Fujitsu Introduces World's Most Compact, High-Efficiency Transmitter
Amplifier for IMT-2000 Systems
September 6, 2002
Fujitsu announced that they have developed and successfully implemented
highly efficient transmitting power amplification technology that
also compensates for signal distortion in IMT-2000 3G wireless communications
systems. 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.
Details of the new technology will be presented at a conference
of the Institute of Electronics, Information, and Communication
Engineers on September 13 at Miyazaki University in Japan.
Background
Faster Internet connectivity and data transmission speeds are increasingly
important requirements for mobile communications. Third-generation
systems using CDMA technology have been developed to meet these
requirements for greater flexibility and speed. One implementation
of CDMA, called W-CDMA, was adopted by NTT DoCoMo 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
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.
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
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.
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