A 2–18-GHz Frequency-Reconfigurable GaN Power Amplifier With More Than 33% Average Power Added Efficiency

A 2–18-GHz frequency-reconfigurable power amplifier (PA) with a measured average power added efficiency (PAE) of more than 33% is presented in this article. To realize the continuous wideband coverage of 2–18 GHz while avoiding the Bode-Fano limit, the proposed PA divided the full frequency band of 2–18 GHz into three continuous frequency subbands with each band covered by a sub-PA. Since each sub-PA works in a transient bandwidth that is only a fractional part of the full frequency band, it will have much higher efficiency and gain. The three sub-PAs can be merged or combined by using a reconfigurable matching network and a reconfigurable combining network so that they can be flexibly reconfigured between three frequency subbands. Based on this strategy, the proposed PA consists of a reconfigurable low-band (LB) sub-PA1 covering 2–10 GHz and a wideband high-band (HB) sub-PA2 covering 10–18 GHz. To effectively combine the two sub-PAs and eliminate the loading effect from each other, a reconfigurable output combining network and a reconfigurable input matching network were proposed. With the proposed structure, the loading effects from the inactive sub-PA to the active sub-PA can be minimized and used as a part of impedance matching to optimize the PA performance. The PA with wideband coverage and high efficiency can be simultaneously achieved using the proposed reconfigurable technique. To demonstrate the proposed techniques, a reconfigurable PA with continuous frequency coverage from 2 to 18 GHz is designed and fabricated in a 0.15-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m gallium nitride (GaN) technology. The resulting PA has been demonstrated to have a measured average PAE of 34% across the ultrawideband range of 2–18 GHz, a peak PAE of 42.8% at 10 GHz, and the measured saturation output power Psat ranges from 31.3 to 34.9 dBm.