A self calibration technique for a DOA array in the presence of mutual coupling and resonant scatterers

Determining the Direction-of-Arrival (DOA) of any signal of interest has long been of great interest to the research community. This is important for both commercial and military applications. DOA estimation is one of the main functional requirements for Direction-Finding (DF) smart antennas in future wireless communication systems.; This dissertation focuses on a DOA array calibration methodology in the area of electromagnetics, and contains two main concepts. An often neglected issue in an array operation is the fact that the elements and near-zone scatterers affect each other, and disturb proper array operation. By compensating for the undesired mutual couplings, the achievable DF performance will be improved. Several numerical examples are given to illustrate the advantages and limitations of the methods in each chapter.; The first concept is a self-calibration technique for a DOA array to automatically remove the effects of mutual coupling and near-zone resonant size scatterers whose locations are known but whose geometries are unknown. The term self calibration implies that an iterative process automatically recovers the desired receive voltages with the effects of near-zone scatterers removed by employing multipole expansions of the unknown scattered fields. The array configuration such as the element number and the element geometry, and thus its Method of Moments (MM) impedance matrix [Z], are to be known. Beginning with the array currents contaminated by both mutual coupling and near-zone scatterers, the applied iterative method determines the uncontaminated method of moments voltage vector, and eventually the DOAs. The method uses the degrees of freedom of the array to determine the coefficients in a harmonic expansion of the scattered fields, the uncontaminated DOA angles, the complex magnitude of the incident plane waves, and the true current shapes on the array elements. The technique is applicable to the problems of multiple scatterers and multiple incidences whose amplitudes may be different with each other.; The second concept is a procedure, termed the Inverse Method of Moments (IMM), which is capable of determining the method of moments (MM) impedance [z] matrix and voltage v vector for a Uniform Linear Array (ULA), given its terminal currents i produced by plane waves from known directions. Although the ULA is assumed to be composed of identical elements, the element geometry, gain pattern, polarization, and mutual coupling is not known. The array is illuminated by an unknown number of incident plane wave of unknown complex amplitude and polarization. It will be shown that the IMM can be combined with an iterative technique to determine the array DOA angles with mutual coupling effects removed. The degrees of freedom of the array are used to determine and remove the effects of mutual coupling, and thus the array can determine the DOAs of the incident plane waves and their complex amplitudes, but not their polarizations.