射频吸波材料同轴测试装置改造及其性能比较

利用网络分析仪的时域功能在同轴装置中测试吸波材料性能的过程中,同轴测试装置必须满足特定的高度要求,测试效果伴随着同轴测试装置等截面段的长度增加而越理想,尤其体现在低频段。文中包括了本研究室结合搬迁对原有测试装置改进和1．6m角锥试样在改进前后的测试结果作了比较分析。     

多向铺层碳化硅纤维吸波材料吸波性能方向性研究

利用自由空间反射法测得了各向异性吸波材料的电磁参数,根据多向交叉辅层纤维吸波材料的传输矩阵方程编制了计算机程序,对多向铺层碳化硅纤维吸波材料的层数和层间夹角对吸波性能方向性的影响规律进行了计算,此方法具有较高的测试精度,实测值与计算值吻和很好.     

天馈线系统中阻抗变换器的原理和测试分析

阻抗变换器是天馈线系统的重要器件，它的的性能直接关系到天馈线发射系统的整体指标。文章简要介绍了阻抗变换器的原理，并用美国惠谱（HP）公司的8754A网络分析仪对它进行了测试分析，绘出了反射损耗测试曲线，分析了实验结果，为阻抗变换器的设计制造提供了理论根据和实验数据。     

片状CuO/PPy复合材料的电磁波吸收性能研究

采用水热法制备了片状CuO,并通过原位聚合法在片状CuO表面附着PPy (聚吡咯)。随后通过XRD、FT-IR、SEM等方法对复合材料的形貌和物相组成进行表征,并采用同轴环测试技术分析复合材料的电磁参数,最后根据传输线理论计算吸波材料的反射损耗RL。研究结果表明:复合材料填料比例为20wt%,涂层厚度为3mm时,复合材料在10.6GHz处出现最大吸收强度-25.1dB,当涂层厚度为2.5mm时,低于-10dB的有效吸收带宽达到7.5GHz,覆盖了整个Ku波段,达到了理想的吸波效果。     

纤维的体积分数对电磁参数和吸波性能的影响

采用自由空间反射法,分别对不同体积分数的碳化硅纤维和铁纤维吸渡贴片的电磁参数进行了测试,对纤维的体积分数对电磁参数的影响规律进行了分析,同时,根据测试的电磁参数和各向异性反射理论对纤维的体积分数对吸波性能的影响进行了理论计算和实验验证.     

射频同轴连接器屏蔽性能的测试

介绍了测试射频同轴连接器的转移阻抗的一种方法——线注入法,设计并制作了测试装置,测试了BNC型连接器的转移阻抗;分析和总结了相关测试数据,最后指出了注入线法测试电缆转移阻抗和测试连接器转移阻抗的区别。     

射频吸波材料拱形法测试系统的软件开发与应用

随着电磁兼容的不断发展和电磁波吸波材料的应用日益广泛,拱形法作为1 GHz以上频率测试射频吸波材料吸波性能的主要方法,对其研究有着重要意义.基于该测试方法的具体要求,针对该方法测试数据量庞大、数据处理和分析复杂等特点,在Lab VIEW开发环境下,编制了一套拱形法测试系统软件,包括:计算机与矢量网络分析仪通信模块;测试数据和信息写入ACCESS数据库模块;测试数据读取并显示模块.通过开发软件,不仅可以再现射频吸波材料反射系数的幅频特性曲线,而且可以显示出反射系数的幅度-高度曲线和幅度-角度曲线,还可同时显示仅某一测试参量不同的多条反射系数幅频特性曲线,以利于反映材料反射系数随各种测试参量的变化情况,另外程序也可将相同测试条件下不同吸波材料的反射系数幅频特性曲线显示在同一图形中,从而可以方便地对不同吸波材料的吸波性能进行对比分析.实验表明,测试软件可以应用于拱形法测试,并有效地提高了测试以及处理、分析测试数据的效率.     

