hi raul,
plan ahead shouldn't change dynamic range.
some of the things that change dynamic range are:
1) shift parameters
(down shift every stage gives poor dynamic range,
but is robust - never overflows.
down shift every other stage gives excellent
dynamic range, but can result in overflow.
2) rounding enabled in the FFT yields improved dynamic range.
3) the number of bits in the FFT
4) the length of the FFT.
best wishes,
dan
On Tue, Sep 16, 2014 at 7:21 AM, Raul Sapunar Opazo <[email protected]>
wrote:
> Hello everyone,
>
> I used planahead to fix the timing problems of a 1.8Ghz 32k channel
> spectrometer in roach 2. I did it without troubles, using 38% of the DSP
> and less of the 50% of RAMs..
>
> After I compiled the model with the new constrains/placement and I tested
> the bof, I found out that the numeric noise increased a lot as the power of
> the harmonics...
>
> This issue results in a big decrease of the dinamic range of the
> spectrometer in the whole BW (around 25 db against 40-45 db of a 1.8Ghz 16
> k ch spectrometer that didn't need planahead)
>
> I encountered this problem with an 1.8GHz 8k ch aswell.. so the issue is
> not related with the increase of the number of channels..
>
> Anyone encountered this kind of problems when using Planahead? As I
> understand planahead shouldn't change the performance because it doesn't
> make any change in the designs...
>
> Any help will be appreciated!
>
> Best Regards,
> Raul Sapunar
>
