Electromagnetic coupling to a conducting wire behind an aperture of arbitrary size and shape

The electromagnetic coupling to a conducting wire behind an aperture in a plane conducting screen is analyzed. The aperture can be of arbitrary size and shape. The wire can be of finite length, with or without terminating loads, or of infinite length. The electric current on the wire and the equivalent magnetic current over the aperture region are calculated by the method of moments. An equivalent circuit for the effect of the aperture on the transmission line mode of the wire is derived.     

EMC prediction model of a single wire transmission line crossing acircular aperture in a planar screen

The structure composed by a wire running above a ground plane and passing through an aperture in a semi-infinite metallic screen is analyzed from an electromagnetic point of view. We assume that the distance between the wire and the ground plane is sufficiently greater with respect to the aperture dimensions and that the latter are small in comparison with the free-space wavelength. A very accurate low frequency solution is obtained by representing the field quantities in a suitable spectral domain and by treating the wire current as a filament current. A transmission line model of the structure, based on the scattering parameter representation for both internal and external excitation, is derived. Then, by use of such a model, analytical expressions for an insertion loss and a signal-to-noise ratio (SNR) are obtained in order to assess the electromagnetic compatibility of the structure     

波纹喇叭差模耦合点的分析

通过对波纹喇叭基本理论的分析,描述了波纹喇叭具有的特殊参数点(低频截止点、快慢波分界线、平衡混合条件、高频截止条件、短路条件)的表达式及特征。以此为依据,详细讨论了在波纹喇叭中主模HE11与差模HE21共存的条件,以及在波纹喇叭内的差模临界截止点的分析。通过寻找到电流或者是电压的波腹点,由此可以更准确选定好开耦合口的位置。     

C波段差模耦合波纹喇叭

通过对波纹喇叭基本理论的分析,描述了波纹喇叭特殊参数(低频截止点、快慢波分界线、平衡混合条件、高频截止条件、短路条件)的表达式及特征。通过对波纹喇叭内差模临界截止点的分析,找到电流或者电压的波腹点,更准确地选定开耦合口的位置。为了使差模信号反射小,主要考虑了波纹喇叭的HE₂₁模式与矩形波导的TE₁₀模式匹配、耦合孔与矩形波导的匹配,以此为依据,选择矩形波导尺寸和耦合孔的尺寸。利用Ansoft软件建立一个C波段波纹喇叭差模耦合模型,仿真计算结果与理论分析吻合,实物测试结果也与理论分析一致,证明了这种设计理论在工程应用中是可行的。     

Wire Optimization and Delay Reduction for High‐Performance on‐Chip Interconnection in GALS Systems

To address the wire complexity problem in large‐scale globally asynchronous, locally synchronous systems, a current‐mode ternary encoding scheme was devised for a two‐phase asynchronous protocol. However, for data transmission through a very long wire, few studies have been conducted on reducing the long propagation delay in current‐mode circuits. Hence, this paper proposes a current steering logic (CSL) that is able to minimize the long delay for the devised current‐mode ternary encoding scheme. The CSL creates pulse signals that charge or discharge the output signal in advance for a short period of time, and as a result, helps prevent a slack in the current signals. The encoder and decoder circuits employing the CSL are implemented using 0.25‐μm CMOS technology. The results of an HSPICE simulation show that the normal and optimal mode operations of the CSL achieve a delay reduction of 11.8% and 28.1%, respectively, when compared to the original scheme for a 10‐mm wire. They also reduce the power‐delay product by 9.6% and 22.5%, respectively, at a data rate of 100 Mb/s for the same wire length.     

Aperture Excitation of a Wire in a Rectangular Cavity

The problem of determining the currents excited on a wire enclosed within a rectangular cavity is considered. The wire and cavity interior are excited by electromagnetic sources exterior to the cavity which couple to the cavity interior through a small aperture in the cavity wall. It is assumed that the wire is thin, straight, and oriented perpendicular to one of the cavity walls. An integral equation is formulated for the problem in the frequency domain using equivalent dipole moments to approximate the effects of the aperture. This integral equation is then solved numerically by the method of moments. The dyadic Green's function for this problem are difficult to compute numerically; consequently, extensive numerical analysis is necessary to render the solution tractable. SampIe numerical results are presented for representative configurations of cavity, wire, and aperture.     