反射率远场测试系统研究

搭建了基于矢量网络分析仪的反射率远场测试系统测量雷达吸波材料反射率。利用180 mm×180 mm×5 mm铝板作为标准体,检测了系统的性能指标;利用大头针测试了系统的位置精度;测试了高度300 mm的泡沫实心角锥吸波材料的反射率。实验结果表明,该反射率远场测试系统的幅度精度在1 d B内,位置误差优于5 mm,对反射率测试结果误差小于1 d B,系统测试精度小于2%。     

一种用双电流探头进行阻抗测试的方法

随着电磁兼容测试仪器的不断更新升级,电磁兼容的测量结果的精度要求也需越来越准确。目前,对元器件的阻抗测试大多都是利用阻抗分析仪来完成,并且该种测量的方法是在被测设备断电停止工作时进行的。如果元器件在通电工作时,其内部电路情况可能会发生些许变化,进而使其阻抗发生改变,那么用阻抗分析仪在其断电情况下得到的阻抗值可能会与其在通电工作时的实时阻抗有所差异。因此,本文提出一种在元器件通电工作时进行阻抗测试的方法,并对其开展研究。     

碳化硅涂层吸波性能的研究

根据吸波机理的相关技术,人们利用工业废弃的塑料等产物作为原料生产碳化硅。作为吸波材料,人们可以将碳化硅制成涂层,再通过XRD、SEM等技术检测碳化硅的结构和反射衰减等,进而评估碳化硅涂层的吸波性能。     

Cutoff probe using Fourier analysis for electron density measurement

This paper proposes a new method for cutoff probe using a nanosecond impulse generator and an oscilloscope, instead of a network analyzer. The nanosecond impulse generator supplies a radiating signal of broadband frequency spectrum simultaneously without frequency sweeping, while frequency sweeping method is used by a network analyzer in a previous method. The transmission spectrum (S21) was obtained through a Fourier analysis of the transmitted impulse signal detected by the oscilloscope and was used to measure the electron density. The results showed that the transmission frequency spectrum and the electron density obtained with a new method are very close to those obtained with a previous method using a network analyzer. And also, only 15 ns long signal was necessary for spectrum reconstruction. These results were also compared to the Langmuir probe's measurements with satisfactory results. This method is expected to provide not only fast measurement of absolute electron density, but also function in other diagnostic situations where a network analyzer would be used (a hairpin probe and an impedance probe) by replacing the network analyzer with a nanosecond impulse generator and an oscilloscope.     

高频信号动态测试中的信号完整性分析

结合高频信号测试仪使用环境的特点及要求,分析了影响高速数据采集电路信号完整性的主要因素,针对高频信号的反射和串扰,分别从多层PCB板的层叠设计,差分信号传输线蛇形布线,添加阻抗匹配网络几方面进行了信号完整性设计。建立差分信号传输线拓扑网络的模型并通过仿真确定了阻抗匹配网络的结构和参数,减小了由于传输线阻抗失配引起的信号反射与串扰;对电源完整性进行分析,通过内电层分割和滤波电容网络减小了电路中的地弹现象,从而降低了测试仪的系统噪声。最后通过模拟环境下的实验验证了高速数据采集电路的信号完整性分析,实验结果表明通过信号完整性设计提高了测试仪的抗干扰能力,所采集的数据可靠有效。     

A novel PC-based admittance analyzer for piezoelectric vibrators

To obtain the electromechanical match at resonant frequencies for piezoelectric actuating applications, the impedance or admittance characteristics of a piezoelectric vibrator must be measured by a spectrum analyzer. In this paper, the admittance analyzer has been developed using an integration technique with a GPIB card, a data acquisition card and software LabVIEW tools. Based on the five built-in models of equivalent circuits as the basic evaluating functions in a HP-4194A impedance analyzer, the most suitable model has been identified to demonstrate the electromechanical features of a piezoelectric vibrator. The measured results from the admittance analyzer and actual data from an HP-4194A analyzer are compared to evaluate the performance of the admittance analyzer. The analyzer offers the complete functions of a hardware instrument for measuring admittance based on theory and experiments within the 120 kHz range.     

