Investigation of surface wave modes on ungrounded electrically thick ceramic alumina substrate at 60 GHz

Propagation of surface waves modes on ungrounded dielectric slab of ceramic alumina with εr= 9.8 and 635 μm of electrically thick height at 60 GHz is explored. An approximate graphical technique is implemented to determine the unknown propagation constants kx and α, to achieve a solution for Helmholtz wave equations, for each TE and TM modes. It also indeed provides a physical insight of existing no. of modes and their dependence on permittivity and height of substrate. Cut-off frequency for all propagating modes is calculated and dispersion graph with propagation constant is plotted. A CPW fed monopole antenna, designed and fabricated at 60 GHz, is found to be affected by the presence of surface wave modes on its radiation characteristics. A tilt of 40° is found in E-plane radiation pattern which certainly evidence the presence of surface wave modes at 60 GHz.