TUNABLE FILTER

摘要

PROBLEM TO BE SOLVED: To provide a tunable filter that inexpensively and compactly reduces the number of variable elements for changing characteristics.SOLUTION: A tunable filter 1 has a resonator section 4 and a series variable reactance element 5 connected in series on a signal path connecting an input terminal 2 and an output terminal 3 to constitute a first circuit element, and has a parallel variable reactance element 6 connected to the first circuit element. The resonator section 4 comprises either an n-tuple mode resonator (n is an integer of two or greater) or a plurality of resonators.