What is the waveform engineering approach to power amplifier design?

The waveform engineering approach to power amplifier design is a systematic methodology that designs the output matching network to shape the transistor's drain voltage and current time-domain waveforms for optimal efficiency, power, and linearity, rather than simply matching impedances at the fundamental frequency. The approach involves: measuring or simulating the transistor's intrinsic drain voltage and current waveforms under different load impedance conditions (using load-pull measurements or nonlinear circuit simulation to map the waveforms at the current-generator plane inside the transistor, de-embedding the package and parasitic elements), identifying the optimal waveform shapes for the desired PA class (for Class F: square voltage, half-sine current; for Class E: shaped voltage with ZVS; for continuous Class F: a family of waveforms that maintain high efficiency across a bandwidth; for continuous Class J: a waveform that allows reactive output impedance while maintaining efficiency), designing the output matching network to present the required impedances at the fundamental, 2nd, and 3rd harmonics (the network must simultaneously present: the optimal fundamental impedance (from load-pull), the correct 2nd harmonic impedance (short, open, or specific reactive value depending on the PA class), and the correct 3rd harmonic impedance), and using the continuous mode design space (modern waveform engineering exploits the continuous modes (Class B/J, continuous Class F) where a range of reactive harmonic impedances all yield the same efficiency; this provides design freedom to achieve wider bandwidth while maintaining high efficiency). The waveform engineering approach produces PAs with 5-15% higher efficiency and wider bandwidth than traditional impedance-matching approaches.