20 June 2012

Mitsubishi develops 170W, 70%-efficiency GaN-on-Si PA for base-station transmitters

Tokyo-based Mitsubishi Electric Corp has developed a prototype 2GHz power amplifier (PA) for mobile communications base stations that features a gallium nitride (GaN) transistor on a silicon (Si) substrate instead of more costly silicon carbide (SiC), achieving power output of 170W and power conversion efficiency of 70% (claimed to be unprecedented among 2GHz PAs with outputs of 150W or higher).

Picture: Mitsubishi Electric’s 170W, 2.1GHz GaN-on-Si power amplifier.

While amplifiers that use GaN transistors consume less power and have a higher output than amplifiers made with silicon transistors, they typically require a more robust substrate made of SiC, which elevates the cost. Initial efforts to develop a GaN transistor using a Si substrate were hampered by deformation between the GaN layer and Si substrate, which led to increased loss and decreased power conversion efficiency. However, the firm has designed a high-performance transistor by optimizing the GaN crystal structure and inserting a buffer layer between the GaN layer and Si substrate.

Mitsubishi Electric’s new GaN-on-Si power amplifier achieves a power conversion efficiency of 70% at 2.14GHz, improving upon the 58% conversion efficiency of 2.17GHz Si transistor amplifiers currently available commercially, it is reckoned.

Graphic: Optimized crystal structure of GaN-on-Si substrate.

The amplifier is expected to lead to the development of smaller and more power-efficient base-station transmitters. The installation of such equipment in tighter spaces should help to expand wireless network coverage to accommodate increasing wireless traffic due to smartphone proliferation, the firm says.

In future, Mitsubishi Electric expects to further downsize the power amplifier and its power supply and cooling units to enable even smaller mobile communications base stations.

Tags: Mitsubishi GaN-on-Si PA Base-station transmitters

Visit: www.MitsubishiElectric.com