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How to find the exact frequency and amplitude from Fourier?
The frequency resolution is 2 Hz and there is no point at the harmonic frequency of 17.2 Hz. Clearly the frequency is bracketed between the 9 th and 10 th point (16 Hz and 18 Hz). How do we find the exact frequency and amplitude?
What is the rule for the Fourier transform?
The rule is simple: period=N/index. That is, a sinusoid like produces spikes in the Fourier spectrum at N/period and N-N/period. The first spike is at a positive frequency and the second is at a negative frequency.
How is the Fourier transform used in IDL?
One of the most important uses of the Fourier transform is to find the amplitude and phase of a sinusoidal signal buried in noise. For example, run the following commands in IDL: You can see that it is difficult to distinguish the sine wave from the noise.
When does the imaginary part of a Fourier transform vanish?
This is a Fourier sine transform. Thus the imaginary part vanishes only if the function has nosine components which happens if and only if the function is even. For an odd function, theFourier transform is purely imaginary. For a general real function, the Fourier transform willhave both real and imaginary parts. We can write
Why do I get different signal after FFT?
I’m trying to rebuild a signal from the frequency, amplitude, and phase obtained after I do an fft of a signal, but when I try and combine the fft data (frequency, amplitude, and phase) back to see if I get a similar signal, the pattern is a little off. I think it has to do with my formula which may be a little incorrect.
How to reconstruct a signal from its discrete Fourier transform?
I would like to slightly modify the above figure such that all of the lines shown are overlaid on a single plot. I have been trying to adapt the figure with some real data sampled at 60 Hz.
How is each point in a FFT a complex number?
So each point in an FFT is a complex number that contains information about the phase and amplitude at that frequency. You’re extracting this information with these lines: You’re getting the magnitude and phase of each complex number, converting from rectangular complex number to polar form.