Code synchronization based on lumped time-delay compensation scheme with a linearly chirped fiber Bragg grating in all-optical analog-to-digital conversion

We propose a novel lumped time-delay compensation scheme for all-optical analog-to-digital conversion based on soliton self-frequency shift and optical interconnection techniques. A linearly chirped fiber Bragg grating is optimally designed and used to compensate for the entire time-delays of the quantized pulses precisely. Simulation results show that the compensated coding pulses are well synchronized with a time difference less than 3.3 ps, which can support a maximum sampling rate of 151.52 GSa/s. The proposed scheme can efficiently reduce the structure complexity and cost of all-optical analog-to-digital conversion compared to the previous schemes with multiple optical time-delay lines.

A convenient look-up-table based method for the compensation of non-linear error in digital fringe projection

Although the structured light system that uses digital fringe projection has been widely implemented in three-dimensional surface profile measurement, the measurement system is susceptible to non-linear error. In this work, we propose a convenient look-up-table-based （LUT-based） method to compensate for the non-linear error in captured fringe patterns. Without extra calibration, this LUT-based method completely utilizes the captured fringe pattern by recording the full-field differences. Then, a phase compensation map is established to revise the measured phase. Experimental results demonstrate that this method works effectively.

A Method for Identification and Compensation of Machining Errors of Digital Gear Tooth Surfaces

In order to generate the digital gear tooth surfaces(DGTS)with high efficiency and high precision,a method for identification and compensation of machining errors is demonstrated in this paper.Machining errors are analyzed directly from the real tooth surfaces.The topography data of the part are off-line measured in the post-process.A comparison is made between two models:CAD model of DGTS and virtual model of the physical measured surface.And a matching rule is given to determine these two surfaces in an appropriate fashion.The developed error estimation model creates a point-to-point map of the real surface to the theoretical surface in the normal direction.A“pre-calibration error compensation”strategy is presented.Through processing the results of the first trail cutting,the total compensation error is predicted and an imaginary digital tooth surface is reconstructed. The machining errors in the final manufactured surfaces are minimized by generating this imaginary surface.An example of ma- chining 2-D DGTS verifies the developed method.The research is of important theoretical and practical value to manufacture the DGTS and other digital conjugate surfaces.

SPLIT-ADC BASED DIGITAL BACKGROUND CALIBRATION FOR TIME-INTERLEAVED ADC

A novel Time-Interleaved Analog-to-Digital Converter (TIADC) digital background calibration for the mismatches of offsets, gain errors, and timing skews based on split-ADC is proposed. Firstly, the split-ADC channels in present TIADC architecture are designed to convert input signal at two different channel sampling rates so that redundant channel to facilitate pair permutation is avoided. Secondly, a high-order compensation scheme for correction of timing skew error is employed for effective calibration to preserve high-resolution when input frequency is high. Numerical simulation performed by MATLAB for a 14-bit TIADC based on 7 split-ADC channels shows that Signal-to-Noise and Distortion Ratio (SNDR) and Spurious Free Dynamic Range (SFDR) of the TIADC achieve 86.2 dBc and 106 dBc respectively after calibration with normalized input frequency near Nyquist frequency.

A multi-channel real-time digital integrator for magnetic diagnostics in HL-2A tokamak

A novel full-digital integrator has been developed for the magnetic diagnostics in HL-2A. Based on the pipeline processing of the field-programmable gate array and high-speed PCI extensions for instrumentation platform, the digital integrator has realized octal-channel10-k Hz real-time integration and data transmission. In order to reduce the integration drift, a 24-bit analog-todigital converter and simple analog processing circuits are applied for high-precision sampling, while certain correction algorithms are used to minimize the drift. With simple and highly integrated circuits and high-performance digital processor, the digital integrator is of high stability and functional expansibility which greatly simplifies the operation procedure. The digital integrator has been tested in the plasma discharge experiments, and the experimental results have confirmed that the drift performance and accuracy of the digital integrator could fully meet the requirements of HL-2A.

