运用网络分析仪对滤波器和放大器进行准确测量

本文基于采用网络分析仪进行测试中经常遇到的测试考虑进行探讨。更好的使用网络分析仪以获得准确的测试结果。     

Multiport scattering matrix measurement using a reduced-port network analyzer

A novel method for acquiring the scattering matrix of an n-port network from measurements using a reduced-port network analyzer is developed. This method can obtain the scattering matrix of a nonreciprocal or reciprocal n-port network with the use of a three- or two-port network analyzer. The formulation of this method considers the imperfection of terminators used in the measurement, and only two of the terminators are required to be known. Experimental results from a four-port microstrip circuit show good accuracy using the developed method.     

Accurate measurement of signals close to the noise floor on aspectrum analyzer

Because most spectrum analyzers are calibrated to read the true power of a sinusoidal signal, a correction factor is necessary to read the true power of a nonsinusoidal signal, such as noise. Consequently, when noise and a sine wave are both present, a correction factor that is a function of the signal-to-noise ratio is necessary to find the true signal power. For some spectrum analyzers the correction factor for pure noise is incorporated into the software, but the correction factor for signal-plus-noise is generally ignored. The authors derive this correction factor, which is significant where the signal-to-noise ratio is near unity     

Time-resolved measurements using conventional analog network analyzer

A new method of making precise time-resolved measurements using an unmodified analog network analyzer is described. This technique is most useful in wafer probing unpackaged acoustic devices in production conditions or in characterizing development acoustic devices that are packaged to allow easy physical access to the device and which may, therefore, exhibit high levels of RF feedthrough.     

矢量网络分析仪反射测量误差分析与修正

本文介绍了定向耦合器在矢量网络分析仪反射测量中的作用,分析了定向耦合器导致方向性误差的原因:耦合端出现的信号中包含有泄漏过去的非理想信号,在定向耦合器的耦合端口是被测件反射的信号,是理想的被测信号,但实际的定向耦合器并不理想,一小部分信号在经被测件反射之前便泄漏到了耦合端口.耦合端口的信号中包含有泄漏过去的非理想信号,...     

Computer correction of a microwave network analyzer without accurate frequency measurement

A method of calibration is described that uses three devices at a common reference plane, eliminating the requirement for accurate frequency measurement. The theoretical approach is supplemented with practical results and a discussion of the sources of error.     

Accurate and fast speed measurement using ramp-waveform samplingtechnique

A novel “ramp-waveform sampling technique” for accurate and fast speed measurement is presented. Square pulses from an encoder are turned into ramps using analog electronics. They are then sampled, and linear regression is used on ramp-waveform sample points to extrapolate backward and determine the starting point of each pulse very accurately     

Modeling and measurement of contact resistances

This paper presents a generalized model of ohmic contacts and a unified approach for the accurate extraction of specific contact resistivity (ρc) for ohmic contacts from measured contact resistance using the cross bridge Kelvin resistor, the contact end resistor, and the tranmsission line tap resistor test structures. A general three-dimensional (3-D) model of the contacts has been developed from the first principles and has been reduced to 2-D, 1-D, and 0-D (one lump) models with the necessary approximations. It is shown that the conventional I-D models overestimate the value of ρcbecause of the parasitic resistance due to 2-D current flow around the periphery of the contact window. Using 2-D simulations, we have accurately modeled the current crowding effects and have extracted accurate values of ρcindependent of contact size and the test structure type. A theory of scaling of contacts has been developed and is applied to commonly used structures. A universal set of curves has been derived for each particular contact resistance test structure and, given the geometry of the structure, these allow accurate determination of ρc, Without the actual use of the 2-D simulator. Experimental and theoretical accuracy of the three test structures has been compared. Accurate values of ρcfor various contact materials to n⁺and ρ⁺Si have been determined. The data confirm that in the past researchers have overestimated ρc, and that ρcwill not limit device performance even with submicrometer design rules.     

Accurate measurement of three-dimensional knee replacementkinematics using single-plane fluoroscopy

A simple extension of a previously reported object recognition technique has been used to implement a six-degree-of-freedom position/orientation estimator for the measurement of knee replacement motion from two-dimensional (2-D) fluoroscopic images. Computer modeling studies and controlled mechanical tests were performed to assess the accuracy of the technique. The results indicate that knee rotations can be measured with an accuracy of approximately one degree and that sagittal plane translations can be measured with an accuracy of approximately 0.5 mm. The measurement technique is uniquely well suited for performing dynamic kinematic measurements on individuals with knee replacements, and for performing comparative studies among subjects with different designs of knee replacements     

频率的精确测量

一般使用的频率计有下面几种. *射频频率计--最高频率到3GHz左右的精确频率测量 *微波频率计--最高频率到40GHz左右的精确频率测量 *调制域分析仪--从调制域的某些参量(如:相位误差)计算频率,多用于数字系统等     

Accurate measurement,using natural sunlight,of silicon solar cells

The light source is very important when measuring solar cells. Commonly used light sources—good‐quality solar simulators—are expensive and have far from ideal characteristics. Computer modelling described in this work strongly suggests that testing of silicon solar cells under natural sunlight is simpler, cheaper, and more accurate than all but the most careful simulator measurements. Direct‐beam solar spectra were generated with the model SMARTS2 for a range of atmospheric conditions, and a broad range of silicon cells (efficiencies 6–25%) were then simulated under these spectra. These simulations showed that measurement uncertainty of less than 5% should be achievable. Climate data for locations within 45° of the equator show that the required atmospheric conditions should occur commonly in summer. Finally, it is shown that the important atmospheric conditions can be measured without expensive equipment. Copyright © 2004 John Wiley & Sons, Ltd.     

