Research And Design Of A High Efficiency Rectenna

With the development of wireless communication technology,microwave power transmission technology has become one of the most popular study.The microwave power transmission technology breaks through the limitation of the transmission line and realizes the wireless transmission of energy.It not only can be applied to high power aspects,such as solar power satellite,high-altitude aircraft and power supply in remote areas,but also can be used in low power scenarios such as RF energy harvesting,wireless sensors and RFID tags.As an energy system,the efficiency of microwave power transmission systems is its main performance indicator.A rectenna which receives an RF power and converts it into DC power is one of the most essential devices for the wireless power transmission systems.Therefore,the design of a high efficiency rectenna is critical to microwave power transmission systems.Based on the design of the 2.45GHz rectenna,this paper study the methods of improving the rectification efficiency.The main work includes the following three aspects.Firstly,the rectifier diode modeling were studied.Aiming at the limitations of the ideal diode model in the design of a rectifier,a modeling method based on diode S-parameter measurement and equivalent circuit fitting is proposed.Firstly,the TRL calibration method is analyzed and the corresponding test bracket and TRL calibration piece are designed.The diode test circuit is built by vector network analyzer,Bias Tee and DC voltage regulator.The S-parameters of the diode were measured from 1 GHz to 8 GHz.According to the measured S-parameter and equivalent circuit model of the diode,the voltage-independent component values are extracted and the expressions of junction capacitance and junction resistance are obtained by fitting.A new diode model was built that is closer to the actual diode than the known model.Secondly,the structure of the rectifier circuit has been improved.The rectifier circuit is designed based on the measured diode model.The low-pass filter part of the conventional rectifier circuit is replaced by a ?/8 band-stop structure,and the whole circuit is optimized by introducing a fan-shaped through-pass filter and a double-branch matching structure.By comparing with the simulation results of the conventional rectifier,the rectification efficiency of the improved circuit is increased by 7.1%.Finally,when the input power is 13dBm and the load is 750?,the improved rectifier circuit has a high efficiency of 74.8%.Thirdly,a receiving antenna with high gain and circular polarization is designed.The high gain performance of the antenna ensures that the rectifier circuit receives sufficient input power,while the circular polarization characteristic reduces losses due to polarization mismatch.The element of the receiving antenna is in the form of a square patch.The circular polarization characteristic is achieved by cutting the patch.In order to achieve high gain,an 2×2 array antenna is formed by using microstrip antenna elements.Meanwhile,for an array antenna having a better circularly polarized performance,the element of the array antenna is fed with an equal amplitude and a phase difference of 90° by a T-type power divider.Through the final measurement,the axial ratio of the array antenna is 0.9dB and the gain is 12.5dB,which realizes the design requirement of high gain and circular polarization.