'System on a chip' stars at ISSCC

Electronic News, Feb 19, 1996 by Cindi Maciolek

San Francisco--The 43rd IEEE International Solid State Circuits Conference (ISSCC) held in San Francisco last week drew the highest attendance in nearly 10 years. Edging near the 3,000 attendee mark, almost 160 papers were presented in concurrent sessions during the three-day conference, according to program chair Frank Hewlett of Sandia National Labs, Albuquerque.

The theme of "System-on-a-Chip" was particularly evident in the sessions on communications chip developments.

The session on communications building blocks was headed by William J. Ooms, manager of Motorola's corporate research labs in Tempe, Ariz. Mr. Ooms described the session as "addressing different parts of the radio, from receiver to transmitter, all at a higher level of integration.

"More portions of a radio are now being put on an IC. In addition, the increased attendance in communications sessions reflects an increased interest in the communications industry as a whole. IC design is no longer just microprocessors and memories," he noted.

Two papers in the session were presented by AT&T Bell Labs: a 1.5V 900MHz downconversion mixer, and a 2.7V 900MHz CMOS LNA and mixer. The first design is aimed at wireless transceivers, to reduce the number of batteries required for portable devices. It uses capacitive regeneration to relax the noise-distortion tradeoffs and is fabricated in a 20GHz BiCMOS process.

The second design is a prototype for 900MHz applications, implemented in a 0.5-micron CMOS process, and aimed at the North American Digital Cellular System. It has 10 mA consumption at 2.7 volts. The design strategy of current reuse reduces power dissipation in this design while increasing amplifier transconductance, AT&T said.

Philips Research offered its own entry in the cellular phone market with a paper on a 1W 830MHz monolithic BiCMOS power amplifier. This new design also offers high efficiency to reduce power dissipation, with a 30 percent increase in power efficiency. It's aimed at the American Mobile Phone System (AMPS). The 0.8-micron BiCMOS Qubic chip hasn't gone into production yet.

Rockwell's presentation focused on an 81MHz infrared frequency (IF) receiver in 0.8-micron CMOS. It uses a single 3V power supply and consumes 14.4 mA, with a channel bandwidth of 200KHz. The design includes an open loop IF amplifier, a subsampling mixer and a sixth-order sigma-delta A/D converter. By implementing this design in CMOS, the IF receiver can be integrated with the baseband processor.

Two papers in the session on high speed communications drew a lot of interest. Francesco Piazza, a PhD student at Integrated Systems Laboratory in Zurich, Switzerland, described a 12 mA triple-conversion receiver for GPS for the civilian L1 band. The design is being done for ASULAB in Switzerland. The triple-conversion architecture minimizes the number of components operating at high frequency to reduce power consumption, and the design complexity is reduced.

The current design is two chips, but the final version is expected to be a single chip. It is currently in prototype, with the first commercial product expected in about a year. Ultimately, it will offer wristwatch navigation capability. The chipset is implemented in a 1.0-micron BiCMOS process, with a supply voltage of 2.4-3.5V.

Anadigics in Warren, N.J., offered its take on a wide dynamic range GaAs broadcast satellite tuner IC. The chip operates at 950MHz to 2150MHz radio frequency (RF), with an IF frequency of 480MHz, and a set-top box which can receive as many as 50 channels. It operates on a 5V power supply.

Just a mere 37-mm squared, the GaAs chip was designed to be small to compete with discrete devices in both cost and performance. The chip is currently in production for select customers. Originally intended for Europe, it is expected to find its way into U.S. products as well.

The session on wireless systems offered a selection of papers which purported to show higher levels of integration and improvements in performance of wireless communications. However, consultant Russell Apfel, who chaired the session, said he felt that "There hasn't been any new, significant functionality in the designs. A reasonable number of components are still external.

"I don't expect to see any major changes for the next year or two. The biggest question is still gallium arsenide versus silicon. There's big growth in the use of silicon, but GaAs is still good in the areas of power amplifiers and switchers. We'll have to monitor the trends to see how it goes," he added.

Mitsubishi presented a two-chip chipset primed for the Japanese personal handyphone system (PHS) which uses an L-band. However, after release to a few select customers in June, Mitsubishi expects to offer the chipset worldwide for inclusion in cellular telephone designs.

The company plans to do some modifications of the chipset, depending on local requirements. The GaAs RF transceiver IC for a 1.9 GHz digital mobile communication system, is paired with a 1.9 GHz single chip IF transceiver fabricated in a 0.8-micron BiCMOS process.