[考題] 普考-通信系統概要/傅立葉轉換
第一題 題目如下:http://ppt.cc/5~Bg
【一般指令】
第一題我做出來答案為
F{g(t)}=G(f)=δ(f)+3/2[δ(f-1000)+δ(f+1000)]+[δ(f-2000)+δ(f+2000)]
由於沒有給正確解答 不知道我的答案是否正確?
(二)(三)小題則是不知從何下手 請高手幫忙了
第二題 題目如下:http://ppt.cc/hsr9
我的作法為:
(一) F{g(t)}=∫g(t)exp(-j2πf)dt
=∫4*exp(-j2πft)dt (由-2積到+2)
= 4*2*∫cos(2πft) dt
= 4*2*[sin(2πft)/2πf]| (由-2積到+2)
= 4*4*[sin(4πft)/4πf]
= 16sinc(4f)
請問對嗎??
(二) F{g2(t)}=F{g1(t-6)}+F{g1(t+6)}
= 16sinc(4f)exp(-j2πf6)+16sin(4f)exp[-j2πf(-6)]
= 16sinc(4f)[exp(-j2πf6)+exp[-j2πf(-6)]]
= 16sinc(4f)[exp(-j12πf)+exp(j12πf)]
= 32sinc(4f)cos(12πf)
請問對嗎??
(三) F{g3(t)} = F{g1(2t)}+F{g1(4t)}
=1/|2| *16sinc(4f/2) + 1/|4| * 16sinc(4f/4)
= 8sinc(2f)+4sinc(f)
請問對嗎??
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