Rectangular aperture radiating into a lossy medium-numerical and experimental results

The authors present three numerical techniques: the finite element method, the method of moments (MOM) and the mode-matching method. These methods were used to determine the input impedance of a rectangular aperture excited by a rectangular waveguide and radiating into a lossy medium. The numerical techniques were applied to several aperture geometries, such as capacitive and inductive slots, in contact with known dielectrics (water and methanol). The calculations were performed over the frequency range 8.5-11.5 GHz (X-band). The numerical results were validated by measurements performed with an automated network analyzer. Typical results are presented which show the dominant mode reflection coefficient in the plane of the aperture for the case of an open-ended guide (full aperture) in contact with water. The CPU usage of the numerical methods is given.<>