Highly efficient wideband harmonic-tuned power amplifier using low-pass matching network

This paper presents a design approach for a broadband and high efficiency harmonic-tuned power amplifier (PA) based on a low-pass filtering (LPF) matching network (MN). The MN is composed of quasi-lumped open stubs (λ
_g
/8<;l<; λ
_g
/4). Compared with widely used conventional Chebyshev LPF matching networks, the proposed output matching network provides a good approximation of desired lumped elements over the entire frequency band. The MN offers a sharp roll-off to the transition band. Optimum fundamental and second harmonic load impedances are obtained by identifying the high efficiency regions on the reactance plane for second harmonic band placement, the design is reduced to a fundamental matching problem. A PA with this concept is designed from 1.0 to 1.5 GHz (FBW=40%) using a Cree GaN HEMT CGH40045. The peak output power, drain efficiency, and gain are 47.3 dBm, 80%, and 12.6 dB, respectively at 1.2 GHz. Furthermore, the PA is evaluated using a COFDM signal with an average output power of 40 dBm, a peak-to-average ratio (PAPR) of 10 dB, and a bandwidth of 2.5 MHz. The PA can achieve a peak drain efficiency of 49% and the adjacent channel power ratio (ACPR) of -26.3 dBc at 1.3 and 1 GHz.