Admittance of rectangular apertures

The paper presents investigation on admittance characteristics of rectangular aperture excited from rectangular waveguides. Complex radiated power is determined from the angular spectrum of plane waves. The aperture admittance is obtained on dividing the complex radiated power by the square of the input reference voltage, which is the dominant mode voltage of a waveguide having the same dimensions as the aperture. Computed results for apertures of different lengths and widths, excited from X-band rectangular waveguide have been presented graphically. The admittance presented to the feed waveguide for inductive window type aperture has also been found.