An inverse scattering solution for dielectric constant of a cylindrical post in a waveguide

An inversion algorithm for the computation of the dielectric constant of a uniform cylindrical object in a rectangular waveguide is presented. Analysis of this problem is motivated by the need for an accurate method to measure the complex dielectric constant of pine needles at microwave frequencies both in situ and in vivo conditions. The inversion technique is based on the method of moments and eigenanalysis which requires the reflection coefficient as input. The objective is to measure the reflection coefficient from a cylinder with known cross section in a rectangular waveguide supporting a TE/sub 10/ mode and then calculate its dielectric constant. Practical aspects of dielectric measurement using this technique is discussed. An HP-8510 network analyzer is used to measure the reflection coefficient of dielectric posts in an X-band waveguide sample-holder.