Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
17 years ago

Altera FFT Vs Matlab FFT. Strange Results

Hi, I’m testing some FFT Altera Core using those parameters: 1)Single Streaming or Burst 16K length FFT 2)12-14-16 bits input REAL data (pseudorandom code {-1,1}) 3)same bits for twiddle...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
17 years ago

Two possible errors:

1. You are inputting data to the FFT core when it isn't ready. You should really wait for sink_ready signal to be asserted.

2. You are using a streaming FFT (I can't tell) and that you are not using the full dynamic range for the input. As I explained in the earlier note (from the same threat), you should really use full dynamic range. Otherwise, it is possible that your input would disappear within the core (due to the block floating point -> data is rounded and truncated after each butterfly stage).

Also... attach a bigger picture, so people can see what you're doing...