Patent ID: 7113059

Claim:
A high frequency filter comprising: a substrate, a ground conductor having an opening provided on one principal surface of said substrate, a center conductor provided on said one principal surface of said substrate in said opening and making up a coplanar line resonator of a coplanar structure together with said substrate and said ground conductor, an input line and an output line provided on the other principal surface of said substrate and adapted to electromagnetically couple with said center conductor, and a variable reactance element inserted in said center conductor at the position of a null point in voltage displacement of a standing wave created in the center conductor operating as a resonator, wherein said center conductor is divided into a first conductor section and a second conductor section at the inserted position of said variable reactance element so as to separate the first and second conductor sections in a longitudinal direction of said center conductor, said variable reactance element being connected at one end to said first conductor section and at the other end to said second conductor section.