Investigating Continuous Class-F Power Amplifier Using Nonlinear Embedding Model

This letter investigates the design space for feasible load impedances of broadband continuous class-F power amplifier (PA) using the nonlinear embedding transfer function. This can overcome the limitation of anticlockwise trajectory of second-harmonic impedance on Smith chart. The approach starts with the design at intrinsic plane based on generic representation of drain voltage and current waveforms. Nonlinear embedding transfer network is then used to project intrinsic loads to the package plane. The proposed design strategy is verified with the implementation of a 15-W GaN HEMT-based PA operating over the frequency range of 1.5 to 2.5 GHz with drain efficiency between 60%-75%. This corresponds to the fractional bandwidth of 50%.