Modeling of Microwave Images of Buried Cylindrical Objects

Tomographic methods of image reconstruction of two-dimensional cross-sections of volumetric objects in millimeter wavelengths band are suggested and considered. It is shown that in the frequency band under consideration, the images of investigated objects may be obtained by first-order diffraction tomography method (Born, Rytov or high frequency approximation of the first-order for scattered electromagnetic field).     

Modeling of the Bistatic Electromagnetic Scattering From Sea Surfaces Covered in Oil for Microwave Applications

This paper describes the influence of oil pollution over sea surfaces on the height spectrum and the height autocorrelation function of rough surfaces. An oil slick damps the capillarity waves of the surface height spectrum and reduces the root mean square slope of the surface. These modified functions then have an influence on the radar cross section (RCS) from contaminated sea surfaces. The bistatic RCS of the contaminated sea surface is then presented by comparison with a clean sea: results from a benchmark numerical model are presented and compared with a new semiempirical model using the geometric optics approximation and then the first-order smallslope approximation.     

微波站电磁环境测试

讨论微波站电磁环境测试系统的组成和设备参数，指出测试过程中需要注意的问题以及系统灵敏度的计算方法。     

Interaction of Electromagnetic Waves with Cylindrical Plasma

Exact numerical solutions are given for the interaction of a plane, electromagnetic wave with a cylindrical plasma. The incident wave is normal to the plasma axis and both TE and TM polarizations are considered. The electron density profile is represented by a Gaussian curve consistent with flow-field calculations for wakes and jets. Transmitted and scattered amplitudes are evaluated as functions of the polar angle and plasma parameters. The data are compared with previous theoretical and experimental work. [17],[18] Parabolic electron density profiles are also investigated and contrasted with the Gaussian results. The sharp cutoff in a parabolic profile has a significant effect on the electromagnetic interaction. Applications to microwave diagnostics are discussed including a new bistatic method.     

Review of New Developments in the Modeling of Lightning Electromagnetic Effects on Overhead Lines and Buried Cables

In the last 20 years, the widespread use of sensitive electronic devices has increased the interest in transients, in particular those caused by lightning (direct and/or indirect). After a short review of the modeling methods achieved in the last 25 years for indirect lightning electromagnetic effects and the validation of these models using electromagnetic pulse simulators and triggered lightning, this paper focuses on four significant new developments in this field achieved in the last years. They concern the decontamination of the natural lightning current from measurements on elevated structures, the possibility of using statistical methods to infer lightning current values from electric field measurements of lightning-detection systems, and the calculation of field-to-transmission line coupling to complex networks and to shielded cables. These numerical calculations today permit approximative solutions and effect orders of magnitude helpful for a correct electromagnetic compatibility design for very complex configurations to be obtained.     

Electrical Impedance Tomographic Imaging of Buried Landmines

A prototype confirmation landmine detector, based on electrical impedance tomography (EIT), which can operate under realistic environmental conditions, has been developed. Laboratory and field experiments demonstrated that it is possible to reliably reconstruct, on the scale of the electrode spacing (ES) (in width and depth), conductivity perturbations due to a shallow buried antitank mine or a similar object in a variety of soils (black earth, clay, sand) down to depths equal to the dimensions of the object (1–1.5 ES, equivalent to 14–21 cm for a 64-electrode 1 m$times$1 m array). These represent the first EIT images of real landmines computed from measured data. Occasional problems were encountered with the electrical contact in very dry soils, with excessive insertion pressure being required for reliable electrode contact. However, poor contacts could be detected, and the offending probe was either reinserted or compensation was applied. A matched filter detection algorithm based on a replica of the object of interest was developed and shown to effectively reduce the false alarm rate of the detector. EIT is especially suited for wet lands and underwater, where other mine detectors perform poorly. Experiments in a water-and sediment-filled tank have demonstrated that detection of minelike objects in such an environment with a submerged array is feasible. These experiments represent the first EIT measurements of targets using an electrode array submerged underwater. EIT may also have an application in locating intact mines in the berms formed by mine-clearing equipment. The EIT sensor head could be made cheaply enough to be disposable and remotely inserted to improve safety.     

柱状结构中多层各向异性吸波材料的电磁分析

通过对圆柱状结构中多层各向异性薄层吸波材料的电磁分析－柱体由金属柱芯和包围其外的多层各向同性介质材料组成,在各层之间和外表面涂覆各向异性薄层。考虑各薄层的输入阻抗,得出曲面结构内部及表面涂覆各向异性吸波材料散射场。根据级联矩阵和算法,在一定波段上进行ＲＣＳ（Ｒａｄａｒ Ｃｒｏｓｓ Ｓｅｃｔｉｏｎ）减缩,获令人满意的计算结果。     

Electromagnetic Field Penetration into a Cylindrical Cavity

For an E-polarized plane wave incident on a perfectly conducting cylindrical shell having a longitudinal slit aperture, the fields inside the cavity are determined by a numerical solution of the E-field integral equation. Selected data are presented and the first few complex frequency (SEM) singularities are determined for a variety of aperture sizes.     

