Self-capacitance of inductors

A new method for predicting the stray capacitance of inductors is presented. The method is based on an analytical approach and the physical structure of inductors. The inductor winding is partitioned into basic cells-many of which are identical. An expression for the equivalent capacitance of the basic cell is derived. Using this expression, the stray capacitance is found for both single- and multiple-layer coils, including the presence of the core. The method was tested with experimental measurements. The accuracy of the results is good. The derived expressions are useful for designing inductors and can be used for simulation purposes     

HF Characterization and Nonlinear Modeling of a Gapped Toroidal Magnetic Structure

The frequency dependent characteristics of a gapped toroidal structure are extracted empirically over a bandwidth that exceeds 30MHz. The analysis is complicated due to nonlinear flux distributions, magnetic properties of the core material, leakage inductance, stray capacitances, and eddy currents in the windings. A permeance model of the core is implemented to model the magnetic circuit. The model includes a linear lumped element equivalent circuit to approximate the nonlinear complex permeability of the core, which was measured empirically. Stray capacitance and inductance of the winding are also modeled. A gyrator is used to couple the electric and magnetic models for circuit simulation. The measured and simulated results of open-circuit impedance from the secondary winding and the transimpedance gain (V/A) of the current sensor are compared and discussed.     

飞机直流母线变换器的输入电磁干扰滤波器设计

针对飞机直流270 V至直流28 V电源变换器的应用需求,分析了电源变换器输入端的传导及辐射电磁干扰源.通过对电源变换器的电磁干扰（electromagnetic interference,EMI）频谱进行分析,确定了滤波器的参数.为了抑制滤波器振荡,提出在差模电感两端并联电阻电感网络的方法,替代使用液态铝电容的传统方法,提升滤波器的可靠性.根据差模电感中电流直流分量远高于交流分量的特点,提出采用扁铜漆包线来实现绕组的方法,使差模电感的体积降低.根据锰锌铁氧体低频磁导率高,镍锌铁氧体高频磁导率稳定的特点,提出双磁芯共模电感的设计方法,实现共模电感宽频率和小体积.实测结果证明输入电磁干扰滤波器可使电源变换器符合GJB 151中CE102要求.     

叠层片式陶瓷电感器寄生电容的提取

寄生电容是叠层片式电感器的重要参数,对电感器的Q值和谐振频率影响很大.如何准确估计寄生电容的大小成为电感器设计的一个难题.采用Ansoft Q3D软件建立了叠层片式陶瓷电感器的3D静电场有限元模型,计算了各电极间的杂散电容,然后建立电感器的等效电容网络,列出节点电压方程并求解得到寄生电容.计算结果和测量结果基本一致.瓷...     

Improving the Characteristics of integrated EMI filters by embedded conductive Layers

Discrete electromagnetic interference (EMI) filters have been used for power electronics converters to attenuate switching noise and meet EMI standards for many years. Because of the unavoidable structural parasitic parameters of the discrete filter components, such as equivalent parallel capacitance (EPC) of inductors and equivalent series inductance (ESL) of capacitors, the effective frequency range of the discrete filter is normally limited. Aiming at improving high frequency performance and reducing size and profile, the integrated EMI filter structure has been proposed based on advanced integration and packaging technologies , . Some improvements have been made but further progress is limited by EPCs of the filter inductors, which is restricted by dimension, size and physical structure. In this paper, a new structural winding capacitance cancellation method for inductors is proposed. Other than trying to reduce EPCs, a conductive ground layer is embedded in the planar inductor windings and the structural capacitance between the inductor winding and this embedded layer is utilized to cancel the parasitic winding capacitance. In order to obtain the best cancellation effect, the structural winding capacitance model of the planar spiral winding structure is given and the equivalent circuit is derived. The design methodology of the layout and area of the embedded ground layer is presented. Applying this method, an improved integrated EMI filter is designed and constructed. The experimental results show that the embedded conductive layer can effectively cancel the parasitic winding capacitance, hence ideal inductor characteristics can be obtained. With the help of this embedded conductive layer, the improved EMI filter has much smaller volume and profile and much better characteristics over a wide frequency range, compared to the former integrated EMI filter and the discrete EMI filter.     

