Absorbing Elements Based on a Uniform Resistive Film for the Implementation of a Wide Range of Radio Signal Power Attenuations

Russian Microelectronics - Rectangular and complex-shaped absorbing elements based on a uniform resistive film are used for constructing waveguide, coaxial, and microstrip attenuators. A decrease...     

An Electromagnetic System for Studying the Responses of Aquatic Organisms to Weak Electric and Magnetic Fields

Recent evidence suggests use of electric and magnetic cues as orientational aids to long-distance migration by fishes. A simple laboratory apparatus is described which accurately reproduces the electromagnetic fields an aquatic organism might naturally experience.     

城市广电网络宽带发展的形势和应对

宽带已成为广电网络转型发展的重要业务,分析了城市广电网络宽带发生、发展和当前所面临的形势,并从应用实例出发,对广电宽带下一步发展提出相应的建议和措施,以寻求突破的对策。     

An Efficient Technique for Computing the Potential Green's Functions for a Thin, Periodically Excited Parallel-Plate Waveguide Bounded by Electric and Magnetic Walls

An efficient formulation is described for calculating all vector and scalar potential Green's functions for a thin, infinitely long waveguide with periodic excitation. The Green's functions are represented by the first few terms of the modal expansion plus a quasi-static correction. This allows one to compute the Green's functions over a wide band of frequencies with little additional effort over that required for a single frequency. An attractive feature of the method is that the l/R free-space singularity exhibited by the potentials is explicitly extracted in the lowest order quasi-static term. Tfris is convenient for evaluating method-of-moments self-term contributions in closed form. The Green's functions have application for problems involving stripline structures such as Rotman lenses.     

吸收材料涂层俘获和吸收微波信号的匹配条件

本文应用电磁场的基本理论,详细地研究了微波信号投射到吸收材料涂层上被完全俘获和吸收的匹配条件,导出解析匹配条件诸参量间对应关系的理论公式,并进行了分析和讨论,为微波吸收材料涂层的设计提供了可靠的理论依据。     

SDH微波接力通信系统差错性能指标的分配和预测方法

本文根据ＩＴＵ－ＴＧ．８２６建议和ＩＴＵ－Ｒ有关文件，分析了Ｇ．８２６指标在ＳＤＨ微波接力通信系统中的分配方法；提出了ＳＤＨ微波接力通信系统差错性能指标的预测方法；介绍了在ＳＤＨ微波接力通信系统中主要的抗衰落措施及其对差错性能指标的改善效果。     

VHF/UHF天线宽带匹配网络的优化设计与实验研究

本文系统地研究了VHF/UHF天线宽带匹配网络的设计与制作.提出遗传算法与模拟退火法相结合的优化设计方法,解决VHF/UHF天线宽带匹配网络制作过程中元件值随频率较大变化引发的难题.最后,利用该方法研制了30~450MHz全向宽带小型化天线的宽带匹配网络.实验表明,带内VSWR＜3.0,且计算结果与测试结果十分吻合.     

Matrix Algorithm for Calculation of the Reflection and Transmission Coefficients for the Incidence of Two Counterpropagating Waves on a Multilayer Structure

Journal of Communications Technology and Electronics - An algorithm is proposed for implementation of the matrix method for the problem of the incidence of two counterpropagating waves on a stepped...     

日用管状电热元件标准及规则换版解读

今年,《日用管状电热元件》的标准JB/T 4088-1999进行了更新换版并开始实施,随后CQC依据新标准对相应的认证规则进行了更新。该文对新旧版本的标准及认证规则进行了详细的比较,通过对两部分差异的说明,来解读目前国内的日用管状电热元件认证体系,以期对业内需要进行相关认证的企业起到一定的指导作用。     

山西广电传输网长距离传输数字微波信号的工程实践

山西广播电视无线传输网采用数字微波作为全省广播电视干线网的传输手段,主要以提高传输效率和传输质量的各种抗衰落技术手段为中心,阐述了空间分集、频率分集、增加直放站等技术对长距离传输微波信号的作用和效果,为干线网中数字微波信号的长距离传输与安全播出提供了很好的解决办法。     

