A 2-GHz GaN HEMT Power Amplifier Harmonically Tuned Using a Compact One-Port CRLH Transmission Line

A compact harmonic tuning network (HTN) using a composite right-/left-handed (CRLH) transmission line (TL) is introduced. The CRLH TL offers purely imaginary harmonic load impedances, as it essentially functions as a one-port circuit at the harmonic frequencies, owing to a harmonics trap filter. In comparison to conventional HTNs based on microstrip line (MSL) or hybrid MSL and CRLH TL technologies, the proposed HTN features remarkable compactness while accommodating various operating classes of amplifiers. As a proof of concept, a 2-GHz 10-W gallium nitride (GaN) high electron mobility transistor (HEMT) power amplifier (PA) was fabricated, demonstrating drain efficiency of 84.6% and power added efficiency (PAE) of 78.4%. The novel HTN is expected to find applications in PAs for transmitter systems, where high efficiency and a minimal circuit footprint are of paramount importance.