27 May 2010


Fujitsu doubles output record to 12.9W for C-Ku band GaN HEMT amplifiers

At this week's IEEE MTT International Microwave Symposium (IMS 2010) in Anaheim, CA, USA (23-28 May), Japan's Fujitsu Laboratories Ltd announced the development of an amplifier based on gallium nitride high-electron-mobility transistor (GaN HEMT) technology with record output power of 12.9W when operating in the wide range of the C-band, X-band and Ku-band radio frequency spectrum between 6-18GHz (more than double the output of existing ultra-broadband, high-frequency amplifiers). The amplifier's efficiency is 18% (see Figure 1).

Figure 1: Comparison of C-Ku ultra-broadband amplifier performance.

The new technology will make it possible for a single amplifier to operate at multiple frequencies, paving the way for further integration of systems, such as broadband communications systems and radar systems, that use various frequencies. For example, aviation radar typically switches between the C-band (which is relatively unaffected by rain) and the X- and Ku-bands (which offer high-precision detection of solid objects) so, conventionally, separate communications equipment is used for the different frequency ranges.

Also, previously, to achieve the output needed to cover large spectrums such as the C- to Ku-bands, multiple transistors have been connected in parallel to create an amplification circuit. However, as the circuit is physically longer, line loss increases, making it difficult to extend coverage up to 18GHz.

Key features of Fujitsu Laboratories' high-output ultra-broadband C-Ku spectrum (6-18GHz) GaN HEMT amplifier are therefore:

  • band-extending circuit technology devised by Fujitsu Laboratories that compensates line losses at high frequencies, employed in an amplifier for the first time (Figure 2);

Figure 2: Circuit block diagram.

  • circuit technology (fabricated on the semiconductor chip) that handles the dividing and combining of electrical power across an ultra-wide spectrum (Figure 3).

Figure 3: Fujitsu's new C-Ku band amplifier.

An amplifier able to cover - on its own - the entire range of the C- to Ku-bands would allow smaller systems that consume less power. Fujitsu says that this has led to interest in multi-functional radar, integrating communications systems and multiple radars into a single device.

Fujitsu Laboratories plans to apply the new single-amplifier technology to a wide range of applications that require high output across wide bandwidths, including wireless communications and radar. It should hence allow the development of smaller, lighter systems capable of covering wide areas. The technology can also be used in instruments for measuring the performance of amplifiers used in broadband communications and radar systems, says the firm.

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