Propagation and excitation of the higher‐order E x 11 mode in an insulated image guide

The use of E   x 11mode in an insulated image guide is proposed. This mode has much lower conductor loss than the fundamental, E   y 11mode. The electric field of the mode is primarily parallel to the metal ground‐plane; therefore, the mode can be efficiently excited with a compact dipole structure oriented parallel to the ground‐plane. When the insulating layer is of low permittivity and relatively thick, the E   x 11mode exhibits the highest effective permittivity (largest propagation constant) of all modes. This reduces unwanted mode coupling at discontinuities. Two example structures, a straight line and a double‐bended line are measured at frequencies around 8 GHz. The excitation of the waveguide causes insertion loss of less than 0.4 dB, and the radiation loss of the bends and the waveguide itself appears to be negligible. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:179–181, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26450