A 380 – 420 MHz two-pole tunable filter using new ferroelectric composite capacitors

This paper presents the design, the fabrication and the measures of a two-pole tunable band-pass filter. The design filter consists of two microstrip resonators loaded by ferroelectric MIM (Metal-Insulator-Metal) capacitors. The capacitors use the Barium Strontium Titanate (BST) ceramics doped by 1% Manganese. The filter tunes from 385 MHz to 420 MHz under 0-380 V of bias. The insertion loss is -2.9 dB at zero bias (385 MHz) and the return loss is - 11 dB at 420 MHz.