Meaning
Mathematical procedure used to calculate the radiation pattern of an antenna at a great distance using measurements taken close to the source. Accurate near field to far field transformation relies on the principle that the electromagnetic field on a closed surface can determine the field everywhere else.
Computational Algorithm
Sophisticated algorithms process the complex vector data during a near field to far field transformation to remove the reactive components that exist only in the immediate vicinity of the radiator. By applying the Huygens principle, the system reconstructs the radiating wave front as it would appear in the Fraunhofer region where the wave becomes locally planar. This process requires extremely precise positioning of the measurement probe to ensure that the phase relationships between different points are correctly preserved.
Measurement Benefit
Conducting a near field to far field transformation allows engineers to characterize large antenna arrays inside small indoor chambers rather than on expansive outdoor ranges. This approach provides a controlled environment that is free from weather interference or stray signals.
Validation Requirement
Accurate results from a near field to far field transformation depend on the precise sampling of the field at intervals determined by the Nyquist criterion. If the probe spacing is too wide, the high frequency components of the radiation pattern will be lost.
