Theory and Measurements of a Compact High Dielectric Microstrip Rotman Lens

A compact microstrip lens operating at frequencies between 1.33 and 4 GHz was designed and tested. The measurements included the complete scattering matrix as well as the multibeam radiation patterns. In addition, a contour integral equation formulation was developed to predict the S-matrix associated with the lens. The model incorporates higher order propagation modes as well as the tapered transitions that transform the 50 Ω transmission lines to the larger lens apertures. This paper discusses problems associated with the lens design and manufacture of the tapered transitions, describes the lens model, compares measured S-parameters with theoretical predictions, and presents the resultant radiation patterns with the lens connected to an array of wideband, notched, stripline antenna elements.