An Electronically Tunable Band Pass Microwave Filter

A new type of tunable band pass microwave filter using the dipole resonance of a plasma column has been investigated. The center frequency of the pass band can be electronically tuned over a large portion of the S band. Over this range the insertion loss at the center frequency is less than 2 db and the isolation for frequencies outside the pass band is at least 12 db. The typical 3 db bandwidth of the filter is 150 Mc/s at S band.