Re: [Discuss-gnuradio] Frequency Xlating FIR filter: bug in gr_rotator

[Matt Ettus]

Quoting Sérgio Rui Silva <address@hidden>:

> I have been using the "GrFreqXlatingFIRfilterSCF" and I notice
> that its output slowly increases in amplitude (or diminishes,
> depending on the frequency setting). I found that this is due to
> the "gr_rotator" class. If the absolute value of the
> "gr_rotator"s "phase"
> variable is printed during the processing cycle one can see that
> its value starts with 1.0, as it should, and then augments
> slowly. I think this is because the recursive multiplication
> used causes a precision error to increase in one direction.

Yes, that's exactly what is happening.


> I solved this by
> not using the gr_rotator class but the gr_nco class instead.
> This solution is not as elegant as the one with the gr_rotator
> class, but it does the trick by now... Any ideas one how to
> solve this correclty?


That's exactly how to solve the problem.  I thought I had alread made that
change, but apparently, I had only done that in the FPLL class.  If you send me
a patch, I'll integrate it.

Thanks
Matt