WR-42功率基准系统有效效率不确定度评定

WR-42功率基准是一套微量热计系统,利用直流替代及量热技术对被测热敏电阻型功率座的有效效率进行定标。对WR-42功率基准系统中有效效率不确定度评定的过程进行了介绍,并给出了有效效率的测量结果与不确定度的评定结果。该基准的研制成功,填补了18～26.5GHz频段的空白,结合其它功率基准,使我国射频与微波功率计量基准频段从10MHz连续覆盖到了220GHz。     

WR-22微波功率基准工作原理及其不确定度

微波功率基准利用直流替代及量热技术对被测热敏电阻型功率座的有效效率进行定标。本文对研制的WR-22（33GHzto50GHz）功率基准的工作原理进行了分析，给出了基准装置不确定度评定结果。     

微波小功率校准系统在K波段的应用

通过对现有的K波段微波功率敏感器校准方法的研究,提出了利用研制的偏置功率匹配器,采用传递标准法,组成了低反射系数等效信号源结构的新方案,实现了对K波段微波功率敏感器的准确校准,并对测量不确定度来源进行了分析与评定.     

宽带微波中功率计量标准装置

本文描述了新近研制的０．４—１８ＧＨｚ，１—２０Ｗ中功率计量标准装置．该装置用瓦级量热计／中功率衰减器组合构成中功率标准，用单定向耦合器作为传递标准．中功率标准校准因子Ｋｓ的不确定度为（１．４—２．９２）％；校准因子的传递不确定度为（１．６３～３．６４）％．该装置为半自动测量系统．     

低反射系数等效信号源的测试方法研究

目前微波小功率标准装置采用低反射系数等效信号源结构,在量值传递过程中,等效信号源反射系数的大小是影响系统测量准确度的关键,而信号源输出端反射系数的测量一直是微波计量中的技术难题.对等效信号源反射系数的常用测试方法进行了介绍,结果表明,大失配功率座法适用于各种等效信号源的反射系数的测量.     

扫频反射系数调试的一种实现方法

现阶段的驻波扫频测量调试大多采用网络分析仪,但是对器件进行驻波扫频调试时,特别是调试时间较长的情况下,可以用扫频反射计,所用设备为一台高方向性定向耦合器、一台精密衰减器和一个标准失配负载或全反射短路负载;在信号源的输出定标很准确的情况下,可以不用精密衰减器调节衰减量,改为直接调节信号源的输出电平,设定出所需反射系数进行器件的反射系数调试,此时所用设备少,在实验室内很容易实现.笔者对此时装置的不确定度进行了分析,结果表明,采用短路负载来设定反射系数效果会好得多.     

26.5—40GHz频段S参数标准──双六端口网络分析仪

本文描述一种高精确度双六端口网络分析仪,将其用作26.5～40 GHz频段的计量标准装置,可校准单端口器件的复反射系数、二端口器件的衰减和相移以及测量二端口的S参数。对该装置的不确定度作了理论分析和实验评定,并经误差合成给出了该装置的测量不确定度指标。     

Rossini型气体热量计电校正实验与分析

Rossini型气体热量计是目前测量准确度最高的气体热值测定装置,在研制过程中,量热容器的当量热容是实验装置的一个重要参数,采用电校正方法能够准确地测量其当量热容。为保证电校正实验与燃烧实验的一致性,实验中要做到电加热功率与燃烧功率完全相同,之后通过测量燃烧器周围吸热介质的温升分析得到量热容器的当量热容。实验结果表明:在电加热功率与燃烧功率一致的情况下,两种实验中燃烧器周围吸热介质的温升曲线完全吻合,测得量热容器的当量热容为19 023 J/K,当量热容测量不确定度为28 J/K,其相对不确定度为0.15%。     

基于高精度功率计的六端口反射计系统

本文研究了采用USB接口高精度功率计进行功率采样的波导六端口反射计系统,该系统由波导对称五端口环形结与定向耦合器组成六端口反射计电路,实现了集功率采样、校准、测量于一体的自动化处理。该系统可用于高精度计量工作和工程上的介质参数以及负载参数的测量。实际电路测试结果表明,功率计的改进提高了测量系统的精度。     

毫米波WR-15（50~75 GHz）国家功率基准的研制

介绍了一种基于热敏电阻功率座的对称双线结构的WR-15（50~75 GHz）矩形波导微量热计的设计及传递标准有效效率计算方法。给出了功率基准热电堆测量曲线及该频段毫米波功率传递标准量值结果。该微量热计将作为我国50~75 GHz毫米波功率基准,将我国的毫米波功率测量能力提高到75 GHz。     

