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Designers give Bluetooth more brawn

Posted: 01 Oct 2008 ?? ?Print Version ?Bookmark and Share

Keywords:Bluetooth design? Wi-Fi? wireless application?

Bluetooth has certainly become ubiquitous, and it is the de facto standard for personal area networks. Even though 10 years have passed since the formation of the Bluetooth Special Interest Group (SIG), the technology behind Bluetooth is by no means stagnant, as designers strive for better performance, lower power consumption, increased range, and decreased size and costs. Companies such as CSR, STMicroelectronics, Marvell and Broadcom continue to release new Bluetooth ICs to address different market segments and applications, even as they churn out existing devices in high volumes.

Developments in high-speed Bluetooth (using Wi-Fi and/or UWB technology) and Bluetooth low energy (previously known as ultralow-power Bluetooth and Wibree) also keep Bluetooth IC designers going back to the drawing board.

High-speed Bluetooth will let consumers transfer large data files such as music, video and photos between devices within a short range. The specification is expected in mid-2009.

New specification in '09
Bluetooth low energy will let Bluetooth devices use small button batteries, enabling scenarios in which devices such as watches could be used to control music players. The Bluetooth SIG expects to announce its first version of the Bluetooth low-energy specification at the end of this year with consumer products appearing in 2009.

Today's available Bluetooth ICs run the gamut from the basic Bluetooth 2.0 with enhanced-data-rate radio to integrated devices and modules that can include FM radio, DSP, enhanced GPS (eGPS) and Bluetooth low energy. Designers can take different approaches to adding on-chip functionality for Bluetooth ICs.

BlueCore7 touts the Bluetooth ver 2.1 + EDR and low-energy standard.

Sameer Bidichandani, senior director of technology strategy at Marvell Semiconductor, said his company takes an intellectual-property (IP) mix-and-match approach. "We have a very rich road map based on multiple radio IP blocks that we put together in single-die or single-package solutions," he added.

Complete set
According to Matthew Phillips, senior VP of CSR's mobile handset connectivity strategic business unit, all of CSR's BlueCore chips start with Bluetooth and variously include FM receive, FM transmit, eGPS, DSP and Bluetooth low energy.

CSR's BlueCore7 offers all of these in a single chip. The on-chip DSP supports custom signal processing, and the company has teamed up with more than 30 third-party code developers.

The company also offers MusiCore1, a single-chip, Bluetooth-equipped MP3 player designed for mobile phones. Phillips said the chip supports more than 100 hours of playback on a standard battery.

Steve Beckers, marketing director for the connectivity group at ST, said his company is in volume production with its fifth-generation standalone radio (the STLC2500D) and a third-generation Bluetooth-FM combo (the STLC2593). ST is also sampling a fourth-generation Bluetooth/FM combination chip (the STLC2690), manufactured using 65nm technology.

What are the specifications to consider when selecting a Bluetooth IC? Power consumption is essential, especially as functionality is added to the Bluetooth IC. "For example, if a phone is used for listening to music but decodes MP3 via the host processor, this will lead to significant power drain," Phillips explained. "It is vital to anticipate accurately what features a device will require to make the most efficient use of the cost, space and power available," he added.

By mixing Bluetooth functionality with an FM transceiver in a single 65nm chip, ST aims to offer leading-edge integration and performance with its STLC2690.

Silicon die size and the total solution footprint are also crucial, because they relate to the available board space as well as the total solution cost. Bidichandani stressed the importance of integration in Bluetooth ICs, saying that bringing more external components on-chip leads to a more optimal design for cost, time-to-market and industrial design of the final product.

Output power range and receive radio sensitivity are also essential as both relate to power drain. It is also important for the Bluetooth IC to address coexistence with other radios. Interference could affect data rates and might require signal strength boost, reducing battery life. When optimal, these factors lead to a more robust design that can deliver a competitive advantage by supporting a better experience for the end user.

Active development
Designers of Bluetooth ICs are not in a holding pattern waiting for the next specification. Most of them are actively involved in development based on what is known of the new high-speed and low-energy specifications, but many Bluetooth IC designers also seem to be working on other innovations.

CSR, for instance, sees the importance of integrating complementary wireless interface standards into the device. "This provides added value to our customers," Phillips said. The company has announced to work on UWB, 802.11n and NFC for Bluetooth.

According to Beckers, ST's next-generation Bluetooth development (after 65nm) will be to drive integration in "connectivity combo" devices and to embed the baseband.

Despite its market leadership, Bluetooth still gets some competition from proprietary standards that target issues of power, cost and interference. These devices are hampered, however, by a lack of interoperability with other products. By contrast, the more than 10,000 members of the Bluetooth SIG put a significant amount of market muscle behind the standard. At present, the collective might is giving heft to the two emerging Bluetooth specifications: high-speed and low energy.

- Janine Love
EE Times

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