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A short antenna pole next to a house Multiple Yagi TV aerials. Antennas are commonly placed on rooftops and sometimes in attics. Placing an antenna indoors significantly attenuates the level of the available signal. [19] [20] Directional antennas must be pointed at the transmitter they are receiving; in most cases great accuracy is not needed ...
In most antennas, the radiation from the different parts of the antenna interferes at some angles; the radiation pattern of the antenna can be considered an interference pattern. This results in minimum or zero radiation at certain angles where the radio waves from the different parts arrive out of phase , and local maxima of radiation at other ...
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.
In antenna engineering, sidelobes are the lobes (local maxima) of the far field radiation pattern of an antenna or other radiation source, that are not the main lobe.. The radiation pattern of most antennas shows a pattern of "lobes" at various angles, directions where the radiated signal strength reaches a maximum, separated by "nulls", angles at which the radiated signal strength falls to zero.
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.
The moving red lines show the wavefronts of the radio waves emitted by each element. The individual wavefronts are spherical, but they combine in front of the antenna to create a plane wave. The phase shifters delay the radio waves progressively going up the line so each antenna emits its wavefront later than the one below it.
The antenna feed system or antenna feed is the cable or conductor, and other associated equipment, which connects the transmitter or receiver with the antenna and makes the two devices compatible. [ 1 ] [ 2 ] In a radio transmitter, the transmitter generates an alternating current of radio frequency , and the feed system feeds the current to ...
Typical antenna parameters are gain, bandwidth, radiation pattern, beamwidth, polarization, impedance; These are imperative communicative means. The antenna pattern is the response of the antenna to a plane wave incident from a given direction or the relative power density of the wave transmitted by the antenna in a given direction. For a ...