Input Impedance Characteristics of a T-Shaped Ridged Waveguide

This paper presents input impedance characteristics of a T-shaped ridged waveguide calculated by a magnetic wall model. They are also confirmed experimentally.     

基于Optiwave的脊形SiGe OI光波导结构设计

利用有效折射率的数值解法,计算出了SiGe OI脊形光波导的有效折射率.通过对SiGe OI光波导结构参量的理论分析和计算,得到了SiGe OI脊形光波导传输单模光波时内外脊高H,h及脊宽W的尺寸.通过Optiwave软件对SiGe OI脊形光波导进行建模仿真,验证了理论分析和计算的正确性.     

用转移矩阵方法来研究发生在势阱内的量子反射

本文利用转移矩阵方法对两种简单的具有吸引尾的势进行了研究.我们发现反射系数在波矢k→0时R=1,反射率与波矢k在k→0时呈线性关系.这说明在发生阱内量子反射时有利于超冷原子生存,因为超冷原子是低速低能原子.此外,我们可以用一个反射时间变化量Δt来判断量子反射的延迟或者超前.     

Investigation of the Dielectric-Loaded, Ridged Helical Groove Slow-Wave System for the Millimeter Wave TWT

A dielectric-loaded, ridged helical groove slow-wave structure for the millimeter wave traveling wave tube is presented in this paper. The effects of the groove depth, ridge dimensions and the dielectric permitivety on the wave propagating properties and the interaction impedance are investigated in detail. From the analysis, it is indicated that for broader band amplification in a helical groove travelling wave tube, a ridged helical structure with shallow groove and loaded by dielectric with proper relative permitivety may be applied.     

脊加载椭圆波导的多项式表示分析方法

采用Rayleigh-Ritz方法和多项式表示对脊加载椭圆波导的传输特性进行了分析.数值计算与电磁仿真软件结果能很好地符合.研究了不同尺寸对脊波导带宽的影响，对这类结构的优化具有指导意义.     

加脊TEM喇叭初步研究

针对恒阻抗TEM喇叭的上下面板电流分布不对称,采用小反射理论和阻抗渐变思想并通过设计脊结构对恒阻抗TEM喇叭进行了改进,研制了加脊TEM喇叭。仿真及实验研究结果表明:对于脉冲宽度约为1 ns的高斯脉冲,通过加脊在一定程度上改善了恒阻抗TEM喇叭上下面板电流分布的不对称性和E面辐射电场的不对称性;相对于相同口径的恒阻抗TEM喇叭,加脊TEM喇叭作为辐射天线和反射面脉冲天线馈源时系统的主轴远场辐射因子均有提高。     

Analysis of Elliptical Thin Ridged Waveguide

Elliptical waveguides and ridged waveguides have found broad applications in many microwave structures. The elliptical waveguide with double infinite thin ridges has been formulated using the mode-matching method. Exact closed-form expressions for eigenvalue problem of all TE and TM modes are presented. Numerical results suggest that the elliptical ridged waveguides have larger bandwidth than that of circular ones. Supported in part by the National Natural Science Foundation of China under Grant 60532010, and in part by the Scientific Research Foundation for the Returned Overseas Chinese Scholars under Grant 04LXJ01.     

Compositional evolution of lava plains in the Syria-Thaumasia Block,Mars

Tharsis is the most prominent volcanic province on Mars,yet the compositions of lava flows and how composition relates to the development of Tharsis are poorly known.Most of Tharsis is covered with air-fall dust,which inhibits spectroscopic determination of lava mineralogy.The Syria-Thaumasia Block(STB)is a complex tectono-volcanic province closely related to the Tharsis bulge.The lava plains of STB have different emplacement ages,which provide an opportunity to examine whether magma composition changed with the evolution of Tharsis.In this study,we assessed the lava plains using Thermal Emission Spectrometer(TES)data.Using derived physical properties,we targeted dust-free regions from four different-aged geological units’surfaces and determined the mineralogical composition by modeling the average TES surface spectrum from each of the four surfaces.All units have similar mineralogy but the younger two units have elevated abundance of high-SiO2phases.The spatial distribution of wrinkle ridges indicates lava plains of unit HNr(older ridged plains material)and Hr(younger ridged plains material)were emplaced before the rise of Tharsis,whereas Hsl(flows of lower member)and Hsu(upper member)were emplaced after Tharsis uplift was initiated.We show that the magma composition differed in the lava plains of STB after the uplift of Tharsis.This study further characterizes early martian magma composition and evolution.     

