HEMT—HBT单片集成技术

简要介绍了ＨＥＭＴ－ＨＢＴ单片集成技术，并对目前用选择ＭＢＥ和ＨＥＭＴ－ＨＢＴ综合工艺制作的ＨＥＭＴ、ＨＢＴ器件和ＨＥＭＴ－ＨＢＴ，放大器性能进行了评述。     

采用局部分子束外延技术的HEMT─HBT集成

介绍微波电路中单片集成ＨＥＭＴ和ＨＢＴ的器件结构及其电学特性，采用ＨＥＭＴ－ＨＢＴ混合工艺的局部分子束外延技术，其器件特性与单一工艺的ＨＥＭＴ和ＨＢＴ基本相同     

采用局部分子束外延技术的HEMT—HBT集成

介绍微波电路中单片集成ＨＥＭＴ和ＨＢＴ的器件结构及其电学特性，采用ＨＥＭＴ－ＨＢＴ混合工艺的局部分子束外延技术，其器件特性与一工艺的ＨＥＭＴ和ＨＢＴ基本相同。     

HEMT与HBT集成放大器的设计

ＨＥＭＴ与ＨＢＴ集成放大器的设计ＨＥＭＴ以其高增益和低噪声著称，而ＨＢＴ则以高线性度和高效率见长，因此，把ＨＥＭＴ和ＨＢＴ集成在同一衬底上的性能引起了微波设计者的观注。ＴＲＷ高电子系统和技术部的Ｋ．－Ｗ．Ｋｏｂａｙａｓｈｉ等人报道了一种放大器；它是用...     

InP基HEMT／HBT器件工艺的最新进展

目前ＧａＡｓ基低噪声ＨＥＭＴ，包括用于ＤＢＳ的ＩｎＧａＡｓ／Ｎ－ＡｌＧａＡｓＰＨＥＭＴ已经商品化，且ＧａＡｓ基功率ＨＢＴ也将很快进入市场。尽管ＩｎＰ基ＨＥＭＴ或ＨＢＴ仍处于研究与发展阶段，但由于它们特殊的电性能，它们将有希望成为下一代异质结构器件。在继续改进器件结构和工艺过程中，晶格生长工艺的改进激发了一种新的趋势，提出并实现了一种用ＩｎＰ做有源层的新型器件结构。这篇文章主要描述了这样一种ＩｎＰ基ＨＥＭＴ和ＨＢＴ器件结构的最新进展。     

InP基HEMT／HBT器件工艺的最新进展

目前ＧａＡｓ基低噪声ＨＥＭＴ，包括用ＤＢＳ的ＩｎＧａＡｓ／Ｎ－ＡｌＣａＡｓＰＨＥＭＴ已经商品化，且ＧａＡｓ基功率ＨＢＴ也将很快进入市场。尽管ＩｎＰ基ＨＥＭＴ或ＨＢＴ仍处于研究与发展阶段，但由于它们特殊的电性能，它们将有希望成为下一代异质结构器件。在继续改进器件结构和工艺过程中，晶格生长工艺的改进激发了一种新的趋势，提出并实现了一种用ＩｎＰ做有源层的新型器件结构。这篇文章主要描述了这样一种ＩｎＰ基Ｈ     

具有低温特性的宽频带P－HEMT MMIC LNA

具有低温特性的宽频带Ｐ－ＨＥＭＴ　ＭＭＩＣ　ＬＮＡ《ＩＥＥＥＴＭＴ＆Ｔ》１９９３年第６—７期报道了使用０．２μｍＴ型栅，ＩｎＧａＡｓＰ－ＨＥＭＴ工艺制作了两个８～１８ＧＨＺ宽带单级ＭＭＩＣ低噪声放大器。其中一个为平衡结构的Ｐ－ＨＥＭＴＭＭＩＣＬＮＡ，...     

