Electro-Optical System for EMP Measurement

An electro-optical system is described for measuring the E-field component of electromagnetic pulses (EMP) produced by an EMP-simulator. Typical rise time of these pulses is down to 10 ns, measured E-field strength from 1-500 kV/m. The measurement device consists of a He-Ne-Laser as the light source, fiber optics as the transmitter with a length of up to some hundred meters, a Pockels-cell with two polarizers as the sensor modulating the light intensity in dependence of E-field strength, and a photodiode with preamplifier and storage oscilloscope as the detector. The wide E-field range can be measured by capacitively coupling the E-field to the Pockels-cell via pairs of plane antennas with variable area. Measurements are shown of pulses produced by a laboratory simulator and a field simulator.     

The measurement of solar array discharges in a simulated spaceenvironment

A spacecraft in a plasma builds up charge on all the dielectric surfaces and interfaces. Once the net charge exceeds the dielectric breakdown of the material, a discharge occurs. One of the more susceptible pieces of equipment is the antenna/receiver system. The radiated E-field may be strong enough to create an ambiguous signal which may be misinterpreted by the system electronics and cause a system malfunction. A technique is developed to monitor the radiated E-field of materials discharging in an electron environment, using vacuum chambers for measuring the material discharges which are made of highly reflective materials. These chambers affect the radiated E-field due to multiple reflections from the walls. The technique developed defines a method for correcting the effects caused by the measurement facilities. The methodology is: monitor the radiated E-field with a broadband dipole antenna, and digitize the radiated signal as a function of time. Determine the frequency response of the radiated E-field using an FFT algorithm. Measure the transmission and reflection characteristics of the two-port network inside the measurement chamber, and determine the impedance network from the measured E-parameters across the frequency band of interest. Transform the measured E-field frequency response through the impedance network to obtain the frequency response of the actual radiated discharge current. Find the inverse FFT of this response to obtain the actual radiated discharge current response. This technique aids in the prediction of the E-field coupling into receive antennas on-board actual satellites     

An integrated optical 3D electric field sensing system based on time-division multiplexing

A new integrated optical three-dimensional (3D) electric field (E-field) sensing system is shown in this paper. In the system, the method of tuning laser’s wavelength is used for controlling the working point of the integrated optical E-field sensor to keep it always in linear working area. The sensing system contains three independent E-field sensors, and the tuning of their working points and the sensing of electric signal are completed by adopting time-division multiplexing (TDM) technique. Then, the theoretical analysis and simulation of the working mechanism of the E-field sensing system are done in this paper. The results show that the bandwidth of electric signal is directly related with the tuning time of working point, and also determines the working rate of the controlling system.     

测量材料吸收毫米波性能的新型探头

提出了用于测量吸波材料吸收雷达波性能的新型探头。引入高次模,采用相位分析法,克服了多变量干扰,简化计算。在固定区间求偏差和方差最小值,得到平缓电场。仿真结果证明新型探头口径电场平缓,波动小,近似平面波。新型探头的平面波范围与口径比为53%,比现有厘米波探头扩大了17.2%,能精确地模拟雷达对材料的辐射,减小测量误差。此探头尺寸较小,可广泛应用于户外测量材料吸收毫米波雷达电磁波的性能。     

A comparison of deep-heating electrode concepts for hyperthermia

There is mounting evidence that localized hyperthermia produced by electromagnetic waves may be useful in the treatment of cancer, and many innovative devices have been designed for this purpose. Most applicators employed for deep heating operate in the frequency region of 10-100MHz to provide greatest depth of penetration. Two basic categories of launching devices exist: E-field and H-field. The E-field applicators include conductive plates and fringing field devices; either may be used individually or in a multiple feed system. The H-field applicators include cylindrical and planar devices configured to produce specific heating patterns. We have analyzed and compared the performance of each of these devices, particularly in terms of engineering principles, design characteristics and their ability to transfer potentially therapeutic energy safely and at depth.     

Electric-field distribution near rectangular microstrip radiatorsfor hyperthermia heating: theory versus experiment in water

A rectangular microstrip antenna radiator is investigated for its near-zone radiation characteristics in water. Calculations of a cavity model theory are compared with the electric-field measurements of a miniature nonperturbing diode-dipole E-field probe whose 3 mm tip was positioned by an automatic three-axis scanning system. These comparisons have implications for the use of microstrip antennas in a multielement microwave hyperthermia applicator. Half-wavelength rectangular microstrip patches were designed to radiate in water at 915 MHz. Both low (epsilon r = 10) and high (epsilon r = 85) dielectric constant substrates were tested. Normal and tangential components of the near-zone radiated electric field were discriminated by appropriate orientation of the E-field probe. Low normal to transverse electric-field ratios at 3.0 cm depth indicate that the radiators may be useful for hyperthermia heating with an intervening water bolus. Electric-field pattern addition from a three-element linear array of these elements in water indicates that phase and amplitude adjustment can achieve some limited control over the distribution of radiated power.     

