基于多输入阻抗的电源分配网络研究

通过多输入阻抗准确描述当代高速平面电源分配网络(PDN).该阻抗能够同时探查多个激励源输入及准确估量其他端口对PDN的影响.多输入阻抗是一种新颖的输入阻抗,它有两种表现形式:多输入自阻抗和多输入叠加阻抗.前者用于描述同一IC内各个电源端口之间的影响,后者用于描述不同IC之间的影响.经时频域仿真,该多输入阻抗能同时精确地...     

Input impedance analysis of single-phase PFC converters

The input impedance of single-phase boost power factor corrected (PFC) AC-DC converters is modeled and analyzed in this paper. A large-signal model is presented for the input impedance which overcomes the limitations of traditional piece-wise linearized models. The model is valid at frequencies ranging from the crossover frequency of the output voltage loop to half the switching frequency of the converter. Experimental results from a boost single-phase PFC converter are provided to validate the model. Input characteristics of typical boost PFC converters, such as input impedance dipping, leading phase of the input current, and responses to distorted input voltages are studied by using the model. A simple compensation technique to reduce the dipping in the input impedance, thereby improving converter performance and minimizing the potential for undesirable interactions with the input filter or the ac source, is also presented.     

空载变压器音频特性研究

研究了配电网中常用的降压变压器（６ｋＶ／３８０Ｖ）在音频激励信号频率下原端的阻抗特性,结论是：在音频激励信号范围内,变压器副边开路时,空载阻抗为容性;副边短路时,空载阻抗为感性;当频率确定时,随着变压器容量的增加,变压器空载阻抗下降;同一容量的变压器,随着频率的下降,空载容抗增加;副边接补偿电容时,空载阻抗为感性。     

Calculation of the input impedance of a strip loop antenna located on a dielectric cylinder

A method for calculating the input impedance of a loop antenna (LA) located on a dielectric cylinder is developed. The integral equation (IE) for the unknown function of the current density distribution on the LA surface is obtained. A numerical method for the IE solution is described. An approximate formula for calculation of the LA input impedance is proposed. Plots of the input impedance on the LA length are given.     

折叠偶极子天线的设计

射频识别(RFID)应用中的天线设计需考虑的最重要因素是低价位、小剖面和小型化,而为了最大功率传输,天线的输出阻抗必须和其后的芯片的输入阻抗匹配。本文介绍一种新颖的简单结构折叠偶极子天线,所需的输入阻抗能通过选择合适的几何参数轻易获得,这对设计特殊阻抗的天线非常有用。     

中波天线输入阻抗计算机分析

通过对76m天线、138m天线输入阻抗数据分析，对天线输入阻抗与平均特性阻抗、波长缩短系数以及天线等效直径的关系进行了探讨，分析了对用传输线法计算天线输入电抗误差较大的原因，并对输入电抗的计算提出了修正。     

Measurement of impedance transformation on practical dipoles

The measured input impedance of a practical dipole antenna is shown to be related to the theoretical input impedance of a delta-gap cylindrical dipole through a bilinear transformation. In order to determine the three complex constants which specify the transformation, the impedance of a dipole in front of a ground plane is measured and compared with the theoretical impedance. The comparison is performed by a curve-fitting procedure for bilinear transformation on a complex plane. The same measurement yields also the receiving efficiency of the antenna and its feeding network. Experiments show that the input impedance of a practical folded dipole, incorporating a balun transformer, may be predicted with an accuracy of better than four percent.     

Ground influence on the input impedance of transient dipole and bow-tie antennas

In this paper, the influence of a lossy ground on the input impedance of dipole and bow-tie antennas excited by a short pulse is investigated. It is shown that the ground influence on the input impedance of transient dipole and bow-tie antennas is significant only for elevations smaller than 1/5 of the wavelength that corresponds to the central frequency of the exciting pulse. Furthermore, a principal difference between the input impedance due to traveling-wave and standing-wave current distributions is pointed out.     

A method of moments analysis and a finite-difference time-domainanalysis of a probe-sleeve fed rectangular waveguide cavity

A multifilament method of moments (MOM) analysis and a finite-difference time-domain (FE-TD) analysis are used to numerically calculate the input impedance of a probe-sleeve fed rectangular waveguide which has been short-circuited on one side. The input impedance of the system is determined by using the above methods for several probe-sleeve configurations, and reasonable agreement between the two methods for the cases studied is found. An MOM Green's function formulation which is based on scattering superposition and which allows the input impedance of a probe-sleeve feed to be calculated when the waveguide is terminated in a given load is derived. The MOM results and FD-TD numerical results are compared for this loaded waveguide input impedance case, and reasonable agreement between the methods is found. A comparison of theory and experiment is given for when the waveguide is terminated in a ground plane aperture     

Input filter design for multiple-module DC power systems

When multiple DC/DC power converters are operated from a DC bus with a nonzero source impedance, undesirable interactions can occur between an individual regulator and the input impedance of the other regulators on the bus. Consequently, criteria for input filter design in the presence of a significant source impedance are developed, which, when used in conjunction with already-known input filter criteria, permit the input filter to be designed so that each regulator operates reliably. Proper filter design tends to decouple the negative regulator impedances from the bus, leaving only the passive input filter impedances to affect the other converters. These filter impedances appear in parallel with the source impedance and reduce the overall source impedance. Hence, the use of multiple modules on the same bus actually improves the performance of the individual regulators. An example, the buck current mode controlled power converter, is examined in detail. Extensive experimental evidence is presented to verify the analytical results     

