Impossibility of Linear Two-Port Noise-Parameter Measurement with a Single Temperature Noise Source

The noise parameters of a linear two-port are usually evaluated through four measurements of the noise figure of the two-port, and the noise figure is in turn determined through the measurements of the noise power output of the two-port when a noise source is connected at its input. It is shown that if the noise power output is the only measured quantity, then the noise parameters cannot be calculated from measurements carried out with a single value of the source noise temperature. The minimum requirements for the determination of noise parameters are established.     

Dielectric plug-loaded two-port transmission line measurementtechnique for dielectric property characterization of granular andliquid materials

There are numerous dielectric property characterization techniques available in the microwave regime each with its own uniqueness, advantages and disadvantages. The two-port completely-filled waveguide (transmission line) technique is a robust measurement approach which is well suited for solid dielectric materials. In this case, the dielectric material can be relatively easily machined to fit inside the waveguide and the subsequent measurement of the scattering parameters of this two-port device renders the dielectric properties of the material filling the waveguide. However, this technique is not well suited for measuring the dielectric properties of granular and liquid materials. These materials are used in the production of various composites which are increasingly replacing the use of metals in many environments. If this technique is directly applied to these types of materials, several approximations either in the measurement apparatus or the formulation must be made. To overcome this problem, this paper describes a modification to this measurement technique utilizing two dielectric plugs which are used to house the granular or the liquid dielectric material. In this approach no approximation to the measurement apparatus is made while the presence of the plugs are fully accounted for in the derivations. Using this technique, the dielectric properties of cement powder, corn oil, antifreeze solution and tap water, constituting low- and high-loss dielectric materials (granular and liquid) were measured. In addition, the important issue of measurement uncertainty associated with this technique is also fully addressed. The issue of optimal choice of various measurement parameters is also discussed as it relates to the measurement uncertainty     

Source Mismatch Effects on Measurements of Linear Two-Port Noise Temperatures

A noticeable source mismatch occurs in measurements of noise parameters of a linear two-port, since an admittance-transformer network between the source and the two-port must be inserted. A generalized analysis of the source mismatch effects on noise measurements, which considers the dependence of the noise performance of the two-port on the input admittance, is presented here. On this basis, two types of noise generators are considered and compared with each other.     

A New Method to Extract Noise Parameters Based on a Frequency- and Time-Domain Analysis of Noise Power Measurements

A new on-wafer noise parameter measurement method at a 2.8-18-GHz frequency band is presented. This measurement method is based on both temporal and spectral analysis of noise power measurements. We present the method and the experimental results on an active two-port. It requires less equipment than the classic noise parameter measurement method. It gives direct results for 801 points in the 2.8-18-GHz frequency band.     

De-embedding two-port noise parameters using a noise wave model

Equations are presented, suitable for computer or calculator, for accurately de-embedding the noise parameters of both the first and the second two-port in a cascade of noisy two-parts from known values of the noise parameters of the cascade. The derivations are presented in terms of a noise wave model for two-ports, using transfer scattering small signal parameters. A numerical example is presented in which the noise parameters of two cascaded passive two-ports having unequal physical temperatures are individually de-embedded from the noise parameters of the cascade. As a check on the analysis presented, the noise parameters of each two-port are also calculated directly from its scattering parameters and physical temperature     

利用矢量网络分析仪单端口校准误差项提取二端口网络的S参数

提出了一种利用矢量网络分析仪单端口校准误差项提取互易二端口网络S参数的方法。该方法要求在不同的参考平面上分别进行两次单端口校准,然后利用两次单端口校准的误差项求解二端口网络的S参数,通过实验验证该方法的正确性。该方法可应用于负载牵引和噪声参数测量过程中阻抗调配网络的S参数提取。     

A Binary Phase-Modulation Technique of Measuring Microwave Phase Shift

A precision measurement system for the differential phase shift of a two-port device has been developed. The system is based on a two-channel circuit of which the phase of one channel is shifted 90° back and forth periodically. The response of the system is essentially independent on an amplitude change which is usually accompanied by the phase shift of the two-port device. An X-band measurement system has been constructed and examined. It is proved that the system has 0.02° resolution in phase angle. This system is also applied for the precise attenuation measurement by using a similar technique to the modulated subcarrier technique.     

A New Technique for the Direct Measurement of Y-Parameters at Microwave Frequencies

A technique has been developed which makes practical the direct measurement of active device two-port y-parameters at microwave frequencies. The instrumentation involved is a simple modification of a conventional s-parameter test set, and the measurement procedure is only slightly more complicated than in a conventional s parameter measurement.     