Preliminary in situ teeth study of the narrow‐ridged finless porpoises remains using microsynchrotron radiation X‐ray fluorescence and laser ablation inductively coupled plasma mass spectrometry

In recent years, a growing number of the narrow‐ridged finless porpoises were found dead near the Yangtze River estuary. In this region lived two sympatric subspecies, respectively, the East Asian finless porpoise and the Yangtze finless porpoise. So far, it is difficult to distinguish these two subspecies due to their similar shape and unavailable molecular marker. In this work, synchrotron radiation X‐ray fluorescence (SRXRF) and laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) were applied for in situ teeth trace chemical analysis to study subspecies identification and migration near the Yangtze River estuary. Teeth Sr concentration and ⁸⁷Sr/⁸⁶Sr ratios, determined by SRXRF and LA‐ICP‐MS techniques, have potential application in the identification of the finless porpoise subspecies. Only one (Sample S4) of the six samples was concluded as the Yangtze finless porpoise, and the others were the East Asian finless porpoise. This study also proved that the Sr/Ca and Zn/Ca ratios could be used as a useful environmental indicator to detect the migratory history of narrow‐ridged finless porpoises.     

利用海底反射信号进行地声参数反演的方法

针对现有反演方法的缺点,提出了一种基于海底反射信号的地声参数高分辨反演方法.它利用短距离声源在不同深度上发射宽带线性调频信号,采用垂直阵进行接收,首先通过匹配滤波方法提取多径到达信息,然后利用海底反射损失曲线,反演海底表层的声速和密度,最后利用浅底层反射信号估计沉积层参数.由于海水中直达波受到内波的强烈影响,选择海底表面反射作为参考,用以可靠地计算浅底层反射的相对到达时间和幅度,从而估计出沉积层的厚度、速度和衰减系数.通过海上实验,验证了利用浅底层反射信号反演参数的有效性. 关键词： 海底参数 反演 浅底层反射信号     

二维平板光子晶体直波导的制备和光传输特性的测量

利用聚焦离子束刻蚀的方法在SOI(silicon on insulator)基片上制备了W3型二维光子晶体直波导.观察并测量了近红外激光通过光子晶体波导的散射图形和透过谱.实验结果说明，激光在有引入引出脊形波导的光子晶体直波导中具有很好的传输特性. 关键词： 光子晶体波导 光子带隙 脊型波导     

Simulation of sputtering from ion-beam-roughened carbon surfaces

Effects of ion-induced surface roughness on sputtering of amorphous carbon under ion bombardment are studied by means of binary-collision computer simulation in a wide range of incidence angles. Most simulations refer to 1–10?keV Ar ion bombardment, and sinusoidal ripple morphology is assumed. It is shown that surface roughness is a key factor to achieve quantitative agreement with experiment. The simulation results are compared with the analytical estimates of the yield from sine-shaped and ridged surfaces based on continuum models of ion sputtering. Some deviations between the results are discussed.     

Numerical modeling of generalized millimeter-wave transmission media with finite element and transmission line matrix methods

In this paper, a general finite element method as well as a graded-mesh TLM procedure for determining the dispersion characteristics, field distribution, pseudo-impedance and losses of generalized millimeter-wave transmission media are described. These methods cover arbitrary cross-sections and account for realistic features (finite metallization thickness, substrate mounting grooves etc.) that are often neglected in theoretical analysis. Dispersion characteristics and characteristic impedances obtained for dielectrically loaded ridged wave-guides compare well with the available data. Conductor and dielectric losses are also computed for these structures. A modified finline structure called ridged finline is also analysed. The main advantages of this structure are its large monomode bandwidth and reduced dispersion. The cutoff frequencies of bilateral finlines in circular waveguides are also computed.     

Low-loss polymeric optical waveguides with large cores fabricated by hot embossing

A simple low-cost method of fabricating polymeric optical waveguides with large core sizes for plastic optical fibers is presented. The waveguides are fabricated by hot embossing with an ultraviolet-cured epoxy resin stamper. The stamper is fabricated by replication of a rectangular groove mold that is made from silicone rubber replicated from a ridged original silicon master. The master is fabricated by anisotropic etching of (110) single-crystal silicon. Optical waveguides with large core sizes of 100-500 microm have been fabricated, and a low propagation loss of 0.19 dB/cm at 650 nm was achieved.     

