论文标题
用多铁纳米磁体实现的极端亚波磁弹性电磁天线
Extreme sub-wavelength magneto-elastic electromagnetic antenna implemented with multiferroic nanomagnets
论文作者
论文摘要
天线通常具有由a/（lambda）^2（a <lambda^2）界定的发射/辐射效率，其中a是发射区域，lambda是发射波长的波长。这使得将天线化到极端次波长尺寸的小型生效变得具有挑战性。克服这一挑战的一种方法是在发射波的共振上启动天线，而是在相同频率下具有较短波长的不同激发的共鸣。我们已经用表面声波（SAW）驱动电磁（EM）天线，其波长在相同频率下比EM波长小约五个数量级。这使我们能够实现极端的次波长EM天线，从而辐射出波长lambda = 2 m的EM波，其发射面积为〜10^-8 m2（a/lambda^2 = 2.5 10^-9），其测量的辐射效率超过了A/（Lambda）^2的限制超过10^5。天线由沉积在压电基底物上的磁刻度纳米磁体组成。一个锯在基板上发射的，交替的电压定期应对纳米磁铁，并因维拉里效应而旋转其磁化。振荡的磁化在锯的频率下排出了EM波。这些极端波长的天线，其效率比A/（lambda）^2限制大的数量级辐射，允许通信系统的急剧微型化。
Antennas typically have emission/radiation efficiencies bounded by A/(lambda)^2 (A < lambda^2) where A is the emitting area and lambda is the wavelength of the emitted wavelength. That makes it challenging to miniaturize antennas to extreme sub-wavelength dimensions. One way to overcome this challenge is to actuate an antenna not at the resonance of the emitted wave, but at the resonance of a different excitation that has a much shorter wavelength at the same frequency. We have actuated an electromagnetic (EM) antenna with a surface acoustic wave (SAW) whose wavelength is about five orders of magnitude smaller than the EM wavelength at the same frequency. This allowed us to implement an extreme sub-wavelength EM antenna, radiating an EM wave of wavelength lambda = 2 m, whose emitting area is ~10^-8 m2 (A/lambda^2 = 2.5 10^-9), and whose measured radiation efficiency exceeded the A/(lambda)^2 limit by over 10^5. The antenna consisted of magnetostrictive nanomagnets deposited on a piezoelectric substrate. A SAW launched in the substrate with an alternating electrical voltage periodically strained the nanomagnets and rotated their magnetizations owing to the Villari effect. The oscillating magnetizations emitted EM waves at the frequency of the SAW. These extreme sub-wavelength antennas, that radiate with efficiencies a few orders of magnitude larger than the A/(lambda)^2 limit, allow drastic miniaturization of communication systems.
