David A. New

Date of Award

3-24-2016

Document Type

Thesis

Degree Name

Master of Science in Electrical Engineering

Department

Department of Electrical and Computer Engineering

First Advisor

Phillip M. Corbell, PhD.

Abstract

Most phased array systems subarray many antenna elements into far fewer digitized channels. While having more degrees of freedom (DOF) yields better performance, adding channels to create more digital DOF increases system cost and data throughput requirements. A subarray itself constitutes a phased array with as many DOF as it has antenna element weights. Typically, only one degree of freedom is used to steer the maximum gain direction of the subarray pattern. For typical antenna geometries a single subarray will provide many more spatial DOF than there are digitized channels. The inherent DOF of the subarrays could be used to mitigate selected interference signals with the subarray pattern if the antenna manifold, the angle of arrival (AOA), and the power of interference sources at the array face are known. Interference AOA and power can be derived from external knowledge sources (e.g., intelligence, additional sensor packages, monopulse beams) or can also be found by processing channel data. The AOA and power estimates can then be used to adapt a subarray pattern to null interference and restore dynamic range while allowing digital DOF to be utilized for other purposes (such as clutter mitigation). Simulations are used to illustrate the implementation tradeoffs and a proposed concept of operations for dividing spatial nulling duties between subarray and digital beamformers, referred to herein as Knowledge-Aided Subarray Pattern Synthesis (KASPS). Performance is simulated for multiple antenna geometries and interference parameters. The technique is shown to outperform conventional digital-only adaption for subarrayed antennas and approach optimum performance bounds under some conditions. KASPS is shown to improve performance even with misestimated interference parameters, unknown manifold error, and quantized subarray weights.

AFIT Designator

AFIT-ENG-MS-16-M-037

DTIC Accession Number

AD1053858

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