Romain Costes

Microwave study of tunable planar capacitors using mn-doped ba 0.6 sr 0.4 tio 3 ceramics

This paper deals with the microwave study of coplanar tunable capacitors using Mn-doped Ba0.6Sr0.4TiO3 ceramics. These ceramics are developed to improve performance at microwave frequencies (i.e., compromise between tuning capabilities and insertion losses). Interdigitated capacitors were first fabricated on thick Mn-doped BST ceramics. The capacitors showed reduced tuning factor because of a parasitic capacitance between the contact pads. The use of Mn-doped BST/ SiO2 bilayers led to a significant enhancement of the capacitor performance (57% of agility under 200 V at 1 GHz).

Tunable RF-Filter Using Mn-Doped BST Ceramic Varactors

A two-pole combline band-pass filter loaded by ferroelectric MIM (Metal-Insulator-Metal) 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.