Compact circularly polarized slits-loaded microstrip patch antenna with symmetric-fractal boundary

Abstract

A novel single feed compact microstrip patch antenna with slits and symmetric-fractal boundary loading is proposed and investigated for circularly polarized (CP) radiation. The compact size of the antenna is realized by insetting four pairs of equally spaced slits of equal lengths to the boundary of square patch along the patch axis. Further size reduction and CP operation is achieved by symmetrically replacing the diagonal boundary of slits loaded square patch antenna with second order iteration fractal curves. By carefully selecting the fractal curve boundary of different indentation widths along the diagonal axis of the patch with respect to the proper feed point, the lowered dominant mode resonant frequency splits into two near-degenerate separate resonant frequencies resulting in circular polarization. The proposed CP antenna on low-cost FR-4 substrate with an overall volume of 0.23λ0 × 0.23λ0 × 0.03λ0 at 2.04 GHz is 57.15% miniaturized as compared to the conventional CP design. The simulated results show that the antenna exhibits a 10-dB impedance bandwidth of 2.02% and a 3-dB axial ratio (AR) bandwidth of 0.54% with a maximum gain of 2.03 dBic. The proposed compact antenna with good CP radiation characteristics finds applicability in modern compact wireless communication systems for S-band applications.