discrete inverse fourier transform

I have an = (T0* (exp(-T1)*(2*n*pi/T0*sin((n*pi*(T0-2))/(2*T0 ))-cos((n*pi*(T0-2))/(2*T0 )))+1))/(1+(2*n*pi/T0)^2);
and I need to preform a ifft using this formula
an.*exp(j*n*w0*x)
while n is between -25 to 25
what am I missing? I'm trying to use symsum and ifft functions and plot?

댓글 수: 8

Matt J
Matt J 2012년 10월 8일
Not sure why you would use SYMSUM. Why not just IFFT?
Rotem
Rotem 2012년 10월 8일
I have both n and x so I need symsum no? I can't just write ifft(an.*exp(j*n*w0*x)) because ifft doesn't accept sym
Matt J
Matt J 2012년 10월 8일
편집: Matt J 2012년 10월 8일
OK, but then why are using symbolic variables if ultimately you just want a plot? Or, if you insist on summing symbolically, with SYMSUM, why do you think you need IFFT as well?
In any case, we probably need to see your code and more of a description from you of what isn't working in it.
Star Strider
Star Strider 2012년 10월 8일
The symbolic inverse Fourier transform is ifourier.
Rotem
Rotem 2012년 10월 8일
I need to synthesize the temporary signal by reverse Fourier transform with a finite number of harmonies as described The following equation: Σ an.*exp(j*n*w0*x) from -N to N
while I found my an as i wrote before Im not sure about how am I supposed to find the inverse using the ifft function .. and am using the sym because its more generic that way
Matt J
Matt J 2012년 10월 9일
But once you've used SYMSUM to evaluate Σ an.*exp(j*n*w0*x) then what more is there to do? The expression above is the inverse fourier transform of an, is it not? Why does IFFT have to be part of this?
Walter Roberson
Walter Roberson 2012년 10월 9일
Note that ifourier is for the continuous inverse fourier, not the discrete.
Rotem
Rotem 2012년 10월 9일
편집: Rotem 2012년 10월 10일
yes but I got a stright line not a hrominc like I think I should get.. I am using the sum let say N = 25 and I get a symbolic answer of a vector of 41 in length using plot with a x vector eq in length to that of the answer and gets a stright line

댓글을 달려면 로그인하십시오.

답변 (0개)

카테고리

도움말 센터File Exchange에서 MATLAB에 대해 자세히 알아보기

질문:

2012년 10월 8일

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by