Photon-timing detector module for single-molecule spectroscopy with 60-ps resolution

Advanced fluorescence measurements on single molecules demand single-photon detectors with high-quantum detection efficiency, low noise, and high time resolution. We have developed a compact (82/spl times/60/spl times/30 mm) and versatile single-photon timing module (SPTM), based on a planar epitaxial single photon avalanche diodes (SPAD) working with a monolithic integrated active quenching and active reset circuit (i-AQC) and cooled by a Peltier element. The main operating parameters are computer controlled via RS-232 interface and the photon counting rate can be continuously monitored. The photon detection efficiency is 45% at 500 nm with cooling at -15/spl deg/C, the dark counting rate is 5 c/s with SPAD operating at 5 V excess bias voltage, 10c/s operating at 10 V. The time resolution obtained with tightly focused illumination has 60-ps full-width at half-maximum. Comparative tests with the SPTM prototype and with an advanced commercially available photon counting module confirmed that the time resolution and sensitivity of the SPTM make it possible to resolve and measure even short lifetime components of a single molecule. The SPTM thus made possible experiments leading to a deeper insight into angstrom-scale structural changes of single-protein molecules.     

基于DDS芯片AD9852的正弦信号发生器及其在通信中的应用

本文所设计的正弦信号发生器主要由DDS 波形产生模块、单片机控制模块、键盘输入模块和数码管显示模块组成.用户可通过键盘输入所需数据,利用AT89C51单片机对输入的数据进行处理,执行相应的控制指令,还可对直接数字频率合成(DDS)芯片AD9852进行编程,不仅可以产生1 kHz～10 MHz的单频正弦波(经示波器观察无明显失真),同时还可以利用单片机进行控制,根据要求产生模拟幅度调制(AM)信号、模拟频率调制(FM)信号、二进制相移键控(BPSK)信号、二进制幅移键控(BASK)信号等.为方便输入和控制,显示模块实时显示键盘输入数据和系统状态.经测试,DDS输出信号的峰峰值最大可达1.02 V.     

VXI总线高速大容量数据采集模块

根据某舰空导弹自动测试系统的要求,设计了基于VXI总线的4通道高速数据采集模块.它以同步动态随机存储器(SDRAM)为数据缓冲单元,用现场可编程门阵列(FPGA)实现控制和与VXI总线的接口.控制程序采用自顶向下的模块化设计方法,用VHDL实现电路行为的描述.采用状态机(FSM)控制整个流程,实现了各路控制信号的可靠同步.针对SDRAM控制复杂的特点,设计了基于FPGA的SDRAM控制器.驱动程序和应用程序用LabWindows/CVI写.测试结果表明,模块的采样频率可达200 Msps,有效位数为7.76位,达到了预期的指标.     

VXI总线高速大容量数据采集模块

本文根据某舰空导弹自动测试系统的要求,设计了基于VXI总线的4通道高速数据采集模块.它以SDRAM为数据缓冲单元,用FPGA实现控制和与VXI总线的接口.控制程序采用自顶向下的模块化设计方法,用VHDL实现电路行为的描述.采用状态机(FSM)控制整个流程,实现了各路控制信号的可靠同步.针对SDRAM控制复杂的特点,设计了基于FPGA的SDRAM控制器.驱动程序和应用程序用LabWindows/CVI编写.测试结果表明,模块的采样频率可达200 MHz,有效位数为7.76位,达到了预期的指标.     

Toward a 3-D camera based on single photon avalanche diodes

A three-dimensional (3-D) imager is presented, capable of computing the depth map as well as the intensity scale of a given scene. The heart of the system is a two-dimensional array of single photon avalanche diodes fabricated in standard CMOS technology. The diodes exhibit low-noise equivalent-power high-dynamic range, and superior linearity. The 3-D imager achieves submillimetric precision at a depth-of-field of a few meters. This precision was achieved by averaging over 10 000 measurements. The imager operates using a standard laser source pulsed at 50 MHz with 40-mW peak power and requires no mechanical scanning mechanisms or expensive optical equipment.     

