Broadband Planar Antenna Combining Monopole Element with Electromagnetic Bandgap


IEICE TRANSACTIONS on Electronics   Vol.E91-C   No.11   pp.1778-1785
Publication Date: 2008/11/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e91-c.11.1778
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Microwave and Millimeter-wave Technologies)
antenna,  EBG,  monopole,  planar,  microwave,  

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New structure of broadband planar antenna, combining monopole elements with electromagnetic bandgap (EBG) structures, is proposed. The antenna has a simple single layer structure and unique beam pattern. Antenna is fabricated on a surface of a single layer dielectric substrate and back side of the substrate is covered with metal layer. At the center of the substrate, an inverted L monopole strip is fabricated and on both sides of this monopole, EBG unit cells are placed. By tuning monopole length and EBG bandgap frequency, the monopole resonates even if metal layer exists close to the monopole radiator. Three types of EBG, one dimensional (1D), square two dimensional (2D) and hexagonal 2D, are tested. By combining monopole strip with hexagonal 2D-EBG, the bandwidth of prototype antenna, whose return loss is less than 10 dB, is 840 MHz in 5 GHz band. To control beam patterns of antenna, parasitic elements are placed close to the monopole radiator and EBGs. These parasitic elements work as directors of quasi Yagi-Uda antenna and radiation gain at lower tilt angles is improved.