[fit,errdb] = rationalfit(s,i,j)使用rationalfitfunction to construct afit, anrfmodel.rationalobject fitting only the (i,j)th element of the S-parameter objects. This syntax is equivalent torationalfit(s.Frequencies,rfparam(s,i,j),...).

[fit,errdb] = rationalfit(s)使用rationalfitfunction to construct afit, anN-by-Nofrfmodel.rationalobjects (sharing identical poles) fitting all theN-by-Nelements of the S-parameter objects. You can directly pass thisN-by-Nfittofreqresp,ispassive,passivityfunctions. This syntax is equivalent torationalfit(s.Frequencies,S.Parameters).