A reflection coefficient derivation for the Q of a reverberationchamber

Reverberation chambers (also called mode-stirred chambers) are multimoded cavities that are used for radiated emissions or immunity measurements. A reflection coefficient method is used to derive the quality factor (Q) of reverberation chambers of arbitrary shape. The results are applicable to walls of general materials, but reduce to the previous result for highly conducting walls with small skin depth. The reflection coefficient method is also used to derive the decay time of reverberation chambers     

基于互耦效应的相控阵天线有源反射系数研究

建立逼真高效的互耦效应分析模型对相控阵天线设计至关重要。阵列天线的互耦效应通常可以用有源反射系数显性化表征,分别采用无限阵仿真与散射(耦合)系数综合实验相结合的方法提取了阵列天线的有源反射系数。首先基于无限阵方法设计相控阵渐变开槽天线,优化并获取无限阵列环境下的中心单元有源反射系数,再依据设计结果研制169单元阵列天线,通过实验测试提取中心单元与其它各激励单元的散射系数的幅值与相位变化,最后采用散射(耦合)系数法综合出有限大阵列的有源反射系数。无限阵仿真结果与有限阵实测结果在扫描盲点出现角度、频段、有源驻波整体趋势等方面吻合良好,从而验证了无限阵设计方法在天线工程设计中的实际效果。     

Reflection from the aperture of a longE-plane sectoral horn

The complex reflection coefficient of a longE-plane sectoral horn is derived using the geometrical theory of diffraction. Single diffraction alone is shown to be sufficient to describe the contribution from theE(widely separated) edges, while singly and doubly diffracted fields from theHedges are included by using an open waveguide result derived elsewhere. A relatively uncomplicated expression is obtained for the complex reflection coefficient of the horn which agrees well with experiment for horns with slant wall lengths greater than about3frac{1}{2}guide wavelengths.     

Reflection coefficient (Schur parameter) representation for convex compact sets in the plane

We obtain a one-to-one relation between the shape and orientation of a convex compact planar set and a complex-valued reflection coefficient (Schur (1917) parameter) sequence, such that (1) the reflection coefficient magnitudes are less than or equal to one, (2) if any reflection coefficient has a magnitude equal to one, then all subsequent reflection coefficients are equal to zero, and (3) the first reflection coefficient is equal to zero. Three additional independent parameters specify the position of the set in the plane, and the size of the set (specifically its circumference). For a finite duration reflection coefficient sequence, if the last nonzero reflection coefficient has a magnitude that is less than one, then the boundary of the set is an infinitely differentiable convex curve. The boundary is a convex polygon if and only if the magnitude of the last reflection coefficient is equal to one; the number of sides of the polygon is equal to the index of the last reflection coefficient. Almost all planar convex compact sets have reflection coefficient sequences of infinite duration. Such sets can be accurately approximated with convex compact sets that are generated from relatively small numbers of reflection coefficients.     

测试连接器互调的新方法

在微波无源网络中,同轴连接器是无源互调产生的主要原因,因此准确确定同轴连接器的无源互调值对于整个无源系统设计来说有至关重要的意义。大多数厂家采用的测试方法中,测量连接器的互调不仅要制作工装,而且还要对连接器做破坏性实验。同时,由于增加了新的接触面,这种测试方法本身又会引入新的互调。基于此种情况,提出一种新的测试连接器互调方法——开路测试法。首先建立连接器的基本模型,然后利用矢量网络分析仪测量连接器模型在开路和匹配两种情况下的负载反射系数和源反射系数随频率的关系,最后根据测量出的反射系数通过连接器模型算出微波无源网络中同轴连接器的互调。利用互调分析仪实测连接器的互调值,测试结果和计算结果吻合,验证了这一方法的有效性。     

Reflection of the transitional electromagnetic wave by inhomogeneous ionized media having a peak of electron density

The reflection coefficient of an inhomogeneous ionized medium having a peak in electron density is analysed. The result shows the existence of peak influences for the phase term of non-peak linearly varying electron density in the medium. The characteristic of the reflection coefficient phase delay versus frequency is related to the electron density at a peak point and the position of the electron peak. Using this theory we can obtain the electron density distribution map in the inhomogeneous ionized medium. To verify the theory the reflection coefficient is compared with the results from the finite difference time domain method; both results give a good agreement.     

