LINEAR-PHASE ARRAYS BASED ON SLITTED ASYMMETRIC RIDGE WAVE-GUIDES

The analysis of linear phase arrays based on the slitted asymmetric ridge waveguide: a structure that is, at the same time, easy to manufacture and very flexible in terms of electrical characteristics is presented. Scanning is obtained in leaky-wave fashion (frequency scan) in elevation (longitudinal plane), and by phase shifters in azimuth (cross-plane). The analysis is based on the development of an accurate transverse equivalent network and on the derivation of a dispersion relation which gives the complex longitudinal propagation constant in terms of the structural parameters. Both cases of air-filled and dielectric-loaded ridge waveguide are studied. The effects of mutual coupling between the various line sources of the array are taken into account using the unit-cell approach. A detailed parametric analysis is carried out showing how the real and imaginary parts of the complex propagation constant, which are related to the radiation characteristics, can be controlled with a good degree of independence from each other. Moreover, no blind sports are introduced in the scanning process, while the grating lobes are avoided, due to the choice of the cross-section. This approach has been applied to two other linear phased arrays of leaky-wave line sources, based on an asymmetric NRD guide and on a printed-circuit version of an offset groove guide.