The Power Smith Tube: Joint optimization of power amplifier input power and load impedance for power-added efficiency and adjacent-channel power ratio

A new visualization tool for design is introduced: the Power Smith Tube. It provides aid in designing for optimum power-added efficiency (PAE) while meeting adjacent-channel power ratio (ACPR) requirements. The Power Smith Tube is a three-dimensional cylindrical extension of the Smith Chart with input power as the vertical axis. As such, this Smith Tube allows the visualization of design metrics, such as PAE and ACPR, as a function of both input power and load impedance. Performance of load-pull measurements or simulations at multiple values of input power provides data for the design. Design examples using the Power Smith Tube based on both simulation and measurement data are presented to demonstrate selection of load impedance and input power providing the highest PAE under ACPR constraints.