Microwave wireless energy transfer and storage for railway Internet of Things

The Internet of Things (IoT) system for rail transportation can achieve real-time monitoring and warning of rail structure engineering, which is an effective means to ensure its safe operation. At present, sensors can only be powered by batteries, which have limited capacity and inconvenient replacement, restricting the development of IoT systems for rail transportation. This paper studies a low-power and high-efficiency microwave rectifier circuit that allows devices to harvest energy from the surrounding environment and convert it into electrical energy for self-use. Under the condition of an input power of 15 dBm and a load resistance of 660 ohm, the output voltage is 3.95V, achieving an rectification efficiency of over 70%. At the same time, a harmonic suppression antenna is designed and developed to suppress second harmonics and higher frequencies. Considering that the operating voltage of the sensor MCU is generally around 3V, in order to obtain a relatively high voltage, after obtaining direct current voltage through rectification, energy storage is performed through a supercapacitor. Then, boost is achieved through a DC-DC boost circuit to provide suitable voltage for subsequent circuits.