High-Efficiency Power Amplifier Using an Active Second-Harmonic Injection Technique Under Optimized Third-Harmonic Termination. - Mincheol Seo; Hwiseob Lee; Jehyeon Gu; Hyungchul Kim; Junghyun Ham; Wooyeol Choi 001; Yanghun Yun; Kenneth K. O; Youngoo Yang (IEEE Trans. Circuits Syst. II Express Briefs, 2014)