High-Efficiency RF-PA Supply Modulation Techniques for mm-Wave Amplifiers
As the complexity of mobile handset hardware is increasing, the battery operating time becomes very important. The front-end power amplifier (PA) is one of the most power-consuming devices in the cellular handset, so there have been many efforts to improve the PA efficiency. In order to increase the PA efficiency, highly-efficient PA supply modulation schemes such as an envelope tracking (ET) or average power tracking (APT) have been widely researched in both industry and academia. To enable the envelope tracking PA, a supply modulator (SM) IC, which has high efficiency, wide signal bandwidth, fast transition time, and low output noise, is required. This tutorial will provide an overview of the envelope tracking system and switched-mode circuit techniques for 2G/3G/LTE/5G. Furthermore, in order to manage the power effectively in millimeter-wave amplifiers, a special supply modulation technique named symbol-power tracking (SPT) is introduced.