Frequency analysis of load modulation networks for asymmetric Doherty power amplifiers in GaN

Research output: Contribution to journalResearch articleContributedpeer-review


This paper investigates the frequency response of load modulation networks for asymmetric Doherty power amplifiers (ADPA) with an output back-off power level larger than 6 dB and a power ratio of peak to main amplifier (N - 1) larger than 1. The influence of the main path impedance transformer (IT) on the Doherty impedances at main and peak path as well as on the ADPA's efficiency is analyzed. Scaling of the main IT's characteristic impedance via ξ indicates a maximum broadband matching for an input voltage Vin of ξ · Vin,max. By weighting the frequency- and ξ-dependent efficiency curves using a probability density function (PDF), an optimum is obtained for ξ = 1/N. To verify the theory, three ADPAs with different ξ-scaled ITs are designed, measured, and compared. For the design at 3.6 GHz, a gallium nitride (GaN) transistor is used. By means of the intrinsic node matching technique, matching at the current source plane is obtained. In laboratory measurements, the ADPA with ξ = 1/N achieves a power-added efficiency (PAE) of 63% at 42 dBm output power and a PDF-weighted average PAE of 38.8% within 400 MHz bandwidth for 8 dB peak-to-average power ratio. Comparison with similar state-of-the-art ADPAs in GaN technology shows highest PAE and operation power gain GP for center frequencies larger than 3.0 GHz.


Original languageEnglish
Pages (from-to)123-133
Number of pages11
JournalInternational Journal of Microwave and Wireless Technologies
Issue number2
Publication statusPublished - 22 Mar 2022

External IDs

Scopus 85120305348
Mendeley 4dce1f82-ed8a-31d1-8330-3be1c3e65b39
WOS 000734783400001
unpaywall 10.1017/s1759078721001550
ORCID /0000-0001-6778-7846/work/142240152


Research priority areas of TU Dresden

ASJC Scopus subject areas


  • Active circuits, Asymmetric Doherty, Power amplifiers