新型多频蝶形微带天线

微带天线工作频带较窄,若能同时激励多个谐振点,可以变相拓展带宽,因此设计一种多频蝶形微带天线。3块介质基板构成"U"型半封闭腔体,天线的辐射臂采用1 4周期正弦轮廓结构,在辐射臂上开取3对"工"字型缝隙,同时在馈电端口处加载枝节。实验结果表明,蝶形微带天线在5个雷达波段(S,C,X,Ku,K)各有1个谐振频点,分别为2.6 GHz,6.8 GHz,11.7 GHz,16.5 GHz,18.45 GHz。通过对比分析可知:在不改变天线整体尺寸的情况下,正弦边结构可调节谐振频点位置;加载的矩形枝节有利于改善天线的阻抗匹配度,降低回波损耗;"U"型半封闭腔体可有效提高增益,其中C波段的增益由0.71 dB可提升到4.30 dB。     

一种新型MICS频段可植入天线的设计

设计了工作在MICS频段,尺寸为10 mm×10 mm×1.905 mm的可植入天线。采用高相对介电常数材料和平面倒F结构微带天线(PIFA)结构以降低天线尺寸。经过软件HFSS仿真计算,对天线模型参数进行了优化,得到最佳的设计效果。天线在403 MHz的谐振频点上回波损耗小于–20 dB,在实现小型化的同时,保持–37 dB的天线远场增益,保证了天线工作的可靠性。     

一种新型小型化三频微带天线的设计

设计了一种可用于无线局域网/无线城域网(WLAN/WiMax)频段的小型化三频微带天线。该结构形似太极鱼,在鱼眼附近同轴馈电,并利用贴片上的一条矩形缝隙,既可实现阻抗匹配,又可使天线在贴片外边界3个位置产生谐振,进而实现在3个频段内同时工作。通过电磁仿真软件HFSS对天线进行仿真,结果表明,该天线在中心频点为2.45GHz,3.95GHz和5.25GHz处的回波损耗分别为29.7dB,29.2dB和27.4dB,天线性能良好。同时天线整体尺寸只有0.24λ×0.18λ(λ为频点2.45GHz时的自由空间波长),具有小型化的特点。该天线尺寸小且结构简单,具有良好的应用价值。其中2.45GHz和5.25GHz可用于WLAN频段,3.9GHz可用于WiMax频段。     

基于UC-EBG的吸波结构设计及其在微带天线中的应用

在共面紧凑型光子晶体结构(Uniplanar Compact Electromagnetic Bandgap,UC-EBG)基础上加载集总电阻,设计出一种新型吸波结构,并分析了其吸波原理。将其加载于微带天线,用于减缩天线带内雷达散射截面(Radar Cross Section,RCS)。仿真结果表明,在谐振频点,该吸波结构的吸波率达到99.8%。加载该结构后,天线的辐射性能基本保持不变,而对于垂直入射的TE波和TM波,其带内RCS分别减缩了26.22 dB和15.08 dB。实测结果与仿真结果较为吻合,证实了该结构可以减缩微带天线的带内RCS,从而提高其带内隐身性能。     

一种新型U型槽宽频微带天线

提出一种新型的低剖面宽带开槽微带天线。该天线通过U型槽加载,从而产生新的谐振点,达到展宽带的目的。采用HFSS软件对提出的天线模型进行仿真优化,结果显示,该天线在12.83 GHz、15.06 GHz两个频点产生谐振,天线阻抗带宽达到940 MHz和770 MHz     

一种新型宽频带E型微带天线的设计

介绍一种新型E型结构的微带天线。在U型微带天线中间加一段传输线构成新型E型微带天线,产生多点谐振,达到微带天线频带展宽的目的。通过改变馈电点位置和传输线的长度和宽度,实现微带天线的最佳匹配和频带的展宽。仿真结果表明,该天线在4.25～5.366GHz频带内反射系数均小于-10dB,方向最大增益达到9dB,相对带宽为23.2%。且对E型天线加工和测试,实测结果和仿真结果一致。     

一种K波段小型化MIMO天线设计北大核心CSCD

针对K波段微带天线具有体积小、方向性好等优势,设计了一款小型化多输入多输出(Multiple-Input Multiple-Output,MIMO)天线。通过对辐射贴片切角、接地板刻蚀缺陷地结构,保证天线小型化的同时拓宽带宽;通过在接地板加载多开口槽矩形寄生单元,降低中低频处耦合,刻蚀互补开口谐振环(Complementary Split-Ring Resonator,CSRR),在固定频点处产生谐振,隔离度有效提高。利用三维电磁仿真软件和矢量网络分析仪分别对该天线进行仿真与实测,结果表明:天线整体尺寸极小,仅为15 mm×24 mm×0.8 mm,天线在17~27.2 GHz(相对带宽达到46.2%)工作频段内S_(11)≤-10 dB,S_(21)≤-18.3 dB,包络相关系数ECC小于0.001。天线特性良好,可广泛应用于无线通信、射频识别及民用雷达等领域。     

波导式双正-近零媒质加载双频微带天线

提出了一种基于嵌入式弯曲线(EML)和互补金属开口谐振环(CSRR)结构的波导式双正-近零分层 人工媒质,将其加载在微带贴片天线上以实现双频工作特性。理论分析以及仿真和实测结果表明:加载了分层人工 媒质的双频微带天线,两个最低阶谐振模式分别是TM010 和修正型TM020 模式,且该天线在这两个谐振频点上具有比 较一致的边射式辐射特性。本文提出的双频微带天线具有结构紧凑、易于用印刷电路板工艺进行一体化制造的优 点。     

紧凑型电磁带隙结构在短路微带天线中的应用

该文提出一种带有紧凑型电磁带隙结构的短路微带天线,并与相同尺寸的普通短路微带天线作比较。测试结果表明该电磁带隙结构天线在增益上增加了3dB, 面的交叉极化有了明显的改善。同时也证明了设计具有同样谐振频率的电磁带隙结构单元,使用这种紧凑型结构的单元边长尺寸仅为普通结构的5060％左右。这对最终实现电磁带隙结构微带相控阵天线具有重要意义。     

基于BST可变电容的电调微带天线研究

采用BaxSr1–xTiO3(BST)可变电容作为调谐元件研制了一种工作频率可调的电调谐微带天线。该天线通过利用单片机控制电源单元输出不同的偏置电压来改变BST可变电容的电容大小,进而实现工作频点的调整。结果表明,当电源输出偏压在0-52 V变化时,该微带天线的工作频点可在1.47-1.61 GHz调节,回波损耗低于–15 dB。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.