天线卓介质损耗的精确测量

提出了一种测量天线罩介质损耗的方法,对其工作原理、测试程序及测量误差作了论述和分析。本方法适用于高性能天线罩介质损耗的精确测量,可以为天线罩的研制提供有效的判据。应用本方法对某夹层型雷达天线罩的材料和制作工艺进行了优化,实验结果良好。     

Direct G/T Measurement for Satellite Broadcasting Receivers

A new G/T measurement method for receivers which are used for direct broadcasting from a satellite is proposed. By this method, G/T can be obtained without measuring G and T values separately. Therefore, this method, which can be called a direct method, can be adopted for the G/T measurement for integrated antennas, wherein an antenna and a receiver are unseparably combined, while the conventional method can not be adopted nder these circumstances. Besides,-o special test equipment is required for this method. This method can achieve more accurate G/T data because the result is independent from noise bandwidth or signal time response of test equipments. This paper describes the principle of the method, practical test procedure and some notes on how to avoid measurement errors. Some experimental results are also presented, which show that G/T values determined by this method agree with those obtained by the conventional method within 0.4 dB.     

Design of microstrip highpass filters with complementary split ring resonators

An accurate equivalent circuit model and the parameter extraction method are presented for the microstrip line with a complementary split ring resonator. A highpass filter with steep rejection slope is designed based on the model. Numerical simulation and measurement confirms the efficient analysis and design procedure and the validity of the highpass filter configuration     

A correction scheme for measurement accuracy improvement inmultichannel CATV systems

Many commercially-available oscilloscopes offer the FFT-based spectral analysis capability and it is one of the most economical ways to perform spectral measurement. However, the measurement accuracy is always degraded by the incomplete-cycle sampling present in the FFT. Such degradation in the FFT-based measurement of multichannel CATV systems is investigated. It severely degrades the spectral amplitude accuracy as well as the frequency resolution, both of which are important in deriving the system parameters such as the composite-second-order (CSO), composite-triple-beat (CTB), and carrier-to-noise ratio (CNR). The undesirable effect is formulated mathematically for multichannel systems and the result is used to obtain more accurate spectral values. Windowing and a proposed correction method are used to alleviate such detrimental effects, and an improvement of 3-5 dB in the CTB measurement is achieved with the proposed correction scheme. A procedure for achieving better spectrum analysis for multichannel CATV systems is also presented. The analysis and the proposed schemes can improve the accuracy of the FFT-based measurements of multichannel CATV systems than the traditional windowing method     

Self-Consistent GaAs FET Models for Amplifier Design and Device Diagnostics

A procedure has been developed for producing accurate and unique small-signal equivalent circuit models for carrier-mounted GaAs FET's. The procedure utilizes zero drain-source bias S parmeter tests to determine accurate values of carrier parasitics, and dc measurements to evaluate the FET's gate, source, and drain resistances. Subsequent S-parameter measurements at full bias are then used to resolve the FET into an equivalent circuit model that has only 8 unknown elements out of a possible 16. A technique for evaluating the frequency range of accurate data is presented and the FET model shown is useful well above the maximum frequency of measurement. Examples of device diagnostics are presented for RCA flip-chip mounted GaAs FET's.     

Wavelength-dependent differential modal delay in graded-index fibres

We present a technique for measurement of wavelength-dependent differential modal delay in a graded-index fibre. The data are used to derive the excitation-dependent zero-dispersion wavelength. The method offers an accurate calibration procedure to determine the zero-material-dispersion wavelength for given dopant concentration.     

一种基于10项误差模型的二端口矢量网络分析仪校准方法

在三通道二端口矢量网络分析仪(Vector Network Analyzer,VNA)的校准过程中,引入长度未知的50欧姆传输线段作为校准件代替常见的短路-开路-匹配-直通(Short-Open- Load-Thru,SOLT)校准算法中的匹配校准件,减少了校准件数量且不需要已知校准件的全部特性,不仅降低了测试成本,同...     

Refined method for measurement of small-signal alphas of thyristors

The letter presents a refined method for accurate measurement of small-signal current gains (alphas) of thyristors. The measurement circuit developed incorporates an original elimination procedure?with a single tuning for the entire range of measurement frequencies?of the spurious effect of the parasitic gate-anode capacitance Cga.     

