Sales of GaAs ICs for WLAN applications grew by 140% in 2003 according to one estimate. Tim Whitaker talks to the major players in what is fast becoming a key market for compound semiconductors.

Providing broadband access in offices and public places such as airports and coffee shops, wireless local-area network (WLAN) products are among the fastest-growing segments of the RF communications market. With data rates in the 11-54 Mbit/s range, WLANs utilize the 2.4 and 5 GHz bands and are creating strong demand for GaAs power amplifiers (PAs) and switches. Among the early leaders in the WLAN GaAs PA market are Anadigics, Microsemi and Fairchild Semiconductor (previously Raytheon s RF Components division), while the leading manufacturers of PAs for cell phones, RFMD and Skyworks, are also beginning to address the WLAN market. Ron Michels, VP of broadband products at Anadigics, describes the WLAN market as a natural extension for RF communication products. "The market is growing leaps and bounds, unlike other markets served by Anadigics such as cell phones and cable TV," he said. Confirming this assertion, Strategy Analytics has estimated that sales of GaAs ICs in the WLAN market grew by about 140% in 2003, and that a compound annual average growth rate of 21% will be experienced through 2008. Furthermore, the market research firm says that 67% of the 177 million PAs shipped in 2008 will be manufactured using GaAs, while all WLAN switch ICs will use GaAs technology. After acquiring fabless WLAN module and PA supplier RF Solutions in April 2003, Anadigics had shipped 1 million PAs by early July, and later reported that its WLAN revenues grew by 47% sequentially in the third quarter of 2003. "We expect our growth to be similar to that seen in the overall market, and that we will continue to significantly increase share next year," said Marcus Wise, senior product line director for WLAN at Anadigics. The company is involved with a new Intel design for the WLAN market, and is also included in a number of other reference designs with tier-1 chipset providers. Meanwhile, Erich Volk, marketing manager for RFIC products at Microsemi, says that in November 2003 his company reached a run-rate of 1 million units per month for PAs supplied to the WLAN market. "We continue to see demand soaring," said Volk. Atheros, one of the leading WLAN chipset manufacturers, has included Microsemi s InGaP HBT PAs in all of its current reference designs. "50% growth through 2006"Further proof of the strength of the WLAN market comes from RFMD, whose VP of wireless products, Eric Creviston, said: "With overall unit growth forecast to be about 50% through 2006, we estimate this market will become larger than our core market today in mobile handsets." Another boon for GaAs IC manufacturers is that demand in this particular market is set to increase as WLAN standards evolve. The current trend in the market is a migration from IEEE 802.11b, which provides a data rate of 11 Mbit/s in the 2.4 GHz band, towards the 54 Mbit/s 802.11g standard (see table). However, the 2.4 GHz band has a small number of available channels and suffers from crowding and interference. A further standard, 802.11a, addresses a much less crowded band at around 5 GHz. (In fact, there are a number of frequencies in use around the world between 4.9 and 5.9 GHz.) The next trend in the market will be the emergence of dual-band a/g devices; this is expected to gain momentum towards the end of 2004. Strategy Analytics estimates that by 2008, a/g combo devices will account for more than 75% of shipped products. These require a PA for each frequency band, together with a switch that is usually implemented in GaAs PHEMT technology. Although there are several silicon-only products available, particularly for the 802.11b standard, the need for GaAs increases as standards evolve. "As the market moves from b to g and then to dual-band [g/a], the performance advantages inherent in GaAs overwhelm what can be done with SiGe," said Michels. Anadigics, Fairchild, Microsemi and RFMD are all using GaAs HBT technology to manufacture PAs for the WLAN market. RFMD sells complete CMOS chipsets for WLAN, although these are designed to be used in conjunction with the company s GaAs PAs. As usual, silicon is not standing still. In September 2003, one of the WLAN market leaders, Broadcom, announced the first single-chip all-CMOS 802.11b transceiver, with all components including the PA integrated onto a single silicon die. Earlier in the year, SiGe Semiconductor reported that its SiGe PA had been integrated into some of Broadcom s reference designs for 802.11g products. Silicon will undoubtedly retain a foothold in segments of the WLAN market that do not require the high performance provided by GaAs. In short-range, low-power applications such as those using hand-held devices like PDAs, integrated silicon solutions are likely to dominate. However, in longer-range applications with a high density of users, the power and performance requirements point to GaAs. "For 1-6 GHz, GaAs HBT is ideal in terms of high-frequency performance, efficiency and linearity," said Michael Kim, general manager of Microsemi s WLAN research and development team. "There is also an advantage in terms of manufacturability compared with SiGe, which can only achieve high speed using sub-0.5 µm lithography." In contrast, Microsemi uses 2 µm HBT process technology. Although the company has an internal 4 inch GaAs fab, it is using external foundries to manufacture its WLAN PAs. "The volume is not there yet, so we prefer to share costs through external foundries with 6 inch capability - there are several in Taiwan and one in Korea," explained Kim. "Our internal capability provides emergency back-up and allows us to look at engineering issues." IntegrationAccording to Kris Rausch, director of WLAN products at RFMD, there will be a trend towards integration following a similar path taken in the cell-phone market. "Two years ago we were selling stand-alone [PA] MMICs with external matching; now we re selling parts with 50 Ω matching integrated within the packaging," he said. "The next stage will be to include switches and filters in the module." The need for integration depends on where the product will be implemented. Kim says that the majority of Microsemi s PAs go to Taiwanese OEMs that make after-market WLAN cards to plug into PCs, or small-form-factor devices that are included inside higher-end notebooks. "In these form factors there s enough space to favor discrete implementations, and cost is a major issue, so there is no big push for integration," he explained. However, the development of much smaller form factors will drive the move to dual-band PAs in a single package and then on to integrated front-end modules. Anadigics is taking the same route. "We are in the process of integrating switches into front-end modules," said Wise. "Our integration level will increase drastically over the next year." Integrating more functionality helps to offset the trend of falling average selling prices (ASPs) for PAs and chipsets, which is very significant in the 802.11b market, and less so in the 802.11g segment. In fact, according to Wise, average ASPs are likely to increase slightly as a and a/g devices are introduced and the product mix changes.