Designed primarily for the entry-level cell phone user and first launched in Brazil, Kyocera's K112 handset still supports a fairly rich feature set including games, calculator, ringtones, and an alarm—one of my favorite little extras. On a more technical note, the handset also features an internal antenna— an amazing bit of RF engineering in itself—to bypass those breakage-prone stubs and whips.
The single-band CDMA/AMPS K112 is based on Qualcomm's recent CDMA2000 standard—designed to improve communications efficiency versus the original IS-95 CDMA protocol. More importantly from an electronics view, the design was one of the first handsets we analyzed to use Qualcomm's radioOne chipset with a Zero Intermediate frequency (ZIF) architecture, also known as direct conversion.
Keeping in mind that the "digital cellphone" still relies on an analog carrier of bitstreams— whether for voice or data— radio complexity remains significant. The CDMA direct conversion architecture results in fewer components versus the previous multi-stage up/down-conversion radios but lags the simplification seen in the latest-generation GSM designs.
The digital baseband processor (MSM6000) is paired with two main radio devices, one for the transmit path (RFT6102), and one for the receive path (RFR6002). Separation of the transmit and receive devices reflects some distinctly analog issues in managing interference and keeping clean communications pathways given the simultaneous transmit and receive activity inherent to CDMA. Incoming signals are piped through a duplex filter to a low noise- amplifier (RFL6000) to boost signal levels and oscillators from Kyocera generate the appropriate RF frequencies for mixing inside the radio chips. A RFMD GaAs PA Module (RF6000-2) is tasked with boosting output signals to the internal antenna.
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Power management at the system level comes via a dedicated analog ASIC (PM6000) responsible for generating the multiple chip supply voltages and handset lighting required. Because supply functions have been rolled up in the PM6000, there is a notable absence of small-scale regulators on the board. Only a charge controller chip and smattering of transistors are required to complete the power management chain.
Despite the relatively inexpensive CDMA handset cost structure for the K112, low cost cannot come at the expense of dropped signals and poor battery life. As such, the analog content in this entry-level phone actually contributes to system cost structure at a level similar to that of the digital baseband. Of course the analog goodies also contribute to the most important thing of all—making the call.
David Carey is President of Portelligent. The Austin, Texas company
produces teardown reports and related industry research on Wireless,
Mobile, and Personal Electronics. (www.teardown.com)