Adaptive Power Management of Linear RF Power Amplifiers in Mobile Handsets – An Integrated System Design Approach

Energy-efficient, linear RF power amplifiers (PAs) are critical for achieving longer battery life in state-of-the-art radio transceivers because typically they determine and dominate the power consumption of the system. In this paper, an adaptive power management scheme using a novel dual-mode, noninverting, buck-boost converter targeted for code-division-multiple-access (CDMA) RF PA is presented. The control scheme dynamically adjusts the PA supply voltage using a noninverting buck-boost converter, and bias current as a function of the transmitter’s output power thereby reducing the quiescent power loss and improving the system efficiency. The use of a dual-mode converter enables the PA system to operate with high efficiency over a wide loading range, which translates to an improvement in battery life. This paper also presents several alternate control strategies that simplify the buck-boost converter accuracy requirements and transmitter gain adjustment circuit design, which directly translates to a reduction in the system’s design complexity thereby saving silicon and PCB real estate. A comparative evaluation of the control methods considering the average efficiency of the system reveals that a three-step and an approximate continuous 1-dB power control schemes result in comparable efficiency enhancement with respect to the accurate continuous control method while offering simpler solutions.