High Performance Electrically Scanned Antenna

The objective of the proposed Phase I effort is to perform a preliminary design of an electronically scanned antenna capable of supporting a multimode radar testbed operating in MTI, ultra-high range resolution and SAR modes. The proposed baseline antenna concept consists of four major components: a two-dimential antenna array of polarization-diverse radiating elements, a dual purpose elevation feed, an active Rotman lens azimuth feed and an azimuth beam steering network. Use of the active Rotman lens ("Wide Instantaneous Bandwidth Active Scanned Array", proposal dtd 5 Feb '92, submitted by Atlantic Aerospace Electronics Corp. to Harry Diamond Laboatory BAA ACT Committee) and a p-i-n diode switch beam steering network ("Low Cost Conformal Electronically Scanned Array", final report dtd 20 Sept '91, prepared by Atlantic Aerospace Electronics Corp. for Harry Diamond Laboratory under contract number DAALO2-91-C-0055) has been evaluated for radar antenna applications in the referenced earlier work and will not be considered in further detail in this proposal. The polarization-diverse elements will consist of dual-input elements with an integrated MMIC switch module to select vertical, horizontal, right-hand and left-hand circular polarizations. The elements will reside in a two-dimentional array such that each vertical, or elevation, column has a dual-mode selectable feed and all columns are fed in azimuth by the output ports of the Rotman lens. The selectable elevation feed will be designed to switch between two pattern modes: fixed cosecant-squared and monopulse. The azimuth feed distribution will be such as to achieve peak sidelobe levels of 25db below the main beam. System performance will be quantified by predictions of antenna patterns at different frequencies (5% about 16Ghz), azimuth scan angles (within + or - 45 deg.), elevation beam modes and polarization selections.