Energy Efficient Power Amplifier Design
Legacy mobile handsets already incorporate multimode features, with dual, tri and quad band functionality already the norm, and the very latest smart phone having WiFi connectivity. However, complete interoperability is still in its infancy with several hurdles still to overcome, and energy efficiency is one of them. Unless mobile handsets are smart enough to be energy aware and flexible in switching between several standards, the 5G slogan of anytime, anywhere connectivity could remain a "vision" rather than close to market. To attain true energy efficiency lays down stringent design requirements on the RF system that in today's handset is a key consumer of power. In fact the power amplifier is the main culprit for stealing energy from the battery supply, and the reason why mobile handset become hot after a lengthy call. This effect will multiply when ubiquitous broadband connectivity becomes the standard, leading to significant research on active cooling, considering approaches similar to fan techniques in laptop and desktop devices. However, rather than trying to reduce the effects of overheating, we aim to tackle the problem at the bud, by considering energy efficient designs. In fact, this chapter is the sequel to the former that was dedicated to the study of new designs for hardware components that can provide truly flexible and energy efficient multi standard transceivers. This chapter completes this study by focusing on energy efficient power amplifier design. We consider three innovative designs, to operate at varying operating frequencies, covering the frequency bands 400 MHz, 1,920 MHz and 3.5 GHz. The proposed RF Power Amplifiers show considerable enhancements compared to the state of the art existing technologies.