Signal power in Matlab

[elmarconi]

hi all
I'm using the functions(fft,ifft) in a matlab code,theoretically signal power must not be changed before and after transformation according to Parsaval theorem.
But when calculating the signal power before and after using E{X^2},the power of the 2 signals aren't the same.
please can any body helping solving this issue.
Thanks

 

[hate]

Does your code filter your fft results?

 

[elmarconi]

No, without using any filter, just ifft only.
and compare between the signal power before and after the ifft

 

[hate]

Result of fft and ifft are complex numbers even though inputs may not be. Are you taking care of that?

 

[elmarconi]

it doesn't affect the signal power
E{X^2}, X is absolute.

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so it doesn't affect the power if the signal is complex or real

 

[hate]

I didn't say it affects the signal power, just wanted to make sure if you've taken it into consideration or not while calculating the power. If you're sure it's right then I can't offer anything else to check other than debuging a very simple case with just 'fft', 'ifft' and power calculation functions.