Digital close loop control system for current-programmed mode arc welding inverter

A small-signal model of current programmed mode pulse width modulation converter including the equivalent sampling effect is introduced and analyzed. In this model, an addition pole is brought out by the sampling effect in the current loop gain, and it affects dynamic bandwidth and stability of the inner current loop. By selecting the appropriate stability parameter which determines the additional pole and describes the degree of peaking in closed loop transfer function, a control model of current programmed full bridge arc welding inverter with maximum frequency bandwidth and stability can be obtained. Small and large amplitude pulse current outputs are employed in simulations and experiments and results validate the design method.

Lag compensation errors in active power filters based on DSP controllers

The growing problems of harmonic pollution on coal mine power lines caused by high-power DC drive systems has increased the use of active power filters.We analyzed compensation errors caused by the time lag in the detecting circuits of an active power filter based on DSP control.We derived a mathematical model for the compensation error starting from the error estimation when a single distortion frequency is present.This model was then extended to the case where multiple frequencies are present in the distortion.A formula for a general theory of compensation error with fixed load and fixed lag time is presented.The theoretical analysis and experimental results show that the delay time of an active power filter mainly arises from the sampling time.Lower sampling frequencies introduce larger compensation errors in the active power filter reference current.

DYNAMIC COMPENSATION OF MEASURING SYSTEMS BY SYSTEM IDENTIFICATION APPROACH

A digital filtering method is presented to compensate the dynamic characteristics of measuring systems.The compensation filter has an infinite impulse response property and is designed by system identification approach from the known input output pairs of the measuring system.Applications of this method to eliminating the distortions of measured waveform in transient pulse measurement are investigated.Experimental results show that the measurement errors caused by the sensor are reduced to be very small after the use of the compensation filter.

Computationally Efficient Nonlinearity Compensation for Coherent Fiber-Optic Systems

Split-step digital backward propagation （DBP） can be combined with coherent detection to compensate for fiber nonlinear impairments. A large number of DBP steps is usually needed for a long-haul fiber system, and this creates a heavy computational load. In a trade-off between complexity and performance, interchannel nonlinearity can be disregarded in order to simplify the DBP algorithm. The number of steps can also be reduced at the expense of performance. In periodic dispersion-managed long-haul transmission systems, optical waveform distortion is dominated by chromatic dispersion. As a result, the nonlinearity of the optical signal repeats in every dispersion period. Because of this periodic behavior, DBP of many fiber spans can be folded into one span. Using this distance-folded DBP method, the required computation for a transoceanic transmission system with full inline dispersion compensation can be reduced by up to two orders of magnitude with negligible penalty. The folded DBP method can be modified to compensate for nonlinearity in fiber links with non-zero residua dispersion per span.

An Adaptive Response Compensation Technique for the Constant-Current Hot-Wire Anemometer

An adaptive response compensation technique has been proposed to compensate for the response lag of the constant-current hot-wire anemometer (CCA) by taking advantage of digital signal processing technology. First, we have developed a simple response compensation scheme based on a precise theoretical expression for the frequency response of the CCA (Kaifuku et al. 2010, 2011), and verified its effectiveness experimentally for hot-wires of 5 μm, 10 μm and 20 μm in diameter. Then, another novel technique based on a two-sensor probe technique—originally developed for the response compensation of fine-wire thermocouples (Tagawa and Ohta 1997;Tagawa et al. 1998)—has been proposed for estimating thermal time-constants of hot-wires to realize the in-situ response compensation of the CCA. To demonstrate the usefulness of the CCA, we have applied the response compensation schemes to multipoint velocity measure- ment of a turbulent wake flow formed behind a circular cylinder by using a CCA probe consisting of 16 hot-wires, which were driven simultaneously by a very simple constant-current circuit. As a result, the proposed response compensation techniques for the CCA work quite successfully and are capable of improving the response speed of the CCA to obtain reliable measurements comparable to those by the commercially-available constant-temperature hot-wire anemometer (CTA).

