A novel design on broadband circularly polarized microstrip antenna

A square array of air columns is embedded in a dielectric substrate to form the photonic-bandgap (PBG) structure and the band-gap of such a PBG structure is analyzed at first. Then a broadband circularly polarized antenna based on the PBG structure is introduced. Through selecting appropriate lattice period and air column radius, the surface wave can be suppressed effectively and the circularly polarized characteristic can be improved when the resonant frequency (f = 12.5 GHz) of the antenna fell in the band-gap of the PBG structure. After calculating and testing, the 20.6% (VSWR [lt] 2) bandwidth and 27.4% 3-dB axial ratio bandwidth are achieved, respectively. Such circularly polarized antenna can be used extensively in communications field. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 954–957, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23257