Novel wideband GaN HEMT power amplifier using microstrip radial stub to suppress harmonics

In this paper, a novel wideband GaN HEMT power amplifier (PA) using microstrip radial stub (MRS) in both input and output matching networks to suppress harmonic components of 2.14 GHz is analyzed, fabricated, and tested. The angle subtended by MRS and the bottom length of MRS are analyzed for harmonic suppressing purpose. The wideband harmonic suppressing characteristic of MRS is compared with normal 50 Ohm quarter-wave rectangular stub. The second and third harmonics of 2.14 GHz are suppressed by −38.37 dB and −29.53 dB, respectively. −15 dBc suppressing bandwidth over 1.32 GHz at both harmonic bands is obtained. By using the proposed MRS in both input and output matching network, the measured maximum power added efficiency (PAE) is 80.52% with 40.53 dBm output power at 2.14 GHz. At least 50% PAE and 37 dBm output power over a 12% bandwidth from 2 GHz to 2.26 GHz is achieved. The maximum gain is 20.25 dB.