高速InP基半导体电光调制器行波电极结构研究

对PIN型和NIN型两种InP基Mach-Zehnder电光调制器的电极结构进行了数值仿真研究,从而确定出适于这两种电光调制器的行波电极结构。仿真结果表明,NIN型电光调制器可采用简单的单臂类微带电极,而PIN型电光调制器需采用周期容性负载电极,以达到良好的阻抗匹配特性和传输特性。进一步地,提出了将串联推挽式行波电极结构应用于PIN型电光调制器,可以简化制作工艺并获得良好的微波特性。     

改善微带贴片相控阵天线轴比的方法研究

通过对微带贴片天线单元的仿真与优化,得出了法向轴比小于3 dB的右旋圆极化微带贴片天线单元;用所得的天线单元组阵得到9元相控阵天线,仿真得到其S11参数小于–16 dB、增益大于13 dB和轴比小于3 dB。针对微带贴片相控阵天线的轴比特性,提出了降低轴比的几种布阵方法,得到0.2 dB的轴比,最后分析并总结了改善微带贴片相控阵天线轴比的一般方法。     

改善微带贴片相控阵天线轴比的方法研究

通过对微带贴片天线单元的仿真与优化,得出了法向轴比小于3 dB的右旋圆极化微带贴片天线单元;用所得的天线单元组阵得到9元相控阵天线,仿真得到其S11参数小于-16 dB、增益大于13 dB和轴比小于3 dB.针对微带贴片相控阵天线的轴比特性,提出了降低轴比的几种布阵方法,得到0.2 dB的轴比,最后分析并总结了改善微带贴片相控阵天线轴比的一般方法.     

MMIC的微带线中瞬态信号失真的联合时频分析

用联合时频分析的方法对微带线中传输的瞬态信号的失真进行了分析,在时频二维平面上得到了信号波形的畸变、色散、功率谱的分布,克服了传统分析方法中时域与频域相分离的缺点.应用FDTD计算出皮秒高斯脉冲在MMIC的三种典型微带结构中传输一段距离后的波形,利用Wigner-Ville分布对其进行分析,结果更清晰的显示了三种微带结构对瞬态信号传播特性的差别.     

电光取样技术在ps级超短电脉冲测量和GHz高频电信号测量中的应用

对ps级超短电脉冲测量而言,电光取样是目前最准确、最有效的方法之一。本文介绍了电光取样的基本测量原理及实验途径,对测量的误差因素进行了分析。电光取样对由电光晶体如GaAs、LiNbO_3等制成的光电器件的瞬态响应测量具有特殊优点。本文着重对GaAs集成电路的瞬态测量原理和方法及误差因素进行了介绍。电光取样基于谐波混频原理对GaAs高频场分布的测量也十分有效。     

基于DGS的微带DBR双工器的研究

提出了一种高隔离度的微带双工器结构.在微带双重行为谐振(DBR)滤波器中引入基于缺陷地结构(DGS)的低通滤波器,利用DGS的慢波特性减小DBR滤波器奇偶模之间的相速差,从而改善滤波器的上阻带特性.使用本文提出的微带滤波器结构设计并研制了一C波段的微带双工器,仿真和测试结果表明:微带双工器的插入损耗小于1.3dB,隔离度大于65dB.     

新型Ku频段全向微带阵列天线

设计了一种新型Ku频段全向天线,该天线由双面辐射微带阵列组成,通过串联形式馈电,实现了全向中等增益辐射特性.文中给出了微带阵列天线的设计方法,对该微带阵列天线的阻抗带宽特性、方向图特性和馈电结构进行了分析.结果表明,该微带阵列天线反射损耗小于-10 dB的绝对带宽为1.15 GHz,在可用频带内全向增益为6.8 dB～7.3 dB,E 面波束宽度在20°～24°,H面方向图不圆度在±0.5 dB以内.该天线能够满足微波通信系统要求.     

基于复合基底微机械微带特性研究

研究了一种复合基底微机械微带,通过理论推导得出微机械微带的特性计算表达式。首先用计算机模拟该微机械微带的性能,再用表面微细加工工艺加工了该微机械微带模型,最后用安捷伦矢量网络分析仪器测试模型,得出该微带在100GHz内无色散,最大损耗小于2dB。该微机械微带利于集成、尺度微小,可应用在微波、毫米波通信系统(器件)中,克服了常规微带在高频工作时色散严重、损耗大等缺点。     

微带结构行波普克尔盒的电光效应

采用准静态近似,讨论了微带结构行波普克尔盒(Pockels—cell)内的电场分布及晶体的电光效应。计算得出,由于电场的不均匀性,微带结构的LiTaO_3行波普克尔盒半波电压要比通常理想行波普克尔盒的半波电压大。     

用可控硅开关Q调电光晶体电压

本文阐述利用可控硅呈转折状态时的雪崩导通特性,使电光晶体以小于100 ns的时间快速退电,得到了体积小、功耗低、速度快、简单、可靠的电光晶体Q开关。     

Spontaneous Calcium Transients in Cultured Cortical Networks During Development

Spontaneous neuronal activity plays an important role in the development of the brain. Developmental changes in the spontaneous activity pattern of neuronal networks in vitro have been extensively studied by using the microelectrode array (MEA) recording system. However, little is known about the transition of spontaneous intracellular calcium dynamics, and the relationship between calcium transients and electrical activity during development. In the present paper, we carry out simultaneous recording of spontaneous electrical activity and intracellular calcium transients of rat cortical networks cultured on MEA. In one-week cultures, periodic synchronized bursts are observed and are followed by synchronized calcium transients. In three-week cultures, synchronized calcium transients are rarely observed despite the presence of highly complicated synchronized activity. Between these two states, in two-week cultures, slow, radial propagation of calcium waves independent of electrical activity is observed. Pharmacological treatments with the purinergic receptor antagonist suramin and gap junction blocker 18-$beta$ glycyrrhetinic acid reveal that the spontaneous radial calcium waves are mediated by the astrocytic network, and suggest that the astrocytic calcium waves can influence the electrical firing patterns of networks by locally affecting neuronal signaling. These results indicate that the various dynamics of intracellular calcium transients regulate the network maturation processes.      

