IEEE Access (Jan 2022)

Generalized Expression and Design Method of Modified Load Networks for Doherty Power Amplifier With Extended Back-Off Range

  • Yifei Chen,
  • Woojin Choi,
  • Jaekyung Shin,
  • Hyeongjin Jeon,
  • Sooncheol Bae,
  • Young Chan Choi,
  • Seungmin Woo,
  • Young Yun Woo,
  • Hansik Oh,
  • Kang-Yoon Lee,
  • Keum Cheol Hwang,
  • Youngoo Yang

DOI
https://doi.org/10.1109/ACCESS.2022.3193227
Journal volume & issue
Vol. 10
pp. 77487 – 77497

Abstract

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This paper presents a generalized expression of the modified load networks (MLNs) for Doherty power amplifiers (DPAs) with an extended output power back-off (OBO) range. Based on the analysis using this new expression, a new circuit structure generally applicable to any combination of the multiple MLNs is proposed. The load network has a simple structure including impedance matching circuits and offset lines for the carrier and peaking amplifiers. A design procedure for the proposed load network is presented. A DPA using any optimized combination of the multiple MLNs can be easily designed using the proposed load network. For verification, a GaN-HEMT symmetrical DPA based on a combination of the virtual open-stub (VOS) and out-phased current combining (OCC) methods was designed and implemented for the frequency band of 3.4 - 3.7 GHz. The reversed uneven power splitting method is adopted in the design for higher power gain. Using the 5G New Radio (NR) signal with a peak-to average power ratio (PAPR) of 7.9 dB and a signal bandwidth of 100 MHz, the proposed DPA exhibited DE of 55.3 - 60.9% with a power gain of 11.9 - 12.7 dB at an average output power of 33.7 dBm. An adjacent channel leakage power ratio (ACLR) of −42.6 - −44.8 dBc was achieved at the average power level by using a digital predistortion (DPD) technique across the band.

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