Linearity enhancement of GaN HEMTs under complex modulated excitation by optimizing the baseband impedance environment

Akmal, Muhammad, Carrubba, Vincenzo, Lees, Jonathan ORCID: https://orcid.org/0000-0002-6217-7552, Bensmida, S., Benedikt, Johannes ORCID: https://orcid.org/0000-0002-9583-2349, Morris, K., Beach, M., McGeehan, J. and Tasker, Paul J. ORCID: https://orcid.org/0000-0002-6760-7830 2011. Linearity enhancement of GaN HEMTs under complex modulated excitation by optimizing the baseband impedance environment. Presented at: 2011 IEEE/MTT-S International Microwave Symposium, Baltimore, MD, USA, 5-10 June 2011. Published in: Seigel, Peter, Remley, Kate, Tzuang, C. and Ponchak, George eds. 2011 IEEE/MTT-S International Microwave Symposium - MTT 2011. New York: IEEE, pp. 1747-1750. 10.1109/MWSYM.2011.5972833

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Abstract

This paper demonstrates how the linearity performance of a 10 W GaN HEMT can be dramatically improved by actively engineering the baseband impedance environment around the device. An important refinement to existing active load-pull measurement capability is proposed that allows the precise and independent control of all significant baseband and RF components that result from the amplification of a complex 9-carrier multi-sine modulation. The synthesis of constant, modulation frequency independent negative baseband impedances, resulting in specific baseband voltage waveforms has delivered a 24 dB improvement in ACPR compared to the classical baseband short case, even when the device is operating with RF components terminated into a non-optimal 50Ω RF environment. This linearization concept is further investigated through the broadband emulation of a class-J impedance environment around a single device. Using this enhanced system and a two-tone modulated excitation, optimum baseband loads are identified that result in a 18.5 dB and 24 dB improvement in IM3 and IM5 inter-modulation products respectively, again relative to the case of a traditional IF short circuit. The significance of this last observation is that unlike the 50Ω case, the optimum class-J IM3 and IM5 baseband impedances disperse, becoming reactive and moving away from the real axis.

Item Type:	Conference or Workshop Item (Paper)
Status:	Published
Schools:	Engineering
Subjects:	T Technology > TK Electrical engineering. Electronics Nuclear engineering
Uncontrolled Keywords:	Active load-pull; baseband; harmonics; memory effects; power device
Additional Information:	Proceedings of a meeting held 5-10 June 2011, Baltimore, Maryland, USA
Publisher:	IEEE
ISBN:	9781612847542
Last Modified:	18 Oct 2022 13:49
URI:	https://orca.cardiff.ac.uk/id/eprint/15573

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