Rotman Lens Amplitude, Phase, and Pattern Evaluations by Measurements and Full Wave Simulations

Abstract

Microwave lens’ performance is depicted by several parameters such as phase error, amplitude taper, and array scan pattern etc. For decades, these parameters have been estimated by the geometry optics method that does not capture the mutual couplings within the lens geometry. Full wave simulation toolkits to conduct EM prediction are now available. However, using them to synthesize and optimize the electrical performance of Rotman lens is still relatively new. Several microwave lens full wave simulations have been attempted using different methods, such as FDTD, FEM, and FIT. They were reported from the perspectives of either phase or amplitude predictions at a single port or single frequency. However, the lens properties at multiple frequencies and for multiple beam ports using MoM have not been investigated. In this paper, we address such simulations using the planar Green’s function in FEKO. The phase, amplitude and array factor across the frequency band for multiple beam ports are compared with the measured results, and their errors are evaluated. Prominent agreement between FEKO and measurement is demonstrated. The performance of a prototype lens is presented, followed by discussing few future aspects of lens optimization using full wave simulations.