Wideband and Low Direct-Coupling Tapered Slot Antenna Using Electromagnetic Bandgap Structures

This paper proposes a wideband and low direct-coupling tapered slot antenna (TSA) using electromagnetic bandgap (EBG) structure. We name this antenna the EBG-TSA. In some near field imaging systems including ground penetrating radars, a number of TSAs are arranged into an array with very small spacing in order to realize high-resolution imaging without synthetic aperture processing. Then, the direct coupling among TSA elements is nonnegligible and harmful. In this paper, we show that the EBG structure is effective in reducing the direct coupling with its stopband, which prevents an electromagnetic wave from propagating in a specific frequency band. Our EBG-TSA reduces its direct coupling by 3 dB or more in a wide band. We also find that the tapered EBG structure area assists the radiation by guiding the fin current flow two-dimensionally along the tapered slot so that the boresight gain increases. The EBG structure contributes to both the direct coupling reduction and the boresight gain enhancement.