Diffraction of an H-polarized electromagnetic wave by a circular cylinder with an infinite axial slot

A comparison of three methods of solution for the problem of scattering and diffraction of a transverse electric (TE) polarized plane wave by an infinite circular cylinder having an infinite axial slot is presented. In one method of solution, the aperture field integral equation (AFIE) method, the fields in and around the cylinder are found from the apertureE-field and the Green's functions for the interior and exterior of a cylinder. In the other two methods, the fields are determined from the surface current, which is obtained by solution of theH-field integral equation (HFIE) or theE-field integral equation (EFIE). The field in the aperture of the cylinder is found from the three methods, and the advantages and disadvantages of each method of solution are discussed. In addition, it is also shown that for shell thickness less than 1/20 of a wavelength, the aperture fields do not differ signifcantly from those of an infinitely thin shell cylinder.     

Curved RFID tags for metallic gas cylinders

Presented is a radio frequency identification (RFID) tag antenna designed to fit around the neck of a small gas cylinder and capable of operation at the European and American UHF RFID bands. The design is readable from all directions in the plane of the cylinder neck and is mounted on cheap synthetic rubber (neoprene) of thickness 2 mm with dimensions of 125 x 20 mm. The tag antenna was conjugally matched to the complex impedance of the transponder IC chip.     

The omni microstrip antenna: a new small antenna

The omni microstrip antenna is a microstrip-shorted quarter-wave resonator that is wrapped around a cylinder. It is an electrically short antenna, and it can be made to radiate an omnidirectional pattern normal to the axis of the cylinder. Equations governing the design of the antenna are given along with a method of excitation. An example of a design at 41.4 MHz is given, and experimental results are reported.     

Contribution to the understanding of pattern coverage of an open-circuited microstrip wraparound antenna acting at half-wavelength resonance

In the case of an open-circuited microstrip antenna wrapped around a conducting cylinder and acting at a half-wavelength resonance, we studied the influence on the pattern coverage of various parameters, such as the dielectric constant of the substrate and cylinder diameter related to the wavelength. Some contradictions with another recent paper appear and are explained.     

热圆柱体表面温度的干涉法测量

介绍一种利用干涉原理测量热圆柱体表面温度的方法,首先,在对圆柱体周围空气的温度和折射率分布特点进行分析的基础上,建立Fizeau等厚干涉系统,调整光路使干涉条纹稳定且等间距。然后,将圆柱体水平放置于干涉光路中加热,记录物体加热前后干涉条纹图像,利用曲线拟合和轮廓跟踪算法对图像进行处理,进而计算出紧靠圆柱体表面处空气的折射率。最后,利用热圆柱体附近空气温度分布的特点,以及空气温度和折射率之间的关系,确定圆柱体的表面温度。结果表明：此方法的测量精度不低于1％,温度分辨率不低于0．1K。     

Far field radiated by short-circuited microstrip antenna acting at a quarter-wavelength resonance

Using electric and polarisation current distributions, known from transmission-line-model analysis, we have determined the far field radiated by a short-circuited rectangular microstrip antenna acting at a quarter-wavelength resonance. An experimental verification for such a radiating strip wrapped around a conducting cylinder is given.     

Optimal excitation of multiapplicator systems for deep regionalhyperthermia

A method is proposed for determining the excitation amplitudes and phases of the elements of electromagnetic multiapplicator systems for optimizing the specific absorption rate (SAR) distribution around a deep-seated tumor. In this method, the ratio of the power dissipated in the tumor to a weighted summation of the powers supplied to the surrounding regions is optimized. The optimization procedure is combined with a recently proposed effective technique for analysis of various electromagnetic scattering and interaction problems. The general principle is applied to a two-dimensional problem of a piecewise homogeneous cylinder heated by an array of electric current filaments placed outside the cylinder. Numerical simulations are performed to check the effectiveness of the approach. The results demonstrate that using this optimization method, improved SAR distributions can be achieved. The extension to three-dimensional configurations is discussed.     

