Wireless Systems Design

Two-Chip WLAN Solution Operates at 54 Mbps

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The industry is unsure whether IEEE 802.11g is just a transitional technology on the way to 802.11a or a wireless-local-area-networking solution in its own right. Intersil, however, is betting on 802.11g for its backward compatibility with existing 802.11b Wi-Fi systems, as well as its potential for high throughput. The company's PRISM GT is a two-chip WLAN solution. It was designed to support the 802.11g high-rate Draft Standard for Wireless Local Area Networking (WLAN) products operating in the 2.4-GHz band.

Notably, PRISM GT promises to provide twice the range and throughput for currently marketed 802.11a products, and over three times the throughput of 802.11b+ products. To attain this level of performance, the company combined the 802.11g Draft Standard's mandatory modulation schemes—the Complementary Code Keying (CCK) used in 802.11b and the Orthogonal Frequency Division Multiplexing (OFDM) used in 802.11a—with its proven, low-cost ZIF architecture. These technologies enable wireless-networking systems to attain data transmission speeds of up to 54 Mbps. In addition, CCK ensures backward-compatibility with the installed Wi-Fi base, while OFDM provides the speed required for today's high-bandwidth applications.

PRISM GT hopes to enable a new generation of high-data-rate platforms. Operating in the 2.4-GHz spectrum, these platforms could deliver a threefold increase in throughput over currently marketed 802.11b+ solutions. Compared to systems operating in the 5-GHz spectrum, it also boasts lower power consumption.

The PRISM GT solution uses Intersil's direct-downconversion architecture that was developed for the PRISM 3 chip set. It also relies on the digital-signal-processing knowledge gained by the company in the development of 5-GHz 802.11a products. The transceiver integrates the receiver, transmitter, synthesizer, and filters onto a single chip. It interfaces directly with the baseband processor to provide system designers with a complete end-to-end WLAN chip-set solution. The medium access controller (MAC) includes enhanced security and network-management features.

Being an RF-to-baseband solution, the PRISM GT transceiver takes high-frequency radio waves and directly converts them to baseband signals during reception. Or, it directly upconverts them from the low-level baseband signal to radio frequency during transmission. This architecture eliminates the need for the intermediate-frequency (IF) stage found in most radios, thereby reducing complexity, bill-of-materials (BOM), and manufacturing costs. At the same time, it effectively enables the smaller form factors appropriate for portable handheld devices.

Intersil's turnkey-solutions approach will include mini-PCI and CardBus32 PC-card reference designs. The reference design kit includes: the PRISM GT chip set; complete schematics; Gerber and layout files; a bill of materials; manufacturing test utilities; PRISM lab test diagnostic tools; FAB drawings (printed-circuit board); antenna-construction details; and a technology license agreement. Manufacturing, mechanical, and assembly drawings also are provided.

Intersil Corp.
7585 Irvine Center Dr., Suite 100, Irvine, CA 92618; (949) 341-7000, FAX: (949) 341-7123, www.intersil.com.

TAGS: Intersil
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