Tuning periodic surfaces with piezoelectric actuators

A periodic surface with tunable phase response is presented here for operation at around 60GHz. The tuning is achieved by means of piezoelectric actuators. The periodic surface consists of a two dimensional square loop metallic elements array printed on a 0.8mm thick dielectric substrate. It is placed at close proximity (50um) over a ground plane creating an air cavity and acting as a High Impedance Surface (HIS). The actuators are employed to produce a displacement between the periodic surface and the ground plane which in turn changes the reflection phase response of the structure. Full wave periodic analysis has been carried out in 3D electromagnetic simulation software (CST Microwave Studio^TM) to extract the reflection characteristics and evaluate the expected tuning range of the proposed structure. A phase shift of 80^o degrees has been achieved at 58.5GHz for a displacement of 15um.