Employing a ground model to accurately characterize electronic devices measured with GSG probes

Traditionally, when measuring an electronic device, the nonideal (non-50 /spl Omega/) electrical behavior of the ground-signal-ground probes is removed through calibration. However, this procedure does not allow for an accurate measurement of devices that exhibit an unbalanced flow of electrical currents through the two ground fingers of the probe. We found that a simple interface circuit can be used by a circuit simulator, such as ADS, to reproduce the measurements of devices in which unbalanced ground currents flow in the return paths. A simple experimental method to determine the interface circuit is given.     

Impedance spectroscopy of human erythrocytes: system calibration,and nonlinear modeling

The authors present an impedance measurement method, the cell embedding technique, for human erythrocytes, and an accurate calibration procedure for a four-electrode impedance measurement system that gives reliable results over a wide frequency range-1 Hz to 10 MHz. To achieve high sensitivity, the cells are embedded in the pores of a Nuclepore filter. The calibration procedure assumes that the measurement system is linear and require measurement of three reference impedances. The reliability of the procedure is demonstrated with various RC circuits. Its application to the bio-impedance measurement system eliminates a quasi-dispersion in the high-frequency range and increases the bandwidth at both the low- and high-frequency ends of the range by about a decade. The experimental data are fitted to, an equivalent circuit model of the impedance of the embedded cells. The impedance spectra display constant-phase-angle (CPA) characteristics, which are used to describe the AC response of the interface between the cell surface, and the external electrolyte solution. Such a CPA element may be related to fractal character of the interface     

采用张量分解的四摄像机测量系统标定方法

摄像机标定是精密三维视觉测量的关键,为了实现对多摄像机测量系统的精确标定,首先分析了现有基于一维靶标的多摄像机标定方法的优缺点,并针对其不足,提出了一种基于张量分解的多相机标定方法,该方法主要包括以下三个方面的内容:(1) 利用透视投影成像模型和刚体变换理论建立多摄像机测量的数学模型;(2) 分析现有基于基本矩阵的多摄像机标定方法存在标定结果之间相互耦合的问题;(3) 将四摄像机测量系统的四焦张量引入标定过程中,利用一维标定靶标的成像点坐标求解的四摄像机测量系统的四焦张量,并根据四焦张量的简化求解方法来精炼获取摄像机矩阵。最后,通过实验验证了该方法的有效性和准确性,实验结果表明:(1) 四摄像机三维测量系统的标定可仅通过三组标定靶标图像即可实现,且标定操作效率相对于基本矩阵法更高;(2) 在4000 mm×4000 mm×2000 mm范围内,多摄像机测量系统的精度达到4 mm (3σ),相比于传统方法具有更精确的标定结果。满足室内运动目标位姿精确测量的要求。     

Simple and accurate technique for extracting the parasitic resistances of the dual-gate GaAs MESFET

A procedure to extract the extrinsic resistances of the dual-gate GaAs MESFET (DGFET) is described. Six dc measurement setups are used to generate nine independent relations from which all the unknown extrinsic resistances of the DGFET are extracted. The described technique distinguishes between the forward bias and the nonforward bias values of the channel resistance. The extrinsic resistances of 29 devices with different topologies are determined using the developed technique. The extracted resistances follow normal scaling rules versus gate width. The developed procedure is a practical and accurate approach to extract the extrinsic resistances of the DGFET.     

Measurement of mode splitting in asymmetric Y-junctions

A measurement procedure is presented for the determination of mode splitting (or mode sorting) in asymmetric Y-junctions. This procedure avoids measurement errors introduced by bends, tapers, small damages in the waveguides outside the coupling region, variation in fiber-chip coupling, etc. It is based on the analysis of the normalized coupled power in an optical coupler in which a mode splitter is used. The method is illustrated with a mode splitter on lithium niobate. A value of 29.2±0.5 dB for the suppression of the unwanted mode is found, showing the applicability of the procedure     

An efficient crosstalk parameter extraction method for high-speedinterconnection lines

