Harmonic suppression performance of a 5GHz MMIC class-E PA using a lowpass lumped-element impedance termination approximation

Lowpass lumped-element load coupling network approximation of class-E switching conditions are very common at microwave frequencies, where the classic approach is not feasible. Although such modified lowpass networks are a valuable approach in approximating class-E efficiency at microwaves, harmonic suppression of these networks has to be considered closely together with switching-mode circuits. This paper assesses experimentally the harmonic output of a fabricated monolithic microwave integrated circuit (MMIC) C- band class-E power amplifier (PA) utilising a modified lowpass load transformation topology. Measurements show that harmonic output of the class-E PA based on such a network without additional filtering is -19.1 dBc, -30.5 dBc and -38.5 dBc for the second, third and fourth harmonic frequency components, respectively.