June 17, 1998 SAN FRANCISCO -- Lucent Technologies researchers have developed powerful new software tools that promise to speed the design of radio frequency (RF) integrated circuits used in wireless phones and base stations.
Currently, it takes four or more design iterations to develop manufacturable RF chips within the industry, and each iteration requires two to three months. Using the new software tools, which are in an advanced development stage at Lucent's Bell Labs, researchers should be able to produce manufacturable RF chips on the first attempt.
"Reducing both time to market and design costs are very important in this highly competitive and exploding wireless electronics market," said electrical engineer Al Dunlop of Bell Labs, who presented his research findings here today (June 17) at the 35th Design Automation Conference.
Evaluating RF chip designs is much more difficult than analyzing the design of digital chips, like those used in computers. While the output of transistors in digital circuits is either zero or one - represented by two distinct voltages - the output in RF circuits is a continuum of voltages, resembling a wave. This wave, or frequency, must be pure to produce the desired result, such as 900 megahertz for cellular phones.
The Bell Labs-prototype software tools are unique because they can evaluate the design of the entire RF chip, which typically has a few hundred to a few thousand transistors, intermingled with capacitors, conductors and insulators. Other software packages for evaluating the design of RF chips, meanwhile, evaluate either chip components or small portions of chips.
"Our new approach is very similar to a conductor leading an orchestra," Dunlop said. "The conductor wants each section to complement each other. It would be pretty awful for the strings to be flat, compared to the brass section, which might be the situation with the old approach."
The wide range of voltages in RF circuits presents only one of several challenges when verifying the design of RF circuits. The other major problems involve distortion, noise and interference. These factors, which affect only RF circuits and not digital circuits, significantly boost the amount of electrical information that must be evaluated.
"Whereas a digital circuit resembles a lake that's empty or full," Dunlop said, "a RF circuit is more similar to the lake's waves. We need to know about the waves' shape, size and frequency."
Besides studying the interference problem, the Lucent software tools predict energy levels for each frequency and also simplify the models without sacrificing accuracy. The trick in developing the software, Dunlop said, was creating different formulations for simulating and analyzing the design of chips. These formulations, he said, were more amenable to today's computing techniques.
"Designing a RF chip always has been more of an art than a science because a chip's performance is very unpredictable," Dunlop said. "We're hoping that this new approach will turn the design of RF chips into more of a science."
Other Bell Labs researchers involved in the research project are Alper Demir, Peter Feldmann, Sharad Kapur, David Long, Robert Melville and Jaigeet Roychowdhury.
The Design Automation Conference was sponsored by the Institute of Electrical and Electronics Engineers, Association for Computing Machinery and Electronic Design Automation Consortium.
Lucent Technologies, headquartered in Murray Hill, N.J., designs, builds and delivers a wide range of public and private networks, communications systems and software, data networking systems, business telephone systems and microelectronic components. For more information on Lucent Technologies, visit the company's web site at http://www.lucent.com.
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