Power-supply modulation steps up handset-power-amp efficiency

摘要

RF-engineering company Nujira has extended the reach of its efficiency-boosting technology for power amplifiers into the handset. The company has until now focused on the infrastructure side of communications, selling its HAT (high-accuracy-tracking) power-line modulators into applications such as base stations.rnThe fundamental principle is that RF power amps-especially those for modern digital-modulation schemes, such as 3G and 4G (third- and fourth-generation) LTE (long-term evolution) and WiMax (worldwide interoperability for microwave access)-must be linear; that is, they must operate from a fixed-voltage rail. When modulation levels are low, a great deal of the power in the output stage contributes nothing to the output; therefore, efficiency is low.