Compact colinear end-launcher for rectangular waveguides

A novel structure for launching the fundamental mode in rectangular waveguides is proposed. The geometry consists of a cavity-backed circular patch radiating into a rectangular waveguide. The matching properties of the proposed component are comparable with the ones of the classically used L-shaped loop end-launcher. The structure results in a very compact, colinear transition from a standard coaxial connector to a rectangular waveguide. The component has applications as general purpose coaxial-to-waveguide transition and is well suited for low-profile phased-array antennas.