高频电磁涡流检测系统及实验研究

针对碳纤维复合材料电磁涡流检测的特点,自主设计研制了一套高频电磁涡流检测系统,其最高检测频率可以达到10 MHz以上。该系统下位机以高速ARM微控制器STM32F407VGT6芯片为控制核心,上位机以虚拟仪器软件LabVIEW设计用户界面。系统集成了信号发生模块、功率放大模块、可调增益放大模块、锁相放大模块、USB模块以及数据采集模块,集成度高、体积小、使用简单方便。利用制作的高频电磁涡流检测系统对碳纤维复合材料的常见损伤形式进行了检测,包括冲击以及分层等,证明了系统的可行性以及实用性。     

基于MSP430的锁相环控制系统设计

给出了一种基于MSP430单片机,通过按键控制对高频信号进行数据采集和液晶显示,实现采集显示的系统。该系统以MSP430单片机为核心,由自动控制模块、待测信号锁相环路模块、按键控制模块、信号采集及数据显示模块几部分组成。从实验结果来看,该系统能够控制产生稳定的高频信号、完成从950 MHz~2.15 GHz频率的扫频、信号自动采集以及显示屏上对数据的实时显示,具有很好的市场应用前景,也具有很高的兼容性。该测试系统搭建简单方便、具有精度高、性能稳定、价格低廉等特点。     

几何变换单元的设计及其FPGA实现

随着计算机绘图规模的需要,借助辅助硬件资源,来提高图形处理单元(GPU)处理速度的需求越来越普遍.结合计算机绘图及FPGA的特点,本文采用Top-Down的方法对GPU几何变换单元部分进行了FPGA设计实现.所有结构模块均实现了RTL级建模,并对其中较复杂的矩阵构造单元和矩阵乘法器模块给出了详细的描述.最后借助电子设计自动化工具(EDA)对整个模块进行了验证综合,结果表明,符合设计需求,该方案能很好地完成几何变换功能,资源耗费低,最高工作频率可达120 MHz.     

基于CPCI总线的多DSP处理模块的设计及实现

超高压直流输电控制保护系统硬件平台的开发,目前面临着巨大的挑战,主要表现在:直流输电测控点多,数据运算量大,系统规模和复杂度不断增加,单CPU的运行已很难胜任工作。结合灵宝、贵广二回工程,在深入分析超高压直流输电控制保护系统的发展和现状,参考其他领域特别是通信和计算机技术发展的基础上,开发了一种实用于超高压直流系统的新型DSP模块。该模块采用64位,66MHz的CPCI总线作为外部总线接口,标准的6U板型,8片DSP芯片TS201S构成多DSP并行处理结构,具有实时运算能力强、接口灵活、可扩展性和通用性强等特点。经过测试和现场应用,各项技术指标良好,运行稳定可靠,能够满足超高压直流输电的应用。     

Single-Photon Detection System for Quantum Optics Applications

We describe the design and characterization of a fiber-coupled double-channel single-photon detection system based on superconducting single-photon detectors (SSPD), and its application for quantum optics experiments on semiconductor nanostructures. When operated at 2-K temperature, the system shows 10% quantum efficiency at 1.3-mum wavelength with dark count rate below 10 counts per second and timing resolution <100 ps. The short recovery time and absence of afterpulsing leads to counting frequencies as high as 40 MHz. Moreover, the low dark count rate allows operation in continuous mode (without gating). These characteristics are very attractive-as compared to InGaAs avalanche photodiodes-for quantum optics experiments at telecommunication wavelengths. We demonstrate the use of the system in time-correlated fluorescence spectroscopy of quantum wells and in the measurement of the intensity correlation function of light emitted by semiconductor quantum dots at 1300 nm.     

