Design of Microstrip Tunable Bandpass Filter using Ferroelectric Thin Film Varactor

This paper describes the design and fabrication of a voltage tunable Microstrip line hairpin structured band-pass filter at 27.6 GHz centre frequency. To get frequency tunability, Barium Strontium Titanate (BST) based parallel plate varactor is used. Parallel plate varactor is designed in which BST is used as dielectric and the designed varactor is integrated in the microstrip line band pass filter. The schematic and layout design of the filter is designed and simulated in Advanced Design System (ADS) simulation software. For filter layout design sapphire (Ɛ
r
=11.58) is considered as substrate and the metal electrodes used are platinum and gold. The S parameters observed are insertion loss (S
21
) of around -1dB and Return loss (S
11
) of less than −20dB. All the simulations are done in Advanced Design System (ADS).