Fujitsu Limited and Fujitsu Laboratories Ltd. today announced the development of a power amplifier using gallium nitride (GaN)(1) High Electron Mobility Transistors (HEMT)(2) that has achieved the world's highest output performance of 1.3W for wireless communications in the millimeter-wave W-band(3), for which widespread usage is expected in the future. The new amplifier will offer transmission output equivalent to approximately 16 times that of existing amplifiers that use gallium-arsenide (GaAs), thereby enabling W-band transmission ranges to be extended by approximately six times.
Fujitsu's new GaN HEMT-based power amplifier will make high-capacity wireless communications possible in regions in which it is unfeasible to lay optical fiber cables, in addition to ensuring high-quality communications in rain and under other conditions where the millimeter-wave signal is known to attenuate.
Part of this research was conducted under contract as part of the Research and Development Project for Expansion of Radio Spectrum Resources of Japan's Ministry of Internal Affairs and Communications. Details of the technology will be presented at the 2010 IEEE Compound Semiconductor IC Symposium (CSICS), to be held in Monterey, California from October 3-6, 2010.
In order to accommodate the demands for greater bandwidth resulting from increases in internet communications and expansions in mobile phone networks, optic fiber cables are being laid in nations throughout the world to create a high-capacity trunk-line system. This is problematic in areas with challenging topography, which has sparked interest in high-bandwidth wireless trunk lines that are capable of data transmission capacities in the range of up to 10 Gbps-on par with optical fiber cabling-as a way to bridge the "digital divide(4)" (Diagram 1).
The millimeter-wave W-band is an effective band for use in wireless communications at a speed up to 10 Gbps, as it is readily available. Diagram 2 shows an example of a wireless transceiver that employs the millimeter-wave W-band. The power amplifier, located inside the transmission unit, is the key component for amplifying the millimeter-wave signal to the intensity required for transmission.
Up until now, Fujitsu and Fujitsu Laboratories have succeeded in producing 350 mW of power using power amplifiers that employ GaN HEMTs. The millimeter-wave W-band, however, experiences significant signal attenuation due to factors such as atmospheric absorption and rain, and there has been demand for high-output power amplifiers that can transmit a stable signal across distances ranging from a few kilometers to several tens of kilometers.
In order to develop a millimeter-wave W-band power amplifier featuring high output, the following issues needed to be addressed.
Fujitsu developed the following technologies in order to resolve the aforementioned issues.
After analyzing the reason why electrons escaped from the electron channel layer and accumulated in the passivation layer, Fujitsu traced the issue to the existence of defects in the crystallization of the SiN used as part of the passivation layer. By enhancing the layer's SiN composition and crystalline structure, Fujitsu was able to build a passivation layer with minimal crystalline defects, making it difficult for electrons to accumulate. As a result, the technology was successful in amplifying high-frequency current to over two times the power of existing technology.
By performing electromagnetic analysis on the complex signal distribution of the high-frequency signal, based on the physical properties of the power splitter and combiner circuits, Fujitsu successfully designed a highly precise circuit that reduces signal attenuation in the two circuits. As a result, Fujitsu was able to increase design precision by roughly 15%.
The above technologies were employed to develop a power amplifier for use in millimeter-wave W-band wireless equipment. The newly developed amplifier achieves a maximum output of 1.3W, which, among GaN HEMT power amplifiers, represents the world's highest output in this frequency band using single integrated circuit.
Furthermore, the new technology achieves a transmission output equivalent to 16 times that of existing amplifiers that use GaAs. When employed in combination with the GaN HEMT receiver amplifier developed by Fujitsu last year, it is expected that transmission ranges will be able to be extended by approximately six times in comparison to transceivers that employ GaAs. This will enable millimeter-wave band wireless communications equipment to be deployed in a wider range of fields, while at the same time ensuring high-quality communications in which ample signal output can be obtained even when there is signal attenuation due to rain and other factors.
Fujitsu and Fujitsu Laboratories plan to work to further improve the performance and expand the frequency spectrum of the new GaN HEMT power amplifier, while at the same time employing the technology in a wide range of applications, including millimeter-wave-enabled trunk lines and ultra-high-speed wireless network access.
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 Gallium-nitride (GaN)
A wide band-gap semiconductor material that operates stably at high temperatures and with a higher breakdown-voltage than semiconductor technologies based on previous materials, such as silicon (Si)- or gallium-arsenide (GaAs)-based technologies.
 High Electronic Mobility Transistor (HEMT)
A field-effect transistor that takes advantage of operation of the electron layer at the boundary between different semiconductor materials that is relatively rapid compared to that within conventional semiconductors. Fujitsu pioneered its development in 1980, and the technology now underpins much of today's ICT infrastructure, including satellite transceivers, wireless equipment, GPS-based navigation systems, and broadband wireless networking systems.
Name for the radio band from 75 to 110 GHz. Used for high-speed wireless communications, automotive radar, image sensors, and other applications.
 Digital divide
Refers to economic differences between those people or regions with good access to information and communications technology, versus those people or regions with poor access.
Fujitsu is a leading provider of ICT-based business solutions for the global marketplace. With approximately 170,000 employees supporting customers in 70 countries, Fujitsu combines a worldwide corps of systems and services experts with highly reliable computing and communications products and advanced microelectronics to deliver added value to customers. Headquartered in Tokyo, Fujitsu Limited (TSE:6702) reported consolidated revenues of 4.6 trillion yen (US$50 billion) for the fiscal year ended March 31, 2010. For more information, please see: www.fujitsu.com.
Founded in 1968 as a wholly owned subsidiary of Fujitsu Limited, Fujitsu Laboratories Limited is one of the premier research centers in the world. With a global network of laboratories in Japan, China, the United States and Europe, the organization conducts a wide range of basic and applied research in the areas of Next-generation Services, Computer Servers, Networks, Electronic Devices and Advanced Materials. For more information, please see: http://jp.fujitsu.com/labs/en.
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Technical ContactsAdvanced Devices Research Lab.
Fujitsu Laboratories Ltd.
All other company or product names mentioned herein are trademarks or registered trademarks of their respective owners. Information provided in this press release is accurate at time of publication and is subject to change without advance notice.
Date: 04 October, 2010
City: Tokyo and Kawasaki, Japan
Company: Fujitsu Limited
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