Compact CMOS active quenching/recharge circuit for SPAD arrays

Avalanche diodes operating in Geiger mode are able to detect single photon events. They can be employed to photon counting and time‐of‐flight estimation. In order to ensure proper operation of these devices, the avalanche current must be rapidly quenched, and, later on, the initial equilibrium must be restored. In this paper, we present an active quenching/recharge circuit specially designed to be integrated in the form of an array of single‐photon avalanche diode (SPAD) detectors. Active quenching and recharge provide benefits like an accurately controllable pulse width and afterpulsing reduction. In addition, this circuit yields one of the lowest reported area occupations and power consumptions. The quenching mechanism employed is based on a positive feedback loop that accelerates quenching right after sensing the avalanche current. We have employed a current starved inverter for the regulation of the hold‐off time, which is more compact than other reported controllable delay implementations. This circuit has been fabricated in a standard 0.18 µm complementary metal‐oxide‐semiconductor (CMOS) technology. The SPAD has a quasi‐circular shape of 12 µm diameter active area. The fill factor is about 11%. The measured time resolution of the detector is 187 ps. The photon‐detection efficiency (PDE) at 540 nm wavelength is about 5% at an excess voltage of 900 mV. The break‐down voltage is 10.3 V. A dark count rate of 19 kHz is measured at room temperature. Worst case post‐layout simulations show a 117 ps quenching and 280 ps restoring times. The dead time can be accurately tuned from 5 to 500 ns. The pulse‐width jitter is below 1.8 ns when dead time is set to 40 ns. Copyright © 2015 John Wiley & Sons, Ltd.     

超声显微测量系统的信号激励接收方法研究

超声显微测量技术是一种广泛应用于工业、航空航天、医疗等领域的无损检测方法。为了减小对100 MHz以上高频超声激励接收仪的进口依赖,研究高频信号激励接收方法。本文超声激励电路利用三级管雪崩击穿特性,以及MARX拓扑电路的电压倍增原理,通过减小激励脉冲脉宽时间,提升带宽覆盖范围。研究了高频超声信号接收电路,并集成超声激励接收仪。研究实现了设备的国产化替代,填补国内超声领域100~500 MHz高频脉冲收发仪的空白。实验结果表明,设计产生的高频激励信号峰峰值不小于128 V、上升沿时间小于0.47 ns、脉宽小于3.5 ns,系统工作带宽覆盖500 MHz,满足高频超声测量系统的需求。     

继电保护定值在线发放管理系统及其安全防护

为实现继电保护定值的在线发放和满足定值在线发放过程中的机密性、完整性、真实性和不可否认性等安全需求,本文在对继电保护定值在线发放管理系统进行需求分析的基础上,设计了定值在线流转、设备参数表上传、系统认证与访问控制、SSL/TLS协议通信模块;基于双因子身份认证、基于任务的访问控制策略和SSL/TLS协议,设计了基于安全信道的数据加密/解密方案和系统安全防护方案;采用C#语言、SQL数据库和OpenSSL开发工具,开发了具有定值单录入、定值单校核、定值单审批和设备参数上传等功能的继电保护定值在线发放管理系统。实际应用结果表明,该系统可实现继电保护定值的在线流转,满足定值在线发放过程中的安全需求。     

一种高频超声波换能器驱动电路的设计

本文设计了一种高频超声波驱动电路,此超声波换能器驱动电路的发射频率高达1MHz,而目前包括集成电路发射模块和分立元件组成的驱动电路发射频率多为40kHz。本电路主要用于对精度要求极高,如基于超声波的精确测量、美容器等领域。此电路为超声波应用于更多的领域提供了必要的准备。     

新型永磁接触器的智能控制单元设计

基于STC12C5410AD单片机,设计了一款以智能化检测与控制为核心的永磁接触器智能控制单元.详细分析了各个功能模块硬件电路的设计方法和工作原理,及各模块的软件系统的主程序.最后对一台配置智能控制单元的140 A永磁接触器进行了试验分析.试验结果表明,采用PWM智能控制方法,可有效提高永磁接触器的储能电容的充电效率与分,合闸频率,减少触头的一、二次弹跳.     

