Design of tunable band pass filter using barium strontium titanate (BST) thin films

Date of Award


Degree Name

M.S. in Electrical Engineering


Department of Electrical and Computer Engineering


Advisor: Guru Subramanya


Barium strontium titanate (Ba1-xSrxTiO3) thin films exhibit unique properties like high dielectric constant, voltage tunable permittivity and small loss tangent which make it attractive in applications of tunable microwave devices. Following are some of the areas where ferroelectrics are applied (1) Random Access Memories (FERAM's) (2) Integrated optics switches, couplers and modulators (3) piezoelectric resonators (4) Capacitors (5) Oscillators and (6) tunable filter. An effort is made to study and characterize the properties of BST thin films and to design a tunable band pass filter using their unique properties like tunable permittivity and low loss tangent. Different EM structures of IDC's (Inter Digital Capacitors) are designed, tested, characterized and an effort is made to optimize the design for high Quality Factor (Q). A tunable band pass filter is designed, fabricated and tested for 1.72GHz center frequency. This is one of the foremost efforts made to design a band pass filter with Coplanar Wave Guide (CPW) transmission line components and BST varactor devices. The total length of the filter is 2.3mm.


Electric filters, Bandpass Design and construction, Barium compounds, Ferroelectric thin films Research, Microwave devices

Rights Statement

Copyright 2011, author