Broadband Switch-Mode Radio Frequency Power Amplifiers using Tunable Ferroelectric Thick-Film Components
Final Report Abstract
Barium-strontium-titante (BST) varactors for high power amplifiers at radio frequencies were developed and evaluated for wideband telecommunication signals. The project was focused on the improvement of the high-power performance, verification of the performance in a test-setup and evaluation of the technology in dynamic operation of a power amplifier targeting a typical telecom application. The project included four main parts: 1. BST material improvement for high power operation and the optimization of thermal properties for low thermal drift and operation under high dissipated power. The approach to use alternative doping for the BST material as well as the MIM capacitor implementation was shown to drastically reduce the thermal drift. 2. Package optimization showing that the complete tunable pre-matching (TpM) PA modules, including a GaN-HEMT device and BST varactors, can be properly modelled by the use of 3D simulations. Inductive bias isolation enables fast dynamic operation that is superior in bandwidth compared to the commercial stacked thin-film BST alternative. 3. Development of a high-power measurement system for the characterization. It enables the testing of TpM-modules as well as high power discrete varactors. Pulsed operation and investigations at alternative base-plate temperatures made it possible to separate voltage induced self-tuning from self-tuning caused by temperature increase from dissipated power. The results show that the developed power varactors have less than 0.5 dB loss and they can handle more than 50 W/mm2 without any thermal self-tuning. 4. Dynamic operation of a tunable power amplifier based on the thick-film BST components. A PA at 1.85 GHz was designed around a 10 mm gate width GaN-HEMT from FBH. The tunable PAs shows a maximum 58% PAE at 45 dBm (31.6 W) output power at 28 V supply voltage biased in low class-AB. By tuning the varactors in 10 V steps from 0 to 100 V, a 3%-points shift in PAE could be accomplished. The project results show that thick film BST varactors can be a competitive solution for the future high-efficiency broadband transmitters. They can handle large power and are very linear. However, the project also shows the need for more research to further improve the varactor technology.
Publications
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Discrete RF-power MIM BST thick-film varactors. In: European Microwave Conference, 2015, pp. 941-944.
S. Preis, A. Wiens, D. Kienemund, D. Kendig, H. Maune, R. Jakoby, W. Heinrich, O. Bengtsson
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Response time of VSWR protection for GaN HEMT based power amplifiers. In: European Microwave Conference, 2016, pp. 401-404.
S. Preis, J. Ferretti, N. Wolff, A. Wiens, R. Jakoby, W. Heinrich and O. Bengtsson
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Wideband tunable GaN HEMT module utilizing thin-film BST varactors for efficiency Optimization. In: IEEE MTT-S International Microwave Symposium, San Francisco, USA, 2016
A. Wiens, S. Preis, C. Schuster, M. Nikfalazar, C. Damm, M. Schuessler, W. Heinrich, O. Bengtsson, R. Jakoby
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Reconfigurable Packaged GaN Power Amplifier Using Thin-Film BST Varactors. In: European Microwave Conference, Nuremberg, 2017, pp. 140-143.
S. Preis, F. Lenze, A. Wiens, R. Jakoby, W. Heinrich, O. Bengtsson
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Thick-Film MIM BST Varactors for GaN Power Amplifiers with Discrete Dynamic Load Modulation. In: IEEE MTT-S International Microwave Symposium, Honolulu, USA, 2017, pp. 281-284.
S. Preis, D. Kienemund, N. Wolff, H. Maune, R. Jakoby, W. Heinrich and O. Bengtsson
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Tunable Ferroelectric Matching Networks implemented into High Power RF Amplifiers for High Dynamic and Wideband Efficiency. Dissertation Technische Universität Darmstadt, 2017, 188 S., ISBN-13 (E-Book) 9783736985117.
A. Wiens
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Load Tuning Assisted Discrete-Level Supply Modulation Using BST and GaN Devices for Highly Efficient Power Amplifiers. In: IEEE MTT-S International Microwave Symposium, Honolulu, USA, 2018, pp. 1230- 1233.
S. Preis, N. Wolff, F. Lenze, A. Wiens, R. Jakoby, W. Heinrich, O. Bengtsson
