O. Bengtsson, S.A. Chevtchenko, R. Doerner, P. Kurpas and W. Heinrich

Published in:

Frequenz, vol. 65, no. 7-8, pp. 217-224 (2011).

Abstract:

In this paper the potential and limitations of using a high-voltage GaN-HEMT RF-power technology with supply modulation for increased back-off efficiency is investigated. Based on extensive on-wafer class-AB loadpull characterization at various supply voltages and input power levels followed by advanced post-processing of the measured data, the possible efficiency improvement with supply modulation is explored and the technology and device limitations are discussed. The analysis is conducted for operation at three different maximum modulation voltages 15 V, 28 V, and 48 V. Post-processing of the measurement data shows a voltage dependent possible static efficiency enhancement of 25 to 40 percentage points in the 10 dB back-off region for a WCDMA signal. For the high voltages it is shown that the efficiency increase using supply modulation for high PAPR signals is greatly reduced. This is mainly a function of the narrower load-impedance matching range at higher supply voltages.

Keywords:

Power amplifiers, GaN-HEMT, supply modulation.

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