矢量网络分析仪时域功能研究

本文介绍了矢量网络分析仪时域测量的数学原理,分析了时域测量的具体过程以及不同的参数设定对变换结果的影响,比较了低通和带通两种测量模式各自的特点,阐述了窗函数在提高测量动态范围、改善测量结果中的作用。最后提出了如何利用矢量网络分析仪进行同轴电缆测试,并结合实例分析了矢量网络分析仪时域功能在电缆长度测试、电缆故障定位等方面的应用。     

矢量网络分析仪在时域测量中的应用

文章主要讲述了使用矢量网络分析仪(VNA)在时域测试中进行故障定位分析的应用,通过对几个实例的测量,说明了矢量网络分析仪在时域测量中的有效性和重要性。     

矢量网络分析仪故障定位方法及典型维修案例

目前,矢量网络分析仪在微波领域中有着十分广泛的应用,由于端口功率输入超载或器件老化等原因,矢量网络分析仪会发生损坏,其中典型的故障便是源输出功率不足、接收机故障以及本振合成板故障等。基于此,以3种典型故障案例为切入点,阐述了功率测量法、自检结果分析法、观察对比法等在故障定位中的应用,为矢量网络分析仪的维修提供了参考。     

矢量网络分析仪校正系统构建

介绍了构建的一种易用的矢量网络分析仪校正系统,该系统用于校正算法的验证.由于在目前的矢量网络分析仪中,应用新的误差模型和新的校正方法非常复杂,笔者把其内部集成的数据处理流程拿到了网络分析仪外来实现.对该系统的硬件和软件特性都进行了阐述.该系统使误差校正验证工作更加灵活高效.     

矢量网络分析仪动态范围的原位拓展方法

针对大带外抑制滤波器传输和反射特性的测试需求,提出了一种矢量网络分析仪动态范围的原位拓展方法。该方法在不改变仪器硬件架构的前提下,在测试链路中增加低噪声放大器,通过把微小信号放大来拓展动态范围,并采用互相关的信号处理算法,通过对两路测试数据进行多次运算进一步降低了仪器的噪声基底。为提升测试精度,解决因低噪声放大器的引入导致无法直接获取接收端口误差项的问题,设计了基于12项误差模型的两步校准方法,并完成了连接适配器参数的提取和去嵌入。最后,对两个不同频段的大带外抑制滤波器进行特性测量。试验结果表明,200 Hz中频带宽下动态范围可以达到130 dB,相对于常规仪器的动态范围可以提升20 dB以上,验证了方法的有效性。     

矢量网络分析仪8项误差模型和校正理论

对矢量网络分析仪S-参量误差模型的建立及校正理论进行了研究.给出了八项误差模型建立的基本理论.并根据此理论设计了一套利用标准元件对矢量网络分析仪S-参量测量进行校正的方法.简化了校正计算.     

矢量网络分析仪在变频器件群时延测量方面的应用

介绍基于矢量网络分析仪对变频器件的群时延进行测量的方法,以RS公司生产的ZVA和Agilent公司生产的PNA矢量网络分析仪为代表,分别对外接本振变频器件和嵌入式本振变频器件的群时延测量原理进行了阐述,可根据不同的测试需求选择有效的测试方法。     

基于线性扫频源的X波段快速幅相测量系统

研制了一种X波段微波网络快速扫频幅相测量系统.系统采用基于小数分频锁相环的线性扫频微波源作为激励,不存在常规矢量网络分析仪的跳频稳频过程.针对线性扫频源激励的特点,系统采用希尔伯特变换(Hilbert transform)或正交解调方法从中频信号中得到幅度和相位.使用研制系统和商用矢量网络分析仪测量了同一X波段的可调谐移相器的频率响应特性.尽管研制系统由于接收机通道不足不能进行完备矢量校准,但通过合理配置隔离器后相位测量结果与商用矢量网络分析仪十分吻合,这表明研制的测量系统不仅测量速度快,而且可能达到较好的测量精度.     

矢量网络分析仪自动校准系统的设计与实现

矢量网络分析仪是无线通信领域常用的一种设备,现对该仪器的校准方法进行了归纳总结,提出了能对该仪器进行自动校准的系统的设计方案并加以实现,简述了系统的主要组成、自动校准软件的架构、软件流程图及各模块的功能,为矢量网络分析仪的自动校准提供了一个可行的参考方案。     

基于GPIB中断请求的多台矢网自动记录系统设计

矢量网络分析仪主要用于射频微波器件的驻波、衰减等参数的测试.传统的失量网络分析仪通过人工操作记录,测试结果不能编辑,使得测试不灵活,效率低.文中设计了基于GPIB中断请求的数据获取模式,通过主控计算机处理GPIB中断请求,完成对多台矢量网络分析仪的控制,自动处理记录响应,存储记录文件,多台计算机通过网络共享记录,可对记录结果编辑,修改.提高了批量射频器件的测试效率,同时可根据用户需求生成自定义测试记录.系统已通过长期使用,结果表明系统稳定可靠,请求响应处理准确率达99％以上.     

