Modeling a tunable plate in a leaky wave antenna

An acoustic leaky-wave metamaterial is an array of cells comprised of ducts and plates and is used for beam steering. The phase interactions caused by the combination of ducts and plates can result in effective material properties not found in natural materials. Natural materials and metamaterials without plates can steer the output radiation lobe in a limited range of 90°, whereas leaky-wave metamaterials can steer in a full range of 180°. This metamaterial is typically passive and has a narrow frequency bandwidth. It can also be difficult to avoid a directivity discontinuity in the center of the bandwidth if there are manufacturing errors, material flaws, or design miscalculations. By adding tunable diaphragms between the unit cells, it is theoretically possible to design a metamaterial that can shift the bandwidth by changing the magnitude of the tunable mass density or tunable bulk modulus. This article shows a computational model for a tunable leaky-wave antenna and predicts how incorporating a piezoelectric diaphragm affects the output of the system.