A design of broadband circularly polarized directional antenna using cavity reflector

With the development of 5G communication, broadband technology has received more and more attention. As an important part of wireless communication systems, antennas are particularly important for broadband research. In this paper, a broadband circularly polarized directional antenna using cavity reflector is proposed. The antenna consists of an array of four rectangular patches and a metal cavity located below. The central axes of the patches are orthogonal to each other. Four rectangular patches evenly arranged on the upper surface of the square dielectric plate. The lower surface of the dielectric plate is an annular GND shared by the patches. The four rectangular patches are respectively fed by four SMA connectors. In order to make the antennas circularly polarized, the feeding phases of the SMA connectors are sequentially different by 90. In order to directional radiation of the antenna, a square metal cavity as the reflector is loaded directly below the dielectric plate. The simulation results show that the antenna has a VSWR ≤ 2 bandwidth of 1.91-5.7 GHz (99.6%), and the axial ratio is ≤ 1 dB in the same bandwidth, the 3 dB gain bandwidth is 2.31-5.24 GHz (77.6%), and the maximum gain is 8.96 dBi. Therefore, the antenna has a wide VSWR bandwidth, axial ratio bandwidth, and 3 dB gain bandwidth. The size of the antenna is 55 ∗ 55 ∗ 25 mm³ and it can meet the size of the radiation surface smaller than λ₀ at 2.31-5.24 GHz. Therefore, the antenna is compact and suitable as a unit of the array.