Nokia teams up in CDMA

Although Nokia is the undisputed leader of the handset market, with roughly 30 percent of global sales, its dominance has not historically carried over into code-division multiple-access protocol subscriber terminals. To improve its flagging CDMA sales, the company began a push in late 2002 starting with the launch of the 3585. Nokia's series of entry-level cdma2000 terminals utilized a fresh approach to chip design-and one that notably sidestepped Qualcomm.

The Nokia 6225 is a second-generation cdma2000 design of the same lineage, with internally developed semiconductors designed to cut an independent path. With the bigger picture in mind, Nokia, along with its chip set suppliers, began an effort to break Qualcomm's stranglehold on the CDMA marketplace.

With Texas Instruments focusing on the digital baseband and STMicroelectronics responsible for analog ASICs and key transceiver devices, the logic was clear: By opening up the chip set to other OEMs, economies of scale could emerge, and the industry as a whole would enjoy a more competitive (and thus lower-cost) solution for cdma2000 hardware.

Nokia's 6225 handset offers the usual features, including a color LCD, polyphonic ring tones, Java games, camera, voice dialing, voice memos, speakerphone, Short Message Service, Multimedia Messaging Service and 500-name/number contact capacity. An FM radio was added for fun.

Based on a candy bar format for ease of final assembly, the design also relies on an internal antenna, eliminating the more-traditional whip antenna of CDMA designs. An assisted global-positioning system for E911 compliance is offered in the design, albeit with a much more traditional approach than Qualcomm's hybrid terrestrial/satellite gpsOne location technology. Two components from TI are used to implement the global-positioning system, splitting duties between a GPS baseband device (F75190) and a GPS receiver (TRF5101). Only an external temperature-controlled crystal oscillator, a pair of filters and supporting discretes are needed to combine with the two chips for location awareness.

Radios based on CDMA are trickier to design than GSM systems, and component complexity in the 6225 RF section reflects this fact. Because cdma2000 is a frequency-division multiple-access protocol requiring simultaneous activity in transmit and receive, higher radio component count is seen on several fronts.

To deal with uplink/downlink isolation, separate chips from ST implement Rx/Tx processor functions. Similarly, separate surface-acoustic-wave frequency duplexers are responsible for splitting the transmit and receive portions for each of the two operating bands of the 6225 design.

Following the ST transmit processor are a pair of transmit drivers from RF Micro Devices (RF2356 and RF2357), which feed RFMD PA modules. Characteristic of many CDMA designs, the 6225 also uses a pair of RF isolators to absorb any radio backwash resulting from antenna mismatches.

Back on the receive end, a front-end, low-noise amplifier/mixer from TriQuint Semiconductor (ACO520) is responsible for boosting incoming signals and providing first-stage downconversion before handoff to the ST receive processor.

But perhaps the biggest story lies in the baseband processor, where protocol signal processing takes place. Based on other Nokia handset teardowns performed by Portelligent, we find that the baseband processor in the 6225 (V835/4375019) has been seen in other GSM designs from Nokia. Sharp-eyed readers might also notice the "UPP" marking on the baseband package, which we speculate stands for Universal Protocol Processor.

We've recently discussed a somewhat hobbled dual-mode telephone based on Qualcomm's MSM6300 platform (www.eet.com and search Article ID: 159400942), but this dual-mode baseband platform is not a point on the data sheets.

TI and ST originally set out to field merchant market alternatives that would combat Qualcomm's CDMA juggernaut. Although their widely publicized effort has met with only modest success to date, the ability of TI (and presumably Nokia) to find baseband common ground between CDMA and GSM is intriguing. Despite challenges, the software-defined radio is getting closer by the day.

David Carey, president of Portelligent (www.teardown.com). The Austin, Texas, company produces teardown reports and related industry research on wireless, mobile and personal electronics