Browse Definitions :
Definition

directional antenna

A directional antenna is a radio-frequency (RF) wireless antenna designed to function more effectively in some directions than in others. The purpose of that directionality is improving transmission and reception of communications and reducing interference. 

In consumer applications, the most common directional antenna is the dish used with satellite Internet and satellite television installations. Other types of directional antennas, such as the Yagi antenna, quad antenna, billboard antenna, and helical antenna, are used in a variety of applications. For example, a Yagi antenna that is mounted outdoors can work well for a wireless Internet connection in a remote area, because the Yagi drastically improves the range compared with a conventional indoor antenna.

For most terrestrial wireless communications purposes, antenna directionality matters only in the azimuth, or horizontal, plane. For satellite and space-communications applications, both the azimuth and elevation (angle above the horizon) are important. A straight, vertically-oriented antenna such as a dipole measuring 1/2 wavelength from end-to-end is omnidirectional in the azimuth plane, meaning that it radiates and receives equally well in all horizontal directions. In any elevation plane, however, a vertical dipole exhibits the most gain parallel to the earth's surface and the least gain directly upward. A horizontally oriented dipole antenna produces more gain off the sides than off the ends in the azimuth plane, so it is bidirectional for terrestrial communications purposes. Horizontal dipole antennas find favor primarily among amateur radio operators.

Directional antennas usually exhibit unidirectional properties. In other words, their maximum gain (increase in efficiency) occurs in a single direction. So-called bidirectional antennas have two high-gain directions, usually oriented opposite to each other in space. An omnidirectional antenna radiates or intercepts radio-frequency (RF) electromagnetic fields equally well in all horizontal directions in a flat, two-dimensional (2D) geometric plane.

 

Continue reading about directional antennas:

Cisco Systems discusses the characteristics of directional antennas versus omnidirectional (nondirectional) antennas.

Engadget describes the construction of a homemade dish antenna for wireless Internet use.

YagiAntenna.net explains how a Yagi works.

This was last updated in February 2012

SearchCompliance

  • compliance risk

    Compliance risk is an organization's potential exposure to legal penalties, financial forfeiture and material loss, resulting ...

  • information governance

    Information governance is a holistic approach to managing corporate information by implementing processes, roles, controls and ...

  • enterprise document management (EDM)

    Enterprise document management (EDM) is a strategy for overseeing an organization's paper and electronic documents so they can be...

SearchSecurity

  • information security (infosec)

    Information security, often shortened to infosec, is the practice, policies and principles to protect data and other kinds of ...

  • denial-of-service attack

    A denial-of-service (DoS) attack is a security event that occurs when an attacker makes it impossible for legitimate users to ...

  • user authentication

    User authentication verifies the identity of a user attempting to gain access to a network or computing resource by authorizing a...

SearchHealthIT

SearchDisasterRecovery

  • risk mitigation

    Risk mitigation is a strategy to prepare for and lessen the effects of threats faced by a business.

  • call tree

    A call tree is a layered hierarchical communication model that is used to notify specific individuals of an event and coordinate ...

  • Disaster Recovery as a Service (DRaaS)

    Disaster recovery as a service (DRaaS) is the replication and hosting of physical or virtual servers by a third party to provide ...

SearchStorage

  • cloud storage

    Cloud storage is a service model in which data is transmitted and stored on remote storage systems, where it is maintained, ...

  • cloud testing

    Cloud testing is the process of using the cloud computing resources of a third-party service provider to test software ...

  • storage virtualization

    Storage virtualization is the pooling of physical storage from multiple storage devices into what appears to be a single storage ...

Close