Design and analysis of circularly polarized circular patch antenna with multiple shorting pins using characteristic mode theory

Abstract

In this paper, we design a single-layer single-feed Circularly Polarized (CP) circular patch antenna with loading of shorting pins. At first, metallic pins are symmetrically placed in a circular patch resonator, and a characteristic mode analysis is carried out. Then, current distributions are studied for a circular patch with four shorting pins, and the pins are slightly shifted to excite two orthogonal degenerate modes simultaneously for CP wave radiation. Finally, the CP circular patch antenna with four shorting pins and optimal feed position is designed to enhance the antenna gain. The proposed antenna has a compact size with dimensions of 0.49λ 0 × 0.49λ 0 × 0.0147λ 0 at 2.76 GHz. According to this study, we can determine the best place of the pins for obtaining the circular polarization. The return loss and radiation properties are measured and compared with simulation results. The proposed antenna has a 3 dB axial ratio bandwidth of 1.8% (2.73–2.78 GHz). The measured gain is 6.1 dBic at 2.76 GHz. The importance of this study is that we can predict the behavior of the antenna with a different number of shortening pins for defining the resonance frequency and obtaining circular polarization.