Tunable RF-Filter Using Mn-Doped BST Ceramic Varactors

Abstract

A two-pole combline band-pass filter loaded by ferroelectric MIM (Metal-InsulatorMetal) varactors is designed, fabricated and tested. The varactors use new Mn-doped Barium Strontium Titanate (BST) ferroelectric ceramics developed to improve the performances at microwave frequencies (i.e. compromise between tuning capabilities and losses). The filter measurements demonstrate a frequency tuning of more than 16% in the 370-430-MHz frequency range under an applied field of 2 kV/mm.