Cylindrical Waveguide Slot Antenna Analysis
Waveguide slot antennas with longitudinal and transverse slots are analyzed using a rigorous method. The antennas are divided into regions, which are analyzed separately and matched by a moment method procedure. At the apertures between the regions, the electric fields are expanded in trigonometric basis functions. These apertures appear at the inside and outside of the slots in order to take the waveguide wall thickness into account.
The shape of the exterior structure of the slot antenna is assumed to be a cylinder with arbitrary cross section. The exterior fields and currents are Fourier transformed along the structure. An integral equation is set up and solved in the spectral domain, i.e. where the time and longitudinal coordinates have been transformed. Its solution is found numerically with the moment method, since general cylindrical structures are treated. The induced electric currents on the structure are expanded in subsectional basis functions formed as triangles and pulses. The spectral magnetic field and the spectral mutual admittances are determined from the computed values of the spectral induced currents. The spectral mutual aperture admittances are inverse transformed and included in the overall slot antenna analysis.