Inverse Fourier Transform of 1/(1+8e^3jw): A Contour Integration Approach

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SUMMARY

The inverse Fourier transform of the function 1/(1+8e^(3jw)) can be approached using contour integration, specifically the integral \(\frac{1}{2\pi i}\int_{-\infty}^{\infty} \frac{e^{iwx}}{1+8e^{3iw}}dw\). This method is suggested as a potentially more efficient alternative to partial fraction decomposition, which can be cumbersome. The discussion emphasizes the need to express the function in a suitable form for easier manipulation, such as A/(1+ae^(jw)) + B/(1+be^(jw)) + C/(1+ce^(jw)), where a, b, and c are less than 1. The participants also note that the simpler case of 1/(1+1/8e^(jw)) yields a straightforward result of (1/8)^n u[n].

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How do I find inverse Fourier transform of 1/(1+8e^3jw)??
Now, it would have been easier to find inverse of 1/(1+1/8e^jw), because that would be just (1/8)^n u[n]
i think i basically need a way to write 1/(1+8e^3jw) in a form described below:
A/(1+ae^(jw)) + B/(1+be^(jw) +C/(1+ce^(jw)
where a, b, c are less than 1.
How do I do that? partial fraction can be killing, because the process will be too long. Any other smarter methods?
 
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kolycholy said:
How do I find inverse Fourier transform of 1/(1+8e^3jw)??
Now, it would have been easier to find inverse of 1/(1+1/8e^jw), because that would be just (1/8)^n u[n]
i think i basically need a way to write 1/(1+8e^3jw) in a form described below:
A/(1+ae^(jw)) + B/(1+be^(jw) +C/(1+ce^(jw)
where a, b, c are less than 1.
How do I do that? partial fraction can be killing, because the process will be too long. Any other smarter methods?
find (2-e^(-jw))/(1+e^(-j3w)/8) inverse Fourier transform
 
kolycholy said:
How do I find inverse Fourier transform of 1/(1+8e^3jw)??
Now, it would have been easier to find inverse of 1/(1+1/8e^jw), because that would be just (1/8)^n u[n]
i think i basically need a way to write 1/(1+8e^3jw) in a form described below:
A/(1+ae^(jw)) + B/(1+be^(jw) +C/(1+ce^(jw)
where a, b, c are less than 1.
How do I do that? partial fraction can be killing, because the process will be too long. Any other smarter methods?

How about just muscle-through the contour integration:

[tex]\frac{1}{2\pi i}\int_{-\infty}^{\infty} \frac{e^{iwx}}{1+8e^{3iw}}dw[/tex]

I suspect that may be just a sum of residues if x>0 however I've not gone over it rigorously so I'm not sure. Just another possibility you may wish to consider.
 
Last edited:

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