High-performance cell transistor design using metallic shieldembedded shallow trench isolation (MSE-STI) for Gbit generation DRAM's

In this paper, the cell transistor design issues for the Gbit level DRAM's with the isolation pitch of less than 0.2 μm caused by the inverse-narrow-channel effect (INCE) and the neighboring storage-node E-field penetration effect (NSPE) will be discussed. Then we propose novel DRAM cell transistor structure by employing metallic shield inside the shallow trench isolation (STI). As confirmed by three-dimensional (3-D) device simulation results, by suppressing the inverse narrow-channel effect and the neighboring storage-node E-field penetration effect using metallic shield inside STI, we can obtain reliable cell transistors with low-doped substrate, low junction leakage current and uniform V_TH a distribution regardless of the active width variation     

Calibration cell for E-field sensors in water environment

Compact and nonperturbing E-field sensors are used for antenna near field measurements. For application in the research area of hyperthermia these sensors are used in a water environment. Owing to the high dielectric constant of water in the frequency range from DC to ~1 GHz the sensitivity is changed. To perform a calibration of E-field sensors, a water-filled TEM-cell has been developed. The technique employs a transverse electromagnetic (TEM) transmission cell that operates as a 50 W impedance matched system. A uniform TEM-field is established inside the cell     

Operation of the Field Displacement Isolator in Rectangular Waveguide

A field displacement isolator in WR-159 rectangular waveguide consisting of a full height ferrite slab having a resistive film on one face is treated analytically. The resultant transcendental equation was programmed for a computer and values of the propagation constant found in the frequency range 5.90 to 6.45 kMc for various film resistivities. Two TE modes are found to exist whose relative behavior depends on the resistivity of the film. Reasonably close experimental verification of the results was obtained. for the total attenuation and for the predicted E-field distributions by E-field probe tests. Additional attenuation above that predicted by the theory for a single mode is observed as a result of an interference at the end of the ferrite. A partial height ferrite slab isolator was subjected to E-field probe tests. The field distributions were found to be similar to the full height case. Here, also, additional attenuation is obtained at some frequencies as a result of an interference.     

Novel Specific Absorption Rate (SAR) Measurement Method Using a Flat Solid Phantom

A novel specific absorption rate (SAR) measurement method is presented that employs a flat solid phantom with multiple embedded E-field probes. A radio device under test traverses over them during the scanning process. The solid phantom provides stable dielectric properties and easy handling, while the multiple E-field probes contribute to shortening the time for measuring the SAR distribution. This method can also be used as an alternative to that employing flat phantoms filled with liquid. Based on the numerical approach, the measurement system configuration is designed to obtain the SAR distributions with an error of within 10% at 900 and 1950 MHz, focusing on the following points: dimensions of the flat solid phantom, size of the E-field probe, and distance between the E-field probes. The experimental setup for the frequency of 1950 MHz confirms that the proposed measurement method obtains the average SARs over 10 and 1 g with an error of within 10% compared to the computed values.     

男性生殖器在915和2450MHz微波作用下的比吸收率分布

应用模型实验和数字化红外热象技术,定量地测定了男性生殖器在915和2450MHz微波远场和近场作用下的SAR分布。实验表明:男性生殖器对915和2450MHz微波的吸收有极化效应。当微波电场矢量E与阴茎平行时,阴茎吸收最强,最大SAR出现在阴茎基部;当微波电场矢量E与阴茎垂直时,对915MHz微波,最大SAR出现在阴囊中心,对2450MHz微波,最失SAR出现在睾丸内,显示同一器官对不同频率,不同极化微波的吸收特性间的差别。本文对实验结果进行了讨论并与过去的理论分析和实验结果作了比较,显示相当接近。     

光纤传输式瞬态脉冲电场传感器分析与设计

为实现瞬态脉冲电磁场的时域测试,研制了一种基于场效应管加载的光纤传输式电场传感器。根据电场传感器的等效电路模型及其实尺仿真模型,分析了接收天线的负载阻抗及其长度等参数变化对传感器测试性能的影响,为传感器设计中的参数选择提供了参考。在此基础上,利用自行研制的电场传感器分别对核电磁脉冲场和雷电电磁脉冲场进行了实测,结果表明:传感器的高、低频响应能力均较好,基本可以满足测试瞬态电磁脉冲场的需要,验证了传感器设计的可行性。     

Theoretical analysis of H-Horn annular phased array system for heating deep-seated tumors

This paper discusses a type of annular phased array system--H-Horn APA. The phase and amplitude control of power deposition patterns for this system are theoretically analyzed at a frequency of 200 MHz. The formulas for calculating E-field and SAR for this APA system are derived, and can be applied to other type APA systems. Models of computerized tomography (CT) scans from liver and lung regions have been used, respectively, for predicting optimization of E-field and SAR patterns in the case of the relative phase and amplitude changes. It is shown that the techniques of the phase and amplitude control of SAR patterns result in more selectively and effectively heating of tumors situated eccentrically and deeply within bodies of patients. The APA hyperthermia described in this paper shows great promise, and it looks very useful for developing clinical applications.     

