18-40 GHz Circularly Polarized Antenna Using Ultra-Wideband Dielectric Polarizer

A circularly polarized (CP) antenna operating from 18 to 40 GHz is presented. The ultra-bandwidth (UWB) performance is realized by a novel dielectric polarizer design that has a relatively large unit-cell width compared to the wavelength. The phase difference of the proposed polarizer has a non-linear growth rate to frequency at the high-frequency range, leading to a bandwidth expansion of effective polarization rotation. Apart from the polarizer, the CP antenna includes a hyperbolic lens for wavefront manipulation and two impedance transitions for reducing the reflection coefficient at the polarizer surface. Measurement results show that the antenna has an ultra-wide operating bandwidth of 76% from 18 to 40 GHz.