Focused Heating in Cylindrical Targets: Part I (Short Papers)

The analytical basis of a method to focus the electromagnetic power into a conductive cylinder is described. The scheme, & currently being used by others, is to locate a number of horn apertures around the periphery. An explicit expression is obtained for the required excitation of the apertures for a two-dimensional model.     

Visualization of electric fields around a biological body

A system was developed that can visualize the spatial distribution of the ELF (extremely low frequency) electric field around an object with a complex shape such as a biological body. A mechanical X- Y scanner controlled by a microcomputer moves an optical sensor, automatically scanning the space around the object. The measured data are processed and the field distribution is represented in a color distribution pattern. Using an object with a simple shape such as a cylinder, the accuracy of the measurement was confirmed by comparison to a numerical calculation. The field distributions around experimental animals (a rat and a cat) were measured and it was shown that a conductor model can be used instead of a living body in the ELF range. The field distribution around a human model was measured in various postures, showing reasonable agreement with measurements for a real human body standing under transmission lines     

红外激光光声光谱气体传感谐振腔分析

设计制作了适合中红外激光光声光谱气体检测用的圆柱形光声腔,采用有限元法对其声信号的传输和探测进行了模拟分析并与实际测量结果进行了系统的比较.结果表明此光声腔中的二阶纵模在4.2KHz附近具有最大的共振幅度和适中的Q值,十分适合中红外光声光谱气体传感应用.     

光纤轴角传感器设计

基于反射原理的光纤角度传感特性，利用输入光纤光束照射可以绕偏心轴转动柱型反射面，其反射光斑在入射光纤端平面所在的接收平面上呈近椭圆状。位于入射光纤两侧的接收光纤耦合光斑能量。接收面上光斑的长短轴、中心、面积都是轴角的函数。以接收光功率与入射光功率比映射轴角曲线关系具有高的共模抑制比。     

The shielding of a plane wave by a cylindrical array of infinitely long thin wires

A plane wave is considered to be incident upon a cylindrical array of infinitely long perfectly conducting thin wires. The wave is assumed to have no magnetic field component in the direction of the wire axes. Exact expressions are found for the currents excited on the wires-and for the total electric and magnetic fields. Numerical computations are made to determine the currents on the wires and the fields inside the array. It is discovered that an important parameter is the number of wires in the array divided by the number of wavelengths that can be wrapped around the cylinder. If this parameter is large enough, the current distribution on the wires resembles that of a solid conducting cylinder, and the array of wires tends to behave like an electromagnetic shield. For smaller values of the parameter, the current distribution can be quite different, and the field inside the array may even be enhanced.     

结构无序对8重准晶光子晶体带隙特性的影响

采用时域有限差分法(FDTD)对介质柱构成的8重准晶光子晶体(PQC)的光子带隙(PBG)特性进行了研究,分别讨论了介质柱尺寸无序和位置无序对其带隙宽度、位置和各向同性的影响.数值模拟结果表明,随着介质柱尺寸无序和位置无序的增大,8重准晶光子晶体带隙的中心频率向低频方向移动,带隙的相对宽度均变窄,但介质柱尺寸无序对带隙的影响远大于位置无序的影响.当尺寸无序达到介质柱半径的一半时,带隙完全消失,而对于相同大小的位置无序,相对带隙宽度只改变了1%;同时,在较大结构无序范围内,带隙的各向同性也能很好地保持.     

Multiply Reflected Gaussian Beams in a Circular Cross Section

A well-collimated beam reflected repeatedly within a circular cross section undergoes periodic focusing and defocusing. This behavior is of interest for tracking of beams around a type of acoustic surface wave disk delay line, and it also relates to beam monitoring after oblique injection into the endface of a multimode optical fiber. The problem is analyzed by considering first the field excited by an isotropic line source inside a dielectric cylinder, and then converting this to Gaussian beam excitation by assigning a complex value to the source coordinate location. Because the wavelength is small compared to the cylinder radius, ray-optical methods are employed to construct the solution, with inclusion of such novel ingredients as the lateral ray shift on a curved boundary. Results are obtained for the amplitude and phase of the ray and beam field and for such beam parameters as the location of the focus the minimum beam width and the rate of beam divergence between successive reflections.     

