The Continuum of Load Modulation Ratio From Doherty to Traveling-Wave Amplifiers

This article proposes a unified theory on power combining with a continuum of load modulation (LM) ratios. Two well-known power amplifier (PA) techniques, Doherty and traveling-wave amplifiers, are the two extreme examples within this continuum, yielding full and zero LMs, respectively. Based on this theory, a power-combining technique is proposed, which optimizes efficiency and bandwidth at a certain power backoff (BO) level, which is often in between the two well-known architectures. As a demonstration, a PA with an LM ratio of 1.4 is designed. It achieves a peak output power of 49.3±0.5 dBm and 47%-60% drain efficiency at 8-dB power BO over 2.6-3.8 GHz. The linearizability and practical usefulness of this PA are demonstrated through linearized-modulated measurements.