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C28X FPU FFT Library Phase Response

Cem Koose
Intellectual 880 points

Hi,

I examined the fft library and examples for f28377x. "2837x_RFFT_Unaligned_ScaledMagnitude" and "2837x_WindowedRFFT" examples.

Both examples uses same input data. I understand that the magnitude outputs have different peak values because first example normalizes the data. But what about the phase output. Why are they look like so different? I plotted the input, magnitude and phase data to a excel file using "data_input.h", "data_output_1.h",  "data_output_2.h", "data_output_3.h" which are given in the example folder.Excel files are attached.

How can we interpret the result?

Regards,

FFT Excel.rar

  • Intellectual 880 points
    I tested the software and understand the phase output. For example RFFTmagBuff[6] gives 3rd harmonic magnitude and RFFTphaseBuff[6] gives respective phase. I think other phase output values in the RFFTphaseBuff[] are irrelevant.