Miniaturized Tapered EBG Structure With Wide Stopband and Flat Passband

In this letter, a miniaturized tapered electromagnetic band-gap (EBG) structure with wide stopband and flat passband is presented. Chebyshev tapered EBG distribution is adopted to minimize ripples in the passband caused by the periodicity of planar EBG structure. The defected ground structure (DGS) is employed for enlarging the bandwidth of stopband and reducing the size of EBG patterns. Two transmission zeros are introduced by spurline and open stubs to get higher attenuation level. In comparison with traditional planar EBG structure, compact size, flat passband, and wide stopband are achieved in the proposed design. Measured and simulated S-parameters indicate that the proposed design has a relative fractional bandwidth of 93.7% in the stopband below -20 dB.