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Small rhombic UHF television antenna from 1952. Its broad bandwidth allowed it to cover the 470 to 890 MHz UHF television band. A rhombic antenna is made of four sections of wire suspended parallel to the ground in a diamond or "rhombus" shape. Each of the four sides is the same length – about a quarter-wavelength to one wavelength per ...
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 ...
Antenna directivity is the ratio of maximum radiation intensity (power per unit surface) radiated by the antenna in the maximum direction divided by the intensity radiated by a hypothetical isotropic antenna radiating the same total power as that antenna. For example, a hypothetical antenna which had a radiated pattern of a hemisphere (1/2 ...
The rhombic is a travelling wave antenna, Each segment of the rhombus has a radiation pattern as shown (grey) having two lobes pointed forward at a certain angle. By making the corner angle equal to twice the tilt angle, the main lobes of each of the 4 sides point in the same direction and reinforce each other, increasing the gain.
Radiant intensity is used to characterize the emission of radiation by an antenna: [2], = (), where E e is the irradiance of the antenna;; r is the distance from the antenna.; Unlike power density, radiant intensity does not depend on distance: because radiant intensity is defined as the power through a solid angle, the decreasing power density over distance due to the inverse-square law is ...
When the antenna is fed at some other point, the formula requires a correction factor discussed below. In a receiving antenna the radiation resistance represents the source resistance of the antenna, and the portion of the received radio power consumed by the radiation resistance represents radio waves re-radiated (scattered) by the antenna. [8 ...
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.
The simplest way is mechanical beam tilt, where the antenna is physically mounted in such a manner as to lower the angle of the signal on one side. However, this also raises it on the other side, making it useful in only very limited situations. Horizontal and vertical radiation patterns, the latter with a pronounced downward beam tilt