Frequency tunable patch antenna with electrically actuated supported polymer membrane

In this paper, we present a frequency-agile microstrip patch antenna printed on a new soft elastomeric polyurethane (PU) substrate (ε_r ≈ 3.5 at 10 GHz). Membrane suspended over an air cavity technology is used to increase the antenna efficiency (η ≈ 31.7%) in frequency X band and adds a supplementary degree of freedom in the purpose of frequency agility. The membrane deflection is realized by electrical actuation (electromechanical reconfiguration) and changes the air gap height between the patch and the ground plane and thus the resonant frequency. This actuation depends on the initial strain of the membrane. So, a frequency shift from 9.61 to 9.12 GHz (5.23% under 145 V) is obtained when the membrane is relaxed. Besides, it is also shown the potentiality of beveled structure to improve the deflection control and strongly reduce the required applied DC voltage to reach close tunability (4.10% under 30 V).