The Development of a Practical,Drift-Free,Johnson-Noise Thermometer for Industrial Applications

Johnson noise thermometers measure a phenomenon that is directly linked to thermodynamic temperature by a fundamental physical law. The measurement of Johnson noise therefore offers the prospect of realizing a drift-free thermometer. Despite previous attempts to produce a practical Johnson noise thermometer for industrial applications, the technique is currently used only in niche research applications to explore discrepancies between practical temperature scales and thermodynamic temperature, or to determine Boltzmann’s constant. This has largely been due to the historical use of switched correlators to measure Johnson noise, which limits the sense resistance and measurement bandwidth that can be employed. This constraint limits the Johnson noise signal to levels near the limits of measurement. A new technique that eliminates switching and thereby allows the use of much higher sense resistances and bandwidths to increase the Johnson noise signal is presented. The signal power achieved is significantly higher than for systems using a switched correlator. Results so far indicate that measurement performance is compatible with the requirements of industrial applications. Specifically, uncertainties of \({<}0.3 \, {^{\circ }}\hbox {C}\) (95 % confidence) were demonstrated for measurements near ambient temperature with a measurement time of only 7 s.     

Methods for direct-reading noise measurements of low-gain two-ports

This paper describes direct-reading measurement methods of noise figure F_m displayed by an automatic noise figure indicator. The F_m readings should be equal to F_x, which are the true noise figure values of the two-port under test, regardless of its available power gain G_Ax, and the noise figure of the measurement receiver F_t. Technical problems of these F_x direct readings are shown. They particularly occur while using the conventional measurement methods. Methods that allow elimination of the influence of the F_r value on F_m readings as well as the influence of both F_r and G_ax on F_m are discussed. An important advantage of using the method with elimination of the F_r value is presented. Formulas are given which allow the estimation of the technical requirements for additional blocks of measurement systems or to count measurement error components, specific for the chosen measurement method     

Parametric identification of two-port models in the frequencydomain

The authors treat the problem of parametric estimation of linear time-invariant dynamic two-port models (e.g. the short-circuit admittance matrix) from experimental data. A multivariate frequency-domain Gaussian maximum likelihood estimator is proposed to estimate the unknown coefficients occurring in the rational two-port model. It takes the perturbing noise of all the measured voltages and currents into account. The covariance matrix of the noise is assumed to be known, e.g. from measurements. The estimates and their covariance matrix are obtained as the result of an optimization procedure. The value of the minimized loss function and the covariance matrix of the estimates can be used to determine the model structure. The ability of the estimator to handle real measurement problems is demonstrated by means of experimental results. Using the estimated two-part parameters of an unloaded band-pass filter, it was possible to predict the transfer function of the loaded filter within an error of ±0.01 dB on the magnitude and ±0.1° on the phase     

PCB导线上下线宽检测算法研究

针对PCB导线的上下线宽的测量,提出了快速而且精确的边缘提取算法。由于采集的显微图像中有很强噪声,一般常用除噪方法很容易破坏图像的边缘信息。采用P-M模型进行除噪,这种方法最大的优点是能够在除噪的同时保护甚至增强图像的边缘;利用Canny算子对降噪图像提取边缘点;最后进行Hough直线拟合。实验证明该方法不仅有很强的抗噪声能力,能够保持边缘信息和测量的精度,并且满足工程测量的实际要求。     

Accuracy and precision of single-pulse one-dimensional vibrational coherent anti-Stokes Raman-scattering temperature measurements

The accuracy and precision of time-resolved one-dimensional temperature measurements using single-pulse one-dimensional N(2) vibrational coherent anti-Stokes Raman scattering along a line have been investigated in air in the temperature range from 300 to 1500 K. For this, the experimental spectra were taken in a high-temperature oven at atmospheric pressure. A planar BOXCARS phase-matching geometry was employed to generate the signal along a 6.16-mm line directed perpendicular to the beam propagation. With the used imaging optics, in this direction a spatial resolution of 86 mum was achieved. Depending on the set temperature, the agreement between the thermocouple readings and the mean values of the evalutated coherent anti-Stokes Raman-scattering temperatures is better than 40 K. The applicability of this new technique for the time-resolved measurement of temperature gradients is demonstrated along a line that crosses the flame front in a premixed laminar CH(4)-air flame.     

