Uniform Concentric Circular and Spherical Arrays with Frequency Invariant Characteristics: Theory, Design and Applications

This dissertation, "Uniform Concentric Circular and Spherical Arrays With Frequency Invariant Characteristics: Theory, Design and Applications" by Haihua, Chen, 陳海華, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract Abstract of the Thesis Entitled Uniform Concentric Circular and Spherical Arrays with Frequency Invariant Characteristics: Theory, Design and Applications submitted by Chen Haihua for the degree of Doctor of Philosophy at the University of Hong Kong in July 2006 This thesis proposes a new theory and design of digital beamformers for uniform concentric circular arrays (UCCAs) and uniform concentric spherical arrays (UCSAs) having nearly frequency invariant (FI) characteristics. The basic principle of the proposed sensor arrays is to transform the received signals to the phase mode and remove the frequency dependency of the individual phase mode through a digital beamforming or compensation network. As a result, the far field pattern of the array, which is governed by a set of variable beamformer weights, is electronic steerable and is approximately invariant over a wider range of frequencies than conventional uniform circular and spherical arrays. The design of the compensation filters is formulated as a second order cone programming (SOCP) problem, which can be solved optimally for minimax and least squares criteria. iiBased on the proposed FI UCCAs and UCSAs, new broadband direction-of- arrivals (DOA) and adaptive beamforming algorithms are developed. Specifically, by employing the beamspace approach derived from the outputs of a set of fixed UCCA frequency invariant beamformers (FIBs), a new beamspace MUSIC (multiple signal classification) algorithm is proposed for estimating the DOA of broadband sources. A similar broadband DOA algorithm based on ESPRIT (estimation of signal parameter via rotational invariance techniques) using UCSA-FIB is also developed. Due to the frequency invariant property of the proposed UCCA-FIB and UCSA-FIB, a very efficient adaptive beamformer using the minimum variance beamforming (MVB) approach can be developed. To reduce computational complexity, new recursive adaptive beamforming algorithms for UCCA-FIB and UCSA-FIB are proposed based on the MVB and generalized sidelobe canceller (GSC) methods. To mitigate DOA and sensor position errors, robust versions of these adaptive beamforming algorithms are also studied. Simulation results show that the proposed adaptive UCCA-FIB and UCSA- FIB are numerically better conditioned than the conventional broadband tapped delay line-based adaptive beamformers, due to the frequency invariant property and significantly fewer numbers of adaptive parameters. The reduced number of adaptive coefficients also leads to lower arithmetic complexity and faster tracking performance than conventional methods. Furthermore, a higher output signal to inference plus noise ratio (SINR) over the conventional approach is observed. The usefulness of the proposed UCCA-FIB and UCSA-FIB in robust beamforming algorithms and broadband DOA estimation is also verified by computer simulations. Due to the geometrical limitation of UCCA, its beam pattern is not steerable in three dimensions and the resolution is not uniform around the elevation angle. The iiiUCSAs, on the other hand, are electronic steerable and have uniform resolution in both the azimuth and elevation angles. The uniform beam pattern and resolution of UCSAs in both the azimuth and elevation angles are verified by computer simulations. An abstract of exactly 436 words iv