Fujitsu Limited and Fujitsu Laboratories announced the development of a gallium-nitride (GaN) high-electron mobility transistor (HEMT) power amplifier for use in W-band (75-110 GHz) transmission systems.
Fujitsu noted for long-distance, high-capacity wireless communications, one approach is to utilise the W-band and other high frequency bands that encompass a range of usable frequencies, with increased output using a transmission power amplifier. In addition, there is demand for improved efficiency in power amplifiers to mitigate the increased power consumption of communication systems.
To address these requirements, Fujitsu has developed a power amplifier for W-band transmission that offers both high output power and efficiency, improving transistor performance through the reduction of electrical current leakage and internal GaN-HEMT resistance. Fujitsu has achieved output density of 4.5 W per millimetre of gate width and has confirmed a 26% reduction in energy consumption compared to conventional technology.
Fujitsu anticipates that siting this new power amplifier between wireless communication systems in two locations can achieve high-bandwidth communications at 10 Gbit/s over a distance of up to 10 km.
In order to increase the distance and capacity of wireless communications and decrease energy consumption with indium-aluminium-GaN (InAlGaN) HEMTs, Fujitsu has developed two technologies that reduce internal resistance and current leakage.
Fujitsu has developed technology that can reduce resistance to one tenth that of previous technology when current flows between the source or drain electrodes and the GaN-HEMT device. The technology involves a manufacturing process that embeds GaN plugs directly below the source and drain electrodes to generate electrons at high densities.In addition, to address current leakage and the resulting reduced operational performance for the power amplifier due to reduced drain current the new technology maintains drain current by distributing InGaN to create a barrier layer below the channel layer. This reduces electron detours during operation and current leakage.
Fujitsu noted that the previous record for power amplifier output density in the W-band for transmitters was 3.6 W/mm of gate width with technology developed by Fujitsu Laboratories. The newly developed technology delivers output of 4.5 W/mm of gate width for a power amplifier designed to operate at 94 GHz.
Fujitsu stated that it plans to apply the new technology to the development of power amplifiers for wireless communications with long range and higher capacity, while also enabling easier installation than with fibre. It aims to commercialise the technology by 2020.
Fujitsu noted that the research was supported by Innovative Science and Technology Initiative for Security, established by the Acquisition, Technology & Logistics Agency (ATLA) of the Japan Ministry of Defense.
