Determine whether filter is SOS form
By default, fdesign and design return SOS filters when possible. This example designs a lowpass SOS filter that uses fixed-point arithmetic.
d=fdesign.lowpass('n,fp,ap,ast',40,0.55,0.1,60); hd=design(d,'ellip'); hd.arithmetic='fixed'; IsSOS=issos(hd);
The fixed-point filter hd is in second-order section form, as is the double-precision version.