Broadband Circularly Polarized Microstrip Patch Antenna With Diamond-Shaped Artificial Ground Structure

This paper presents a broadband circularly polarized patch antenna with an artificial ground structure (AGS), which has rotated rectangular unit cells with respect to the sides of the rectangular ground plane, as a polarizer. A two-element ( $2\times 1$ ) array configuration of the antenna is also presented. The rectangular unit cells are rotated by 45° with respect to the sides of a square dielectric substrate, named a diamond-shaped AGS (DAGS). The overall dimensions of the AGS are smaller than those of the ground plane. The rotated unit cells and the smaller AGS patch dimensions effectively suppress surface wave resonance on the AGS. The proposed antenna achieves a wide 3-dB axial ratio bandwidth in the boresight direction. The proposed design has a flatter gain curve in the operating frequency band compared to that for conventional designs. It is found that the array configuration outperforms the single-element structure.