While many available Bluetooth chip sets support a variety of system architectures, Motorola's Bluetooth solution is narrowly focused on the link between mobile handsets and wireless headsets. As such, the RF front-end and baseband of the set have been optimized to the specific needs of the link.

Audio quality is a key concern for a mobile phone/headset link. Most available Bluetooth chip sets have been engineered to transmit data, so designers must add echo cancellation features to handle audio transmissions. Recognizing this difficulty, Motorola built audio signal processing circuitry into its baseband architecture.

The chip set eliminates the need for an echo canceller and avoids the switching delays that can increase noise and pesky clicking an end user hears with other chip sets, said Gary Montgomery, director of marketing for Motorola's Wireless Local Connectivity Division.

The RF transceiver has also been optimized for handset/headset links, Motorola said. For starters, it can share the clock of the mobile phone. The chip set sports a fractional synthesizer that operates from 10 MHz to 26 MHz, allowing the transceiver to hook into a variety of clocks, Montgomery said. By offering this functionality, the chip set won't be limited to only GSM or CDMA operation, but can support a variety of mobile phone architectures, including those with a host of RF front-ends.

Peaceful coexistence

Motorola has also tackled the coexistence problems that have become a nagging headache for designers when 802.11b wireless LANs and Bluetooth architectures are in close proximity. These difficulties are expected to rise as deployment of these wireless solutions rises in 2002.

Motorola has addressed the issue in two ways. First, it has implemented an adaptive scheme that allows the chip set to intelligently hop around channels to avoid interference. Other chip makers have followed this course. Second, it has added joint detection and maximum likelihood sequence estimation (MLSE) techniques to the RF front-end to increase sensitivity, which in turn increases interference to noise.

These technologies allow Motorola's chip set to determine the likely centerpoint of a signal as it is being received. Then the RF front-end can operate in a narrow range around that centerpoint, thus limiting such pesky RF factors as co-channel and adjacent channel interference, the company said.

These techniques help deliver a Bluetooth transceiver with a sensitivity of -84 dBm, which is 14 dB better than the -70-dBm sensitivity spec set by the Bluetooth standard, Montgomery said.

Increased range is a side benefits of the increased sensitivity. The transceiver can achieve a range of approximately 120 meters, a fourfold improvement over the Bluetooth spec, Montgomery said.

The chip set includes the MC71000 ARM7-based baseband processor equipped with a Bluetooth-compliant host controller interface, the MC13180 RF BiCMOS transceiver, the MRFIC2408 power amplifier, and Digianswer software. The power management chip can reduce power consumption in mobile and non-mobile systems, Motorola said.

Motorola has working silicon of the chip set and will sample it with development kits in the first quarter of 2002. Production is planned for the second quarter. The chip set will carry a suggested list price of $5.90 each in million-unit volumes.

Robert Keenan is editor-in-chief of CommsDesign.com, an online sister publication of EE Times.