Input impedance of slots printed between two dielectric media and fed by a small /spl Delta/-gap

We present a quasi-analytical formulation for the input impedance of a slot antenna printed between two dielectric media and fed by a /spl Delta/-gap which is very small in terms of a wavelength. The work is oriented to the analysis of hot electron bolometers used as sensors for sub-millimeter wave slot antennas. In such structures, the geometrical details are very small in terms of the wavelength, thus implying ill-conditioning problems in a conventional method of moments analysis. The present formulation is based on the Green's function of a slot printed between two homogeneous dielectrics, presented in our previous works. A suitable asymptotic function is extracted from the spectral domain expression of the input impedance in such a way that the re-added contribution leads to an analytical form. The regularized remainder after the extraction is efficiently calculated by a spectral numerical integration. Finally, the procedure is generalized to /spl Delta/-gap feeding in more complicated slot-circuit geometries.