An increasing number of LTE, WiMAX , 3G and other advanced broadband radio systems are being installed around the world to improve both coverage and capacity. With the radio networks normally accounting for around 80% of the total electricity used by an operator, the increase in energy usage, coupled to continuing rises in the price of energy, is driving up operational costs for network operators and contributing to an increased environmental impact. Current LTE, WiMAX and 3G base stations are very power-inefficient due to the use of linear RF power amplifiers (PAs), which typically account for half of the total power used by a base station.

Another increasingly important consideration is the need to support a wider range of frequency bands, and multi-mode operation, from the same basic PA design to meet the emerging needs of operators worldwide. Current efficiency improvement techniques, being essentially narrow-band, cannot satisfy this requirement.