Optimized envelope tracking operation of Doherty power amplifier

Abstract

This paper presents an optimized envelope tracking operation of Doherty amplifier. By modulating the supply voltage of the carrier amplifier, while that of the peaking amplifier is fixed, the supply modulator provides just a half of the current for the same PA output power. It results in a reduced chip size and the crest factor of the supply modulating signal is reduced by 6dB, enhancing the efficiency of the supply modulator. The designed ET transmitter consisting of the Doherty amplifier and the supply modulator are fabricated in 2um HBT and 0.13um CMOS processes, respectively. It presents the efficiency improvement over a broad output power region. Especially, at the 16dB backed off power level, more than 23% of PAE is achieved. For WiBro application, it shows the PAE of 38.6% at the output power of 24.22dBm with the gain of 24.62dB. The EVM is 3.64%.