Re: [Discuss-gnuradio] Costas Loop not Locking (Solved)

[Eric Blossom]

On Fri, May 22, 2009 at 09:42:00AM -0400, Tom Lutz wrote:
> I was having a very difficult time trying to get a Costas Loop to work
> yesterday for order=2.  I discovered, by the end of the day, several
> things:
> 
> 1. Min and Max frequency are in Radians per Sample (the documentation
> says 'normalized', but I wasn't sure whether it meant cycles/sample or
> radians/sample)

Fixed in the .h file.  Not yet committed.

> 2. The loop likes a signal that lies on the unit circle (i.e.
> magnitude=1).  I was using unscaled data that ranged from -150 to
> 150....not so good!  I used Automatic Gain Control to fix this.
> 
> I used a nominal value of 0.01 for alpha and alpha^2/4 for beta, but I
> suppose you should tweak these by testing the response of the loop for
> various stimuli.
> 
> I think I'll update the documentation to make things more explicit.
> 
> Cheers,
> Tom