Open AccessModulated rapid load pull system for the emulation of envelope tracking power amplifiers
Author(s) -
Alsahali S.,
Gecan D.,
Alt A.,
Chen P.,
Woodington S.,
Sheikh A.,
Tasker P.,
Lees J.
Publication year - 2020
Publication title -
electronics letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.375
H-Index - 146
ISSN - 1350-911X
DOI - 10.1049/el.2019.3896
Subject(s) - linearity , amplifier , distortion (music) , electronic engineering , emulation , power (physics) , electrical efficiency , electrical impedance , engineering , computer science , electrical engineering , cmos , physics , quantum mechanics , economics , economic growth
This Letter presents a novel characterisation system that is able to fully emulate a complete envelope tracking power amplifier (ET‐PA) environment, with modulated impedance synthesis and dynamic supply voltage generation while using industry‐standard modulated signals and digital pre‐distortion. The system is used to characterise a 10 W GaN device and provide impedance control over the signal and distortion bandwidths, in response to a 10 MHz long‐term evolution signal. A National Instruments PXI‐based measurement system is utilised to apply tracking signals to a bespoke supply modulator and successfully improve the average power added efficiency by ∼18 percentage points. Three different shaping functions are implemented, and their efficiency and linearity performance evaluated. In addition, digital pre‐distortion (DPD) is used to linearise the PA while operating with the three different tracking trajectories. Experimental results demonstrate that when applying shaping functions, a trade‐off needs to be made between efficiency and linearity. Even though a constant gain shaping function provides lower efficiency, it achieves good raw linearity performance without DPD, which is a good option if local linearisation is not available. This novel system is a useful tool in the design of ET‐PAs, to more completely investigate the performance of the device.