Radiation of Open-Ended Rectangular Waveguide into Terminating Rectangular Cavity: Application to the Measurement of the Complex Dielectric Constant of Substances

The problem of radiation of open-ended rectangular waveguide into a rectangular cavity is tackled. The cavity is assumed to be filled with material of complex dielectric constant in the form of powder or liquid. The cavity is directly connected to the waveguide through its open end. The work main objective is to solve for the electromagnetic fields inside the waveguide and the cavity in order to estimate the value of the equivalent admittance of the cavity in terms of its dimensions, the complex dielectric constant of the substance filling it and the waveguide dimensions. Successful and good agreement is obtained between the obtained results and those obtained by using the commercial software HFSS. Further to that, the work paves the way for an accurate and efficient technique to measure the complex dielectric constant of substances filling the terminating cavity.