Mumbai: NEC Corporation has developed a compact gallium nitride power transistor amplifier for third generation (3G) base stations which, it said, has the world''s highest output power level of 400W, as also low distortion characteristics.

This amplifier is composed of a single transistor package, which achieves the world''s greatest power output amplification under a W-CDMA scheme, without using any power-combining circuits, the company said in a release.

The research has been carried out by Professor Yasushi Nanishi of the Ritsumeikan University under the `High-Power, High-Frequency Gallium Nitride Device Project'' of the Research and Development Association for Future Electron Devices (FED), with support from the New Energy and Industrial Technology Development Organisation (NEDO).

This power transistor achieves high output power density under high-current (1A/mm) and high voltage (45V) operation using NEC''s field-modulating plate technology. The single-ended galium nitride (GaN) power amplifier also boasts of a compact configuration that decreases the number of assembled RF components. Newly developed output bias networks inside the amplifier suppress the memory effect of the amplifier, thereby achieving excellent linearity with a digital predistorter placed within.

The need to achieve a large-capacity and high-speed system is becoming more crucial with the rapid increase in traffic accompanying the swelling number of 3G mobile subscribers and increasingly sophisticated and diversified 3G services worldwide. To achieve such a system a power amplifier with higher output power and high linearity for 3G base stations are vital. For this, the amplifier needs to be compact in size and should be able to realise energy savings.

The features of the newly developed power amplifier for 3G base stations include:

• Single-ended GaN amplifier with a digital predistorter for W-CDMA base stations;
• Operation voltage: 45 Volts;
• Peak output power of W-CDMA signal: 400W (2.14 GHz);
• Third order intermodulation distortion: -50 dBc (At average output power of over 60W); and
• Drain efficiency: 25 per cent (at average output power of 60W).

This new research is expected to play an important role in increasing output power, as well as downsizing and energy savings of base station amplifiers for the third generation and beyond. NEC said it would continue to carry out aggressive research and development of the technology for achieving commercialisation by the end of 2008.

The transistors used for this amplifier are made on a GaN epitaxial wafer, which was developed under the NEDO high-power, high-frequency gallium nitride device project, and manufactured by Toyoda Gosei Co Ltd.

NEC Corporation is one of the world''s leading providers of internet, broadband network and enterprise business solutions dedicated to meeting the specialised needs of its diverse and global base of customers. NEC delivers tailored solutions in the key fields of computer, networking and electron devices, by integrating its technical strengths in IT and networks, and by providing advanced semiconductor solutions through NEC Electronics Corporation.

The NEC group had net sales of approximately €4,825 billion ($41.2 billion) in the fiscal year ended March 2006.