Electromagnetic properties of nonreciprocal compositechiral-ferrite media

The theoretical properties of a composite chiral-ferrite medium are developed, The composite is constructed from a general chiral medium and a nonreciprocal ferrite medium. Application of the reaction theorem allows proof of nonreciprocity based on the constitutive relationships. Vector Helmholtz E- and H-field equations are derived, and from these equations reciprocal space Green's function dyadics are found. The direct space dyadics are then determined. Characteristic dispersion equations are found from the sourceless vector phasor Helmholtz equations. E-field polarization is obtained by projecting the E-field vector onto the polarization plane selected. Diagonalization of the elliptic equation through coordinate rotation allows major and minor axis determination     

大功率微波下超材料的设计和应用

为使超材料结构在大功率微波下更稳定地工作,本文介绍的超材料结构由双层打孔金属板构成,不同于常见的由介质基板构成的超材料结构.通过采用散射参数反演方法计算发现,超材料结构具有零折射率系数的特性,并对电场场强分布产生一定的影响.为了解该超材料对天线性能的影响,在实验过程中,采用松下2M244-M1型磁控管作为微波源来产生大功率微波,测试结果显示,半功率宽度由28°减小为15°,增益提高了1.7 dB.     

海浪对水下航行器漂浮电缆收信性能的影响分析

分析了漂浮电缆受力情况,给出了平静海面下的接收信号表达式,得到了信号电压与电场强度的近似关系式。分析了海浪对漂浮电缆的影响,建立了海浪下的漂浮电缆模型,推导出水下航行器的拖带速度和线缆深度的关系,并且推导了海浪下漂浮电缆的接收信号表达式,得到了信号电压与电场强度的近似关系式,从而为水下航行器漂浮电缆收信性能的计算与应用提供了参考。     

Automated E-field scanning system for dosimetric assessments

The interest in accurate dosimetric measurements inside phantoms that simulate biological bodies has burgeoned since several regulatory commissions began calling for or recommending the testing for compliance with safety standards of low power devices. This paper presents a newly developed, robot-based system that allows automated E-field scanning in tissue simulating solutions. The distinguishing characteristics of the system are its high sensitivity and its broad dynamic range (1 μW/g to 100 mW/g) over the entire frequency range (10 MHz to over 3 GHz) used for mobile communications. The reproducibility of the dosimetric evaluations has been shown to be considerably better than ±5%. This has been accomplished by the use of an improved isotropic E-field probe connected to amplifiers with extremely low noise and drift characteristics in conjunction with digital processing of the data. Special emphasis has been placed on system reliability, user-friendliness and graphic visualization of data     

Mixed-field hybrid FEM/BEM formulation for two-dimensional TEradiation and scattering by resistive strips

A new mixed-field, hybrid finite-element method (FEM) (E-field)/BEM (H-field) formulation is presented for modeling the two-dimensional (2-D) radiation and scattering from scatterers comprised with inhomogeneous materials including resistive cards and perfectly electrically conducting (PEC) strips for the TE polarization. Using the usual H-field formulation leads to the requirement for the use of a special gap element. The E-field formulation will result in a much more cumbersome BEM integral. The new mixed-field formulation retains the simplicity of the scalar formulation and is useful for problems which cannot be treated elegantly with the existing approach. The new formulation has been implemented into a 2-D FEM/BEM computer code. Numerical results obtained compare well to previously published results     

Generalization of the Ludwig-3 definition for linear copolarizationand cross polarization

This article presents a generalization of Ludwig's (1973) third definition that introduces a &thetas;-dependence that is absent from Ludwig's original definition. Our generalization is based on the nonconformal mapping between the electric field vector lying in the propagation plane (i.e., the probe aperture plane) and the projection of this vector onto the aperture plane (i.e., the AUT aperture plane). We show the error incurred by the two definitions for both the E-field and the H-field aperture models. Ludwig's definition incurs the same level of error for both models while our generalized definition incurs slightly more error for the H-field aperture model but no error for the E-field aperture model     

Combined-field integral equation

The combined-field integral equation (CFIE) is a linear combination of the H-field and the E-field integral equations. Previously, the weighting parameter of the E-field equation in the CFIE had been assumed constant along the generating curve of the body of revolution. However, it is shown that the weighting parameter can take a variable distribution along the generating curve or on a part of it only. In the latter case, a reduction in the computational time of 40-50% is achieved.<>