PROPAGATION AND EXCITATION OF THE HIGHER-ORDER Ex11 MODE IN AN INSULATED IMAGE GUIDE

The use of E-x(11) mode in an insulated image guide is proposed. This mode has much lower conductor loss than the fundamental, E-y(11) mode. 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(11) mode 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. (C) 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:179-181, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26450