A global phone with local restrictions

Call it a conditional truce in the ongoing standards wars within the handset industry. Samsung has rung in the first known phone to support both cdma2000 and GSM. The SCH-A790 is a quad-band, dual-mode terminal (800-/1,900-MHz CDMA; 900-/1,800-MHz GSM) sold through Verizon in the United States for use by its globe-trotting customers.

Released last year, the A790 has many of the usual high-end features, including a built-in camera and two displays: a 2.2-inch thin-film-transistor liquid-crystal display with 128 x 160-pixel resolution and 262,000 colors; and an external 1.2-inch TFT LCD with 65,000 colors. A VGA camera, speaker phone, voice recorder, voice-activated dialing, audio caller ID and picture ID, vibrator, polyphonic ring tones, downloadable applications and a host of other bells and whistles are also part of the package.

The blockish design of the clamshell phone uses a beveled outer case to mitigate an otherwise sharp-edged feel. The squared-off look extends to the keys themselves, which split down the middle for redundant actuation of the 2-5-8-0 positions. Sometimes attempts to be different tend to go a little too far.

On the more practical side, the A790 supports cdma2000 1xRTT for high-speed data when the user is in the United States. Overseas, it also offers lower-speed General Packet Radio Service data capability in the GSM mode of operation.

Electronics for the SCH-A790 are found on the eight-layer buildup-technology mainboard. A second flex circuit assembly in the upper half of the clamshell design supports both of the color LCD panels and the VGA camera.

Outside CDMA's still-sizable area of success, GSM rules global handset shipments, so Qualcomm Inc. made a decision to build in GSM protocol support. As such, its MSM6300 jack-of-most-trades chip set is central to the A790 design, supporting baseband duties for cdma2000 and GSM along with Qualcomm's proprietary global-positioning system solution, gpsOne.

System memory comes in the form of 32 Mbytes of SDRAM and two 32-Mbyte NAND flash devices, all three in the same stacked package from Samsung (KAG00J007M). The memory implementation alone testifies to the differing architectures at play. In this case it displaces the traditional execute-in-place NOR flash for code storage in favor of a NAND solution. While the jury is still out on which memory types will remain in favor among handset designers, the A790 breaks some new ground in the NAND-SDRAM approach.

Things also have to work a little differently in the RF world when diverse signals and protocols are in play. To separate the CDMA and GSM signals from and to the antenna, the A790's radio system uses a New Japan Radio (NJG1519KC1) SP4T switch, two ports of which are connected to CDMA duplexers-one for each band-and the third port to a GSM switchplexer handling GSM Tx-Rx control. The fourth switch port connects to the GPS receive path during a position fix.

The transceiver for the GSM signal as well as the CDMA transmit processor are implemented on the same Qualcomm chip (RTR6300), but the CMDA receive path uses previously available Qualcomm devices for the low-noise amplifier front end and receive processor (RFL6000 and RFR6000, respectively). By partitioning the design in this fashion, Qualcomm needed to develop only one unique radio chip for the mixed-protocol platform. Skyworks' dual-band GSM power amplifier (PA) module (SKY77326-11), 800-MHz-band CDMA PA (CX77105) and 1,900-MHz-band CDMA PA (CX77107) perform all of the needed final-stage RF amplification.

Other key components include a Qualcomm PM6050 for power management, a Yamaha audio synthesizer (YMU765) for polyphonic sound and a VGA CMOS image sensor with on-board A/D converter from Hynix Semiconductor (HV7131).

Not surprisingly, the dual-LCD display and imaging capability and dual-mode functionality have added some cost to the design. Indeed, the A790 is encroaching on the complexity of recent entry-level Universal Mobile Telecommunications System (UMTS) phones, with 675 electronic components and an estimated cost of goods sold that is north of $140.

Unlike UMTS handsets, however, the A790 is serving as a geographic bridge for U.S. CDMA customers abroad rather than the "new service plus legacy compatibility" target of UMTS. What seems like a multiprotocol nirvana is really a means for Verizon to partner with Vodafone for international GSM roaming, and charges of $1.30/minute should allow both parties to enjoy a tidy profit. The Verizon agreement with Vodafone is made possible by the hobbled GSM capability, which works only in non-U.S. locations given the 900/1,800-MHz GSM banding. No competitive threats are present on either side.

Thus, the notion of a multilingual handset remains a flight of fancy. In the meantime, the SCH-A790 can be considered an interesting, but niche, product.

Forthcoming chip sets from Qualcomm promise even greater protocol flexibility. But unless competing carriers are motivated to share a common hardware platform-and why would they?-any genuine world phone will always be born with handcuffs.

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.