Electrically tunable split-ring resonators at microwave frequencies based on barium-strontium-titanate thick films

Split-ring resonators (SRRs) implemented using ferroelectric materials to modify their resonance frequency by means of a tuning voltage are presented for the first time. SRRs have been used to load a microstrip transmission line on a multilayered substrate including a thick film of barium-strontium-titanate (BST) to obtain a tunable stopband response. The characteristics of the BST layer allow the application of 140 V as tuning voltage to obtain frequency tunability values of around 12.5 . The applied technology is suitable for the fabrication of cost-effective and reliable planar microwave devices.