The Research And Application Of Low Power Microwave Rectification Technology

Microwave rectification is one of the key techniques that enable the microwave power transmission and harvesting. The technology usually utilizes the nonlinearity of rectifying diodes to convert microwave power to DC output voltage, which can be used to supply power wirelessly to portable electronic devices such as wireless sensor, making the equipments to get rid of the limit of battery life, In practical application, the reception and conversion of microwave energy are completed by rectifying antenna, which consists of receiving antenna and rectifying circuit. The paper mainly discusses several kinds of designs and realizations of low power rectifier circuits, as well as the approach to acquire higher rectifying efficiency, smaller circuit size and dual-band rectifier under ultra-low power input, According to the requirements of the low-power awakening module of active electronic tags and sensor nodes, a wireless control method of semiconductor switch based on microwave rectification is designed to achieve the wireless control of wake-up module with very low consumption. Specifically, the main work and achievements of this paper can be summarized as follows:(1) The nonlinear characteristic of rectifier diode is analyzed theoretically. Considering the energy demand of low power wireless sensor devices, a voltage doubler rectifier circuit at 900 MHZ is designed, fabricated and measured. It's proved that the rectification efficiency of 20.5% can be realized at-20 dBm input power.(2) A dual frequency rectifier circuit of series connection is realized, which has good operating characteristics at 2.16 GHz and 2.45 GHz, lying in UMTS and WIFI frequency bands, respectively. The circuit can achieved rectification efficiencies of 31.7% and 27.4% at-15 dBm input power, simultaneously.(3) A kind of wireless semiconductor switch control method based on microwave rectification is designed for the demand of active electronic tags and wake-up module with low power consumption of sensor node. A ring electrically small antenna with omnidirectional radiation characteristics is designed to be the receiving antenna for wireless wake-up signal, Aiming at achieving the maximum DC output voltage,the methods based on single antenna and dual antennas array are designed respectively. By the comparison of the two measured results, the rectification circuit in this paper is aimed to achieve the largest output DC voltage. Simulation and measurement results show that, with a two-element array design, the minimum required controlling voltage(1V) for turning on a typical CMOS switch can be achieved with an RF power level as low as-18 dBm received by both antenna elements.(4) To further improve microwave rectifier efficiency under low power input, the structure of rectifier circuit with multiple antenna array is researched and designed.In the structure, the total output dc power can be achieved by adding the multi-channel output dc power on the basis of the design of each antenna equipped with a separate rectifier circuit. Proved by the Analysis and simulation, the conversion efficiency of antenna array is better than that of single antenna. The measured results show that the conversion efficiency of 20.5% in single antenna can be obtained, while 22.5% can be achieved by antenna array at the condition of-20 dBm input power.