Advanced Simulators Focus On EM Fields

April 14, 2008
A variety of electromagnetic (EM) simulation tools are available for planar and full three-dimensional analyses, as stand-alone tools or integrated into complete design software suites.

Electromagnetic (EM) simulation software is no longer a luxury but now an essential tool in any practical highfrequency design effort. The number of commercial programs has grown steadily over the years, providing RF/microwave designers with an unprecedented number of choices in EM simulators, including software for analysis of planar designs as well as full three-dimensional structures. Most of these EM tools link seamlessly to other computer-aided-engineering tools, such as linear and nonlinear circuit simulators, or can be supplied as part of a CAE software suite complete with layout editors and even optimizers.

EM simulators come in many forms with various degrees of capability. For example, software based on the method of moments (MoM) or finite-element method (FEM) analysis can provide fast predictions and two-dimensional (2-D) visualizations of electric and magnetic fields around a planar structure. For greater detail, a planar 3-D EM simulator can show current flow in three dimensions and can be applied to many planar circuits. For full 3-D analysis, a simulator using finite-difference timedomain (FDTD) technology can provide the greatest detail, but also require the greatest computational power and processing time.

Many available EM simulators can be found within a collection or suite of software tools that may include linear and nonlinear circuit simulators, layout tools, and optimization tools. For example, Computer Simulation Technology (CST, offers a variety of EM-based software tools in its CST STUDIO SUITE, designed to be used in companion, including the CST MICROWAVE STUDIO, which simplifies the application of EM simulation to high-frequency problems, the CST DESIGN STUDIO, which allows the combination and analysis of results from diverse simulators, and the CST EM STUDIO, which is tailored to the analysis of static low-frequency structures.

In adding to its EM-based product offerings, CST completed its acquisition of several EM product lines and its associated technology from Flomerics ( this past January, including the MicroStripes and FLO/ EMC products.

Earlier this year, the company announced the addition of two new products to its CST Studio Suite, the CST PCB STUDIO and the CST CABLE STUDIO. The former is designed for the analysis of electromagnetic interference (EMI) and electromagnetic compatibility (EMC) of printed-circuit boards, including analog, digital, mixed-signal, and power-supply issues. The latter program is designed for the analysis of signalintegrity (SI), EMC, and EMI effects in cable harness systems. It can be used to optimize shielding, weight, and size of single wires and cable assemblies.

Ansoft Corp. ( is well known for its High-Frequency Structure Simulator (HFSS) software for fullwave EM simulation of high-frequency/ high-speed components, circuits, connectors, and antennas. The latest edition of HFSS, version 11, offers a host of improvements over earlier versions of the industry-standard EM software, including new higher-order hierarchical basis functions and an iterative solver for generating smaller meshes and more accurate solutions for large, multiple-wavelength structures. In addition, version 11 provides analysis for Floquet ports for the analysis of frequency-selective materials and phased-array antennas.

Ansoft integrates its many software tools through its Ansoft Designer environment, which provides access to HFSS, its Nexxim circuit simulator, and its SIwave signal-integrity analysis tool. Ansoft also offers useful literature on its site, including a detailed, 58-page document on the EM simulation of packages for low-noise amplifiers (LNAs) and voltage-controlled oscillators (VCOs) in CMOS written by Dr. Nick Campbell, application engineer for Ansoft Corp. Europe (and available directly at

Applied Wave Research (, which late last year celebrated its tenth anniversary, offers the full-featured Microwave Office suite of high-frequency design tools with the EMSight EM simulator being one of the available design tools within that suite. The Microwave Office suite also works with third-party software, such as the APLAC circuit simulator. Also, the firm recently created the EM Socket open standard interface for accessing a wide range of EM tools without leaving the Microwave Office environment, including EM simulators from CST, Flomerics (, Optimal Corp. (, Sonnet Software (, and Zeland Software (

In addition, the company recently introduced its stand-alone AXIEM ( EM simulator (see Microwaves & RF, December 2007, p. 82). In contrast to EMSight, which is designed for closed-boundary problems with the assumption that the circuit in question is contained within a rectangular conducting box, AXIEM is an openboundary solver that assumes a circuit or structure in free space. AXIEM is ideal for analyzing a variety of high-frequency designs, including PCBs, integrated circuits, and LTCC circuits. AXIEM is also better suited for handling arbitrarily shaped structures, with faster solution times for those problems.