On bounding the excitation of a terminated wire behind an aperture in a shield

A formulation is developed for determining the voltage and current induced on an impedance-terminated wire behind an aperture in a shield. Loading effects on the aperture are included by using receiving antenna theory. Upper bounds for the current and voltage are obtained and numerical results are presented for a thin slot antenna.     

Electromagnetic excitation of a wire through an aperture-perforated conducting screen

Integro-differential equations are formulated for the general problem of a finite-length wire excited through an arbitrarily shaped aperture in a conducting screen. The wire is assumed to be electrically thin and perfectly conducting, and it is arbitrarily oriented behind the perfectly conducting screen of infinite extent. A known, specified incident field illuminates the perforated-screen/wire structure. The integro-differential equations fully account for the coupling between the wire and the aperture/screen. They are specialized to the case of the wire parallel to the screen with the aperture a narrow slot of general length. These special equations are solved numerically and data are presented for wire currents and aperture fields under selected conditions of wire/slot lengths and orientation. Data indicative of the coupling between the wire and slot are presented.     

Coupling through narrow slot apertures to thin-wire structures

Electromagnetic coupling through a narrow slot aperture in an infinite ground plane is considered when a thin wire is present in the coupled half-space. The effect of the wire on coupling is determined. The slot has width and depth. The method of moments is applied to determine equivalent aperture currents and wire currents. Then coupling is calculated from the resulting fields. Results are presented for high and low Q slots and on and off resonance     

Transient current on a wire penetrating a cavity-backed circular aperture in an infinite screen

The problem of a wire penetrating a circular aperture in an infinite conducting screen and entering a circular cylindrical cavity is considered. Results for the transient current propagating along the wire both inside and outside the cavity are presented. The current in both regions is evaluated in the frequency domain by the method of moments (MOM). An approximate method for evaluating the exterior current at an observation point far from the aperture is discussed. To obtain the transient response, a numerical inverse Fourier transform is used. The current response is examined as a function of cavity and aperture dimensions. Results obtained with the approximate method are compared with the MOM solution. It appears that information concerning the interior cavity dimensions is present in these exterior observations.<>     

N槽结构波纹喇叭的理论分析

本文利用空间谐波法导出了N槽结构(每个周期有N个槽)波纹喇叭的特征方程和等效壁导纳的普遍公式,并把这些公式应用于双槽深波纹喇叭,给出了其等效壁导纳的表达式。文章还对一个双槽深波纹喇叭的等效壁导纳、特征值、口面模比和辐射方向图进行了数值计算,并与实验结果比较,两者吻合得很好。     

Optimization of Broadband Smooth-Wall Circular Horn Antennas

This paper presents the optimization and characterization of broadband circular horn antennas with smooth walls. These antennas are simpler and easier to manufacture than corrugated horns. They work by converting the incoming fundamental mode to a mode mixture, whose total field corresponds to a Gaussian beam pattern at the aperture. The geometry of the horn is found by an optimization algorithm. While smooth-wall horn antennas have been designed for many years, they are inherently band limited because they rely on a correct multimode interference in the aperture to match the total field to a Gaussian distribution. The presented method achieves significantly larger bandwidths by allowing the Gaussian beam parameters, and thus the required mode spectrum in the aperture, to vary with the frequency. Together with an appropriate mirror optics, a receiver system with a bandwidth of more than 3 octaves could be realized.     

Transient current propagation along a wire penetrating a circularaperture in an infinite planar conducting screen

The shielding properties of a wire penetrating an infinite planar screen are considered. Time domain results are presented for the case of a transient current pulse propagating along the wire. These results are obtained by first computing numerical solutions for the problem in the frequency domain and then utilizing the inverse Fourier transform. Two double exponential pulses with differing characteristics are considered. Numerical results for the two pulses are compared to determine the effects of the pulse characteristics on the shielding properties of the geometry. Applications to via structures in high-speed circuits are also briefly discussed. It is observed that even for very small apertures, the effect of the screen on the low-frequency pulse is negligible. As the pulse width decreases, the effect of the screen becomes more prominent. For the high-frequency case, the pulse is significantly affected by the screen. Unlike the low-frequency pulse, the amplitude of the high-frequency pulse is dependent on the aperture size. Even for large apertures, the attenuation becomes significant as the current propagates down the wire. It is shown that as the width of the input pulse decreases, the distortion in the pulse shape becomes more pronounced. This effect is especially important in applications related to high-speed integrated circuits     

