The electromagnetic characteristics associated with the creeping waves supported by a dielectric coated cylinder ate investigated. The propagation constants and wave impedances of the creeping waves are obtained nnmerically. Higher order modes which are significant for a thick coating are also investigated. The propagation constants and creeping wave modal impedance are compared with those obtained for a planar dielectric slab backed by a ground plane. It is found that, contrary to the planar configuration, no cutoff frequencies exist for the creeping waves associated with the coated cylinder. In fact, the coated cylinder supports an infinite number of modes. However, depending upon the thickness of the coating, only a few Elliott type creeping wave modes with low attenuation can exist. Furthermore, for each of the Elliott type creeping waves, there is a critical radius for the cylinder below which the EUiott type creeping wave cannot exist. The results are also compared with an impedance boundary cylinder, where the impedance is chosen to be purely imaginary.C

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An H-polarized leaky wave antenna (LWA) employing metal strip grating (MSG) is presented. A novel feeding system based on the ridge gap waveguide (RGW) technology feeds the proposed antenna. The proposed feeding mechanism is made up of a profiled Quasi-TEM horn ridge gap waveguide, which is designed to have the same aperture width and provide uniform field excitation to the leaky wave antenna. The design is performed to provide proper matching between the launcher and the MSG to improve the antenna radiation efficiency. The proposed antenna is operating at 28.5 GHz with a scanning angle capability of -20 o achieving a realized gain of 24 dBi. Several numerical results using point-matching and aperture distribution method are used to analyze the proposed LWA. Moreover, measurement results are presented to illustrate the effectiveness of the novel feeding system functioning as the LWA launcher.Index Terms-Leaky wave antenna (LWA), metal strip grating (MSG), ridge gap waveguide (RGW), and horn ridge.

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