A Novel Anisotropic Uniplanar Compact Photonic Band-Gap (UC-PBG) Ground Plane

A novel anisotropic UC-PBG structure, presenting a propagation direction and an attenuation direction and characterized by a period much smaller than wavelength, is introduced as a ground plane for a microstrip line. Simulated and measured transmission parameters of the resulting structure show good transmission in the propagation direction and strong rejection in the attenuation direction over a bandwidth of about 35%, an excelent insensitivity to the line position in both directions, a classical line and slow-wave behavior for the effective wavenumber in the propagation and attenuation directions, respectively, and a progressive variation of the transmission characteristics as a function of the angle of the line on the PBG. The gaps in the attenuation direction are shown to be very deep and to exhibit a very sharp cutoff despite the extremely small size of the overall structure.