Standard linear antennas, 30 to 1000 MHz

It is demonstrated that the insertion loss between pairs of thin, linear antennas may be calculated using fairly simple equations that are generally considered to be good engineering approximations. Although the insertion loss calculation does not involve antenna gain directly (some measurements are actually made in the near-field where gain is not defined), the result is precisely the quantity obtained using the antenna gains in Friis's transmission formula, assuming the mismatch losses are zero. Therefore, the antenna gain product is implicit in the more general insertion loss equations. The particular measurement of insertion loss used here yields a quantity called site attenuation by electromagnetic compatibility engineers. A close agreement between measured and calculated data provides confidence in the site attenuation calculations when the site is essentially perfect, and provides confidence in the gain product of the antenna pair calculated using basically the same equations as those used for insertion loss. It is assumed that one-half of the mean value of the difference between the calculated and measured data is a good estimate of individual antenna performance. For the antennas described here, this measure of performance is typicallylE0.05dB and on the outside,iE0.42dB.     

传输/反射法测量微波吸收材料电磁参数的研究

通过从HP8722ET网络分析仪提取散射参数,研究了以乙丙橡胶为基体,磁性材料羰基铁粉为吸收剂的微波吸收材料同轴测试样品在同轴夹具中位置L1与样品长度L2的测量误差对其电磁参数测量结果的影响,提出了减小测量误差的方法.结果表明：在2.6～18GHz范围内,L1存在-0.08mm的绝对误差使得相对介电常数实部ε′与虚部ε″,相对磁导率实部μ′与虚部μ″的测量值与真实值的最大相对误差值分别达3.1%、168.0%、3.7%和-10.0%;L2存在-2%的相对误差使得ε′、ε″、μ′和μ″的测量值与真实值的最大相对误差值分别达3.5%、30.0%、4.0%和5.0%.采用光学显微镜的静态方法测量样品长度和使用辅助定位夹具可以减小测量误差,提高电磁参数测试结果的精确度。     

30MHz～1000MHz电场辐射干扰测试中测量不确定度的评估方法

文章以CISPR 16-4:2002为依据,讨论了在标准3m法电波暗室中进行30MHz-1000MHz电场辐射干扰测试时测量不确定度的评估方法.     

A comparison of electric field-strength standards for the frequencyrange of 30-1000 MHz

Published results about site attenuation and transmission loss measurements as well as antenna factor calculations and calibrations are summarized. The antenna types discussed are precision dipoles, a microstrip patch antenna, open-ended waveguides, and horn antennas as well as TEM-cells. The best values for agreement between theory and experiments that were reported for the transmission losses were in the range of 0.25-0.4 dB. An experimental comparison between precision reference dipoles and a TEM-cell that was performed in the Seibersdorf calibration laboratory is described with deviations of no more than 0.15 dB in the antenna factor or field-strength     

Higher order absorbing boundary conditions for thefinite-difference time-domain method

Higher-order absorbing boundary conditions are introduced and implemented in a finite-difference time-domain (FDTD) computer code. Reflections caused by the absorbing boundary conditions are examined. For the case of a point source radiating in a finite computational domain, it is shown that the error decreases as the order of approximation of the absorbing boundary condition increases. Fifth-order approximation reduces the normalized reflections to less than 0.2%, whereas the widely used second-order approximation produces about 3% reflections. A method for easy implementation of any order approximation is also presented     

解析25～1000MHz短距离设备电磁兼容欧洲标准

介绍短距离设备欧洲标准ETSI EN 300 220-1 V2.3.1的测试模型选取和测试条件;详尽分析频率误差、平均传导功率、有效辐射功率、扩频调制、瞬态功率、临近信道功率、调制带宽、杂散发射、频率稳定性和占空比等发射机参数,以及灵敏度、LBT阈值、临近信道选择性、阻塞性能、杂散抑制和接收机杂散等接收机参数;并对全电波暗室、半电波暗室和开阔场的试验场地、试验布置和测试方法进行分析说明。     

用于30MHz～1GHiz电磁辐射骚扰测量的全电波暗室场地校验方法

详细介绍了最新国际标准CISPR 16-1-4:2004第5.8条给出的两种评估方法-场地参考法(site reference method)和归一化场地衰减法NSA.为评估全电波暗室的性能提供重要技术依据.     

