A Wideband Dual-Polarized Endfire Antenna Array with High Isolation for Beam Steering Applications

In this paper, a dual-polarized endfire antenna with high isolation is proposed for millimeter-wave beam steering applications. A ridge SIW is formed by incorporating a metal septum into the middle layer of two stacked SIWs. Based on this ridge SIW, a dual CP antenna is subsequently designed using the stepped septum polarizer, and additional metasurfaces and metal blocks are introduced to improve impedance matching. Then, a SIW magic-T is integrated into the dual CP antenna as 180° coupler to achieve dual linearly polarized (LP) radiation. The proposed dual LP antenna achieves a working bandwidth from 24 to 30 GHz and the isolation is higher than 35 dB. Compared with traditional design, the single substrate thickness of the proposed antenna is reduced by 37.5%. Then, a
$1\times 4$
multibeam array is constructed to evaluate the beamforming capability. The measured overlapping bandwidth for both polarizations is from 24.5 to 30 GHz. The measured isolation is better than 28 dB in the entire working bandwidth and mutual coupling between co-polarized ports is less than −18 dB. The measured scanning beams of both polarizations are capable of covering ±40° within 3-dB gain variation at 28 GHz. The measured peak gains of vertical and horizontal polarizations are 9.6 and 10 dBi, respectively.