Bandwidth and Central Frequency Tunable Bandpass Filter

This paper presents an original tunable filter topology, which allows to control both the central frequency and the bandwidth. This structure is based on the association of a particular passive stubs filter with capacitors. The capacitors, placed at the end of the stubs, act as agility elements. The elementary resonators of the passive filter are based on the parallel association of open-ended stubs which create transmission zeros on each side of a pass-band. In the last part, we describe a central frequency tunable filter implemented in coplanar technology using MEMS as variable capacitors.