RF radiation properties of printed-circuits boards in a GTEM cell

The behavior of reradiated fields from printed-circuits boards (PCBs), with the radar cross section being the main parameter of interest, is investigated in this paper. A rigorous approach to predict radiation from PCBs in a gigahertz transverse electromagnetic cell is presented. The analysis is based upon the use of the reciprocity theorem in combination with the method of moment applied to the scattered field, thus yielding a generalized impedance matrix, whose determinant represents the characteristic polynomial of the scattering system. The effectiveness of the method is demonstrated by investigating some canonical circuit configurations and structures illustrating sources of fundamental electromagnetic interference mechanism. The validity and the accuracy of the analysis becomes obvious in view of the one-to-one correlation with measurements.     

Rigorous analysis of the GTEM cell

The modeling of a GTEM cell which consists of a tapered rectangular waveguide loaded with an eccentric sloping plate conductor is discussed. The fields of the cross section of the uniform structure are derived by transverse resonance diffraction. The local modes approach is applied to the study of the longitudinal field distribution. Results show the structure to be actually overmoded rather than quasi-TEM. Numerical results agree with those in the literature, where available. The treatment is highly accurate and requires no more computer power than that of a desktop computer     

一种有前景的辐射EMI测试方法--用GTEM小室做EMI测试

文中简介了用GTEM小室做电磁兼容辐射EMI测试的方法，概念，现状和实际测试结果，通过对电偶极源，磁偶极源和一个实际雷达分机在GTEM室和开阔场的实际测试，证实了用GTEM室做辐射EMI预测试或预测试的可行性。     

论吉赫横电磁室(GTEM)的理论与设计

新型GTEM室可克服传统横电磁室可用频率上限低的缺点,这是由于其结构渐变、避免表面锐棱转折和引入吸波材料,故可用于2GHz或更高频率。本文论述GTEM的原理和设计方法,特别关注该结构的特性阻抗的规律。文中指出了准静态分析法的局限,建议从导波系统的更普遍、更严格的观点处理这一问题。     

Accurate analysis of the GTEM cell wide-band termination

A model of the termination of the GTEM (GigaTEM) cell is discussed. The termination is effective over a very large band owing to the combination of resistors, acting at low frequencies up to ≈100 MHz, and of tapered absorbers, acting at frequencies higher than 100 MHz. The combined effect of both mechanisms is examined by using a transmission line model for low frequencies and a local mode expansion for higher frequencies     

在GTEM小室中测试UHF RFID标签的Delta RCS

该文提出了一种使用吉赫兹横电磁波传输(GTEM)小室进行被动式超高频射频识别(UHF RFID)标签Delta Radar Cross Section (RCS)测试的方法。通过理论分析RFID标签工作时的等效电路及其散射特性,推导出GTEM小室中和自由空间中UHF RFID标签Delta RCS测试的等效性。并通过GTEM小室和全电波暗室的对比实验,验证了使用GTEM小室进行UHF RFID标签Delta RCS测试的可行性及实用性。     

GTEM小室性能测试方法

文章在GTEM小室原理及其应用的基础上详细介绍了GTEM小室的性能指标,并结合具体测试给出了GTEM小室性能测试方法。结果表明,本测试方法所使用的时域阻抗、电压驻波比、场均匀性及屏蔽效能这四个指标能够较好地反映GTEM小室的技术性能。     

光折变相位共轭技术的研究进展

简要地介绍了光折变相位共轭技术的研究概况,着重介绍了自泵浦相位共轭镜及互泵浦相位共轭镜的研究进展,对它们的结构及机理做出了说明。     

两类单阿秒脉冲产生技术的相位依赖性分析

为了分析目前国际上现有的两类高次谐波极紫外单阿秒脉冲产生技术——振幅选通技术和偏振选通技术在驱动脉冲场载波-包络相位设置方面的差异,基于这两类单脉冲产生技术基本原理并借助于高次谐波产生3步理论分析模型,半定量分析了这两类技术的驱动光场载波-包络相位依赖性及其差异。结果表明,两者的最佳驱动脉冲场载波-包络相位设置分别为0与0.5π,出现此差异的根本原因是高次谐波现象对驱动光场偏振度的高度依赖性。此分析结果对更短脉宽极紫外阿秒脉冲光源的产生和相关应用具有重要的参考价值。     

