Fujitsu Labs Enables 1.5x Longer Battery Life for WiMAX Handsets

Apr 16, 2007
Masahide Kimura, Nikkei Electronics
On the right is the power amplifier circuit and the black box on the left is the DPD system. Fujitsu Laboratories will further develop these circuits into an MMIC and a SoC, respectively. They were shown at the company's R&D strategy meeting held on April 13.
On the right is the power amplifier circuit and the black box on the left is the DPD system. Fujitsu Laboratories will further develop these circuits into an MMIC and a SoC, respectively. They were shown at the company's R&D strategy meeting held on April 13.
[Click to enlarge image]

Fujitsu Laboratories Ltd. has developed a technology that boosts power efficiency of transmission amplifiers for mobile WiMAX handsets twice higher than the previous level. As far as mobile phones and other mobile WiMAX terminals on the company's assumption are concerned, power used by a transmission amplifier has constituted 70% of total power consumption thus far. The technology enables the battery life on those mobile devices to be 1.5 times longer, the company claims.

WiMAX requires a large-output power amplifier and a digital predistortion (DPD) system as it needs large peak power when transmitting data. Given the amplifier efficiency of low 10-20% power, however, most of input power has been wasted as heat. In addition, Fujitsu Laboratories designed its DPD technology for base stations and accordingly could not apply it to mobile handsets due to its large power consumption.

Combining high- and low-output power amplifiers this time, the company has achieved higher power efficiency. Fujitsu Laboratories also lowered power through the development of DPD technology for mobile terminals. The technology marked a power added efficiency (PAE) of 40% with 19 dBm output in proving tests, according to the company. Furthermore, the DPD circuit enabled 64QAM mode data upload, which resulted in a data rate of 13.5 Mbps, 1.5 times faster compared to the previous model without the DPD circuit.

Fujitsu Laboratories will further develop analog circuits of power amplifiers into an MMIC (microwave monolithic IC) and the DPD system into a SoC, with the aim of commercializing the technology in FY2008.