Novel techniques of polarization diversity and extended-aperture spatial diversity for sensor-array direction-finding in radar, sonar, and wireless communications
Abstract
An array of diversely polarized antennas can resolve impinging sources based on the sources' different polarizational states in addition to the sources' different directions-of arrival (DOA). Alternately in the sonar environment, an array of diversely oriented velocity-hydrophones can exploit DOA information embedded in the acoustic particle velocity vector-field, in addition to the scalar pressure field. Array aperture extension using sparse array configurations enhances direction-finding (DF) accuracy and resolution capabilities without undue increase in hardware and software costs. The main part of this presentation involves the use of electromagnetic vector-sensors, each of which is composed of six spatially co-located, orthogonally oriented, diversely polarized antennas, distinctly measuring all six electromagnetic-field components of an incident multi-source wave-field. The pivotal insight is that the DOA's may be estimated from the Poynting-vector estimates obtainable from each vector-sensor's steering vector. This vector-sensor based DF provides DOA estimates independent of the traditional estimation based on the phase shifts between the sensor-array's spatially displaced elements as in interferometry. These two separate approaches to DOA estimation allow: (1) extension of intervector-sensor spacing in a uniform array geometry beyond the Nyquist half-wavelength maximum in a closed-form ESPRIT-based DF algorithm, while disambiguating the resultant cyclic ambiguity using the Poynting-vector DOA estimates as coarse references, (2) derivation of coarse DOA estimates to initiate a MUSIC-based iterative search algorithm for any irregularly spaced array of vector-sensors, (3) closed-form DF using only one vector-sensor under certain signal scenarios, (4) closed-form DF using any array of sonar vector-sensors at unknown and arbitrary locations. (The sonar vector-sensor is composed of co-located but orthogonally oriented velocity-hydrophones & a pressure-hydrophone.) Two other DF methods not using the aforementioned vector-sensors are: (5) a close-form Root-MUSIC-based DF algorithm allowing adjacent spatially displaced antennas to have different polarizational states, and (6) an extended-aperture ESPRIT-based algorithm applicable with identical scalar-sensors spaced in a novel geometry with dual sizes of spatial invariances. These various novel DF methods result in order-of-magnitude improvements in estimation accuracy and resolution capability compared with customary non-diversely-polarized half-wavelength spaced interferometry-type DF approaches.
Degree
Ph.D.
Advisors
Zoltowski, Purdue University.
Subject Area
Electrical engineering
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