看板Electronics
标 题Re: [问题] 请教二个讯号与系统的问题
发信站I-Shou University BBS (Wed Dec 21 23:23:50 2005)
转信站ptt!ctu-reader!Spring!ctu-gate!news.nctu!news.nsysu!news.isu!isu
※ 引述《[email protected] (找寻爱的定义)》之铭言：
> 1. x(t)=tu(t)
U(w)=1/jw+πδ(w)
∵tf(t)←→jdF(w)/dw
∴X(w)=jd/dw[1/jw+πδ(w)]
> (1)(t-2)x(t-2)
t-shifting:
F[(t-2)x(t-2)]=e^-jw2˙X(w)
(2)e^-jw0tdx(t)/dt
F[dx(t)/dt]=(jw)X(w)
frequency shifting:
F[e^-jw0tdx(t)/dt][j(w-w0)]X(w-w0)
2. x(t)←→jw/(w^2-j3w-2)
> (1)x(2t+1)=x(2(t+1/2))
time shifting:
F[x(t+1/2)]=e^jw1/2˙[jw/(w2-j3w-2)]
scaling:
F[x(2t+1)]=F[x(2(t+1/2))]=1/|2|e^j(w/2)1/2˙[j(w/2)/((w/2)^2-j3(w/2)-2)]
> (2)x(t)*x(t-1)
F[x(t)*x(t-1)]=X(w)˙e^-jw1˙X(w)=e^-jw1˙[jw/(w^2-j3w-2)]^2
> 感谢指教 谢谢 <(_ _)>
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220 除了本身以外的因数有:
1, 2, 4, 5, 10, 11, 20, 22, 44, 55, 110
284 除了本身以外的因数有:
1, 2, 4,71,142
而
220=1+2+4+71+142
284=1+2+4+5+10+11+20+22+44+55+110
它们彼此付出了自己的全部而化成了对方....
adapted from MagicFox....
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