Precision Microwave Waveguide Loss Calibrations

Precision microwave insertion-loss measurements are an important part of the evaluation and calibration of the Jet Propulsion Laboratory-NASA low-noise deep-space communication systems. A study of cooled transmission-line components was initiated with the Rantec Corporation in July 1966. The preliminary work at Rantec involved WR 430 waveguide insertion-loss calibrations using a microwave cavity Q technique. JPL verified the technique by repeating the calibration using a direct insertion-loss measurement technique between matched components. The JPL measurements are described in detail, and the critical areas identified. The difference between the reported JPL (0.00427 dB) and Rantec (0.00414 dB) measurements of 0.00013 dB is within experimental accuracies and adds to the confidence factor of both measurement techniques.     

A Portable Microwave Phase and Amplitude Test Set

Phase alignment at microwave frequencies may be made to 0.1° or less, and amplitude balance to 0.1 dB may be made simultaneously with this fully solid-state test set which is designed to be comparable in size and weight to a Tektronix oscilloscope. Provisions are incorporated for testing with either pulsed or CW signals. Present means of measuring phase and amplitude differences at microwave frequencies require either rack size equipments or a group of various pieces of test equipment such as RF generators, standing wave indicators, and slotted lines. Standard procedures are to utilize slotted lines with VSWR sampling points using a short-circuited line or line-swapping arrangement. While these methods are versatile, all have limitations in resolution and accuracy while requiring long setup times and a high degree of skill by the operator. Operating at a single-crystal-controlled microwave frequency, this test set provides a means of continuously comparing two signals, one a reference or standard; the other a signal to be adjusted. The phase and amplitude difference between these two signals may be reduced to a null by adjusting the module under test while observing two zero-center balance meters. The signals may be read to ±3 dB and ±3.0° or ±90° full scale. Accuracy is better than 5 per cent for all scales, and the null resolution is ±0.05 dB and ±0.05°. A self-contained solid-state reference signal generator produces up to 3-watts power output from a balanced varactor double stage at 1296 Mc.     

Magnetic Potentiometer of High Precision

A magnetic potentiometer is described, the measuring error of which is in the order of 0.1 percent. The measuring winding is on polished straight ceramic rods, the joints of which are kept free from magnetic field by magnetic screening. Thus a measuring frame for heavy currents arises, the mutual inductance of which is independent of the primary circuit situation and of neighboring busbars. The exact measurement of the ac voltages induced can be made with the aid of measuring contacts or also with integrating electronic amplifiers, so that the rms value, fundamental oscillation, and harmonics and phase angle of heavy currents can be measured reliably. The practical error effects in these devices have been examined by the Physikalisch-Technische Bundesanstalt, Berlin.     

精密LCR测试技术研究

介绍了一种L、C、R测试系统,可以在75kHz～30MHz频率范围内对元器件进行精密测量。阐述了测试系统中的关键技术:包括自动平衡电桥法阻抗测量技术、75kHz～30MHz频率合成源技术、自动电平控制技术、鉴相及矢量测量技术、A D变换技术和四端对结构。研究了测试系统的误差来源及消除误差的方法,给出了系统的校准件的数学模型,并据此模型对系统的分布参量误差、频响误差等进行测量校准。最后给出了实验结果,系统的准确度为0 1%,被测件DUT上所加信号频率为75kHz～30MHz,以100Hz步进,幅度在5mV～2V范围内连续可调。     

A New Precision Automatic Microwave Measurement System

The Hewlett-Packard computer-controlled network analyzer performs fully automatic rapid characterizations of passive and active networks through their scattering parameters. It is extremely flexible in both measurement capability and presentation results, and provides standards laboratory accuracy. System operation is discussed, and in particular, the sources of error involved in making such measurements are dealt with: imperfect standards used for calibration, instrumentation, and signal source accuracy and repeatability errors. Total system accuracies and some measurement results are given.     

The Calibration of a Precision Potentiometer Using a Minimum of Special-Purpose Equipment

A method of calibrating a potentiometer, at the part-per-million level with a minimum of special-purpose equipment, is described. The technique is illustrated by application to a particular instrument with numerical values drawn from a particular calibration. The required accuracies are shown to be attainable with usual laboratory equipment.     

应用1281型数字多用表检定高准确度直流电位差计

本文主要论述用1281型数字多用表检定0.002级高准确度电阻型直流电位差计的检定原理,着重进行了测量不确定度分析.     

微波紧缩场面板的精密检测与定位

介绍了一种微波紧缩场面板的精密检测与定位方法.该方法利用跟踪仪的高精度测距功能,采用网格扫描的测量方法,检测微波紧缩场面板的面型参数,面型RMS值的测量不确定度小于0.005 mm;通过设置辅助观测点,将面板的定位偏差转移到辅助点上,动态调整辅助点可以快速解决面板的定位问题.     

Precision Detector for Complex Insertion Ratio Measuring Systems

A precision, low-noise, highly sensitive, synchronous RF detector is described that permits simultaneous phase and level nulling in complex insertion ratio measuring systems. This insertion ratio is a measure of both the phase shift and magnitude change produced by a network when inserted in a transmission path.     

