Moment method calculation of the propagation constant for leaky-wave modes in slotted rectangular waveguide

Abstract

A moment method analysis procedure is described to determine the aperture field distribution in a finite-length straight longitudinal slot cut in the broad wall of a rectangular waveguide. The waveguide is fed from one end with the dominant waveguide mode, while the other end of the waveguide is shorted, exactly at the far end of the slot. From the aperture distribution the far-field radiation pattern is then computed, and from the radiation pattern the attenuation and phase constants of the leaky-wave mode in the waveguide are determined. The method of determining the propagation constant from the radiation pattern is an often used experimental technique to determine leaky-wave propagation constants. Computed data is compared to measured data, and good correspondence observed. This propagation constant data can be used to design long meandering leaky-wave slot antennas.