On beam design for sparse arrays of subarrays using multi-objective optimization and estimation-theoretic criteria

Compact antenna arrays with a moderately large number of elements (e.g., 16 elements in a 4× 4 planar configuration) can be realized at low cost at millimeter wave frequencies. This provides the opportunity for cost-effective synthesis of large aperture antenna arrays using sparse placement of such compact “subarrays”. In this paper, we investigate the design of arrays of subarrays constructed in this fashion, constraining the number of subarrays and the size of the area over which they are placed, with a view to mitigating the grating lobes created by multi-wavelength separation of the subarrays. We consider multi-objective optimization of directivity, beamwidth, maximum sidelobe level and beam eccentricity. While exhaustive search for the space of optimal solutions is computationally infeasible, we obtain intuitively plausible configurations using simple search strategies for finding local minima. We compare example configurations based on their performance for Direction of Arrival (DoA) estimation.