Variable resolution direction finding using the robust symmetrical number system
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Authors
Lee, Anthony Kok Long
Subjects
Advisors
Pace, Phillip E.
Jenn, David C.
Walters, Donald L.
Date of Issue
2006-12
Date
Publisher
Monterey, CA; Naval Postgraduate School
Language
Abstract
A digital implementation of a phase sampling interferometer antenna system based on the Robust Symmetrical Number System (RSNS) is built using commercial-off-the-shelf (COTS) items. The RSNS-based direction finding (DF) system uses short baselines to achieve a high resolution DF capability in a physically compact system for use as stand-in sensors on unmanned aerial vehicles. The RSNS inherent integer Gray code property minimizes the possible encoding errors and adds a robustness to the accuracy of the estimated Angle of Arrival (AOA). A digital architecture using quadrature demodulators and real-time controllers provide grreater flexibility for signal processing and allows for the implementation of a new virtual spacing algorithm. The virtual spacing concept changes the RSNS moduli values to implement a virtual antenna spacing without having to physically change the antenna element spacing. This enables higher resolution DF in circumstances where the Signal-to-Noise Ratio is high enough to provide error free coding of the AOA. Two four element, digital 3-channel interferometer prototype systems were constructed and tested in the NPS anechoic chamber. The first antenna array is designed using pairwise relatively prime (PRP) moduli. When an extension of the virtual spacing concept for application to N-channel systems was successfully resolved, a second 3-channel array was built using non-PRP moduli for evaluating the performance of the virtual spacing concept. The simulated and experimental results, hardware implementation and testing procedures are presented in this thesis. Results for the first array show that the RSNS-based DF system is able to provide 0.7 degree RMS resolution with a baseline of 66 cm. For the second virtual spacing array, the short physical baseline of 14 cm was sensitive to noise and antenna spacing errors.
Type
Thesis
Description
Series/Report No
Department
Organization
Naval Postgraduate School (U.S.)
Identifiers
NPS Report Number
Sponsors
Funder
Format
xvi, 101 p. : ill. ;
Citation
Distribution Statement
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.