A Wide-Angle-Scanning Large-Spacing Phased Array with Multi-Polarization and Grating-Lobe Suppression

In this article, an X-band wide-angle-scanning large-spacing phased array with grating-lobe suppression based on low-profile quad-polarization null reconfigurable (QPNR) elements is proposed. The key novel contributions are as follows. First, the QPNR element composed of four dipoles, a dual-polarization (DP) microstrip patch and a quasi-monopole can provide four radiation channels to achieve DP beams in zenith and horizontal regions independently. Second, by adjusting the amplitude weight ratio and phase difference of the four independent channels, the null synthesis of linear polarizations (LPs) and circular polarizations (CPs) can be realized at different angles, supporting the grating-lobe suppression in phased array design. Third, a typical QPNR-element-based 1×8 linear phased array with element spacing of 0.85λ₀ is designed, fabricated and experimentally verified within the band of 8.3-8.7 GHz. The results show a beam scanning range of ±75° without grating lobe under both dual-LP and dual-CP operating modes. The grating-lobe levels are reduced by more than 9.7 dB compared to that of the array only using DP microstrip patch elements. The gain drop at the maximum scanning angle is less than 4.2 dB. The good performance of multi-polarization wide-angle scanning and grating-lobe suppression make this array a potential option in radar and communication applications.