[Discuss-gnuradio] Numerical stability and accuracy of PLL blocks

[Daniele Nicolodi]

Hello,

does anyone know if any stability and accuracy evaluation of the digital
PLL as implemented in GNU Radio exist?

I'm trying to measure the frequency of a very low phase-noise signal and
I see strange artifacts for certain combinations of detuning (residual
frequency difference between the signal and the N210 center frequency)
and PLL bandwidth.

I already have re-implemented the PLL blocks to measure phase using a
more accurate arctan2() function than the one provided by Volk (which
uses a linear approximation for small angles) but I still see strange
things that I believe are due to the control loop going nuts due to
numerical problems.

If some work has already been done in this regard I could probably save
some time.

Thanks. Cheers,
Daniele