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射频涡旋电磁波等相位面呈涡旋状,是一种携有新自由度-轨道角动量的电磁波。在轨道角动量模式理论分析的基础上,提出了在中心频率6 GHz处产生携有轨道角动量的涡旋电磁波的一种圆微带天线阵新结构,设计了以双层圆形微带天线为阵元组成的圆形阵列天线,通过控制馈源的相位差,得到模式量子数为0,1,2, 3, 4的轨道角动量。仿真结果表明:携轨道角动量的电磁波矢量电场图具有涡旋波阵面的特性,合适的阵列半径和馈线排列分布将产生携有良好轨道角动量特性的涡旋电磁波,而不当的阵列半径或馈线排列分布将出现能量的分散或者相互耦合的问题。 相似文献
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双异质结双极晶体管(DHBT)的性能与发射区-基区(E.B)异质结和基区.集电区(B.C)异质结的能带突变类型关系密切,本文基于热场发射.扩散模型,对两类不同能带结构类型的新型DHBT的性能做了比较分析.结论表明:与作为当今研究热点的E.B和B.C异质结构均为全交错II型能带结构的InP/GaSbAs/InPDHBT的性能相比,E.B异质结采用传统I型、B.C异质结采用交错II型的一类新型能带结构的InAlAs/GaSbAs/InPDHBT虽然在开启电压上更高,但具有更好的电流驱动能力、直流增益和高频性能. 相似文献
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重掺杂禁带变窄效应引起异质结导带、价带带阶的扰动,从而使突变HBT异质结界面势垒的形状和高度发生了变化,这将对电流传输特性产生重要的影响.基于热场发射-扩散模型,对这一现象进行了深入的研究.得到的结论是:异质结界面势垒的扰动引起内建势的变化对电流影响的重要性远大于其引起隧道效应发生区域的变化,这是由于内建势的变化对电流的影响反映在指数项;因此对于突变HBT,精确考虑禁带变窄在导带与价带之间的分布对于器件性能的分析是非常重要的.
关键词:
HBT
能带带阶
内建势
隧穿因子 相似文献
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双异质结双极晶体管(DHBT)的性能与发射区-基区(E-B) 异质结和基区-集电区(B-C)异质结的能带突变类型关系密切, 本文基于热场发射-扩散模型, 对两类不同能带结构类型的新型DHBT的性能做了比较分析. 结论表明: 与作为当今研究热点的E-B和B-C异质结构均为全交错II型能带结构的InP/GaSbAs/InP DHBT的性能相比, E-B异质结采用传统I型、B-C异质结采用交错II型的一类新型能带结构的InAlAs/GaSbAs/InP DHBT虽然在开启电压上更高, 但具有更好的电流驱动能力、直流增益和高频性能. 相似文献
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肺癌是危害人类生命的主要癌种之一,诱发肺癌的第一位因素是吸烟,第二位因素是吸入氡及其子体后的内照射. Lung cancer is one of the main killers to mankind in all kinds of cancers.The first factor inducing lung cancer is cigarette smoking. The second factor is the internal exposures from the intake of Radon and its airborne decay products. 相似文献
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First-principles investigation of BAs and BxGa1-xAs alloys Using first-principles calculations in the generalized gradient approximation, the electronic properties of BAs and BxGa1-xAs alloys are studied. At the Brillouin-zone centre, the lowest conduction band is the three-degenerate p-like Г15c state rather than s-like Г1c state, and the conduction band minimum (CBM) is along the A line between the Г and X points-at approximately 11/14(1,0,0)2π/a. With boron content at 0%-18.75%, BxGa1-xAs alloys have a small (2.6 eV) and relatively composition-independent band-gap bowing parameter, the band-gap increases monotonically by -18meV/B% with increasing boron content. In addition, the formation enthalpies of mixing for BxGa1-xAs alloys with boron content at 6.25% and 12.5% are calculated, and the large formation enthalpies may explain the difficulty in alloying boron to GaAs. 相似文献
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We propose a novel iteration-free blind phase noise estimation scheme for coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. In the new algorithm, the cost function is selected as the similar expression with real and imaginary parts as that in the modified constant modulus algorithm, and the new cost function is derived under some assumptions, where it is infinitely approximated by the sine and cosine functions. By means of the analytical formula of the cost function, the initial coarse common phase error can be obtained with only some samples, where the algorithm avoids computational complexity of conventional blind phase noise compensation scheme. In CO-OFDM systems with high-order modulation format (32 quadrature amplitude modulation) and narrow linewidth lasers, it is proved by the simulation results that the nhase noise can be effectively compensated with the proposed blind estimation method. 相似文献
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基于GaAs 0.25 μm增强/耗尽型(E/D)赝配高电子迁移率晶体管(pHEMT)工艺,研制了一款Ku波段6位数字衰减器微波单片集成电路(MMIC)。该6位数字衰减器由6个基本衰减位级联组成,可实现最大衰减量为31.5 dB、步进为0.5 dB的衰减量控制。采用简化的T型衰减结构,实现了0.5 dB和1 dB的衰减位。16 dB衰减位采用开关型衰减拓扑,在提高衰减平坦度的同时,有效降低其附加相移。测试结果表明,在12~18 GHz的频率内,数字衰减器衰减64态均方根误差(RMS)小于0.25 dB,附加相移为?0.5°~+9.5°,插入损耗小于4.9 dB,输入输出驻波比均小于1.5∶1。芯片尺寸为3.00 mm×0.75 mm。该芯片电路具有宽频带、高衰减精度、小尺寸的特点,主要用于微波相控阵收发组件、无线通讯等领域。 相似文献