When splitting higher order recursive filters into more convenient 2nd order sections (biquads), in matlab, we usually use
zp2sos to convert. In document, there's a couple of lines , which I am quoting below,
[sos,g] = zp2sos(z,p,k,''order') specifies the order of the rows in sos, where 'order' is
'down', to order the sections so the first row of sos contains the poles closest to the unit circle
'up', to order the sections so the first row of sos contains the poles farthest from the unit circle (default)
Here i can't remember that I had read something relevant to arranging the biquads on the basis of poles location.
Now Can anyone explain me, why should we arrange the biquads in a specific manner while cascading them ?
What that arrangement is to deal with the poles being closer or farthe from unit circle, as Matlab documents says?
What specifics need to be considered while ordering the biquads to get higher order filters.
It'll be so nice to illustrate by using some case study, for example, designing the A weighting filter (8th order IIR), and converting it ino biquads, and arranging them in a specific manner which is under discussion.
Thanks in advance.