A designed visual geometry group(VGG)-based convolutional neural network(CNN)model with small computational cost and high accuracy is utilized to monitor pulse amplitude modulation-based intensity modulation and direc...A designed visual geometry group(VGG)-based convolutional neural network(CNN)model with small computational cost and high accuracy is utilized to monitor pulse amplitude modulation-based intensity modulation and direct detection channel performance using eye diagram measurements.Experimental results show that the proposed technique can achieve a high accuracy in jointly monitoring modulation format,probabilistic shaping,roll-off factor,baud rate,optical signal-to-noise ratio,and chromatic dispersion.The designed VGG-based CNN model outperforms the other four traditional machine-learning methods in different scenarios.Furthermore,the multitask learning model combined with MobileNet CNN is designed to improve the flexibility of the network.Compared with the designed VGG-based CNN,the MobileNet-based MTL does not need to train all the classes,and it can simultaneously monitor single parameter or multiple parameters without sacrificing accuracy,indicating great potential in various monitoring scenarios.展开更多
In this paper,a novel pulse density modulation(PDM)with semi-bridgeless active rectifier(S-BAR)in inductive power transfer(IPT)system for rail vehicle is proposed.It is to reduce switching losses of the active rectifi...In this paper,a novel pulse density modulation(PDM)with semi-bridgeless active rectifier(S-BAR)in inductive power transfer(IPT)system for rail vehicle is proposed.It is to reduce switching losses of the active rectifier in pickups.In the control method,the insulated-gate bipolar transistors(IGBTs)in the S-BAR are controlled by synchronous PDM signals,so that zero-voltage switching(ZVS)and zero-current switching(ZCS)can be achieved in the whole output power range.The output power is regulated by changing the pulse density(PD)of the S-BAR since the it is almost linear proportional with the PD in high quality factor of pickup side.The communication device between the primary side and pickup side is not necessary anymore.The detailed theoretical analyses of the PDM method are provided,and its advantages are shown in a 7.5kW IPT prototype for rail vehicle.The experimental results are presented to verify the analysis and demonstrate the performance.The overall efficiency of the system by PDM control is 74.2%which is improved by 4%compared with phase shift(PS)control at light load.展开更多
Since the poor performance of orthogonal binary Pulse Position Modulation (PPM) compared with binary Pulse Amplitude Modulation (PAM), this paper presents a new modulation scheme named Pulse Width Modulation (PWM) for...Since the poor performance of orthogonal binary Pulse Position Modulation (PPM) compared with binary Pulse Amplitude Modulation (PAM), this paper presents a new modulation scheme named Pulse Width Modulation (PWM) for Impulse Radio Ultra-WideBand (IR-UWB) communication systems. This modulation scheme uses pulses with equal amplitude and different widths to carry different information. The receiver employs differences between similarity coefficients