On the design of MMIC multi-harmonic load terminations for class-F amplifiers

In this paper, four multi-harmonic transmission-line load networks suitable for class-F amplifiers are analysed and compared in terms of harmonic suppression and their effects on output power and efficiency. Based on this study a design of a monolithic microwave integrated circuit (MMIC) class-F amplifier has been carried out at K-band. The fabricated amplifier achieves state-of-the-art efficiency. Moreover, without the need of supplementary filtering sections, harmonic suppression is better than -25 dBc for operation well into compression. To the best knowledge of the authors, this is the first experimental verification of harmonic suppression of transmission-line load networks suitable for class-F tuning