Array Analysis for Predicting Multipolarization DF Performance, 16-R9584

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Principal Investigator
Jackie E. Hipp

Inclusive Dates:  10/01/05 – 04/01/07

Background - During beam steer direction finding, performance is jeopardized whenever the steered beam exhibits a sidelobe response with such large magnitude that the main beam and sidelobe cannot be reliably distinguished on the basis of observed magnitude alone. For skywave scenarios, the DF array response beam is a two-dimensional surface of response versus steering azimuth and steering elevation. In addition, the two-dimensional mainbeam and sidelobes also depend on the incident polarization. This project has developed a capability for analyzing any multipolarization array manifold to estimate DF performance for any desired set of skywave signal-parameter values. 

Approach - Estimating DF performance for a multipolarization DF system required supporting development of an estimator for array manifold errors and a multipolarization array manifold analysis capability that predicted the consequent distribution of DF errors. The array manifold error estimator development was based primarily on iterative analyses of self-consistency within the tabulated array manifold. The multipolarization array manifold analysis development included a method for identifying and quantifying characteristics of the main beam and sidelobes, both of which are functions of azimuth, elevation, and complex polarization. The DF error estimator accounted for the influences of array manifold errors and the main beam and sidelobe descriptions.

Accomplishments - This project developed a straightforward set of non-iterative routines for very rapidly analyzing a multipolarization array manifold and delineating those polarizations that produce a beam response above or below any specific level. This analysis is directly applicable to any multipolarization array manifold, regardless of the array, the array environment, or the distribution of incident polarizations. The ability to efficiently perform these estimates provided a practical basis for choosing a multipolarization array design with the most effective skywave DF performance. Prior to this development, the primary design alternative had been to use Monte Carlo simulations in which many random combinations of polarization were incorporated into repeated simulations of noisy measurement, requiring several orders of magnitude more time to compare the multipolarization DF performance among different candidate DF arrays.

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