Higher-Order Cylindrical Leaky Waves-Part I: Canonical Sources and Radiation Formulas

Radiation from cylindrical leaky waves (CLWs) supported by layered dielectric media is of interest in a variety of current applications. A comprehensive two-part study has been undertaken to investigate the generation and the radiation properties of CLWs with an arbitrary integer azimuthal order $n$ . The first of this two-part sequence deals with the identification of continuous rings of canonical sources of electric and magnetic types, capable of exciting higher-order CLWs (HOCLWs) in planar open radial waveguides. The relevant far-field radiation formulas are then derived, generalizing those already available in the literature for cylindrical waves with azimuthal orders $n=0$ and $n=1$ , i.e., those excited by elementary vertical or horizontal dipoles. Design guidelines for the practical excitation of HOCLWs through discrete sources, namely, circular phased arrays, are provided in the companion paper along with numerical validations and illustrative results in both the near-field and the far-field regions.