Antenna Beamwidth Control Using Parasitic Subarrays

A new and effective technique of controlling the azimuth pattern of a singly or dually polarized linear antenna array is presented. It is shown that the use of parasitic elements allows us to control the azimuth beamwidth over a wide range. We are motivated by the need for base station antennas for mobile or fixed cellular systems. Such antennas are often required to produce a fan beam, with a narrow beamwidth in the elevation plane and a wide beamwidth in azimuth. Moreover, in some systems that employ polarization diversity the antenna produces two orthogonally polarized beams simultaneously. We will consider diversity configuration in which one antenna port is vertically polarized (VP) and the other is horizontally polarized (HP). The key aspect of such antennas for good diversity performance has been shown to be equal response to vertical and horizontal field components, i.e., similar radiation patterns in the two polarizations. The beamwidths in the azimuth plane are specified to cover a certain sector, which could be in the range of 30 degrees to 120 degrees.