Re: [Discuss-gnuradio] MRFM (Magnetic Resonance Force Microsocopy)andGNU Radio

[Jeff Brower]

Jon-

> > I'm curious .. what do use the 'biquad filters' for?  I assume you mean 
> > that you've
> > implemented a 4th order IIR filter?  If so that would mean somewhat 
> > non-linear phase
> > depending on the IIR design type.  What type are you using?  Elliptic?  
> > Other?
> 
> The pair of cascaded biquadratic filters form an optimal cantilever 
> controller.
>  Our experiment software calculates the controller transfer function, a ratio
> of polynomials with four numerator and four denominator coeffcients (floating
> point), using the methods described in the papers linked to our page at
> "Cantilever controller design is discussed _here_ ..."
> Our software refactors and scales that transfer function into two biquad 
> filter
> stages with 24-bit integer coefficients.   So I guess the filter type is
> "other".   Some phase compensation is included in the transfer function,
> as described in the papers.

Ok thanks.  A fascinating use of the USRP hardware.

-Jeff