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The far-field pattern of an antenna may be determined experimentally at an antenna range, or alternatively, the near-field pattern may be found using a near-field scanner, and the radiation pattern deduced from it by computation. [1] The far-field radiation pattern can also be calculated from the antenna shape by computer programs such as NEC.
The vertical plane is used to plot an antenna's relative field strength perpendicular to the ground (which directly affects a station's coverage area) on a polar graph. Normally, the maximum of 1.000 or 0 dB is at the side (unless there is beam tilt), which is labeled 0°, to 90° at the top and −90° at the bottom.
In contrast, directional antennas can have an almost unidirectional radiation pattern, so the correct end of the antenna must be pointed at the TV station. As an antenna design provides higher gain (compared to a dipole), the main lobe of the radiation pattern becomes narrower. Outdoor antennas provide up to a 15 dB gain in signal strength and ...
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
Omnidirectional radiation patterns are produced by the simplest practical antennas, monopole and dipole antennas, consisting of one or two straight rod conductors on a common axis. Antenna gain (G) is defined as antenna efficiency (e) multiplied by antenna directivity (D) which is expressed mathematically as: G = e D {\displaystyle G=eD} .
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 ...
For most antennas the boresight is the axis of symmetry of the antenna. For example, for axial-fed dish antennas, the antenna boresight is the axis of symmetry of the parabolic dish, and the antenna radiation pattern (the main lobe) is symmetrical about the boresight axis. Most antennas boresight axis is fixed by their shape and cannot be changed.