MBE生长的PM－HEMT结构中深电子陷阱及其钝化／消除

应用ＤＬＴＳ、ＳＩＭＳ和ＰＬ技术详细研究ＭＢＥ生长的ＰＭ－ＨＥＭＴ结构中深能级．样品的ＤＬＴＳ谱表明在ＰＭ－ＨＥＭＴ结构的ｎ－ＡｌＧａＡｓ层里存在着较大浓度和俘获截面的深电子陷阱，其能级位置分别位于导带下的０．６４ｅＶ和０．７９ｅＶ处．ＳＩＭＳ和ＰＬ谱表明深电子陷阱与ＡｌＧａＡｓ层里的氧含量和光致发光（ＰＬ）响应有直接的联系．它们影响ＰＭ－ＨＥＭＴ结构的电性能．应用氢等离子体对深电子陷阱进行处理，结果表明，在一定条件下，ＰＭ－ＨＥＭＴ结构样品里的深电子陷阱能有效地被钝化／消除．     

MBE生长的PM—HEMT结构中深电子陷阱及其钝化／消除

应用ＤＬＴＳ、ＳＩＭＳ和ＰＬ技术详细研究ＭＢＥ生长的ＰＭ－ＨＥＭＴ结构中深能级。样品的ＤＬＴＳ谱表明在ＰＭ－ＨＥＭＴ结构的ｎ－ＡｌＧａＡｓ层里存在着较大浓度和俘获截面的深电子陷阱，其能级位置分别位于导带下的０．６４ｅＶ和０．７９ｅＶ处。ＳＩＭＳ和ＰＬ谱表明深电子陷阱与ＡＬＧａＡｓ层时原氧含量和光致发光（ＰＬ）响应有直接的联系，它们影响ＰＭ－ＨＥＭＴ结构的电性能，应用氢等离子体对深电子陷阱进行处理，     

MPEG—2和DVD技术研讨

ＭＰＥＧ－２是数字电视广播（ＤＶＢ）、ＨＤＴＶ、ＤＶＤ等的基础，文章首先叙述了ＭＰＥＧ－２的图像压缩编码，然后介绍了ＭＰＥＧ－２的数据结构，对ＭＰＥＧ－１和ＭＰＥＧ－２进行了比较。并对ＤＶＤ标准和ＤＶＤ的技术要点作了全面介绍。     

All-active monolithic InP-based HBT VCO with tunable HEMT inductor

A novel HEMT-HBT VCO is presented; it is the first all-active analogue VCO demonstrated using InP HEMT-HBT integrated MMIC technology. The MMIC monolithically integrates an InP common-collector HBT oscillator with a tunable InP HEMT active inductor using selective MBE. The novel HEMT-HBT VCO can provide performance advantages over analogue VCOs such as the multi-vibrator, and has direct implications for high speed clock recovery circuits needed in InP based optoelectronic IC applications     

A monolithically integrated HEMT-HBT low noise high linearityvariable gain amplifier

We report on a 1-6 GHz HEMT-HBT three-stage variable gain amplifier (VGA), which is realized using selective molecular beam epitaxy (MBE). The VGA integrates an HEMT low noise amplifier with an HBT analog current-steer variable gain cell and output driver stage to achieve a combination of low noise figure, wide gain control, and high linearity. The HEMT-HBT VGA MMIC obtains a maximum gain of 21 dB with a gain control range >30 dB, a minimum noise figure of 4.3 dB, and an input IP3 (IIP3) greater than -4 dBm over 25 dB of gain central range. By integrating an HEMT instead of on HBT preamplifier stage, the VGA noise figure is improved by as much as 2 dB compared to an all-HBT single-technology design. The HEMT-HBT MMIC demonstrates the functional utility and RF performance advantage of monolithically integrating both HEMT and HBT devices on a single substrate     

HEMT-HBT matrix amplifier

A novel matrix amplifier using simultaneously high electron-mobility transistors (HEMTs) and heterojunction bipolar transistors (HBTs) is proposed in this paper. The amplifier includes HEMTs in the first tier and HBTs in the second tier. The HEMT-HBT matrix amplifier in comparison to the HEMT matrix amplifier presents a notable lower dc power consumption without remarkable gain and bandwidth reduction, maintaining the advantage of using HEMTs in the first tier. A theory to demonstrate that the amplifier performance can be optimized if the HBTs in the second tier are properly chosen is also proposed. A comparison among the HEMT-HBT matrix amplifier, HEMT matrix amplifier, and HBT matrix amplifier is also presented     

A novel self-oscillating HEMT-HBT cascode VCO-mixer using an activetunable inductor

