Thick-Film Barium-Strontium-Titantate Varactors for RF Power Transistors

A. Wiens1, O. Bengtsson2, H. Maune1, M. Sazegar1, W. Heinrich2, and R. Jakoby1

Published in:

Proc. 43th European Microwave Conf. (EuMC 2013), Nuremberg, Germany, Oct. 7-10, pp. 1351-1354 (2013).

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This work addresses the properties of Barium- Strontium-Titanate based thick-film varactors at conditions that are expected to arise when the varactors are integrated in a packaged RF power transistor i.e. varying thermal conditions in combination with large fields and high power larger than 30dBm. The varactors are characterized in a small- and largesignal environment in a wide temperature range. A considerable thermal dependency is found and its effect on a tunable prematching transistor assembly is investigated. At a 40 degree Celsius temperature increase, the pre-matching shunt varactor increases the gain shift from 1.0dB up to 1.3dB compared to a non pre-matched GaN. Considering these effects in the design, the additional shift can be fully re-tuned with the varactor bias voltage to re-establish the gain of the GaN-HEMT.

1 Institut für Mikrowellentechnik und Photonik, Technische Universität Darmstadt, Darmstadt, Germany
2 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany


ferroelectrics, BST, nonlinear devices, power amplifier.