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Also called a beam antenna [4] and parasitic array, the Yagi is widely used as a directional antenna on the HF, VHF and UHF bands. [ 3 ] [ 4 ] It has moderate to high gain of up to 20 dBi , [ 3 ] depending on the number of elements used, and a front-to-back ratio of up to 20 dB.
Yagi antenna for UHF TV reception with 22 parasitic elements; 4 reflectors attached to the vertical bracket at left, and 18 directors attached to the horizontal beam at right. The driven element is attached to the black box next to the reflectors. The antenna is most sensitive to radio waves coming from the right, parallel to the antenna's axis.
Patch antenna gain pattern. A directional antenna or beam antenna is an antenna which radiates or receives greater radio wave power in specific directions. Directional antennas can radiate radio waves in beams, when greater concentration of radiation in a certain direction is desired, or in receiving antennas receive radio waves from one specific direction only.
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A diffractive beam splitter can generate either a 1-dimensional beam array (1xN) or a 2-dimensional beam matrix (MxN), depending on the diffractive pattern on the element. The diffractive beam splitter is used with monochromatic light such as a laser beam, and is designed for a specific wavelength and angle of separation between output beams.
The first full scale beam waveguide antenna was the 64 meter antenna at the Usuda Deep Space Center, Japan, built in 1984 by the Japan Aerospace Exploration Agency. [6] After the Jet Propulsion Lab (JPL) tested this antenna and found it better than their conventional 64-meter antennas, [ 7 ] they too switched to this method of construction for ...
A quad antenna is a type of directional wire radio antenna used on the HF and VHF bands. A quad is a Yagi–Uda antenna ("Yagi") made from loop elements instead of dipoles: It consists of a driven element and one or more parasitic elements; however in a quad, each of the loop elements may be square, round
For directional antennas, the Yagi antenna is the most widely used as a high gain or "beam" antenna. For television reception, the Yagi is used, as well as the log-periodic antenna due to its wider bandwidth. Helical and turnstile antennas are used for satellite communication since they employ circular polarization.