On the class-F power amplifier design

Power-amplifier class-F operation is investigated and revised, evidencing t he fundamental importance of the harmonic-generating mechanism and the limi tations imposed by the device input and output nonlinearities on the ideal class-F behavior. Closed-form expressions are derived for the major design quantities, together with the optimum fundamental and third-harmonic loadin g of the active device. A design procedure, making use of the derived expre ssions, is presented and the deviations from the ideal behavior are discuss ed. Sample designs, making use of a fall nonlinear device model and commerc ial analysis software, are carried out to demonstrate the effectiveness of the analysis and the design procedure. It is shown, both analytically and u sing commercial nonlinear simulations, that blind application of commonly u sed, idealized class-F harmonic terminations can cause unexpected detriment al results. (C) 1999 John Wiley & Sons, Inc.