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W-CDMA gets a boost from dual-band power amplifier module

Posted: 12 May 2005 ?? ?Print Version ?Bookmark and Share

Keywords:fairchild semiconductor? w-cdma power amplifier? power amplifier? rmpa2265? pa module?

Keeping up with changing and evolving specifications and minimizing design cycles are common challenges for RF and wireless design engineers. In response, Fairchild Semiconductor has raised the bar on functionality and size for W-CDMA power amplifiers with its RMPA2265 PA module.

"This is one of the first dual-band W-CDMA PAs that offers a 3-by-3mm footprint," observes Sanjiv Shah, director of marketing for the RF Group at Fairchild. With an eye to the international market, the team designed the product to satisfy both UMTS bands, Band 1 (which is primarily used in Europe) 1,920MHz to 1,980MHz, and Band 2 1,850MHz to 1,910MHz. "With this approach, manufacturers can design a generic phone board for either market, reduce design time, and minimize inventory," he adds.

Also keeping an eye on the future, the team ensured that the PA was also compliant with the emerging High-Speed Downlink Packet Access (HSDPA) standard, which supports data up to 10Mbits/s rates. The product is already rolling out of manufacturing as in being used in W-CDMA UMTS wireless terminals and handsets, and will not require a hardware change to the handset when a network goes HSPDA compliant.

The RF Group has a track record with front end designs for W-CDMA, CDMA, and more recently, GSM and EDGE. Part of the Raytheon RF components group until October 2003, the group at Fairchild is also working on products for WLAN a/b/g, as well as emerging Wibro and WiMAX standards.

Design Concerns Long battery life and long talk time are high priorities in the W-CDMA handset market, and to achieve this, the PA needs to provide high power added efficiency. The new PA is a third-generation product, and engineers at Fairchild have boosted efficiency from 35% to 42% with this latest design. How did they achieve that? Of course, the team credits engineering expertise, but they have also employed an InGaP/GaAs HBT process, which offers inherently good linearity. "To get higher PAE, you need to trade off linearity," Shah explains, "so, by using this process we were able to get the PAE we were targeting while still maintaining the linearity required to hit the higher data rates of HSPDA."

Limited board space is another issue for designers of W-CDMA handsets, so the team focused on reducing footprint. Earlier generations featured footprints of 6-by-6mm, then 4-by-4mm, and then 3-by-3mm. How did they do this? Shah explains that the company works on products in families, and by developing a process to shrink the size of one product, it effectively translates to shrink the other products in the line.

Certainly one of the most compelling features of this product is its dual-band functionality. And, it actually exists, with production volumes shipping to European manufacturers right now. An evaluation board is available, and the company provides application support to help with circuit tuning.

The RMPA2265 is priced at 98 cents each in 1,000-piece quantities. It is available now with delivery in 6 to 8 weeks.

- Janine Love


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