Research And Design Of Multi-dimensional RF Energy Harvester

With the rapid development of Internet of things,the application scope of RF energy harvesting technology is gradually developing.As a rectenna in the RF energy acquisition system,it plays an important role in the system.The study of rectenna is devoted to collect more energy and improve the PCE(power conversion efficiency)in the limited power density environment.In the period of the RF energy collecting process,polarization mode and the combination mode of the rectifying circuit restrict the receiving ability of the energy harvesting system.In this paper,a reconfigurable omnidirectional circularly-polarized antenna is designed to improve the energy harvesting ability of the antenna by switching the polarization of antenna.The omnidirectional vertical polarization and dual polarization rectifying antenna array are designed.And the article discussed possibility of stabilizing the rectifying efficiency of the energy harvesting system with the power distribution network.Finally,the maximum power transmission efficiency method is used to optimize the feeding network and increase the parasitic substrate to improve the transmission efficiency of the transceiver antenna array.The main work of this paper includes:1.In this paper,a low-profile Reconfigurable Polarization omnidirectional circularly-polarized antenna is proposed.The antenna consists of a 1×4 dipole array antenna and a monopole antenna.By designing a reconfigurable feeding network to excite the two antennas,switchable dual circularly-polarized waves can be generated.The designed feeding network is mainly composed of a single-pole-double-throw switching circuit and a compact second-order 3-dB coupler,so that two outputs of equal amplitudes and switchable phase differences between±90°can be achieved.By connecting the two output ports of the feeding network with the horizontally-polarized dipole antenna array and the vertically-polarized monopole antenna,the whole antenna can be switched between the left-handed circular polarization(LHCP)and the right-handed circular polarization(RHCP)radiation states.The overall cross-sectional area of the designed antenna is 59.9×59.9×?mm²,while the thickness of the antenna is 0.058?₀.The measured results show that the impedance bandwidth(|S11|<-10 dB)of the antenna is 21.5%(2.24-2.78 GHz)and 19.4%(2.32-2.81 GHz)for LHCP and RHCP,respectively.The overlapped axial-ratio(AR)bandwidth(AR<3dB)of omnidirectional dual-circular-polarization state is about 7%(2.44-2.62 GHz).The maximum gain of the antenna is-0.9 dBic,while the gain variations in the horizontal plane is less than1.3 dB.2.In this paper,two kinds of rectenna arrays for RF energy acquisition are proposed,which work at 2.45GHz.Two kinds of antenna arrays are high gain omnidirectional vertical polarization rectenna array and vertical horizontal dual polarization omnidirectional rectenna array.When the incident wave direction and polarized angle are uncertain,the rectifying efficiency of the rectenna array is stabilized by adding a power distribution network.The simulated and measured results show that distributing the input power equally to rectifiers can stabilize the efficiency of the system.3.A 16×16 antenna array is excited by a feeding network in equal amplitude in phase.The network for the array is redesigned in the way of maximum power transmission efficiency method.In the simulation the transmission efficiency of the original antenna array is just 22.7%.In the measurement,transmission efficiency of the fabricated antenna array that has optimized feeding network can reach 25.4%in the distance of 3m.