Re: [Discuss-gnuradio] AGC loop

[Bob McGwier]

Eric Blossom wrote:

> On Tue, Sep 19, 2006 at 01:36:55PM -0400, Robert W McGwier wrote:
>  
>
> > Tom:
> >
> > A good agc has at least two time constants.  One for attack and one for 
> > decay.  Your attack is much too slow.
> >
> > tmp = (reference - sqrt(real(y)^2 + imag(y)^2));
> > rate = rate1;
> > if   tmp > gain    rate = rate2;
> >
> > gain += tmp*rate;
> >    
>
>
> Shouldn't this read:
>
>  
>
> > if   tmp > reference    rate = rate2;
> >    
>             ^^^^^^^^
>
>  

I don't think so.   If your noisy  current observation, tmp,  which is 
an instantaneous measurement on the needed gain to attain reference,  is 
below the current smoothed state,  gain,  then you are in decay mode.  
If your instantaneous needed gain observation is less than the current 
smoothed gain,  you are in the attack condition and a different time 
constant on the smoothing is needed.  I am pretty sure what I told him 
is right.  Does it make more sense now?

Bob

--
Robert W. McGwier, Ph.D.
Center for Communications Research
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