| Wireless power transmission mainly includes laser power transmission and microwave power transmission(MPT), MPT draws the more and more researchers’ attention because of its advantages such as less space power loss and high conversion efficiency, and it has been widely used in such as driving unmanned aerial vehicle, the airship power transmission, solar microwave power transmission according to their long distance transmission. As the receiving front-end of MPT system, rectenna affects the transmission and conversion efficiency of the whole system, and plays as the key factor to decide the conversion efficiency of the system. How to guarantee the efficiency of the system in the condition of highly dynamic input on mobile platforms is one of the technical problems.In view of rectenna’ application when receving the large dynamic power, this paper conducted the following researches based on the existing researches:① Deeply analyzing the theory of MPT system. Due to that rectenna mainly includes receving antenna and rectifier circuit, firstly, the radiation mechanism and efficiency theory of antenna are analyzed; then introducing the rectifier diode theory in detail, and analytical method is used in deriving the closed formula of the rectifying efficiency of ideal case as a function of the input power and output impedance separately.②A dual-band dual-polarized antenna is proposed. Substrate integrated waveguide(SIW) comprises a series of advantages of rectangular waveguide and microstrip line. On the basis of SIW and considering the metamaterial structure of miniaturization and fractal structure, this paper proposed a dual-band dual-polarized antenna. The proposed antenna consists of two feed ports, and two complementary split ring resonators(CSRR) to realize the coupling between the radiator and transmission line. As a result, interference between the two frequencies can be decreased by this way. Simulation and measured results of the proposed antenna show that this antenna can be used for power transmission and communication of MPT.③ A circuit scheme which can convert large dynamic microwave power into DC is proposed. Reflection loss caused by impedance mismatch in traditional rectifier circuits will reduce the efficiency of the whole MPT system, so a circuit scheme is proposed to solve this problem. Reflection microwave is rectified by multilevel rectifier circuit to improve efficiency of rectification in the proposed circuit. In addition, the reflection wave is prevented transmission back to the receiver, it can avoid the secondary radiation caused by the antenna which radiates the reflection wave to the air. The specific circuit board was fabricated according to the former analysis. The difference test results between the traditional rectifier circuit and the proposed circuit show that this scheme can work efficiently in large dynamic microwave power conversion. |
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