Look‐up table method for optimising coupling ratio in broadband sequential power amplifiers. Issue 13 (22nd September 2020)

• Record Type: Journal Article
• Authors: Chen, Peng; Quaglia, Roberto; Lees, Jonathan; Merrick, Brian M.; Alt, Alexander; Tasker, Paul J.
• Is Part Of: IET microwaves, antennas & propagation. Volume 14:Issue 13(2020)
• Page Start: 1626
• Page End: 1634
• Publication Date: 2020-09-22
• Subjects: UHF power amplifiers -- wideband amplifiers -- directional couplers -- table lookup; required coupling ratio -- wideband directional coupler -- drain efficiency -- digital predistortion -- adjacent channel leakage ratio levels -- look‐up table method -- broadband sequential power amplifiers -- optimum design parameters -- sequential power amplifier -- relative phase difference -- phase relationship -- main peaking amplifiers -- modified efficiency formulation -- key design parameters -- SPA efficiency -- high‐efficiency SPA design -- optimising coupling ratio -- LTE signal -- error vector magnitude -- frequency 20.0 MHz -- frequency 1.5 GHz to 2.4 GHz; Microwaves -- Periodicals; Microwave antennas -- Periodicals; Antennas (Electronics) -- Periodicals; Radio wave propagation -- Periodicals; Microwave communication systems -- Periodicals; 621.381305
• DOI: 10.1049/iet-map.2019.1102
• Languages: English
• ISSNs: 1751-8725

Abstract

Abstract : This study reappraises the optimum design parameters for the sequential power amplifier (SPA) when taking relative phase difference into account. By including the phase relationship between the main and peaking amplifiers, a modified efficiency formulation is derived that reveals the impacts of the key design parameters on the SPA efficiency at output power back‐off. To optimise a wideband high‐efficiency SPA design, a look‐up table method is used to predict the required coupling ratio for a wideband directional coupler. To validate the design approach, a 1.5–2.4GHz SPA is designed and measured, showing drain efficiency higher than 40% at 6dB back‐off across the band. When characterised using a 20MHz long term evolution (LTE) signal and digital predistortion, the SPA shows good linearity with error vector magnitude <1.3%, and adjacent channel leakage ratio levels better than −45 dBc across the band.