End-Fire Array Enhancement with Gradient-Based Numerical Optimization

Endfire linear arrays comprising isotropic radiators are optimized for sidelobe reduction and additional suppression of the first sidelobes. Our approach utilizes the sequential-quadratic programming algorithm exploiting analytical derivatives of the array directivity with respect to the designable parameters, as well as initialization through a smart random search. Several test cases varying in the number of design variables and optimization constrains are considered. The initial design, the reference, is the Hansen-Woodyard (HW) design. It was possible to essentially nullify the first sidelobes, without compromising the directivity compared to the HW design and without shrinking the inter-element spacing. A comprehensive numerical study is provided.