Class-F and inverse class-F power amplifier loading networks design based upon transmission zeros

In practical implementations, class-F amplification is achieved based upon the second and/or third harmonic control provided by the output matching network. This paper presents a design method based upon inserting finite-frequency transmission zeros to a lumped-element matching network at the harmonic frequencies of interest. A two-section impedance matching network is transformed to either a class-F_2,3 or inverse class-F_2,3 loading network. The manipulation of transistor parasitics is described using network transformations. The resultant loading networks serve as fundamental-frequency matching and harmonic tuning simultaneously while reducing the number of components and circuit size. The simulated results show the expected wave shaping and drain impedances. The prototype amplifiers achieve 81% and 79% efficiency for the class-F and inverse class-F, respectively, at 42.32 and 42.37 dBm output powers at 300-MHz fundamental-frequency.