用于30MHz～1GHz电磁辐射骚扰测量的全电波暗室场地校验方法

详细介绍了最新国际标准CISPR16-1-4∶2004第5.8条给出的两种评估方法—场地参考法(sitereferencemethod)和归一化场地衰减法NSA。为评估全电波暗室的性能提供重要技术依据。     

Higher order formulation of absorbing boundary conditions for finite-difference time-domain method

A simple formulation of absorbing boundary conditions with higher order approximation is proposed for the finite-difference time-domain (FD-TD) method. Although this formulation is based on the third order approximation of the one-way wave equations the authors have succeeded in reducing it to an equation in a form quite similar to the second order approximation.<>     

A simple method for characterizing the RF properties of high-temperature superconductive materials

A simple method using a resonant strip in a rectangular waveguide has been devised for superconductive material characterization. The method has the advantages of simplicity; and it requires only a small piece of the superconductive material. The resonant frequency of the superconductive strip can be predicted theoretically.     

On the synthesis of exact free space absorbing boundary conditionsfor the finite-difference time-domain method

An exact and nonlocal analytical absorbing boundary condition (ABC) for use in the finite-difference-time-domain (FDTD) method is proposed. The ABC requires no assumptions regarding a minimum spacing between scatterers and the artificial termination planes, and is not a function of the angle of an incident wave component with respect to the ABC truncation plane. Hence the size of the volumetric computational domain may be kept to a minimum. The derivation of the ABC makes use of the surface equivalent theorem and the vector potentials after an analytical frequency to time domain transformation. The new ABC contains derivatives with respect to both time and space, and may be approximated in the FDTD method via appropriate finite difference approximations     

A frequency-dependent finite-difference time-domain formulation for dispersive materials

The traditional finite-difference time-domain (FDTD) formulation is extended to include a discrete time-domain convolution, which is efficiently evaluated using recursion. The accuracy of the extension is demonstrated by computing the reflection coefficient at an air-water interface over a wide frequency band including the effects of the frequency-dependent permittivity of water. Extension to frequency-dependent permeability and to three dimensions is straightforward. The frequency dependent FDTD formulation allows computation of electromagnetic interaction with virtually any material and geometry (subject only to computer resource limitations) with pulse excitation. Materials that are highly dispersive, such as snow, ice, plasma, and radar-absorbing material, can be considered efficiently by using this formulation.<>     

The time-domain discrete Green's function method (GFM)characterizing the FDTD grid boundary

For a given FDTD simulation space with an arbitrarily shaped boundary and an arbitrary exterior region, most existing absorbing boundary conditions become inapplicable. A Green's function method (GFM) is presented which accommodates arbitrarily shaped boundaries in close proximity to a scattering object and an arbitrary composition in the exterior of the simulation space. Central to this method is the numerical precomputation of a Green's function tailored to each problem which represents the effects of the boundary and the external region. This function becomes the kernel for a single-layer absorbing boundary operator, it is formulated in a manner which naturally incorporates numerically induced effects, such as the numerical dispersion associated with the FDTD scheme. The Green's function is an exact absorber in the discretized space. This property should be contrasted with other methods which are initially designed for the continuum and are subsequently discretized, thereby incurring inherent errors in the discrete space which cannot be eliminated unless the continuum limit is recovered. In terms of accuracy, the GFM results have been shown to be of a similar quality to the PML, and decidedly superior to the Mur (1981) condition. The properties of the GFM are substantiated by a number of numerical examples in one, two, and three dimensions     

A method for characterizing carbon nanotubes

High-resolution transmission electron microscopy and electron energy-loss spectroscopy of a multi-walled carbon nanotube (MWCNT) at elevated temperatures were studied. Although the observation was carried out at 200 kV, the crystal structures of the MWCNT were observed without introducing defects. In addition, contamination on the MWCNT, such as nanobubbles, was removed during the observation at 600 degrees C. In this paper, we report the observation conditions and experimental results. The experimental results obtained both at 600 degrees C and at room temperature were compared.     

