Linearity Enhancement for the RF Class-E Power Amplifiers Using Duty-Cycle Modulation at the Feed-Forward Path

A linearity improved class-E power amplifier using duty-cycle modulation(DCM) is proposed at 2.4 GHz. The main class-E amplifier is combined with the auxiliary duty-cycle modulated class-E amplifier to enhance the linearity with suppressing the harmonics. The duty-cycle modulation is employed for the auxiliary amplifier to generate harmonics which cancel the main amplifier´s harmonics at the combiner. It is important to create the harmonics needed to suppress the main amplifier´s harmonics by controlling gate voltage of the auxiliary amplifier. The measured maximum output power at the fundamental frequency shows 28.8 dBm, whereas the PAE shows 53 % with 14 dBm input power excited. The ACPR is improved by 12 dB compared to that of the class-E amplifier without duty-cycle modulation.