Omnidirectional Dipole Antennas

This subtopic describes the omnidirectional dipole antenna.

Omnidirectional Antenna: Dipole

Energy lobes "pushed in" from the top and bottom

Higher gain

• Smaller vertical beamwidth

• Larger horizontal lobe Typical dipole pattern

Higher gain

• Smaller vertical beamwidth

• Larger horizontal lobe Typical dipole pattern

Side View (Vertical Pattern)

Vertical Beamwidth New Pattern (with Gain)

Top View

(Horizontal Pattern)

2-dBi Dipole "Standard Rubber Duck"

Side View (Vertical Pattern)

Vertical Beamwidth New Pattern (with Gain)

Top View

(Horizontal Pattern)

2-dBi Dipole "Standard Rubber Duck"

When an omnidirectional antenna is designed to have gain, the result is a loss of coverage in certain areas.

Imagine the radiation pattern of an isotropic antenna as a balloon that extends from the antenna equally in all directions. Now imagine pressing in on the top and bottom of the balloon. This causes the balloon to expand in an outward direction, covering more area in the horizontal pattern, but reducing the coverage area above and below the antenna. This yields a higher gain because the antenna appears to extend to a larger coverage area. The higher the gain on an antenna, the smaller the horizontal and vertical beamwidth.

The 2-dBi Rubber Duck dipole antenna for 2.4-GHz frequency band is an example of an omnidirectional antenna. The figure shows the vertical radiation pattern.

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