| A brief review of composite right/left handed (CRLH) transmission line (TL) theory and CRLH substrate integrated waveguide (SIW) leaky wave antennas (LWAs) is presented. Further, a work of circularly polarization (CP) low side lobe level (SLL) CRLH SIW LWA is shown. The SLL reduction is achieved by tapering the radiation amount in each radiation unit along the LWA. In the second part, the principle of diffraction gratings are summarized. In addition, a set of novel planar metasurface structures are proposed to behave as a 3D diffraction grating such that the specular reflection is minimized. The feature is obtained by utilizing both periodicity of the super unit structure and phase modulation provided in the unit cells. Two different designs of such structure are given following the same methodology. The metasurface then is applied to a rectangular waveguide to create a stopband structure. |
