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. © 2008 IEEE.
- Barium-strontium-titanate (BST)
- Dual mode filter
- Ferroelectric material
- Tunable circuit
- Tunable filter