Broadband GaAs HBT Doherty Power Amplifier for 5G NR Mobile Handset

• Published in: IEEE transactions on circuits and systems. II, Express briefs Vol. 71; no. 2; pp. 527 - 531
• Main Authors: Bo, Shao Fei, Ou, Jun-Hui, Peng, Yan Jun, Xuan, Kai, Xu, Jin-Xu, Zhang, Xiu Yin
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.02.2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: 5G mobile communication; 5G NR handset; Amplification; Broadband; broadband amplifier; Cell phones; Circuit faults; Continuous radiation; Couplings; Doherty power amplifier; GaAs HBT; Impedance; Inductors; Laminates; Power amplifiers; Power splitters; Quadratures; transformer; Transformers
• ISSN: 1549-7747; 1558-3791
• DOI: 10.1109/TCSII.2023.3291528

This brief proposes a broadband flat-gain Doherty power amplifier (DPA) for 5G new radio (NR) mobile handsets. It is implemented by the heterogeneous integration of GaAs HBT process for PA die and 6-layer laminate for output network. To realize wideband Doherty-operation, an on-laminate transformer with three <inline-formula> <tex-math notation="LaTeX">\pi </tex-math></inline-formula>-shaped networks is designed. Meanwhile, the parallel coupling of on-chip spiral inductors is introduced into input quadrature power splitter and interstage matching network to extend bandwidth and reduce size. Mechanism of the proposed DPA is analyzed and a prototype is implemented for verification. For continuous-wave (CW) signal, saturation power of 36-dBm and comparable peak power added efficiency (PAE) of the DPA at 3.3, 3.75 and 4.2 GHz are realized. Within the 6-dB power back-off (PBO) range, the measured PAE is higher than 27%. Flat gain within n77 band (3.3 - 4.2 GHz) is obtained, varying from 25.8 dB to 27.2 dB. Under the excitation of 5G NR 100-MHz QPSK signal, the proposed DPA delivers a PAE of 26.2% - 30.3% with the averaged output power of 30 dBm in n77 band. The corresponding lower and upper adjacent channel leakage ratios (ACLRs) are measured from −32.1 dBc to −36.5 dBc without digital pre-distortion (DPD). The size of die is <inline-formula> <tex-math notation="LaTeX">1.34\times1.44 </tex-math></inline-formula> mm2, and the occupied core area of laminate is <inline-formula> <tex-math notation="LaTeX">1.69\times3.85 </tex-math></inline-formula> mm2.