Here we describe a unique Ka-band self-oscillating HEMT-HBT cascode mixer design which integrates an active tunable resonator circuit. The VCO-mixer MMIC integrates GaAs HEMT's and HBT's using selective molecular beam epitaxy (MBE) technology. The HEMT-HBT cascode active mixer operates similarly to a dual-gate mixer. The HBT of the cascode is used to construct a VCO by presenting the base with an HEMT tunable active inductor. The VCO can be tuned from 28.5 to 29.3 GHz while providing ≈0 dBm of output power. Operated as an upconverter, the MMIC achieves 6-9 dB conversion loss over a 31-39 GHz output frequency band. Using these active approaches, both VCO and mixer functions were integrated into a compact 1.44×0.76 mm² chip area. The active RF integrated circuit (IC) techniques presented here have direct implications to future high complexity millimeter-wave monolithic integrated circuits (MIMICs) for ultrahigh-speed clock recovery and digital radio applications     

Monolithic HEMT-HBT integration by selective MBE

We have achieved successful monolithic integration of high electron mobility transistors and heterojunction bipolar transistors in the same microwave circuit. We have used selective molecular beam epitaxy and a novel merged processing technology to fabricate monolithic microwave integrated circuits that incorporate both 0.2 μm gate-length pseudomorphic InGaAs-GaAs HEMTs and 2 μm emitter-width GaAs-AlGaAs HBTs. The HEMT and HBT devices produced by selective MBE and fabricated using our merged HEMT-HBT process exhibited performance equivalent to devices fabricated using normal MBE and our baseline single-technology processes. The selective MBE process yielded 0.2 μm HEMT devices with g_m=600 mS/mm and f_T=70 GHz, while 2×10 μm² HBT devices achieved β>50 and f_T=21.4 GHz at J_c=2×10⁴ A/cm². The performance of both a 5-10 GHz HEMT LNA with active on-chip HBT regulation and a 20 GHz Darlington HBT amplifier are shown to be equivalent whether fabricated using normal or selective MBE     

Alternative Schemes for Dynamic Secure VPN Deployment in UMTS

Three alternative schemes for secure Virtual Private Network (VPN) deployment over the Universal Mobile Telecommunication System (UMTS) are proposed and analyzed. The proposed schemes enable a mobile node to voluntarily establish an IPsec-based secure channel to a private network. The alternative schemes differ in the location where the IPsec functionality is placed within the UMTS network architecture (mobile node, access network, and UMTS network border), depending on the employed security model, and whether data in transit are ever in clear-text, or available to be tapped by outsiders. The provided levels of privacy in the deployed VPN schemes, as well as the employed authentication models are examined. An analysis in terms of cost, complexity, and performance overhead that each method imposes to the underlying network architecture, as well as to the mobile devices is presented. The level of system reliability and scalability in granting security services is presented. The VPN management, usability, and trusted relations, as well as their behavior when a mobile user moves are analyzed. The use of special applications that require access to encapsulated data traffic is explored. Finally, an overall comparison of the proposed schemes from the security and operation point of view summarizes their relative performance. Christos Xenakis received his B.Sc. degree in computer science in 1993 and his M.Sc. degree in telecommunication and computer networks in 1996, both from the Department of Informatics and Telecommunications, University of Athens, Greece. In 2004 he received his Ph.D. from the University of Athens (Department of Informatics and Telecommunications). From 1998–2000 was with the Greek telecoms system development firm Teletel S.A., where was involved in the design and development of advanced telecommunications subsystems for ISDN, ATM, GSM, and GPRS. Since 1996 he has been a member of the Communication Networks Laboratory of the University of Athens. He has participated in numerous projects realized in the context of EU Programs (ACTS, ESPRIT, IST). His research interests are in the field of mobile/wireless networks, security and distributed network management. He is the author of over 15 papers in the above areas. Lazaros Merakos received the Diploma in electrical and mechanical engineering from the National Technical University of Athens, Greece, in 1978, and the M.S. and Ph.D. degrees in electrical engineering from the State University of New York, Buffalo, in 1981 and 1984, respectively. From 1983 to 1986, he was on the faculty of Electrical Engineering and Computer Science at the University of Connecticut, Storrs. From 1986 to 1994 he was on the faculty of the Electrical and Computer Engineering Department at Northeastern University, Boston, MA. During the period 1993–1994 he served as Director of the Communications and Digital Processing Research Center at Northeastern University. During the summers of 1990 and 1991, he was a Visiting Scientist at the IBM T. J. Watson Research Center, Yorktown Heights, NY. In 1994, he joined the faculty of the University of Athens, Athens, Greece, where he is presently a Professor in the Department of Informatics and Telecommunications, and Director of the Communication Networks Laboratory (UoA-CNL) and the Networks Operations and Management Center. His research interests are in the design and performance analysis of broadband networks, and wireless/mobile communication systems and services. He has authored more than 150 papers in the above areas. Since 1995, he is leading the research activities of UoA-CNL in the area of mobile communications, in the framework of the Advanced Communication Technologies & Services (ACTS) and Information Society Technologies (IST) programmes funded by the European Union (projects RAINBOW, Magic WAND, WINE, MOBIVAS, POLOS, ANWIRE). He is chairman of the board of the Greek Universities Network, the Greek Schools Network, and member of the board of the Greek Research Network. In 1994, he received the Guanella Award for the Best Paper presented at the International Zurich Seminar on Mobile Communications.     

