Characterizing and Improving the Probability of Correct Phase Ambiguity Resolution for Uniform Circular Array Phase Interferometers

Correct phase ambiguity resolution (CPAR) for a uniform circular array (UCA) phase interferometer is formally defined and some theoretic results for CPAR are derived. The probability of CPAR is numerically investigated considering the impact of baseline formulation, number of elements, radius wavelength ratio and phase measuring mechanism. Three methods for improving the probability of CPAR are proposed based on the findings of the characteristics of UCA phase interferometers. An extensive numerical investigation is conducted to validate the effectiveness of the proposed methods. The investigation results validate the effectiveness of the proposed methods and suggest choosing among the three proposed methods by considering the specific needs and engineering limitations.

I. Introduction

Phase interferometer is a widely used direction finding mechanism. Typical application of phase interferometer systems includes object tracking, geolocation, efficient communication, signal source classification, orbit determination, etc [1] –[6]. A phase interferometer measures several groups of signal phase differences among the selected elements of an antenna array. Direction finding is then conducted based on the established mapping between the phase differences and DOAs. Typical methods for DOA estimation include the analytic approach and the least square (LS) approach. Ambiguity occurs when one tries to improve the direction finding accuracy by lengthen the baselines [7]. It is well known that for a basic two-element interferometer ambiguities begin to occur when the baseline is longer than half of incoming signal wavelength, since the phase difference can only be measured in the sense of modulo . To overcome such problems, many efforts have been devoted to ambiguity resolution for phase interferometers.