An InP optical 90°hybrid based on a×4 MMI coupler with a deep ridged waveguide is designed and fabricated.The working principle of the 90°hybrid is systematically introduced.Three-dimensional beam ropag...An InP optical 90°hybrid based on a×4 MMI coupler with a deep ridged waveguide is designed and fabricated.The working principle of the 90°hybrid is systematically introduced.Three-dimensional beam ropagation method(3D BPM)is used to optimize the structure parameters of the 90°hybrid.The designed compact structure is demonatrated to have a low excess loss less than-0.15 dB,a high common mode rejection ratio better than 40 dB,and a low relative phase deviation less than±2.5°.The designed hybrid is manufactured on a sandwitched structure deposited on an InP substrate.The measured results show that the common mode rejection ratios are larger than 20 dB in a range from 1520 nm to 1580 nm.The phase deviations are less than±5°in a range from 1545 nm to 1560 nm and less than±7°across the C band.The designed 90°optical hybrid is suitable well for realizing miniaturization,high-properties,and high bandwidth of coherent receiver.展开更多
A control method of active front steering(AFS)based on active disturbance rejection technique was proposed for solving the model nonlinearity and parameter decoupling control in the traditional control methods.The AFS...A control method of active front steering(AFS)based on active disturbance rejection technique was proposed for solving the model nonlinearity and parameter decoupling control in the traditional control methods.The AFS controller consists of the proportional and derivative(PD)feed-forward controller and the active disturbance rejection feedback controller.To improve the steering response characteristics of a vehicle,a PD controller is designed to realize variable steering gear ratio,and to enhance the safety of vehicle when steering.An active disturbance rejection controller(ADRC)is designed to follow the expected yaw rate of the vehicle.According to the input and output of system,extended state observer(ESO)of ADRC can dynamically estimate internal and external disturbance of the system,thus easily realizing the model nonlinear and parameter decoupling control.The AFS controller is simulated and validated in Matlab and CarSim.The simulating results of double lane change(DLC)test and pylon course slalom(PCS)test show that the ADRC can well control the vehicle model to complete the road simulation test of DLC and PCS with small path tracking error.The simulating results of angle step test of steering wheel show that the vehicle under the control of ADRC demonstrates good lateral response characteristic.The controller regulates a wide range of parameters.The model has less precision requirements with good robustness.展开更多
The accuracy of the measured current is a preeminent parameter for Current Control based Power Converter applications to ensure genuine operation of the designed converter.The current measurement accuracy can be affec...The accuracy of the measured current is a preeminent parameter for Current Control based Power Converter applications to ensure genuine operation of the designed converter.The current measurement accuracy can be affected by several parameters which includes the type of technology used,components used for the selected technology,aging,usage,operating and environmental conditions.The effect of gain resistors and their manufacturing tolerances on differential amplifier-based buck converter current measurement is investigated in this work.The analysis mainly focused on the output voltage variation and its accuracy with respect to the change in gain resistance tolerances.The gain resistors with 5%,1%,0.5%and 0.1%manufacturing tolerances taken for the worst-case analysis and the calculated performance results are compared and verified with the simula-tion results.The Operational amplifiers(Op-Amp)for high frequency power con-verter applications must operate in a high frequency noise environment and the intended current measuring system must manage common mode noise distur-bances paired with the signal to be measured.Based on the Common Mode Rejec-tion Ratio(CMRR)the common mode voltages and noise signals will effectively getfiltered out.Lesser CMRR results in lower common mode signal rejection,resulting in poor precision and noise rejection.In differential amplifiers,the CMRR predominantly depends on gain resistors.So,the variations in Common Mode Rejection Ratio due to gain resistor tolerances also analyzed and compared with the output voltage variations.Besides the effects of resistor tolerances,this paper also examines the effect of Op-Amp offset voltage on output accuracy spe-cifically for low magnitude input currents.The obtained results from this analysis clearly shows that the gain resistors with 0.1%tolerance gives maximum accuracy with improved CMRR and accuracy at low magnitude input currents will get well improved by using Op-Amps with Low Offset voltage specifications.展开更多
