Direction of arrival (DOA) estimation using electrically small resonant dipole antennas

In this paper we present a methodology for the direction of arrival (DOA) estimation using the induced voltages that are measured at the feed points of electrically small resonant dipole antenna arrays illuminated by the signal of interest. The matrix pencil method is applied directly to the induced voltages to estimate the DOA of the various signals. Using electrically small resonant antennas can be advantageous if they are spaced half a wavelength apart as it will significantly reduce the mutual coupling between the various antenna elements. However, the electrically small antennas can also be placed in close proximity of each other saving the real estate and thus making it possible to deploy phased arrays on small footprints. For the latter case it may be necessary to use the transformation matrix to compensate for the strong mutual coupling that may exist between the antenna elements. The transformation matrix converts the voltages that are induced at the loads corresponding to the feed point of the array operating in the presence of mutual coupling and other near field scatterers to an equivalent set (ULVA) consisting of omni-directional isotropic point radiators equally spaced and operating in free space. Three different scenarios are presented to illustrate the methodology. First we consider resonant dipole elements spaced half wavelength apart, electrically small resonant antenna elements spaced half wavelength apart and electrically small resonant antenna elements placed in close proximity of each other to reduce the footprint without affecting the performance of the phase array. Numerical examples are presented to illustrate the principle of this methodology.