| The rapid development of Internet of Things technology promotes the application of wireless sensors,and its power supply problem also attracts people's attention.Microwave energy harvesting system has become a new power supply mode with its advantages of all-weather use,long working time and low maintenance cost.It inputs the electromagnetic energy distributed in space to the system through the receiving antenna and outputs the DC voltage for the operation of the device by using the AC/DC conversion capability of the rectifier circuit.This paper mainly studies the rectifying antenna system for microwave energy harvesting,which mainly includes the RF receiving antenna and rectifying circuit.Although microwave energy is widely distributed in space,its energy density is very low and the practical frequency band is not abundant.Therefore,it is necessary to improve the receiving capacity of the antenna as much as possible and reduce the loss in the transmission and rectification process,so as to ensure adequate output.In order to improve the rectification efficiency,this paper designs Vivaldi wideband receiving antenna and coplanar waveguide feeding circular polarized antenna based on the microstrip antenna.By adding grids to the Vivaldi antenna to improve the feed,broadband reception in the range of 1.1GHz?5.2GHz was achieved with a gain of more than 9d B.By using the partial feed and slot for the circular polarization microstrip antenna fed by the coplanar waveguide,the circular polarization output in the frequency range of 1.9GHz?3GHz is realized and the axis ratio in the working bandwidth is less than 5d B.The RF energy received by the antenna is transferred to the rectifier circuit for energy conversion,and the final output is DC power.The rectifier circuit determines the final output and conversion efficiency of the system.This paper analyzes the rectifier diode's performance,selects the appropriate Schottky rectifier diode as the main device and uses the voltage multiplier full-wave rectifier's performance to realize the rectifier function.The circuit is simulated and optimized in ADS.In addition,in order to reduce the reflection loss,the impedance analysis of the rectifier circuit is carried out,and therectifier circuit is matched to the input 50 ohms with a two-branch matching structure.In the main operating frequency band,voltage output of more than 300 m V can be achieved with an input of-10 dbm and a load of 4000 ohms,and the rectification efficiency is greater than 24%.Finally,the simulation model is used to make and test the real object,and the validity of the results is verified.Simulation results show that the actual working bandwidth of Vivaldi antenna is 1.15GHz? 6.1GHz,and the reflection coefficient at each frequency point is less than-20 d B.Compared with the simulation results,the reflection coefficient of the rectifier circuit is reduced to-11.27 d B.Microstrip patch antenna has stable voltage output of 110 m V and 160 m V under different emission sources while Vivaldi antenna has the voltage output of 300 m V and 400 m V.The function of microwave energy harvesting can be realized. |
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