Planar antenna utilizing cascaded right-handed and left-handed transmission lines

A planar antenna apparatus comprising:

• a dielectric substrate having a first surface and a second surface opposite to the first surface;
• a ground plane on the second surface of the dielectric substrate;
• a feeding line disposed on the first surface of the dielectric substrate;
• an antenna section based on a portion of the dielectric substrate, comprising:
• a first conductive pattern disposed on the first surface of the portion of the dielectric substrate, the feeding line being coupled to the first conductive pattern, wherein the first conductive pattern comprises:
• a first patch coupled to the feeding line;
• a first trace coupled to the first patch;
• and a second patch, coupled to the first trace, comprising a first sub-patch and a second sub-patch;
• a second conductive pattern disposed on the second surface of the portion of the dielectric substrate and connected to the ground plane, wherein first conductive pattern is coupled to the second conductive pattern so as to serve as a cascade of a right-handed transmission line and a left-handed transmission line;
• wherein the first and second conductive patterns comprise:
• a first lumped equivalent circuit of the right-handed transmission line;
• and
• a second lumped equivalent circuit of the left-handed transmission line, cascaded with the first lumped equivalent circuit, wherein the right-handed and left-handed transmission lines have electrical lengths with opposite signs respectively.