Research Of RF Energy Harvesting Device Based On Wideband And High Gain Antenna

RF energy harvesting technology can utilize the radio-frequency(RF)energy to power low-power electronic devices,which is one of the effective means to realize the conversion of RF energy and DC energy.In this paper,in order to improve bandwidth and gain of the receiving antenna as well as increase the conversion efficiency of the rectifier,three novel and practical rectenna and a DC/DC boost energy storage circuit with the low voltage input are designed.Firstly,this paper introduces the development and fundamental structure of RF energy harvesting system as well as the current research situation in the world,then the research direction of rectenna is summarized.The distribution of ambient RF energy,the primary technologies of circular polarization,wideband and high gain,as well as the requirement of antenna performance are presented.In addition,the selection process of rectifying diode and its topology,the nonlinear analysis of the rectifier input impedance,and the simulation example of the single-stage voltage double rectifier are also proposed.Meanwhile,the design method of narrow band,double frequency and broadband matching circuit is introduced.Secondly,a 2.4GHz circular polarization microstrip rectenna is presented.The receiving antenna adopts dual feed microstrip antenna with loop slot,achieving bidirectional circular polarization,wideband and high gain characteristics.A single frequency rectifier with low loss characteristic is constructed by adding single frequency matching circuit on the basis of single stage voltage double rectifier circuit.Through processing and testing the receiving antenna and rectifier,it is verified that the rectifier antenna has a high rectifying efficiency in the 2.4GHz band at low power.Thirdly,this paper proposes two wideband circular polarization rectenna.One is triple band circular polarization rectenna,the receiving antenna adopts the orthogonal dipole antenna,which realizes the circularly polarized radiation with the help of the selfphase shift feeding structure of three-fourths delay line.By introducing the parasitic patch and the fine dipole pair between the adjacent dipole arms,the impedance width and the axial bandwidth are improved.The other one is four band circular polarized rectenna.The receiving antenna adopts the dipole array antenna,which can realize the circular polarization with the help of power split phase shifting structure.It also extends the impedance and axial bandwidth and improves the gain by means of the dipole arm deformation and the addition of the metal arm.On the basis of single-stage double voltage rectifying circuit,three frequency and four frequency band matching circuits are added respectively to form three frequency and four frequency rectifier.The two rectennas are manufactured and tested,and the results show that they can cover GSM1800/UMTS2100/2.4GHz band and GSM900/GSM1800/UMTS2100/2.4GHz band respectively.In addition,the results demonstrate that the multitone input signals can enhance the overall conversion efficiency of rectifier,too.Finally,a DC/DC boost energy storage circuit applied to the output end of rectenna is proposed.On the basis of the power management chip LTC3108,the external circuit consisting of the booster converter,supercapacitor and capacitors is added.So,in the case of low voltage input,a higher output voltage can be get,and the excess dc power can be stored in the supercapacitor.