Comment: Leaky waves on a dielectric rod

An approximate analysis by Arnbak has shown that solutions (near cutoff) to the cylindrical dielectric-rod transcendental equation (for n=0) possess the same symmetry in their complex top-sheet domain as that commonly found in planar interface structures. The letter shows that, for all solutions (n=0, 1, 2, ¿) on a lossless cylindrical dielectric rod, symmetry can only hold in the upper (proper) half plane of the top sheet. Symmetry in the lower (improper) half plane involves two sheets. An illustrative example is given and a useful computing technique is mentioned.