Research On The Key RF Technology Of Microwave Power Transmission

In recent years, wireless power transmission (WPT) has become an intriguing solution for contactless powering of low-consumption electronic devices. WPT can be achieved by different approaches such as near-field inductive coupling, magnetic resonant coupling, and microwave power transmission (MPT). Comparing with other WPT technologies, MPT exhibits significant advantages on the ability of energy transfer direction controlling and long range radio frequency (RF) power transmission. At present, the technology has been applied in the field of wireless sensor networks, radio frequency identification (RFID), microwave driven aircraft and so on. The key technologies of Microwave power transmission(MPT) include high efficiency transmitter, high gain & high beam control accuracy antenna and the high efficiency rectenna. As the microwave power source technology is relatively mature, its performance is not much space for improvement. The performance of the transmitting antenna directly affects the efficiency of the system. The rectenna, acting as microwave-to-dc power converter, is the key component in MPT systems and one of the top factors determining the efficiency of the MPT.In this thesis, we focus on the research of high gain & high beam control accuracy array antenna, and high efficiency rectenna.(1) A four element linear phased array with a working frequency of 2.4GHz is designed. The phased array consists of element antenna and feed network. The array element antenna is used in microstrip Yagi antenna.And the feed network is composed of the power distribution network and the phase shift network. The power distribution network designed in this thesis is composed of Wilkinson power divider. Two types of phase shifter are designed, one analog phase shifter which is based on the 3dB directional coupler, and one 5 bit digital phase shifter which is based on the load line. When the feeding network is composed of analog phase shifter,the beam scanning range is -13.5°-13.5° by HFSS simulation. The designed 5-bit digital phase shifter, step 11.25°, phase-shifting error of up to 3°.(2 ) A novel circular polarization rectenna with multiorders harmonic suppression is proposed in this thesis. The circular polarization is realized by corner perturbation on a rectangular radiation patch, and enhanced by a diagonal slim slot etched at the center of the patch. An open stub connects to the transmission line is used to suppress harmonics. The realized results show that the antenna obtained -18dB return loss at 2.4GHz, and -7dB,-20dB and -20dB suppression on second to fourth harmonic frequency bands respectively. With a voltage doubling rectifier circuit connecting to the output of the antenna, 75% of RF-to-DC conversion efficiency is achieved.In this paper, the anti-jitter (input power) of the rectified antenna is analyzed in depth, and the solution is proposed, but the effect needs to be further optimized.