Circular polarization

Circular polarization is a state in which an electromagnetic wave’s electric-field vector rotates in a circle in the plane perpendicular to its direction of travel. It results from two perpendicular field components of equal amplitude with a quarter-cycle phase difference.

Linear polarization: A polarization state in which an electromagnetic wave’s electric field oscillates along a fixed line perpendicular to its direction of travel. Equal perpendicular components produce this state when their phase difference is zero or half a cycle.
Electromagnetic wave: A propagating disturbance of electric and magnetic fields that transports energy through space or a medium. Circular polarization describes the changing direction of this wave’s electric field.
Circularly polarized antenna: An antenna designed to transmit or receive electromagnetic waves with circular polarization. Its rotating field supports links where transmitter and receiver orientations may vary.
Unpolarized light: Light whose polarization direction varies randomly over time or across the measured ensemble. Unlike a single circularly polarized wave, it has no fixed field-rotation state.
Zeeman effect: The splitting of atomic spectral lines by a magnetic field. Radiation viewed along the field can contain oppositely handed circularly polarized spectral components.
Elliptical polarization: A polarization state in which an electromagnetic wave’s electric-field vector traces an ellipse in the transverse plane. Circular polarization is the special case with equal component amplitudes and a quarter-cycle phase difference.
Electric field: A vector field that exerts electric force on charged particles. Its direction and magnitude define the instantaneous state of polarization.
Satellite communication: The transmission of information between Earth stations and satellites using radio waves. Circular polarization can reduce losses from changing antenna orientation and some propagation effects.
Partially polarized light: Light containing both polarized and unpolarized components, described by a degree of polarization between zero and one. A beam can contain circular polarization without being purely circularly polarized.
Pulsar: A rotating neutron star that emits beams of electromagnetic radiation observed as periodic pulses. Pulsar radio signals can contain measurable circular polarization that reveals magnetized emission conditions.

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