Browse Definitions:
Definition

directional antenna

Contributor(s): Stan Gibilisco

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

Start the conversation

Send me notifications when other members comment.

By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy

Please create a username to comment.

-ADS BY GOOGLE

File Extensions and File Formats

Powered by:

SearchCompliance

  • PCAOB (Public Company Accounting Oversight Board)

    The Public Company Accounting Oversight Board (PCAOB) is a Congressionally-established nonprofit that assesses audits of public ...

  • cyborg anthropologist

    A cyborg anthropologist is an individual who studies the interaction between humans and technology, observing how technology can ...

  • RegTech

    RegTech, or regulatory technology, is a term used to describe technology that is used to help streamline the process of ...

SearchSecurity

  • email spam

    Email spam, or junk email, is unsolicited bulk messages sent through email with commercial, fraudulent or malicious intent.

  • distributed denial of service (DDoS) attack

    A distributed denial-of-service attack occurs when an attack originates from multiple computers or devices, usually from multiple...

  • application whitelisting

    Application whitelisting is the practice of identifying applications that have been deemed safe for execution and restricting all...

SearchHealthIT

  • athenahealth Inc.

    Based in Watertown, Mass., athenahealth Inc. is a leading vendor of cloud-based EHRs for small to medium-sized physician ...

  • Affordable Care Act (ACA or Obamacare)

    The Affordable Care Act (ACA) is legislation passed in 2010 that changed how uninsured Americans enroll in and receive healthcare...

  • HIPAA Privacy Rule

    The Standards for Privacy of Individually Identifiable Health Information, commonly known as the HIPAA Privacy Rule, establishes ...

SearchDisasterRecovery

  • disaster recovery as a service (DRaaS)

    One approach to a strong disaster recovery plan is DRaaS, where companies offload data replication and restoration ...

  • data recovery

    Data recovery restores data that has been lost, accidentally deleted, corrupted or made inaccessible. Learn how data recovery ...

  • disaster recovery plan (DRP)

    A company's disaster recovery policy is enhanced with a documented DR plan that formulates strategies, and outlines preparation ...

SearchStorage

  • yottabyte (YB)

    A yottabyte is a measure of theoretical storage capacity and is 2 to the 80th power bytes, or, in decimal, approximately 1,000 ...

  • Kilo, mega, giga, tera, peta, exa, zetta and all that

    Kilo, mega, giga, tera, peta, exa, zetta are among the list of prefixes used to denote the quantity of something, such as a byte ...

  • brontobyte

    A brontobyte is a measure of memory or data storage that is equal to 10 to the 27th power of bytes.

SearchSolidStateStorage

  • SSD caching

    SSD caching, also known as flash caching, is the temporary storage of data on NAND flash memory chips in a solid-state drive so ...

  • NVDIMM (Non-Volatile Dual In-line Memory Module)

    An NVDIMM (non-volatile dual in-line memory module) is hybrid computer memory that retains data during a service outage.

  • NAND mirroring

    NAND mirroring has been proposed to break the security in certain portable devices that use NAND flash memory for encryption.

SearchCloudStorage

  • RESTful API

    A RESTful application program interface breaks down a transaction to create a series of small modules, each of which addresses an...

  • cloud storage infrastructure

    Cloud storage infrastructure is the hardware and software framework that supports the computing requirements of a private or ...

  • Zadara VPSA and ZIOS

    Zadara Storage provides block, file or object storage with varying levels of compute and capacity through its ZIOS and VPSA ...

Close