An Accuracy-Enhanced Vector Fitting Technique and Its Applications to Model Electromagnetic Parameters

An accuracy-enhanced vector fitting (VF) technique is proposed in this letter to fit electromagnetic parameters, which do not require conjugate symmetric complex terms. Based on the original VF technique, a gain coefficient is introduced by each term in the pole-residue model and solved using the system equation constructed from measured data. Then, these coefficients are incorporated into the residual and constant of the corresponding term in the existing pole-residue model. In addition, four adaptive order selection schemes for engineering applications are discussed and given. Two numerical examples, including complex refractive index and relative permittivity of metals, and the surface conductivity of mulilayer graphene, demonstrate the improvement on the fitting accuracy of the proposed technique.