A Semi-Automatic Method for the Precision Measurement of Microwave Impedance

A system is described for the measurement of the magnitude and phase of the reflection coefficient over wide frequency bands. The method consists of recording the voltage at several points along the standing-wave pattern in a coaxial line. A fixed probe is used and the distance between the probe and the load is altered by successively inserting several lengths of precision coaxial line. Knowing these lengths and the frequency of the signal, a curve representing the standing-wave pattern is fitted to the experimental points by means of a computer program performing a least-squares minimization. To cover a given frequency band, the frequency is changed in discrete steps and the corresponding probe voltage recorded automatically. The measured impedance is referred directly to the characteristic impedance of air-dielectric coaxial lines.     

道路声屏障降噪理论的研究进展

道路声屏障降噪理论的发展是新型高效声屏障设计的基础, 根据声屏障降噪理论的发展历程将其分为几何与波动声学理论、试验与半经验理论以及边界元理论三种,综述了各自的基本原理和研究进展,比较分析了三种理论的特点和实用范围,为声屏障优化设计提供理论参考.     

Error in Insertion Loss Measurement Due to Multiple Reflections

A system error of a waveguide impedance bridge due to multiple reflections between the test section and the bridge circuit is analyzed. A principle and a method of making corrections to this system error are presented with actual numerical examples.     

Time-Domain Reflectometer Measurement of Insertion Loss of High-Frequency Switches

High-frequency switches of the reed relay type have insertion losses of the order of 0.1 dB. The insertion loss is primarily the result of large skin effect impedance in the magnetically active portion of the signal path. This paper presents a novel time-domain reflectometer technique for measuring this skin effect impedance in the time domain then shows how a Fourier transform will convert the readings to either an impedance or insertion loss in the frequency domain. The method uses inexpensive equipment, is very accurate, and is fast since only a single voltage measurement at one instant of time is needed for the determination of the insertion loss at a desired frequency. Precision of at least 0.001 dB is achievable.     

Precision Model for Microwave Rotary Vane Attenuator

A model for a rotary vane attenuator is developed to describe the attenuator reflection and transmission coefficients in detail. All the parameters of the model can be measured in situ, i.e., without diassembling any part. The tranmission errors caused by internal reflections are calculated from measurements of the much larger reflection parameters, hence commonly used nonprecision instruments can be used to determine the transmission errors with sufficient accuracy for the highest precision obtainable in standard laboratories.     

基于里德堡原子的微波功率精密测量

提出一种基于里德堡原子量子相干效应的功率测量新方法。将装有铷蒸气的低电磁扰动原子气室置于特定的导波系统中,基于里德堡原子量子相干效应将对导波电场测量转化为对原子吸收光谱的探测,利用功率和导波电场的解析量化关系,实现一种全新的可溯源至普朗克常数的微波功率测量。在10.22GHz频率处与传统功率测量进行比较,-40dBm至-20dBm的功率范围内两者平均偏差为0.08dB(1.86%)。这种全新的微波功率量子测量方法具有灵敏度高、动态范围大、测量不确定度小等优势,有望形成新一代可直接溯源至国际单位制(SI)的微波功率基准。     

微波衰减精密测量方法研究

本文结合工作实际,重点分析微波衰减量的多种精密测量方法,并阐明了各种方法的工作原理和优缺点,以便在实际应用中根据被测对象不同选择最优的测试方案,从而提高微波衰减测量的准确度。     

吸波材料的基础研究及微波损耗机理的探讨

从物理学和材料学的观点,较为系统地总结了制备吸波材料的基础研究,并探讨了传统肖波材料及新型纳米吸波材料的微波损耗机理,最后,对吸波材料研究的发展向提出了一些见解。     

数字微波通信综合测试系统

数字微波通信综合测试仪是将十几台仪器的测试功能集成在一个测试系统中。它可以对数字微波通信系统的大部分参量进行测量 ,特别适合于数字微波移动通信系统的测量。本文简要介绍了数字微波通信综合测试仪的原理和应用。     

双法兰式三阀组阀体多向精密成形工艺

目的研究双法兰式三阀组阀体多向精密成形工艺。方法根据双法兰式三阀组阀体的结构特点,提出其多项精密成形工艺方案。采用Deform-3D有限元分析软件,对提出的工艺方案进行数值模拟,分析载荷-行程曲线、金属流动规律等,最后进行工艺试验。结果多向精密成形工艺方案可在模具许用应力范围内成形双法兰式三阀组阀体,工艺试验获得的锻件充填饱满,所获数据与模拟结果基本一致。结论双法兰式三阀组阀体多向精密成形工艺是可行的,对实际生产及其他相似零件具有指导意义。     

填料对阻尼隔声材料的水中插入损失的影响

本文研究了空心玻璃微珠、粉煤灰 (煤胞 )、发泡聚合物等填料对阻尼隔声橡胶材料水中插入损失的影响 ,发现橡胶中加入隔声填料可以明显提高水中插入损失。其中玻璃微珠插入损失最大 ,其次是粉煤灰 ,再次为发泡聚合物 ,而前三者等量混合物略差。玻璃微珠用量以 3 0份为宜 ,水中插入损失随用量增加而降低 ,在3kHz、1 0kHz、2 0kHz三个频段 ,用量 3 0份至 5 0份时 ,插入损失降低幅度较大 ,5 0份以后降低幅度变缓 ,其他频率也有类似情况