Research And Design Of Broadband High Power Conversion Efficiency RF Energy Harvesting System

With the rapid development of the integrated circuit industry,the problem of chip energy supply has seriously restricted the improvement of its circuit performance in the narrow-band,Internet of things,wireless sensor networks,wearable devices and other fields.Because of its convenience,sustainability and cleanliness,radio frequency energy harvesting technology can meet the demand of self-power supply for low-power systems,which has become the key to solve the problem of energy supply.At present,the existing research of RF energy harvesting technology mainly focused on a single frequency.To accumulate more power from the weak environment source and provide more stable energy for the load,broadband RF energy acquisition technology has gradually become a more important research direction.This thesis is researched and designed a wideband RF energy harvesting system design scheme which is based on the SMIC 55nm CMOS process.The internal core circuit modules include impedance matching network,RF-DC rectifier,bandgap,low dropout regulator,etc.In this paper,the improvement of the rectifier structure in different ways is studied and analyzed based on the traditional Dickson charge pump rectifier structure.Finally,the effective conduction voltage of the diode-connected transistor is minimized by the CMOS bridge differential rectifier circuit,and the cross-coupling structure is used to provide a bias for the circuit,thereby obtaining a higher energy conversion efficiency.The post-simulation results show that when the input power is 0d Bm and the frequency is 953MHz,the PCE can reach 69.8%,and the settling time is about 1μs.Secondly,this thesis introduces auxiliary circuit,cascode current mirror and RC filter structure to enhance the PSRR of the circuit on the basis of the traditional bandgap reference structure.Adding a unit gain buffer guaranteed that the output voltage does not change with the load.At the same time,the design of the start-up circuit enables the bandgap reference to consume less static power.The post-simulation results show that the bandgap can output a reference voltage of 1.18V within 1μs,with a ripple voltage of 6m V,the temperature coefficient is less than 10.8ppm/℃,the power supply rejection ratio is better than 70d B at low frequencies,up to 120d B at high frequencies,and the quiescent current is 11.02μA.Next,the basic principles and performance of the LDO are introduced in detail.This thesis focuses on the stability and improvement methods of the LDO.Then a flipped voltage follower LDO structure is proposed,which uses a dynamic bias circuit to achieve a fast transient response,adding miller compensation capacitor C_m to maintain loop stability,and adding a capacitor between the gate and source of the power tube to improve the PSRR of the loop.A high pass filter is added between the output and the dynamic bias circuit to prevent the voltage fluctuation at the output from being transmitted to the dynamic bias circuit module.The post-simulation results show that the output voltage is stable at about 1.16V,the quiescent current is 6u A,the ripple is less than 1.6m V,and the maximum load current can reach 1.3m A.Finally,this work finish simulation optimization layout design of the system through iterative design.The overall post-simulation results show that the RF energy harvesting system receives a 0 d Bm and 953 MHz radio frequency signal,and the output voltage is stable at about 7μs,with a ripple voltage of 0.22 m V.The system can provide 316μA current for the load,the rectifier power conversion efficiency is 69.8%,and the power conversion efficiency of the system can reach 36.9%.The overall power conversion efficiency can be maintained at 36.3%～38%in the frequency range of 800MHz～2500MHz,and the overall system performance is good.