FROM EDN EUROPE: Devices and standards progress for cellular handsets

The annual cellular-fest of the 3GSM conference brings with it a plethora of announcements in the mobile-communications arena. IP provider TTPCom (www.ttpcom.com) has introduced a cellular-modem reference design that revises system partitioning of functions in the conventional mobile-phone architecture. Rather than split signal-processing and control functions between a DSP and a control processor, the new modem design integrates everything from protocol stack to RF drivers on a single processor.

The design exploits the capability of the new generation of microprocessors with extended DSP functions; specifically, TTPCom is using the StarCore S1400 for its first demonstration of the concept, although the company says that other implementations may follow. Today's phones are likely to need a conventional microcontroller to run high-level applications, and the available cycles of that machine are limited if it is constantly dealing with high-priority interrupts from the communication system; freed of that load, the microcontroller can run an open operating system.

You will also see benefits in a unified and smaller memory requirement for the modem itself and in lower power demand. By separating modem and application domains, TTPCom adds, you will also reduce the need to reverify correct modem operation each time a new phone variant is designed.

From Silicon Labs (www.silabs.com), comes a chip that you might have thought impossible: a power amplifier for a GSM/GPRS (Global System for Mobile Communications/General Packet Radio Service) handset built entirely in standard CMOS technology. All functions, from transceiver to antenna switch—including high- and low-band amplifiers, complete GSM power control, thermal- and load-mismatch protection, harmonic filtering, and matching networks—have been integrated onto one die. Its makers also claim it is better specified than previous power-amplifier modules, offering margins to specification across full voltage and temperature ranges.

The design uses an undisclosed architecture that is sufficiently innovative to warrant the description of a new "class" of operation; in particular, it can handle the voltages experienced by the output devices (which can reach 12 to 20V in the case of poor antenna match) with transistors built in a standard 0.35-micron process. It will deliver the full 3GPP (Third-Generation Partnership Project) power level of 33 dBm.

Built as a single die with flip-chip mounting, its thermal performance is also better than a multichip module's, the company says. Coded Si4300, the device will be available as an 18-pin land-grid array and will cost $2.82 (10,000). You can use Silicon Labs' new architecture with the nonlinear GMSK (gaussian-minimum-shift-keying)-modulation GSM signal. The device does not extend to the linearity needed for WCDMA (wideband-CDMA) signals, although the company does not rule out such a progression.

SiGe Semiconductor (www.sige.com) is offering just such a device—an integrated amplifier for WCDMA handsets in the 1900-MHz band. Living up to the company's name, the RangeCharger SE5120 uses SiGe (silicon-germanium) technology licensed from IBM, where previous offerings predominantly used GaAs (gallium arsenide). The device integrates a three-stage power amplifier that will output 28 dBm with a linearity of –38 dBc. Compared with a modular solution, the device removes the need for a separate voltage regulator, power-amplifier power switch, detector, and isolator. Its conventionally constructed lead-frame package improves thermal performance, and the signal path requires no external passives.

Racal Instruments (Wireless Solutions, www.aeroflex.com/riws) offers the 6401 AIME/CT ISHO (Intersystems Handover) test set, which targets a potentially thorny problem that will emerge with 2G/3G (second- and third-generation) handsets: performance-measurement issues in the handover between networks (Picture). Initial products are believed to have suffered from poor performance and dropped calls, particularly when handing off from 2G to 3G services. Racal says that most of the certified test cases for 3G so far relate to basic network operation. The company currently has a group of 51 test cases due for submission.