A Method to Minimize Emission Measurement Uncertainty of Electrically Large EUTs in GTEM Cells and FARs Above 1 GHz

This paper presents an emission measurement technique with reduced uncertainties for electrically large equipment under test (EUTs) in gigahertz transverse electromagnetic (GTEM) cells and fully anechoic rooms (FARs) above 1 GHz. A small and a large EUT were measured and the results obtained in the GTEM cell were validated against those obtained in a FAR. Measurements in a FAR were made, for the small EUT, in the conventional way with an azimuth scan and, for the large EUT, with a limited antenna height scan. Key findings are that similar scanning is required in the GTEM cell and that the three-orthogonal-position (TOP) method of EN61000-4-20 is not appropriate for EUTs that have multilobed radiation patterns. In other words, GTEM cells and FARs are sensitive to directional properties of EUTs, and both methods require further scanning for electrically large EUTs     

Convergence properties of wide-angle techniques

We apply Lanczos and Pade methods to a series of field propagation techniques and examine the relative advantages of each procedure     

Improving phase unwrapping techniques by the use of local frequencyestimates

In multipass spaceborne synthetic aperture radar (SAR) interferometry, the two acquisitions often present low correlation levels and very noisy phase measurements that are incompatible with automatic phase unwrapping. Instead of dealing with many residues due to erroneous-wrapped phase differences, the authors propose to use the local frequency as measured by a spectral analysis algorithm presented in a previous paper, E. Trouve et al. (1996). For this purpose, the authors present two conventional unwrapping algorithms, one local and the other global, which they revisit to benefit from the robust focal frequency estimates. For a local approach based on path-following techniques, they use the frequency estimates in a slope-compensated filter that extend the complex averaging up to a sufficient number of looks to eliminate residues due to the noise. Then they connect residues due to noninterferometric features along mask components resulting from the detection of layovers and uncorrelated areas. For a global approach, such as the weighted least-squares methods, they demonstrate that the use of noisy discrete phase gradient leads to a biased solution. To avoid this drawback, they propose to use the local frequency estimate and associated measure of confidence as phase gradient and weight. Results are presented on both topographic and differential interferograms obtained from the ERS-1 European radar satellite over various landscapes and the displacement field of the Landers 1992 earthquake     

GTEM室场均匀性校准方法研究

根据IEC 61000-4-20:2010,介绍了场均匀校准的要求和方法,结合电磁波的传播特点并基于概率统计的方法对GTEM Cell中选定的有效试验区域进行验证;同时,针对试验结果,用GB 17626.3-2006暗室的场均匀校准方法重新验证。最后分析测试结果,并提出相应建议。     

A comparison of techniques to optimize measurement of voltage changes in electrical impedance tomography by minimizing phase shift errors

In electrical impedance tomography, errors due to stray capacitance may be reduced by optimization of the reference phase of the demodulator. Two possible methods, maximization of the demodulator output and minimization of reciprocity error have been assessed, applied to each electrode combination individually, or to all combinations as a whole. Using an EIT system with a single impedance measuring circuit and multiplexer to address the 16 electrodes, the methods were tested on resistor-capacitor networks, saline-filled tanks and humans during variation of the saline concentration of a constant fluid volume in the stomach. Optimization of each channel individually gave less error, particularly on humans, and maximization of the output of the demodulator was more robust. This method is, therefore, recommended to optimize systems and reduce systematic errors with similar EIT systems.     

