Sequential Load-Pull Technique for Multioctave Design of RF Power Amplifiers

A design methodology for multioctave RF power amplifiers (PAs) is presented in this brief using sequential harmonic characterization. The investigation of in-band harmonics on the multioctave performance of the RF PA shows that a more optimal performance can be achieved using the proposed technique compared to the conventional load-pull. To demonstrate the capability of this technique, a broadband multioctave PA prototype was designed and fabricated using sequential second harmonic characterization. The fabricated prototype uses a GaN HEMT from Cree Inc. and exhibits a drain efficiency of 53%-64% in the range of 0.7-4.0 GHz while having an output power of 37.5-39.1 dBm corresponding to the fractional bandwidth of 140%. Measurement results validate the proposed method as a robust PA design procedure for broadband and multistandard applications.