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 Ðźŷת 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