Multiplexing of interferometric sensors using phase carrier techniques

This paper demonstrates the multiplexing of fiber-optic interferometric sensors using a CW phase generated carrier technique. The technique employs modulated diode laser sources at different carrier frequencies, nearly balanced interferometers (∼4-cm path difference), and phase generated carrier demultiplexing demodulation. This approach leads to a simple all-passive sensor array which has intrinsically low crosstalk. The system is analyzed in terms of shot noise performance and crosstalk. An experimental all optical implementation of a four sensor array was demonstrated; both the single sensor and multisensor arrays were limited by the laser phase noise to a sensitivity ofsim 18 murad/sqrt{Hz}. Crosstalk between individual channels was better than -60 dB and crosstalk between three sensors and the test sensor was better than -55 dB. In the absence of laser phase noise the demodulator/demultiplexer demonstratedsim 2-murad performance with both single sensor and four element array operation.     

A new look into the acquisition properties of a second-orderdigital phase locked loop

With the help of real-time numerical simulation results, the acquisition properties of a second-order ZC₁-DPLL are investigated. Besides confirming the sensitivity of the system dynamics to the initial values of the state variables, it predicts qualitatively the maximum possible frequency acquisition range (FAR) of the system, and obtains the values of the maximum FAR for systems with different design parameters. The effect of jitter on the loop dynamics has also been considered     

A subspace identification extension to the phase correlation method

The phase correlation method (PCM) is known to provide straightforward estimation of rigid translational motion between two images. It is often claimed that the original method is best suited to identify integer pixel displacements, which has prompted the development of numerous subpixel displacement identification methods. However, the fact that the phase correlation matrix is rank one for a noise-free rigid translation model is often overlooked. This property leads to the low complexity subspace identification technique presented here. The combination of non-integer pixel displacement identification without interpolation, robustness to noise, and limited computational complexity make this approach a very attractive extension of the PCM. In addition, this approach is shown to be complementary with other subpixel phase correlation based techniques.     

A model for analyzing the interface properties of asemiconductor-insulator-semiconductor structure. I. Capacitance andconductance techniques

A model is presented for analyzing the interface properties of a semiconductor-insulator-semiconductor (SIS) capacitor structure. By introducing a coupling factor, conventional metal-oxide-semiconductor (MOS) capacitor theory is extended to analyze the interface properties of the film/buried-oxide/substrate interfaces of a silicon-on-insulator (SOI) material. This model was used to determine parameters such as doping concentration, buried oxide thickness, fixed oxide charge, and interface trap density from the SIMOX (separation by implantation of oxygen) based SIS capacitors     

光波反射相移测量的新方法

提出一种用单片机控制空心轴步进电动机带动检偏器旋转,测量光波在介质界面上发生全反射时相位移动量的智能化方法。给出了测量系统和相关计算机程序框图。测量了ZF—7光学玻璃直角三棱镜斜面上内反射的相移,实验结果和理论计算吻合。同时给出了判断相移正、负的方法。该方法的优点是光路简单,智能化程度和测量精度高,并且很容易推广到相关偏振光相位差的测量中。     

A Complete Model for Simulating Magnitude and Phase of Emissions from a DUT Placed Inside a GTEM Cell

Since the publication of IEC 61000-4-20, the gigahertz transverse electromagnetic (GTEM) cell has gained popularity in radiated emission and immunity electromagnetic compatibility tests. Various numerical methods such as finite-difference time-domain, finite element method, and method of moments have been used to model the GTEM cell in the pursuit of getting to know the characteristic of the GTEM cell with varying degrees of verification. In this paper, the time-domain transmission line model will be used to model the GTEM cell. The advantages of this method include high accuracy and the ability to model different materials. Thus, the GTEM is realistically modeled including radio absorbing material (RAM) and lumped terminations. In addition, the model of a realistic device under test (DUT) was also included in the GTEM model. The DUT consists of a standard sized box with an aperture, placed in different orientations inside the GTEM for power and phase measurements. The particular features of this paper are: 1) the inclusion of a realistic numerical model of RAM, 2) the inclusion of a realistic DUT model, 3) systematic verification of the model against measurements, and 4) the method of phase measurement in a GTEM cell. Good agreement between the experimental results and simulations is obtained.