Coherent sources direction finding and polarization estimation with various compositions of spatially spread polarized antenna arrays

Various compositions of sparsely polarized antenna arrays are proposed in this paper to estimate the direction-of-arrivals (DOAs) and polarizations of multiple coherent sources. These polarized antenna arrays are composed of one of the following five sparsely spread sub-array geometries: (1) four spatially spread dipoles with three orthogonal orientations, (2) four spatially spread loops with three orthogonal orientations, (3) three spatially spread dipoles and three spatially spread loops with orthogonal orientations, (4) three collocated dipole-loop pairs with orthogonal orientations, and (5) a collocated dipole-triad and a collocated loop-triad. All the dipoles/loops/pairs/triads in each sub-array can also be sparsely spaced with the inter-antenna spacing far larger than a half-wavelength. Only one dimensional spatial-smoothing is used in the proposed algorithm to derive the two-dimensional DOAs and polarizations of multiple cross-correlated signals. From the simulation results, the sparse array composed of dipole-triads and loop-triads is recommended to construct a large aperture array, while the sparse arrays composed of only dipoles or only loops are recommended to efficiently reduce the mutual coupling across the antennas. Practical applications include distributed arrays and passive radar systems.