A ceramics-free waveguide for ITER ion cyclotron wave system

A ceramics-free waveguide for the high-power International Thermonuclear Experimental Reactor ion cyclotron (ITER IC) system (15-80 MHz), which is a TEM waveguide supported mechanically by T-shaped ridged waveguides, is proposed. The transmission-line theory shows that this waveguide has power handling capability of more than 3 MW, where an optimized antenna impedance is used for the ITER plasma parameters. The transmission line model used for the analysis is verified by the experiments on a one-tenth scale model     

Fundamental Study of Reflection Pulse Oximetry

For the purpose of developing reflection pulse oximetry, we have analyzed the light propagation in tissue to calculate the photon-visit depth for reflected light and to estimate the measured intensities of transmitted and reflected light using the analytical solutions of the photon diffusion equation. The effects of the reflectance of the probe surface have been studied, and a low reflecting surface has been found to provide deeper photon-visit depth than a high reflecting surface for reflection pulse oximetry. Based on analytical estimation, we made reflection type probes, and conducted preliminary experiments to confirm the feasibility of this type of pulse oximetry.     

A New Type of Ultra-Wide Band Conical Antenna Ridged with a Novel Finline Radiator

A new type of ultra-wide band(UWB) conical antennas ridged by a novel taper finline radiator(TFR) used as radiation and receiving of the short pulse are developed. In which, a new UWB feed structure of a coplanar waveguide to finline and a TFR ridge are used initially. The experiment results show the characteristics of high fidelity, high efficiency, and high gain compared with some common broad-band antennas such as the biconical antennas, V-conical antennas, logarithm periodic antennas, and the other TEM horns.     

A Compact 2-D Finite-Difference Frequency-Domain Method for Dispersion Characteristics Analysis of Trapezoidal-Ridge Waveguides

A compact two-dimension (2-D) finite-difference frequency-domain (FDFD) method is used to analyze the dispersion characteristics of single and double trapezoidal-ridge waveguides. The general 2-D FDFD formulation under orthogonal curvilinear coordinate system is derived from the difference form of Maxwell’s equations, and modified difference formulas at the trapezoidal-ridge section are built. After implementing the boundary conditions, the 2-D FDFD formulation is concluded as an eigen equation and then constructed by a highly sparse matrix. By solving the matrix-eigen equation, the dispersion characteristics of the ridged waveguides can be obtained. Computed results are in good agreements with the previously published and simulated ones, which prove the correctness of the method.     

2.45 GHz ECR离子源的微波阻抗匹配

ECR离子源的等离子体阻抗对其微波传输与阻抗匹配设计至关重要。在中国科学院近代物理研究所现有的2.45 GHz ECR 质子源上,对等离子体阻抗进行了测量。首先用水吸收负载代替等离子体负载测量得到了所用微波窗阻抗,然后根据质子源测量数据,推算得到了等离子体阻抗。实验结果表明,脊波导输出端阻抗与后续负载不完全匹配,等离子体阻抗随微波功率变化呈非线性。这些结果为ECR离子源过渡匹配和微波窗的设计提供了参考依据。Plasma impedance of an ECR ion source is important for microwave transmission and impedance matching design. Plasma impedance was measured indirectly with the 2.45 GHz ECR proton source at the Institute of Modern Physics, Chinese Academy of Sciences. In the test, we got microwave window mpedance by using water absorption load instead of plasma load, and the source plasma impedance was derived from the test data with the 2.45 GHz ECR proton source and microwave window impedance. The experimental results show that ridge waveguide output impedance and the subsequent load does not exactly match, plasma impedance variation is nonlinear with microwave power. The achievedresult is useful in the design of ridged waveguide and microwave window.     

Analysis of Bragg reflection waveguides with finite cladding: An accurate matrix method formulation

Ideal Bragg reflection waveguides (BRWs) are assumed to have an infinitely extended periodic cladding whereas in practice, the cladding of BRWs is of a finite extent. Bloch theorem is widely used to analyze the propagation characteristics of the BRWs. Since Bloch theorem is ideally valid only for an infinitely extended periodic medium, its application to study such BRWs is an approximation. We present a matrix method for a more accurate analysis of finite-clad BRWs and estimate the extent of errors involved in the values of the propagation constant obtained by the Bloch wave formalism. The proposed method can be used to obtain the mode effective indices as well as the radiation loss of a finite-clad BRW without resorting to solving any complex transcendental equation. In addition, since the method does not inherently assume a periodic cladding, it can also be used to analyze symmetric multi-channel BRWs, chirped structures and directional couplers.