Design Of Wide Dynamic Range Rectennas And Research Of Rf Energy Harvesting System

The booming development of the Internet of Things technology and 5G technology has led to the application of many low-power sensors,which makes higher requirements on radio frequency energy harvesting technology.As the core of the RF energy harvesting system,the performance of the rectenna is critical.It contains receiving antenna and rectifier circuit,requiring that they perform well when they work alone.And more importantly,they should be integrated efficiently to form a system.This thesis focuses on the key point in RF energy harvesting.It mainly studies the efficient reception of electromagnetic waves by microstrip antennas and the efficient conversion of RF energy based on Schottky diodes,aiming to achieve the design of a wide dynamic range rectenna.And then combined with the power management circuit and energy storage module,an efficient RF energy harvesting system is built.The main work of this thesis includes the following aspects:The first is research and design of low power RF rectifier circuit.For low-power scenes,this thesis chooses the suitable topology and the Schottky diode with the low on-voltage drop,to design a 2.45 GHz single-band rectifier,a 1.8GHz and 2.4GHz dual-band rectifier,respectively.Among them,the 2.45 GHz rectifier achieves more than 40% efficiency under the-10 d Bm input power condition and 28% efficiency under the-20 d Bm input power condition.And then the design method of a 2.4GHz wide dynamic range rectifier based on a new impedance compression network is proposed.When the input power is-10 d Bm,the efficiency can maintain more than 45% as the load resistance varies from 3000? to 6000?,which improves the environmental adaptability of the rectifier.The second is the design of rectenna and the RF energy harvesting system.Aiming at the diverse polarization characteristics and frequency characteristics of electromagnetic wave in the air,the structure and radiation principle of the microstrip antenna are analyzed.Based on the three-dimensional electromagnetic simulation software HFSS,a 2.4GHz dual-polarization antenna and a 1.8GHz and 2.4GHz dual-band antenna with circular polarization are designed.Among them,the 2.4GHz dual-polarization antenna has a radiation gain of 5d Bi.The polarization characteristics of the dual-band circularly polarized antenna are frequency selective.It exhibits left-handed circular polarization characteristic when working at 1.8GHz,and right-handed circular polarization characteristic at 2.4GHz.Next,the 2.4GHz wide dynamic range rectifier and the 2.4GHz dual-polarization antenna are integrated into a common PCB board to realize the integrated design of antenna and rectifier to form a rectenna.Finally,combined with the power management circuit,an energy storage module,together with the antenna and rectifier,a RF energy harvesting system is formed,which can effectively support the normal operation of the low power consumption sensors.The third is miniaturization design of wide dynamic range rectenna array.By changing the traditional impedance matching method,the impedance of the antenna is directly conjugated with the rectifier impedance,which reduces the power loss caused by the matching network and realizes the miniaturization of the rectenna array.A simple square patch is used as the antenna radiating unit.Four rectifier circuits are connected behind each patch,two of which are responsible for the low-power region below-10 d Bm,and the others are responsible for the power range of-10 d Bm to 0d Bm.Afterwards,four rectennas are formed into the 2 ? 2 small arrays,and then the circuit loads of the same power region are combined in parallel.Finally,field and circuit collaborative verification are performed.In the range of 2.3GHz to 2.45 GHz,when the power changes from-20 d Bm to 0d Bm,the energy conversion efficiency of the rectenna array can be maintained at more than 30%,while the highest efficiency in different power regions both exceed 50%.