Design of a wideband circularly polarized millimeter-wave antenna with an extended hemispherical lens

This communication presents a design of a wideband and high-gain circularly polarized (CP) extended hemispherical lens antenna for millimeter-wave applications. The proposed lens integrated with a dielectric polarizer can transfer an incident wave from linear to CP over the wide operating bandwidth. This design is different from the cascaded design of a polarizer with an extended hemispherical dielectric lens. In this design, only one device is required to achieve dual functions. Therefore, size reduction and loss reduction can be obtained. Besides, thanks to the low-cost 3-D printed technology, the polarizer can be fabricated in an accurate and convenient way. A theoretical analysis is carried out. Equations are derived based on refraction law. For demonstration, the proposed CP lens antenna is implemented and measured. This antenna achieves a wide impedance bandwidth of 27% from 51 to 67 GHz for the reflection coefficient <-10 dB and a wide axial ratio (AR) bandwidth of 29% from 50 to 67 GHz for the AR <3 dB. The gain of the antenna can reach to 21 dBic, which agrees with our analysis. The ultimate goal of this communication is to develop a wideband, high-gain, small size and low-cost lens antenna for the millimeter-wave frequency band.