基于大创项目的应用技术开发实践——以数字电源教具设计为例

针对教学环节中的难点和重点内容,基于dsPIC33CK256MP505数字信号控制器芯片,为开发新型的数字电源教具,在降压转换器的电路拓扑结构基础上,利用MplabPowerSmart开发软件,完成了电压控制型数字环路补偿器的设计,实现3P3Z数字补偿器的实时算法功能。

一种集成图像处理功能的数字像元焦平面读出电路

设计了一种像元级数字化焦平面读出电路,克服了传统模拟读出电路技术的电荷容量局限,实现了更大的动态范围和更低噪声的数字化图像读出;同时在像元内部进行数字化图像处理,可实现非均匀校正(NUC)、盲元补偿、数字时间延迟积分(TDI)、空间滤波等图像预处理功能。该电路采用40 nm CMOS工艺流片,面阵规格为640×512,像元步进为30μm,全芯片尺寸约22 mm×19 mm。测试结果显示,该电路通过TDI、空间滤波功能可大幅降低(分别约90%和63%)输出图像空间噪声,提升成像质量。

数字借阅补偿金制度及其对我国的启示

公共借阅权有排他权、获酬权和补偿金三种实施模式,其中补偿金模式是当前各国的主流选择。数字时代,很多国家开始探索将公共借阅权拓展至数字领域,澳大利亚、加拿大、英国和丹麦四国均已建立起数字借阅补偿金制度。这一制度符合功利主义社会整体利益最大化的理念。在目前制度实践的基础上,本文总结了数字借阅补偿金的运行机制,主要体现在受益者范围、借阅模式、报酬支付和管理体系四个方面。我国应当引入数字借阅补偿金制度,以激励文化创新,促进知识传播,从而实现社会利益最大化。

一种不同时钟信号的全温相位同步补偿方法

信号同步技术是相控阵雷达数字收发组件的关键技术,针对数字收发组件中多通道同步时钟在高低温下相位变化不满足同步要求的问题,本文研究了一种能够在高低温下自动补偿时钟信号相位同步的方法,无需实时控制补偿值,电路布局简单,经过批量生产检验,效果显著,具有广泛推广应用价值。

基于数字温度传感器的热电偶冷端补偿研究

介绍热电偶的工作原理和冷端温度补偿,对比分析不同数字温度传感器的工作原理和特点,提出基于数字温度传感器实现热电偶冷端补偿的方法,解决了热电偶测温存在冷端温度变化大、测量数据非线性难处理、测量信号微弱及数字化输出须转换等问题,提高了测量准确度,简化了温度补偿电路。

基于量子电压的模数转换器性能评估

相比于用传统半导体器件研制的信号源,约瑟夫森任意波形发生器合成信号的幅值可溯源至自然常数,其输出波形具有超低噪声、超低失真的优点。使用约瑟夫森任意波形发生器评估了National Instruments公司24位数字采集卡PXI 5922的性能。其中,采用零补偿波形合成方法简化系统硬件结构,并且使用高精度、多比例的感应分压器提升评估效率。首先,在10 kHz的带宽内标定了PXI 5922单通道的增益及其稳定性、信噪比、无杂散动态范围、总谐波失真、信纳比和有效位数;其次,标定了PXI 5922两通道不同相位下的相位差;最后,结合电网的谐波情况,以60 Hz的基波频率为例,标定了PXI 5922在12阶谐波以内各谐波的幅度与相位响应。约瑟夫森任意波形发生器的超高精度和宽带输出能力在评估高精度模数转换器的性能方面具有广阔的应用前景。

