Broadband InGaP/GaAs HBT Doherty Power Amplifier IC Using Direct Interstage Power Division for Compact 5G NR Handset Module

• Published in: IEEE access 2023-01, Vol.11, p.1-1
• Main Authors: Oh, Hansik, Shin, Jaekyung, Jeon, Hyeongjin, Woo, Young Yun, Hwang, Keum Cheol, Lee, Kang-Yoon, Yang, Youngoo
• Format: Article
• Language: English
• Subjects: 5G new radio; Amplification; Bandwidths; Broadband; Circuit design; differential power amplifier; direct power division; Doherty power amplifier; Electrical loads; Equivalent circuits; Frequencies; Gallium arsenide; Gallium indium phosphide; Impedance matching; Inductance; InGaP/GaAs HBT; Integrated circuits; Modulation; Power amplifiers; Power gain; Radio signals; Reactance; Receivers & amplifiers; transformer-less interstage; Transformers; Transmission lines
• ISSN: 2169-3536; 2169-3536
• DOI: 10.1109/ACCESS.2023.3256079

This paper presents a 2.8-3.8 GHz broadband 2-stage fully differential Doherty power amplifier using direct interstage power division based on a 2-μmInGaP/GaAs HBT process for 5G new radio handset applications. A compact transformer-less interstage network is proposed for direct power division for carrier and peaking amplifiers. The power division ratio at the interstage is designed to dynamically vary according to the input power level to provide higher power gain and desired load impedance modulation. By utilizing the non-linear input reactance of the peaking amplifier, broadband dynamic power division circuits were designed for an operating frequency band of as broad as 1 GHz. In addition, active bias circuits for the peaking amplifier were optimized to have sufficient gain expansion, so that the overall AM-AM characteristics is as flat as possible. A broadband load modulation network using one transformer and two quarter-wave transmission lines is proposed. For the off-chip output transformer, impedance trajectory for the wide band impedance matching is presented using a T-equivalent circuit of the transformer. The self-inductance ratio of the transformer is optimized to maximize the bandwidth. Using the 5G new radio uplink signal with a signal bandwidth of 100 MHz, the implemented Doherty PA IC exhibited a power gain of 31.9 to 38.4 dB, PAE of 22.0 to 30.6%, and average output power of 26.0 to 27.8 dBm at a given ACLR of -33.0 dBc without pre-distortion.