New analytical design equations for maximum drain efficiency of Class-E power amplifiers including the on-resistance of the transistor

In the analysis of ideal Class-E power amplifier, zero switch resistance is assumed and zero-voltage-switching/zero-derivative-switching conditions are used to optimise the design. Neglecting the finite switch resistance due to increased complexity can result in nonoptimum performance. In literature, analysis of the effect from switch resistance is based upon the same ZVS/ZDS conditions used for ideal Class-E. In this work, a new criterion is proposed to optimise the design, considering the resistive losses of the switch. PAs with component values based upon this condition provides higher drain efficiency than those using ZVS/ZDS conditions. Analytical equations are given to directly determine the optimum values for the load network. The results are verified by simulation in ADS using a lossy resistive switch model. The closed-form analysis matches very well with ADS simulation.