Broadband monolithic constrained lens design.

Abstract

Constrained lens geometries have attracted attention as a replacement for bulky mechanical beam-steering systems or complex and expensive electronically beam scanned systems. Despite the great potential of constrained lenses, poor matching techniques and port implementation have limited the performance of Rotman lenses. This thesis provides a thorough engineering methodology for designing and analysing Rotman lenses. This has been achieved by reworking the Rotman equations for the intended application of a linear antenna array feed network. Further, a number of statistical methods are presented to evaluate the performance of the Rotman lens, providing a set of tools to optimise the lens for any linear array specification. While mathematical analysis of the Rotman lens using geometrical optics has occupied much of the work in the literature, the real challenges of constrained lens design have been only briefy reported. These challenges include the design of port geometries, feed networks, and impedance matching, which are particularly significant due to the desire to exploit the broadband potential of constrained lenses. The electromagnetic limitations of the Rotman lens architecture are presented with the analysis and fabrication of a 5 to 20 GHz Rotman lens design. In doing so, the mechanisms that limit lens performance are highlighted. This thesis presents a clear path through the minefield of design transforms to a Rotman lens that transforms its broadband potential to reality.