BST-Varactor Tunable Dual-Mode Filter Using Variable ${Z}_{C}$ Transmission Line

Ferroelectric materials like barium-strontium-titanate (BST) have become attractive for microwave tunable circuit applications. This letter presents an investigation of BST-varactor tunable dual-mode filter using variable characteristic impedance or ZC transmission line. The interdigital BST varactors are fabricated and modeled, which are then deployed to realize a bandpass filter with tunable bandwidth capability. The use of tunable impedance line provides additional flexibilities in the design of microwave tunable circuits. A tunable bandpass filter of this type with a center frequency of 1.8 GHz and a bandwidth tuning ratio of 1.15:1 is demonstrated experimentally.

[1]  Kwok-Keung M. Cheng.  Design of dual-mode ring resonators with transmission zeros , 1997 .

[2]  H. Yabuki,et al.  Dual-mode stepped-impedance ring resonator for bandpass filter applications , 2001 .

[3]  A. Tombak,et al.  Tunable barium strontium titanate thin film capacitors for RF and microwave applications , 2002, IEEE Microwave and Wireless Components Letters.

[4]  Ming-Fong Lei,et al.  An analysis of miniaturized dual-mode bandpass filter structure using shunt-capacitance perturbation , 2005 .

[5]  Jia-Sheng Hong,et al.  A novel tunable transmission line and its application to a phase shifter , 2005 .

[6]  M.B. Steer,et al.  An electronically tunable microstrip bandpass filter using thin-film Barium-Strontium-Titanate (BST) varactors , 2005, IEEE Transactions on Microwave Theory and Techniques.

[7]  Ke Wu,et al.  Microwave characterization of ferroelectric thin-film materials , 2005, IEEE Transactions on Microwave Theory and Techniques.

[8]  J. Papapolymerou,et al.  Frequency and Bandwidth Agile Millimeter-Wave Filter Using Ferroelectric Capacitors and MEMS Cantilevers , 2007, IEEE Transactions on Microwave Theory and Techniques.

[9]  Michael J. Lancaster,et al.  Microwave properties of Ba0.5Sr0.5TiO3 thin film coplanar phase shifters , 2006 .

[10]  Felix A. Miranda,et al.  Design and development of ferroelectric tunable microwave components for Kuand K-band satellite communication systems , 2000 .

[11]  A. Mortazawi,et al.  Improving Linearity of Ferroelectric-Based Microwave Tunable Circuits , 2007, IEEE Transactions on Microwave Theory and Techniques.