Accurate measurement of intrathoracic airways

Airway geometry measurements can provide information regarding pulmonary physiology and pathophysiology. There has been considerable interest in measuring intrathoracic airways in two-dimensional (2-D) slices from volumetric X-ray computed tomography (CT). Such measurements can be used to evaluate and track the progression of diseases affecting the airways. A popular airway measurement method uses the “half-max” criteria, in which the gray level at the airway wall is estimated to be halfway between the minimum and maximum gray levels along a ray crossing the edge. However, because the scanning process introduces blurring, the half-max approach may not be applicable across all airway sizes. The authors propose a new measurement method based on a model of the scanning process. In their approach, they examine the gray-level profile of a ray crossing the airway wall and use a maximum-likelihood method to estimate the airway inner and outer radius. Using CT scans of a physical phantom, the authors present results showing that the new approach is more accurate than the half-max method at estimating wall location for thin-walled airways     

扫频式频谱分析仪测量雷达发射功率误差分析

针对雷达功率测量问题,提出了运用频谱分析仪测量发射功率的方法并对该方法进行了误差分析。首先分析了频域测量发射功率的原理性误差,推导出了理论误差系数并进行了仿真分析,然后通过分析扫频式频谱分析仪的工作原理,列出了影响频谱分析仪实际测量精度的硬件要素,研究了硬件实现中的误差系数,最后得出了该方法测量功率所得结果与实际功率的关系表达式。     

Improving time-domain measurements with a network analyzer using arobust rational interpolation technique

A method to efficiently and accurately compute a time-domain waveform from a network-analyzer frequency-domain measurement is presented in this paper. The method is based on a robust interpolation technique to construct a pole-residue representation of the response of the device-under-test. First, the rational function is expressed in terms of Chebyshev polynomials, instead of the usual power series, to accurately determine the poles of the network over a wide frequency range. The properties of a passive system are then utilized to efficiently calculate the residues. The resulting pole-residue model is analytically transformed to obtain the time-domain response in any time window, beyond the limitations of the discrete Fourier transform (DFT) technique. Unlike the DFT technique, the method does not require a large number of equally spaced harmonically related frequency points. The parametric model can also be used to economically store large measurement data. The proposed procedure is computationally inexpensive and less sensitive to numerical instability. To illustrate the validity of the method, examples of frequency- and time-domain measurements of a Beatty structure and simulation data of a low-pass Butterworth filter are given     

脉冲激光能量的准确测量

本文介绍一种补偿锥腔量热计，进行了脉冲激光能量的准确测量，并对电脉冲和激光脉冲情况下的动态非等效性进行了研究。量热计辐射（能量）灵敏度的总的不确定度为0.2％。使用光学快门和稳定的连续氩离子激光时，比对量热计和绝对辐射（功率）计，两种标度符合0．05％以内。     

扫频法精确测量高速光调制器频率响应

同微波网络一样,可以用S参数来精确描述光电子器件的性能.根据微波网络的S参数,详细推导了光电子器件的S参数.搭建了40 GHz高速测试系统,利用矢量网络分析仪(带宽40 GHz)和作为参考的标准高速光探测器(带宽45 GHz),测量了宽带光强度调制器(实测带宽35 GHz)的频率响应.理论上,通过S参数和T参数的互相转换,扣除了微波放大器对测试结果的影响.在120 MHz～35 GHz范围内,测得的结果与出厂数据取得了很好的一致性.文中通过合理的简化,得到了光调制器频率响应的简明表达式,从而降低了数据处理的复杂度.     

网络分析仪数据处理分析

在分析讨论了网络分析仪数据处理过程的基础上,提出了线性内插算法,并用具有两种扫描方式的网络分析仪对算法进行验证。结果表明：通过线性内插算法,两种扫描方式得到的5参数测量值之间的差值与定制频率扫描方式下测量值的标准偏差相近,因此能较好地解决频率点不一致带来的问题;此外,也为分析相位测量数据异常提供了有力的工具。     

A multiline method of network analyzer calibration

The author presents a method for the calibration of network analyzers. The essential feature is the use of multiple, redundant transmission line standards. The additional information provided by the redundant standards is used to minimize the effects of random errors, such as those caused by imperfect connector repeatability. The resulting method exhibits improvements in both accuracy and bandwidth over conventional methods. The basis of the statistical treatment is a linearized error analysis of the TRL (thru-reflect-line) calibration method. The analysis presented is useful in the assessment of calibration accuracy. It also yields results relevant to the choice of standards.<>     

基于可信度量的网络组件性能评估方法

针对新型网络及其服务构建中所涉及的网络组件选择问题,以可信评估思想为指导,通过多属性决策建模,提出一种网络组件性能评估方法。首先,针对网络应用环境的灵活多变特征,设计了一种按需驱动的可信指标树动态构建策略。其次,利用模糊层次分析法减小主观权重计算的不确定性,并将主客观权重相结合以提高赋权操作的公平性。最后,在评估决策阶段,综合运用指标数据效用转换、可信属性向量构造和向量间的相对近似度计算等策略得到评估结果。通过对软件定义网络控制器的实际案例分析,验证了所提评估方法的合理性及有效性。