Antenna Polarization
Understanding Antenna Polarization
Polarization determines how the electric field of the radiated wave is oriented in space. It is one of the most important antenna parameters because mismatched polarizations between transmitter and receiver cause signal loss.
Polarization Types
- Linear vertical: E-field vertical. Monopoles, vertically oriented patches.
- Linear horizontal: E-field horizontal. Horizontal dipoles, H-plane horn orientation.
- RHCP: E-field rotates clockwise (looking from behind the antenna). Helix, CP patch.
- LHCP: E-field rotates counter-clockwise. Reverse-wound helix.
Polarization Mismatch Loss
| TX Pol | RX Pol | Mismatch Loss |
|---|---|---|
| V | V | 0 dB |
| V | H | Infinite (total loss) |
| V | RHCP | 3 dB |
| RHCP | RHCP | 0 dB |
| RHCP | LHCP | Infinite (total loss) |
Frequently Asked Questions
What is antenna polarization?
Antenna polarization is the orientation of the radiated E-field: linear (V or H), circular (RHCP or LHCP), or elliptical. Matched polarization gives zero mismatch loss. Cross-polarized antennas (V vs H, RHCP vs LHCP) have theoretically infinite loss.
Why use circular polarization?
CP eliminates the need for alignment between TX and RX polarizations. A CP antenna receives any linearly polarized signal with only 3 dB loss. CP is also immune to Faraday rotation in the ionosphere. Used for satellite, GPS, and radar.
What is axial ratio?
Axial ratio is the ratio of major to minor axis of the polarization ellipse. Perfect CP has AR = 1 (0 dB). Perfect LP has AR = infinity. Practical CP antennas achieve AR < 3 dB (axis ratio < 1.41). Lower AR means more circular (better CP).