Note: Vector network analyzer-ferromagnetic resonance spectrometer using high Q-factor cavity

A ferromagnetic resonance (FMR) spectrometer whose main components consist of an X-band resonator and a vector network analyzer (VNA) was developed. This spectrometer takes advantage of a high Q-factor (9600) cavity and state-of-the-art VNA. Accordingly, field modulation lock-in technique for signal to noise ratio (SNR) enhancement is no longer necessary, and FMR absorption can therefore be extracted directly. Its derivative for the ascertainment of full width at half maximum height of FMR peak can be found by taking the differentiation of original data. This system was characterized with different thicknesses of permalloy (Py) films and its multilayer, and found that the SNR of 5 nm Py on glass was better than 50, and did not have significant reduction even at low microwave excitation power (-20 dBm), and at low Q-factor (3000). The FMR other than X-band can also be examined in the same manner by using a suitable band cavity within the frequency range of VNA.     

Smith-chart diagnostics for multi-GHz time-domain-reflectometry dielectric spectroscopy

A time-domain-reflectometry Smith-chart display is demonstrated to be a valuable diagnostic tool in a variety of situations in time-domain-reflectometry dielectric spectroscopy. A relative reflection coefficient is formed by dividing the Laplace transform of the reflected sample transient by the Laplace transform of the empty-sensor transient and displaying in the complex plane, with the approximate sensor admittance read from susceptance and conductance circles. The Smith chart provides, as a diagnostic tool, an initial estimate of the dielectric behavior in the multi-GHz range and a means of identifying artifacts in acquisition and Laplace transform, in a way which does not require multiple steps of calibration and is only one step removed from the direct transient. Results are presented for a simple 3.5-mm flat sensor immersed in various liquid media, showing variations in the Smith chart for typical variations in sample permittivity, loss, and conductivity. Results are matched to vector network analyzer (VNA) measurement over an identical frequency range, as well as to finite-element field simulation. Results are also presented for a 3.5-mm sensor with various terminating pin lengths, typically employed at low frequencies and low permittivity media to increase sensor capacitance. For an unshielded pin, the Smith chart detects reflections from sample boundaries and measures the effectiveness of shielding used to eliminate these reflections. For a shielded pin, it characterizes the effect of pin length on the susceptance variation and the onset of pin resonance at high frequencies and high-permittivity values. The effect of artifacts appearing in the Smith chart on the actual calibration is shown by tracking them through the calibration process to the final result. Results are also presented for a 9-mm flat termination used for concrete hydration monitoring, showing effects of transmission-line discontinuities within a terminating plug and the onset of waveguide-like modes in a surrounding shield, with results compared to VNA measurement.     

Complex permittivity measurement using capacitance method from 300 kHz to 50 MHz

Complex permittivity measurement has been performed using a parallel plate capacitor and a vector network analyzer (VNA) from 300 kHz to 50 MHz. The material under test (MUT) is a flat and thin sample clamped between the capacitor plates and connected to the VNA to obtain its two port S parameters. The S parameter is converted into impedance to calculate the complex permittivity using Matlab program. Techniques used to overcome the air gap and stray capacitance was described. Measurement obtained using the proposed method was compared with the free space method to validate its accuracy. The percent difference is less than 5%.     

Multiport vector network analyzer calibration using the generalized 3-term error model

A generalized 3-term error model, where only three error matrixes are defined, is proposed for the calibration of n-port vector network analyzer (VNA) with n + 1 measurement channels. In this model, the node is replaced by the complex vector, and correspondingly the branch gain is represented by the complex square matrix. According to this error model, which also obeys the fundamental rules of flow graph, the formula for actual scattering matrix of an n-port DUT can be deduced. Finally, the actual S-parameters of a four-port device can be corrected and they are compared with the measurement results by Agilent VNA E5071B. The good agreement attests the precision of the calibration algorithm.     

基于全参数化建模的工业货架设计分析系统

采用基于对象的分析方法，系统地研究了数百套包括AS／RS、VNA、APR等各类立体仓库货架的结构和设计方案，分析归纳出工业货架的通用层次化结构模型和全参数化模型，提出了“系统设计-结构设计-组件设计-构件设计”的货架层次化设计方法。基于该模型和方法开发的工业货架设计分析系统软件具有进行货架规划设计、有限元分析和工程报价的功能，可以自动生成规划设计报告、有限元分析报告、CAD设计图纸和工程报价清单。该系统为物流系统集成企业、物流设备生产企业和物流工程咨询企业提供了一个高效快捷、准确科学的设计和分析工具。