Efficiency Enhancement Technique for Outphasing Amplifier With Extended Power Back-Off Range

The article proposes a modified series compensation (MSC) outphasing power amplifier (OPA) that maximizes saturation output power and extends power back-off range. The proposed OPA enables achieving output power back-off (OBO) compensation without affecting the saturation matching. Then, the circuit structure is simplified by introducing a post-matching circuit to integrate the combiner and the reactive compensation network (RCN). Moreover, a simplified dual-impedance matching network (DIMN) is placed between each transistor and the output combiner, leading to increased OBO range with improved efficiency. This technique not only takes into consideration the influence of parasitic parameters but also match the required impedance at both saturation and OBO points, simultaneously. The above design idea is successfully verified by using the gallium nitride (GaN) high-electron-mobility transistor (HEMT) to develop an OPA circuit operating at 2.6 GHz, providing 45.2 dBm of peak output power. At the 12-dB output back-off point, the drain efficiency reaches 61.5%. In addition, the prototype achieves values of the adjacent channel leakage ratio (ACLR) equal to -48.17 dBc and 47.74 dBc for LTE modulated signal with 8 dB PAPR value and for 5G NR signal with 11.7 dB PAPR value, respectively.