X-Band GaN Power Amplifier MMIC with a Third Harmonic-Tuned Circuit

This paper presents an X-band GaN HEMT power amplifier with a third harmonic-tuned circuit for a higher power density per area and a higher power-added efficiency (PAE) using a 0.25 m GaN HEMT process of WIN semiconductors, Inc. The optimum load impedances at the fundamental and third harmonic frequencies are extracted from load-pull simulations at the transistor's extrinsic plane, including the drain-source capacitance and the series drain inductance. The third harmonic-tuned circuit is effectively integrated with the output matching circuit at the fundamental frequency, without complicating the whole output matching circuit. The input matching circuit uses a lossy matching scheme, which allows a good return loss and a simple LC low-pass circuit configuration. The fabricated power amplifier monolithic microwave integrated circuit (MMIC) occupies an area of 13.26 mm(2), and shows a linear gain of 20 dB or more, a saturated output power of 43.2-44.7 dBm, and a PAE of 35-37% at 8.5 to 10.5 GHz.