Software Takes On Design "Wild Cards"

Nov. 9, 2010
By constantly pushing their tools beyond the limits of traditional simulation and modeling, software vendors are ensuring truer prototypes and faster, cheaper design.

Software has taken an increasingly dominant role in the design processfrom the controlling code for today's test and measurement equipment to solvers, simulators, and layout tools that are speeding the development of devices, circuits, and systems. Computer designs and simulations are closing the gap between predicted and measured results, thanks to the fact that the software accounts for more variables than ever before.

Computer-aided-engineering (CAE) software developers face the constant challenge of adding features and capabilities while making their tools easier to use. For example, ANSYS debuted Ansoft Designer 6.0 at this fall's European MicrowaveWeek (EuMW). It offers solver-on-demand technology that integrates both ANSYS' HFSS threedimensional (3D) electromagnetic (EM) -field simulation software and HSPICE, the integratedcircuit (IC) simulation tool from Synopsys. As a result, design engineers can quickly and accurately analyze signal-integrity, power-integrity, and EM-interference (EMI) problems from a single schematicand layout-based environment.

With the soon-to-be-released Advanced Design System (ADS) 2011 from Agilent Technologies, engineers should be able to more quickly and easily design multi-technology RF system-in-package (SiP) modules and perform complex EM simulations. This version of ADS enables co-design with multiple technologies (board, laminate, package, module, and IC). Also new is a use model that promises to simplify EM simulation by integrating both planar and 3D finite-element-method (FEM) EM tools. In addition, load-pull capabilities vow to deliver faster, better matchingcircuit design from measured data.

Also due out in January is Studio Suite 2011 from Computer Simulation Technology (CST), which includes the CST MICROWAVE STUDIO simulation software. The 2011 version offers enhanced material-property descriptions across its entire palette of available solvers. In addition, high-performance computing options will now be available for frequency-domain and integral-equation solvers. Both of CST MICROWAVE STUDIO's general-purpose EM solverstimeand frequency-domain toolscan provide sensitivity analysis for an arbitrary number of parameters in just one simulation run. The newly implemented trust region framework in CST STUDIO SUITE 2011 can apply sensitivity weighting to cut down optimization time. As such, yield analysis for 3D models is becoming available at virtually no additional computational cost.

The Sonnet suites of EM simulation software from Sonnet Software aim to simply provide very high accuracy in a planar EM simulator. Based on method-of-moments (MoM) solutions, these tools are particularly effective in predicting the performance of highfrequency circuits on increasingly thinner dielectric substrates, such as those used for millimeter-wave circuits and multilayer RF/microwave designs.

Key features of AWR Corp.'s Visual System Simulator (VSS) 2010 include time-delay-neuralnetwork (TDNN) amplifier behavioral models for including memory effects and measurement-data-interchange-format (MDIF) model support. The release also offers a phased-array element for radar design engineers. Enhancements have been made to the VSS RFA architect tool and new communication models and signal-processing blocks have been added. The release offers support for turbo codes used in third-generation (3G)/fourth-generation (4G) standards. It also includes a library and/or components that can be used to decode custom turbo codes.

SimRF from The MathWorks provides a component library and circuit-envelope simulation engine for the system-level design of RF communication systems (see figure). Its new circuit-envelope and harmonic-balance simulation technologies are built on the Simscape platform for modeling RF system architectures. Aside from performing multi-frequency simulations early in development, engineers can make effective tradeoffs in designs that include digital and analog/RF components.

When it comes to chip design, engineers are often forced to model the active and passive parts of an IC using separate field and circuit simulators. They then combine the results using simple approximations that do not account for EM-field coupling and interference, which often leads to inaccurate models. With no approximations, EM-Supreme 2010 from Powerful Electronic Design Automation Software (PEDASOFT) can be used for the EM modeling of passive structures, active components, and RF and millimeter-wave modules. This timedomain field-device-circuit co-simulator allows EM fields to pass through the components to model the chip's behavior as it is exhibited physically. EM-Supreme can simulate S-parameters and largesignal parameters including harmonics, compression point, load-pull, source-pull, and more.

