| WPT (Wireless power transfer) technology refers to a process of transmitting energy. At the transmitter, the dc energy is transformed into radio frequency energy. Then it is transferred in the form of electromagnetic waves in the space. Finally, it is received by the receiver and can be used in the form of dc energy. Wireless power transmission technology can be divided into near-field and far-field WPT. The former transfers energy through the electromagnetic coil coupling, while the latter emits radio frequency energy from the antenna at the transmitter, and the energy is received at the receiving end, the radio frequency energy then converted to dc power through a rectenna (rectifier antenna). Compared to traditional wired power transmission, wireless energy transmission is more suitable for some special occasions. On the other hand, with the rapid development of wireless communication, the radio frequency energy density in the surrounding environment is increasing. The idea of using small amounts of idle radio frequency energy to power low-power electronic devices through energy harvesting is gaining more and more attention. In the receiving end and the energy harvesting system of the far-field wireless energy transmission system, rectenna is a key module to achieve RF-dc conversion,and there has been a lot of research at home and abroad. Therefore, based on the research of the existing rectifier antenna technology, this thesis discusses the analysis and design method of the rectifying antenna applied in different scenes. The main work are as follows.(1) In this thesis, three broadband multi-frequency rectifier circuits and one broadband multi-frequency antenna are designed and implemented for RF energy harvest system with wide frequency and low energy density. As a result, single-branch broadband rectifier circuit can collect energy at band of GSM1800 / GSM2100, the highest efficiency is 56.4%. The dual-branch and three-branch broadband multi-frequency rectifier circuit can collect the energy of GSM900 / GSM2100 / Wi-Fi and GSM900 / GSM1800 /GSM2100 / Wi-Fi band respectively, the highest efficiency is 57.5% and 55.9%. The three-branch rectifier circuit, compared to the broadband rectifier circuit published abroad with same input power, has increases the GSM900 frequency band, and the level of conversion efficiency is similar.Based on the existing broadband antenna with slotted structure, low-frequency resonance is generated by adding the coupling slot resonant patch,and finally formed the broadband multi-frequency antenna. The antenna can cover GSM1800 / GSM2100 / Wi-Fi frequency band and some GSM900 frequency band, and can be loaded in front end of the broadband multi-frequency rectifier circuit as the receiving antenna.(2) A large dynamic range rectifier circuit operating at 5.8GHz is designed for the large transmission power and power fluctuation situation in wireless power transmission system. The dynamic range of the rectifier circuit is further extended by adopting the technology of adaptive multi-diode cascade large dynamic rectifier circuit based on the FET switch and the reconfigurable power divider. The dynamic range of input power greater than 40% is extended from 4dBM-15dBm to 4dBM-29dBm for single series diode structure, and the simulation efficiency is up to 61%. The power input dynamic range compared to the large dynamic rectifier published abroad which reached almost the same conversion efficiency, has broadened 13 dBm. |
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