What is antenna polarization?
Polarization is the figure traced by the electric field vector of a radiated wave over time, observed in the direction of propagation. It may be linear, circular (right- or left-hand) or elliptical. Axial ratio (major/minor axis) is 1 (0 dB) for perfect circular polarization. Polarization mismatch loss is PLF = |êt·êr|²; for two linear antennas at angle ψ, PLF = cos²ψ.[1][2]
What losses occur from polarization mismatch?
- Linear to linear at 90°: theoretically infinite (in practice limited by cross-polar levels, often 20–30 dB).
- Linear to circular: 3 dB.
- RHCP to LHCP: theoretically infinite isolation.
Why is circular polarization used?
It is insensitive to the relative rotation of transmitter and receiver and to Faraday rotation in the ionosphere, so satellite links and GNSS use it; GPS uses right-hand circular polarization.[3] Reflection from a surface reverses the handedness, helping reject some multipath.
How is polarization produced?
Linear: dipoles, monopoles, single-fed patches. Circular: crossed dipoles fed 90° apart, helical antennas in axial mode, patches with truncated corners or dual quadrature feeds. Dual-polarized antennas (±45° slant in base stations) support polarization diversity and MIMO.[2]
Frequently asked questions
What axial ratio is acceptable?
Often below 3 dB for circularly polarized antennas.
Why do base stations use ±45° slant?
For polarization diversity with two orthogonal channels.
Does reflection change polarization?
Yes; circular handedness reverses at each specular reflection.
See also
References
Online sources accessed October 21, 2026; printed works cited by edition. See all sources.
- “IEEE Standard for Definitions of Terms for Antennas (IEEE Std 145)”. IEEE. 2013 revision.
- “Antenna Theory: Analysis and Design, 4th ed.”. C. A. Balanis, Wiley. 2016.
- “IS-GPS-200 / IS-GPS-705: Navstar GPS Space Segment / User Segment Interface Specifications”. U.S. Space Force / GPS Directorate. current revisions.