基于FPGA的高精度频率计的设计与实现

为了实现对正弦信号频率的高精度测量,设计了一种基于FPGA的数字频率计;除测量频率外,该装置还可以测量双路方波信号的时间间隔和脉冲信号占空比.该频率计以FPGA和单片机为核心,采用“多路并行计数法”实现信号频率的高精度测量.输入信号经高频放大和比较模块转换为方波信号输入FPGA单元,经多路不同倍数分频后进行并行计数,最后由单片机选择输出精度高的一路计数值,利用换算关系得出最终的测量结果.经测试,该数字频率计可实现1 Hz～199 MHz、10 mVrms～1Vrms正弦信号的频率测量,相对误差的绝对值不大于0.0001％;100 Hz～1 MHz、50 mV～1 V同频方波的时间间隔测量,测量范围为0.1μs～100 ms,相对误差的绝对值不大于1％;50mV～1 V、1 Hz～5 MHz脉冲信号的占空比测量,相对误差的绝对值不大于1％.因此,具有测量精度高、测量频率范围宽和测量幅度范围大的特点.     

基于正交相位的吸收式带通滤波组件设计

提出了一种吸收式带通滤波器组件,由等相位功率分配-合成器、"+45°"高通滤波移相器、"-45°"低通滤波移相器和广义切比雪夫滤波器组-合成器对两支路正交信号进行合成;实现了对其相位和幅度的抵消,从而有效地吸收了带外返回信号,减小了带外信号反射量。基于该结构,设计实现了一款中心频率70MHz、IL≤4dB、BW_(-3dB)≤4.5MHz及BW_(ab)(吸收带宽):BW_(-3dB)≥10的吸收式带通滤波组件。     

A Single Photon Avalanche Diode Implemented in 130-nm CMOS Technology

We report on the first implementation of a single photon avalanche diode (SPAD) in 130 nm complementary metal-oxide-semiconductor (CMOS) technology. The SPAD is fabricated as p+/n-well junction with octagonal shape. A guard ring of p-well around the p+ anode is used to prevent premature discharge. To investigate the dynamics of the new device, both active and passive quenching methods have been used. Single photon detection is achieved by sensing the avalanche using a fast comparator. The SPAD exhibits a maximum photon detection probability of 41% and a typical dark count rate of 100 kHz at room temperature. Thanks to its timing resolution of 144 ps full-width at half-maximum (FWHM), the SPAD has several uses in disparate disciplines, including medical imaging, 3D vision, biophotonics, low-light illumination imaging, etc.     

VCO/RADIATOR MODULE TUNED BY FERROELECTRIC VARACTOR

ABSTRACT

Design of tunable Gunn diode—based active antenna module including a new type of planar dielectric resonator (PDR) tuned by a ferroelectric (FE) varactor is presented. The module is designed in such a way that the PDR acts both as a stabilizing resonator and as a radiator. MW properties of FE elements used for VCO tuning are considered. The module operates at frequency around of 17 GHz and demonstrates the radiated power of 8.8 ± 0.1 dBm over the 130 MHz tuning range and a phase-noise level of ?95 dBc/Hz at 100 kHz offset. 65° width of the radiation pattern in both the E and H planes corresponding to a gain of 5.1 dBi was measured. The maximal VCO power limited by the dielectric nonlinearity of a FE film in the microwave electric field and by the FE film overheating is estimated for FE film-based varactors of the planar and parallel structures.     

基于虚拟仪器技术的综合自动化系统测试仪

为了便于变电站综合自动化系统检验,研制了基于虚拟仪器技术的变电站综合自动化系统测试仪。该仪器主要由人机接口模块、主控模块和功率源模块组成。人机接口软件利用LabVIEW虚拟仪器编程语言作为开发平台,主控模块采用TI公司的TMS320LF2407为主处理器,功率源模块采用美国模拟器件公司的新一代高性能600 MHz处理器Blackfin533, 每周波拟合的波形点数高达30 000点,波形保真度高,几乎无谐波分量,输出无需低通滤波器,从而具有很好的暂态特性、相频特性、幅频特性。该仪器功能齐全,集成度高,利用