Analysis and Synthesis of Rotman Lenses

Rotman lenses are attractive candidates for use in beam forming networks (BFNs) for satellitebased direct radiating arrays. This paper will review the basic design equations for a Rotman lens and will describe Rotman lens synthesis and analysis software developed by the author. The synthesis tool, named RLDESIGN, is written in MATLAB to automatically and rapidly solve the Rotman lens equations and interactively display the resulting lens geometry and performance parameters. It features a full graphical user interface customized to easily design, tune, and optimize a Rotman lens for a given application. The more rigorous analysis tool, named NARL (Numerical Analysis of Rotman Lens), is written in MATLAB and Fortran 95 and is based on a boundary integral/surface integral hybrid formulation. NARL uses a unique wide-band expansion of the parallel plate Green’s function to enable rapid analysis of the lens for a large number of frequencies. To demonstrate the accuracy of the codes, comparisons are presented of the predictions of both RLDESIGN and NARL to measurements on a prototype Rotman lens.