Design of Large Effective Apertures for Millimeter Wave Systems Using a Sparse Array of Subarrays

We investigate synthesis of a large effective aperture using a sparse array of subarrays. We employ a multi-objective optimization framework for placement of subarrays within a prescribed area dictated by form factor constraints, trading off the smaller beam width obtained by spacing out the subarrays against the grating and side lobes created by sparse placement. We assess the performance of our designs for the fundamental problem of bearing estimation for one or more sources, comparing performance against estimation-theoretic bounds. Our tiled architecture is motivated by recent progress in low-cost hardware realizations of moderately sized antenna arrays (which play the role of subarrays) in the millimeter wave band, and our numerical examples are based on 16-element ($4 \times 4$) subarrays in the 60GHz unlicensed band.