Highly Efficent 3G Power Amplification

Fujitsu announced that they have developed and successfully implemented highly efficient transmitting power amplification technology that also compensates for signal distortion in IMT-2000 (*1) third-generation wireless communications systems.

Picture shows IMT-2000 and Complementing Technologies.

Fujitsu has incorporated this technology in an LSI and used the chip to develop the world's most compact, energy-efficient transmitter amplifier for IMT-2000 base station systems.

Background
Faster Internet connectivity and data transmission speeds are increasingly important requirements for mobile communications. Third-generation systems using code division multiple access (CDMA) technology (*2) have been developed to meet these requirements for greater flexibility and speed. One implementation of CDMA, called W-CDMA, was adopted by NTT DoCoMo, Inc. for its "FOMA" service, which became commercially available in October 2001.

Transmitter amplifiers for IMT-2000 systems, which use CDMA technology, must provide good linearity and low distortion in amplifying broadband signals with high dynamic range, as well as high power efficiency (*3) to keep energy consumption low. Generally, these two requirements have been mutually exclusive, so there has been growing need for distortion compensation technology that could amplify signals while minimizing distortion and power consumption.

Today, transmitter amplifiers for wireless base stations use an analog feedforward technology to compensate for distortion. However, since this technology's power efficiency is already approaching its theoretical limit, there has been a need to develop a new approach to distortion compensation technology.

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About Fujitsu's New Technology
Fujitsu's new distortion compensation technology is based on the digital pre-distortion (DPD) method, which adds compensatory characteristics to the signal before distortion occurs. Fujitsu has incorporated this technology into a distortion-compensation LSI, and, using this chip, has developed a high-efficiency transmitter amplifier.

In tests, the new amplifier satisfied all IMT-2000 system wireless specification requirements, and achieved roughly double the power efficiency of conventional feedforward amplifiers, thus achieving significant improvements of efficiency and compactness in a transmitter amplifier.

Some of the key features of the new technology are as follows:

1. Wideband distortion compensation
Using an adaptive digital pre-distortion method, it enables amplifiable distortion compensation in the 20 MHz band used for W-CDMA communications. In addition to W-CDMA and cdma2000, it can be used for amplifiers in other CDMA or equivalent bandwidths.

2. Adaptive distortion compensation
This approach to distortion compensation is well suited to dealing with fluctuations caused by device inconsistencies, temperature changes, and aging.

3. Low power consumption
Thanks to Fujitsu's new distortion-compensation chip, the transmitter amplifier-which accounts for a large portion of the energy consumed in a wireless base station-has become much more efficient, resulting in less power consumption and enabling more compact size.

Fujitsu began shipping prototypes of its high-efficiency transmitter amplifier to Evolium SAS (*4) in December 2001, and in July 2002 began deploying units jointly developed with NTT DoCoMo, Inc. in DoCoMo's wireless base stations.