Scattering of waves from periodic surfaces

The scattering of waves from periodic surfaces is studied. We give a general review of this problem and compare three analytical methods for a conducting sinusoidal surface in detail for both TE and TM polarized waves. The three methods are: 1) the method developed by Masel, Merrill, and Miller (MMM); 2) the Modified Physical Optics (MPO) method; and 3) Waterman's Plane Harmonics (WPH) approach. We find the MMM method to be the most efficient one in terms of the rate and range of convergence. For dielectric media with periodic rough surfaces, an improved method is developed for calculating the reflected and transmitted powers. The results are used to compare with experimental data obtained at optical frequencies. It is shown that good agreement is achieved when the complex permittivity of the metal for the grating at the corresponding frequency is used.     

毫米波四脊方波导的研究

采用模式匹配法详细分析毫米波四脊方波导的传输特性。首先将对称加载四脊的方波导横截面分成三个子区域,将其中的电磁场分量用模式函数和的形式分别展开,通过在区域交界面上施加边界条件得到展开系数,进而得出本征方程。接着采用数值计算方法求出本征值和特性阻抗等重要参数,与参考文献中的结果比较吻合。最后采用上述方法设计了工作频段为18-40GHz的四脊方波导,它可用于毫米波双极化或圆极化宽带喇叭天线的馈源传输线。     

A new iterative diakoptics-based multilevel moments method forplanar circuits

This paper combines a multilevel moments method (MMM) scheme with a modified diakoptics (MD) technique and a block Gauss-Seidel (BGS) iterative technique to reduce the solution time of large planar microwave structures. The proposed MMM scheme has two levels. On the lower level, the planar circuit is divided into several subcircuits using two types of artificial ports. At the higher level, general basis functions defined over the complete circuit are generated in an iterative way. The validity and the efficiency of the new technique are validated by several examples, including a large low-pass filter     

Numerical method for calculating surface current density on a two-dimensional scatterer with smooth contour

A numerical method is presented for finding the surface current density on a two-dimensional smooth scatterer. This method is an improved version of a method which one of the authors presented as an adjoint method to the conventional mode-matching method (MMM) for finding the scattered field. After formulating the problem, we interpret the method being adjoint to the conventional mode-matching method and show that the method yields a sequence of approximate current densities converging to the true density in the mean squares sense. Next we propose the improved method and prove the fact that this method yields a sequence of approximate solutions which converges to the true density uniformly on the contour of the scatterer. We then state that the method is an adjoint one to the mode-matching method with a smoothing procedure (SP) which we proposed as a powerful numerical method for the scattered field. Numerical results of some sample calculation are attached to show the effectiveness of the new method.     

Improved model-order reduction by using spacial information in moments

The new concept of multinode moment matching (MMM) is introduced in this paper. The MMM technique simultaneously matches the moments at several nodes of a circuit using explicit moment matching around s=0. As compared to the well known single-point moment matching (SMM) techniques (such as asymptotic waveform evaluation), MMM has several advantages. First, the number of moments required by MMM is significantly lower than SMM for a reduced-order model of the same accuracy, which directly translates into computational efficiency. This higher computational efficiency of MMM as compared to SMM increases with the number of inputs to the circuit. Second, MMM has much better numerical stability as compared to SMM. This characteristic allows MMM to calculate an arbitrarily high-order approximation of a linear system, achieving the required accuracy for systems with complex responses. Finally, MMM is highly suitable for parallel-processing techniques especially for higher order approximations while SMM has to calculate the moments sequentially and cannot be adapted to parallel processing techniques.     

电子设备多学科主模型及其建立技术

通过电子设备多学科主模型相关技术研究,归纳了电子设备多学科主模型概念及其特点,明确了综合化电子设备多学科综合优化模型组成,提出了两种基于多学科主模型技术的综合优化模型建立技术及其实现途径,为多学科优化设计技术研究和电子设备多学科优化设计平台开发奠定了技术基础.     

