Saturday, September 4, 2010

Omnidirectional Antenna

An omnidirectional antenna is an antenna  system which radiates power uniformly in one plane with a directive pattern shape in a perpendicular plane. This pattern is often described as "donut shaped". Omnidirectional antenna can be used to link multiple directional antenna in outdoor point-to-multipoint communication systems including cellular phone connections and TV broadcasts.

The only 3-dimensional omnidirectional antenna is the unity gain isotropic antenna, a theoretical construct derived from actual antenna radiation patterns and used as a reference for specifying antenna gain and radio system effective radiated power. Antenna gain (G) is defined as antenna efficiency (e) multiplied by antenna directivity (D) which is expressed mathematically as: G = eD. A useful relationship between omnidirectional radiation pattern directivity (D) in decibels and half-power beamwidth (HPBW) based on the assumption of a sinbθ / bθ pattern shape is

Practical antennas approach omnidirectionality by providing uniform radiation or response only in one reference plane, usually the horizontal one parallel to the Earth's surface.

Common low gain omnidirectional antennas are the whip antenna, a vertically oriented dipole antenna, the discone antenna, and the horizontal loop antenna (or halo antenna) (Sometimes known colloquially as a 'circular aerial' because of the shape).

Higher gain omnidirectional antennas are the Coaxial Colinear (COCO) antenna and Omnidirectional Microstrip Antenna (OMA).

Omnidirectional antennas are generally realized using colinear dipole arrays. These arrays consist of half-wavelength dipoles with a phase shifting method between each element that ensures the current in each dipole is in phase[4]. The Coaxial Colinear or COCO antenna uses transposed coaxial sections to produce in-phase half-wavelength radiatiors. A Franklin Array uses short U-shaped half-wavelength sections whose radiation cancels in the far-field to bring each half-wavelength dipole section into equal phase.

D-Link ANT24-0700 2.4 GHz Omni-Directional :

This antenna gives your router extended coverage and can go almost anywhere in your house.

D-Link introduces the Omni-Directional 7dBi Indoor Antenna (ANT24-0700) designed to provide extended coverage for an existing 802.11b/g wireless network. The omni-directional design of the ANT24-0700 offers dramatically increased wireless signal coverage in all directions. With 360° of better signal reception, this high-gain antenna will also improve data throughput at farther distances.The D-Link ANT24-0700 connects to a variety of wireless routers and access points on the market today. Whether the wireless router or access point has an SMA or TNC connector, the ANT24-0700 comes with an RP-SMA to RP-TNC conversion adapter to accommodate either connector type.
For maximum placement flexibility, the ANT24-0700 comes with a magnetic base unit* with 1.5m extension cable and a mounting kit. The magnetic base unit has an incredible strong hold onto any metal surface. Avoid the cost and complexity of adding additional access points or repeaters when you can easily use the ANT24-0700 to help improve wireless performance. Enjoy the benefits of wireless connectivity at greater distances throughout your home or small office.

The D-Link 2.4GHz Omni-Directional 7dBi Antenna (ANT24-0700) is a powerful antenna designed to help improve the performance of 802.11b/g networks, particularly if the adapter or router is in an area that is not ideal to send and receive radio signals.


  • Magnetic base with extension cable and mounting kit for flexible placement
  • Power 7dBi gain improves overall reach