3-D Printed Annular Linear-to-Circular Dielectric Polarizer and Its Applications to Omnidirectional and Multibeam Antennas

This article presents a 3-D printed dielectric polarizer. It is constituted by a number of annually arranged dielectric slabs, and each slab is 45° rotated with respect to the azimuth plane. It is able to transform the polarization state of the waves in azimuth plane from linear to circular. Based on the polarizer, two circularly polarized (CP) antenna designs are proposed. One of them is an omnidirectional CP antenna, and the other is a multibeam CP antenna with capability of full azimuthal scanning. They are fed by a dielectric filled biconical structure and six corner reflectors, respectively. Their polarizers are individually designed with different geometric parameters. Both antennas are one-piece configurations and can be directly 3-D printed without assemblies in later stage. Partial surfaces of the antennas are coated with copper films by an electroplating technique to act as the necessary metal components. To validate the design ideas, two prototypes are demonstrated in X-band. Experimental results show that the omnidirectional antenna can achieve a wide 3 dB axial ratio (AR) bandwidth of 28.3% from 8.5 to 11.3 GHz and a peak gain of 3.3 dBic. Meanwhile, the multibeam antenna is with a wide 3 dB AR bandwidth of 22.4% from 8.7 to 10.9 GHz and a peak gain of 9.2 dBic. Within the AR bandwidth, the AR values in full azimuth plane are lower than 3 dB.