Patent ID: 7236069

Claim:
An adjustable resonator filter, which comprises a plurality of resonators housed in a single conductive housing and an arrangement to shift an operating band of the filter by a one-time adjustment, each resonator including an inner conductor, a bottom and a wall belonging to said housing and a cavity formed in said housing, wherein said arrangement comprises for each resonator an adjustment circuit with a fixed tuning element that is located in the resonator cavity and has an electromagnetic coupling to the inner conductor of the resonator, and an adjusting part located outside said housing, the fixed tuning element and the adjusting part forming a transmission line together with an outer surface of the resonator wall, the electric length of the transmission line being adjusted by a control of the adjustment circuit to change the reactance of the transmission line and thereby the natural frequency of the resonator, and wherein said control is applied in common for all of the resonators of the filter in order to implement said one-time adjustment in shifting the operating band of the filter.