A negative-index annular lens device for feeding 360°-steerable ring arrays

This paper describes the design of a negative-index annular lens device intended for use as the core element of the beam-forming network in circular ring electronically-steerable arrays (ESA). Circular ring ESA's offer the benefit of full 3600 scan coverage, and hence are ideal for application in mobile and portable communication devices. The proposed lens device can be used as an interface between the front-end electronic and the antenna elements, as depicted in Fig. 1. The lens has an annular geometry. The antenna ports are defined along the outer rim and electronic (or beam) ports lie on the inner rim of the device. The lens is made of inhomogeneous material, where the refractive index varies with radius. Antenna ports can be extended using equal lengths of transmission line to feed an array with a radius greater than that of the lens.