包层泵浦光纤激光器长度优化设计的研究

文章基于三能级系统光纤激光器的速率方程模型,重点分析了输入端反射系数R1、输出端反射系数R2以及泵浦功率这3个因素对包层光纤激光器最佳光纤长度L优化的影响.并用数值仿真进行了研究,得到了有意义的结果,对包层泵浦光纤激光器的研究具有重要意义.     

Zero reflection coefficient in discretized PML

In this paper we present a closed-form reflection coefficient for the perfectly matched layer (PML), when realized using the finite-difference time-domain (FDTD) algorithm. Examining the reflection coefficient, it is found that zero reflection can be obtained for isolated pairs of frequency and angle of incidence     

Discussion on Optimum Bead Spacing (Correspondence and Author's Reply)

Mr. Dettinger's article on the optimum spacing of bead supports in coaxial transmission lines is too sanguine as to the performance which will result. He states that an array of M beads arranged according to his theory will result in a total reflection coefficient of no more than /spl radic/M Gamma/sub 0/ where Gamma/sub 0/ is the reflection of one bead. In his Fig. 5 he shows a chart of the reflection of four beads equally spaced and the reduced reflection which he hopes will result from application of his rule. The case where there are four beads will result for equal spacing in a maximum value of 4Gamma/sub 0/, and from his theory for progressive spacing it should be possible to arrange the beads so that the maximum possible reflection is only 2Gamma/sub 0/.     

双耦合线巴伦设计

基于微带耦合线的四端口网络模型,提出了一种双耦合线巴伦,根据最小反射系数准则,推导出巴伦应满足的阻抗方程,并给出不同带宽所要求的耦合线奇偶模阻抗.最后给出ADS仿真结果及实验结果.     

The small slope approximation reflection coefficient for scatteringfrom a “Pierson-Moskowitz” sea surface

First- and second-order reflection coefficients are presented for the small slope approximation. The first-order reflection coefficient is identical to the Kirchhoff, or physical optics, result, and the second-order reflection coefficient reduces to those of perturbation theory and the Kirchhoff approximation in the appropriate limits. Numerical results are obtained for acoustic or TE-polarized electromagnetic scattering from one-dimensional, “Pierson-Moskowitz” sea surfaces at low grazing angles. Comparison with exact integral equation results shows that the second-order small slope approximation is extremely accurate and better than both the perturbation and Kirchhoff methods     

The Improvement of PML Approach for the Calculation of Microwave and Millimeter Waves Circuit

The improved PML absorbing boundary condition have been introduced in this paper. The reflection coefficient of the absorbing boundary condition is less than the reflection coefficient of Berenger's PML algorithm. And in order to validate the theory and its effectiveness, We have applied the absorbing boundary condition to the calculation of microwave and millimeter waves circuit and get its reflection coefficient S ₁₁. The numerical result is shown in this paper.     

Inverse scattering method for one-dimensional inhomogeneous layered media

An inverse scattering method to reconstruct simultaneously the permittivity profile and the conductivity profile of one-dimensional inhomogeneons medium which makes use of the transverse electric (TE) wave and/or transverse magnetic (TM) wave, is proposed. The medium is illuminated by the TE and/or TM plane wave at oblique incidence, and the data are taken as the reflection coefficients for a set of discrete frequencies and/or a finite number of incident angles. Furthermore, the reflection coefficient data contain the Gaussian noise. The nonlinear integral equation relating the unknown constitutive parameter of the medium to the reflection coefficient for TE wave and/or TM wave is solved by the Newton iteration method. The inverse operator in the Newton method is determined by the regularization method. It is demonstrated in terms of the numerical examples that this method utilizing both polarizations and the incident angle of the incident plane wave is very effective even if the reflection coefficient contains the practical measurement error, or the phase of the reflection coefficient is unknown. Moreover, the relationships between the errors of reconstructed profile and the measured reflection coefficient are also discussed.     

