Design of low profile broadband circularly polarized planar monopole antenna based on AMC

In this paper, a low-profile, broadband, circularly polarized planar monopole antenna with directional radiation is designed based on Artificial Magnetic Conductor (AMC) reflector. The antenna radiating layer utilizes a cross-shaped monopole as the feed structure. By slotting the ground plane and adding extension branches, it disrupts the current path, forming two orthogonal electric field components that produce circular polarization radiation.Additionally, the cross-shaped feed structure optimizes current distribution and improves impedance matching. The Split-Ring Resonator (SRR) structure regulates the electromagnetic field distribution through its resonant characteristics, enhancing the antenna's axial ratio.The square annular AMC reflector is located directly below the radiation layer as the reflection layer of the antenna. This design not only realizes efficient directional radiation, but also effectively reduces the overall profile of the antenna. Simulation and test results indicate that the antenna has 48.6% (4.09~6.72 GHz) impedance bandwidth and an Axis ratio bandwidth of less than 3dB of 38% (4.11~6.04 GHz), and the max gain can be up to 8.0 dBic. The profile height of the antenna is 0.13λ₀. (λ₀ is the wavelength of electromagnetic wave in vacuum)