Patent ID: 8836450
Filing Date: 2014-09-16
Classification: H01P

Abstract:
1. An adjustable resonator filter which comprises a filter housing comprising: a bottom, a plurality of walls and a lid and functioning as a ground of a transmission path, the space of which housing is divided into resonator cavities by conductive partition walls to form a plurality of resonators, and in each partition wall separating two successive cavities on the transmission path there is a coupling opening to excite an oscillation in a latter successive cavity, and the filter comprises a first movable and conductive tuning element for at least two successive resonators to adjust the coupling between these resonators and, thus, a bandwidth of the filter, wherein; a conductive fixed coupling element extends from at least one resonator cavity of the resonator cavities to a next successive resonator cavity of the resonator cavities through a canal in an upper part of a wall of the plurality of walls of the filter housing; said first movable and conductive tuning element is located outside the resonator cavities in the wall of the plurality of walls of the filter housing, and an adjustable capacitive coupling exists through the first movable and conductive tuning element from said fixed coupling element to the ground for changing the coupling, implemented by the coupling element, between successive resonators of the plurality of resonators; said coupling opening between two successive resonators of the plurality of resonators is dimensioned and the corresponding fixed coupling element is positioned so that the coupling between the resonators implemented by this coupling element is arranged to partly compensate the coupling which takes place through the coupling opening; the filter further comprises a cylindrical second movable and conductive tuning element for adjusting a coupling between an input resonator of the plurality of resonators and an input line of the filter or for adjusting a coupling between an output resonator of the plurality of resonators and an output line of the filter; wherein the second movable and conductive tuning element is supported to a conductor rod so that it can be slid along the conductor rod, which conductor rod, or middle rod, extends from a middle conductor of a coaxial connector of the filter through an opening in a wall of the plurality of walls of the filter housing to a cavity of the input or output resonator and is connected there to an inner coupling element of the respective input or output resonator; an outer conductor which connects galvanically to said wall at its one end and to an outer conductor of said connector at its other end, surrounds the middle rod so that the middle rod with the second movable and conductive tuning element and the outer conductor constitute a transmission line belonging to the transmission path of the filter, and a diameter of the middle rod is sufficiently short and a diameter of the cylindrical second movable and conductive tuning element supported to it is sufficiently long that an impedance of said transmission line is at the second movable and conductive tuning element substantially lower and on both sides of the second movable and conductive tuning element substantially higher than the nominal impedance of the transmission path of the filter.