frfit

frequency response fit

Calling Sequence

sys=frfit(w,fresp,order)
[num,den]=frfit(w,fresp,order)
sys=frfit(w,fresp,order,weight)
[num,den]=frfit(w,fresp,order,weight)

Arguments

:w positive real vector of frequencies (Hz) : :fresp complex vector of frequency responses (same size as w) : :order integer (required order, degree of den) : :weight positive real vector (default value ones(w)). : :num,den stable polynomials :

Description

sys=frfit(w,fresp,order,weight) returns a bi-stable transfer function G(s)=sys=num/den, of of given order such that its frequency response G(w(i)) matches fresp(i), i.e. freq(num,den,%i*w) should be close to fresp. weight(i) is the weight given to w(i).

Examples

w=0.01:0.01:2;s=`poly`_(0,'s');
G=`syslin`_('c',2*(s^2+0.1*s+2), (s^2+s+1)*(s^2+0.3*s+1));
fresp=`repfreq`_(G,w);
Gid=frfit(w,fresp,4);
frespfit=`repfreq`_(Gid,w);
`bode`_(w,[fresp;frespfit])

See Also

• frep2tf transfer function realization from frequency response
• factors numeric real factorization
• cepstrum cepstrum calculation
• mrfit frequency response fit
• freq frequency response
• calfrq frequency response discretization