COMPLEX PERMITTIVITY EXTRACTION OF DIELECTRIC SAMPLES IN WAVEGUIDE

摘要

This paper describes a method to determine the relative permittivity of a dielectric material in Printed Circuit Board.The dielectric sample in a PCB is placed to formA finline discontinuity of finite length Ina waveguide. S-parameter of a discontiuity from an empty waveguide to finline and back to empty waveguide is measured. An errorfunction that compares the measured and calculated S-parameters of the discontinuity is minimized to extract the permittivity of the sample. The optimization is based onA practical Quasi-newton algoritm. The calculated value of the S-parameter used in the error function is obtained from the modal expansion of the fieldsInthe empty waveguide and the finline structure. Field matching is done at the disconitinuity to yield the theoretically calculated S-paramters.