A new class of tunable multi-layer meta-surfaces

A new class of tunable multi-layer meta-surfaces is presented whereby the proposed structures produce very low losses at millimeter wave frequencies. Two configurations are investigated as working examples of the proposed tuning technique. Initially, a tunable high impedance meta-surface is being studied, consisting of a square loop element printed on a dielectric substrate and placed over a ground plane creating an air cavity. Subsequently, the transmission and reflection properties of double layer meta-surfaces consisting of two square aperture arrays printed on dielectric substrates and separated by an air cavity are presented. Tuning of the reflection phase of the high impedance meta-surface and the bandpass filter response of the double layer meta-surface is achieved by means of piezoelectric actuators positioned around the surfaces. The proposed actuators dynamically change the thickness of the air cavities in both configurations, due to their property of expanding vertically under DC biasing, which results in tuning the reflection and transmission characteristics of the structures.