Frequency-derived distributed optical fibre sensing: signal-frequency downshifting

A method for downshifting the frequency of polarisation-optical time domain reflectometry signals has been demonstrated by optically mixing backscattered light from two semiconductor lasers simultaneously launched into a single mode fibre with bending birefringence. For lasers with wavelengths of 670 and 780 nm and 140 m of the fibre wound around a cylinder of radius 7.5 cm, approximately five downshifted beat cycles were obtained.<>     

一种宽带全向圆极化天线简

 基于环天线-偶极子模型,本文提出一种宽带全向圆极化天线.天线包含四对围绕圆柱放置的倾斜振子和一个宽带馈电网络.每对振子包含一个主辐射振子和一个用以增加带宽的寄生振子.馈电网络包括四个宽带巴伦和一个阻抗匹配电路.实验结果表明,该天线15-dB回波损耗带宽和3-dB轴比带宽分别为31%（1.68-2.31GHz）和30%（1.7-2.3GHz）,水平面不圆度小于1dB.     

激光横向剪切干涉应用于温度场的测量

根据大空间自然对流水平圆管上部上升的羽状烟柱区不符合边界层假设而导致各种解之间差异的问题,提出了利用横向大剪切量干涉实验装置来实现温度场的光学测量,得到了自然对流水平圆管在不同壁温时的实时条纹。利用彩色条纹图像中RGB原始数据中的R分量的峰、谷极值点的坐标来识别明、暗条纹并得到了全场的级数分布,以此反演出全场温度分布。实验结果表明:当圆管直径d为15.6mm、剪切量s为24.2mm时,实验得到的干涉条纹类似于利用全息干涉或马赫-曾得干涉原理得到的无限宽简单条纹;干涉条纹分辨率达到75.64pix/mm;利用横向大剪切量干涉法能够准确快速地反演全场温度分布,为工程热物理分析提供相关数据。     

隐形斗篷的研究

基于坐标变换理论设计了菱形、不规则四边形和扇形隐形斗篷。利用COMSOL Mul-tiphysics对其进行仿真得到,覆盖斗篷后电磁场可以"拐弯"绕着物体走,斗篷内部区域未受到电磁场干扰,隐形效果均得到了较好的证实。这三种形状的隐形斗篷比圆柱形和球形斗篷更为常见,因而在减少物体的雷达散射截面(RCS)方面具有更为广泛的实用性。     

金属环封装低频光纤布拉格光栅振动传感系统研制

研制了一种金属环封装的单柱体芯轴式光纤布拉格光栅(FBG)振动传感器,搭建了基于非平衡迈克耳逊干涉仪相位载波调制(PGC)解调技术的FBG振动传感器解调系统,实现了低频振动信号的高精度实时解调,并分析了各参数对传感器谐振频率和灵敏度等特性的影响。实验结果表明,研制的FBG振动传感器谐振频率为388Hz,在10～200Hz频率范围内,传感器的加速度灵敏度约为81pm/g,且加速度响应平坦,起伏小于1dB,与理论分析结果基本一致。研制的振动传感器可实现200Hz以下低频振动信号的实时检测,解调系统的波长检测精度为1.07×10-3 pm,最小可检测加速度为1.3×10-5 g。     

内置金属/电介质同心圆柱的金属孔阵列结构强透射特性

采用有限时域差分(FDTD)法研究了内置金属/电介质同心圆柱结构的材料属性、半径及其相对高度对金属孔阵列强透射特性的影响.发现该结构与内置单一金属、单一电介质和电介质/金属三种不同的同心圆柱结构相比较,光的透射性能得到显著的增强;这种内置金属/电介质同心圆柱结构具有进一步增强表面等离激元与局域表面等离激元共振耦合作用.结果表明,金属、电介质的材料属性对强透射特性影响明显,当金属圆柱为Au、电介质圆柱折射率较小时,其透射性能较好;圆柱半径是影响透射率与共振峰位置的主要因素,半径越大,共振峰红移越明显,但其透射率先增大而后持续减小.同时,金属/电介质圆柱的相对高度也影响透射率大小,当金属圆柱高度为60 nm时,其透射性能较好.