Symmetric Inter-Antenna Spacing Constrained Sparse Arrays for DOA Estimation of Mixed Near-Field and Far-Field Source Signals

A symmetric sparse array, termed as the symmetric inter-antenna spacing constrained array (SISC), is proposed for unambiguous direction of arrival (DOA) estimation of mixed near-field and far-field source signals. This SISC array is designed from the perspective of assembling four uniform linear subarrays, while balancing the uniform degree of freedom (uDOF) and array sparseness. The SISC array may involve only one closely spaced antenna pair with spacing the quarter of signal wavelength, while synthesizing a contiguous processing aperture with large uDOF. The minimum inter-antenna spacing of SISC can also exceed the quarter of signal wavelength (without closely spaced antenna pair), if reducing antenna mutual coupling is preferred. Simulation results are provided to verify the superiority of SISC to the current symmetric sparse arrays, in terms of antenna mutual coupling, uDOF, processing aperture and DOA estimation accuracy.