An impedance converter device comprises an electrically conductive external conductor with one or more connection locations for electrical lines, an electrically conductive internal conductor with one or more connection locations for electrical lines, and also a dielectric arranged between external conductor and internal conductor. The external conductor comprises a base area bounded by one or more side walls thereby forming an external conductor housing with an internal space and an opening opposite the base area. The internal conductor is arranged in the internal space. The internal conductor and the external conductor are insulated from one another by the dielectric. The internal conductor comprises at least one cutoff bar-type section with a cutoff bar bottom and at least one wall which extends from the bottom in the direction of the opening of the external conductor housing.