I am taking a 256 point FFT using FFT7.1. I am using a sine wave as input to xn_re via Gateway In block.
I am setting the binary points in gateway In block . I have used (number of bits , binary point) [8,7] [16,15] and [34,33] number of bits in Gateway In to increase the precision.
I have plotted the db plot of output magnitude spectrum and I am not able see much difference as I change the precision.
I have few queries
Is it the right way to set precision?
What precision will be used for internal FFT computation?
Why I am unable to see the effect of precision change?
Mayur D. Jain
Try changing the Twiddle Factor precision.
Also look at how much of the dynamic range you are using. The FFT treats the data as 16.15.