Waveguide impedance matching transitions while maintaining effective cross-section unchanged

Claim 1

A WAGEGUIDE COUPLING ARRANGEMENT COMPRISING, IN COMBINATION: A FIRST WAVEGUIDE OF CIRCULAR CROSS-SECTION HAVING A PREDETERMINED VALUE OF SURFACE IMPEDANCE OVER THE MAJOR PORTION OF ITS LENGTH, THE INNER SURFACE OF SAID FIRST WAVEGUIDE HAVING PLURAL CIRCUMFERENTIAL GROOVES THEREIN OVER THE REMAINING PORTION OF ITS LENGTH TERMINATING IN ONE END TO PROVIDE A GRADUAL TRANSITION OF SURFACE IMPEDANCE FOR MATCHING SAID PREDETERMINED VALUE TO ANOTHER, DIFFERENT VALUE OF SURFACE IMPEDANCE AT SAID END, SAID GROOVE HAVING DIMENSIONS WHICH VARY PROGRESSIVELY TOWARD SAID END, AND BOTH SAID MAJOR PORTION AND THE REMAINING PORTION HAVING A THE SAME CONSTANT MINIMUM INTERNAL DIAMETER; A SEOND WAVEGUIDE OF CIRCULAR CROSSSECTION HAVING A SURFACE IMPEDANCE SUBSTANTIALLY EQUAL TO SAID DIFFERENT VALUE; AND COUPLING MEANS FOR JOINING SAID FIRST WAVEGUIDE AND SAID SECOND WAVEGUIDE END TO END FOR PROPAGATION OF ENERGY IN THE TE01 MODE BETWEEN THE TWO WAVEGUIDES WITHOUT ANY REFLECTION OR MODE CONVERSION.