Precision Coaxial VSWR Measurements by Coupled Sliding-Load Technique

The method described employs a slotted line for VSWR measurement and a precision coaxial line as an impedance standard. A sliding load terminates the standard line during the process of transforming the impedance of the slotted line to that of the standard line. This load is coupled mechanically to the slotted-line probe so that the two move together. The VSWR seen by the probe is then, to first approximation, only that due to the reflection from the junction of the two lines. It is simple, therefore, to tune out the residual reflection without requiring a perfect load. The slotted line is then effectively transformed to the impedance of the standard line, and subsequent measurements made with it at the same frequency indicate VSWR with respect to the standard line. In order to minimize the effect of amplitude fluctuations of the RF source and to expand the scale, the detected probe output is compared with the detected output of a directional coupler monitoring the incident power. The difference is recorded with a strip recorder; the paper transport of the recorder is synchronized with the probe travel. In describing the method, considerable background material is presented on other precision impedance-measuring methods and techniques and on the general state-of-the-art. Theory, accuracy, system details, and results are given. The system appears capable of making absolute impedance measurements on a low VSWR termination to a maximum possible error in reflection coefficient of 0.0012.     

A Multistate Reflectometer

Precise measurement of complex reflection coefficient and power sensor effective efficiency is reported using a reflectometer comprising two detectors and two directional couplers, one coupler having connected to it a reflector able to switch to different stable states. Results were obtained in three waveguide bands spanning 8.2-26.5 GHz.     

Calibration and Use of a Reference Standard Directional Coupler for Measurement of Large Coupling Factors

Fixed frequency, point-by-point calibration is outlined for a reference standard directional coupler to be used in steppedfrequency measurement of 40-dB, or greater, coupling factors of directional couplers. If a reference directional coupler has a 40-dB coupling factor, a main-line waveguide output, and a sexless coaxial side-arm output, the best accuracy obtainable in measurement of its coupling factor is estimated to be ±0.03 dB.     

A Millimeter Wave Complex Reflection Coeficient Scanner

A broadband microwave measurement system has been designed to make complex reflection coefficient measurements on a swept basis at millineter wave frequencies. This instrument covers a frequency range of 50-75 GHz in WR-15 rectangular waveguide. Two appliques are being added in WR-22 and WR-10 waveguide to extend the frequency range of the system to 33-110 GHz. Measurements can be made while sweeping over bands as wide as 10 GHz. An interesting feature of the complex reflection coefficient scanner is that residuals, or baseline, of the system are automatically subtracted. The resultant output display is a real-time polar plot of the actual reflection coefficient of the network under test. Residuals of 0.03 for reflection coefficients around unity, and 0.013 for reflection coefficients around zero can be measured with a resolution of 0.01 while sweeping over a 5 GHz band. A maximum reflection coefficient range of 46 dB has been achieved using straightforward video detection techniques. For measurements of networks with very low reflection coefficients (0.01 and lower) a time averaging feature is available to reduce the effects of random noise. The complex reflection coefficient of the unknown can be displayed on an oscilioscope and photographed, or read out on an X-Y plotter.     

对两种吸声系数测量方法的讨论

某黑色聚氨酯材料样本放置于自行设计的管道脉冲吸声测量装置的管道中间以及管道末端并紧贴刚性背衬两种情况下,利用产生的1ms的巴特沃斯函数声脉冲测量其吸声系数。样本放于声管末端的反射法测量结果与B＆K4206阻抗管测量结果相近;而放于声管中间的透射法测量结果与反射法有区别。从声能量角度解算了两种测量的平均吸声系数表明：相比于单层样品,双层样品的透射法测量结果与反射法更接近。     

Optical switching in a symmetric three-waveguide nonlinear directional coupler

In this paper we study optical switching in a system of a three-waveguide nonlinear directional coupler. We consider a waveguide structure with three parallel waveguides in a linear, symmetric coupling configuration. We work in the case that the (absolute value of the) difference of the propagation constants of the outer and centre waveguides is much larger than the linear coupling constants. When one of the outer waveguides is initially excited, we show that for small values of the initial power the system behaves as a two-waveguide nonlinear directional coupler where only the two outer waveguides are involved in the switching. For larger values of the initial power, transfer of light between the initially excited waveguide and the centre waveguide is observed.     

Automated Characterization of Bolometric and Electrothermic Mounts

The greatest inaccuracy in making a microwave power measurement is usually the uncertainty of the calibration factor or the effective efficiency. These terms account for the RF losses and substitution errors in the bolometric or electrothermic mount. A new method for transferring calibration from a standard mount to a mount to be calibrated has production line speed and simplicity; yet its accuracy rivals standards laboratory techniques. This method uses an automatic network analyzer to measure the quantities required and to solve the mismatch equation in transferring calibration from the standard mount to the one to be calibrated. A technique is also described to evaluate the errors of the transfer measurement. An accurate method of measuring the complex reflection coefficient of a stabilized source is another result of this work. The present implementation measures effective efficiency, calibration factor, and the magnitude and phase of the reflection coefficient of a mount at six calibration frequencies in 60 seconds. The uncertainty in transferring calibration factor and effective efficiency is about 0.5 percent.