EM And Math Software Aids RF/Microwave Design

April 16, 2009
The latest EM and mathematical software tools are gaining in speed and sophistication, taking advantage of the processing power of modern multicore-processor computers.

Software plays an increasingly important role in high-frequency design, especially as more functions are integrated into smaller circuits. Design engineers have a wide choice of computer-aided- engineering (CAE) software tools at their disposal, from full-featured, multi-program suites to single-function utilities. Two of the more versatile types of tools, mathematical and electromagnetic (EM) programs, help analyze a wide range of designs, from antennas to waveguide.

EM simulation programs apply Maxwell's equations to high-frequency and other structures to calculate the EM field behavior of those structures. Analysis can be presented as two-dimensional (2D planar) or three-dimensional (3D) field information, or a combination of the two, as 2.5-D studies. Because EM simulators rely on compute-intensive algorithms to solve the matrices representing Maxwell's equations at each frequency, older programs have required either long solution times for complex structures, or the processing power of computer clusters to reduce the computational time. With the availability of multicore microprocessors operating at faster clock speeds, however, EM code writers are taking advantage of new-found parallel processing power to speed results with EM simulators.

For example, the latest form of the SONNET Suites Professional collection of software from Sonnet Software, release 12, provides faster simulations than previous versions through the use of parallel processing on multicore central processing units (CPUs). Sonnet's matrix solver has been refined for parallel processing to achieve impressive gains in computing speed, as much as seven-fold faster when using a typical workstation with dual quad-core microprocessors.

The company has also developed two new versions of its em EM analysis engine. The Sonnet Desktop Solver, which is aimed at typical personal computers (PCs), uses two CPU cores in parallel to reduce computation time. The Sonnet High Performance Solver, geared for high-end workstations with dual quad-core CPUs, can work with as many as eight CPU cores for eight-way parallel solutions for each frequency. Combined with an improved meshing algorithm, the new Sonnet analysis engine provides analyses as much as 50 times faster solving speed than the firm's previous software release.

Another EM simulator taking advantage of shared memory multiprocessor (MPM) technology is version 7.0 of XFdtd (XF7) from Remcom. The full-wave EM solver is based on finite-difference time-domain (FDTD) analysis, with this latest version suitable for antenna design and analysis, biological EM analysis such as studies of specific absorption ratio (SAR) of EM energy, and microwave circuit design. The software features a streamlined user interface. It runs natively on Windows, Mac OS X, and Linux operating systems. The software is available in Pro and Bio-Pro versions. Both include 32- or 64-b analysis module, geometric modeler and post-processor capability to share memory with as many as eight microprocessor cores, and a variety of 3D CAE import modules. The Bio-Pro version also includes SAR capability.

The latest version of the High-Frequency Structure Simulator (HFSS) software from Ansoft, version 11, is also designed for improved processing speed. The fullwave 3D EM field simulator requires less time to solve complex geometries while consuming less computer memory. The latest version offers new automation features, user-interface refinement, and data linking capability. New capabilities include higher-order hierarchical basis functions that work with an iterative solver for achieving smaller meshes around multiple-wavelength structures; an enhanced port solver for tackling lower frequencies; and Floquet ports for analyzing frequency-selective surfaces and phased-array antennas.

Another trend in high-frequency software tools involves the addition of electromagnetic-compatibility/ electromagnetic-interference (EMC/ EMI) simulation to circuit simulators, nominally for the purpose of optimizing the signal-integrity (SI) performance of components and circuits. For example, Computer Simulation Technology (CST) announced the integration of cable, printed-circuitboard (PCB), and EMC/EMI simulation capabilities in the firm's CST STUDIO SUITE collection of software tools. The suite includes the CST PCB STUDIO and CST CABLE STUDIO programs which, as part of the CST DESIGN ENVIRONMENT, can make use of the CST MICROWAVE STUDIO time-domain solver to optimize 3D components.

For SI studies, Zeland Software now offers its IE3DSI software for developing packages, PCBs, integrated circuits (ICs), and monolithic microwave integrated circuits (MMICs). It features an automatic "layout-to-EM-model design flow" integrated with the Cadence Allegro PCB/Package Designer as well as with AWR Microwave Office, AutoCAD DXF, and GDSII databases. The software supports automatic 3D geometry model creation, including bond wires, dielectric material thicknesses, and interconnections. It employs proprietary nonuniform mesh generation and adaptive curve fitting for fast and accurate processing.

Zeland's IE3D-SI features mixeddomain SPICE simulation for analyzing transient behavior in the time domain and studying the time-harmonic nature of passive structures, including interconnections. The software can conduct broadband SPICE model extraction, and perform test signal simulation and analysis, as well as transmission-line analysis ad random or jitter-enables clock signal analysis with an eye-diagram display.

As a sign of the increased integration in EM software tools, Agilent Technologies and the 2009 version of the Advanced Design System (ADS) software helps circuit, package, board and system designers work with a single software platform (see figure). In addition to containing a range of component models for the latest cellular and wireless standards, including LTE and WiMAX, the software suite supports SI studies with fast eye-diagram optimization of multigigabit, high-speed serial links, where layout geometry, preemphasis and equalization are optimized for the lowest bit error rate (BER).

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ADS 2009 makes use of Agilent's X-parameters, device parameters based on nonlinear measurement data that can be used for studying the linearity behavior of amplifiers and transistors. It also features 3D EM parameterized components representing metal shields, antenna radomes, absorbers, packages, interconnects, finite dielectric substrates and wire bonds. For added efficiency, ADS 2009 operates with tools from Cadence and Mentor Graphics.

Applied Wave Research issued a challenge to users of EM simulation software that its solver, the AXIEM 3D planar EM simulator, could improve anly processing speed record by another commercial planar EM simulator, or lunch was on AWR. The AXIEM EM simulator seamlessly integrates with AWR's Microwave Office and Analog Office.

Mathematical software is more versatile than an EM simulator in terms of applications, since math software can be anywhere that relationships can be defined by equations. It can be used in electronic and electrical designs as well as in biological, chemical, mechanical, and thermal studies. A variety of web sites offer more information on math software, including Drexel University's The Math Forum, with reviews of free math programs and information on commercial symbolic processors, such as MathCAD, Maple, and Mathematica. The National Institute of Science and Technology (NIST) also offers its Guide to Available Mathematical Software (GAMS) at www.gams.nist.gov to help those seeking more on math software.

In terms of commercial packages, the Maple Toolbox for MATLAB from Maplesoft is a collection of tools for use with the MATLAB math software from The Mathworks. The Maple Toolbox for MATLAB can work with exact quantities, including fractions, radicals, and symbols. It can perform simplification quickly and accurately. Using symbolic technology, numeric approximations can be deferred until needed, working with symbolic parameters in a problem instead. The software provides access to over 4000 mathematical functions in Maple, covering a range of topics such as differential equations, statistics, calculus, and linear algebra.

The latest version of Mathcad, Version 14, from Mathsoft integrates standard math notation, text, and graphics in a single worksheet. The software is easy to use, requiring no special programming skills. It provides full unicode support for global collaboration and capture of intellectual property (IP). A new worksheet analysis functionality allows worksheets to be compared side by side.

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