Novel type of fibre-optic ring resonator

A fibre-optic ring resonator with highly wavelength-selective input reflection coefficient was realised by introducing a small local reflection in the ring. The influence of the local reflectivity on the input reflection coefficient is demonstrated. Maximum values for the input reflectivity and finesse are 55% and 10, respectively, using a fibre directional coupler (FDC) with a coupling ratio of 30%/70%.     

Band-Limited Deconvolution of Locating Reflectometer Results

The locating reftectometer is a frequency-swept microwave instrument which, by analog Fourier transformation, converts the reflection coefficient, a function of frequency Gamma(s), into the spatial distribution of the reflection coefficient Gamma(x). It will be shown that by the method of deconvolution an increase in axial resolution may result. By making use of the fact that the real and imaginary parts of the "locating plot" Gamma(x) are a Hilbert transform pair, a signal-to-noise ratio improvement is achieved by averaging the results of complex deconvolution using only the real and then only the imaginary parts of the locating plots. A number of experimental results are given, illustrating the increase in axial resolution when the method of band-limited deconvolution is applied to some typical waveguide components and obstacles.     

A PML using a convolutional curl operator and a numerical reflection coefficient for general linear media

A general time domain representation of the Chew and Weedon [1994] stretched coordinate perfectly matched layer (PML) absorbing boundary condition is described. This new approach mathematically operates on the spatial field derivatives and allows the PML update equations to be trivially derived from any set of general linear medium update equations. A method for calculating the frequency dependent reflection coefficient for this form of the PML is derived for general linear media. Two and three dimensional numerical test results, which validate the calculation of the reflection coefficient, are presented. The range of numerical tests include the PML matching of free space, a magnetoplasma, and a free space waveguide. Improving the reflection coefficient is examined.     

Conductive contacting spheres on the centre of the broad wall of rectangular waveguides

It has been found that metallic balls (held by external magnets) in rectangular waveguides produce a frequency-independent reflection, and an empirical formula is given for the magnitude of the reflection coefficient.     

用反射透射系数递推算法计算有限周期光子晶体的带隙结构

提出了一种计算光子晶体带隙结构的新方法,即用反射透射系数递推算法(RTCM)对不同介电常数,不同结构特点一维光子晶体的带隙结构进行了讨论,计算结果表明本文所提出的方法物理概念清晰,公式简洁。     

测量表面张力和接触角的简单方法和装置

利用激光束在液体柱面弯月面上的反射推导了计算表面张力和接触角的公式，并用简单的实验装置测量了水的表面张力系数和接触角。     

Characterization of dynamics and power handling of RF MEMS using vector measurement techniques

This paper proposes a new method to measure dynamics and power handling of RF microelectromechanical systems (MEMS) devices based on a mobile membrane. The method uses in-phase/quadrature demodulation of an RF signal proportional to the reflection coefficient of the measured device, which contains information of its mechanical properties, such as actuation and release times and instantaneous position of the mobile membrane. Both one-port (capacitors) and two-port devices (switches and extended tuning-range capacitors) can be measured. Its main advantage is the capability of obtaining information from both magnitude and phase variations of the device reflection coefficient to characterize its dynamics and power handling. It is shown that detecting phase is advantageous in high quality factor capacitors, where the magnitude of the reflection coefficient is nearly constant for any position of the mobile membrane. Open-short-load calibration of the system is provided in order to obtain absolute measurements, which are necessary for power-handling characterization. The performances of the proposed method are demonstrated by comparison to systems based on detection of the magnitude of the reflection coefficient. A MEMS capacitor is characterized in terms of dynamics-actuation and release times, and mechanical resonance frequency and in terms of power handling-membrane instantaneous position and phase and tuning range variation.