Also hailing from PEDASOFT is EMCore 2010, a 3D EM field solver for planar-circuit and antenna simulation. It is capable of modeling both small-signal (i.e., S-parameters and impedances) as well as radiation patterns and fields for planar components like filters, antennas, couplers, RF IC and MMIC circuits, high-density interconnects, transmission lines, and microwave-circuit discontinuities. EMCore includes EM to study and model EM-distributed effects, coupling, and radiation as well as parasitic effects at RF and millimeter-wave frequencies on passive structures and systems.

For those concerned with tying layouts to circuit models, Intercept Technology offers a bidirectional flow between its powerful Pantheon layout software and ANSYS' HFSS EM simulator. The link allows a design to be started in either software. The effects may be viewed in the other program. For example, the EM effects of modifications to a hybrid circuit design can be viewed almost instantly.

As the broader software tools have continued to evolve, some targeted solutions also have emerged for specific microwave and RF applications. For example, Canada's National Research Council Institute for Biodiagnostics (NRC-IBD) recently teamed with Switzerland's Schmid & Partner Engineering AG (SPEAG) to offer a software platform for magnetic- resonance-imaging (MRI) scanner design. The software vows to provide all of the tools needed to design RF phased arrays in one user-friendly program.

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Essentially, the output of the SEMCAD X software forms the input to NRC's Musaik analysis software. Through three different versions, the NRC software also can accept experimental data as input or both simulated and experimental data. In doing so, Musaik enables the user to evaluate simulated array-coil designs and assess their parallel-imaging capabilities. The software also computes full, complex noise co-variance matrices. SEMCAD X from SPEAG is the latest-generation three-dimensional (3D), Finite Difference Time Domain (FDTD) and Finite Integration Technique (FIT) full-wave simulation software.

Software innovation also is aiding the progression of monolithic microwave integrated circuits (MMICs). Last month, for example, AWR announced a process design kit (PDK) for Cree's gallium-nitride, highelectron- mobility-transistor (HEMT) MMIC foundry process. The Cree/AWR PDK enables MMIC designers to model Cree's GaN HEMT MMIC process within AWR's Microwave Office software environment. To automatically radius and fillet corners when connecting different parts together, it leverages AWR's Intelligent Net (iNet) automated interconnect construction technology. In doing so, the PDK ensures design-rule-check (DRC) -compliant layouts and eliminates the need for manual editing.

One industry that has been perhaps the greatest driving force behind software's evolution is test and measurement. Increasingly, test-equipment vendors are placing as much emphasis on the software that is offered in their boxes as the boxes themselves. With software-defined-radio (SDR) roots, many boxes are upgradeable to handle today's evolving communications standards. For example, National Instruments' LTE Measurement Suite, which operates with RF signal generators and analyzers, is a software-defined test system based on NI automated test software and PXI modular instrumentation.

Test software also is increasingly being updated to increase ease of use while pinpointing design problems early in the process. With Signal Safari 2010, Aeroflex, Inc.'s demonstration version of the latest evolution of its software suite, engineers gain multi-domain analysis and data-generation capabilities for wireless- communication R&D, RF system testing, signal analysis, and SATCOM link testing. When coupled with the CS9000 broadband signal system, the software enables the advanced analysis of complex communications signal environments.

AWR's Microwave Office now supports S-functions that are nonlinear behavioral models developed by NMDG NV of Belgium. By adding NMDG S-function support, the software can support multiple, emerging, nonlinear behavioral models like Agilent's X-parameters and Mesuro's Cardiff model.

For its part, Agilent just introduced the next generation of its 89600 vectorsignal-analysis (VSA) software, ideally suited for analyzing complex modulated signals such as those used in 3G and 4G wireless communications systems. For example, the software supports custom orthogonal-frequency-divisionmultiplexing (OFDM) analysis and enhanced LTE analysis. These are just some examples of the many software solutions that are available to today's microwave designers. No matter how varied their target application or goal is, all of these solutions strive to ease the microwave and RF design process. Most importantly, they work to provide prototypes that work as predicted.

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