Re: [Discuss-gnuradio] Clock Recovery MM

[Tom Rondeau]

On Mon, Sep 8, 2014 at 5:49 PM, Bastian Bloessl <address@hidden> wrote:

Hi all,

looking at the clock recovery MM code, I wonder if d_omega_relative_limit is a relative or absolute deviation from d_omega.

Here it looks like absolute
https://github.com/gnuradio/gnuradio/blob/next/gr-digital/lib/clock_recovery_mm_ff_impl.cc#L107

Here it is relative
https://github.com/gnuradio/gnuradio/blob/next/gr-digital/lib/clock_recovery_mm_ff_impl.h#L57

(even though this code has no impact since d_{min,max}_omega is not used.)


I don’t have access to the book linked in the docs atm.

Best,
Bastian

It is supposed to be relative. I'd have to verify the math on that line 107 in the .cc file, but it's supposed to adjust the center position of the current omega estimate and then apply the clipping. Then it adds the mid point back to get it back to where it's centered. Try walking through that line one more time to verify that it's doing that properly. But yes, it's supposed to be relative to the original setting of omega.

Tom