Waveguide transition piece with low reflection

Claim 1

In a waveguide transition piece for the broad-banded, low reflection connection of a standard waveguide having a rectangular inner cross section with a smooth or corrugated waveguide having an oval inner cross section, said transition piece being a waveguide with a substantially rectangular inner cross section with the central portion of the longer sides of said inner cross section of a section of said transition piece having a widened portion which extends, in the form of linearly widened conical sections over a length of no more than 0.85 waveguide wavelengths ( lambda H), in the direction toward the end of the transition piece to which the oval waveguide is to be connected, said widened portion serving substantially to effect a broadbanded matching of the characteristic impedance of the two waveguides having different inner cross sections which are to be connected by means of concentrated adapter elements which act, at the point where they are disposed, predominantly as parallel capacitances or parallel inductances; the improvement wherein said transition piece includes a further waveguide section disposed between the connecting plane with the oval waveguide and the end of the waveguide section having the conically widened portion, said further waveguide section being no longer than lambda H/8 and having a rectangular inner cross section whose longer sides are uniformly circularly widened in the central portion thereof with the diameter of these widened portions being less than the greatest diameter of said conically widened portion.