A wideband millimeter-wave CP antenna with gain enhancement

This paper presents two wideband millimeter wave antennas with circular polarization and high gain performance. The first antenna consists of a linear polarization antenna source and a cylindrical dielectric polarizer. Some slots are cut from the dielectric polarizer to switch the linear polarization into circular polarization. Moreover, the polarizer can be used to enhance the gain of the antenna. By tuning the thickness and the relative permittivity of the dielectric polarizer, the gain can be easily enhanced. In order to suppress the sidelobe level of the radiation pattern, the second antenna is proposed by replacing the cylindrical polarizer with a tapered polarizer. To verify our concept, the antennas were fabricated by using 3D printed technology. The measured results show that the proposed antennas achieve a wide impedance bandwidth of 50% an overlapped axial ratio bandwidth of 30%. The maximum gain of the antenna reaches to 16 dBic. The ultimate goal of this work is to develop a wideband, high-gain and low-cost antenna for the millimeter-wave frequency band, which is a good candidate for 5G communication.