6 June 2011

Fujitsu develops first GaN HEMT T/R module operating in C–Ku band

At this week’s IEEE MTT International Microwave Symposium (IMS 2011) in Baltimore, MD, USA (5 June), Fujitsu Laboratories Ltd of Kawasaki, Japan is presenting the development of what is claimed to be the first transmitter/receiver (T/R) module using gallium nitride (GaN) high-electron-mobility transistor (HEMT) technology that operates across a wide bandwidth range of C-band, X-band, and Ku-band (C–Ku-band) radio frequencies (6–18GHz).

By combining the what are claimed to be world’s best performing GaN power amplifier (PA) — announced last year at IMS 2010 — with a newly developed GaN low-noise amplifier (LNA), the researchers have achieved a compact T/R module that generates a high output of 10W.

The firm says that the technology enables the integration of multiple types of communications equipment — each currently operated at a different frequency range — into a single module, allowing the development of smaller, lighter radar equipment and wireless communication systems.

Figure 1: Photo and structure of GaN wide broadband T/R module.

In line with an increasingly network-based society, radio wave demand in wireless systems is expected to increase even further, says the firm. For example, aircraft radar typically switches between the C-band (which can detect distant objects and works well in rain) and the X- and Ku-bands (which are able to measure physical objects with high-precision).

Currently, this demand for multiple frequency ranges requires different communications equipment, each suited to their respective frequency band. However, a single T/R module capable of covering the entire C–Ku-band range would meet a variety of needs, allowing systems to become more compact.

T/R modules are essential to operate multi-functional radar over a broad spectrum. Users therefore demand that they wide-band features capable of operating across multiple frequency ranges, as well as high-output performance in order to cover a wide area. To develop a T/R module with 10W-class high-output power over a wide broadband range (such as the C-Ku-band), not only is a wideband PA and LNA required, but it is also critical to improve the T/R module’s heat dissipation characteristics, as heat generation intensifies in tandem with higher output levels.

Figure 2: Photo and cross-sectional diagram of GaN wide broadband T/R module.

It is also necessary to reduce signal losses in the input/output terminal to maintain frequencies up to 18GHz. This is because, at higher frequency ranges, input/output signal losses increase in the terminal portion of the T/R module.

By adopting a GaN HEMT, Fujitsu Laboratories has developed a compact, high-output GaN HEMT T/R module that covers the ultra-broadband C-Ku spectrum (6–18GHz). Key features of the new technology are as follows:

• Fujitsu Laboratories has developed an embedded heat-sink structure that efficiently dissipates the heat generated at high output levels. The heat-sink is built into the T/R module's multi-layer alumina ceramic substrate. Compared with previous designs, heat dissipation has improved by a factor of five times, enabling high output levels of 10W.

• Fujitsu Laboratories has devised an ultra-broadband terminal structure that reduces the input/output terminal signal loss that occurs at higher frequencies. With the new terminal structure, high-frequency signals passing through the module can be transmitted at up to 40GHz, three times the frequency levels of previous designs.

• In addition to the GaN HEMT PA featuring the record output performance developed by the firm last year, the researchers have developed a new LNA using GaN HEMTs. The compact 2.7mm x 1.2mm LNA achieves a gain of 16dB across 3–20GHz and noise figures of 2.3–3.7dB (claimed to be record performance levels).

The new technology has enabled Fujitsu Laboratories to develop a compact T/R module measuring just 12mm x 30mm. The firm says that the new technology will enable a single T/R module to operate at multiple frequencies, paving the way for further system integration in broadband communications and radar systems that use various frequencies, meaning more compact and lighter equipment.

Fujitsu Laboratories targets the technology at a wide range of applications that require compact modules with high output across wide bandwidths, including wireless communications and radar systems.

Tags: Fujitsu GaN HEMT T/R module

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