Electrically Large Circular Loops in the Estimation of an Incident Emitter's Direction-of-Arrival or Polarization

Electrically small loops have been the focus of the research literature on loop-antenna signal processing, but such electrically small loop-antennas are electromagnetically inefficient. Electrically large loop-antennas will instead be analyzed here in this paper, in the context of estimating an incident source's direction-of-arrival or polarization. Specifically, three large loop-antennas here are collocated and are oriented orthogonally, in order to measure all three Cartesian components of the incident magnetic field simultaneously all at one specific spatial position. This orthogonal triad offers azimuth-elevation bivariate directivity despite the three loops' spatial collocation. For such a triad of electrically large loops, this paper (first in the open literature) formulates the array manifold, develops the corresponding algorithms in closed form to estimate an incident source's azimuth-elevation direction-of-arrival or polarization, and demonstrates these proposed estimators' precision as close to the Cramér-Rao bounds.