crosspolarized

Crosspolarized describes electromagnetic radiation whose polarization is orthogonal to a reference polarization. In optics and imaging, this term is used when light passes through a polarizer and analyzer set at right angles, producing minimal transmitted intensity. In radio and microwave engineering, cross-polarization refers to the component of a radio signal whose electric field is polarized perpendicular to the intended or transmitted polarization.

In antenna systems, cross-polarization is usually undesired and can reduce received signal power and cause interference, especially in dual-polarized or polarization-multiplexed links. The quality can be summarized by cross-polarization discrimination (XPD), the ratio, typically expressed in decibels, of the co-polarized component to the cross-polarized component.

Causes include misalignment of feeds, mechanical tilt, structural asymmetries, multipath propagation, reflections from ground or structures, and imperfections in the antenna or feed network. Frequency-dependent and environment-dependent; cross-pol can vary with pointing angle and elevation.

Applications and mitigation: In some systems, cross-polarization is deliberately employed to double capacity by polarization-division multiplexing, using orthogonal polarizations such as horizontal vs vertical, or right- and left-hand circular polarization. In reception, polarization diversity or dual-polarized antennas help mitigate fading. Mitigation approaches include precise installation, high-quality feeds, circular polarization, shielding of feeds, and digital signal processing to separate polarizations.

In optics, crossed polarizers (analyzer and polarizer at 90 degrees) yield near-zero transmission, a principle used in contrast enhancement, stress analysis with birefringent materials, and certain imaging techniques.