光纤传感系统中APD增益温漂的动态补偿研究

为实现对雪崩光电二极管(APD)增益温漂的动态偏压补偿, 设计了高精度的ADC和DAC电路系统,对APD可以达到毫伏级的偏压控制精度和0.2 ℃的温度采样精度.依托光纤传感系统并运用数据采集与处理技术获得了在APD增益比较稳定的条件下其偏压与温度之间的线性关系以及增益温漂误差的偏压补偿公式,应用时传感系统能够实时补偿增益的温漂并且具有足以满足系统要求的补偿精度.     

APD阵列芯片偏置电压温度补偿系统设计与实现

为使APD阵列芯片在不同温度下保持较为恒定的增益,设计反向偏压自动温度补偿系统。采用STM32微处理器对热敏电阻分压采样和A/D转换后计算获得阵列芯片工作温度,根据工作温度求解出合适的反向偏压值,再通过调节数字电位器控制高压模块输出解算得到的反向偏压至APD阵列芯片。采用Matlab仿真方法获取匹配电阻的阻值避免了繁琐的数学推导。应用μC/OS嵌入式操作系统实现多任务程序设计,且任务间采用消息邮箱通信,提高了软件运行的稳定性和可靠性。测试结果表明,使用该温度补偿系统的5×5 APD阵列芯片的每个通道都能在不同温度下保持本通道输出信号幅度基本恒定,证明了系统的有效性和实用性。     

基于单片机多模式控制的APD偏压电路模块设计

针对雪崩光电二极管(APD)应用多样化的需求,提出多模式控制的APD偏压电路模块设计方案。基于APD工作原理,分析了APD增益系数、反向偏置电压、工作温度三者之间的关系,设计了具有多模式工作的APD偏压模块硬件电路,开展了详细的单片机软件功能设计。结合雪崩光电二极管进行了实验验证,结果表明在-40~+60℃温度范围内,该偏压电路模块具有温度补偿及多模式切换功能,输出电压偏差小于0.5 V,纹波小于100 mV,可实现APD多模式工作,满足工程化应用需要。     

APD最佳偏压温度补偿的实现方法

本文在对APD最佳雪崩增益分析的基础上,研究了最佳偏压和温度的关系并给出了温度偏压补偿的具体实现电路。     

光纤喇曼测温系统中APD增益稳定的研究

分布式光纤测温系统采用APD雪崩光电二极管作为接收器件,它的稳定性对后级的信号处理及系统主要技术指标起着决定性的影响.APD的增益受温度波动影响较大.对APD增益进行了分析,针对分布式光纤测温系统中喇曼光信号极微弱和强噪声的特点,设计了一温控系统和一反馈偏压补偿系统.实验证明温控温度波动小于0.1℃,测试输出电压波动小于0.5 mV,完全满足分布式光纤测温系统对APD增益稳定的高要求.     

Ge/Si SACM-APD器件分析

Ge/Si吸收区-电荷区-倍增区分离(SACM)结构的APD作为一种新型光电探测器已成为硅基APD器件研究的重点.对SACM Ge/Si型APD器件的基本结构及其主要特性参数,包括量子效率、响应度、暗电流等进行了理论分析及仿真验证.实验结果表明:在给定的器件参数条件下,所设计的APD器件的雪崩击穿电压为25.7 V,最大内部量子效率为91%,单位增益下响应度峰值为0.55 A/W,在750~1 500 nm范围内具有较高响应度,其峰值波长为1 050 nm;在高偏压以及高光照强度情况下,倍增区发生空间电荷效应从而导致增益降低.     

基于后向喇曼散射测温系统APD最佳雪崩增益分析

本文对基于后向Raman散射分布式光纤测温系统中APD的最佳雪崩增益Mopt进行了分析。文中系统讨论了APD雪崩增益和入射光功率、APD的工作温度和APD的偏置电压等的关系。提出了一套温度控制加偏压调节保持最佳雪崩增益的方法,并给出了偏压调节方程式。最后,针对系统提出了系统APD最佳雪崩增益的概念,给出了具体计算方法。实验结果证明分析是合理、正确的。     

基于ADL5317的APD偏压控制/光功率监测电路

介绍了ADL5317的引脚功能、内部结构和工作原理.针对APD偏置电压需要精确控制的要求,给出了一种具有高精度、宽动态范围的APD偏压控制/光功率监测功能的核心电路.     

