FarFieldTests

FarFieldTests is a collection of procedures used to characterize the radiative properties of a source when observed in its far field. It is widely applied to RF antennas as well as acoustic radiators such as loudspeakers and transducers.

In the far-field region, the field’s angular distribution is essentially independent of distance, and the wavefront is approximated as planar. A common rule of thumb places the onset of far field at R > 2D^2/λ, where D is the largest dimension of the radiator and λ is the wavelength.

Measurements typically aim to determine the radiation pattern, gain and directivity, polarization, impedance or reflection coefficient, phase center, and, in acoustics, the on- and off-axis acoustic power response. The resulting data support design, verification, and comparison across devices.

Tests are conducted in controlled environments such as shielded anechoic chambers, outdoor ranges, or compact-range facilities. Equipment includes calibrated reference antennas or microphones, a rotation mechanism or positioning system, measurement instruments (vector network analyzers, spectrum analyzers, or microphones and preamps), and data-processing software.

Typical procedures involve mounting the device, sampling emissions over a spherical or hemispherical set of angles, calibrating against a reference, and computing polar or volumetric radiation plots along with numerical metrics such as peak gain, directivity, and efficiency.

Limitations include reflections and multipath, environmental noise, and calibration errors. Results are normally expressed with associated uncertainties and are often standardized for comparison.