An Endfire Circularly Polarized Millimeter-Wave Phased Array Antenna With Multiple Tilted Directors for Wide-Angle Scanning and Improved Axial Ratio

In this letter, a millimeter-wave planar endfire circularly-polarized (CP) array antenna (ECPAA) is proposed using multiple tilted-arranged directors (TADs) for wide-angle scanning and improved axial ratio. Initially, an endfire CP substrate-integrated waveguide (SIW) antenna element with a width of less than half a wavelength explores TADs to realize beam inclination. Specifically, the loaded directors feature three pairs of metal patches printed on opposing sides of dielectric substrate, which are interconnected via two metallized vias. In contrast to conventional method of increasing antenna gain by incorporating additional directors, the proposed planar ECPAA introduces a distinctive design that symmetrically positions eight columns of directors in a divergent configuration in front of the array. This approach not only significantly expands the scanning angle range, but also improve the axial ratio during large angle scanning, offering a novel solution for wide-angle scanning of circularly polarization. As a validation, a prototype of the array is fabricated and tested, yielding results that are in good agreement with simulated results. The proposed CP endfire array demonstrates an excellent beam scanning range of ±65°. With the merits of endfire radiation, wide-angle scanning, and circular polarization, the proposed antenna has promising usage for for installation on automobiles, low-altitude economic platforms, and terminal equipment in mm-wave systems.