星载激光测距仪APD最佳雪崩增益控制技术研究

针对激光测距仪星载应用环境的特殊性,研究了星载激光测距仪APD最佳增益控制技术。通过引入星载激光测距仪APD电流信噪比模型,分析了影响星载激光测距仪APD信噪比的关键因素。针对某星载激光测距仪的具体应用,展开了APD最佳增益控制技术研究,设计了温度增益反馈控制电路,并推导建立了温度增益数字反馈控制算法,实验验证了控制电路及算法的正确性和良好的温度适应性。实验结果表明,该控制电路和算法能够使得APD在-25~60℃温度范围下保持恒定增益,适用于星载激光测距仪APD最佳增益控制。     

4H-SiC 雪崩光电探测器中倍增层参数的优化模拟

应用ATLAS模拟软件,设计了吸收层和倍增层分离的（SAM）4H-SiC 雪崩光电探测器（APD）结构。分析了不同外延层厚度和掺杂浓度对器件光谱响应的影响,对倍增层参数进行优化模拟,得出倍增层的最优化厚度为0.26μm,掺杂浓度为9.0×1017cm^-3。模拟分析了APD的反向IV特性、光增益、不同偏压下的光谱响应和探测率等,结果显示该APD在较低的击穿电压66.4V下可获得较高的倍增因子105;在0V偏压下峰值响应波长（250nm）处的响应度为0.11A/W,相应的量子效率为58%;临近击穿电压时,紫外可见比仍可达1.5×103;其归一化探测率最大可达1.5×1016cmHz ^1/2 W^-1。结果显示该APD具有较好的紫外探测性能。     

Noise Temperature Characteristics and Gain-control of Avalanche Photodiodes for Laser Radar

Avalanche photodiodes（APDs） are promising light sensors with high quantum efficiency and low noise. It has been extensively used in radiation detection, laser radar and other weak signal detection fields. Unlike other photodiodes, APD is a very sensitive light detector with very high internal gain. The basic theory shows that the gain of APD is related to the temperature. The internal gain fluctuates with the variation of temperature. Investigated was the influence of the variation of the gain induced by the fluctuation of temperature on the output from APD for a very weak laser pulse input in laser radar. An active reverse-biased voltage compensation method is used to stabilize the gain of APD. An APD model is setup to simulate the detection of light pulse signal. The avalanche process, various noises and temperature＇s effect are all included in the model. Our results show that for the detection of weak light signal such as in laser radar, even a very small fluctuation of temperature could cause a great effect on APD＇s gain. The results show that the signal-tonoise ratio of the APD＇s output could be improved effectively with the active gain-control system.     

A precision variable-supply CMOS comparator

Several new techniques are presented for the design of precision CMOS voltage comparator circuits which operate over a wide range of supply voltages. Since most monolithic A/D converter systems contain an on-chip voltage reference, techniques have been developed to replicate the reference voltage in order to provide stable supply-independent DC bias voltages, and controlled internal voltage swings for the comparator. These techniques are necessary in order to eliminate harmful bootstrapping effects which can potentially occur in all AC coupled MOS analog circuits. An actively controlled biasing scheme has been developed to allow for differentially autozeroing the comparator for applications in differential A/D converter systems. A general approach for selecting the gain in AC-coupled gain stages is also presented. The comparator circuit has been implemented in a standard metal-gate CMOS process. The measured comparator resolution is less than 1 mV, and the allowable supply voltages range from 3.5 to 10 V.     

Modeling of two-dimensional gain profiles for InP-InGaAs avalanchephotodiodes with a stochastic approach

The two-dimensional (2-D) gain profiles for separate absorption, grading, charge and multiplication (SAGCM) InP-InGaAs avalanche photodiodes (APD's) have been modeled with a stochastic approach. To consider the influence of the curved diffusion edge on the electric field within the periphery region, equations are derived from the cylindrical Poisson's equation. The electric field profiles are computed at various APD radii and the electric field in the multiplication layer is reduced significantly for APD's with a partial charge sheet in the periphery. It is demonstrated by the modeled 2-D gain profiles that the premature edge breakdown can be effectively suppressed for such devices. The modeled 2-D gain profiles for APD's with a partial charge sheet incorporated in the periphery are in good agreement with the experimental results. The results and the uniformity issue of the 2-D gain profiles are discussed. The effect of using curved diffusion interfaces instead of a steep mesa step is also explored; this suggests that the fabrication of a charge sheet mesa step may complicate the gain uniformity issue. From our analyses, we find that the uncertainty and the symmetry of both patterning the charge sheet mesa structure and controlling the diffusion interface between the p⁺ InP top layer and the n^- InP multiplication layer are most likely to affect the uniformity and the symmetry of the 2-D gain profiles for the SAGCM InP-InGaAs APD's     

