Re: [Discuss-gnuradio] Basic IIR Filtering

[Robert Roberts]

Hi Matt.


Thanks for your help.   I restored Internet access to my Linux box and
was able to transfer the actual filter weights from MATLAB into GNURadio
and it worked. The roundoff error must have been causing the IIR filter
to go unstable.


Thanks,
~Chris~

----- Original Message -----
From: Matt Ettus <address@hidden>
Date: Tuesday, June 13, 2006 1:29 pm
Subject: Re: [Discuss-gnuradio] Basic IIR Filtering
> 
> >I am finding that if I use a tap vector length of greater than 4 the
> >code stops working. Instead of a tone I get no noise.
> >  
> >
> You may be getting instabilities, which is common with high order 
> IIR 
> filters.  However, Just to make sure the problem isn't the code, 
> try 
> making a 2 tap filter and instantiate it as a 4 tap, setting the 
> other 
> taps to 0 or 1 as appropriate. 
> 
> If you find that instability is the problem, you are better off 
> breaking 
> your filter into cascaded biquad sections.  Matlab should be able 
> to do 
> that for you.
> 
> Matt
>