Modeling of Cylindrical Pin-Fin Heat Sinks for Electronic Packaging

Analytical models are developed for determining heat transfer from in-line and staggered pin-fin heat sinks used in electronic packaging applications. The heat transfer coefficient for the heat sink and the average temperature of the fluid inside the heat sink are obtained from an energy balance over a control volume. In addition, friction coefficient models for both arrangements are developed from published data. The effects of thermal conductivity on the thermal performance are also examined. All models can be applied over a wide range of heat sink parameters and are suitable for use in the design of pin-fin heat sinks. The present models are in good agreement for high Reynolds numbers with existing experimental/numerical data.      

转台模式的近场微波成像研究

针对转台模式的这场微波成像进行了深入研究。首先给出了转台模式下图像函数（描述目标的几何特征）与球投影的积分变换关系，并导出了图像函数的精确解。然后从线性系统的角度出发，研究了理想情况和实际情况下转台模式近场微波成像的分辨特性，理想情况下成像系统的点扩散函数（ＰＳＦ）就是狄拉克－函数。ＰＳＦ的数值模拟结果表明：实际情况下，扫描频带越宽分辨率越高。     

Mode Charts for Cylindrical Microwave Resonators (Program Descriptions)

This program calculates, prints, and plots the data for mode charts. Frequency range, cavity parameters, graph size, grid spacing, and required modes are all user specified.     

Electromagnetic Absorption in Multilayered Cylindrical Models of Man

The absorption characteristics of multilayered cylindrical models of man irradiated by a normally incident electromagnetic plane wave are investigated. Numerical calculations for a specific skin-fat-muscle cylindrical model of man predict a layering resonance at 1.2 GHz with an average specific absorption rate (SAR) about double that calculated for the corresponding homogeneous model. The layering resonance frequency is found to be the same for incident waves polarized parallel and perpendicular to the cylinder axis. The effects of layers on whole-body absorption by man are determined by averaging the effects obtained for many combinations of skin and fat thicknesses. Absorption effects due to clothing are also investigated.     

圆柱螺旋线的时域电磁场

给出一个单连通的空间电流线圈在远区辐射的的时域电磁场，应用等效性原理和场的迭加性，求出圆柱螺旋天线的辐射场分析。     

Dispersion Characteristics of a Cylindrical Electromagnetic Band Gap Structure

In this letter, a new analytical expression for the dispersion equation of radially periodic structures is derived. The periodic structure is considered as a set of parallel cylindrical frequency selective surfaces, and the dispersion equation is calculated by using a transmission line model. Using this result, the dispersion proprieties of cylindrical electromagnetic bandgap structures composed of continuous or discontinuous metallic wires are presented. It is shown that the band structures of these materials can be determined by using the proposed dispersion equation. Cylindrical periodic materials have potential applications for designing directive antennas, circular high impedance surfaces, or agile antennas     

高能微波电磁脉冲武器

介绍了高功率微波武器的特点，简要说明了高能微波电磁脉冲的形成过程。叙述了在现代战争中应用的领域，并谈及我国发展该武器的紧迫性。     

Electromagnetic Modeling of Hot-Wire Detonators

An effort is underway to determine the electromagnetic (EM) characteristics of hot-wire detonators in order to quantify more precisely how they might respond to modern EM illumination. These analyses provide a precise tailored approach to EM safety and insights into IEEE Standard C95.7–2005. The analyses include a comprehensive investigation of physical detonator characteristics, which is then used to model detonators using EM theory. The theoretical analysis treats the detonator as a cascaded transmission line incorporating several different dielectric regions, and examines both differential and common mode excitation for a generic detonator geometry. This model is then implemented in Matlab and is used to calculate the input impedance for the detonator from dc to 9 GHz. This program can then be used to quickly investigate similarly constructed hot-wire detonators by simply varying the input parameters. The model is used to predict the input impedance for a state-of-the-art blasting cap, and these predictions are then compared with experimental measurements.      

Determination of Depth of Shallowly Buried Objects by Electromagnetic Induction

A method of determining the depth of a shallowly buried metallic object by using its electromagnetic response is investigated. The method consists in relating the distance of the object from the sensor to the ratio of voltages induced in two coils by the object when it is subjected to a pulsed magnetic field. While the theory is developed for a spherical object, experimental data for both spheres and spheroids are used to evaluate the technique. It is shown that over the range of depths for which the signal-to-noise ratio is large enough, the error in determining a sphere's depth should not exceed approximately 10 cm.     

微波体声波延迟线的电磁屏蔽

本文分析了微波体声波延迟线多层介质的电磁屏蔽效应，结果表明，全屏蔽方式可以有效地解决微波延迟线研制中的直通抑制问题。实验结果证实了理论分析。     

Microwave Modeling of Rectangular Tunnels

Natural propagation of electromagnetic waves in rectangular tunnels is investigated experimentally at microwave frequencies (1-10 GHz) using a tunnel model of reduced dimensions made of a lossy mixture of sand, water, and salt. The experimental results for the propagation constant of the low-order modes agree satisfactorily with theoretical predictions. Practical applications of the experimental technique are discussed.