卫星遥感温室气体的大气观测技术进展

全球、区域及城市的碳浓度、碳源汇信息是应对气候变化、达成双碳目标、完善国际谈判、支持治理政策制定与执行的重要依据。国际认可的“自上而下” 方法将卫星观测作为基础的通量计算技术, 是验证温室气体排放清单的重要手段。系统介绍了温室气体的卫星探测载荷原理、类别和发展, 以及反演、估算CO2、CH4 和N2O 的浓度和排放通量的方法, 还有探测缺失和误差存在的影响因素等; 分析了对卫星探测温室气体能力提高的迫切需求, 浓度反演和排放量估算精度不足, 以及N2O、氟化物等其他温室气体遥感研究缺乏、地基遥感验证能力薄弱等问题; 最后总结了我国温室气体卫星遥感技术的发展趋势, 主要是面向主被动高时空分辨率卫星的研制应用、高精度多尺度排放量估算(特别针对城市、小区域和点源尺度)、氟化物遥感评估等主题, 以加强对碳排放的量化观测, 并增强对碳循环的理解, 提高感知和应对气候变化的能力。     

单目图像序列光流三维重建技术研究综述

由单目图像序列光流重建物体或场景的三维运动与结构是计算机视觉、图像处理与模式识别等领域的重要研究内容,在机器人视觉、无人机导航、车辆辅助驾驶以及医学影像分析等方面具有重要的应用。本文首先从精度与鲁棒性等方面对单目图像序列光流计算及三维重建技术近年来取得的进展进行综述与分析。然后采用Middlebury测试图像序列对HS、LDOF、CLG-TV、SOF、AOFSCNN 和 Classic ＋NL 等典型光流算法以及 Adiv、RMROF、Sekkati 和DMDPOF等基于光流的间接与直接重建方法进行实验对比分析,指出各对比方法的优点与不足,归纳各类方法的性能特点与适用范围。最后对利用分数阶微分模型、非局部约束、立体视觉以及深度线索解决亮度突变、非刚性运动、运动遮挡与模糊情况下光流计算及重建模型的局限性与鲁棒性问题进行总结与展望。     

接入控制器安全网络管理系统的设计与实现

在讨论了接入控制器(AC)网络管理系统安全重要性的基础上,分析了SNMP协议的应用,包括对其3个版本SNMPv1、SNMPv2及SNMPv3的优缺点的对比,并解释了该设备网络管理系统采用SNMPv3版本的原因.详细介绍了AC所实现的管理信息库的内容,包括RFC1213协议、IEEE 802.1x协议、RMON协议、Web DHCP、EAP_OTP、EAP_MD5、EAP_TLS、EAP_SIM等多种认证协议以及网络管理系统的五大功能.最后阐述了AC安全网络管理系统结构的设计与实现.     

宇航用电感器和变压器的失效特征分析

基于美国宇航用电感器和变压器发生失效的类型、原因、检测方法和发生频次的数据，总结了其失效特征，并给出了电感器和变压器在MIL-STD-981中各项试验重要性的认识。通过对美国和国内宇航用电感器和变压器由设计、生产产生的失效和实验中失效的对比分析。给出了此类元件的失效特征。依据国情，提出了如何通过制定标准和失效数据分析工作来提高国产宇航用电感器和变压器可靠性的建议。