Analysis and evaluation of harmonic suppression of lumped-element networks suitable for high-frequency class-E operation condition approximation

The harmonic output of microwave lumped-element class-E load-coupling topologies is assessed. Measurement results on fabricated C-band class-E power amplifiers with either a modified lowpass and an optimised second-harmonic impedance network show that the latter provides better performance not only in terms of output power, gain and efficiency, but also in regard to harmonic suppression. Compared with the common modified lowpass network, harmonic content in the load of the optimised second-harmonic impedance topology at the second-, third- and fourth-harmonic frequencies are lower by more than 5.8, 10 and 5.8 dB, respectively.