Design of HEMT GaN power amplifiers with wideband control of 2nd harmonic impedances in S-Band

This paper reports the design and measurement of a GaN power amplifier whose output loads are optimised at fundamental and 2^nd harmonic over a wide bandwidth (20%) in S-Band to reach maximum power added efficiency (PAE). The design methodology is described in the paper. Two power amplifiers have been built. The first one is optimized at fundamental and 2^nd harmonic while the other one is only optimised at fundamental. Comparisons of power measurement results demonstrate the interest of optimising load impedances at the 2^nd harmonic over large bandwidths for GaN HEMTs. When loaded by the matching circuit optimised at the 2^nd harmonic, the packaged GaN exhibits 23.4Watts (9.7W/mm) output power associated to 15.2dB power gain and 69% PAE at the low frequency of the bandwidth (fmin). The paper also proposes a new matching architecture at 2^nd harmonic frequency.