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June 6, 2002

RF ICs, embedded memories to get airing at DAC

By Stephan Ohr
EE Times

May 30, 2002 (1:21 p.m. EST)

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    SAN FRANCISCO RF IC design platforms will be among the tools clamoring for attention when the 39th annual Design Automation Conference (DAC) opens June 10 in New Orleans. RF design tool startup Xpedion Design Systems Inc. will add fuel to the war of words already being waged by Agilent Technologies and Ansoft Corp., as the two latter companies unveil competitive offerings at the show.

    Elsewhere at DAC, fast-circuit-simulator manufacturers Nassda Corp. and Legend Design Technology Inc. will demonstrate the approach's application to embedded memory characterization, and a panel will explore the technology issues attached to the development and sale of analog intellectual property.

    The brouhaha in RF IC design tools began in February, when Agilent Technologies' EEsof group announced a "far-reaching" partnership with Cadence Design Systems Inc. Agilent is arguably the "2,000-pound gorilla" among RF design tool vendors and is the fifth-largest EDA software supplier, said marketing market Jim Tabuchi. Cadence, meanwhile, is inarguably the largest supplier of IC design tools: Its Analog Artist platform has an installed base of more than 15,000 users worldwide.

    The partnership, which covers joint research and development, is intended to create a single RF IC design flow on the Cadence platform.

    But no sooner was the partnership announced than RF design tool competitors began positioning themselves against it. Former Cadence marketer James Spoto, now president of Applied Wave Research Inc., called Agilent tools slow and inefficient compared with AWR's, and AWR sought its own position on the Cadence IC design platform, via Cadence's Connections program.

    More recently, Ansoft Corp. declared its intention to compete with Agilent in the RF IC design sector with the introduction of Ansoft Designer. Although it had formerly partnered with Agilent on high-frequency structure simulators, Ansoft's design translators and links to the Cadence design environment position Ansoft Designer as more of a head-on competitor to Agilent's Advanced Design System (ADS).

    Ansoft Designer includes a "solver-on-demand" technology that lets users move easily among physics-based electromagnetic models, circuit models, system-level behavioral models and others. (Access to RF and GaAs foundry models has been a coveted Agilent strength.) Ansoft is identified as a Platinum Partner in Cadence's Connections program, which means its tools can be invoked from the Cadence platform.

    The latest challenge comes from startup Xpedion Design Systems, which claims that version 3.1 of its Golden Gate simulation tool, to be shown at DAC, will run circles around Agilent's offering on computationally intensive RF analysis and visualization tasks, such as adjacent channel power ratio and third-order intercept. Roger Bitter, Xpedion's chief technology officer, claims that his tools even deliver faster results than Agilent's on harmonic balance simulation, traditionally an EEsof forte.

    For its part, the Agilent-Cadence team has been adamant that the partnership came at the behest of its customers large players in RF IC design, like Philips Semiconductors, STMicroelectronics and Infineon, that use both Agilent and Cadence Design tools for RF IC development. Such customers had been insisting that the tools be made to work together, said Agilent EEsof marketing manager Charles Plott and Cadence RF platform marketing director Les Spruiell.

    First results

    Agilent's and Cadence's demonstration at DAC will reveal the first results of their joint R&D program. Currently, Cadence's Analog Artist and Agilent's ADS invoke separate simulation and layout flows on the road to final layout and verification. The program looks to create a single design flow for RF ICs.

    In the first phase, Agilent EEsof's display and analysis tools will be brought completely into the Cadence environment. In operation of the platform tools, the user could call forth Cadence Spectre RF (for time-domain representations) and Agilent EEsof's harmonic balance simulator (for frequency-domain simulation) and other Agilent tools from the same Cadence interface. Results of the simulations would be displayed in a Cadence screen window with Agilent's plotters.

    The second-phase incarnations of the tools will incorporate intelligence into the selection of the simulation tool in the RF IC design environment. Instead of selecting a Spice-like circuit simulation or a harmonic-balance simulation, the user would indicate the kind of data desired, and the tools would automatically select and run the appropriate simulator or simulators, said Joe Civello, Agilent's ADS platform manager.

    Troublesome memories

    Some DAC activity will attest to the growing concern that digital CMOS IC designers even memory designers have about analog effects. Nassda (Santa Clara, Calif.) will demonstrate an embedded memory analysis tool, as will Legend Design Technology (Sunnyvale, Calif.).

    While Nassda has always specialized in circuit simulation for large ICs, its Lexsim product is the first EDA tool to model IR drops in nanometer ASICs, claimed product marketing manager Simon Young. IR drops are the voltages dissipated by the interconnect structures that reside between the supply rail and the actual CMOS circuit.

    IR drop is always a problem, but it is especially acute in nanometer circuits (130 nm and below), where IR drops consume a higher proportion of a lower supply voltage, Young said. Thus, an extraordinarily fast tool is required to support post-layout full-chip simulation of embedded memory at the circuit level, he said.

    Nanometer memories are particularly troublesome to characterize, agreed You-Pang Wei, marketing manager at Legend Design Technology, which will release a post-layout memory verification tool dubbed MSim at DAC. Legend, known for expertise in fast circuit simulation, typically uses a parameter matrix (rather than a continuum) to simplify the computational burdens and speed the process.

    But simulation accuracy limits the reduction that can be applied to nanometer structures. With 0.18-micron technology, the simulation could be simplified as a 3 x 3 matrix, simulating "typical," "low" and "fast" memory access values, Wei said. With 0.13-micron technology, the matrix is more like 7 x 7.

    But for 100-nm technology, a 10 x 10 matrix is required to account for all the variations in memory performance. Simulation performance is maintained by parallel processing on multiple Linux machines, Wei said.

    Analog IP hurdles

    As if the DAC product introductions will not provide enough analog concerns, designers can also attend a Tuesday (June 11) afternoon panel devoted to the technology obstacles plaguing the analog intellectual property (IP) business. Because the performance of analog circuits is so bound to the behaviors of devices in specific processes, many believe that the trade of analog IP for use on larger system-on-chip devices can never be made without an entire engineering team's accompanying the transfer.

    The panel will feature assessments from tool vendor Cadence, foundry Taiwan Semiconductor Manufacturing Co., intellectual property marketers Antrim Design Systems Inc. and Nurlogic Design Inc. and their large-company customers Hitachi Ltd. and Infineon Technologies AG.



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