2.5G mobile eyes thin market

Thin is in. While Motorola's RAZR family and, more recently, Samsung's Blade phone designs get much of the press, others too have been quietly shaving handset thickness to stay fashionably slim.

The Panasonic EB-X800 triband GSM camera phone measures in at just over 17 mm, a few millimeters thicker than the more widely known ultraslender designs from

Motorola and Samsung. Panasonic's competitors probably enjoy substantially fatter sales however, since the X800 is not offered by any of the major U.S. carriers at this time. While banding for the phone allows global GSM operability, the rather tight control of customer hardware provisioning by U.S. and other carriers worldwide means direct retail handset sales tend to lag those of designs subsidized through carrier plans.

Supporting GPRS Class 10 data, the clamshell-style phone features a 2.2-inch thin-film-transistor LCD main display (176 x 208 pixels, 65,536 colors), while the external supertwisted-nematic 4,096-color display (64 x 96 pixels) provides caller ID and other visuals. A VGA camera with white-LED flash is standard fare, though resolution is somewhat low by current standards. Symbian Series60 software is used for the phone operating system, with Bluetooth, serial or IR available for data transfer and pluggable XD memory for expansion storage. A surprisingly high five hours of talk time is claimed based on the unit's standard 720-milliampere-hour lithium ion battery, a figure reflecting power-efficient design, optimistic characterization or perhaps a mix therein.

With clean external lines enabled by an internal antenna, the X800 uses a clever one-push, auto-open button to gracefully unfold, a nice touch in mechanical hinge design, which complements the smooth-finish plastic two-tone case. Given the potentially fragile nature of a thin flip-phone design, an internal cast-magnesium shield does double duty as a mechanical stiffener.

Electrical design illustrates one camp in the evolution of high-function OS feature phones, specifically the separation of communications functions from applications- and media-related silicon. A Texas Instruments OMAP310 processor based on an ARM925 core is paired with a three-chip memory stack from Intel, the latter providing a total of 48 Mbytes of NOR flash and 16 Mbytes of low-power mobile RAM. This processor subsystem for LCD and camera resides on the same pc-board assembly as the keypad contacts, interfacing to the remainder of system electronics with a stacking connector.

The main board (actually about half the area of the larger keypad/applications board) hosts the communications platform of the design along with power management, expansion memory socket and a SIM card slot.

In keeping with a design philosophy of single-vendor communications platforms, Panasonic chose cellular silicon from Infineon Technologies. A PMB8870 baseband processor contains both the DSP core and an additional ARM926 core, though based on memory sizes and distribution, it seems most likely that the Omap processor is running the Symbian OS. Also, the PMB8870 integrates an analog baseband to bridge the digital realm with the RF radio, a partitioning counter to some alternative platforms that place analog baseband off-chip and monolithically with other analog comms elements.

Here, a separate power-management ASIC from Infineon (part number PMB6811) and a power/audio combo chip from Matsushita/Panasonic (the AN3206A1) collectively tackle most other system mixed-signal chores.

The single-chip Infineon transceiver (PMB6680) contains all of the radio system, including the RF voltage-controlled oscillator for up- and downconversion. A mix of off-chip SAW and silicon filters see to radio bandpass needs for transceiver input and output. The RF Micro Devices RF3146 multiband RF power amplifier is fed with the remaining piece of the Infineon platform, a gain-limiting driver amp (PMB2258), which passes transmit signals from the radio transceiver.

A complex rigid-flex assembly is used in the upper half of the flip design, interconnecting both LCDs and the camera to the lower half of the design via the push-button hinge assembly. An additional audio/power combo chip from National Semiconductor is the primary semiconductor residing on this rather complex--and likely pricey--bit of interconnect.

Unfortunately, the Panasonic design may represent the end of the line for the company in pure-GSM mobiles. While Panasonic's success in Japan with 3G design continues, the company has found it difficult to compete in the often cutthroat environment for pure-GSM terminals. Despite a demonstrated ability to innovate in consumer goods, the company has decided to retrench mobile efforts in next-generation terminals, where market-share gains are felt to be more realistic. It's a wicked game of scale in handset manufacturing, and those without big volumes can sometimes find themselves frozen out.

Electronics can change rapidly however, and the sense of style in the X800 might just appear--in modified 3G form--from Panasonic, a company that's arguably savvy about consumer tastes.

By 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.

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