多层PCB 电源地平面返回路径阻抗的边界元分析

研究了多层印制电路板(PCB)中含有一个信号过孔的电源/地平面返回路径阻抗的频域特性,并分析采用添加短路过孔的方法减小多层PCB的输入阻抗.电源/地平面形成了径向传输线结构,反焊盘处的输入阻抗即为信号电流在电源/地平面间的返回路径阻抗.在电源/地平面外部边界施加PMC(完全导磁体)边界条件,在反焊盘处施加电流激励源,短路过孔轴向电场为零,采用高效的二维边界元法求解.计算了10GHz内电源/地平面返回路径的输入阻抗.结果表明:在两特性相同的平面之间添加短路孔可以降低输入阻抗,同时,电源、地平面的输入阻抗随频率变化交替呈现容性或感性,在反谐振频率处输入阻抗值可达几百欧姆,此外,在频率较低时输入阻抗可用静态电容或静态电感表示.采用基于全波分析的有限元软件验证了计算结果和计算方法的正确性.     

扫频仪测圆环天线输入阻抗值的可行性研究

用扫频仪测量天线的输入阻抗时，在同轴传输线与天线间应按平衡—不平衡变换器。针对圆环天线的输入阻抗为复阻抗，提出了一种新的四分之一波长平衡一不平衡变换器，得到了实验结果，并进行了讨论。     

Differential amplifier input impedance

The analysis of a simple differential amplifier excited by two separate voltage sources reveals that the input impedance which loads the voltage source at the inverting input is not a constant but rather is a function of the characteristics of each voltage source. An expression is derived for the input impedance and the result is illustrated in a simple example.     

用于金属表面的UHF RFID标签天线优化设计

UHF RFID 标签天线置于金属表面会引起阻抗变化以及阻抗失配,因此为了减小金属表面的影响,提出一种用于金属表面的UHF RFID 标签天线阻抗匹配优化设计方法。首先在折叠偶极子天线臂上附加短路段来调整标签天线的输入阻抗,通过粗略调节短路段的位置使天线和RFID 标签芯片在金属表面达到阻抗的基本匹配,然后利用遗传算法优化得到天线最优的长度、宽度和短路段位置,使天线和RFID 标签芯片在金属表面达到准确的阻抗匹配。所设计天线阻抗及方向图的仿真和测试结果表明该优化设计方法能够使RFID 标签天线在金属表面正常工作。     

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。     

Effect of gate poly-silicon depletion on MOSFET input impedance

One of the most challenging problems encountered in developing RF circuits is accurate prediction of MOS behavior at microwave signal and data frequencies. An attempt is made in this work to accurately model the device input impedance for the 1-20-GHz frequency range. The effect of device length and single-leg width on the input impedance is studied with the aid of extensive measured data obtained from devices built in 0.11-/spl mu/m and 0.18-/spl mu/m technologies. The measured data illustrates that the device input impedance has a nonlinear frequency dependency. It is also shown that this variation in input impedance is a result of gate poly-silicon depletion, which can be modeled by an external RC network connected at the gate of the device. Excellent agreement between the simulation results and the measured data validates the model in the device active region.     

一款JFET低噪声前置放大器的设计

在对级联网络及结型场效应管的噪声分析基础上,采用结型场效应管等分立元件设计了一款低噪声前置放大器实用电路。并对其幅频特性、输入阻抗和等效输入噪声进行了测量,结果表明其输入阻抗高达71Mn。等效输入噪声电压为0．7nV／√Hz,是一种适合于较高内阻传感器的较理想的低噪声前置放大器电路。     

Input impedance, radiation pattern, and radar cross section ofspiral antennas using FDTD

A finite-difference time-domain (FDTD) analysis of spiral antennas is performed to calculate input impedance, antenna gain, and scattering. A semicircular spiral mounted on a dielectric substrate was simulated for computing the input impedance versus frequency. The gain and scattering computations were performed on a square Archimedean spiral mounted in a ground plane with a cavity backing. Total-field FDTD calculations are used to compute the impedance and gain patterns, while a specially modified scattered-field approach for aperture antennas in infinite ground planes is used for the scattering results. Comparisons are made with published impedance measurements and gain and scattering calculations done with a finite element method. Good results were obtained for impedance, radiation, and scattering     

Nominal resistance of a complex impedance

The theoretical relationships between broadband electrical input impedance and maximum instantaneous input current are given for classes of input voltage signals with or without bandwidth limitations. A nominal resistance associated with a complex impedance is defined, and this quantity can be used in circuit analysis or design to predict maximum possible transient current. Results from several experimental measurements are presented.     

The development of a closed-form expression for the input impedance of power-return plane structures

In multilayer printed circuit boards, the noise on the power bus is influenced by the impedance between the power and ground planes. Power-bus noise estimates require an accurate estimate of the power-bus input impedance. This paper develops a closed-form estimate of the input impedance for circular power-return plane structures. When the structure is lossy (e.g., boards employing embedded capacitance or densely populated boards), the energy reflected from the board edge does not significantly affect the input impedance. In general, the expressions developed here for circular structures can be used to estimate the impedance of lossy power-return plane structures of any shape.