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What Is a Polarization Antenna?

An antenna is a type of transducer or, in other words, a device that receives a signal in the form of one type of energy and converts it to another form. Specifically, an antenna converts electrical current into electromagnetic waves that are radiated into space. The way in which the waves are radiated is known as the antenna's polarization. Generally speaking, antennae use linear -- vertical or horizontal straight line -- or circular polarization.

Vertical Polarization
- A vertical polarization antenna has its electric field perpendicular, or at 90 degrees, to the surface of the earth. This type of antenna is often used to radiate a radio signal in all directions, such as from a broadcast tower for amplitude modulation, or AM, radio. Vertical polarization is effective in rural areas, especially where the topography includes hills or mountain, and is used for most surface-to-surface communications in the frequency range above 30 megahertz.
Horizontal Polarization
- A horizontal polarization antenna, on the other hand, has its electric field parallel to the surface of the earth. This type of antenna is used to broadcast television signals in the United States, partly so that television reception does not suffer interference from vertically polarized signals, such as mobile radio, and partly because most man-made electrical noise tends to be vertically polarized.
Circular Polarization
- A circular polarization antenna radiates electromagnetic waves in the vertical and horizontal planes and all planes in between. In other words, the plane of polarization rotates, in a corkscrew pattern, through a full 360 degrees during each wavelength.
  Circular polarization is typically used for satellite communications because, unlike a vertically or horizontally polarized radio wave, a circularly polarized wave cannot be rotated as it travels through a region of the earth̵7;s upper atmosphere, known as the ionosphere. Circular polarization keeps the signal constant if a satellite appears to move in relation to a fixed antenna on the surface of the earth.
Considerations
- Antenna polarization is an important factor when selecting and installing an antenna and knowing the difference between the various types of polarization can help you to maximize the performance of your wireless communication system. Circular polarization antennae are typically less susceptible to the effects of reflectivity, absorption, inclement weather and line-of-sight obstructions -- all of which weaken signal strength and make communication links difficult to establish and maintain -- than their vertical and horizontal polarization counterparts.

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