Microwave impedance determination by reflection-coefficient measurement through an arbitrary linear 2-port system

A new method is described for measuring an impedance accessible only through an unknown 2-port linear system. Four calibrating impedances are used: a known resistance, a short circuit and two other unknown reactances. The value of impedance is calculable directly from the input measurements using simple step-by-step formulas.     

Experimental determination of tie-lines in the Hg-Cd-Te system

Starting with powdered Hg_1−xCd_xTe, several tie-lines at 500 and 560°C were established using an energy dispersive spectrometer on a scanning electron microscope for the quantitative analysis. After holding at 500 or 560°C for time periods based upon the powder size and the published interdiffusion constant, then water quenching to room temperature, the primary grains were found to be uniform in composition and covered with a 5-6 μ layer of HgTe or low x Hg_1−xCd_xTe. The primary grain and overall compositions establish directions for tie-lines that are in good agreement with published experimental and theoreti-cal results.     

Experimental determination and thermodynamic calculation of the phase equilibria in the Cu-In-Sn system

The phase equilibria of the Cu-In-Sn system were investigated by means of the diffusion couple method, differential scanning calorimetry (DSC) and metallography. The isothermal sections at 110–900 C, as well as vertical sections at 10wt.%Cu–70wt.%Cu were determined. It was found that there are large solubilities of In in the ε(Cu₃Sn), δ(Cu₄₁Sn₁₁), and η phases in the Cu-Sn system, and large solubilities of Sn in the γ, η, and δ(Cu₇In₃) phases in the Cu-In system. The η phase was found to continuously form from the Cu-In side to the Cu-Sn side, and a ternary compound (Cu₂In₃Sn) was found to exist at 110 C. Thermodynamic assessment of the Cu-In-Sn system was also carried out based on experimental data of activity and phase equilibria using the CALPHAD method, in which the Gibbs energies of the liquid, fcc and bcc phases are described by the subregular solution model and that of compounds, including two ternary compounds, are represented by the sublattice model. The thermodynamic parameters for describing the phase equilibria were optimized, and agreement between the calculated and experimental results was obtained.     

Spherical measurement system for determination of complex radiation patterns of mobile terminals

A prototype of a 'real-time' 64-channel spherical measurement system for determining the complex radiated far fields of active mobile terminals is presented. The system does not require any RF feed cables to be connected to the mobile terminal. Test measurements show that the complex far field can be determined with an acceptable accuracy. The system thus provides, together with the radio-channel data, a basis for realistic and fast estimation of MIMO performance of a mobile terminal.     

光纤电流传感器的实验系统与性能

光纤电流传感器是把光纤缠绕在导线周围,光纤既是信息的传输元件又是信息的敏感元件,因此这种传感器的地面设备以外的部份就只是整根的光纤,这不但解决了绝缘问题,且具有抗电磁干扰、灵敏度高、测量动态范围大的优点,具有广泛的应用前景.二、基本关系式因光纤材料的Faraday效应,在长直导线上绕有N圈光纤时,其偏振光的旋转角度θ为:θ=VNI(1)式中V是Verdet常数.图1为实验系统简图.从波长为632.8nm的He-Ne激光器发出的激光束经     

Determination of the spectral response of sis-junctions by a direct detection measurement

We present a simple method to determine the spectral response of an SIS detector in the millimeter and submillimeter wavelength range from its current response to a chopped cold-load. This direct detection response is also a good indicator of quantum efficiency and mixer noise temperature when using the SIS junction in heterodyne mode. A simple experimental setup without local oscillator, cryogenic IF-amplifier or any quasioptical interferometer allows a quick diagnosis of integrated planar impedance matching structures.     

无合作目标测量中目标表面后向散射特性的实验研究

设计并搭建了半球空间内收发同轴的目标表面后向散射特性测量系统,以1 550 nm线偏振、窄线宽激光为光源,在0°~±60°入射角度范围内,通过对具有不同表面微观形貌(研磨、立铣和平铣加工表面)的典型粗糙度比较样块进行后向散射特性的测量,探讨了入射光偏振方向、入射方位角、入射角和表面微观形貌的变化对后向散射特性的影响,分析了这些影响产生的原因,并分析了后向散射场偏振特性的变化。结果表明这些影响因子均对表面后向散射特性产生规律性影响,既有共性规律,也有个性规律.其中,表面微观形貌又决定着入射方位角、入射角等变量变化时对后向散射场能量分布及偏振性质的改变所产生的影响。这一结果为无合作目标测量领域及其他表面测量特性研究领域提供参考及应用价值。     

Experimental determination and thermodynamic calculation of the phase equilibria and surface tension in the Sn-Ag-In system

The phase equilibria of the Sn-Ag-In system were investigated by means of differential scanning calorimetry (DSC) and metallography. The isothermal sections at 180–600°C, as well as some vertical sections, were determined. Thermodynamic assessment of this system was also carried out based on the experimental data of thermodynamic properties and phase equilibria using the calculation of phase diagram (CALPHAD) method, in which the Gibbs energies of the liquid, fcc, and hcp phases are described by the subregular solution model, and those of compounds are represented by the sublattice model. The thermodynamic parameters for describing the phase equilibria were optimized, and reasonable agreement between the calculated and experimental results was obtained. The maximum bubble-pressure method and dilatometric method have been used in measurements of the surface tension and density of the binary In-Sn and ternary (Sn-3.8Ag)_eut + In (5 at.% and 10 at.%) liquid alloys, respectively. The experiments were performed in the temperature range from 160–930°C. The experimental data of the surface tension were compared with those obtained by the thermodynamic calculation of Butler’s model.     

