Sharif Digital Repository

In the majority of leaky-wave antennas (LWAs), the lack of broadside radiation is due to the existence of an open-stopband (OSB) at broadside. In this letter, we present a study on the OSB suppression in LWAs. In particular, we start from a simple unit cell comprising a planar waveguide having alternating open and short sidewalls. The analytical and simulated band structures testify consistently that OSB suppression can indeed be realized by proper design, analytically studied using mode-matching, and further supported by full-wave simulations. An LWA is then implemented using the substrate integrated waveguide (SIW) technology, which provides interesting features such as a high directive... 

In this work, we present a study on the existence of Dirac type dispersion in the simplest of periodic metallic waveguide structures. It is shown that periodic repetitions of two dissimilar waveguides (WGs) can be properly designed to lead to a Dirac type dispersion. A simple theory using circuit modeling is presented to find the condition for Dirac point operation. In addition, mode-matching followed by full-wave simulations validate that the band structure matches that of the theory and shows that a Dirac dispersion can be realized. A Dirac Leaky-Wave Antenna (DLWA) is then implemented using this simple arrangement in substrate-integrated-waveguide (SIW) technology. This DLWA has the... 

The physics behind the broadband Brewster transmission through square arrays made of rectangular metallic pillars is explored by appealing to the effective medium theory. First, an analytical solution is given for the principal electromagnetic mode propagating between the pillars, and then, the mode matching technique is invoked to extract the parameters of the effective medium model. In this fashion, the pillars are homogenized via a diagonal anisotropic tensor and the effects of higher diffracted orders are included in the effective medium theory by attributing a surface conductivity to the surface boundary of the array. It is shown that the former effectuates the wideband Brewster effect...