Input Impedance Stabilization of Finite Arrays of HIS-Backed Antenna Elements

When designing a phased array antenna, typically a unit cell is first optimized with periodic boundary conditions and then patterned into a finite array. However, there can be notable differences between the input impedances of elements designed with periodic boundary conditions and the same elements placed in a more realistic finite array. This paper presents a simple framework for explaining the cause of the finite effects, as well as a technique for suppressing them through strategic placement of conductive vias. An example wide band, low-profile antenna element composed of a dipole and high-impedance surface (HIS) is designed to demonstrate the technique, which improves input impedance consistency between the infinite periodic and finite simulation methods without requiring global optimization or individual matching of each element.