The Excitation of Surface Waveguides and Radiating Slots by Strip-Circuit Transmission Lines

A variety of methods for coupling between a shielded strip-circuit transmission line, operating in the TEM coaxial mode, and a surface waveguide have been investigated. The arrangements include phased dipole arrays, series ground-plane slots and Iongitudinal slot excited probes. Impedance and matching conditions for each are discussed together with their relative efficiency and bandwidth. In the case of a single radiating slot, measurements on the effective equivalent circuit have been made as a function of the orientation angle of the slot with respect to the axis of the strip-line guide. Slots used ranged in length from 0.3 to 0.6 lambda_g, having length/width ratios from 5 to 16.