Highly efficient power amplifiers could bring about 5G adoption much sooner than expected

Super-efficient power amplifiers could bring about the next generation of mobile internet technology (i.e. 5G), lightweight microsatellites for global communication networks and low-cost radars for collision avoidance in automobiles much quickly than was initially anticipated. The first 5G or fifth generation mobile devices should be released by the year 2019 and they will need improved power amplifiers to be able to operate at much higher frequencies. These new phones will be able to download and share all types of data much faster than today’s top-of-the-line 4G phones. They will also be able to provide better network coverage and consume less battery power while meeting the requirements of the emerging technology ‘Internet of Things’, where everyday devices will be connected to a centralised local area network, enabling them to communicate with and share data with each other.

The main purpose of power amplifiers is to transmit signals. As today’s mobile phone amplifiers are manufactured with gallium arsenide, they are unable to be integrated into the device’s silicon-based technology, known as complementary metal-oxide-semiconductor (CMOS). New amplifier designs have a CMOS-base, meaning that researchers can easily integrate the amplifier with the phone’s semiconductor, reducing their cost of manufacturing and power consumption while simultaneously boosting the chip’s performance. Silicon is typically much cheaper than gallium arsenide, has a relatively longer lifespan and is more reliable. It is also much easier to maintain or test a system-on-a-chip rather than several different components.

Professors at Purdue University have created the most efficient CMOS power amplifier in the frequency range desired for next-gen radars and 5G mobile phones. The findings have been detailed in two papers one of which was presented at the IEEE International Microwave Symposium held in San Francisco in May 2016. The second one is expected to appear in a future issue of the IEEE Transactions on Microwave Theory and Techniques journal. The CMOS amplifier was able to achieve an efficiency of 40 percent that allows it to be favourably compared to gallium arsenide amplifiers. The researchers were able to create this new amplifier by using silicon on insulator (SOI) i.e. a high-performance CMOS technology type. The new amplifier design comprises closely stacked multiple silicon transistors. This reduces the number of metal interconnections that are required between transistors, helping decrease "parasitic capacitance" that hinders performance and can potentially damage the electronic circuits.

The transistors have been merged in such a manner that there is minimal metallisation around the device, the capacitance is reduced and a much higher efficiency is achieved. The researchers are striving to totally eliminate metallisation that occurs between transistors. These new amplifiers might be able to improve road safety substantially by bringing low-cost avoidance radars for automobiles and electronics used in lightweight communication microsatellites. The CMOS amplifiers might even enable researchers to design microsatellites that are less than one-hundredth the weight of modern day satellites. Three U.S patents related to CMOS amplifiers have been issued and this research was partially funded by the U.S. Defense Advanced Research Projects Agency. Researchers are now working on an advanced version of the CMOS amplifier that could potentially be twice as powerful. However, more research will be needed to perfectly integrate the CMOS amplifier into the semiconductor of mobile phones of the future.