深槽TVS研究

以静电放电（ESD）以及其他一些电压浪涌形式随机出现的瞬态电压,通常存在于各种电子器件中。随着半导体器件日益趋向小型化、高密度和多功能。电子器件越来越容易受到电压浪涌的影响,甚至导致致命的伤害。从静电放电到闪电等各种电压浪涌都能诱导瞬态电流尖峰,瞬态电压抑制器（TVS）通常用来保护敏感电路受到浪涌的冲击。基于不同的应用。瞬态电压抑制器可以通过改变浪涌放电通路和自身的箝位电压来起到电路保护作用。为了节省芯片面积,并且获得更高的抗浪涌能力,深槽TVS的概念已经被提出和研究。深槽TVS的结面形成于纵向的深槽的侧壁,这样,在相同的芯片面积下,它有更多的有效结面积,即更强的放电能力。我们也可以预见,深槽TVS的小封装尺寸对应用于保护高端IC非常关键。     

Modeling and testing of immunity of computerized equipment to fastelectrical transients

One of the major problems associated with testing computerized equipment for immunity stems from the fact that their susceptibility to electrical transients is time-variant. This paper develops an improved statistical model for the susceptibility of computerized equipment to electrical transients and illustrates a few affordable methods for estimating the mean and maximum malfunction probability in an operational cycle. Reinforcement learning algorithms are used to estimate the maximum susceptibility efficiently. These algorithms automatically restrict testing to the most susceptible time windows. This allows affordable testing for safety-related equipment and also supports effective redesign     

On-Chip Transient Detection Circuit for System-Level ESD Protection in CMOS Integrated Circuits to Meet Electromagnetic Compatibility Regulation

A new on-chip transient detection circuit for system-level electrostatic discharge (ESD) protection is proposed. The circuit performance to detect different positive and negative fast electrical transients has been investigated by the HSPICE simulator and verified in a silicon chip. The experimental results in a 0.13-m CMOS integrated circuit (IC) have confirmed that the proposed on-chip transient detection circuit can be used to detect fast electrical transients during the system-level ESD events. The proposed transient detection circuit can be further combined with the power-on reset circuit to improve the immunity of the CMOS IC products against system-level ESD stress.     

Protecting computer systems against power transients

The sources of electrical transients, broadly interpreted as occurrences of any disturbance, either on the power line or the computer system's data line, are reviewed. Common transients are overvoltages due to lightning strikes, transients caused by switching sequences in the power system, and undervoltages which could be caused by a nearby start-up of heavy loads or by distant faults. The impact of transients on small stand-alone and on distributed computer systems is examined. Growing concern among computer users that power-line surges, in particular, may damage equipment or cause loss of data has created a market for surge suppressors. Some guidelines are provided for choosing a protective device for both types of systems mentioned above. Potential negative side effects are indicated     

Transient RF signals during the switching of MESFET control devices

An analytical model that predicts the intrinsic small-signal switching transients for MESFET control devices is developed. Theoretical results for video-breakthrough and small-signal RF switching waveforms are in excellent agreement with measurements on many devices. Although the intrinsic transients are less than a few nanoseconds in duration, FET material aspects (such as surface states) can induce much longer transients. The 10-90% switching time, which is dominated by intrinsic effects, can be lowered by reducing gate length and gate bias resistance (the latter is more feasible with recently reported diode-gate FFTs)     

EDFA gain transients: experimental demonstration of a low cost electronic control

Er-doped fibre amplifier (EDFA) gain transients are dynamic performance-degrading effects that need to be effectively suppressed in next-generation reconfigurable optical networks. In this paper, we experimentally assess the feasibility of an electronic dynamic gain control based on low-cost optoelectronic components, showing that a linearized electrical circuit and a control bandwidth smaller than 1 MHz can achieve the same performance as the commonly proposed all-optical feedback solutions.     

Analysis of fast electrothermal dynamics in power BJT

It is well known that the self heating phenomenon in power bipolar devices strongly influences the electrical behavior. Heating phenomenon is a dynamic process ruled by different time constants. While the thermal dynamics associated to external heat exchange is an order of magnitude slower than the electrical one, the thermal dynamics occurring at the silicon level near the active junction is relatively faster and can interact with the electrical one. In this paper, it is proved that such a fast thermal dynamics is responsible for unstable oscillating electrical transients that can be detected in power bipolar transistors. An electrothermal resonance phenomenon Is theoretically and experimentally verified on a commercial power BJT. It is explained how such a phenomenon ran be operatively employed to extract the parameters of the fast thermal dynamics, difficult to measure with conventional procedures     

Investigations on the Susceptibility of ICs to Power-Switching Transients

Due to the fast changes of the voltage and current generated by the operation of power-switching circuits that supply inductive loads, wideband transients can be induced at the ports of electronic equipment operating in the same environment. The level of collected transients is responsible for the degradation of system performance as well as its reliability. This paper describes a circuit model by which the transient waveforms at the equipment ports can be analyzed for real applications in the early design stages. A compact injection probe, whose properties derive from simulations performed on the circuit model and on the results of experimental measurements, has been designed and fabricated to characterize IC susceptibility to electrical transients.