Miniaturized coaxial cavity tunable filter with balanced bandwidths at high end and low end

The invention relates to a miniaturized coaxial cavity tunable filter with balanced bandwidths at a high end and a low end. The prior coaxial cavity tunable filter can not maintain a constant bandwidth at different frequency bands. The miniaturized coaxial cavity tunable filter comprises a filter shell and a baffle plate, wherein a front end cover and a back end cover of the filter shell are provided with coaxial joints; the baffle plate is arranged in the middle of the filter shell; a rectangular coupling window is arranged on the baffle plate; the bottom edge of an inter-cavity coupling looppasses through the coupling window to be arranged; the plane where the inter-cavity coupling loop is arranged is perpendicular to the plane where the rectangular coupling window is arranged; two waists of the inter-cavity coupling loop are respectively positioned in a front coaxial cavity and a back coaxial cavity; and the top point of the inter-cavity coupling loop is positioned in the middle point of a line section where the jointing part of the baffle plate and the bottom of the filter shell is positioned. In the invention, the coupling window of the filter is combined with the inter-cavity triangular coupling loop, and the structure can be used for enabling the bandwidth of the coaxial cavity tunable filter to be constant in the whole frequency tuning range.