声表面波器件输入及输出负载阻抗匹配研究

针对声表面波器件测量中网络分析仪的负载阻抗与射频传输线特性阻抗不匹配,导致传输线上反射波幅值较大的问题,提出一种减少传输线上反射波的负载阻抗匹配系统与方案。负载阻抗匹配方案针对声表面波器件测量中输入与输出端分别设计不同的无源负载阻抗匹配网络,使输入输出端同时达到匹配状态。负载阻抗匹配系统集成了未匹配通道与匹配通道,根据负载阻抗不同调整匹配参数。对一个中心频率为101.764MHz,带宽为30MHz的声表面波器件使用该匹配方案前后中心频率处的衰减进行测量对比,实验结果表明采用该匹配方案后在中心频率点处输入及输出反射损耗分别为-49.36dB和-38.13dB,比未采用匹配方案时分别减少了44.99dB和29.44dB。     

Low-cost microwave/millimeter-wave impedance measuring scheme usinga three-probe microstrip circuit

A simple, compact, and low-cost three-probe microstrip impedance measuring scheme has been developed. The impedance of an unknown load can be determined by measuring the coupling power levels at the three probes. The algorithm, formulas, and bandwidth criteria developed are very simple and can be easily used. The power coupling is arbitrary, and no precise directional coupler is required. Using a switch, only one power meter is needed to detect the output power levels of the three probes. The phase information is obtained by amplitude measurement. A detailed analysis and calibration method are developed. The calibration is based on three known standards (a short, an open, and a matched load). The reflection coefficient is calculated from power measurements at three locations along a uniform line terminated by an unknown load. The operating frequency bandwidth depends on the selection of probe locations. A prototype device has been built at X-band     

Measurements of Embedding Impedance of Millimeter-Wave Diode Mounts

A method for measuring the embedding impedanee of diode mounts is presented. The method is based on the measurement of reflection coefficient magnitude only. The reflection coefficient is measured as a function of diode bias (impedance). The embedding impedance can then be obtained in a simple way from the measured data. Results obtained on a coolable 60-90-GHz waveguide mixer are presented and discussed.     

Impedance Transformations For The Generalized Reflection Modulator

A procedure is given for obtaining the impedance transformer which will produce a prescribed pair of phasor reflection coefficients by transformation from a given pair of impedance states terminating the transformer. The transformer may be used in a general two-state reflection modulator: as a phase shifter with phase change at constant amplitude or as an amplitude modulator with level shift at constant or variable phase. The condition governing the reflection coefficients available from a given pair of impedance states is given. Examples and limitations are discussed.     

HP4191A射频阻抗分析仪的测量原理和误差修正原理

HP4191A射频阻抗分析仪的测量原理是测量阻抗的反射系数,他具有自动校准功能,根据3个参考值的校准值自动修正反射系数的误差。首先介绍他的主要性能特点、测量原理、3个参考阻抗件的原理结构和标准值,然后通过公式推导重点介绍他的误差修正方法。     

G.fast数字用户线路阻抗不匹配信道模型研究

基于数字信号传播理论中的反射原理,采用反射系数刻画线路阻抗不匹配程度,利用线路阻抗匹配时测量得到的信道数据（直接信道、远端串扰信道和近端串扰信道）,建立了一个G.fast数字用户线路阻抗不匹配时信道数学模型.当线路终端处于断开时,利用该模型生成的信道数据与实际测量的信道数据基本吻合,证明了该模型的正确性.由于采用反射系数刻画线路阻抗不匹配程度,该信道模型可仿真终端设备在不同阻抗值的情况下对通信系统信噪比的影响,从而提出线路终端设备阻抗最大允许的变化范围,为终端设备制造商在阻抗设计时提供一定的理论指导.     

A Microwave Impedance Meter Capable of High Accuracy (Correspondence)

Recent applications of directional couplers with auxiliary tuners for accurate VSWR and phase shift measurements have made possible a microwave impedance meter capable of high accuracy. It is similar to some bridges in that one obtains an initial detector null and a final null, before and after connecting the unknown. Both the magnitude and phase angle of the reflection coefficient of the unknown are determined in this operation, and these can be made direct reading if desired. The principle of operation is as follows.     

