Antenna Impedance Variation Compensation by Exploiting a Digital Doherty Power Amplifier Architecture

This paper presents a comprehensive theoretical study on Doherty power amplifiers (PAs) under antenna impedance mismatch. It is demonstrated for the first time that by varying the relative gain and phase of the carrier and peaking amplifiers, the PA performance degradation caused by the antenna impedance mismatch can be largely compensated. Such a compensation effect is discussed extensively for different antenna impedance conditions. Four types of Doherty PAs, i.e., three digital Doherty PAs with different degrees of flexibility and the classical analog Doherty PA, are covered in the complete theoretical analysis. To intuitively show the proposed concept, this paper presents numerical simulation results based on the theoretical analysis. In addition, measurement results on a fully integrated digital Doherty PA implemented in 65-nm bulk CMOS are demonstrated to verify our theoretical study.