Scaling and focusing of the Rotman lens

Abstract

With a high dielectric material, the size of the Rotman lens (see Rotman, W. and Turner, R.F., 1963) can be reduced by a factor of /spl radic/(/spl epsiv//sub r/). Its design equations and scaling factor can be modified and defined according to the dimensions and materials of the lens and lines. Combining the lens with phase shifters, the lens and antenna array can generate multiple focused beams with a relatively small spot size. In wireless communications, the lens can allow us to increase the channel capacity by adding space division multiplexing and increasing the signal-to-interference ratio, S/I. Focusing the beam adds to both the angular and radial resolution. For application in ground-penetrating radar, a Rotman lens reduces the burden on signal processing as well as its size and weight. Using a ferroelectric material such as BaSrTiO/sub 3/, we can fabricate the lens and voltage-tunable delay lines (phase shifters) in thin film geometry by laser ablation.