An octave bandwidth Class-J power amplifier with second harmonic termination control

A purely passive design technique for a class-J power amplifier (PA) is proposed, based on complex terminations at the fundamental frequency and the second harmonic, which increases the bandwidth while maintaining high efficiency. Using combined analytical derivation and numerical simulations, the drain impedance termination locus curve is obtained in the drain efficiency and DC voltage spaces. Successive application of the newly proposed de-normalization technique avoids the drain DC voltage manipulation used elsewhere. This is due to the resulting variable reactance of the output drain-source capacitor, optimal over a wide frequency range. Following the proposed procedure and the obtained optimal parametric space, a GaN HEMT-based PA is designed, fabricated, and tested displaying a very good agreement of the predicted and measured results.