A Wideband Multi-Polarized Microstrip Antenna with High Polarization Isolation Based on Dual-Circular Polarization

To address the limited overlapping bandwidth across polarization modes in conventional multi-polarized antennas, this paper proposes a wideband multi-polarized microstrip antenna with high polarization isolation. Based on the theory of orthogonal dual-circular polarization synthesis, the proposed antenna achieves left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) under a single-port excitation mode, and can generate arbitrary linear polarization (LP) by simply adjusting the phase when dual-fed. For verification, a prototype operating at the C-band is designed, fabricated, and measured. The measured results agree well with the simulations. For linear polarization, the measured 10 dB bandwidth ranges from 4 GHz to 8 GHz (relative bandwidth of 66.7%), with polarization isolation exceeding 26 dB. For circular polarization, the measured bandwidth (for 10 dB return loss and 3 dB axial ratio) spans 4.1-8 GHz (relative bandwidth of 64.5%), with polarization isolation greater than 15 dB. The linear polarization gain is slightly higher than the circular polarization gain, with a maximum gain of 4.3 dB. The proposed antenna simultaneously features multi-polarization, a wide bandwidth, a low profile (0.03 λ₀), and high polarization isolation, which can meet the urgent demand for multi-polarized antennas in modern multi-functional integrated wireless systems, such as communication systems, radar, and unmanned aerial vehicles (UAVs).