Analysis, Design Optimization and Performance Comparison of Bias Adapted and Asymmetrical Doherty Power Amplifiers

Doherty type Power Amplifler (DPA) design is one of the most practical e-ciency enhancement methods that provide moderate linearity. Asymmetrical device usage and employment of bias adaptation are among the most commonly used Doherty architectures in recent applications. In this paper, the e-ciency performances of bias adapted DPA and asymmetrical DPA are compared based on the e-ciency expression that is derived in terms of the conduction angle. The e-ciency of bias adapted DPA is analyzed in terms of conduction angle of the peaking device; various bias waveforms are proposed and their efiects on enhanced e-ciency performance are demonstrated. This paper also facilitates an approach to determine the required relative periphery of the peaking amplifler in order to have a fully load modulated asymmetrical DPA. Both DPA structures are designed and implemented at the output power of 50dBm with nearly 60% drain e-ciencies in 6dB load modulation region. The measurements verify the better e-ciency characteristics of the bias adapted DPA and asymmetric DPA in comparison to the conventional DPA. For the flrst time in the literature, as a fair comparison, the performances of asymmetrical DPA and bias adapted DPA are compared on the same platform and their advantages as well as drawbacks are demonstrated using measurement results.