회로이론전자기사 · 2016년10월01일 · 34/100
34.v(t)=cos2πf0t을 Fourier 변환한 V(f)를 구하면?
1
V(t)=δ(f-f0)+δ(f+f0)
2
V(t)=π[δ(f-f0)+δ(f+f0)]
3
V(t)=1/2[δ(f-f0)+δ(f+f0)]정답
4
V(t)=2π[δ(f-f0)+δ(f+f0)]
해설
푸리에 변환시 cos2πft*cos2πf0t를 변환하는데 cos(A±B)=(cosAcosB∓sinAsinB)를 응용하여 1/2(2*cos2πft*cos2πf0t)=1/2{cos(2πft+2πf0t)+cos(2πft-2πf0t)}=1/2[cos2πt(f-f0)+cos2πt(f+f0)]=1/2[δ(f-f0)+δ(f+f0)]