A proposal is presented for an effective extraction method for crosstalk model parameters of high-speed interconnection lines. In the extraction procedure, mutual capacitance and mutual inductance of the coupled interconnection lines are extracted based on S-parameter measurement, time-domain-reflectometry (TDR) measurement and subsequent microwave network analysis. The extraction method is useful for characterizing homogeneous guiding structures, where the propagation of coupled transverse electromagnetic (TEM) modes is supported. In contrast to previous extraction methods, the suggested procedure requires fewer on-wafer probing steps and does not need matched terminations in the test device for high-frequency probing. The extracted models can be readily used with simulation program with integrated circuit emphasis (SPICE) circuit simulation. The procedure can also be used for modeling the crosstalk in packaging structures and multichip modules (MCMs). The proposed procedure has been successfully applied to the crosstalk model extraction of on-chip interconnection lines. Crosstalk model parameters were obtained for different line structures, spaces, and widths. Finally, the validity and reliability of the extracted models were examined by comparing a SPICE circuit simulation using the extracted crosstalk model parameters with high-speed time-domain crosstalk measurement. A close agreement was observed in the amplitude and pulse shape between the simulation and the measurement, showing the accuracy and usefulness of the proposed extraction method     

基于SOPC的集成化指纹处理实验研究

指纹技术作为一种安全、有效的身份识别方式,目前受到广泛关注.本文针对指纹识别的快速实现和集成化实验问题,基于SOPC技术设计了一类指纹采集、处理系统的FPGA原型.系统配备了NiosII软核及相关功能组件,并外扩指纹传感器模块.同时,本文还研究了适合于SOPC系统的指纹图像采集方式和预处理方案,完成了指纹图像的方向图计...     

基于测量子集优化的雷达/ESM联合目标跟踪

针对雷达电子支援措施(ESM)主被动传感器的协同定位与目标跟踪,提出了基于测量子集优选的目标跟踪算法。该方法利用ESM方位角测量与雷达距离、方位测量组成的各测量子集对目标的定位精度分析,遴选出定位精度最高的测量子集定位结果作为雷达对目标跟踪的融合量测,在雷达的跟踪门内进行量测确认,之后按照联合数据互联的方法,对多目标当前状态进行估计。仿真实验显示,该方法是异地配置雷达/ESM协同目标跟踪的一种点迹级融合的有效方法。     

大动态范围激光散斑位移测量研究

通过对散斑特性的研究与分析,提出了一种快速、准确的散斑相关搜寻法。同时还提出一种“逐步更新”的测量方法,它克服了由于大的位移而导致相关系数偏低的缺点。实验证明,这咱测量方法是一种快速、准确的大范围面位移测量方法。     

Dielectric constant measurements of finite-size sheet at microwavefrequencies by pseudo-Brewster's angle method

Dielectric constant (ϵ_r) measurements for finite-size dielectric sheets (DS's) at centimeter wavelengths are presented using the method-of-measuring pseudo-Brewster's angle. This method is applied to measure ϵ_r of sheets of Plexiglas and window glass. In the experiment, two horn antennas are used to transmit and receive p-polarized waves. A dielectric sheet is located between the two antennas and rotated 180°, which produces two peaks in the transmittance curves. For a more accurate measurement of Brewster's angle, an optical spectrometer with 1-min accuracy is also used. By this method, ϵ_r of Plexiglas and window glass are obtained to be 2.55±0.13 and 5.35±0.1, respectively. This method measures |ϵ_r|, but the measurement is easy and nondestructive for DS's. Finally, an accurate method of error calculation is used to calculate the error in the measured values of ϵ_r     

A new method to electrically determine effective MOSFET channel width

A new, easy, and accurate electrical measurement method for determining process bias of MOSFET channel width is proposed. This method is based on the linear relationship between the effective width and the channel conductance (or drain current) of a MOSFET operating in the linear region. Constant and sufficiently high gate voltages compared with the threshold voltage of the device are used in the measurement to minimize the error due to the threshold-voltage variation with W in narrow-width devices. The validity of the method is supported by identical results obtained using different gate voltages.     

S-parameters characterization of through, blind, and buried via holes

A method for de-embedding the scattering parameters matrix for single-end or differential through, buried, and blind via holes in multilayer printed circuit boards for high-speed digital applications is presented. The proposed technique starts from a measurement or simulation of the structure containing the discontinuity and, after the structure's partitioning, extracts the scattering parameters of the required discontinuity. The procedure is applied to different kinds of single-ended and differential via holes and is validated by measurements. The finite integration technique is used to perform the needed three-dimensional electromagnetic simulations. Due to its reduced CPU time, the proposed methodology is suitable for a parametric analysis on the electrical performance of the via hole discontinuities and it gives useful results for the extraction of accurate computer-aided design models.