天基信息系统互通技术研究

对构建天、空、地一体化综合电子信息系统中的天基信息系统与陆、海、空电子信息系统的互连互通问题,参考国际信息网络互通技术,研究了天基信息系统的组网运行和信息传递,及其与陆、海、空电子信息系统互通的概念、互通参考模型、互通单元的功能要求等内容。     

导读

<正>当前,由于陆地信息系统已经无法充分满足信息化社会及国防信息化广域覆盖与多类信息融合共享的需求,在离地一定高度的空间建立信息基础设施是未来信息网络发展的需求。空间信息基础设施必须由空间卫星(亦称航天器)系统来完成对天基信息的感知、传输等一系列任务。因此,近年来国际航天活动频次居历史高位,新型发射方式促使航天器的数量激     

对建设我国“天地一体化信息网络”的思考

得益于低成本火箭发射技术、微小卫星平台技术和载荷技术的迅猛发展,实现全球信息,特别是天基信息共享的天地一体化信息网络正在全世界范围内引发广泛关注.考虑到我国各类天基信息系统发展中面临的一些特殊制约条件,自主建设以天基网为核心的天地一体化信息网络迫在眉睫.它将为我国智慧城市、应急救灾、航空航天、国家安全等多个领域的发展提供必要的保障.本文在梳理了国内外相关发展现状的基础上,就我国天地一体化信息网络的基本概念提出了三点基本认识,分析了这一网络可采取的基本架构和面临的主要技术难点,并对我国天地一体化信息网络的初步建设工作提出了几点粗浅的建议.     

给信息网络加把“锁”

自从信息网络继广播、电视和报刊之后成为人类第四媒体以来，它的安全已成为人们普遍关注的问题。信息社会网络的安全是最大的安全已逐渐成为人之共识。 领空、领海和领土是一个国家主权的象征，伴随着信息网络的建立与发展，信息疆域应运而生。信息疆域是“软边界”，无论是天、空、地、海，只要有信息网络涉足的地方，都是它的天下。一个国家如果信息疆域遭到袭击，从某种意义上说，就无领空、领海和领土的主权可言。 信息网络是一个国家的神经系统，如果信息网络遭到袭击或出现安全问题，等于摧毁了一个国家寻求发展的基础设施，好比是釜…     

外军一体化联合战场情报、监视与侦察系统的发展

陆、海、空、天战场信息获取、处理、传输和应用一体化,是外军自20世纪90年代以来,情报、监视与侦察系统发展的一个重要趋势,尤其是自2001年年底的阿富汗战争以后,外军更是加快了其发展的步伐。因此,本文在描述外军战场情报、监视与侦察系统近年来发展特点的基础上,重点介绍了外军一体化联合战场情报、监视与侦察系统的基本概念、体系结构及其关键技术等。     

5G NTN关键技术研究与演进展望

5G非地面网络（non-terrestrial network,NTN）技术是5G通信系统面向卫星通信和低空通信等新应用场景的重要技术，标志着5G技术应用从陆地通信走向了空间通信。首先分析了5G NTN和地面5G的差异点，包括网络架构、时频同步、HARQ和移动性管理等。进而介绍了3GPP Release 17的5G NTN标准进展及关键技术点与3GPP Release 18的5G NTN增强技术。最后展望了未来空、天、地一体化的技术演进。通过对5G NTN技术研究和标准分析，明确了5G和卫星通信融合的技术路线，并为后续6G空、天、地融合系统研究和设计提供基础。     

基于居民便利服务信息的模型构建

随着网络技术的广泛发展和应用,在城乡一体化发展中逐渐涌现出居民小区家政信息化服务需求紧缺的情况。在居民小区内,采用网络技术和数据挖掘技术,将小区居民订制的各类生活服务信息及时汇总、保存,并进行数据信息挖掘、分析,建立需求购进量模型,以便对于特定人群形成信息服务链,提供滚动显示、短信实时通知等便民服务。以此提高小区物业服务质量和居民的生活质量,为居民小区后期信息化建设提供参考。     

天地一体化信息网络在我国民航领域的应用设想

天地一体化信息网络工程将构建全球覆盖的安全、高效、实时、宽带数据传输网络,基于天地一体化信息网络的新一代机载通信、导航、监视系统是未来我国民用航空电子系统发展的重要趋势之一,可以显著提升机载航电系统能力,为航空运输的安全性、经济性、环保性、舒适性带来巨大的变革。在分析国外航空卫星系统在民用航空领域应用现状的基础上,针对我国天地一体化信息网络在民用航空领域的应用差距,提出了基于我国自主卫星系统的天地一体化信息网络在民用航空领域应用的建设设想、实施步骤及适航考虑。     

