Aperture performance of a double-ridge rectangular waveguide in a phased array

Despite its widely recognized broad-band characteristics, the potential of a double-ridge rectangular waveguide as a phased array element has not been systematically explored. An additional benefit in using this waveguide is its reduced size which permits realization of a compact array lattice for wide angle scanning applications. A number of treatments of ridge waveguide propagation characteristics appear in the literature [1] -[5], but an analysis of the performance of a double-ridge waveguide phased array element has only recently been published [6], [7]. The results presented are based on [6], but they include additional material. The unmatched aperture performance of a rectangular ridge-guide in a number of wide-band phased arrays with quarter-hemispherical coverage, and a single narrow-band -plane scan design are examined. A parametric study and comparison of the unmatched aperture performance of a ridged-guide element with that of a rectangular waveguide reflects the capabilities of the double ridged-guide wide-band element in a large phased array. Such parametric study reveals to the designer the active admittance of the unmatched radiating element and leads in a systematic manner to a choice of the ridge-guide geometry and array lattice, to be followed by the determination of a suitable matching structure. This approach contrasts that of [7], which concentrates on demonstrating the feasibility of broad-band matching of a particular dual ridged-element.