20 GHz bandwidth low-noise HEMT preamplifier for optical receivers

A broadband, low-noise HEMT preamplifier is designed for very high-speed fibre-optic transmission systems. A 20 GHz 3 dB down bandwidth and 7.6 pA/√(Hz) averaged input equivalent noise current density from 100 MHz to 18 GHz are achieved using inductor peaking techniques and low stray capacitance chip resistors     

Transients in high-power modulators

The physical size involved in the design and construction of high-power modulators introduces high inductance and stray capacitance in the circuit. Analysis shows that under normal operation any inductance between the energy source and the RF device, together with stray capacitance, produces damped oscillations after the "turn-on" and "turn-off" of the RF generator beam. Unfortunately, the need for adequate protection of the RF generator and modulator requires the introduction of an additional inductor in the circuit to limit the rate of rise of fault current. Improper placement of this inductor can also produce detrimental oscillations under fault conditions. Proper design can minimize these unwanted transients. An analysis of the circuit and the results obtained in a high-power modulator are discussed.     

光学系统杂散光分析

杂散光是光学系统中所有非正常传输光的总称,杂散光对光学系统性能的影响因系统不同而变化。因此,在现代光学设计中,杂散光分析成为光学设计工作中的一个重要环节。杂散光产生的原因比较复杂,讨论了漏光和透射面残余反射引起的杂散光,针对漏光杂散光给出了高密度取样的分析方法,对于残余反射的杂散光建立了带能量因子的光线光学模型和光线二叉树的数据结构,在保证计算精度的同时减少了计算时间。对一个卡塞格林光学系统进行了漏光杂散光分析和光学表面残余反射杂散光的近轴与实际光线分析,得到减少杂散光的措施,达到了杂散光分析的目的。     

Exact solution for capacitive compensation of the RC potential divider with lumped stray capacitances to earth

Serious shortcomings of RC wideband dividers for high voltages can be overcome by suitably graded compensation of stray capacitance. The general case of the lumped-circuit-element RC divider is analysed, and the exact solution for graded capacitive compensation for any distribution of lumped stray capacitance is given.     

星敏感器遮光罩的设计与杂散光分析

杂散光抑制是提高星敏感器精度的重要手段,遮光罩的设计是抑制杂散光的主要途径.对星敏感器遮光罩进行设计,通过SolidWorks软件建模,绘制出遮光罩结构,将得到的结构导入TracePro软件中进行杂散光分析.设定材料表面的双向散射分布函数与光线追迹数目,在不同方位角度对1°～75°之间共16个离轴角度进行了光线追迹,得到系统的PST曲线.结果表明,和改进前的结构相比,PST值降低了一个数量级,且系统的杂散光抑制能力在离轴角30°时达到10-9量级.遮光罩内设计竖直挡光环结构有很好的杂散光抑制作用,使系统杂散光抑制水平得到较大的提高.     

考虑衬底涡旋电流的CMOS射频电路电感元件的快速提取算法及实现

本文描述了一个采用复镜像方法来解析计算CMOS射频电路中衬底涡旋电流对螺旋电感元件的影响.其基本思路是将衬底里分布着的涡旋电流等效为电感金属绕组的一个镜像,但是这个镜像所处的位置是一个复数.通过把计算出的部分电感和部分电容矩阵组装成一个PEEC(部分元件等效电路)的办法,能够进一步算出螺旋电感的交流小信号参数.基于该算法实现的程序(称为SCAPE)的正确性已经通过大量的例子测试,并跟一些广泛使用的软件(如UC Berkeley的ASITIC和Agilent的ADS Momentum)进行了比较,结果证明了SCAPE具有精度高、运算速度快的优势.     

CMOS RFIC平面螺旋电感的集总等效电路

基于DDM-CM理论,建立了CMOS工艺下射频集成电路中广泛使用的平面螺旋电感器的π型集总等效电路.获得了Si-SiO2结构衬底上解析、封闭的集总参数的表达式,并和已经发表了的实验数据进行了比较,验证了所得结果的准确性.     

Correction of stray light and filter scratch blurring for ASTER imagery

Stray light components in images obtained by the shortwave infrared (SWIR) and visible near-infrared (VNIR) radiometers of the Advanced Spaceborne Thermal Emission Reflection Radiometer (ASTER) were investigated. A simple method, which is equivalent to the van Cittert method of deconvolution, was used for correction. The stray light components were estimated using the image obtained during lunar observation, and the improvement in image quality was examined after stray light correction. The calculation is performed in the space domain, and application to the filter scratch problem of the ASTER/SWIR sensor, which has a scratch on the interference filter resulting in partially degenerated images, is also demonstrated.     

