| Microwave power transmission technology is a new green and pollution-free contactless charging method,which breaks through various limitations of the traditional wired charging method.It can be applied to AI-robots,radio frequency identification,internet of things node deployment,5G communication,unmanned aerial vehicle space project,energy supply in hazardous environments and so on.The microwave power transmission system consists of a transmitter and receiver modules.Among them,the receiver is the core part of the system,which determines the working efficiency of the whole system.Its basic principle is to use the receiving antenna and the rectifier circuit to convert the environmental radio energy signal into the DC energy signal which available to the electronic equipment.Based on this background,the thesis studied the receiving antenna and rectifier circuit.The main research contents are as follows:According to the basic theory of receiving antenna and the design basis of dual band antenna,three kinds of microstrip patch antennas working at 2.45 GHz and 3.50 GHz were designed by simulation software.In order to improve the woring bandwidth of the antenna,and reduce the manufacturing cost and the antenna size,the improved methods of slotting,slotting loading and loading complementary split ring resonator structure was carried out on the antenna,so that the antenna can be better applied to the microwave energy transmission system.In the design process,several antenna model which contained different size parameters and structures were simulated,analyzed and compared,and the post-optimized antenna structure and size were determined.Finally,the antenna loaded with complementary split ring resonator structure was fabricated and tested,which is in ideal agreement with the simulation results.According to the basic theory of rectifier circuit and impedance matching,a single frequency rectifier circuit working at 2.45 GHz was designed by simulation software.The traditional straight-through filter,rectifier structure and single frequency matching network were simulated and analyzed in this software.Similarly,the optimized circuit size and structure were determined.Based on the single frequency rectifier circuit,a dual frequency rectifier circuit working at 2.45 GHz and 3.50 GHz was designed.A sector-shaped microstrip line harmonic suppression network with compatible harmonic suppression effect was designed,and the impedance matching network design was completed by the conjugate impedance matching method,which based on the Π-type structure proposed in this thesis.The simulation results show that the dual frequency rectifier circuit has good circuit performance.At two frequency points,the maximum rectification efficiency is 70.02% and 68.36% and the maximum output voltage is 2.97 V and 2.93 V.Combined with the results of cosimulation of the layout,the circuit is processed and made.The test results are close to the simulation results,and the circuit performance is good.The measured peak rectification efficiency can reach 61.61% and 58.67%,which can be effectively applied to the MPT receiver.Finally,the microwave energy transmission system composed of radio frequency source,low noise amplifier,transmitting antenna,receiving antenna,rectifier circuit,multimeter and radio frequency cable was built and tested.The peak efficiency of the system is up to 38.15%,which is greatly improved compared with the MPT system composed of other circuits. |
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