Low-Profile Wideband Millimeter-Wave Circularly Polarized Antenna With Hexagonal Parasitic Patches

A low-profile wideband circularly polarized (CP) millimeter-wave (mm-Wave) L-shaped dipole antenna with hexagonal parasitic patches is presented in this letter. Two types of hexagonal parasitic patches are placed round the rotationally symmetrical L-shaped dipole to enhance the impedance and axial ratio (AR) bandwidth. Based on this antenna element, a substrate integrated waveguide-fed 2 × 2 subarray with sequential rotate feeding technique is designed to further improve AR bandwidth. Finally, a 4 × 4 CP array is designed to further enhance the gain. The measurement shows the proposed array can achieve the impedance bandwidth of 27.7%, the AR bandwidth of 28.5%, and the peak gain of 17.85 dBic while maintaining a lower profile. Therefore, the design scheme will be suitable for 5G mm-Wave communications and satellite communication systems.