Dual-Polarized Ka-Band Phased Array Using Hybrid Magnetic-/Electric-Dipole With Low Profile for Low Cross-Polarization Leakage Inside ±60° Scan Volume

Abstract

This paper presents a 26–40-GHz 16×16 dual-polarized phased array. For the dual-polarized phased array antennas, the sources of cross-polarization leakage mainly include the polarization coupling from the feedlines and the radiators. Electric dipole (E-dipole) and magnetic-dipole (M-dipole) are the most common radiators, which both suffer from the deteriorated polarization isolation when scanning in D-plane. Here, the hybrid M-/E-dipole is employed to overcome this issue. To avoid the serious cross-polarization leakage from the typical 1/4 wavelength feedline of E-dipole, the M-dipole is chosen to form the primary radiator with the typical 1/10 wavelength feedline. Therefore, the excited electric-/magnetic-current field vectors on the radiators and the feedlines can be significantly weakened. However, the low-profile M-dipole introduces the half-patch TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode due to the coupling between the horizontal feedline and the ground plane. This parasitic radiation mode with the slant polarization seriously deteriorates the polarization isolation of the M-dipole. The shorted posts are employed to suppress the half-patch TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode without breaking the M-dipole mode. Through that, the high polarization isolation characteristic of the dual-polarized M-dipole radiator is maintained. Then, the double-layer meta-surface (MS) is designed to act as the secondary radiator, i.e. the E-dipole. The MS also plays the role of the impedance matching layer. Based on these methods, the cross-pol. level better than {–66, –59, –52} dB in E-/H-planes and {–66, –28, –17} dB in D-plane when scanning to {broadside, 30°, 60°} is achieved, respectively.