采用两步式数字校准的低温漂松弛振荡器

针对传统片上振荡器设计面临的时钟频率难以实现高精度校准的问题,提出基于二分搜索法的数字校准方法,实现了振荡频率校准并提高了校准的线性度。校准算法采用了粗校准加细校准的两步式校准过程,大大增加了频率校准范围。针对振荡频率的温度漂移问题,提出了新的温度补偿方案,在传统一阶温度补偿的基础上,增加了亚阈值电流自补偿的高阶补偿机制,大大降低了温度变化对输出频率的影响。在校准电路的设计中,合理设置开关电阻阵列的温度系数以保证输出频率的校准不影响输出频率的温度稳定性。对振荡器版图提取了寄生参数,并进行了仿真,仿真结果表明:经过所提频率校准和温度补偿方案,典型情况下振荡频率误差小于0.04%;在-40~125℃温度范围内频率误差小于±0.12%;2.5~5.5 V电源电压范围内频率随电源电压变化误差小于±0.13%;电路工作电流为47.6μA,完成一次校准时长不超过2.7 ms。该振荡器可用于物联网、处理器等应用,可以取代片外晶体振荡器,能够降低系统成本和体积。

带有死区时间补偿及电容电压平衡功能的二极管钳位型三电平逆变器数字调制方法

针对二极管钳位型三电平逆变器存在的电容电压平衡问题和死区时间导致的输出波形失真问题,该文在分析死区时间对输出波形失真及电容电压平衡影响的基础上,提出一种可用于高频逆变器的数字调制方法及具体实现形式,分析量化与采样环节、数字隔离器件传输延时及采样时钟对所提方法的影响,并给出开关时钟分频倍数的设计准则。该方法独立于闭环控制系统其他环节,无需电流采样,实现容易且易于集成在数字控制器中;无需控制环路运算,可适用于更高开关频率和输出频率。仿真和实验表明,所提方法在不同开关频率、不同死区时间和不同负载类型下均能有效地降低死区时间导致的输出波形失真现象,且能够很好地解决电容电压平衡问题。此外,所提方法在开关频率高达400 kHz的情况下仍具有良好的效果。

工业企业数字化转型抑制了“去工业化”吗?——兼论其结构性减速补偿效应

随着数字经济快速发展,企业数字化转型为企业发展带来了新的发展潜能,这能否成为应对“去工业化”的有效手段并对其导致的结构性减速形成补偿效应,则有待考察。本文将企业数字化转型和“去工业化”纳入统一分析框架,基于2011—2019年中国沪深A股工业上市公司数据,实证检验工业企业数字化转型对“去工业化”的影响及作用机制,并考察结构性减速补偿效应。研究发现:企业数字化转型显著抑制了“去工业化”,并呈现一定的企业属性和城市层级异质性特征,企业数字化转型主要通过降低企业营业成本和促进企业技术创新,发挥对“去工业化”的抑制效果。进一步研究发现,“去工业化”对经济增长呈现显著的结构性减速影响,企业数字化转型则在这一影响中发挥结构性减速补偿效应。

Primary frequency control considering communication delay for grid-connected offshore wind power systems

Offshore wind farms are becoming increasingly distant from onshore centralized control centers,and the communication delays between them inevitably introduce time delays in the measurement signal of the primary frequency control.This causes a deterioration in the performance of the primary frequency control and,in some cases,may even result in frequency instability within the power system.Therefore,a frequency response model that incorporates communication delays was established for power systems that integrate offshore wind power.The Padéapproximation was used to model the time delays,and a linearized frequency response model of the power system was derived to investigate the frequency stability under different time delays.The influences of the wind power proportion and frequency control parameters on the system frequency stability were explored.In addition,a Smith delay compensation control strategy was devised to mitigate the effects of communication delays on the system frequency dynamics.Finally,a power system incorporating offshore wind power was constructed using the MATLAB/Simulink platform.The simulation results demonstrate the effectiveness and robustness of the proposed delay compensation control strategy.