摘要
This article presents and compares high-performance X-band continuous-mode GaN monolithic microwave integrated circuit (MMIC) power amplifiers (PAs) utilizing Class-F (CCF) and inverse Class-F modes (CCF−1) in 0.25- μ m GaN-on-SiC high electron mobility transistor (HEMT) technology. A π -type equivalent network is proposed to compensate the transistor output parasitic capacitance for obtaining high harmonic matching impedances. Considerations and challenges for continuous-mode design, especially for achieving a wide bandwidth (BW), have been discussed in detail. Broadband matching networks with low loss are investigated by accounting for varying optimal impedances at different frequencies and power levels. Measured results show that the CCF PA achieves a 3-dB BW f_(-3 \text dB) from 8.5 to 11.4 GHz (29.1%) and a maximum gain of 23 dB, while the CCF−1 PA demonstrates a f_(-3 \text dB) of 8.3-11.2 GHz (29.7%) with a peak gain of 24 dB. Also, the CCF PA attains a larger P_(𝐬𝐚𝐭) of 38.6 dBm, while the CCF−1 PA reaches a higher peak PAE of 44.3%. Compared to the previously published 0.25- μ m GaN MMICs with harmonic tuning in a similar frequency range, both designs achieve the fractional BW and FoMs among the best. In addition, the CCF−1 PA shows a further improved FoM compared with the CCF design.