Equivalent Circuit Analysis of an RF Integrated Inductor with Ferrite Thin-Film

针对已制作并发表的一种新型铁氧体磁膜结构射频集成微电感进行了等效电路分析.阐述了磁性铁氧体薄膜对电感的感值(L)和品质因数(Q)的增强作用.对射频测试结果进行了电路元件参数提取.结果表明,与空气芯无磁膜微电感相比,磁膜结构微电感的L和Q在2GHz处分别提高了17%和40%.等效电路分析和测试结果均证明了铁氧体薄膜的引入对增强射频集成微电感性能的作用显著.     

FDTD modeling of lumped ferrites

Implementing ferrites in finite-difference time-domain (FDTD) modeling requires special care because of the complex nature of the ferrite impedance. Considerable computational resources and time are required to directly implement a ferrite in the FDTD method. Fitting the ferrite impedance to an exponential series with the generalized-pencil-of-function (GPOF) method and using recursive convolution is an approach that minimizes the additional computational burden. An FDTD algorithm for a lumped ferrite using GPOF and recursive convolution is presented herein. Two different ferrite impedances in a test enclosure were studied experimentally to demonstrate the FDTD modeling approach. The agreement is generally good     

铁氧体磁膜RF集成微电感等效电路分析

针对已制作并发表的一种新型铁氧体磁膜结构射频集成微电感进行了等效电路分析.阐述了磁性铁氧体薄膜对电感的感值(L)和品质因数(Q)的增强作用.对射频测试结果进行了电路元件参数提取.结果表明,与空气芯无磁膜微电感相比,磁膜结构微电感的L和Q在2GHz处分别提高了17%和40%.等效电路分析和测试结果均证明了铁氧体薄膜的引入对增强射频集成微电感性能的作用显著.     

Wire antennas in the presence of a dielectric/ferrite inhomogeneity

A moment method solution for treating thin-wire antennas in the presence of an arbitrary dielectric and/or ferrite inhomogeneity is presented. The wire is modeled by an equivalent surface current density, and the dielectric/ferrite inhomogeneity is modeled by equivalent volume polarization currents. The conduction currents on the wire and the polarization currents in the dielectric/ferrite inhomogeneity are treated as independent unknowns and determined in the moment method solution. The method is applied to the problem of a loop antenna loaded with dielectric or ferrite. Numerical results are presented, and are in good agreement with measurements and previous calculations.     

Experimental determination of stray capacitances in high frequency transformers

This paper presents practical techniques for determining stray capacitances in a two-winding high frequency transformer for circuit simulation and computer-aided design purposes. These techniques fall into two categories: The two-port network approach; and the step-response approach. The first approach can be employed for high frequency transformer circuit models with the effect of stray capacitances modeled as a /spl pi/-shape network of three lumped stray capacitances. The second approach is useful for the transformer circuit model with the overall effects of stray capacitances modeled as lumped stray-capacitance connected cross the primary side. These techniques have been verified in the modeling and numerical simulation of a 500 W 25 kHz two winding E-core transformer. The merits and limitations of these techniques are also discussed.     

Determination of capacitances and inductances of the uniformcoupled lines in the anisotropic inhomogeneous medium by resistive sheet

Many filters, power dividers and nonreciprocal circuits such as a lumped element circulators used for broadcasting, communications and CATV, are using parallel coupled lines together with the high dielectric constant ceramics and ferrite. It is important to design such a devices, that the capacitance and inductance per unit length of the multi-distributed lines are determined by simple methods. This paper shows a simple method of determining the values of the multi-lines in an anisotropic medium by using the two dimensional resistive sheet or equivalent computer method. The values are used for obtaining the effective dielectric constant and the effective permeability which are required for the estimation of the quasi-TEM mode in the case of a small sectional dimension compared with the wavelength. The method used to obtain the inductance is based on the Babinet' principle     

弱小目标红外探测系统的杂散辐射分析

杂散辐射是指到达红外探测系统靶面的非目标成像的辐射能量。杂散辐射经过光电器件后增加了系统的噪声,降低了系统的输出信噪比,影响到红外探测系统对目标的探测能力。为了提高红外探测系统对空间弱小目标的探测能力,分析了红外探测系统的杂散辐射来源;推导了不同地理纬度、不同时刻下的红外探测系统太阳辐射入射角计算公式;分别计算了红外探测系统的太阳辐射、天空背景、热辐射噪声等效电子数;比较了杂散辐射噪声和探测器的固有噪声,分析了红外探测系统的最小噪声极限,得出地基红外探测系统的背景噪声决定了系统的探测极限。