AC actuation contribution to the induced electromotive force in the miniaturized inductive planar microphone

In this paper, we aim to analyze the gain ratio in the output induced voltage of a CMOS-compatible miniaturized electrodynamic microphone which is based on the use of two coplanar concentric inductors. These latter are comparable to a concentric transformer with a secondary situated on the microphone diaphragm top. The study has been applied when the outer inductor is actuated using an AC bias instead of DC leading to a time-variable B-field. The induced output voltage expression has been evaluated using two distinct analytic methods: the magnetic field derivation and the electric field approach. When an AC current with frequency above that of the acoustic band is used to bias the primary, results show that the induced voltage increases and becomes independent from the incident pressure wave frequency. The paper demonstrates also that with an AC bias, the microphone induced voltage values can reach the order of hundreds of µVs, as opposed to only few µVs when applying a DC bias. The gain in the induced voltage has been investigated and it is shown that it can be correlated to the AC current frequency, ω_c, and the inner inductor fluctuation frequency, ω_p. Moreover, this has been quantified analytically and it is shown that it equals ω_c/8ω_p. This result will not only enhance the overall performance of the microphone, but will also make the preamplification design less complicated by increasing the SNR ratio.     

雪崩光电二极管恒虚警率控制在激光成像系统中的应用

雪崩光电二极管以其接收灵敏度高，响应速度快等优点，常用于扫描式激光成像系统中，由于雪崩光电二极管的工作电压随背景和温度的变化而变化，因此正确设置其工作偏压，对充分发挥接收系统的探测灵敏度是重要的。主要讨论采用恒虚警率控制法自动设置雪崩光电二极管的偏压，调整噪声门限以获得光电接收系统最佳工作状态。     

一种高精度低功耗的APD偏置电压模块设计

设计了一种具有升压和自动温度漂移补偿功能的雪崩光电二极管(APD)偏置电压模块,该模块包含正反馈振荡器、高频全波整流电路和温度补偿器.正反馈振荡器实现DC/AC的变换,并通过变压器进行电压放大;高频全波整流电路通过AC/DC变换输出直流高压;温度补偿器通过模拟温度传感器自动补偿APD的温度漂移.该模块大小为1.7 cm×2.7 cm,最大功耗为100 mW,输出电压在0～372 V连续可调,且最大纹波不超过0.004％,通过对模块中元器件参数的调整,能够对任意型号的APD进行电压偏置和温度补偿,偏置电压最大偏差不超过0.005％.     

Comparison of available detectors for digital optical fiber systems for the 1.2-1.55 µm wavelength range

Receiver sensitivity is estimated at 1.3 and 1.5 μm for commercial Ge APD's for bit rates between 8 and 1200 MBd, for a variety of APD diameters and operating temperatures. Although both holes and electrons are injected into the depletion region at these wavelengths, the measured photocurrent excess multiplication noise is found empirically to be well described by the simple expression for unilateral carrier injection into the depletion region, while the measured noise on the bulk leakage current can be characterized by the photocurrent parameters for wavelengthssim1.8 mum. Measurements at BTRL on a 140 Mbit/s system receiver using an Optitron GA-1 Ge APD at temperatures in the range20-60degC agree within 1 dB with the theoretical model using these data. The performance of Ge APD-based receivers is strongly influenced by noise on the leakage current and is therefore susceptible to temperature fluctuations. The ionization rates for holes and electrons are comparable in Ge, resulting in a high excess noise factor and a strong dependence of multiplication factor on bias voltage. Thus, APD's for long-wavelength digital optical receivers operating below ∼1 GBd require a bulk leakage current densityll 10^{-4}A/cm²and markedly different ionization rates for holes and electrons, in order to match the otherwise superior performance of the present-day high-impedance p-i-n/FET hybrid.     

The effect of nonuniform gain on the multiplication noise of InP/InGaAsP/ InGaAs avalanche photodiodes

We have investigated the effect of spatial gain uniformity on the multiplication noise of InP/InGaAsP/InGaAs avalanche photodiodes (APD's) with separate absorption, "grading," and multiplication regions. APD's with localized regions of high gain exhibit higher excess noise factors and poorer Performance in lightwave receivers than those with uniform gain.     

Si/SiGe/SiHBT直流特性的可靠性

对单台面SiGeHBT在E-B结反偏应力下直流特性的可靠性进行了研究。研究结果表明,随应力时间的增加,开启电压增加,直流电流增益下降,特别是在低E-B正偏电压时下降明显;而交流电流增益退化缓慢。