Design of realistic phased array patch elements using a genetic algorithm

Presently most wide band array elements are complicated 3-dimensional structures which are difficult and costly to manufacture. Therefore we explore planar patch elements which offer a simplified geometry with potentially reduced weight and cost and are suitable for conformal applications. We use a genetic algorithm to design a patch element in a unit cell of an infinite periodic array and model the feed with the usual δ-gap voltage source. However, since this feed is a non-realizable mathematical concept, we also explore the antenna performance achieved with several realistic feeds. For broadside arrays we obtain a bandwidth B ≈ 4:1 both with the δ-gap and with the realistic feeds. For arrays with scan angles out to 45°, the initial bandwidth B ≈ 2:1 with the δ-gap is reduced to B ≈ 1.7:1 with a differential coaxial feed, whereas the initial bandwidth is maintained with a GA-optimized custom feed. The element profiles range from 0.13 λ_L to 0.17 λ_L, where λ_L denotes the wavelength at the low end of the operational band.