Agilent Technologies ( announced the latest (fifth) release of its full-wave 3-D EM modeling and verification tool, the Antenna Modeling Design System (AMDS), earlier this year. Licensed from the State College, PA developer Remcom ( and originally released last June, this latest version of the EM antenna simulator offers a scripting feature for performance optimization and automation of complex designs such as the patch array antennas used in cellular telephones. The software allows engineers to use equations to define the geometry of complex antennas to optimize performance. Last year, Agilent completed full integration of EMDS into its Advanced Design System (ADS) electronic-design-automation (EDA) software platform, speeding the translation of layouts into EM models. The ADS platform also provides access to the company's planar EM simulation tool, Momentum.

In addition to its license arrangement with Agilent, Remcom offers extensive EM products and capabilities, including the latest version of its XFdtd software, Version 6.5. XFdtd is a full-wave 3-D EM solver based on the FDTD method. It features a fast-meshing algorithm to speed an analysis and supports hardware acceleration and cluster computing.

Zeland Software ( recently introduced version 5.5 of its FIDELITY FDTD full 3-D simulator for modeling high-frequency circuits, components, and antennas and performing EMI and EMC studies. The software can automatically generate a nonuniform mesh around a subject under study to model planar and 3-D structures with complex dielectric configurations. FIDELITY provides multiple 2-D and 3-D views to help visualize the fields around a structure. The latest version of FIDELITY features hardware acceleration, improved de-embedding for ports, and a Case Study User's Manual.

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Earlier this year, Zeland announced the release of version 14 of its IE3D EM Design System. The full-wave method-ofmoments (MoM) EM simulator is widely used in the design of high-frequency integrated circuits as well as densely packed circuits, such as millimeter-wave circuits and low-temperature-cofired-ceramic (LTCC) circuits. It is a powerful solution for antennas as well as high-temperaturesuperconducting (HTS) circuits.

Sonnet Software site (, which is celebrating 25 years of service to the high-frequency industry as a developer and supplier of innovative planar EM analysis tools, has grown from humble beginnings to offering a full line of EM EDA software products. The Sonnet Professional Suite of tools is mainly focused on 3-D studies of mainly planar structures. The latest version of the Sonnet Suite is release 11. The EM simulation tools are well suited for analyzing 3-D planar antennas and circuits, including coplanar waveguide, microstrip, stripline, waveguide, printed-circuit boards (PCBs) with multiple layers, and assemblies with combinations of the technologies. For those who need full 3-D high-frequency EM analysis, Sonnet has teamed with CST to offer and support that company's CST Microwave Studio to customers in North America.

Sonnet offers a great deal of useful guidance on its web site, helping potential customers choose the optimal EM simulation tool for their needs. For example, a technical paper written by Jim Rautio, Sonnet president and founder, "Testing Limits of Algorithms Associated With High-Frequency Planar Electromagnetic Analysis," compares EM simulations with measured data to help visitors to the site understand in terms of accuracy the practical upper-frequency limits of planar EM simulation tools such as Sonnet's powerful em simulation software.

In addition to supplying a free, fully functional evaluation copy of the Sonnet Suites to qualified customers on a 30-day trial basis, Sonnet offers a free scaled-down version of the Sonnet Suites as Sonnet Lite, which can be downloaded from the company's web site. It provides full-wave EM analysis for 3-D planar circuits and is easy to learn and use.

EM Explorer ( is now offering Version 5.0 of its EM Explorer 3-D EM solver. The software is ideal for simulating the fields of complex dielectric and complex magnetic materials. Based on the FDTD method, it provides complex electric (E) and magnetic (H) field information in amplitude and phase. The software is available in 32- and 64-b versions and in graphical user interface (GUI) and console versions for Windows.

Information on additional EM software simulators can be found by visiting the following web sites: Circuit Sage (, SPEAG (, SuperNEC (, and 2COMU (

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