I. Introduction
The Class-E power amplifier (PA) is a highly nonlinear amplifier, introduced by Sokal in 1975, [1]. Being a switching power amplifier, it has higher efficiency at high output power levels than a conventional linear power amplifier (Class A, B, AB). Theoretically (using an ideal switch) the efficiency of a Class-E amplifier can reach 100% due to the fact that nonzero values of switch voltage and current do not occur simultaneously, leading to zero power dissipation within the switch.