉÓÃones(1,n)ºÍzeros(1,n)ÃüÁҲ¿ÉÓÃÂß¼­ÅжÏÃüÁîÉú³ÉÂö³åÐòÁС£ [Àý2¡ª5]

ÔÚn?[?2,20]ÄÚÉú³Éµ¥Î»Âö³åÐòÁÐ?(n?3)¡£

·½·¨1£º n0=3; n=-2:20;

x=[zeros(1,5),1,zeros(1,17)]; stem(n,x);

axis([-2,20,0,1]);

ylabel('x(n)');xlabel('Time index n'); title('unitary pulse signal');

·½·¨2£º n0=3; n=-2:20;

x=(n-n0)==0; stem(n,x);

axis([-2,20,0,1]);

ylabel('x(n)');xlabel('Time index n'); title('unitary pulse signal');

ͼ2.5(a) ͼ2.5(b)

½á¹ûͼ·Ö±ðÈçͼ2.5(a), (b)Ëùʾ£¬ÓÐͼ¿É¼ûÕâÁ½ÖÖ·½·¨ÊǵÈЧµÄ¡£µ«·½·¨2 ÏԵøüΪ¼òµ¥¡£

6¡¢ÔëÉùÐòÁÐ

rand(1,N) ²úÉúN¸öÔÚ[0£¬1]Çø¼ä¾ùÔÈ·Ö²¼µÄ°×ÔëÉù¡£

randn(1,N) ²úÉúN¸ö¸ß˹·Ö²¼£¨¾ùֵΪ0£¬Ð­·½²îΪ1£©µÄ°×ÔëÉù¡£

¶þ ³£ÓÃÐźÅÔËËã

ÐòÁг£ÓÃÔËËãµÄMATLABʵÏÖÈç±í2-1Ëùʾ

ÐòÁг£ÓÃÔËËãµÄMATLABʵÏÖ ÔËËãÃû³Æ Ðźŷù¶È±ä»¯ ÐźÅʱÒÆ Ðźŷ­×ª ÐźÅÀÛ¼Ó Êýѧ±í´ïʽ MATLABʵÏÖ Y=alpha*x Y=[zeros(1,k),x] Y=flip(x) Y=cumsum(x) y(n)??x(n) y(n)?x(n?k) y(n)?x(?n) ny(n)?ÐźŲî·Ö£¨»ò½üËÆ΢·Ö ÐźÅÇóºÍ k????x(k) Y=diff(x) Y=sum(x(n1:n2)) y(n)?x(n?1)?x(n) n2n1y?Á½¸öÐźÅÏà¼Ó Á½¸öÐźÅÏà³Ë Á½¸öÐźží»ý ?x(n) Y=x1+x2 Y=x1*x2 Y=conv(x1,x2) 12(ny(n)?x1(n)?x2(n) y(n)?x1(n)x2(n) y(n)?k????x(k)x?1??k) Y=xcorr(x1,x2) Á½¸öÐźÅÏà¹Ø Rxx(m)?n????x(n)x2(n?m)

[Àý2¡ª6] ÀëÉ¢¾í»ý

Èôx(n)=[1,1,1,10,0]£¬¼ÆËãÀëÉ¢¾í»ýºÍy(n)?x(n)*x(n)£¬¼ûͼ2.6Ëùʾ¡£ x=[1,1,1,1,0,0]; y=conv(x,x);

subplot(2,1,1);stem([0:length(x)-1],x); ylabel('x(n)');xlabel('time index n'); title('discrete-time convolution');

subplot(2,1,2);stem([0:length(y)-1],y);

ylabel('y(n)=x(n)*x(n)');xlabel('time index n');

ͼ2.6 ÀëÉ¢¾í»ý

[Àý2¡ª7] Àëɢʱ¼äÐźÅ×ÔÏà¹Ø

Èôx(n)=[1,1,1,10,0]£¬¼ÆËãx(n)µÄ×ÔÏà¹Øº¯ÊýRxx(m)?x=[1,1,1,1,0,0];

y=xcor r(x,x);

subplot(2,1,1);stem([0:length(x)-1],x);

ylabel('x(n)');title('discrete-time correlation');

m=(length(y)-1)/2;

subplot(2,1,2);stem([-m:m],y);

ylabel('y(n)=rxx(n)'),xlabel('time index n');

n????x(n).x(n?m)¡£¼ûͼ2.6Ëùʾ¡£

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ͼ2.7 Àëɢʱ¼äÐźÅ×ÔÏà¹Ø [Àý2¡ª6] ¼ÆËãÀëÉ¢ÐźŵÄÄÜÁ¿Ó빦ÂÊ

ÒÑÖªÎÞÏÞ³¤ÐòÁÐx(n)?0.8nu(n)£¬¼ÆËãÇ°10µãµÄÄÜÁ¿Õ¼ÄÜÁ¿µÄ°Ù·Ö±È¡£

ÐòÁеÄÄÜÁ¿E??x(n)n?0?2??x(n)xn?0N?1n?0?*(n)

1ÐòÁеŦÂÊP?N?n?0N?11x(n)?N2?x(n)x*(n)0

Ç°10µãµÄÄÜÁ¿¼ÆËãÈçÏÂ

N=10; n=0:N-1; x=(0.8).^n; e=sum(abs(x).^2)

e=

2.7458 ¸ÃÐòÁÐ×ÜÄÜÁ¿£ºE?

E=1/(1-0.64) E=2.7778 e/E ans= 0.9885

?x(n)n?0?2?1?2.7778

1?0.64