A finite-difference time-domain method applied to anisotropicmaterial

The popularity of the finite-difference time-domain (FDTD) method stems from the fact that it is not limited to a specific geometry and it does not restrict the constitutive parameters of a scatterer. Furthermore, it provides a direct solution to problems with transient illumination, but can also be used for harmonic analysis. However, researchers have limited their investigation to materials that are either isotropic or that have diagonal permittivity, conductivity, and permeability tensors. The authors derive the necessary extension to the FDTD equations to accommodate nondiagonal tensors. Excellent agreement between FDTD and exact analytic results is obtained for a one-dimensional anisotropic scatterer     

A disk-loaded thick cylindrical dipole antenna for validation of anEMC test site from 30 to 300 MHz

We propose a new broad-band, short (80-cm-long) disk-loaded thick cylindrical dipole (DTCD) antenna for validation of an electromagnetic compatibility (EMC) test site for the frequency range between 30-300 MHz. In order to achieve broad-band characteristics, we have chosen a thick dipole as DTCD element. Disk loading has been applied to make this dipole shorter. To eliminate any ambiguity in balun characteristics, a commercially available hybrid junction is used as an antenna balun. Thus, the DTCD proposed in this paper is a very short, simple, and well-defined broad-band antenna that covers the frequency range between 30-300 MHz. The DTCD has an azimuthally symmetrical radiation pattern and, thus, is very well suited for the validation of an EMC test site. This paper presents the DTCD antenna characteristics such as input impedance, antenna gain, antenna factor, and classical site attenuation, which are calculated by use of the method of moments (MoM). These theoretical antenna factors and classical site attenuations of the DTCD are compared with experiments over the frequency range of 30-300 MHz. They agree with each other to within ±1 dB in antenna factor and to within ±2 dB in site attenuation. Our preliminary investigation indicates that an additional DTCD (25 cm long) can cover the frequency range of 300-1000 MHz. Therefore, only two DTCDs will be needed for very accurate calculable classical site attenuation values in order to validate an EMC test site for the entire frequency range between 30-1000 MHz     

Development and characterisation of tissue equivalent materials for frequency range 30-300MHz

Two formulations for tissue equivalent liquids are presented and characterised in terms of dielectric properties in the frequency range 30-300 MHz. The purpose is to provide viable options for consideration by the standardisation bodies dealing with the assessment of exposure to electromagnetic sources in that frequency range     

30～1000 MHz辐射骚扰测量的不确定度分析与研究

为能正确评定30～1 000 MHz辐射骚扰测量设备和设施的不确定度,针对一些评定有难度的输入量进行了解释、分析和研究,这有助于理解CISPR 16-4-2:2018中给出的有关30～1 000 MHz辐射骚扰测量设备和设施的不确定度评定的内容,可为30～1 000 MHz辐射骚扰测量设备和设施的不确定度的评定提供指导.     

A triple-through method for characterizing test fixtures

Test fixtures for evaluating microwave components usually consist of two unmeasurable sections, each having, for example, one coaxial and one microstrip terminal. A method is proposed for evaluating the S -parameters of these sections through three conventional reflection/transmission measurements. The method is based on the use of an auxiliary two-port. A microstrip standard is not needed, except for a load which is necessary if the SWR (standing wave ratio) of the auxiliary two-port is not low enough. Only one reflection measurement with a load has to be performed on the auxiliary two-port, and even this may be cancelled if the two-port is a transition with low SWR. The method is broadband, frequency-insensitive, and extendable to other media such as waveguide and finline     

解析401～402MHz与405～406MHz短距离设备电磁兼容欧洲标准

介绍了短距离设备欧洲标准ETSI EN 302 537-1 V1.1.2的测试条件、电源要求和环境要求,分析了辐射测试场地和测试布置。最后,详尽解读了401～402 MHz与405～406 MHz频段超低功耗医学设备的频率误差、发射带宽、有效辐射功率、杂散发射、低电压条件下的频率稳定度、基于低功率低占空比条件的频谱访问等发射机参数要求,以及接收机杂散的要求。