| In this paper, Firstly, functions of the rectenna in Microwave Power Transmission, WirelessPower Supply and Resource Recycling of free spce are introduced. The operation principle andcomponents of rectenna system are also introduced. The rectenna system in this paper is composedof receiving antenna with harmonic rejection, voltage doubler rectifier circuit at low input powerand DC load. The Microwave in free space is received by receiving antenna and then changed intoDC power for load by rectifier circuit.A flat low-pass microstrip filter at2.45GHz is designed and applied to rectenna system.Simulation of schematic and layout are done. Attenuation of the filter is27dB at4.9GHz (secondharmonic) and60dB at7.35GHz (third harmonic). Filter is usually applied to rectenna for reducinghigh harmonic in traditional rectenna system. In this paper,Method of harmonic rejection isresearched. The system uses a improved antenna with harmonic rejection instead of using afilter,SIR structure is applied to the antenna.The improved rectenna system can suppress harmonic.The paper also analyses the efficiency of the system.According to the princples of rectangular microstrip antenna and SIR structure,the papercalculates the sizes of antenna with harmonic rejection and simulate it. The result of simulation iscompared to result of traditional antenna.It shows that the return loss of the antenna is-2dB atsecond and third harmonic.Studies of rectifier circuit is discussed in the paper.The circuit in this paper chooses voltagedoubler circuit because of the wide application scope. It studies rectifier circuits at low input powerand designs three different circuits. All these circuits can work when the input power is higherthan-20dBm.The efficiency of these cricuits is around50%at0dBm.The highest efficiency canreach75%and the DC output voltage can reach6V. Finally,processing, debugging and testing arecompleted.The testing results are closed to the results of simulation.The efficiency reaches90%. |
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