C-Axiszig-zag polarization inverted ScAlN multilayer for FBAR transformer rectifying antenna

Energy harvesting from surrounding electromagnetic wave can satisfy the increasing demand of trillions of wireless sensors for IoT. RF energy harvesting is generally achieved by RF-DC conversion using a rectifying antenna (called rectenna). For weak RF signal, however, RF-DC conversion efficiency significantly decreases because weak RF signal cannot activate the diode in the rectenna. Therefore, in order to obtain high conversion efficiency for a weak signal, a Dickson charge pump[1] is generally used to increase the RF voltage. However, their low efficiency, poor impedance matching, and large size are the problem. In this study, to overcome this problem, we introduce the RF energy harvester consisting of a new type of polarization inverted FBAR transformer and rectenna. As shown in Fig.1 (a), RF input signal can be increased 7 times when 8 polarization inversion layered FBAR transformer is used. We previously reported various polarization inverted structure such as (0001)/(000-1) ScAlN films [2] and (-1-120)/(11-20) AlN films [3]. We here reports the eight layer of c-axis zig-zag polarization inverted ScAlN stack transformer resonator. [1] A. Parks, et al. Proc. IEEE WiSNET, (2013). [2] M. Suzuki, T. Yanagitani, and H. Odagawa, Appl. Phys. Lett. (2014) [3] M. Suzuki, T. Yanagitani, IUS 2011, 4C-2 (2011).