Coupled-line-based millimeter-wave CMOS spiral power dividers with tapered TLs

Analog Integrated Circuits and Signal Processing - We propose a power divider comprising of two parallel λ/4 coupled lines with a shared input signal line. An isolation resistor R is included...     

Multipoint Galerkin asymptotic waveform evaluation for model orderreduction of frequency domain FEM electromagnetic radiationproblems

In this paper, a model order reduction technique is presented. This technique, known as Galerkin asymptotic waveform evaluation (GAWE), or multipoint Galerkin asymptotic waveform evaluation (MGAWE) if multiple expansion points are considered simultaneously, can be used to reduce matrices describing electromagnetic (EM) phenomena generated through the finite element method (FEM) to a smaller space while still accurately approximating the characteristics of the original responses. The resulting solution procedure of using GAWE or MGAWE, to solve FEM equations allows for wideband frequency simulations with a reduction in total computation time. Numerical simulations using these methods are shown along with traditional methods such as using an LU decomposition at each frequency point of interest and asymptotic waveform evaluation (AWE). Comparisons in accuracy as well as computation time are also given     

A single-level dual rank IE-QR algorithm to model large microstrip antenna arrays

A single-level dual rank IE-QR algorithm is introduced so that the resulting dense method of moments (MOM) matrix is efficiently compressed. For a system of N equations, an amount of work of the order O(N/sup 2/) has traditionally been required for both matrix assembly and matrix-vector multiplication in an iterative matrix solver. The algorithm of the present paper reduces the memory requirement and CPU time for both matrix assembly and matrix-vector multiplication to O(N/sup 3/2/) making it practical to solve for large antenna arrays with full wave approach. In conjunction with a "geometric-neighboring" preconditioner for matrix solution using GMRES, the current approach solves problems involving large antenna arrays using only a fraction of what are needed by conventional MOM both in term of memory and total CPU time.     

A comparison of anisotropic PML to Berenger's PML and itsapplication to the finite-element method for EM scattering

The use of an anisotropic material for the boundary truncation of the finite-element method is considered. The anisotropic material properties can be chosen such that a plane-wave incident from free space into the anisotropic halfspace has no reflection. Because there is no reflection, the material is referred to as a perfectly matched layer (PML). The relationship between the anisotropic PML and the original PML proposed by Berenger (see J. Comp. Phys., vol.114, p.185-200, October 1994) is considered. The anisotropic PML is applied to the finite-element solution of electromagnetic (EM) scattering from three-dimensional (3-D) objects. Numerical results are presented to demonstrate the accuracy of the PML     

Solving electromagnetic problems using a novel symmetric FEM-BEM approach

This paper presents a novel symmetric finite element method-boundary element method (FEM-BEM) formulation for solving unbounded electromagnetic problems. The proposed method offers two very attractive features: 1) it is variational, leading to a symmetric system of equations and 2) the meshes for the computations of FEM and BEM can be nonconformal, leading to decoupled computations of FEM and BEM. The accuracy and efficiency of the method are studied for both electromagnetic radiation and scattering problems.     

一种新型的超导磁场单晶炉的研制

磁场对于半导体晶体生长过程中的熔体流动模式有着明显的影响,因而可以改善晶体的组分和杂质的分布。在半导体单昌生长过程当中利用超导磁场来抑制熔体的对流,采用这种方式既可以生长出优质的单昌又可以研究熔体的对流与扩散对生长半导体单晶的质量影响,本文报道了新近自行设计,制造的一种新型超导磁场直拉单晶炉。     

无线传感器网络自律分散区域结构的在线扩展

实际监控环境中,比如食品厂监控系统,随着生产线调整和新生产线的开发,传感器经常会重定位和重组织,并在重定位的时候会引起某一区域网络发生拥塞。提出了建立一种双层自治分散区域结构的方法,用来解决传感器网络堵塞的问题。所建立的这种结构解决了路由区域信息共享的问题,并且减少了在动态变化过程中传感器和网络的连接时间。最终实验结果表明这种方法可以达到无线传感器网络结构在线扩展的要求。     

低成本的UTRV三维可视化仿真测试系统设计

相对于常规飞行器,倾转旋翼飞行器原本就对飞控系统有着更高的要求,而其无人化后的产品UTRV(无人倾转旋翼飞行器)对此的需要还要更上一层楼.为了满足开发UTRV飞控系统的需要,有必要开发更加方便的飞控系统仿真测试环境.使用现有货架商品构建了一套UTRV三维可视化仿真测试系统.系统内含可调整的UTRV全飞行包线非线性气动模型,用于提供控制律开发和动态仿真;系统可以方便的替换飞控模块程序进行仿真实验,以此验证控制律;同时,仿真实验全程数据以直观的实时三维视觉仿真方式显示,有利于发现飞控系统缺陷.使用货架商品还大大降低了成本,非常适合中小研究所和大学使用.     

Optimization of subgridding schemes for FDTD

A procedure to optimize the coupling coefficients between fine and coarse mesh regions for two-dimensional (2-D) finite-difference time-domain (FDTD) subgridding algorithms is introduced. The coefficients are optimized with respect to different angles and expanded in a form suitable for FDTD computation     

Hierarchical vector finite elements for analyzing waveguiding structures

In this paper, we extend the finite-element method into hierarchical higher order bases and the inexact Helmholtz decomposition. With the help of hierarchical basis functions, the approach can adopt well into the p version adaptive process. On the other hand, the inexact Helmholtz decomposition enhances the stability of the finite-element procedure when the operating frequency is low or the element size is very small compared to the wavelength. This approach can also enhance the h version adaptive mesh refinement process since the process may cause very small elements near a singular region. To accomplish the inexact Helmholtz decomposition for the edge elements, the lowest order curl conforming basis functions, the tree-cotree splitting, is utilized, and the general procedure is presented. As a result, a combination of hierarchical higher order basis functions with the inexact Helmholtz decomposition can improve the efficiency and the stability of the hp adaptive mesh refinement process. The accuracy and stability of the proposed approach are also discussed through numerical examples.