A new aperture admittance model for open-ended waveguides

A novel model for the aperture admittance of open-ended waveguide structures radiating into a homogeneous, lossy dielectric is presented. The model is based on the physical and mathematical properties of the driving point admittance of passive, stable one-port networks. The model parameters, which depend on the geometry of the waveguide and aperture, are determined from a relatively small number of computed admittances. These computed data are obtained by a full-wave moment method solution and, hence, include the effects of radiation and energy storage in the near-field and the evanescent waveguide modes. The accuracy of the model, for both the direct and the inverse problem, is verified. The proposed model has important applications in the field of dielectric spectroscopy.<>