Main Archive Specials Wiki | FAQ Links Submit Forum

 Frequency response from biquad coefficientsType : biquadReferences : Posted by peter[AT]sonicreef[DOT]comNotes : Here is a formula for plotting the frequency response of a biquad filter. Depending on the coefficients that you have, you might have to use negative values for the b- coefficients. Code : //w = frequency (0 < w < PI) //square(x) = x*x y = 20*log((sqrt(square(a0*square(cos(w))-a0*square(sin(w))+a1*cos(w)+a2)+square(2*a0*cos(w)*sin(w)+a1*(sin(w))))/ sqrt(square(square(cos(w))- square(sin(w))+b1*cos(w)+b2)+square(2* cos(w)*sin(w)+b1*(sin(w))))));

 CommentsAdded on : 20/12/04 by SergeyComment : There is a better formula of a higher order by George Yohng available on this siteAdded on : 16/03/06 by dfl[ AT ]ccrma[ DOT ]stanford[ DOT ]eduComment : this formula can have roundoff errors with frequencies close to zero... (especially a problem with high samplerate filters) here is a better formula: from RBJ @ http://groups.google.com/group/comp.dsp/browse_frm/thread/8c0fa8d396aeb444/a1bc5b63ac56b686 20*log10[|H(e^jw)|] = 10*log10[ (b0+b1+b2)^2 - 4*(b0*b1 + 4*b0*b2 + b1*b2)*phi + 16*b0*b2*phi^2 ] -10*log10[ (a0+a1+a2)^2 - 4*(a0*a1 + 4*a0*a2 + a1*a2)*phi + 16*a0*a2*phi^2 ] where phi = sin^2(w/2)

 Add your own comment Comments are displayed in fixed width, no HTML code allowed! Email: Comment: Are you human?

Site created and maintained by Bram
Graphic design by line.out | Server sponsered by fxpansion