Radio frequency patch antenna reconfiguration with Ni–Ti shape memory alloy switches

Abstract

Nickel–titanium shape memory alloys are employed to develop a multiband radio frequency antenna. Switches made from Ni–Ti electronically connect together a planar patch antenna arrangement, creating several electrical signal pathways that enable reconfiguration via resonance shifting. The changes in the antenna geometry, induced by the switches, create different working frequencies. The switches open and close due to an induced phase change from martensite to austenite via resistive heating from a separate electric circuit. A patch antenna was fabricated and then measured for S11 reflection coefficient, antenna gain, and radiation pattern at different configurations. The results show that the working frequency of the patch antenna arrangement is tunable from 2.25 to 2.43 GHz depending on the antenna geometry, while the antenna always maintains a high gain. The experimental results match well with simulations, indicating the potential for simulated design of future applications and geometries through shape memory actuators.