ADMITTANCE OF A LONGITUDINAL WAVE-GUIDE SLOT RADIATING INTO AN ARBITRARY CYLINDRICAL STRUCTURE

In this paper we use a hybrid method to calculate the admittance of a longitudinal slot (of finite length) in a rectangular waveguide, when the slot radiates into a cylindrical outer structure of arbitrary fini te cross section. The analysis takes advantage of a Fourier transforma tion along the cylinder axis, by which the computational effort is dra stically reduced. The harmonic spectral currents on the structure are expanded in subsectional triangular basis functions and determined usi ng an electric field integral equation (EPIE) and the moment method. T hese currents and the corresponding fields are inverse Fourier transfo rmed and matched over the slot to the fields inside the waveguide by a n additional moment method approach using entire domain basis function s for the slot field. The calculated slot admittance has good accuracy when compared with measurements on a chosen geometry.