Extrapolated Virtual Antenna Array for Enhancement of Resolution of Uniform Linear Array

Abstract

In this paper, we propose a design of the multibeam antenna for cellular base stations operating in frequency band 1.7–2.2GHz. The antenna consists of a uniform linear array of 12 slot elements with rectangular directors and modification of Rotman lens used as beamforming network. Rotman lens was folded in half to reduce its dimensions: the ground plane was placed in the center of the lens; the halves of the lens body and exponential strip transformers were placed on both sides of the ground plane. To reduce the sidelobe level in receiving mode, we formed additional virtual antenna elements by array interpolation and extrapolation. Moreover, number of virtual antenna elements can exceed number of “real” antenna elements while its physical size stay the same. This property is especially useful in case of limited installation space. In addition, extrapolated antenna array can be used to increase the directivity of a receiving antenna system and resolve radio sources which are not resolvable by “real” antenna array.