关于建立低空空域无线立体通信网络的探讨

随着空域的逐步开放以及无人机和通用航空工业中泛在连接、多网深度融合等技术的发展,迫切需要建设一张能够满足空天地一体化的通信网络。天,有卫星通信网络;地,有移动通信网络;空,除了陆地移动通信系统的末梢稍有覆盖外,在300 m到3 000 m的空域几乎没有一张可用的通信网络,更无法满足未来发展的需求。为此,就低空空域如何结合5G现状以及6G的前瞻性构建立体通信网进行了探讨,提出了莲蓬式立体组网方案,可以有效弥补低空空域目前无网络覆盖的空白,满足该区域物物相连、物人相连、人人相连的需求,为低空开放奠定良好的通信基础。     

通信、网络、计算融合的天地一体化信息网络体系架构研究

随着人类活动范围从大陆向海洋、太空的不断扩展,世界各国纷纷开始布局全球无缝覆盖、连接无处不在的天地一体化信息网络建设。天地一体化信息网络是天基网络与地面网络的深度融合,不是简单的地面向空间的拓展与叠加。从融合的角度出发,首先梳理了地面互联网、移动通信网、天基信息网络发展现状以及存在的问题与挑战;然后总结分析了天地一体化信息网络体系架构研究现状以及新型网络架构向云化、智能化发展的趋势;最后提出了通信、网络、计算融合的天地一体化信息网络的体系架构,并从物理架构、功能架构、物理与功能架构映射等多个维度进行了阐述,提出了一体化信息通信系统、一体化网络系统、一体化信息系统的3层功能架构模型,以期为后续天地一体化信息网络的研究、建设和标准化提供有价值的建议和参考。     

Performance improvement in tensile-strained In/sub 0.5/Al/sub 0.5/As/In/sub x/Ga/sub 1-x/As/In/sub 0.5/Al/sub 0.5/As metamorphic HEMT

This paper proposes a In/sub 0.5/Al/sub 0.5/As/In/sub x/Ga/sub 1-x/As/In/sub 0.5/Al/sub 0.5/As (x=0.3-0.5-0.3) metamorphic high-electron mobility transistor with tensile-strained channel. The tensile-strained channel structure exhibits significant improvements in dc and RF characteristics, including extrinsic transconductance, current driving capability, thermal stability, unity-gain cutoff frequency, maximum oscillation frequency, output power, power gain, and power added efficiency.     

Very low-noise Al/sub 0.3/Ga/sub 0.7/As/Ga/sub 0.65/In/sub 0.35/As/GaAs single quantum-well pseudomorphic HEMTs

AlGaAs/GaInAs/GaAs pseudomorphic HEMTs with an InAs mole fraction as high as 35% in the channel has been successfully fabricated. The device exhibits a maximum extrinsic transconductance of 700 mS/mm. At 18 GHz, a minimum noise figure of 0.55 dB with 15.0 dB associated gain was measured. At 60 GHz, a minimum noise figure as low as 1.6 dB with 7.6 dB associated gain was also obtained. This is the best noise performance yet reported for GaAs-based HEMTs.<>     

A 12 /spl times/ 12 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode array

We report a 12 /spl times/ 12 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode (APD) array. The mean breakdown voltage of the APD was 57.9 V and the standard deviation was less than 0.1 V. The mean dark current was /spl sim/2 and /spl sim/300 nA, and the standard deviation was /spl sim/0.19 and /spl sim/60 nA at unity gain (V/sub bias/ = 13.5 V) and at 90% of the breakdown voltage, respectively. External quantum efficiency was above 40% in the wavelength range from 1.0 to 1.6 /spl mu/m. It was /spl sim/57% and /spl sim/45% at 1.3 and 1.55 /spl mu/m, respectively. A bandwidth of 13 GHz was achieved at low gain.     

Al/sub 0.3/Ga/sub 0.7/As/In/sub x/Ga/sub 1-x/As (0/spl les/x/spl les/0.25) doped-channel field-effect transistors (DCFET's)

The properties of both lattice-matched and strained doped-channel field-effect transistors (DCFET's) have been investigated in AlGaAs/In/sub x/Ga/sub 1-x/As (0/spl les/x/spl les/0.25) heterostructures with various indium mole fractions. Through electrical characterization of grown layers in conjunction with the dc and microwave device characteristics, we observed that the introduction of a 150-/spl Aring/ thick strained In/sub 0.15/Ga/sub 0.85/As channel can enhance device performance, compared to the lattice-matched one. However, a degradation of device performance was observed for larger indium mole fractions, up to x=0.25, which is associated with strain relaxation in this highly strained channel. DCFET's also preserved a more reliable performance after biased-stress testings.<>     

