This morning, Nokia announced it has acquired Eta Devices, a U.S. start-up focused on improving the efficiency of power amplifiers (PA) used in cellular base stations, 802.11ac access points and handsets.

Eta Devices was formed in 2010 to commercialize a patented asymmetric multilevel outphasing (AMO) technology, developed at MIT by engineering professors Joel Dawson and David Perreault, co-founders of the company. Termed ETAdvanced, the AMO approach improves PA efficiency by selecting the amplifier's supply voltage to best handle the RF signal level. Unlike envelope tracking, which provides continous dynamic adjustment of the amplifier supply voltage, Eta's approach seems to select from a discrete number of supply voltages and amplifiers. The company's website states

For narrowband applications, ETAdvanced is 25 percent more efficient than envelope tracking, and the implementation is simpler, given fewer components. Unlike envelope tracking, ETAdvanced supports ultra-wideband channels of up to 160 MHz, making the technology future proof by supporting both LTE Advanced and 802.11ac Wi-Fi. This is unlike envelope tracking, which only works up to 20 to 40 MHz — far short of the 100 MHz required by LTE Advanced and the 160 MHz utilized by 802.11ac.

A private company before the acquisition, Eta Devices has headquarters in Cambridge, Massachusetts and an R&D office in Stockholm. It employs approximately 20 people. Nokia’s acquisition includes the fixed assets, employees, intellectual property rights and the lease and supplier agreements. The price Nokia paid was not disclosed.

The acquisition indicates that Nokia assessed AMO as a viable technology for improving PA efficiency and reducing base station energy usage.