Dynamically reconfigurable high impedance and frequency selective metasurfaces using piezoelectric actuators

Novel dynamically reconfigurable low-loss high impedance and frequency selective metasurfaces (FSmSs) are presented, operating at around 15 GHz and incorporating compact piezoelectric actuators. The high impedance metasurface (HIS) consists of an array of metallic elements printed on a thin dielectric substrate, placed over a ground plane, and supported by the actuators. Under a dc bias, the actuators produce a displacement between the two layers, resulting in a change in the reflection phase response. Furthermore, novel multilayer FSmSs are proposed achieving significant tuning of their passband response with low losses. The FSmSs consist of three closely spaced periodic arrays of subwavelength nonresonant elements, namely, an array of metallic square loops placed between two arrays of square apertures in metallic sheets, separated by air cavities. The combination of the square loop array and one of the square aperture arrays produces a high impedance surface response, which is tuned using the piezoelectric actuators. This in turn alters the resonance condition of the complete FSmS structure and thus the central frequency of the passband. The structures have been investigated through simulations and measurements with good agreement, achieving an experimental frequency tuning range of 17% for the HIS and of 8.8% for the FSmS as well as a maximum phase shift of over 177° for the HIS at approximately 14 GHz.