Design and Analysis of Antenna Arrays for Adaptive Array Processing: Interference Mitigation, Direction of Arrival Estimation, and Radar

Abstract

This dissertation explores the design and analysis of small antenna arrays for various array processing applications, such as interference mitigation, direction of arrival estimation, and terrain mapping radars. Both antenna engineering and signal processing perspectives are taken into account to improve antenna characteristics as well as array processing performances, as specified below. First, three different approaches are introduced to minimize the effect of mutual coupling for better radiation characteristics. A novel feeding mechanism is presented to improve the isolation for dual-band operation in small arrays whose aperture diameter is much smaller than a wavelength, and the mounting angle of each array element is optimized to further improve the isolation. Then, a methodology for maximizing the physical distance between array elements is introduced to improve the null steering performance by using a polarization adjustable microstrip patch antenna. Second, optimum array configurations are introduced for two different objectives: improved null depth and width for adaptive array patterns in stationary systems and fast null steering time for mobile environments. The null depth and width are improved by using subarrays with auxiliary elements arranged on a spherical curvature, and the null steering time is minimized by the vertical placement of the center reference element. Third, a systematic approach of antenna placement is introduced to minimize the platform effects for accurate direction of arrival estimation in a harsh platform environment. Physical insights on the platform effects are obtained by using a generic arc-wall shape, and the approach is extended to a more realistic military aircraft model to demonstrate its utility. Finally, an approach to terrain mapping radars is presented to investigate the effect of antenna characteristics on radar scan images using an equivalent terrain model. The transmit beamforming scheme is used to investigate the proper array configuration for receiving antennas, and digital beamforming is applied to find the configuration for transmit antennas. Other effects of EM properties, such as wave scattering, blockage, diffraction, reflection, and side lobe effects, are also discussed.