Hello all ! Considering IIR filtering with fixed-point DSP : How to arrange biquads to reduce roundoff or quantization noise ? If anyone has resources, advices or links ! Thank you.
Arranging biquads
Started by ●September 30, 2003
Reply by ●September 30, 20032003-09-30
"Curl" <Mr.Bilou@microsoft.fr> wrote in news:3f79a987$0$28905 $626a54ce@news.free.fr:> Hello all ! > > Considering IIR filtering with fixed-point DSP : > How to arrange biquads to reduce roundoff or quantization noise ? > > If anyone has resources, advices or links ! > > Thank you. >Rule No. 1: Use Direct Form 1, not Direct Form 2. -- Al Clark Danville Signal Processing, Inc. -------------------------------------------------------------------- Purveyors of Fine DSP Hardware and other Cool Stuff Available at http://www.danvillesignal.com
Reply by ●October 1, 20032003-10-01
| Al Clark a ecrit : | Rule No. 1: | Use Direct Form 1, not Direct Form 2. | Rule No. 1 already respected ;o) What is the No.2 ?
Reply by ●October 1, 20032003-10-01
Curl wrote:> Hello all ! > > Considering IIR filtering with fixed-point DSP : > How to arrange biquads to reduce roundoff or quantization noise ? > > If anyone has resources, advices or links ! > > Thank you.Investigate the Mathworks web site. Using their search dialog, ask for 'ss2sos'. The first entry should lead you to the description of this conversion method. It uses 'order' and 'scale'. Following the links should lead you to the principles behind. If you use Matlab, signal processing toolbox is your friend. Bernhard
Reply by ●October 1, 20032003-10-01
If you still have trouble with quanitization with DF1, then you can try some of the lattice/ladder implementations. Is this fixed or floating point? What kind of numerical precision do you have (e.g. 16, 24, 32-bit)? "Curl" <Mr.Bilou@microsoft.fr> wrote in message news:3f7a9a73$0$28876$626a54ce@news.free.fr...> | Al Clark a ecrit : > | Rule No. 1: > | Use Direct Form 1, not Direct Form 2. > | > Rule No. 1 already respected ;o) > > What is the No.2 ? >
Reply by ●October 2, 20032003-10-02
"Curl" <Mr.Bilou@microsoft.fr> a �crit | Rule No. 1 already respected ;o) oops.. Too fast The exact aswer is : I'm using a cascade form of 2nd order Form 1 IIR filter The poles of a biquad are combined whith the zeros of the next biquads. Thank you for your answers, I'm currently looking at SPRA454 (Extended precision IIR filter Design on the TMS320C54x DSP). Since I have 5 biquads, I think i will try different arrangements (may be the 5!) and see the difference with a spectrum analyzer
Reply by ●October 3, 20032003-10-03
Curl wrote:> > Hello all ! > > Considering IIR filtering with fixed-point DSP : > How to arrange biquads to reduce roundoff or quantization noise ? > > If anyone has resources, advices or links !I would recommend a book: Dietrich Schlichtharle. Digital Filters: Basics and Design. Springer ISBN 3-540-66841-1 Basically, the rule is to combine poles with zeroes and move the sections with high Q to the front so the noise of high Q sections will be filtered out by low Q sections. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com