Phase Spectrum in Fourier Transform Probably a simple question to answer. I have been trying to use the fft function in MATLAB and have been succesful to get the amplitude spectrum of a known signal. But when working out the phase spectrum I am unsure if its the correct output.
Can anyone explain what the phase spectrum in fft is used for? I have researched other places but have not a satisfactory answer.
If for example I had a pure sine wave what would the phase spectrum show and how will I know if it is correct.
I can give example of my MATLAB code if necessary but if someone can give a basic explanation using MATLAB it will be much appreciated.
I think that the plot you display does not show the correct answer, what makes me think that is that you inject in your fft a pure sinewave with an initial phase equal to 0. Therefore your plot should display a 0 phase shift for every frequency bins.
For exemple, below you can see the phase plot of a pure sine wave with an initial phase shift of 30 degrees.

The phase spectrum will be here to tell you in which way your signals are delayed for each frequency components.