A Comparative Study of Power Amplifiers' Sensitivity to Load Mismatch: Single Branch vs. Doherty Architectures

This paper proposes a comparative study of the sensitivity of different power amplifiers architectures to load mismatch. The two considered architectures are a single branch class AB power amplifier, and a multi-branch architecture using the Doherty dynamic load modulation technique. Two LDMOS based power amplifiers operating around 1.95 GHz are used. The magnitude of the load reflection coefficient is varied from 0 to 0.2 in steps of 0.05. For each of these values, the phase of the load reflection coefficient is swept over 360° in steps of 45°. The amplifiers' linearity and power added efficiency variations with the load reflection coefficients are evaluated. It is found that the Doherty amplifier is less sensitive to load mismatch than a single branch class AB amplifier in terms of its efficiency performance. However, the linearity performance of the single branch class AB amplifier is less sensitive to the load mismatch than that of the Doherty amplifier.