Sharma Raghav, Mishra Rahul, Ngo Tung, Guo Yong-Xin, Fukami Shunsuke, Sato Hideo, Ohno Hideo, Yang Hyunsoo
Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore.
Centre for Applied Research in Electronics, Indian Institute of Technology Delhi, New Delhi, India.
Nat Commun. 2021 May 18;12(1):2924. doi: 10.1038/s41467-021-23181-1.
The mutual synchronization of spin-torque oscillators (STOs) is critical for communication, energy harvesting and neuromorphic applications. Short range magnetic coupling-based synchronization has spatial restrictions (few µm), whereas the long-range electrical synchronization using vortex STOs has limited frequency responses in hundreds MHz (<500 MHz), restricting them for on-chip GHz-range applications. Here, we demonstrate electrical synchronization of four non-vortex uniformly-magnetized STOs using a single common current source in both parallel and series configurations at 2.4 GHz band, resolving the frequency-area quandary for designing STO based on-chip communication systems. Under injection locking, synchronized STOs demonstrate an excellent time-domain stability and substantially improved phase noise performance. By integrating the electrically connected eight STOs, we demonstrate the battery-free energy-harvesting system by utilizing the wireless radio-frequency energy to power electronic devices such as LEDs. Our results highlight the significance of electrical topology (series vs. parallel) while designing an on-chip STOs system.
自旋扭矩振荡器（STO）的相互同步对于通信、能量收集和神经形态应用至关重要。基于短程磁耦合的同步具有空间限制（几微米），而使用涡旋STO的远程电同步在数百兆赫兹（<500 MHz）范围内频率响应有限，限制了它们在片上GHz范围应用中的使用。在此，我们展示了在2.4 GHz频段使用单个公共电流源以并联和串联配置对四个非涡旋均匀磁化的STO进行电同步，解决了基于STO设计片上通信系统时的频率-面积困境。在注入锁定下，同步的STO表现出出色的时域稳定性和显著改善的相位噪声性能。通过集成电连接的八个STO，我们展示了利用无线射频能量为诸如发光二极管等电子设备供电的无电池能量收集系统。我们的结果突出了在设计片上STO系统时电拓扑（串联与并联）的重要性。
