Millimeter-Wave Endfire Circularly Polarized Phased Array for Wide-Angle Scanning Using Heterogeneous Radiating Element

This letter presents a 1×8 millimeter-wave planar endfire circularly-polarized (CP) phased array with enhanced scanning capabilities using some heterogeneous radiating elements. The proposed CP element features a hybrid structure combining substrate-integrated waveguide (SIW), an inclined printed dipole, and an angularly optimized reflector. Eight such elements are symmetrically arranged around the array center to form the scanning platform. Inspired by conformal phased arrays, the design innovatively inclines the dipole and reflector around their midpoints, emulating the stable effective aperture of conformal arrays while retaining the benefits of a planar configuration. A prototype array of size 1.6λ₀×3.7λ₀×0.2λ₀ is fabricated and tested. Both simulated and measured results demonstrate a CP scanning coverage of ±62°, significantly surpassing conventional arrays. This design offers a practical solution for millimeter-wave applications requiring wide-angle scanning with planar geometry and endfire circular polarization.