Analog Linearization of an RF PA Using Baseband Feedback and Power Gate Tracking

The advent of 5G has introduced more complicated modulation schemes that produce signals with high peak-to-average power ratios. Requirements on linearity for wideband signals are becoming more crucial. However linearity is not the only critical parameter, efficiency is a key feature in many applications. The power consumed within the RF amplifier impacts the efficiency of the whole communication systems, increasing the need for cooling and limiting the battery lifetime for handset devices. Achievement of high efficiency typically has a negative impact on the linearity of the power amplifier, which in turn introduces nonlinear distortion components on the transmitted signal. A common solution in communication systems is to push for efficiency and then employ one or more linearity enhancement schemes to correct the signal. Among these schemes digital predistiotion (DPD) is a popular one for its effectiveness in correcting the signals’ distortion. Not without consequences though; due to memory effects DPD has limitations when it comes to bandwidth. With growing demand on wideband communication analog linearization methods appear very attractive. This thesis presents the effects of baseband feedback as an alternative to linearization by digital predistortion. In addition, the thesis work explores the possibility of enhancing linearity by tracking the power of the envelope at the gate. The activities carried out include simulation, implementation and measurements.