1-Bit Circularly Polarized Transmit-Array with Orthogonal Elements in X Band

In this paper, we present two universal layout schemes for designing a 1-bit circularly polarized (CP) transmit-array utilizing only a single phase-modulated layer. These schemes eliminate the correlation of co- and cross-polarization phase patterns caused by 1-bit phase discreteness in the CP array, effectively preventing cross-polarization beam in the same direction. As a proof of concept, a broadband CP transmit-array antenna with goodish polarization purity beams is designed in X-band around 10 GHz. Compared to a uniform element array, the staggered placement of two orthogonal 1-bit elements significantly improves the cross-polarization discrimination (XPD), achieving a 3 dB axial ratio bandwidth of 32.7%. The performance of wide-angle scanning beams up to 60° further validates the effectiveness. The proposed schemes could be used for CP reconfigurable array antennas, enabling electronic beam-steering with just a single phase-modulated functional layer.