关于Montgomery模乘迭代的可控性分析

在公钥密码实现中,Montgomery模乘扮演着非常重要的角色。本文研究Montgomery模乘(MMM)的迭代控制结构,给出了进行MMM迭代的输入边界控制条件,以及改进的MMM算法。这种扩展的迭代控制条件适合用于复杂求幂的迭代过程,在其边界控制下可直接进行一些加法、减法及乘法等基本运算,而无须模约化处理。给出的模乘迭代算法具有高度的灵活性,可利用来实现安全高效的RSA、ECC等公钥密码体制。     

Generalized Modal Scattering Matrix of Bandpass Filters Using Ridged Waveguides

Simple and accurate integral equation formulation using a three dimensional finite element (3DFEM) to determine the propagation of microwave passive structures is presented. This technique is applied to solve the scattering problems due to various forms of irises in lossless rectangular waveguide.The analysis of these components is highly dependent of the numbers of modes considered in the neighbourhood of the discontinuity. The theoretical model is compared with measurements and Mode Matching Method (MMM). Results are found to be good agreement.     

CSSA-低功耗Montgomery模乘的环形脉动阵列

文章提出了一种环形脉动阵列CSSA（Circular Structured Systolic Array），用于实现Montgomery模乘算法MMM（Montgomery Modular Multiplication）。该阵列采用循环结构，迭代计算。仿真结果表明，与基于一维脉动阵列的MMM硬件实现相比，该结构牺牲了运算时间，但是降低了功耗和芯片面积（本文实现的两个例子，功耗和芯片面积均减少了约97％）。并且，处理单元的数量可配置，以平衡速度和功耗。     

Efficient simulation of switched networks using reduced unificationmatrix

A new and simple formulation method for switched networks in the numerical time domain is presented. Unification models of switching devices, companion models of energy-storage elements, and several straightforward circuit-manipulated operations are used in obtaining a reduced unification matrix (RUM). The feature of the constant formulated RUM is clarified, and the selection of the main parameters of unification models is illustrated. A condition of reducibility is proposed to determine how small the dimensions of a modified nodal matrix (MNM) can be reduced to. Simulation results using the RUM method demonstrate its superiority over the commonly used MMM method, not only for memory requirements, but also for computational speed. A large circuit example shows that the RUM method offers a 76.32% time savings in computation. Additionally, the RUM method possesses the merits of easy formulation, easy programming and more realistic switch modeling, as well as greater accuracy and higher time efficiency when compared with commonly used state-space approaches. These combined advantages should make the proposed RUM method very attractive in the time-domain simulation of switched networks. For large switched networks, the decided advantages are very great     

梯形截面介质光波导的模方程

本文简化了有效折射率法和WKB法对梯形截面介质光波导传输特性的分析过程,给出了计算E_(mn)~X模有效折射率的近似模方程,并用数值计算结果和实验结果检验了该模方程的精度。     

基于帧填补的MMM Clos网络按序分组交换算法

与其它类型的Clos网络相比,各级带缓存的MMM(Memory-Memory-Memory)Clos网络使得交换网络的配置时间最小化,但是MMM交换中间级缓存的存在会引起输出端口的信元乱序。该文提出了一种满帧填补扩展算法(EPF),采用逐帧转发的方式来避免MMM Clos网络中的乱序问题。新算法在输入级和输出级采用固定周期轮转方式,中间级采用最早信元优先输出调度,具有复杂度低,可分布式控制,以及不需要缓存加速的特点。分析和仿真结果表明该算法是稳定的,即输入输出为可允许业务时,算法可达100%吞吐率。     

A single-period TE02-TE01 mode converter in ahighly overmoded circular waveguide

A single-period 60 GHz TE₀₂-TE₀₁ mode converter for use in an electron cyclotron heating (ECH) system for magnetically confined plasmas is presented. The mode converter is very compact and has a broad bandwidth and a theoretical conversion efficiency of 97.6%. A method of computing the reflection from converters is presented and used to show that reflection from the single-period mode converter is minimal. Experimental results are consistent with theoretical calculations     

A novel marker design for magnetic marker monitoring in the human gastrointestinal tract