Electrochemical reduction of CO_(2)into high-value hydrocarbons and alcohols by using Cu-based catalysts is a promising and attractive technology for CO_(2)capture and utilization,resulting from their high catalytic a...Electrochemical reduction of CO_(2)into high-value hydrocarbons and alcohols by using Cu-based catalysts is a promising and attractive technology for CO_(2)capture and utilization,resulting from their high catalytic activity and selectivity.The mobility and accessibility of active sites in Cubased catalysts significantly hinder the development of efficient Cu-based catalysts for CO_(2)electrochemical reduction reaction(CO_(2)RR).Herein,a facile and effective strategy is developed to engineer accessible and structural stable Cu sites by incorporating single atomic Cu into the nitrogen cavities of the host graphitic carbon nitride(g-C_(3)N_(4))as the active sites for CO_(2)-to-CH_(4)conversion in CO_(2)RR.By regulating the coordination and density of Cu sites in g-C_(3)N_(4),an optimal catalyst corresponding to a one Cu atom in one nitrogen cavity reaches the highest CH_(4)Faraday efficiency of 49.04%and produces the products with a high CH_(4)/C_(2)H_(4)ratio over 9.This work provides the first experimental study on g-C_(3)N_(4)-supported single Cu atom catalyst for efficient CH_(4)production from CO_(2)RR and suggests a principle in designing highly stable and selective high-efficiency Cu-based catalysts for CO_(2)RR by engineering Cu active sites in 2D materials with porous crystal structures.展开更多
设计了一种线性补偿低温漂高电源抑制比带隙基准电压源电路。带隙基准核心电路采用三支路共源共栅电流镜结构,提高电路电源抑制比。补偿电路采用分段补偿原理,在低温阶段,加入一段负温度系数电流,在高温阶段,加入一段正温度系数电流,通...设计了一种线性补偿低温漂高电源抑制比带隙基准电压源电路。带隙基准核心电路采用三支路共源共栅电流镜结构,提高电路电源抑制比。补偿电路采用分段补偿原理,在低温阶段,加入一段负温度系数电流,在高温阶段,加入一段正温度系数电流,通过补偿,使带隙基准输出电压的精确度大大提高,达到降低温度系数的目的;同时电流镜采用共源共栅结构,不仅提高电路的电源抑制比,而且可以抑制负载对镜像晶体管电压的影响。基于0.5μm CMOS工艺,使用Cadence Spectre对电路仿真,结果表明,在-50^+125℃温度范围内,基准输出电压的温度系数为2.62×10^(-6)/℃,低频时的电源抑制比(PSRR)高达88 d B。展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFB0402404)the Beijing Natural Science Foundation,China(Grant No.4194093)the National Natural Science Foundation of China(Grant Nos.61635010,61674136,and 61435002).
文摘An InP optical 90°hybrid based on a×4 MMI coupler with a deep ridged waveguide is designed and fabricated.The working principle of the 90°hybrid is systematically introduced.Three-dimensional beam ropagation method(3D BPM)is used to optimize the structure parameters of the 90°hybrid.The designed compact structure is demonatrated to have a low excess loss less than-0.15 dB,a high common mode rejection ratio better than 40 dB,and a low relative phase deviation less than±2.5°.The designed hybrid is manufactured on a sandwitched structure deposited on an InP substrate.The measured results show that the common mode rejection ratios are larger than 20 dB in a range from 1520 nm to 1580 nm.The phase deviations are less than±5°in a range from 1545 nm to 1560 nm and less than±7°across the C band.The designed 90°optical hybrid is suitable well for realizing miniaturization,high-properties,and high bandwidth of coherent receiver.
基金supported by the National Natural Science Foundation of China(No.51205191)
文摘A control method of active front steering(AFS)based on active disturbance rejection technique was proposed for solving the model nonlinearity and parameter decoupling control in the traditional control methods.The AFS controller consists of the proportional and derivative(PD)feed-forward controller and the active disturbance rejection feedback controller.To improve the steering response characteristics of a vehicle,a PD controller is designed to realize variable steering gear ratio,and to enhance the safety of vehicle when steering.An active disturbance rejection controller(ADRC)is designed to follow the expected yaw rate of the vehicle.According to the input and output of system,extended state observer(ESO)of ADRC can dynamically estimate internal and external disturbance of the system,thus easily realizing the model nonlinear and parameter decoupling control.The AFS controller is simulated and validated in Matlab and CarSim.The simulating results of double lane change(DLC)test and pylon course slalom(PCS)test show that the ADRC can well control the vehicle model to complete the road simulation test of DLC and PCS with small path tracking error.The simulating results of angle step test of steering wheel show that the vehicle under the control of ADRC demonstrates good lateral response characteristic.The controller regulates a wide range of parameters.The model has less precision requirements with good robustness.
