Study On Measurement Method Of Electromagnetic Parameters For Double Negative Medium

The measurement method of electromagnetic parameters of the media are compared in this paper and the in common use measurement method of the electromagnetic parameters of the double negative medium(DNG) are discussed. The effect of the polarization of the incident wave and the effect of the asymmetry of the structure on the parameters are studied by using finite difference time domain (FDTD) method.Firstly, the various measurement methods of electromagnetic parameters are introduced in detail. The principle of all kinds of measurement methods are discussed, and the advantages and disadvantages of each method are compared.Secondly, the measurement methods of anisotropic media and the special structure DNG are discussed in detail. The NRW(Nicolson-Ross-Weir) formulas for reconstruction the constitutive parameters in free space of dielectric medium are deduced based on the inversion formula of waveguide. The unlimited periodic model of DNG in free space are obtained by using the periods boundary conditions and the double-ring resonators model. The S parameters are calculated by the period FDTD method, and the relative permittivity and relative permeability of the period DNG are obtained by using the S parameters and the NRW method.Thirdly, the anisotropic characteristics of the DNG are studied. The effective parameters of the period double-ring resonators model are reconstructed when the electromagnetic incident perpendicular to the interface of the media and with different polarization angle. The influence of measurement result when the incident polarization angles are changed is discussed. The numerical results indicate that the simple double-ring resonators can be the multi-band left-handed material.At last, considering an more practical structures, take the DNG as a non-uniform structure or a partition uniform structure. The symmetric and asymmetric of the periodic structure and the influence on equivalent electromagnetic parameters are studied. The numerical results show that the effective permittivity and permeability of the resonant frequency coincides with each other through adjusting the structural parameters of the model.