Impedance characteristics of magnetoelectric antennas
Authors: Song Kai-Xin , Min Shu-Gang , Gao Jun-Qi , Zhang Shuang-Jie , Mao Zhi-Neng , Shen Ying , Chu Zhao-Qiang ,   Key Laboratory of Underwater Acoustic Technology, Harbin Engineering University, Harbin 150001, China,   Key Laboratory of Marine Information Acquisition and Security, Ministry of Industry and Information Technology (Harbin Engineering University), Harbin 150001, China,   Underwater Acoustics College of Engineering, Harbin Engineering University, Harbin 150001, China,   Innovation and Development Center, Harbin Engineering University, Qingdao 266071, China
Published: September 2022

Mechanical antenna, a novel scheme for realizing very low frequency (VLF) and portable transmitters, has been investigated recently. In this work, the impedance characteristics of 1-1 type of and 2-1 type of magnetoelectric (ME) mechanical antennas are systematically studied and compared with each other. Based on the measured frequency-impedance curves and the corresponding modified Butterworth-van Dyke (MBVD) model, three characteristic frequency points, i.e. the minimum impedance frequency <inline-formula><tex-math id="M5">\begin{document}$ {f}_{\rm{m}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20220591_M5.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20220591_M5.png"/></alternatives></inline-formula>, the series resonance frequency <inline-formula><tex-math id="M6">\begin{document}$ {f}_{\rm{s}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20220591_M6.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20220591_M6.png"/></alternatives></inline-formula>, and the resonance frequency <inline-formula><tex-math id="M7">\begin{document}$ {f}_{\rm{r}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20220591_M7.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20220591_M7.png"/></alternatives></inline-formula> are obtained and discussed. On this basis, the influence of driving voltage, bias magnetic field, and the quality factor (<i>Q</i> value) on ME antenna impedance characteristics are experimentally explored. Finally, the reactance components of both 1-1 type of and 2-1 type of ME antenna are collected by referring to the actual working frequency <inline-formula><tex-math id="M8">\begin{document}$ {f}_{\rm{d}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20220591_M8.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20220591_M8.png"/></alternatives></inline-formula>. Experimental results prove that the resonant ME antennas are basically pure resistive vibrators, while an ME antenna with high <i>Q</i> value normally fails to support high driving field because of the low resistance (< 100 Ω) and the strong nonlinearity. Thus, the field radiation capability in 2-1 type of ME antenna is higher than that in 1-1 typed one. This work provides the ideas for choosing <i>Q</i> value and further optimizing a magnetoelectric antenna based on the understanding of its impedance characteristics.