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Toshiba claims GaN microwave power record

Toshiba claims GaN microwave power record

The Japanese conglomerate turns up the power for high-definition satellite broadcasting with its Ku-band GaN-on-SiC HEMT.

Toshiba has produced a GaN HEMT with an output power of 65.4 W at 14.5 GHz, that it hopes will replace competing electron-tube technologies in satellite applications.

According to the Japanese company, this is the highest power-output FET to operate in the Ku-band, the region of the microwave spectrum between 12 and 18 GHz.

Toshiba pushes Ku-Band amps
Toshiba pushes Ku-Band amps

Presented at European Microwave Week on October 8, the device will be sampled at the end of 2007 and should enter mass production in March 2008.

The GaN HEMTs are marketed for high-capacity, high-definition satellite broadcasting base stations and high-power radar systems, which both require high-power amplifiers.

“Demand is particularly strong for GaN devices, which offer advantages over GaAs devices in heat dissipation and high power performance characteristics at high frequency,” Toshiba said.

The HEMT's designers ensured high rates of heat conduction by growing AlGaN and GaN layers on a thermally-conductive SiC substrate. The circuit design was also configured to be highly heat-dissipative.

Via holes from the surface source electrodes to the backside ground electrode are used to reduce parasitic inductance in the device. Making vias through SiC is a challenging process, so successfully forming them in these HEMTs was a breakthrough for Toshiba.

The device comes on a 3.4 mm x 0.53 mm chip that measures 21.0 mm x 12.9 mm in its packaged form and offers a linear gain of 8.2 dB. Such modest proportions should offer the GaN device a clear advantage over its bulkier electron tube competitors.

However, klystron and traveling wave electron tube microwave amplifiers can offer kW power outputs that remain some way beyond the reach these individual FETs.

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