2.4 GHz Class- $\text{F}^{-1}$ GaN Doherty Amplifier With Efficiency Enhancement Technique

An enhancement in the efficiency of an inverse Class F (Class <inline-formula> <tex-math notation="LaTeX">$\text{F}^{-1})$ </tex-math></inline-formula> Doherty power amplifier (DPA) using a proposed triple-level supply modulator (SM) is presented. A three-level SM provides a lower supply voltage at a low input voltage, while providing the maximum level beyond the power back off. By adjusting the supply voltage in terms of the magnitude of the input signal, the efficiency of the main amplifier of the DPA over a wide input range is extended. For verification, a 2.4-GHz GaN Class <inline-formula> <tex-math notation="LaTeX">$\text{F}^{-1}$ </tex-math></inline-formula> DPA was designed and fabricated. Using a 10 MHz 8.6 dB peak-to-average power ratio signal, at an average output power of 34.1 dBm, the fabricated Class <inline-formula> <tex-math notation="LaTeX">$\text{F}^{-1}$ </tex-math></inline-formula> DPA achieves an efficiency level of 49%, which is 7.1% higher than that of a conventional amplifier. Under this condition, the measured adjacent channel leakage ratio (ACLR) is below −30 dBc.