Ansoft jumps into RF IC modeling

Stephan Ohr

February 16, 2004

Stephan Ohr

San Francisco — Ansoft Corp. will introduce a circuit simulator this week designed to compete with HSpice and SpectraRF in time-domain analysis of high-frequency circuits, and with Agilent EEsof tools in frequency-domain analysis. Ansoft's Nexxim serves as both a circuit simulator for time-domain analysis and as a harmonic balance simulator for the frequency domain, the company said.

Ansoft said it intends to position Nexxim as the simulator of choice for analysis of RF and high-frequency wireline circuits. The circuit simulator will compete against the offerings of Cadence Design Systems Inc. and Agilent Technologies Inc., which have formed an alliance to develop an RF and mixed-signal IC design flow. The company is aiming Nexxim specifically at new RF IC designs developed by designers who in the past may have used the Cadence platform with Agilent EEsof links and add-ons.

While Ansoft is best known as an electromagnetics company, Nexxim "positions us front and center in the Spice circuit simulator business," said Lawrence Williams, director of marketing at Ansoft (www.ansoft.com). "HSpice compatibility enables Ansoft to fit into the silicon builder's design flow."

Nexxim targets a flaw in the Cadence-Agilent design flow, said Prem Premkumar, vice president for product development at Ansoft. While Cadence's SpectreRF simulator provides Spice-like time-domain analysis and Agilent's ADS provides harmonic balance simulation, the simulators rely on different models, and correlating the simulation results can be difficult, Premkumar said. Nexxim's numerical algorithms allow two simulations to be launched from the same HSpice netlist-one for time domain, another for frequency domain-with the results correlated, he said.

Ansoft also hopes to excel on run-time and capacity issues, Premkumar said. "There are shifts that make people want to look for a change," Prem said. "The Cadence-Agilent platform would be adequate-if the world stood still," he said.

"We started as a 'tech boutique,' " Premkumar said. "Now we're definitely competing."

But going against the Cadence-Agilent hegemony may be a tall order. Those companies' Unix-based tools have an extremely large installed base, especially among developers of RF ICs. From its inception two years ago, the Cadence-Agilent alliance carried endorsements from players like Motorola's Semiconductor Products Sector, Philips Semiconductors and STMicroelectronics. The Ansoft product carries no endorsements at this point.

Ansoft cited five customer benchmarks-a 1.8-GHz phase-locked loop in 0.25-micron CMOS with over 2,000 BSIM3 transistors; an RF/analog front end for a Bluetooth BiCMOS system-on-chip design with over 4,000 active devices; a DRAM cell with over 13,000 BSIM3 transistors; an RF mixer analyzed with more than 1,000 harmonics; and a 3-Gbit/second A/D converter in a 0.35-micron GaAs process, but no run-times were provided. Marketer Williams said that semiconductor builders are currently using the Nexxim product, but he admitted that, so far, they have declined to be named.

The Nexxim product links with Ansoft Designer to support co-simulation with system and planar EM solvers like HFSS-the 3-D electromagnetic solver-and Q3D Extractor, Ansoft's parasitic extractor. In addition to providing time- and frequency-domain circuit simulation with consistent results across both analysis domains, Nexxim provides simulation accuracy and transistor-level detail without model approximations.

Ansoft will release Nexxim in the second quarter. It will support Linux, Windows 2000 and Windows XP. The list price is $79,900 for a perpetual license.