Co- and Cross-Polarization Decoupling Structure With Polarization Rotation Property Between Linearly Polarized Dipole Antennas With Application to Decoupling of Circularly Polarized Antennas

A decoupling structure with polarization rotation (DSPR) property is proposed to reduce the mutual coupling between co- or cross-polarized antennas. The proposed DSPR generates a neutralization wave with two orthogonally polarized components that can be controlled to cancel the original mutual coupling. The DSPR is placed above the arrays with orthogonal and parallel dipole elements. After applying the DSPR, the mutual coupling at the center frequency of 3.5 GHz is reduced to −40 dB for both arrays, and the overall mutual coupling is better than −26 dB within the band of 3.3–3.7 GHz, and the reflection coefficients remain below −12 dB. The antennas maintain stable radiation patterns within the operation bandwidth with a 0.5 dB increase of the realized gain. Since the DSPR can effectively reduce both co- and cross-polarization coupling, the mutual coupling between circularly polarized antennas in a
$1 \times 4$
array is reduced to below −35 dB thanks to the DSPR. Finally, a prototype of the antenna array with orthogonal dipole elements loaded with the DSPR is fabricated and measured. The measured results are in excellent agreement with the simulated ones, demonstrating the effectiveness of the proposed DSPR for isolation enhancement between cross-polarized antennas.