A novel tunable filter enabling both center frequency and bandwidth tunability

This paper presents a novel filter circuit configuration that enables both the center frequency and the bandwidth to be tuned with a steep frequency response. Digital-type and microelectromechanical system (MEMS) analog-type tunable filters with a small size of 3.3 mm × 3.8 mm on a high-k low-temperature-co-fired-ceramics (LTCC) wiring wafer have been developed to verify the proposed filter configuration. The digital type achieved a wide tuning range of 62.7% from 1.4GHz to 2.7 GHz with an insertion loss of 2.21 - 2.48 dB. And a 119% bandwidth tuning from 300 MHz to 650 MHz was also verified with an insertion loss under -3dB. Moreover, the analog type achieved a center frequency tuning about 600 MHz from 2.8 GHz to 3.4 GHz using integrated MEMS varactors. The new filter configuration was verified to enable a steep frequency response with a shape factor less than 2.