T03.3 - Inverse Class-H Power Supply Modulator for Envelope Tracking Applications

The Envelope Tracking (ET) technique enhances the power efficiency of Radio Frequency (RF) Linear Power Amplifiers (LPAs) by dynamically adjusting their supply voltage according to the amplitude of the signal to be reproduced. Given the high Peak-to-Average Power Ratio (PAPR) of modern communication signals, the supply modulators used in ET schemes must be designed to ensure high power efficiency across a wide range of supply voltage levels and bandwidths in the order of megahertz. High-bandwidth Switching-Mode Power Converters (SMPCs) have been typically proposed for this task, although their power efficiency can be compromised in the low-power range, particularly in high-power RF applications. This work presents the inverse Class-H modulator, a new bias-modulation strategy focused on improving the overall efficiency of supply modulators in high-power RF applications. Moreover, a topology especially conceived for implementing this novel technique is also described. The idea is validated with an experimental prototype designed considering an LPA with a 50 V maximum supply voltage reproducing a 11 dB-PAPR signal, and a peak supply power of 250 W.