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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 near field refers to places nearby the antenna conductors, or inside any polarizable media surrounding it, where the generation and emission of electromagnetic waves can be interfered with while the field lines remain electrically attached to the antenna, hence absorption of radiation in the near field by adjacent conducting objects detectably affects the loading on the signal generator ...
The first technique developed was the far-field range, where the antenna under test (AUT) is placed in the far-field of a range antenna. Due to the size required to create a far-field range for large antennas, near-field techniques were developed, which allow the measurement of the field on a distance close to the antenna (typically 3 to 10 ...
English: Typical far field radiation pattern of an antenna. It consists of a surface whose distance from the origin at each point is proportional to the field strength radiated by the antenna in that direction. This is not the radiation pattern of any particular antenna but a generic pattern. SVG version of existing image. Source US Patent ...
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.
It radiates a far field signal strength of in its direction of maximum radiation along the z-axis. The green sphere is the radiation pattern of an ideal isotropic antenna that radiates the same maximum signal strength as the directive antenna does. The transmitter power that would have to be applied to the isotropic antenna to radiate this much ...
In a radio antennas, the main lobe or main beam is the region of the radiation pattern containing the highest power or exhibiting the greatest field strength.. The radiation pattern of most antennas shows a pattern of "lobes" at various directions, where the radiated signal strength reaches a local maximum, separated by "nulls", at which the radiation falls to zero.
Yagi–Uda antenna polar pattern showing pattern of alternating lobes and nulls. In radio electronics, a null is a direction in an antenna's radiation pattern where the antenna radiates almost no radio waves, so the far field signal strength is a local minimum. Nulls occur because different parts of an antenna radiate radio waves of different ...