Automated Topology Design for Electromagnetic Devices

In this paper a novel automated design procedure based on the integration of a full wave Finite Element Analysis (FEA) and a topology design method employing Sequential Linear Programming (SLP) is introduced. The employed topology design method is the Solid Isotropic Material with Penalization (SIMP) technique which is formulated as a general non‐linear optimization problem. SLP is used to solve the optimization problem with the sensitivity analysis based on the adjoint variable method for complex variables. A key aspect of the proposed design method is the integration of optimization tools with a fast simulator based on the Finite Element‐Boundary Integral (FE‐BI) method. The capability of the proposed design method is demonstrated by designing a patch antenna subject to pre‐specified bandwidth and miniaturization criteria. Results show that the proposed design method is capable of designing full three‐dimensional volumetric material textures and printed conductor topologies for filters and patch antennas with enhanced performance. © 2004 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87915/2/2155_1.pd

Parallel computation of 3-D electromagnetic scattering using finite elements

The finite element method (FEM) with local absorbing boundary conditions has been recently applied to compute electromagnetic scattering from large 3-D geometries. In this paper, we present details pertaining to code implementation and optimization. Various types of sparse matrix storage schemes are discussed and their performance is examined in terms of vectorization and net storage requirements. The system of linear equations is solved using a preconditioned biconjugate gradient (BCG) algorithm and a fairly detailed study of existing point and block preconditioners (diagonal and incomplete LU) is carried out. A modified ILU preconditioning scheme is also introducted which works better than the traditional version for our matrix systems. The parallelization of the iterative sparse solver and the matrix generation/assembly as implemented on the KSR1 multiprocessor is described and the interprocessor communication patterns are analysed in detail. Near-linear speed-up is obtained for both the iterative solver and the matrix generation/assembly phases. Results are presented for a problem having 224,476 unknowns and validated by comparison with measured data.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50413/1/1660070504_ftp.pd

Comparison of Semi-Analytical Formulations and Gaussian Quadrature Rules for Quasi-Static Double Surface Potential Integrals

This paper presents a comparison of a new semi-analytical expression with Gaussian-quadrature formulas for the quasi-static double-surface potential integrals arising in the boundary integral (BI) models of micron-size objects, such as RF-MEMS switches. The integrals considered are the quasi-static Green's functions for the scalar and vector potentials, with constant or linear basis functions over triangular subdomains. The examples given illustrate that the new semi-analytical formulations can achieve significantly higher solution accuracy and are more efficient when compared to the Gaussian-quadrature formulas.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87252/4/Saitou47.pd

Perfectly matched layer termination for finite-element meshes: Implementation and application

Perfectly matched layer (PML) absorbers deteriorate the condition of the resulting finite-element sparse systems. Therefore, poor convergence scenarios are observed when an iterative solver is employed. In this work, we show that, by choosing the PML parameters in an optimal manner, substantial speedup in the solution convergence is achieved without affecting PML absorption. A robust preconditioned solver with nearly no breakdown possibilities is suggested, implemented, and tested for two microwave circuit applications. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 23: 166–172, 1999.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/35043/1/11_ftp.pd

High frequency scattering by a smooth coated cylinder simulated with generalized impedance boundary conditions

http://deepblue.lib.umich.edu/bitstream/2027.42/7846/4/UMR0471.pd

Fully Integrated Electrothermal Multi-Domain Modeling of RF MEMS Switches

RF MEMS switches have demonstrated excellent performance. However, before such switches can be fully implemented, they must demonstrate high reliability and robust power-handling capability. Numerical simulation is a vital part of design to meet these goals. This paper demonstrates a fully integrated electrothermal model of an RF MEMS switch which solves for RF current and switch temperature. The results show that the beam temperature increases with either higher input power or increased frequency. The simulation data are used to predict switch failure due to temperature-related creep and self pull-in over a wide range of operating frequency (0.1-40 GHz) and power input (0-10 W). Self pull-in is found to be the dominant failure mechanism for an example geometry.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87264/4/Saitou33.pd

Lifetime Extension of RF MEMS Direct Contact Switches in Hot-Switching Operations by Ball-Grid-Array (BGA) Dimple Design

Direct contact RF microelectromechanical systems switches have demonstrated excellent ultrawideband performance from dc to 100 GHz. However, they are prone to failures due to contact adhesion and arcing, particularly for pure-gold/pure-gold contacts. In this letter, we present a new contact design employing ball grid array (BGA) dimples that limit the effective contact area to a few tens of nanometers in diameter. We experimentally show the performance of the BGA dimple with pure-gold/pure-gold contacts and demonstrate RF power handling greater than 1 W during hot switching in excess of 100 million cycles.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87268/4/Saitou10.pd

Analysis of RF-MEMS Switches Using Finite Element-Boundary Integration with Moment Method

This paper presents a new hybrid methodology for modeling RF-MEMS switches. This method combines the usual finite element-boundary integration (FE-BI) method for the fixed section of the switch, and the method of moments for the movable beam. This approach is intended to address the large 100:1 scale variation within a single computational domain, which also spans a very small fraction of a wavelength.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87249/4/Saitou98.pd

Hybrid finite element modelling of conformal antenna and array structures utilizing fast integral methods

Hybrid finite element methods (FEM) which combine the finite element and boundary integral methods have been found very successful for the analysis of conformal finite and periodic arrays embedded on planar or curved platforms. A key advantage of these hybrid methods is their capability to model inhomogeneous and layered material without a need to introduce complicated Green's functions. Also, they offer full geometrical adaptability and are thus of interest in general-purpose analysis and design. For the proposed hybrid FEM, the boundary integral is only used on the aperture to enforce the radiation condition by employing the standard free space Green's function. The boundary integral truncation of the FEM volume domain, although necessary for rigor, is also the cause of substantial increase in CPU complexity. In this paper, we concentrate on fast integral methods for speeding-up the computation of these boundary integrals during the execution of the iterative solver. We consider both the adaptive integral method (AIM) and the fast multipole method (FMM) to reduce the complexity of boundary integral computation down to []( N α ) with α <1.5. CPU and memory estimates are given when the AIM and FMM accelerations are employed as compared to the standard []( N 2 ) algorithms. In addition, several examples are included to demonstrate the practicality and application of these fast hybrid methods to planar finite and infinite arrays, frequency selective surfaces, and arrays on curved platforms. Copyright © 2000 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/35033/1/347_ftp.pd

Contact Physics Modeling and Optimization Design of RF-MEMS Cantilever Switches

RF MEMS direct-contact switches exhibit many advantages over the conventional semiconductor switches; however, existing drawbacks such as low power handling, high pull-in voltage and long switch opening time are most critical. This paper presents an optimization design for an RF-MEMS cantilever direct-contact switch to achieve maximum power handling capability, minimum pull-in voltage and switch opening time simultaneously. A 2-step optimization technique is proposed to achieve the optimal design to allow for a power handling capability of 130 mW, a pull-in voltage of 52 V, and a switch opening time 4.4 _s presented. The optimization results show that substantial room exists for improving the current designs of RF MEMS direct-contact switches.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87255/4/Saitou72.pd