Design And Analysis Of Dual-band Rectenna For RF Energy Harvesting System

Radio frequency(RF)energy harvesting technology has become a new way to solve energy problems since it's a kind of low labor cost,environmentally friendly and sustainable power supply method.The technology has broad application prospects in such fields as internet of things(IoT),wireless sensor networks(WSN),microwave-driven pipeline robots and so on.RF energy harvesting refers to the harvesting of electromagnetic energy in the surrounding environment,which can be used as an energy source for a battery-free system or an auxiliary power source for the battery,which greatly improved the endurance of small electronic equipment.RF energy harvesting system mainly utilizes rectenna to receive and transmit energy.Due to the weak distribution of RF energy in the environment,the energy which received by the rectenna is small,thus the input power received by the rectifier from the receiving antenna is low.As a result,the output voltage is low,and it is difficult to be utilized effectively.Therefore,how to improve the energy conversion efficiency of the rectenna under low input power condition is the key research of this thesis.In this thesis,a dual-band rectenna for radio frequency energy harvesting is proposed in view of the problem of low energy conversion efficiency of traditional dual-band rectenna operating at 1.75 GHz and 2.45 GHz.The rectenna mainly consists of receiving antenna,double voltage rectifier,dual-band impedance matching network and terminal load.The main contents and contributions of this thesis are as follows:(1)Considering the frequency distribution of RF signal in the environment,a small dual-band microstrip patch antenna operating at 1.75 GHz and 2.45 GHz is designed for the application scenario of miniaturized equipments.Firstly,the theory and working principle of microstrip patch antenna are analyzed,and the design of slotting in the floor is introduced.Then the antenna is simulated by the high frequency structure simulation software(HFSS),and the structure parameters that affect the antenna performance are analyzed,then the optimal size of the antenna is obtained.Finally,the antenna is fabricated and measured,and the measured results are analyzed.The structure of the antenna is simple so that the size of the rectenna could be reduced effectively.(2)A novel impedance matching network is proposed due to the low energy conversion efficiency of traditional rectennas.The selection of rectifier diode type is carried out according to the need of the actual rectifier,and the basic principle of impedance matching is analyzed.In the dual-band environment,a new impedance matching network between antenna and double voltage rectifier is designed by utilizing stack architecture.The impedance matching network uses lumped parameter elements to reduce power loss and circuit size.The simulation and optimization of the rectifier are carried out by using the advanced design system simulation software(ADS),and the optimal parameters of the impedance matching network components are obtained.According to the selection of components type,the rectifier is fabricated and tested.The tested results show that the new rectifier design in this thesis has a smaller size and higher rectifying efficiency compared with the traditional dual-band rectifier under the same conditions.(3)The problem that the application performance of the actual rectenna is improved.The fabrication and experimental analysis of rectenna are carried out.It can be measured that in the common indoor environment,the trend of conversion efficiency varies with the input power changing from-30 dBm to-5dBm.The experimental results show that the optimal RF-DC conversion efficiency reach 65.34% and 54.3% in 1.75 GHz GSM band and 2.45 GHz WLAN band at the input power level of-10 dBm,respectively.Moreover,the experimental results show that the new rectenna can be applied in low-power consumption devices in IoT applications.