Pushing Piezoelectric Transmitters to the MHz Regime

Transmitters driven by piezoelectric resonators have been shown to radiate quasistatic electromagnetic waves in the low frequency and very low frequency (LF and VLF) bands. These devices make use of the inverse piezoelectric effect to convert continuous-wave excitation into mechanical stress and strain that is oscillatory in nature. This leads to the generation of electrical charge that accelerates onto floating electrodes exploiting topological symmetry, which results in dipole-like field radiation. The radiation efficiency can be three orders of magnitude greater than that of conventional electrically-small antennas operating in this frequency range. To our knowledge, this is the first time that radiation has been shown with lithium niobate (LiNbO3) acoustically-driven transmitters operating in the MHz regime. The measured results from a line-of-sight spatial power drop-off experiment show great promise for physically realizable transmitters much smaller than the current state-of-the-art at these frequencies. These devices offer great potential to be used as compact low-power transmitters on platforms constrained by power and volume, such as drones, quadcopters, and microsatellites. It is suggested that arraying these devices may allow for much more compact spacecraft radar and communication hardware, which can greatly benefit the overall system performance.

由压电谐振器（piezoelectric resonators）驱动的发射器已被证明可在低频和甚低频（LF和VLF）波段辐射准静态电磁波（quasistatic electromagnetic waves）。这类器件利用逆压电效应（inverse piezoelectric effect）将连续波激励转换为本质上呈振荡性的机械应力与应变。这会产生电荷，该电荷借助拓扑对称性（topological symmetry）加速至浮动电极上，进而形成类偶极场辐射（dipole-like field radiation）。其辐射效率可比同一频率范围内工作的传统电小天线（electrically-small antennas）高出三个数量级。据我们所知，这是首次证实采用铌酸锂（LiNbO3）的声驱动发射器在MHz频段工作时可产生辐射。视距空间功率衰减实验（line-of-sight spatial power drop-off experiment）的测量结果表明，在这些频率下，可物理实现的发射器有望远小于当前最先进的同类产品。这类器件在功率和体积受限的平台（如无人机、四旋翼飞行器和微卫星）上具有作为紧凑型低功耗发射器的巨大潜力。研究表明，将这类器件阵列化可实现更紧凑的航天器雷达与通信硬件，从而显著提升系统整体性能。