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subplot?2,2,2?, stem?k,Xa,'filled'?,title('Ä£'); subplot?2,2,4?, stem?k,Xn,'filled'?,title('Ïà½Ç');
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2.3.4 ¸´Ö¸ÊýÐòÁÐ
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Im{f (k )}= rk sin(wk)Ϊf?k?µÄÐ鲿
¿É¼û£¬¸´Ö¸ÊýÐòÁÐf?k?µÄʵ²¿ºÍÐ鲿·Ö±ðΪ·ù¶È°´Ö¸Êý¹æÂɱ仯µÄÕýÏÒÐòÁС£µ±r£¾1ʱ£¬f?k?µÄʵ²¿ºÍÐ鲿·Ö±ðΪָÊýÔö³¤µÄÕýÏÒÐòÁУ»µ±0£¼r£¼1ʱ£¬f?k?µÄʵ²¿ºÍÐ鲿·Ö±ðΪָÊýË¥¼õµÄÕýÏÒÐòÁУ»µ±r?1ʱ£¬f?k?µÄʵ²¿ºÍÐ鲿·Ö±ðΪµÈ·ùÕýÏÒÐòÁС£
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function dfzsu?n1,n2,r,w? %n1:»æÖƲ¨ÐεÄÐéÖ¸ÊýÐòÁÐµÄÆðʼʱ¼äÐòºÅ
%n2£º»æÖƲ¨ÐεÄÐéÖ¸ÊýÐòÁеÄÖÕֹʱ¼äÐòºÅ %w£ºÐéÖ¸ÊýÐòÁÐµÄ½ÇÆµÂÊ %r: Ö¸ÊýÐòÁеĵ×Êý
k?n1:n2;
f?(r*exp(i*w))k;
Xr?real?f?; Xi?imag?f?; Xa?abs?f?; Xn?angle?f?;
subplot?2,2,1?, stem?k,Xr,'filled'?,title('ʵ²¿'); subplot?2,2,3?, stem?k,Xi,'filled'?,title('Ð鲿'); subplot?2,2,2?, stem?k,Xa,'filled'?,title('Ä£'); subplot?2,2,4?, stem?k,Xn,'filled'?,title('Ïà½Ç');
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Àëɢʱ¼äÐòÁÐf1(k) ºÍf2(k)µÄ¾í»ýºÍ¶¨ÒåΪ:
f(k)?f1(k)*f2(k)??f1(k)?f2(k?i),i?R £¨2-8£© ÔÚÀëÉ¢ÐźÅÓëϵͳµÄ·ÖÎö¹ý³ÌÖУ¬ÎÒÃÇÓÐÁ½¸öÓë¾í»ýºÍÏà¹ØµÄÖØÒª½áÂÛ£¬Õâ¾ÍÊÇ£º
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MATLABµÄconv()º¯Êý¿ÉÒÔ°ïÖúÎÒÃÇ¿ìËÙÇó³öÁ½¸öÀëÉ¢ÐòÁеľí»ýºÍ¡£convº¯ÊýµÄµ÷ÓøñʽΪ£ºf ? conv ?f1,f2?
ÆäÖÐf1Ϊ°üº¬ÐòÁÐf1(k)µÄ·ÇÁãÑùÖµµãµÄÐÐÏòÁ¿£¬f2Ϊ°üº¬ÐòÁÐf2(k)µÄ·ÇÁãÑùÖµµãµÄÐÐÏòÁ¿£¬ÏòÁ¿fÔò·µ»ØÐòÁÐset?gca,'position',h?µÄËùÓзÇÁãÑùÖµµãÐÐÏòÁ¿¡£
ÏÂÃæÊÇÀûÓÃMATLAB¼ÆËãÁ½ÀëÉ¢ÐòÁоí»ýºÍf(k)?f1(k)*f2(k)µÄʵÓú¯Êýdconv? ?£¬¸Ã³ÌÐòÔÚ¼ÆËã³ö¾í»ýºÍf(k)µÄͬʱ£¬»¹»æ³öÐòÁÐf1(k) ¡¢f2(k)ºÍf(k)µÄʱÓò²¨ÐÎͼ£¬²¢·µ»Øf(k)µÄ·ÇÁãÑùÖµµãµÄ¶ÔÓ¦ÏòÁ¿¡£
function ?f,k??dconv?f1,f2,k1,k2? % The function of compute f?f1*f2
% f: ¾í»ýºÍÐòÁÐf(k)¶ÔÓ¦µÄ·ÇÁãÑùÖµÏòÁ¿ % k£º ÐòÁÐf(k)µÄ¶ÔÓ¦ÐòºÅÏòÁ¿ % f1: ÐòÁÐf1(k)·ÇÁãÑùÖµÏòÁ¿ % f2: ÐòÁÐf2(k)µÄ·ÇÁãÑùÖµÏòÁ¿ % k1: ÐòÁÐf1(k)µÄ¶ÔÓ¦ÐòºÅÏòÁ¿ % k2: ÐòÁÐf2(k)µÄ¶ÔÓ¦ÐòºÅÏòÁ¿
f?conv?f1,f2? %¼ÆËãÐòÁÐf1Óëf2µÄ¾í»ýºÍf k0?k1?1??k2?1?; %¼ÆËãÐòÁÐf·ÇÁãÑùÖµµÄÆðµãλÖà k3?length?f1??length?f2??2; %¼ÆËã¾í»ýºÍfµÄ·ÇÁãÑùÖµµÄ¿í¶È
k?k0:k0?k3 %È·¶¨¾í»ýºÍf·ÇÁãÑùÖµµÄÐòºÅÏòÁ¿
stem?k1,f1?
stem?k1,f1? %ÔÚ×Óͼ1»æÐòÁÐf1(k)ʱÓò²¨ÐÎͼ title?'f1?k?'? xlabel?'k'? ylabel?'f1?k?'? subplot?2,2,2?
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stem?k,f?; %ÔÚ×Óͼ3»æÐòÁÐf(k)µÄ²¨ÐÎͼ title('f?k?f1?k?Óëf2?k?µÄ¾í»ýºÍf?k?')xlabel?'k'? ylabel?'f?k?'?
h?get?gca,'position'?; h?3??2.5*h?3?;
set?gca,'position',h? %½«µÚÈý¸ö×ÓͼµÄºá×ø±ê·¶Î§À©ÎªÔÀ´µÄ2.5±¶
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