Electromagnetic Radiation Field from a Flanged Rectangular Waveguide

In this paper, the radiation of an electromagnetic wave from a canged rectangular waveguide is exactly formulated by using the KP method when the waveguide is excited by TE- and TM-mode waves. The process of analysis is similar to [4]. The aelds in the waveguide and half-space are expanded in terms of the normal modes of the waveguide and the Weber-Schafheitlin (WS) discontinuous integrals, respectively. Imposing the continuity of the tangential components of the aelds on the aperture, we obtain a matrix equation to determine the expansion coeecients of the diaracted wave. The matrix elements are given by double inanite integrals and double inanite series which contain Bessel functions, and an eaective method for computing the double inanite series is proposed. Using the derived formula for the far diaracted aeld, the radiation patterns are computed for various kinds of parameters. 2. Statement of the problem Fig. 1 shows an open-ended canged rectangular waveguide and the related coordinate systems. We study the aeld E d radiated from the aperture to the half-space z> 0, when an electromagnetic wave E i in the waveguide are propagating in the positive z direction. The cange and waveguide are assumed to be perfectly conducting and the permittivity and permeability of the half-space（region I）are e1 and n1, respectively. The inside of the waveguide（region II） is alled with a homogeneous isotropic medium with parameters e2, n2, and the dimension of the guide is 2aC2b. The aperture and cange are located in the z = 0 plane. Because of the discontinuity of the geometry at z = 0, the recected wave of the incident wave and the higher-order mode waves are excited at the open end. In this analysis, the harmonic time dependence exp(j!t) is assumed and omitted throughout.