Amplitude performance of Ruze and Rotman lenses

Abstract

Ruze and Rotman lenses are devices which can be used to form multiple beams for antenna arrays. A previous paper has shown these lenses can be designed for low-phase aberrations and minimum size. Published work on these lenses has concentrated on phase and largely neglected amplitude performance (except Maybell). Here, a theoretical model is developed which predicts the primary amplitude distribution across the array ports of the lens; this then allows predictions of insertion loss and sidelobe levels of the fed array. An experimental waveguide-fed parallel-plate lens has constructed, and amplitude and phase performance measured. Comparison with the theoretical predictions shows good agreement. The multiple beam radiation patterns produced by a 16-element array fed by this lens have also been measured. The lens has a low insertion loss (?2 dB) and provides a low sidelobe level (?20 dB) for the 8?12 GHz band.