among these pulses to distinguish different information. Both theoretical analysis and simulation results verify that this novel scheme has a Signal to Noise Ratio (SNR) gain of about 1.75 dB compared with or- thogonal binary PPM, and has an SNR loss of about 1.4 dB compared with binary PAM. Although both the theoretical analysis and simulations are based on time-hopping multiple access, this modulation scheme can also be applied to other accessing techniques of UWB communication systems.展开更多
为解决传统调幅发射机在效率与线性度方面的技术瓶颈,设计一种基于数字信号处理的脉冲密度调制(Pulse Density Modulation,PDM)调幅发射机驱动控制系统。系统包括信号处理、调制与编码、功率驱动、控制与校准及保护与监测5个功能层,采...为解决传统调幅发射机在效率与线性度方面的技术瓶颈,设计一种基于数字信号处理的脉冲密度调制(Pulse Density Modulation,PDM)调幅发射机驱动控制系统。系统包括信号处理、调制与编码、功率驱动、控制与校准及保护与监测5个功能层,采用二阶Σ-Δ调制与噪声整形生成PDM码流,经全桥功率放大与优化的电感-电容(Inductance Capacitance,LC)滤波器驱动射频末级。引入双反馈闭环控制、时序对齐与预失真补偿提升包络精度,并在保护与监测层设置多种快速响应机制。验证结果表明,该系统能够在不同工况下保持高效、稳定的运行状态,具备较高的工程适配性与推广价值。展开更多
介绍了脉冲密度调功(Pulse Density Modulation,简称PDM)的原理,由于PDM在品质因数较小时,负载电流波动很大,因此采用均匀PDM方法进行改进,推导出品质因数与谐振周期数的关系。通过给定品质因数,可以很方便地计算出一个工作周期内的最...介绍了脉冲密度调功(Pulse Density Modulation,简称PDM)的原理,由于PDM在品质因数较小时,负载电流波动很大,因此采用均匀PDM方法进行改进,推导出品质因数与谐振周期数的关系。通过给定品质因数,可以很方便地计算出一个工作周期内的最小脉冲密度,从而避免过小的电流流过负载,使负载电流连续,保证对负载谐振频率进行可靠跟踪。经过仿真和试验验证了该分析的正确性。展开更多
针对多电平移相全数字发信机(All Digital Transmitter,ADTx)架构中脉冲波形幅度不平衡误差问题,开展了误差机理分析和数值仿真研究。提出了一个基于ADTx硬件电路不理想性引起的脉冲幅度不平衡误差非线性失真模型,并推导分析了脉冲幅度...针对多电平移相全数字发信机(All Digital Transmitter,ADTx)架构中脉冲波形幅度不平衡误差问题,开展了误差机理分析和数值仿真研究。提出了一个基于ADTx硬件电路不理想性引起的脉冲幅度不平衡误差非线性失真模型,并推导分析了脉冲幅度不平衡误差对输出信号时域波形的畸变机制。通过数值仿真研究了脉冲幅度不平衡误差对发信机线性性能的影响。实验结果表明,脉冲幅度不平衡误差会显著恶化误差矢量幅度(Error Vector Magnitude,EVM)、邻信道功率比(Adjacent Channel Power Ratio,ACPR)以及三次谐波抑制性能等关键性能指标。深入分析该幅度不平衡误差对于准确评估并消除误差、提升多电平ADTx系统性能具有重要的理论和实践意义。展开更多
研究了基于脉冲密度调制(Pulse Density Modulation)控制策略的串联谐振逆变电晕处理电源。PDM的基本思想是在一定的调功周期内使交流输出端产生方波电压或者是零电平电压,这样即使电晕放电负载具有很强的非线性也可以宽范围内控制功率...研究了基于脉冲密度调制(Pulse Density Modulation)控制策略的串联谐振逆变电晕处理电源。PDM的基本思想是在一定的调功周期内使交流输出端产生方波电压或者是零电平电压,这样即使电晕放电负载具有很强的非线性也可以宽范围内控制功率输出。对于该电晕处理电源进行了仿真与实验,所得结果验证了理论分析。展开更多
基金supported by the National Key Research and Development Program of China (Grant No.2019YFB1803700)the Key Technologies Research and Development Program of Tianjin (Grant No.20YFZCGX00440).
文摘A designed visual geometry group(VGG)-based convolutional neural network(CNN)model with small computational cost and high accuracy is utilized to monitor pulse amplitude modulation-based intensity modulation and direct detection channel performance using eye diagram measurements.Experimental results show that the proposed technique can achieve a high accuracy in jointly monitoring modulation format,probabilistic shaping,roll-off factor,baud rate,optical signal-to-noise ratio,and chromatic dispersion.The designed VGG-based CNN model outperforms the other four traditional machine-learning methods in different scenarios.Furthermore,the multitask learning model combined with MobileNet CNN is designed to improve the flexibility of the network.Compared with the designed VGG-based CNN,the MobileNet-based MTL does not need to train all the classes,and it can simultaneously monitor single parameter or multiple parameters without sacrificing accuracy,indicating great potential in various monitoring scenarios.
