Re: [Discuss-gnuradio] Frequency resolution of CORDIC algorithm

[Trond Danielsen]

2007/6/28, Brian Padalino <address@hidden>:
> On 6/28/07, Trond Danielsen <address@hidden> wrote:
> > Hi,
> >
> > after having read several papers on the subject, I am still not able
> > to find the answer I am looking for. I wonder how to calculate the
> > frequency resolution of the CORDIC algorithm. In an earlier post to
> > this mailing list it was stated that the resolution is approximately
> > 0.01 Hz. Could anyone point me to where I can find a deviation of this
> > result?
>
> This paper is really good for understanding the CORDIC:
>     http://web.njit.edu/~hkj2/CORDIC.pdf
>
> It is specifically written to look at FPGA implementations, which is nice.
>
> As I understand it, the USRP uses the CORDIC as described in section
> 3.1 of that paper.  A phase accumulator is used to spin the angle
> around, and the modulated sin/cos or xi is the output on xo and yo
> after 12 iterations of the algorithm.  The value of zo should be zero,
> and any error leftover should be represented on that output.
>
> The resolution should really be how slowly you can spin the zi
> component while maintaining accuracy out of the CORDIC.  It may be
> that with 12 iterations and 16-bit inputs 0.01 Hz is possible, whereas
> more iterations or larger inputs might get better resolution, but I
> suspect you're really past the point of diminishing returns at that
> point.
>
> Is that helpful?

Thank you a lot for your reply. I have already read the mentioned
paper, and found it useful.

Regards,
--
Trond Danielsen