Re: [Discuss-gnuradio] AGC loop

[Robert McGwier]

Bob McGwier wrote:
> 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

Arrrgh.  If the instantaneous needed gain ERROR estimate, tmp,  is 
positive,  you are in decay.
If the instaneous needed gain ERROR estimate, tmp, is negative,  you are 
in attack.

I believe the equations are right even if I cannot answer an email clearly.

;-)
Bob



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