Hi Guys,

I hope someone can help,

I am trying to perform an FFT on 2 seperate signals

the first signal is a Sin(w_o*t) (with a dt=9.7656e-005)

the second is cos(wt)

when I perform the trasnform the phase of these come out a little
strange.

say if i use a block size of 512.
then the cos term phase in the frequency domain gives a perfect 180
degree phase change over the the natural frequency (w_o).

and when i look a the phase of the sin term it has a large positive
gradient with a 180 phase change at w_o.

What causes this large gradient?

Also an interesting thing is for every block size i look at above
512 (ie 1024, 2048 etc) the cosine term's phase has this perfect
change of 180, and the sine term has this large gradient.

however if i look at lower block sizes (256, 128) etc the sine term'
phase is now perfect and the cosine term now has the large gradient!

can anyone explain this to me? or give me some references that coudl
help explain this?

thanks

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