Frequency Response Characterization of Thin-Film Shape Memory Alloy Actuator for Reconfigurable Antenna

The frequency response characteristics of a thin-film shape memory alloy (SMA) actuator have been studied to check its applicability as a switching element in a reconfigurable antenna. The thin-film SMA actuator is a composite structure comprising of thin-film CuAlNiMn SMA material coated on a flexible straight polyimide substrate. The actuation is achieved by the martensite to austenite phase change of the SMA through Joule heating in the heating cycle and the flexible polyimide acting as the bias element in the cooling cycle. The performance of the actuator is studied by applying voltage signals of different amplitudes and varying frequencies to it. It was observed that the actuator has the maximum displacement with minimum offset in the frequencies between 0 Hz and 1 Hz of a 3-V sinusoidal signal. The response of the actuator to a sinusoidal signal of different frequencies has also been analyzed using finite element analysis in COMSOL Multiphysics^®. The experimental results match well with the simulation results which help in deciding the operating bandwidth of the proposed thin-film SMA actuator. The application of the actuator as a switching element in connecting two rectangular microstrip patch antennae to achieve frequency reconfiguration is discussed conceptually. Furthermore, the length of the actuator was reduced and the corresponding displacements were measured to determine its effective functioning in reconfigurable microstrip patch antennae, where a microscale geometry is essential.