Impedance Matching of Rectangular Microstrip Antennas partially loaded with DNG metamaterials

A new structure for improving the bandwidth and impedance matching of subwavelength resonant rectangular microstrip antennas filled with double-positive material and double-negative metamaterials is presented. Due to the phase compensation properties of double-negative metamaterials, arbitrarily low resonant frequency can be obtained for a fixed dimension. However, the antenna does not radiate efficiently because of the radiation from the two radiating edges cancels each other. An extra double-positive material slab is inserted between the radiator and substrate to reverse the axial electric fields at the radiating edges and hence to improve the input impedance characteristics. The input impedance of the proposed structure is studied using finite-difference time-domain method.