文摘The accuracy of the measured current is a preeminent parameter for Current Control based Power Converter applications to ensure genuine operation of the designed converter.The current measurement accuracy can be affected by several parameters which includes the type of technology used,components used for the selected technology,aging,usage,operating and environmental conditions.The effect of gain resistors and their manufacturing tolerances on differential amplifier-based buck converter current measurement is investigated in this work.The analysis mainly focused on the output voltage variation and its accuracy with respect to the change in gain resistance tolerances.The gain resistors with 5%,1%,0.5%and 0.1%manufacturing tolerances taken for the worst-case analysis and the calculated performance results are compared and verified with the simula-tion results.The Operational amplifiers(Op-Amp)for high frequency power con-verter applications must operate in a high frequency noise environment and the intended current measuring system must manage common mode noise distur-bances paired with the signal to be measured.Based on the Common Mode Rejec-tion Ratio(CMRR)the common mode voltages and noise signals will effectively getfiltered out.Lesser CMRR results in lower common mode signal rejection,resulting in poor precision and noise rejection.In differential amplifiers,the CMRR predominantly depends on gain resistors.So,the variations in Common Mode Rejection Ratio due to gain resistor tolerances also analyzed and compared with the output voltage variations.Besides the effects of resistor tolerances,this paper also examines the effect of Op-Amp offset voltage on output accuracy spe-cifically for low magnitude input currents.The obtained results from this analysis clearly shows that the gain resistors with 0.1%tolerance gives maximum accuracy with improved CMRR and accuracy at low magnitude input currents will get well improved by using Op-Amps with Low Offset voltage specifications.
基金This work was supported by the Fundamental Research Funds for the Central Universities(2232021A-02 and 2232023Y-01)the National Natural Science Foundation of China(Nos.52122312,22209024 and 22202183).
文摘Electrochemical reduction of CO_(2)into high-value hydrocarbons and alcohols by using Cu-based catalysts is a promising and attractive technology for CO_(2)capture and utilization,resulting from their high catalytic activity and selectivity.The mobility and accessibility of active sites in Cubased catalysts significantly hinder the development of efficient Cu-based catalysts for CO_(2)electrochemical reduction reaction(CO_(2)RR).Herein,a facile and effective strategy is developed to engineer accessible and structural stable Cu sites by incorporating single atomic Cu into the nitrogen cavities of the host graphitic carbon nitride(g-C_(3)N_(4))as the active sites for CO_(2)-to-CH_(4)conversion in CO_(2)RR.By regulating the coordination and density of Cu sites in g-C_(3)N_(4),an optimal catalyst corresponding to a one Cu atom in one nitrogen cavity reaches the highest CH_(4)Faraday efficiency of 49.04%and produces the products with a high CH_(4)/C_(2)H_(4)ratio over 9.This work provides the first experimental study on g-C_(3)N_(4)-supported single Cu atom catalyst for efficient CH_(4)production from CO_(2)RR and suggests a principle in designing highly stable and selective high-efficiency Cu-based catalysts for CO_(2)RR by engineering Cu active sites in 2D materials with porous crystal structures.
文摘设计了一种线性补偿低温漂高电源抑制比带隙基准电压源电路。带隙基准核心电路采用三支路共源共栅电流镜结构,提高电路电源抑制比。补偿电路采用分段补偿原理,在低温阶段,加入一段负温度系数电流,在高温阶段,加入一段正温度系数电流,通过补偿,使带隙基准输出电压的精确度大大提高,达到降低温度系数的目的;同时电流镜采用共源共栅结构,不仅提高电路的电源抑制比,而且可以抑制负载对镜像晶体管电压的影响。基于0.5μm CMOS工艺,使用Cadence Spectre对电路仿真,结果表明,在-50^+125℃温度范围内,基准输出电压的温度系数为2.62×10^(-6)/℃,低频时的电源抑制比(PSRR)高达88 d B。
