Abstract: A connecting piece for connecting a rectangular waveguide with an elliptical waveguide is composed of a waveguide section having a rectangular cross section identical to that of the rectangular waveguide to be connected, the waveguide section being provided, in the center of at least one of its wide sides, with a cylindrical recess at a distance of 1/8 of the waveguide wavelength with respect to the center of its longitudinal dimension from the plane of connection with the elliptical waveguide, the length of the recess in the longitudinal direction of the waveguide section being less than 1/4 such wavelength and the depth of the recess being selected in dependence on its length to match the two connected waveguides over a broad frequency band.

Abstract: A flange adapted to be arranged on a tube. A plurality of flange parts fit together to define a flange having a central opening for surrounding the outer perimeter of a tube. Each of the flange parts defines at least a portion of the central opening. Each flange part is provided on its surface portion which defines at least a portion of the central opening with at least one protrusion for engaging a corresponding groove in an associated tube in a form-fitting relationship.