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How to see FT in more close picture.

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Hoon
Hoon 2015-9-9
评论： Hoon 2015-9-9
below is my code
--------------------------
lam=1552; %%%nm
lamd=lam*10^(-9); %%m
c=3e8;
freq=c/lamd; %%Hz
gbps=32e9; %%Hz
tb=1/gbps; %%s
lng=10; %%km
beta=0.1;
deltaf=beta/2/tb;
disp=0.088/4*(lam-(1317^4)/(lam^3)); %%ps/(nm*km)
deltat=-disp*lng*c*(10^9)*deltaf/(freq^2); %%ps
%%%%%%%%%%%%%%FFT
L=80e-11; %%%spatial extent
dt=1e-13; %%1 second - sample spacing
N=L/dt; %%% number of samples
t=(-N/2:N/2-1)*dt;
f=(-N/2:N/2-1)/(N*dt);
hfunct=sinc(t/pi/tb);
figure();plot(t,hfunct); %%%confirmed
hfft=fftshift(fft(fftshift(hfunct)))*dt;
NN=10;
fv=f(N/4:3*N/4-1);
hv=hfft(N/4:3*N/4-1);
figure();plot(fv,hv);
------------------------
The important part is after FFT.
when I transformed sinc function, it should give signum fuction, and it did. But the problem is, it looks like as if it were taken from very far distance.
How do I see FT graph more closely?

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采纳的回答

Walter Roberson
Walter Roberson 2015-9-9
L = length(fv);
subwindowidx = floor(L*3/8):ceil(L*5/8); %an area around the centre
plot(fv(subwindowidx), hv(subwindowidx));
  1 个评论
Hoon
Hoon 2015-9-9
So, all I got is reducing the window.
There is no way I can reduce window, and enhance resolution (i.e., reducing df) simultaneously?

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