电偶极子和磁偶极子场分布相似性的一种解释

电偶极子电场与磁偶极子磁场具有相似的空间分布。然而,这种相似性并非显而易见：电偶极子由一对等量异号电荷组成,而磁偶极子则是一个电流回路。本文从矢量场边值问题的唯一性定理出发,得出了面散度源和面旋度源产生的矢量场分布的一种等价关系,进而对电偶极子电场与磁偶极子磁场空间分布的相似性进行了解释。     

a Compact Waveguide "Resolver" for the Accurate Measurement of Complex Reflection and Transmission Coefficients Using the 6-Port Measurement Concept

The theory of an optimum 5-port network for measuring complex reflection and transmission coefficients is developed. A compact realization in waveguide is described which allows these quantities to be determined over waveguide bandwidths from the measurements of two referenced power levels.     

A Comparison of Electrically Short Bare and Insulated Probes for Measuring the Local Radio Frequency Electric Field in Biological Systems

The problems associated with measuring the local electric field in a medium with spatally inhomogeneous electrical constitutive parameters like biological tissue are discussed. Simple theoretical analyses that describe the operation of electrically short bare and insulated electric field probes in a dissipative medium are presented. The conditions that must be satisfied for each of these probes to have an electric field response that is independent of the electrical constitutive parameters of the surrounding tissue are determined. The results of a systematic experimental study of both types of probes are presented. In the study the probes were immersed in a succession of liquids with dielectric properties similar to those for biological tissues at radio frequencies.     

The Influence of Substitution with Aluminum on the Field of Effective Magnetic Anisotropy and the Degree of Magnetic Texture of Anisotropic Polycrystalline Hexagonal Ferrites of Barium and Strontium for Substrates of Microstrip Devices of Microwave Electronics

Russian Microelectronics - This article discusses the influence of substitution with Al3+ ions on the field of the effective magnetic anisotropy HAeff and the degree of magnetic texture f of...     

Gd2O(CO3)2 · H2O Particles and the Corresponding Gd2O3: Synthesis and Applications of Magnetic Resonance Contrast Agents and Template Particles for Hollow Spheres and Hybrid Composites

The solution approach was employed to yield multifunctional amorphous Gd₂O(CO₃)₂ · H₂O colloidal spheres by reflux of an aqueous solution containing GdCl₃ · 6H₂O and urea. By elongating the reaction time, crystalline rhombus‐ shaped Gd₂O(CO₃)₂ · H₂O with at least 87% yield could be formed and were also accompanied by some rectangular particles. High‐resolution synchrotron powder X‐ray diffraction provides crystal structure information, such as cell dimensions, and indexes the exact crystal packing with hexagonal symmetry, which is absent from the Joint Committee on Powder Diffraction Standards file, for the crystalline rhombus sample. Particle formation was studied based on the reaction time and the concentration ratio of [urea]/[GdCl₃ · 6H₂O]. After a calcination process, the amorphous spheres and crystalline rhombus Gd₂O(CO₃)₂ · H₂O particles convert into crystalline Gd₂O₃ at temperatures above 600 °C. For in vitro magnetic resonance imaging (MRI), both Gd₂O(CO₃)₂ · H₂O and Gd₂O₃ species show the promising T₁‐ and T₂‐weighted effects and could potentially serve as bimodal T₁‐positive and T₂‐negative contrast agents. The amorphous Gd₂O(CO₃)₂ · H₂O contrast agent further demonstrates enhanced contrast of the liver and kidney using a dynamic contrast‐enhanced MR imaging (DCE‐MRI) technique for in vivo investigation. The multifunctional capability of the amorphous Gd₂O(CO₃)₂ · H₂O spheres was also evidenced by the formation of nanoshells using these amorphous spheres as the template. Surface engineering of the amorphous Gd₂O(CO₃)₂ · H₂O spheres could be performed by covalent bonding to form hollow silica nanoshells and hollow silica@Fe₃O₄ hybrid particles.