Research On Wave Propagation In Complex Dispersive Media Based On WLP-FDTD Method

In this paper,in order to improve the efficiency,stability and general ability of time domain numerical algorithm to simulate wave propagation characteristics in complex dispersive media,based on the modified Lorentz model,we derived an algorithm of WLP(weighted Laguerre polynomials)-FDTD(Finite-Difference Time-Domain)which can cover Debye,Drude,Lorentz,CP(critical point)?CCPR(complex-conjugate pole-residue)? QCPF(quadratic complex rational function),Cole-Cole and any combination of them.It is applied to biological tissue with complex dispersion model to study the electromagnetic properties of electromagnetic wave through biological tissue.This study expands the application range of WLP-FDTD method,and will help to develop new protocols for electromagnetic imaging,tumor diagnosis and target detection.The main research results of this issue are as follows:1.This study expand the scope of Lorentz model and make it have strong general ability.the Cole-Cole model of fractional derivative is transformed into a modified Lorentz model by Padé approximation.The modified Lorentz model can cover any multipolar complex dispersion models such as Debye,Drude,Lorentz,Critical Point,QCRF,CCPR and Cole-Cole and any combination of them.This general dispersion model can be applied to other more efficient FDTD algorithms,which provides a new possibility for other general FDTD algorithms.2.The general modified Lorentz model is applied to the unconditionally stable WLP-FDTD,so that the advantages of the modified Lorentz model can be combined with the advantages of the unconditionally stable WLP-FDTD algorithm,and the application range of WLP-FDTD algorithm is expanded,and the theoretical system of WLP-FDTD is enriched.The methods and steps of the transformation from complex dispersion models such as Debye,Drude,Lorentz,Critical Point,QCRF,CCPR and Cole-Cole to modified Lorentz model are given in detail.3.The unconditionally stable ADE-WLP-FDTD algorithm based on modified Lorentz model is applied to biological tissue with complex dispersion medium model.The transmission characteristics of normal breast tissue and tumor breast tissue at terahertz frequency band were studied.The results showed that transmission coefficients were obviously different under the same conditions.It provides a new numerical method for studying the wave propagation characteristics of biological tissue in terahertz frequency band.At the same time,the microwave wave propagation characteristics of muscle tissue and adipose tissue based on the 4-th Cole-Cole model and CCPR model are discussed,which provides a new solution for the study of wave propagation in biological tissue.