A multi-mode transmission line includes a first and second conductive layers, first and second waveguide walls, a strip line, and a blind conductor. The second conductive layer that is formed over the first conductive layer. The first waveguide wall is elongated in a first direction and is in contact with the first conductive layer and the second conductive layer in a vertical direction. The second waveguide wall is elongated in the first direction parallel to the first waveguide wall and is in contact with the first conductive layer and the second conductive layer in the vertical direction. The strip line is formed between the first and second conductive layers and between the first and second waveguide walls. The blind conductor is connected to one of the first conductive layer, the second conductive layer, the first waveguide wall, or the second waveguide wall.