A 3-D-Printed Wideband Circularly Polarized Parallel-Plate Luneburg Lens Antenna

This communication presents a 3-D-printed wideband parallel-plate circularly polarized Luneburg lens (LL) antenna. The proposed structure of dielectric posts truncated by two metallic parallel plates serves not only as a LL, but also as a wideband linear-to-circular polarizer. The permittivity variation of the LL is realized by positioning dielectric posts with various radius (r) based on the optics theory and the effective medium theory (EMT). On the other hand, the desired circular polarization is realized by exciting two orthogonal propagating modes with different phase constants thanks to the integrated parallel plates. To verify our concept, a prototype was fabricated using 3-D-printing technology. Based on the measurement results, the proposed antenna achieves an overlapped bandwidth of 43% (21-32.5 GHz) in terms of the reflection coefficients lower than -10 dB and the axial ratios smaller than 3 dB. Good agreement between simulation and measurement is obtained.