Morphological and electrical characterization of SixCryCzBv thin films

Si_xCr_yC_zB_v thin films with several compositions have been studied for integration of high precision resistors in 0.8 μm BICMOS technology. These resistors, integrated in the back-end of line, have the advantage to provide high level of integration and attractive electrical behavior in temperature, for analog devices. The film morphology and the structure have been investigated through transmission electron microscopy analysis and have been then related to the electrical properties on the base of the percolation theory. According to this theory, and in agreement with experimental results, negative thermal coefficient of resistance (TCR) has been obtained for samples with low Cr content, corresponding to a crystalline volume fraction below the percolation threshold.Samples with higher Cr content exhibit, instead, a variation of the TCR as a function of film thickness: negative TCR values are obtained for thickness lower than 5 nm, corresponding to a crystalline volume fraction below the percolation threshold; positive TCR are obtained for larger thickness, indicating the establishment of a continuous conductive path between the Cr rich grains. This property seems to be determinant in order to assure the possibility to obtain thin film resistors almost independent on the temperature.     

Highly linear Al/sub 0.3/Ga/sub 0.7/N-Al/sub 0.05/Ga/sub 0.95/N-GaN composite-channel HEMTs

We report an Al/sub 0.3/Ga/sub 0.7/N-Al/sub 0.05/Ga/sub 0.95/N-GaN composite-channel HEMT with enhanced linearity. By engineering the channel region, i.e., inserting a 6-nm-thick AlGaN layer with 5% Al composition in the channel region, a composite-channel HEMT was demonstrated. Transconductance and cutoff frequencies of a 1 /spl times/100 /spl mu/m HEMT are kept near their peak values throughout the low- and high-current operating levels, a desirable feature for linear power amplifiers. The composite-channel HEMT exhibits a peak transconductance of 150 mS/mm, a peak current gain cutoff frequency (f/sub T/) of 12 GHz and a peak power gain cutoff frequency (f/sub max/) of 30 GHz. For devices grown on sapphire substrate, maximum power density of 3.38 W/mm, power-added efficiency of 45% are obtained at 2 GHz. The output third-order intercept point (OIP3) is 33.2 dBm from two-tone measurement at 2 GHz.     

Comparison between Pt/TiO2/Pt and Pt/TaOX/TaOY/Pt based bipolar resistive switching devices

Nonvolatile memories have emerged in recent years and have become a leading candidate towards replacing dynamic and static random-access memory devices. In this article, the performances of TiO₂ and TaO₂ nonvolatile memristive devices were compared and the factors that make TaO₂ memristive devices better than TiO₂ memristive devices were studied. TaO₂ memristive devices have shown better endurance performances (10⁸ times more switching cycles) and faster switching speed (5 times) than TiO₂ memristive devices. Electroforming of TaO₂ memristive devices requires~4.5 times less energy than TiO₂ memristive devices of a similar size. The retention period of TaO₂ memristive devices is expected to exceed 10 years with sufficient experimental evidence. In addition to comparing device performances, this article also explains the differences in physical device structure, switching mechanism, and resistance switching performances of TiO₂ and TaO₂ memristive devices. This article summarizes the reasons that give TaO₂ memristive devices the advantage over TiO₂ memristive devices, in terms of electroformation, switching speed, and endurance.     

Electrooptic ferroelectric Na/sub 0.5/K/sub 0.5/NbO/sub 3/ films

We report on waveguiding and electrooptic properties of epitaxial Na/sub 0.5/K/sub 0.5/NbO/sub 3/ films grown by radio-frequency magnetron sputtering on Al/sub 2/O/sub 3/(11_02) single crystal substrates. High optical waveguiding performance has been demonstrated in infrared and visible light. The in-plane electrooptic effect has been recorded in transmission using a transverse geometry. At dc fields, the effective linear electrooptic coefficient was determined to 28 pm/V, which is promising for modulator applications.     

A 1 cm/spl times/1 cm In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode array

We report a 1 cm/spl times/1 cm array of 100 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiodes (APD). The average breakdown voltage was 28.7 V with a standard deviation of less than 0.5 V. The distribution of breakdown voltage across the area followed a radial pattern consistent with a slight epitaxial growth nonuniformity. The mean dark current at a gain of 10, or 6.1 A/W, was 10.3 nA, and none of the 100 APDs had a dark current of more than 25 nA. The bandwidth at a gain of 10 was 6.2 GHz, and the maximum gain-bandwidth product was 140 GHz. This technology is ideally suited for next-generation three-dimensional imaging applications.