Novel Flexible Dual-Frequency Broadside Radiating Rectangular Patch Antennas Based on Complementary Planar ENZ or MNZ Metamaterials

A novel scheme of designing dual-frequency broadside radiating rectangular patch antennas is proposed. Cavity model analysis shows that, by partially loading Lorentzian dispersive epsilon-near-zero (ENZ) or mu-near-zero (MNZ) metamaterials (MTM), the electric fields at two radiating edges of the patch antennas can be out of phase and a broadside radiation pattern can be achieved at both operating frequencies. With proper constitutive parameters and filling ratio, the frequency ratio (FR) of the dual-frequency antenna can be flexibly chosen in a very wide range. Experimental results of a double positive (DPS)-MNZ based dual-frequency patch antenna, with its MNZ practically implemented by a complementary electric-LC (CELC) array etched on the patch surface, demonstrates the validity of such scheme. A detailed design procedure is also described. Compared to some conventional and other MTM based techniques, the proposed dual-frequency solution shows its advantages on excellent broadside radiating pattern with low cross-polarization and reduced back lobe, FR flexibility, and ease of fabrication.