Impedance Matching (Correspondence)

Matching an impedance to a transmission line by the use of a cascaded section of line is a well-known process. However, the range of terminating impedance that can be matched by this method, I believe, is not so well-known. Consider a lossless line of characteristic impedance R/sub0/ to which is to be matched an arbitrary impedance /bar Z/ = R + jX by means of another lossless line of lentgh d and characteristic impedance R/sub 1/ cascaded between the first line and the load as shown schematically in Fig. 1. The problem is to determine for what range of values of /bar Z/ a match can be thus obtained for any values of R/sub 1/, and d.     

低通型阻抗匹配网络的计算机辅助设计

本文在推导阻抗匹配网络输入端反射系数极点解析式和分子多项式的基础上，编写了设计任意偶数阶具有Ｂｕｔｔｅｒｗｏｒｔｈ响应和Ｃｈｅｂｙｓｈｅｖ响应阻抗匹配网络的计算机程序，程序用Ｆｏｒｒａｎ语言编写，当输入匹配网络的阶数ｎ＝２ｍ和阻抗变换比ｒ＝Ｒ２／Ｒ１对Ｃｈｅｂｙｓｈｅｖ响应，通带容许的最大波纹αｄＢ，计算机程序输出匹配带宽和匹配网络归一化元件值。     

A Waveguide Impedance Meter for the Automatic Display of Complex Reflection Coefficient

A waveguide impedance meter has been developed, comprising some specially designed components and some components previously designed for other applications. When this circuit is used in conjunction with the X-band rapid sweep oscillator and suitable display and control circuits, the impedance focus of a waveguide component is automatically and rapidly measured and oscilIographically displayed in the reflection coefficient plane. A waveguide component having a 11/4-inch X 5/8-inch (large X-band) waveguide input port can be continuously measured throughout the frequency range extending from 8.5 to 9.6 kmc (12 per cent X-band). The bandwidth of the system is limited by the design bandwidth of the waveguide components. The plane of the impedance measurement may be referred to a plane internal to or external to the input port of the component under test. An expanded portion of the reflection coefficient plane may be displayed on the crt when small reflections are measured. The measurements of several representative impedances by the waveguide circuit were compared with slotted line measurements of these same components. For measurements of large reflections, standard /spl infin/ db swr full scale display, the maximum observed errors of the magnitude and phase of the reflection coefficient as measured by the waveguide circuit were 10 per cent and 5 degrees respectively. These maximum errors occurred for measurements performed at the ends of the 12 per cent frequency band. The average errors of the magnitude and phase of the reflection coefficient were 2.5 per cent and 2 degrees respectively. For measurements of small reflections, with the crt display of the reflection coefficient plane expanded to 6 db swr full scale, the maximum observed deviation of the waveguide circuit measurements from slotted line measurements was 0.5 db swr, and the average deviation was 0.2 db swr. The maximum errors again occurred at the ends of the 12 per cent frequency band.     

Loop Gain, Input Impedance and Output Impedance of Feedback Amplifiers

Introductory treatments of feedback amplifiers commonly contain inconsistencies, or present results as universal when in fact they need qualification. Loop gain, overall gain, input impedance and output impedance are instances. A case can therefore be made for rigorous development, even in a first course, provided mathematical rigor can be combined with physical insight. A feedback factor H is first defined for ideal circumstances. The corresponding forward-path gain G has an obvious physical interpretation: the amplifier without feedback, the external source and load impedances, and the feedback network are all involved, and the form of G is such as to suggest best practice for the various feedback configurations. Stability considerations, and precise values for overall gain, sensitivity, input impedance and output impedance follow directly from GH.     

Complete calibration of a six-port reflectometer with one slidingload and one short

A novel method is presented for calibrating a six-port reflectometer using only one sliding load of unknown reflection coefficient and one short as a calibration standard. The calibration procedure is derived from the fact that the Fourier coefficients of the periodic port power ratios corresponding to the sliding load positions are closely related to the six-port system parameters. The unknown reflection coefficient of the sliding load as well as the eleven system parameters at each frequency is determined in the procedure. The validity and utility of the proposed method are confirmed by experiments over the frequency range 8.5-12.0 GHz in 0.5 GHz steps with a rectangular waveguide sliding load and a polished metal standard short     

