The Othello-G radio supports full quad-band operation and integrates virtually all the necessary components for a complete cellular handset radio design such as voltage-controlled oscillators (VCOs) and the associated tank circuits, PLL loop filters, and power management. Analog Devices Othello-G radio (part number AD6548) is a single chip combining all the radio and power management functions for an ultra-compact, cost-effective GSM/GPRS radio. The only external components required for a complete radio design are the receive SAW (surface acoustic wave) filters, power amplifier, transmit/receive switch, and a few passives.

Othello-G features four fully integrated programmable gain differential LNAs (low-noise amplifiers) for full quad-band (GSM850/900/1800/1900) support. Othello-G uses a single integrated LO (local oscillator) VCO (voltage control oscillator) for both receive and transmit circuits. The synthesizer lock times are optimized for GPRS applications up to and including class 12. To dramatically reduce the radio BOM, the synthesizer integrates a loop filter and incorporates a complete reference crystal calibration system. ADI's Othello-G radio is available now.

The ADI team began looking at designing and manufacturing a direct-conversion radio for GSM back in the late 1990s. By 1999, they released the original Othello chipset, a two-chip GSM radio. "This was the first open-market direct conversion radio for GSM," notes Doug Grant, Dir of Business development for RF and wireless systems at ADI, "Many said it couldn't be done because of the bursty nature of the GSM signal, the DC offset correction, temperature drift, and other issues. But, we put a lot of engineering effort into it, making use of our precision analog design technology and 40 years of expertise. Over the next few years, pretty much everyone copied us."

So what's new with Othello-G? This transceiver is housed in a 5x5 mm package, with a complete radio taking up 1.5 sq.cm. ADI reports that there is a 75% reduction in component count from its previous generation and 30% smaller area. The device features direct connection to the battery, so there is no need for external voltage regulators. In short, the chip requires 23 external components, and "none of them are critical," says Grant.

How did they reduce the component count? ADI credits its own integration efforts as well as those of the manufacturers whose components connect around the transceiver, such as advances in SAW filter integration. Also, while most other radios for GSM/GPRS have an external master reference oscillator which is usually a packaged VCTCXO, the Othello-G features on-chip oscillator circuitry and temperature calibration on chip, so all that is required externally is a crystal.

Of course, it doesn't matter how small the radio is, if its performance isn't up to par. The ADI team claims the Othello-G offers state-of-the-art sensitivity performance. "Best in class is now -109 to -110 dBm sensitivity, which we meet easily."

So, what can Othello fans look forward to in the future? "Othello-G is our latest, state-of-the-art GSM/GPRS radio. From here, our next activities are going to be towards an EDGE radio which is similar in terms of integration and size. EDGE has some additional challenges because it requires a slightly different modulation scheme than GSM/GPRS. In parallel and moving forward, we are working on our multimode radios that cover GSM/GPRS/EDGE/3G standards," reports Grant.

Available now. Price: 10,000 qty. under $3.00

Analog Devices, Inc. +1-800-262-5643 www.analog.com