Magnetic marker monitoring (MMM) is a technique to determine the motility of the gastrointestinal tract and to observe the dissolution of pharmaceutical compounds. Today's magnetic markers usually consist of magnetized magnetite. Because of their weak magnetic fields, highly sensitive sensor systems are required. For a wider class of applications, stronger markers and more flexible measurement setups are necessary. In this paper, a novel marker design is introduced. This marker comprises one permanent magnet and a compartment of iron powder in a magnetically unstable configuration. During dissolution of the pharmaceuticals, the powder is redistributed around the magnet, thereby altering the externally measured magnetic induction. Based on this design, magnetically marked tablets and capsules were prepared and their magnetic field during dissolution was observed. Magnetic induction values were between 16 and 0.2 μT at distances of 5-30 cm, which is considerably higher compared to the pico-Tesla range of conventional markers. During dissolution, the magnetic induction decreased by between 14% and 27%. These values could be confirmed in detailed finite element method simulations. In conclusion, the present results indicate that our novel marker design is well suited for MMM with more flexible sensor technologies, such as magnetoresistive sensors.     

Ray-Optical Analysis of Electromagnetic Scattering in Waveguides

The ray-optical method presented previously for the analysis of scalarizable waveguide discontinuity problems is extended to vector scattering problems wherein an incident TE or TM mode excites both mode types. The procedure is illustrated first for reflection of an obliquely incident mode from the open end of a parallel plane waveguide, and is then applied to reflection from an open-ended circular waveguide. Formulas for modal reflection and coupling coefficients are given to various degrees of approximation, depending on whether or not multiple interaction phenomena are considered in addition to the simplest primary diffraction effects. Comparison with data computed from exact solutions for the circular waveguide problem shows that the ray-optical method is remarkably accurate not only in the strongly overmoded but also the dominant mode regimes.     

印刷电路板差分线边缘布置的电磁兼容分析

利用有限元法对差分信号线置于板子边缘的不同距离进行分析,得出差模阻抗和共模阻抗的变化,并且分析了散射参数,提取了系统的SPICE模型,分析了该边缘效应引起的共模噪声的变化以及造成的系统损耗,得出差分布线距离电路板的最小长度,并对差分布线的设计规则提供指导.     

A New Method to Extract Bulk Carrier Mobility in Germanium-on-Insulator

A new method is presented to extract bulk carrier mobility of germanium-on-insulator (GeOI) films based on the data from the depletion mode of four-point probe pseudo-MOSFET measurement. Analytical models of the conductance in depletion region and related parameter extraction procedures are presented. This method is validated with both GeOI and silicon-on-insulator substrates prepared by layer transfer.     

A modal analysis of TEM mode in circular-rectangular coaxialwaveguides

A modal analysis of transverse electromagnetic (TEM) mode in a circular-rectangular coaxial waveguide is presented in this paper. The analysis is based on the modal-expansion technique. Analytic expressions for the characteristic impedance and attenuation coefficient are derived from the solution of the TEM mode. The calculated results are compared with those of the finite-element method, as well as published data. Excellent agreement is observed     

Improved mode properties of unstable resonators with tapered reflectivity mirrors and shaped apertures

The use of tapered reflectivity mirrors and shaped apertures in unstable resonators is shown to be an effective method for improving the mode properties. Mode intensity and phase profiles are smoothed and the mode discrimination ratio is increased. Results are presented illustrating the importance of diffracted waves from sharp mirror edges in determining these mode properties. A simple expression for estimating the diffractive contribution is given and is used to determine optimum mirror designs. Shaped mirrors and mirrors having amplitude and phase reflectivity tapers are studied. The concept of equivalent Fresnel zones is used to gain physical insight into the mode properties.     

An approximate but accurate analysis of the dielectric wedge antenna fed by a slab waveguide using the local mode theory and Schelkunoff equivalence principle

A computationally efficient method to obtain design parameters for tapered radiators is presented. The method uses a local mode theory in conjunction with the Schelkunoff equivalence principle. Radiation patterns of directive gain for dielectric wedge antennas of varying lengths and different dielectric constants are presented. Both the TE and TM cases are considered. The method is validated by comparison with data obtained from a recently developed more rigorous mode-matching method. Excellent agreement is obtained over the physically important angular range from endfire to broadside for the TE case and over the angular range spanned by the major lobe for the TM case.