Antennas typically have emission/radiation efficiencies bounded by A /λ²(A < λ²) where A is the emitting area and λ is the emitted wavelength. That makes it challenging to miniaturize antennas to extreme subwavelength dimensions without severely compromising their efficiencies. To overcome this challenge, an electromagnetic (EM) antenna is actuated with a surface acoustic wave (SAW) whose wavelength is about five orders of magnitude smaller than the EM wavelength at the same frequency. This allows to implement an extreme subwavelength EM antenna, radiating an EM wave of wavelength λ = 2 m, whose emitting area is ≈10⁻⁸ m² (A /λ² = 2.5 × 10⁻⁹), and whose measured radiation efficiency exceeds the A /λ² limit by over 10⁵. The antenna consists of magnetostrictive nanomagnets deposited on a piezoelectric substrate. A SAW launched in the substrate with an alternating electrical voltage periodically strains the nanomagnets and rotates their magnetizations owing to the Villari effect. The oscillating magnetizations emit EM waves at the frequency of the SAW. These extreme subwavelength antennas that radiate with efficiencies a few orders of magnitude larger than the A /λ² limit allow drastic miniaturization of communication systems.

中文翻译：

---

多铁性纳米磁体实现的超亚波长磁弹性电磁天线

天线通常具有由界定发射/辐射效率甲/λ ²（甲<λ ²），其中阿是发射区域，λ是发射波长。这使得在不严重损害天线效率的情况下将天线小型化到极限亚波长尺寸具有挑战性。为了克服这一挑战，用表面声波（SAW）驱动​​电磁（EM）天线，该表面声波的波长比相同频率下的EM波长小大约五个数量级。这允许实现一个极端的亚波长EM天线，辐射的EM波的波长λ= 2米，其发光面积是≈10 ^-8米²（阿/λ² = 2.5×10 ^-9），其测量的辐射效率超过阿/λ ²通过在10极限⁵。天线由沉积在压电基板上的磁致伸缩纳米磁铁组成。由于维拉里效应，利用交流电压在衬底中发射的声表面波会周期性地使纳米磁体变形并使它们的磁化旋转。振荡的磁化强度以SAW的频率发射EM波。这些极端亚波长天线辐射即与效率大小比较大的几个数量级阿/λ ²限制允许通信系统的急剧小型化。