Intersil, CSR spin Bluetooth/802.11b reference design

Intersil, CSR spin Bluetooth/802.11b reference design
San Jose, Calif. — Intersil is partnering with Cambridge Silicon Radio (CSR) and Smart Modular Technologies to send a mini-PCI board to market that combines 802.11b wireless LAN (WLAN) and Bluetooth technology.

Intersil is no stranger to working with Bluetooth chipset developers on joint reference platforms. In April of this year, the well-known WLAN chipset maker sent a joint 802.11b/Bluetooth mini-PCI reference design to market that combined Intersil's Prism 3 chip set with a two-piece Bluetooth chipset from Silicon Wave. (See Intersil, Silicon Wave sample combo Bluetooth/WLAN solution).

At this week's Bluetooth Developer's Conference here, Intersil and CSR will unveil a similar offering. The CSR/Intersil reference card includes the Prism 3 chipset, which includes a direct-conversion radio and a baseband/MAC IC. It also houses CSR's BlueCore2 IC, which integrates both the Bluetooth RF and baseband functionality on the same piece of silicon.

Essentially, the new reference platform is a two-system solution, said David McCall, senior applications engineer at CSR. Unlike other companies trying to deliver highly integrated Bluetooth/802.11b radios, such as Mobilian, Intersil and Silicon Wave opted to combined their individual radios on a card and use software to exchange information between them. According to McCall, signaling is provided between the Prism 3 chipset and the Bluetooth baseband to inform each radio of who's working and who needs to back off. Additionally, signaling is provided from the host PC to the BlueCore2 radio, informing BlueCore2 what channel Prism 3 is running on.

The exchange of channel information is an essential ingredient in ensuring co-existence in the Intersil/CSR reference. CSR's BlueCore2 chip is equipped with a channel skipping technology that allows it to avoid operating on particular channels, McCall said. Using the operating channel information received from the host system, the BlueCore radio can then avoid operating on the WLAN channel, McCall added.

As McCall points out, the drawback with the channel spacing approach is a small reduction in Bluetooth bandwidth. "We take a small hit on Bluetooth bandwidth to avoid a big hit on 802.11b bandwidth," McCall said.

To illustrate the hit taken, McCall pointed to a card implementing Bluetooth and WLAN radios without employing channel skipping. In this scenario and a worst-case operating condition, the WLAN radio would operate at 10% of its bandwidth while the Bluetooth radio would operate at 70 to 80% of its bandwidth. When channel skipping is turned, however, McCall said the WLAN radio will operate at 80 percent of its bandwidth while the Bluetooth radio would operate at 50 to 60 percent of its bandwidth in a worst-case scenario.

The reference design will achieve a Bluetooth receive sensitivity of better than -82 dBm and a typical output power of +2 dBm. The card's 802.11b radio, on the other hand, will sport a receive sensitivity of better than -85 dBm and a typical +16 dBm output power.

Smart Modular will be responsible for making mini-PCI cards housing the reference design. Samples of these cards are expected in January 2003.