无源UHF RFID标签的低成本阻抗匹配网络设计

提出了一种符合ISO/IEC18000-6C标准的无源RFID(射频识别)标签的低成本阻抗匹配网络。该设计基于复功率波反射系数的概念,修正芯片输入阻抗,在片内添加阻抗匹配电路。通过变化芯片阻抗和天线共轭匹配及失配间切换,有效完成信号的调制反射。提出的电路结构简单,易于实现,在读写器、标签天线和芯片之间实现了功率传输的最大化,提高了芯片输入电压以及读写器对标签反射信号的识别率。采用该阻抗匹配网络的芯片基于chartered 0.35μm CMOS工艺实现。测试结果表明,在923MHz频带下,倍压电路输出可达1.47V,标签满足系统设计要求。     

Calibration of a waveguide sensor for measuring soil moisture

An open-ended waveguide is calibrated for use as a soil moisture sensor. The calibration procedure models the waveguide as a microwave network and uses an optimization procedure to calculate network parameters which minimize errors between measured and calculated response curves. The test load is formed by terminating the waveguide with a two-layered sand profile whose top layer thickness is incrementally adjusted to vary the output load. The output impedance of the waveguide is approximated from intrinsic impedances of the wave propagation through layered media. This approximation produced excellent agreement between reflection responses calculated from the network calibration parameters and those observed for a wide range of output loads     

Normalized Impedance Graphs for Exponential Transmission Lines (Short Papers)

Sign errors in an existing closed form solution for the reflection coefficient along an exponentially tapered transmission line have been corrected and the solution has been modified by the use of electrical line length. This allows useful graphs for the input impedance of the tapered line to be computed which are normalized with respect to frequency and system impedance. The graphs clearly demonstrate both the broad-band and narrow-band properties of the tapered line.     

基于GaN宽带管芯的X波段功放设计

本文在无大信号模型和静态I-V曲线下,应用小信号S参数,power tuned下的负载反射系数和线性模型,得到输出阻抗,应用宽带匹配进行阻抗设计。后加载偏置对S31进行仿真,并观测对S11的影响,从而保证扼流效果并且减小对匹配电路的影响。同时应用小信号S参数和输出阻抗得出输入阻抗,保证增益的平坦性。保证了在8-12GHz下,输出驻波VSWR〈1.4,偏置隔离大于-30dB,小信号增益12.75dB,带内波动0.5dB。     

W-Band Waveguide Impedance Tuner Utilizing Dielectric-Based Backshorts

We present the design, simulations, fabrication, and measurements of a W-band waveguide impedance tuner. The design consists of a WR-10 waveguide with two E-plane arms for tunable dielectric-based backshorts. The impedance tuner is fabricated using a simple split-block technique and is easily scalable to submillimeter wavelengths. Our design shows an excellent input impedance range, tuning accuracy, repeatability, and a high attainable maximum reflection coefficient over the frequency band of 75-110 GHz. Our tuner applies dielectric-based backshorts, which provide a tuning accuracy better than that of other waveguide backshorts.     

Reflection Charts Relating to Impedance Matching

A reflection chart is some grid of coordinates on which to plot an impedance locus over a frequency range. Taking as a reference a constant real impedance, one may construct contours of the reflection coefficient (or the related VSWR, reflection loss, etc.). The reference may be the wave impedance of a transmission line. This may be a line connecting radio equipment with an antenna or it may be a standard line used in measuring the impedance. The reflection chart in widest use is the so-called "Smith Chart" proposed by Philip H. Smith in 1939. It is one form of the hemisphere chart, which was proposed, also in 1939, by Philip S. Carter. Its properties, uses are described. It has some limitations. A reference value must be assigned, after which the shape of a locus depends on this value. Also, a locus is crowded toward the rim of the chart. A logarithmic reflection chart has recently been proposed by the author, which overcomes these limitations but loses some desirable features of the hemisphere chart.     

A new programmable load for noise parameter determination

A new computer-controlled programmable load is presented. The load consists of a cascade of p-i-n diodes bonded to each other. The capacitance of the reverse-biased p-i-n diode, together with the interconnecting bonding wires, forms an artificial transmission line. A complete phase coverage in the Smith chart is obtained by forward biasing any diode pair, using only two current generators and two multiplexers. The amplitude coverage will depend on the diode spacing. The load may be set to any reflection coefficient within its coverage area. Synthesis formulas for the determination of the current driver settings have been derived. A calibration procedure determining the unknown synthesis parameters from input port measurements only is presented. Only the p-i-n diode parameters are characterized separately. The programmable load has been built and tested. Measurements verify the principle and show good agreement with computer simulations. The load has been developed for noise parameter determination. Other applications for variable impedance measurements are circuit or device optimization of gain output power performance