Reduced Size and Tunable Microwave Circuits Using BST Thin-Film Varactors

Conference: GeMIC 2008 - German Microwave Conference
03/10/2008 - 03/12/2008 at Hamburg-Harburg, Germany

Proceedings: GeMIC 2008

Pages: 4Language: englishTyp: PDF

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Lourandakis, Errikos; Weigel, Robert (Institute for Electronics Engineering, University of Erlangen-Nuremberg, Cauerstrasse 9, 91058 Erlangen, Germany)
Schmidt, Matthias; Leidl, Anton; Seitz, Stefan (EPCOS AG, Anzinger Strasse 13, 81671 Munich, Germany)

The potential of using Barium-Strontium-Titanate (BST) varactors in order to design reduced size and frequency agile circuits is presented. Possible candidates for this method are transmission line based microwave circuits such as branch-line hybrid couplers and Wilkinson power dividers. Both topologies are discussed and the suitability of the methodology is verified by a prototype circuit. A Wilkinson power divider was implemented and characterised showing good agreement between simulation results and measurements. The additional insertion loss in both output branches remains below 1.2 dB while maintaining a worst case amplitude- and phase difference of 0.5 dB and 9 degrees respectively. The operating frequency can be tuned continuously from 1.7GHz to 2.1GHz exhibiting an isolation between the two output ports of more than 25 dB over the whole tuning range.