An efficient volume integral-equation approach for characterization of lossy dielectric materials

An efficient volume integral-equation approach for characterizing lossy dielectric materials in the Courtney holder type of measurement environment is proposed. Utilizing the parallel-plate dyadic Green´s functions and the volume equivalence theorem, an effective electric-field integral equation is developed for azimuthally invariant mode analysis of a parallel-plate dielectric resonator. Volumetric cylindrical pulse basis functions and a point-matching moment-method procedure are used to formulate an eigenvalue problem. A novel singularity treatment, which uses a Bessel function identity, is presented. In an iterative permittivity searching process, perturbation of the eigenmatrix equation involves solely recomputing a diagonal matrix, which is a function of permittivity only. Therefore, the efficiency of the searching process is greatly increased. Two numerical examples are provided to illustrate the applicability and validity of the proposed approach to the evaluation of dielectric constant, loss tangent, and surface resistance of the parallel plates.