Conexant Streamlines Mobile Handset Design With A Cost-Cutting Direct Conversion Transceiver Solution For Next-Generation GSM Platforms
Conexant Systems Inc. today announced a new single-chip radio frequency (RF) transceiver that streamlines the design of multi-band global standard for mobile communications (GSM) handsets. By eliminating costly intermediate-frequency conversion steps, Conexant's CX74017 advanced direct-conversion transceiver cuts the number of external components required to build a mobile handset by one-third, significantly reducing the cost, size and power requirements of next-generation GSM handsets. Proprietary design techniques employed in the receiver also enable the device to be used with any commonly available GSM baseband IC, which will shorten handset development cycles.
Conexant's CX74017 transceiver supports general packet radio service (GPRS) and downlink-enhanced data rates for global evolution (EDGE) standards, and provides a well-defined roadmap to dual-mode, wide-band code division multiple access (W-CDMA)/GSM universal mobile telecommunications (UMTS) handsets. These handsets will support such advanced applications as multimedia and high-speed web browsing.
"Dual-band GSM radios using conventional solutions require around 100 external components. The same radio requires only 65 with Conexant's CX74017, providing customers with a compact design platform for creating smaller phones, wireless PDAs and other advanced terminals that can also include such functions as Bluetooth connectivity, digital imaging and MP3 audio," said Moiz Beguwala, senior vice president and general manager for Conexant's Wireless Communications Division. "Plus, we've eliminated the need for baseband processing support so that this device can be cost-effectively combined with virtually any baseband solution on the market."
According to the market research firm The Strategis Group, revenue from wireless data is expected to reach $33.5 billion globally by 2004. The firm also predicts that there will be one billion wireless subscribers worldwide on third-generation (3G) networks by the year 2010. Cahners In-Stat Group anticipates that the worldwide penetration of all wireless service will grow from 7.5 percent today to more than 32 percent during this decade on a global basis.
Technical Details
The CX74017 transceiver uses several new techniques-for which patents are pending-to solve many of the problems previously associated with the implementation of direct-conversion technology, which has long promised the ideal solution for today's GSM handsets and next-generation terminals, including 2.5-generation (2.5G), GPRS and 3G terminals.
Direct conversion eliminates all of the intermediate frequency (IF) signal conversions that are required with the more commonly used superheterodyne technique, along with the costly discrete components that are associated with the extra signal-conversion step. Until now, direct-conversion solutions have required a significant level of digital signal processing (DSP) support from the handset's baseband circuitry, and have generally provided poorer performance than the more common superheterodyne receivers. In contrast, Conexant's implementation removes the baseband-processing burdens of earlier approaches to provide superheterodyne-like performance in a dual- or tri-band solution, while offering the flexibility to be combined with any of a variety of readily available digital baseband processor chipsets.
The CX74017 transceiver consists of integrated low-noise amplifiers (LNAs), a quadrature demodulator, baseband filters and a direct current (DC) offset correction sequencer. It uses a low-frequency, low-pass filter to perform all of the required tasks associated with rejecting in-band blocking signals and adjacent alternate channels. This contrasts with superheterodyne architectures that first convert the RF signal to an IF signal using one external surface acoustic wave (SAW) filter. One SAW filter is used for each of the bands supported in a multi-band handset, to reject the image frequency at RF. Then, the IF signal is converted to a baseband signal using a second local oscillator and external voltage controlled oscillator (VCO). Because Conexant's proprietary technology eliminates the IF conversion stage, all of the filtering for each of the bands can be performed inexpensively, on chip.
Other CX74017 features include a translational loop structure on the transmitter side, consisting of an in-phase and quadrature (I/Q) modulator, offset mixer, phase detector and transmit VCO with no external tank. The transmitter offers exceptionally high performance, thus also reducing the number of external components required. The local oscillator structure is formed around a fractional-N phase lock loop (PLL) with all components integrated, save for the external passive loop filter. Agile channel switching allows support of GPRS multi-slot operation, and key performance parameters are optimized through the use of Conexant's internally developed, low-cost RF packaging technology.
Conexant, 4311 Jamboree Rd., Newport Beach, CA 92660. Tel: 949-483-4600; Fax: 949-483-4078.