Bandwidth Enhancement of a Low Profile Antenna by Applying non-Uniformity to its High Impedance Ground Plane

A non-uniform high impedance surface (NU-HIS or tapered HIS) is proposed against a uniform HIS (U-HIS). The surfaces are one dimensional (1D) and made of parallel wires with a length a little less than half wavelength. To show the effects of the surfaces, a half wavelength dipole antenna is placed near three different surfaces, PEC, U-HIS, NU-HIS while the dipole height is fixed. These three EM problems are analyzed numerically by the method of moments (MoM) and are compared. It is observed that NU-HIS yields more bandwidth than U-HIS, while in both cases the structures have identical volumes and nearly identical gains. This effect is attributed to the decrease in sensitivity of the HIS to the incidence angle caused by applying non-uniformity to the elements radii