文摘In this paper,a novel pulse density modulation(PDM)with semi-bridgeless active rectifier(S-BAR)in inductive power transfer(IPT)system for rail vehicle is proposed.It is to reduce switching losses of the active rectifier in pickups.In the control method,the insulated-gate bipolar transistors(IGBTs)in the S-BAR are controlled by synchronous PDM signals,so that zero-voltage switching(ZVS)and zero-current switching(ZCS)can be achieved in the whole output power range.The output power is regulated by changing the pulse density(PD)of the S-BAR since the it is almost linear proportional with the PD in high quality factor of pickup side.The communication device between the primary side and pickup side is not necessary anymore.The detailed theoretical analyses of the PDM method are provided,and its advantages are shown in a 7.5kW IPT prototype for rail vehicle.The experimental results are presented to verify the analysis and demonstrate the performance.The overall efficiency of the system by PDM control is 74.2%which is improved by 4%compared with phase shift(PS)control at light load.
文摘Since the poor performance of orthogonal binary Pulse Position Modulation (PPM) compared with binary Pulse Amplitude Modulation (PAM), this paper presents a new modulation scheme named Pulse Width Modulation (PWM) for Impulse Radio Ultra-WideBand (IR-UWB) communication systems. This modulation scheme uses pulses with equal amplitude and different widths to carry different information. The receiver employs differences between similarity coefficients among these pulses to distinguish different information. Both theoretical analysis and simulation results verify that this novel scheme has a Signal to Noise Ratio (SNR) gain of about 1.75 dB compared with or- thogonal binary PPM, and has an SNR loss of about 1.4 dB compared with binary PAM. Although both the theoretical analysis and simulations are based on time-hopping multiple access, this modulation scheme can also be applied to other accessing techniques of UWB communication systems.
文摘为解决传统调幅发射机在效率与线性度方面的技术瓶颈,设计一种基于数字信号处理的脉冲密度调制(Pulse Density Modulation,PDM)调幅发射机驱动控制系统。系统包括信号处理、调制与编码、功率驱动、控制与校准及保护与监测5个功能层,采用二阶Σ-Δ调制与噪声整形生成PDM码流,经全桥功率放大与优化的电感-电容(Inductance Capacitance,LC)滤波器驱动射频末级。引入双反馈闭环控制、时序对齐与预失真补偿提升包络精度,并在保护与监测层设置多种快速响应机制。验证结果表明,该系统能够在不同工况下保持高效、稳定的运行状态,具备较高的工程适配性与推广价值。
文摘介绍了脉冲密度调功(Pulse Density Modulation,简称PDM)的原理,由于PDM在品质因数较小时,负载电流波动很大,因此采用均匀PDM方法进行改进,推导出品质因数与谐振周期数的关系。通过给定品质因数,可以很方便地计算出一个工作周期内的最小脉冲密度,从而避免过小的电流流过负载,使负载电流连续,保证对负载谐振频率进行可靠跟踪。经过仿真和试验验证了该分析的正确性。
文摘针对多电平移相全数字发信机(All Digital Transmitter,ADTx)架构中脉冲波形幅度不平衡误差问题,开展了误差机理分析和数值仿真研究。提出了一个基于ADTx硬件电路不理想性引起的脉冲幅度不平衡误差非线性失真模型,并推导分析了脉冲幅度不平衡误差对输出信号时域波形的畸变机制。通过数值仿真研究了脉冲幅度不平衡误差对发信机线性性能的影响。实验结果表明,脉冲幅度不平衡误差会显著恶化误差矢量幅度(Error Vector Magnitude,EVM)、邻信道功率比(Adjacent Channel Power Ratio,ACPR)以及三次谐波抑制性能等关键性能指标。深入分析该幅度不平衡误差对于准确评估并消除误差、提升多电平ADTx系统性能具有重要的理论和实践意义。
文摘研究了基于脉冲密度调制(Pulse Density Modulation)控制策略的串联谐振逆变电晕处理电源。PDM的基本思想是在一定的调功周期内使交流输出端产生方波电压或者是零电平电压,这样即使电晕放电负载具有很强的非线性也可以宽范围内控制功率输出。对于该电晕处理电源进行了仿真与实验,所得结果验证了理论分析。
