A 0.6-2.1-GHz Wideband GaN High-Power Amplifier Using Transmission-Line-Transformer-Based Differential-Mode Combiner With Second-Harmonic Suppression

A wideband gallium nitride (GaN) power amplifier (PA) using a four-way planar differential-mode combiner (DMC) with impedance transformation function based on the transmission line transformer (TLT) technique was fabricated. The performance was compared with a PA using a four-way planar common-mode combiner (CMC), which was recently reported. The fabricated PA with the CMC exhibited an average output power ( P_{\mathrm{ out}} ) of 233 W and an average power-added efficiency (PAE) of 42% in the frequency range of 0.5-2.1 GHz. The fabricated PA with DMC exhibited an average P_{\mathrm{ out}} of 282 W and an average PAE of 48% in the frequency range of 0.6-2.1 GHz, which is superior to the PA with CMC. Moreover, the fabricated PA with DMC exhibited a large second-harmonic suppression. The maximum suppression is −54 dBc at 1.5 GHz, and the average of the suppression from 0.6 to 2.1 GHz is −38.3 dBc.