刀具负载对蜂窝复合材料超声切割声学系统阻抗特性的影响

针对刀具负载对蜂窝复合材料超声切割声学系统的影响,利用四端网络法,将压电换能器与变幅杆结合在一起,提出了声学系统的整体设计方程,得出了负载与声学系统阻抗特性的关系式。利用有限元软件对声学系统进行模态分析及谐响应分析,并利用阻抗分析仪和激光位移传感器对声学系统的阻抗﹑谐振频率和输出振幅进行检测。仿真和实验结果表明：随着刀具负载的增大,声学系统的阻抗值增大,谐振频率减小,但仿真与实验得出的输出振幅与理论分析不同,这是由于刀具的放大作用造成的。研究结果对声学系统的设计及实际应用有指导意义。     

Nondestructive Permittivity Profile Retrieval of Non-Planar Objects by Free Space Microwave Techniques

In this paper, a nondestructive method for the non-contact characterization of non-planar dielectric objects is presented. Traditionally, this kind of measurement is achieved by using spot-focused antennas associated to a vector network analyzer. In this study, we propose a free space measurement system, fitted out with a classical horn antenna, which demonstrates its usefulness in many practical cases. The permittivity has been computed from the measurement of the reflection coefficient of metal-backed samples of different shapes at 2.45 GHz. Signal processing tools, based on deconvolution techniques, are developed to enhance the accuracy of the permittivity measurement.     

基于归一化网络的多枝节阻抗匹配仿真

为使微波电路或系统无反射,行驻波尽最接近行波状态,从而使得负载功率达到最大的阻抗匹配问题一般采用双枝节阻抗匹配;但是双枝节匹配对于负载阻抗的电导有严格要求,可能会出现匹配失败.通过归一化网络计算多枝节问题,使计算无耗传输线的匹配问题时无需考虑系统的特性阻抗和波长,只需考虑网络矩阵进行级联计算后的阻抗匹配,弥补了图解法的...     

基于SR7265硬件的虚拟锁相放大器、频谱仪、阻抗计和半导体参数分析仪

锁相放大器是用来测量微弱信号的专用仪器.即使噪音上千倍于被测信号,通过锁相放大器,也能得到精确结果.随着数字信号处理技术在仪器中的应用,可编程仪器变得越来越灵活.结合虚拟仪器的技术,论文通过对SR7265的硬件重新编程,在同一个硬件上实现了虚拟锁相放大器、虚拟频谱仪、虚拟阻抗计和虚拟半导体参数分析仪等等功能.本虚拟仪器采用了4层的逻辑结构.同样的功能也在一个FPGA板上成功地部署.     

A Combined System for Automated Ellipsometry and for Network Analysis Based on a Microcomputer

ABSTRACT

A Microcomputer has been employed for the automation of two types of measurements: Ellipsometry, and ac impedance in a wide frequency range (“network analysis”). These measurements are combined in the characterization of electrochemical interfaces. An identical simple and fast algorithm has been employed in both cases for the digital analysis of a sinusoidal signal. The rotating analyzer ellipsometer has a time resolution of 0.01 sec and a precision of 0.01 deg, following 1 sec integration time. The network analyzer generates a complex plane plot in the range of 10mHz-1kHz in 5 min. These specification have been achieved by employing only basic electrochemical instrumentation and a manual ellipsometer, in conjunction with a low cost microcomputer.     

A multiresonance method for measuring the reflection coefficient in a waveguide

A new method for measuring the complex reflection coefficient in rectangular waveguides using a scalar network analyzer is proposed. This method is based on measurements of the resonance characteristics of a quasi-resonator, i.e., a portion of the waveguide between a reflecting object on one side and an object with a known scattering matrix on the other side. One advantage of the multiresonance technique is that simultaneous analysis is performed for the entire set of resonance frequencies, which substantially increases the accuracy in finding the reflection coefficient. The errors in measuring the magnitude and phase of the reflection coefficient in actual experiments were close to 0.015 and 1.5°, respectively.Translated from Pribory i Tekhnika Eksperimenta, No. 1, 2005, pp. 94–100.Original Russian Text Copyright © 2004 by Ponomarenko, Popov.     

Fe78Si9B13非晶薄带的巨磁阻抗效应

采用4284A型阻抗分析仪研究了退火处理、非晶薄带长度、交流电频率和磁场强度等对Fe<,78>Si<,9>B<,13>非晶薄带巨磁阻抗效应的影响.结果表明:退火可以提高非晶薄带的阻抗变化幅度;其阻抗随着薄带长度的增加和交流电频率的升高而增大,随着磁场强度的增大而减小;其阻抗变化幅度随着薄带长度的增加和交流电频率的升高和...