Lossless Inductor Current Control in Envelope Tracking Supply Modulator with Self-Allocation of Energy for Optimzation of Efficiency and EVM

Abstract

conventional hybrid supply modulator for envelope tracking (ET) technique requires the linear amplifier to track a RF envelop signal with the help of switching converter to provide average power for high efficiency. Any distortion caused by resistive and inaccurate current sensing will result in increase of power loss and Error Vector Magnitude (EVM). Thus, a lossless inductor current control (LICC) with a closed-loop self allocation technique is proposed to increase efficiency and decrease the EVM. Inductor current ripple information is directly extracted from the gate drive signal of a class-AB linear amplifier and a weighted self-allocation control is applied to optimize for efficiency and EVM. Extra power improvement of 2.5% can be derived. Owing to the removal of a power consuming sensing resistor in conventional design, the efficiency can be effectively improved. The proposed supply modulator is capable of delivering an instantaneous peak power of 3.36W and a bandwidth of 20MHz with an averaged efficiency up to 85%.