Combining Class J and Inverse Class F Continuous Modes for a Highly Efficient Broadband Power Amplifier

This paper explores the use of waveform engineered continuous modes with the aim of achieving a broadband Radio Frequency Power Amplifier (RF PA) with a high average efficiency across its operating bandwidth. The effect a High Electron Mobility Transistors (HEMTs) knee voltage can have on achievable drain efficiency of Class J and Continuous Inverse Class F (CCF ⁻¹ ) is presented. Drain efficiency can be as low as 60% for Class J and 82% for CCF ⁻¹ when considering a real device such as a GaN HEMT. This paper therefore proposes the combination of Class J and CCF ⁻¹ modes for achieving high average efficiency across the bandwidth of operation of a PA. This combination of modes is verified with the design and manufacture of a 10W PA using a Wolfspeed CGH40010F GaN HEMT. The realised PA achieves a power output of between 39.5 – 42.2dBm with a drain efficiency between 68.8–82.9 %. A high average efficiency of 76.4% is achieved across the 2.1–3.6 GHz operating bandwidth of the PA.