An Ultralow - Sidelobe Adaptive Array Antenna

One of the most important functions of a radar antenna is to provide spatial filtering that maximizes the radar's sensitivity in the desired sUIveillance direction while suppressing interference signals that enter the radar from other directions. This article describes a UHF radar antenna systemwith exceptional interference-rejection capabilities that are achieved through a combination of precision passive beamforming in the azimuth plane, and active, digital adaptive nulling in elevation. The antenna is composed of 14 stacked rows; each row contains a stripline, low-sidelobe, passive corporate-feed network. For signal reception, a separate receiver and analog-to-digital converter are used at each row output. The system adaptively combines the digitized row signals to form an elevation pattern with nulls at the elevation angles ofinterference sources. The antenna system is part ofan advanced air surveillance radar that Lincoln Laboratory is developing for the Navy. This article describes the design of the antenna system and presents performance analyses and measured results.