An Unconventional Shape Memory Alloy Low-Power Ratchet for Reconfiguring the Polarization of a Moiré Pattern-Based Antenna

In this article, a novel polarization reconfigurable antenna based on the Moiré effect is proposed. The presented design exploits substantial changes in the overlapped Moiré patterns to minimize the needed actuation for antenna reconfiguration. The novel antenna design is based on stacking two circular FR4 substrates on top of a truncated edge rectangular patch antenna. The top layers of both the substrates are milled into horizontal stripes forming the Moiré patterns. One of these substrates is fixed with respect to the antenna, while the second one rotates with respect to the fixed substrate. Upon rotation, these stripes from the two substrates overlap in pattern, which shapes the antenna. As a result, the antenna design is capable of switching its polarization scheme between vertical, horizontal, and circular with left-hand orientation. In addition, the Moiré patterns can also enhance the directivity and gain of the proposed antenna. The reconfiguration’s mechanical actuation is achieved via a nontraditional ratchet mechanism that uses shape memory alloys (SMAs). This realized actuation system is fast, flexible in its positioning, has low energy expenditure, and minimizes interference with antenna operation. An antenna prototype is fabricated and tested where measured results match the simulated performance.