Conventional two-dimensional phased arrays face two major shortcomings: the presence of ambiguities in direction of arrival measurements and beam broadening endfire effects. The literature provides methods for addressing and minimizing these problems on conventional planar phased array structures, but there has been no investigation into solving these issues with three-dimensional geometries. In this thesis, the design and performance of a cubic phased array that can eliminate endfire effects and dramatically improve direction of arrival ambiguity resolution is investigated. Both beamforming and direction of arrival simulations are performed in MATLAB and 4nec2 simulation environments for cubic phased arrays of various sizes and at different frequencies and demonstrate that the endfire effects are eliminated and direction of arrival ambiguity resolution is dramatically improved. These findings are expected to lead to new designs of high fidelity three-dimensional phased arrays. / Master of Science / Conventional two-dimensional, flat, plane antenna arrays have revolutionized how sensing and detection systems perform. These systems, however, face two major shortcomings due to their "flat" geometry. The computation that determines the direction from which an object is approaching or a signal has been transmitted will have two solutions that are opposite each other in the same way that the polynomial expression x2 = +2 or -2 has two solutions that are opposite each other. This is known as the ambiguity problem and presents major uncertainty in direction finding or direction of arrival measurements. The second major shortcoming has to do with transmitting a signal at different directions. The antenna elements in the array are stationary, but the beams that each element transmits can be aimed in specific directions by controlling the phase of the voltage sources for each respective antenna. This is why it is called a phased array. When every element is transmitting directly forward, it is known as broadside. As the voltage sources for the elements are shifted, or steered, away from this direction, it is known as beam steering. When the beam is steered 90 degrees from the broadside direction, the beams of one column of elements are actually transmitting into the next column of elements, effectively transmitting out of a one-dimensional line array. This is known as endfire and has significant negative effects that are often desired to be avoided. Current scientific literature provides methods for addressing and minimizing these problems on conventional two-dimensional planar phased array structures, but there has been no investigation into solving these issues with three-dimensional geometries. In this thesis, the design and performance of a cubic phased array is presented. The cubic phased array eliminates endfire effects entirely because each face of the cube is identical; when transmitting at 90 degrees off broadside, the transmit area of the cube is identical to that of the broadside direction. The cubic geometry also dramatically improves the direction-finding process. By introducing a third dimension, the mathematics can more precisely determine the direction from which the object or the signal is coming, thus dramatically decreasing the ambiguity simply as a function of geometry. Both beam steering and direction of arrival simulations are performed in MATLAB and 4nec2 simulation environments for cubic phased arrays of various sizes and at different frequencies. This demonstrates that the endfire effects are eliminated and direction of arrival performance is dramatically improved. These findings are expected to lead to new designs of high fidelity three-dimensional phased arrays for a multitude of applications, especially for space applications where the three-dimensional geometry has the added benefit of resolving the requirements for compensation for the tumbling motion of objects in orbit.

The complex relationship between array gain patterns and microphone distributions limits the application of traditional optimization algorithms on irregular arrays, which show enhanced beamforming performance for human speech capture in immersive environments. This work analyzes the relationship between irregular microphone geometries and spatial filtering performance with statistical methods. Novel geometry descriptors are developed to capture the properties of irregular microphone distributions showing their impact on array performance. General guidelines and optimization methods for regular and irregular array design are proposed in immersive (near-field) environments to obtain superior beamforming ability for speech applications. Optimization times are greatly reduced through the objective function rules using performance-based geometric descriptions of microphone distributions that circumvent direct array gain computations over the space of interest. In addition, probabilistic descriptions of acoustic scenes are introduced to incorporate various levels of prior knowledge for the source distribution. To verify the effectiveness of the proposed optimization methods, simulated gain patterns and real SNR results of the optimized arrays are compared to corresponding traditional regular arrays and arrays obtained from direct exhaustive searching methods. Results show large SNR enhancements for the optimized arrays over arbitrary randomly generated arrays and regular arrays, especially at low microphone densities. The rapid convergence and acceptable processing times observed during the experiments establish the feasibility of proposed optimization methods for array geometry design in immersive environments where rapid deployment is required with limited knowledge of the acoustic scene, such as in mobile platforms and audio surveillance applications.

In this work, a novel method is proposed to optimize the array geometry for DOA estimation. The method is based on minimization of fine error variances with the constraint that the gross error probability is below a certain threshold. For this purpose, a metric function that reflects the gross and fine error characteristics of the array is offered. Theoretical analyses show that the minimization of this metric function leads to small DOA estimation error variance and small gross error probability. Analyses have been carried out under the assumptions of planar array geometry, isotropic array elements and AWGN. Genetic algorithm is used as an optimization tool and performance simulation is performed by comparing the DOA estimation errors of optimized array to a uniform circular array (UCA). Computer simulations support the theoretical analyses and show that the method proposed leads to significant improvement in array geometry in terms of DOA estimation performance.

The goal of this master’s thesis is to explore the possibilities of multichannel localization of acoustic signal sources and their following application on a real signal localization and separation, using Beamforming methods. During this thesis two beamforming methods were selected, namely Delay and Sum a Constant Directivity Beamforming - Circular Arrays, and were applicated on real environment signals using two microphone arrays’ geometries ULA (Uniform linear array) and UCA (Uniform Circular array).