Investigation Of High-efficiency Rectifier With Wide Input Power Range In Wireless Power Transmission

In recent years, the microwave wireless power transmission(WPT) is becoming a hot research topic. The microwave rectifier which can convert the received RF power into DC power is a crucial part of the WPT system. However, the received power is varied due to the effect of the power loss and multipath reflection. Therefore, it is valuable to investigate the methods for improving the power range of the rectifier. In this thesis, the rectifying technologies and the techniques for improving the power range were investigated and summarized. Based on this, the rectifying techniques are studied in detail and three methods for improving the input power range are presented. The main work can be summarized as follows in three parts:1. The high-efficiency rectifier based on two sub-rectifiers with unequal optimized input power levels is presented. The two sub-rectifiers whose input powers crossponding to the highest PCE are different are combined through the unequal power divider. The two rectifiers can work at the highest efficient mode in different input power. Firstly, the rectifier circuits are analyzed in theory and then simulated by software. Good agreement between the simulation and measurement results validates the proposed methods.2. A differential rectifier based on impedance compression network(ICN) is presented. For the input impedance of the rectifier is varied as the input power changes, the conventional impedance network can only be designed to match the input impedance at certain input power level. Therefore, the power range is reduced due to the mismatching at other input power levels. By adding the ICN between the source and the rectifier, the change of the impedance of the rectifier can be reduced. Therefore, the rectifier can achieve high PCE wthin wider input power range. Firstly, two voltage doubler rectifiers are designed as the two sub-rectifiers for realizing the differentially-driven rectifier. The operating mechanism of the voltage doubler and the ICN are investigated to give the guideline for designing the differentially-driven rectifier based on ICN. The proposed designs are simulated by software. Good agreement between the simulation and measurement results validates the proposed methods.3. Impedance modulated rectifier is proposed. Two sub-rectifiers with unequal input power level corresponding to the optimized efficiency are designed. They are combined with the microstrip line balun. The power on the two sub-recitifiers is modulated by controlling the different impedances of the sub-rectifier. When the incident power is low, the power on the lower-power recitifier is higher than the higher-power circuit and it will achieve the optimized efficiency in some input power level. When the incident power is high, the power on the higher-power recitifier is higher than the lower-power circuit and it will reach the optimized efficiency in high input power.