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5 years, 10 months ago.
Complex FFT reversing
Hello,
I've succeeded to compute complex FFT of a data array of interleaved values using the arm_cfft_f32() API, and got in the same array the FFT results as frequency domain values with the same interleaving.
I chose some result values based on a specific criteria, and want to go back to the initial index before calculating the FFT and passing through arm_cfft_radix8by4_f32() API.
Is there anyway to go in the opposite sens, and identify a point based on its FFT result value ?
Thanks and regards, tinymanta.
1 Answer
5 years, 9 months ago.
Hi Tinymanta,
We think you might be confused about what the FFT is doing! It's used to convert a time-series sequence to the frequency domain. There is no direct correlation between any single data point in the time domain with the discrete output samples of the FFT. All input samples are required to generate the FFT output.
Perhaps you are getting tripped up with the terminology. It's possible to return to the time domain by performing an inverse FFT. However, that too requires all FFT output samples to recreate the input.
To summarize, you can't cherry-pick certain samples in the time domain and associate them with a specific frequency (or vice-versa).
-Ralph, Team Mbed