Nokia Bell Labs, Mitsubishi Electric and the Center for Wireless Communications at University of California San Diego in the US have jointly developed a new envelope-tracking power amplifier with the potential to significantly enhance the energy efficiency of next-generation base stations.
The gallium-nitride power amplifier supports modulation bandwidth up to 80MHz, four times wider than the signals used in other envelope-tracking power amplifiers.
This translates to a gain efficiency of 41.6% in wide-bandwidth operation, Nokia said, making it a promising candidate for 5G base stations.
Next-generation wireless systems are using complex modulated signals with large peak-to-average power ratio and extra-wide modulation bandwidth, which will require power amplifiers to operate most of the time at backed-off power levels that are well below their saturation levels.
But the efficiency of power amplifiers is generally significantly degraded at backed off levels. While envelope-tracking power amplifiers are considered a promising solution to this problem, so far the supply-modulator circuit has been the bottleneck limiting modulation bandwidth.
The new prototype uses Mitsubishi Electric's high-frequency GaN transistor technology and Nokia Bell Labs' real-time digital pre-distortion system to help remove this bottleneck and achieve wider modulation bandwidth, the companies said.
Technical details of the system will be presented during next month's IEEE MTT International Microwave Symposium in Hawaii.