Design of Highly Linear Broadband Continuous Mode GaN MMIC Power Amplifiers for 5G

In this paper, we present a design approach for broadband harmonic-tuned monolithic microwave integrated circuit (MMIC) power amplifiers (PAs). Two harmonic matching networks are proposed for the realization of continuous class-B and class-F modes in an integrated PA. A design procedure is developed for integrated PAs using these matching networks to achieve high linearity, broadband operation, and compact chip area, in the presence of parasitic components and the physical limitations of the MMIC process. Two proof-of-concept fully integrated PAs are implemented in a 0.25-μm GaN-on-SiC process. Output power of 34.2-36.4 dBm with 40% to 49% power-added efficiency (PAE) is achieved in 4.2-7.0 GHz (51.6% fractional bandwidth), from the continuous class-B PA with only 1.5-mm² chip area. Furthermore, the continuous class-F PA achieves 36.2 dBm output power and 52% PAE at 5.0 GHz. The PAs are also characterized using QAM signals with wide bandwidth, in order to evaluate their performance for 5G wireless applications. For a 64-QAM signal with 100-MHz bandwidth and 8 dB peak-to-average power ratio (PAPR), the continuous class-B PA achieves 29.3 dBm average output power, 28% average PAE, and -25 dB (5.5%) error vector magnitude (EVM). The continuous class-F PA, tested using a 200 MHz 256 QAM signal with 8.5 dB PAPR, provides an average output power of 28.5 dBm, average PAE of 27%, and -28 dB (4%) EVM, without any pre-distortion.