The transfer impedance of cables with a nearby return conductor anda noncentral inner conductor

The transfer impedance Z_t of a cable is often assumed to be a characteristic of the shield only. We investigate the limits of this assumption by calculations and measurements. The first test cable was formed by a solid copper tube (“shield”) and a wire inside; several positions, also non-central, were chosen for the wire. The common mode current (between 10 Hz and 100 kHz) through the tube had as return path a single wire, which was placed at several positions, near and at some distance from the shield. A second cable with a braided shield was tested as well. The results show that both the differential mode and the common mode circuit have to be carefully defined for a particular Z_t. Varying either circuit may alter Z_t drastically. Consequently, the Z_t of a particular cable measured in a triaxial setup, is a characteristic of that setup and cannot always be used in another setup as in for instance cable bundles     

Radiating apertures in a corrugated rectangular waveguide

A variational analysis for determining the scattering parameters of an aperture in the plane broad wall of a corrugated rectangular waveguide is described. To effect the analysis, a quasi Green's function for the loaded waveguide is postulated.     

余弦高斯光束通过硬边光阑的解析传输公式

从Collins公式出发,对余弦高斯光束通过有光阑限制的一阶ABCD光学系统的传输进行了研究,采用将矩形域函数表示为复高斯光束迭加的技巧,推导出了普适的场分布的解析公式。作为应用例,对余弦高斯光束通过有硬边光阑的薄透镜聚焦系统进行了数值计算,计算结果表明,作者的结果与直接由Collins公式衍射积分所得结果一致。数值计算证明,用该方法能节约大量机时,并可推广到其它光束通过硬边光阑光学系统的传输研究。     

高阶贝塞尔-高斯光束通过圆孔硬边光阑的传输特性

文章通过把圆孔光阑函数展开为有限复高斯函数和的方法,用惠更斯-菲涅尔衍射积分,推导出了高阶贝塞尔高斯光束通过具有圆孔光阑的近轴ABCD光学系统的传输近似解析公式,并对高阶贝塞尔-高斯光束通过圆孔硬边光阑的传输特性进行了研究.分析结果表明,衍射特性与截断参数、贝塞尔函数的阶数以及光束的菲涅尔数等因素有关.     

平顶高斯模式宽带激光通过光阑的光强分布

为了研究横向分布为平顶高斯模式的宽带激光通过硬边光阑系统的光强分布特性,采用衍射积分公式推导了平顶高斯模式宽带激光的每一频率分量在光阑系统中的传输公式,再通过傅里叶变换得到时间域的传输公式,详细分析了光阑和频带宽度对强度分布的影响。结果表明,近场光强在截断参量较大时,仍保持一定的平顶分布特性,但是随带宽的增加强度分布变窄;截断参量较小时强度呈高斯分布,并且带宽的变化对强度分布没有太大影响;然而在远场时截断参量较小情况下的光强分布也明显表现出随带宽增加而变窄的现象,但随着截断参量增大,这一变化趋势变缓。这些结果对平顶高斯模式宽带激光的应用具有重要参考价值。     

Low-profile helical array antenna fed from a radial waveguide

A low-profile array antenna composed of two-turn 4° pitch angle helices is designed for a frequency band of 11.7 GHz to 12.0 GHz. The feed wire of each helix is inserted into a radial waveguide through a small hole and excited by a traveling wave flowing in the transverse electromagnetic mode between the two parallel plates of the waveguide. The measured aperture efficiency shows a maximum value of 77% for a beam radiated in the normal direction and 69% for a 30° beam tilt     

光阑约束超几何激光束的传输特性

基于广义惠更斯-菲涅耳衍射积分和圆孔光阑函数展开为有限复高斯函数之和的方法,导出了超几何激光束通过有圆孔光阑约束的近轴ABCD光学系统传输的近似解析表达式,并对其传输特征进行了数值计算和分析。研究结果表明,超几何激光束光强的分布及其衍射效应与光阑的孔径大小、传输的距离以及光束参数等因素密切相关。此外,文中采用的近似解析方法与直接利用衍射积分计算相比,具有更高的计算效率,可以大大节省计算机时。