| Wireless Power Transfer(WPT)technology is a technology based on a non-wire contact method that uses microwave beams to realize the transmission of electric energy from the transmitting end to the receiving end(large-scale rectenna array)in free space.WPT is wildly used for wireless charging,Miniature detection robots,UAV base stations,solar satellite systems and other applications.For millimeter-wave wireless energy transmission applications,the efficiency and cost of millimeter-wave rectifier antenna arrays will determine whether the WPT system can be used on a large scale.The core is to design low-cost,high-efficiency,fully integrated rectifier chips and antennas,which will become is the key breakthrough point for wireless energy transmission in the millimeter wave frequency band.This paper has carried out in-depth research on the high-efficiency,low-cost rectifier chip and rectifier antenna array in the W-band.The main research contents and contributions of the paper are summarized as follows:(1)A Ka-band rectifier is designed.Aiming at the lack of suitable high-frequency rectifiying structure in CMOS process and the serious problems of high-frequency parasitics,a series of new technologies are proposed and applied,such as the proposed current source switching transistor rectifying structure.Detailed theoretical analysis and mathematical derivation are given.The structure has great advantages in rectification efficiency,bandwidth and input power range.A new type of transistor layout technology is proposed to reduce the high-frequency parasitic parameters of the transistor and ensure the high-frequency performance of transistors in millimeter wave;the chip area of the rectifier is only 0.116mm~2,and the rectifying efficiency is as high as 36.5%.The rectification efficiency can compete with similar Ga As products using Schottky diodes,and the bandwidth exceeds 11GHz,which proves the feasibility of the rectifying structure.(2)Focus on the design and implementation of the W-band rectifiers.First,a W-band current source switching transistor rectifier is verified and implemented,and the input matching circuit is jointly designed.The rectifier achieves a maximum rectifying efficiency of 27%at 91 GHz.Due to the 180°phase-shift circuit which affects the rectification efficiency,the circuit structure is improved and the current leakage switching transistor rectification structure is proposed to achieve a W-band rectifier with a maximum rectification efficiency of 45.8%.Finally,the technical advantages of the differential rectifier in the rectifier antenna array are analyzed.A pseudo-differential switching rectifier structure is proposed.The peak PCE of the rectifier reaches 35%when the input power is about 18d Bm.The three W-band rectifier chips exhibit excellent performance in terms of rectification efficiency,bandwidth,area,and input matching.They are currently one of the W-band CMOS rectifier chips with the highest rectifying efficiency in the world.(3)The design and implementation of the W-band rectifier antenna array are discussed in detail,including link budget of the wireless power transfer system,circuit structure analysis,index requirements,circuit design and circuit test,etc.The final designed W-band2×2 rectenna array achieveds a rectification efficiency of 23%and a DC output power of20m W with an incident power density of 90m W/cm~2,and the overall performance is world-leading. |