Phase noise performance of microwave analog frequency dividers: application to the characterization of oscillators up to the millimeter-wave range

The phase noise performance of two different microwave analog frequency dividers is characterized and compared with the values obtained using simple theories of noise in injection-locked systems. The direct measurement of the divider noise with a low phase noise synthesizer is not accurate enough, and the residual noise technique is used. The noise levels observed using this technique, between -120 and -155 dBc/Hz at a 10 kHz offset frequency, demonstrate that this divider noise is much lower than the phase noise of most microwave free running oscillators, even if this noise is still high with respect to the residual noise of amplifiers realized with the same active devices. The down conversion of microwave sources up to 40 GHz, is proposed as an application example.     

Spectroscopic Measurement of Air Temperature

Optical dimensional measurements have to be corrected for the refractive index of air. The refractive index is conventionally calculated from parameters of ambient air using either Edlén or Ciddor equations or their modified versions. However, these equations require an accurate knowledge of ambient conditions and especially the temperature of air. For example, to reach an uncertainty of 10^?7 in dimensions, the air temperature has to be known at ~100 mK level. This does not necessarily cause problems in a stable laboratory environment. However, if measurements are done outdoors or in an industrial environment, variations in temperature can be very rapid and local temperature gradients can cause significant error if not taken into account. Moreover, if the required distance is long, the temperature over the whole measurement path can be impractical or impossible to determine at sufficient temporal or spatial resolution by conventional temperature measurement techniques. The developed method based on molecular spectroscopy of oxygen allows both lateral spatial and temporal overlap of the temperature measurement with the actual distance measurement. Temperature measurement using spectroscopy is based on a line intensity ratio measurement of two oxygen absorption lines, previously applied for measurements of high temperatures in flames. The oxygen absorption band at 762 nm is a convenient choice for two-line thermometry since the line strengths are practical for short- and long-distance measurements and suitable distributed feedback lasers are commercially available. Measurements done on a 67 m path at ambient conditions demonstrate that the RMS noise of 22mK, or 7.5 × 10^?5, near 293 K using 60 s measurement time can be achieved, which is to our knowledge the best reported resolution.     

Identification of Wiener-Hammerstein models using linearinterpolation in the frequency domain (LIFRED)

A new method to identify the linear subsystems of a Wiener-Hammerstein model through the measurement of the second-order Volterra kernel is proposed. This technique makes use of the symmetry properties of the Volterra kernel and assumes that the frequency response gain and phase between estimated points can be reasonably well approximated by a straight line. The signal applied for the identification is a multisine with properties of no interharmonic distortion. Several advantages of the proposed method over existing ones are discussed, and two simulation examples are presented to illustrate the applicability of the technique. The method is also shown to be robust to noise and distortion in the input signal     

Insights into linear and rank correlation for material identification in laser-induced breakdown spectroscopy and other spectral techniques

The purpose of this work was to critically assess the potential and limitations of linear and rank correlation methods, not only relevant to laser-induced breakdown spectroscopy (LIBS), but to other spectroscopic techniques as well. Through computer simulations, it was demonstrated that a linear correlation is a more suitable technique for material identification than a rank correlation due to its better stability toward noise and better ability to detect small systematic variations in line intensities. The effect of noise on the results of correlation analysis has been studied. It was found that random noise causes correlation coefficients to be distributed normally, whereas flicker noise (random fluctuations in line intensities) results in a gamma distribution of correlation coefficients. Hence, the distribution of correlation coefficients can be used for detection of the type of noise that dominates correlated spectra. A potential of linear correlation analysis for plasma diagnostics has been demonstrated. It is based on a strong dependence of the linear correlation coefficient upon the line shapes of correlated spectral lines and, consequently, upon plasma parameters (plasma temperature, number densities).     

Estimating thermal contact resistance using sensitivity analysis and regularization

Characterization of the thermal contact resistance is important in modeling of multi-component thermal systems which feature mechanically mated surfaces. Thermal resistance is phenomenologically quite complex and depends on many parameters including surface characteristics of the interfacial region and contact pressure. Although most studies seek a single value as a function of these parameters, in general, the contact resistance is non-uniform over the interface. In this paper, a technique is developed for extracting non-uniform contact resistance values from experiments in two-dimensional configurations. To begin, a two-dimensional model problem is formulated for a known contact resistance between two mated surfaces. An inverse problem is devised to estimate the variation of the contact resistance by using the BEM to determine sensitivity coefficients for specific temperature measurement points in the geometry. Temperature measured at these discrete locations can be processed to yield the contact resistance between the two mating surfaces using a simple matrix inversion technique. The inversion process is sensitive to noise and requires using a regularization technique to obtain physically possible results. The regularization technique is then extended to a genetic algorithm for performing the inverse analysis. Numerical simulations are carried out to demonstrate the approach. Random noise is used to simulate the effect of input uncertainties in measured temperatures at the sensors.     

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。