棒球测速系统的设计与实现

本文应用芯片技术设计了棒球测速系统,首先阐述了该系统的工作原理,并对系统需求进行了分析,然后设计了硬件系统和软件系统,硬件系统的加速度传感器采用ADXL345,单片机采用ST7LITE49M,软件系统主要设计了1COSMIC C编译器,最后对该系统进行了系统测试,结果较满意。     

一种高精度外弹道测量系统的设计

介绍了一套基于扩频伪码单程测距、多基站时差定位、GPS同源共视定时的外弹道测量系统,给出了该系统的设备组成、工作原理,分析了系统工程实现中的几个关键技术问题及其解决途径,分析了影响系统定位精度的关键因素,给出了系统的理论定位精度.该系统具有外测精度高、抗干扰、保密强、可以适用于多目标测量等优点.     

Simulation of a proposed near-field-to-far-field antenna measurement system

A new antenna-pattern measurement method for antennas with large far-field distances is proposed. The method is applicable to conventional antenna ranges with two axis mounts and with pattern recording in amplitude only, It requires only a few minor items of additional equipment. A computer simulation has been carried out and the results are presented.     

Pseudorandom sequences and the measurement of the frequency response

There are many ways to measure the magnitude of the frequency response of a system. The authors consider three methods and explain why they are not optimal. Then a method that uses pseudorandom sequences and explains why this method is optimal is considered. The authors discuss pseudorandom sequences and show how their properties make them nearly ideal for measuring the magnitude of the frequency response of a system. Several implementations of pseudorandom sequence generators is described. Finally, an example of a measurement made using a pseudorandom sequence is provided. Pseudorandom sequences are used in audio applications to measure the properties of loudspeakers and of rooms. Additionally pseudorandom sequences are made use of in direct sequence spread spectrum.     

Impulse response of a discrete time system

The use of a Markov model is a valuable aid in the analysis of many systems. The purpose of this work is the establishment of a response for this type of system based on the use of an impulse function. The response of the system is obtained with the impulse as an excitation while utilising the Markov property of the system.     

基于调制度测量轮廓术的测量系统研究

调制度测量轮廓术可以实现对物体的垂直测量 ,特别适合于探测表面有高度剧烈变化或不连续区域的物体 ,研究实用的基于调制度测量轮廓术的测量系统对三维传感和机器视觉有重要意义。本文从调制度测量轮廓术的原理出发 ,分析了获取条纹调制度信息的原理 ,提出了两种易于实现仪器化的垂直扫描方法 ,提出了调制度测量轮廓术的实验系统设计方法和步骤 ,给出了模拟实验结果。本文的工作对调制度测量轮廓术的实验设计和实用化有重要的意义     

微结构光纤色散参数的实验测量

利用基于迈克耳逊干涉仪的干涉法,在可见光波段测量了一种全内反射型微结构光纤的群速度色散和色散参数值,其中在450nm处,色散参数D为-416.987ps-2·nm-1·km-1,并用多极法进行了数值模拟,发现实验测量值与理论计算结果具有很好的一致性.     

Design of a monopulse SAR system for the determination of elevationangles

Terrain height variations in mountainous areas cause problems in the radiometric correction of SAR images. The authors propose a novel SAR system which exploits the monopulse principle to determine the elevation angle and thus the height at the different parts of the image. From the ratios of images radiometrically modulated by the difference and sum antenna pattern in cross-track direction, the authors can calculate the appropriate elevation angle at any point in the image. In this paper, they present design considerations for an array antenna for DLR's airborne X-band SAR system and give estimates of the error due to system noise and azimuth ambiguities as well as the expected performance and precision in topographic mapping     

Calibration and measurement of a wideband six-port polarimetricmeasurement system

The principle of operation, calibration procedure, and experimental results of a wideband six-port polarimetric measurement system are described in this paper. This measurement system can measure the polarization states of incoming waves and the polarimetric scattering matrices of scattering targets from the wideband power data. The imbalances and coupling between antenna polarization channels and the characteristics of microwave components used in the measurement system are calibrated using three partly unknown scattering calibrators that are illuminated by four unknown-polarized calibrating waves     

高消光比测试系统的研究

消光比是标志偏光器件性能的主要参数之一,也是表征许多光学材料性质的重要指标。因此对消光比的精确测量一直是人们非常关心的问题,也是科研和生产中亟待解决的一个课题。而高消光比的测量更是急需解决的关键问题之一。虽然,过去人们曾在这方面做过一些工作,但由于起偏系统和测试方法等的限制,很难保证其测量精度和灵敏度,并且无法给出单只偏光器件的这一参数。本文给出了一种测量高消光比的有效方法。并建立了相应的测试系统,其消光比的测量优于10~(-9),能较好地满足科研和生产的需要。     

Application of a six-port network to a near-field antenna measurement system

The configuration and calibration of a six-port network analyser for application in near-field antenna measurements is described. The suitability of the new measurement system is illustrated by experimental results.     

Stabilization of a power system through output feedback

The optimal stabilization of a power system using the state variable feedback has the drawback that all the state variables are not available for measurement. A suboptimal control policy for stabilization of a power system is proposed, using the available output variables and employing the pole assignment technique. The proposed scheme is illustrated with an example.