Test standards with UFA procedures and guidelines:
Uniform Field Area (UFA) Setup for IEC 61000-4-3
The relationship between field strength within the UFA and forward power applied to the antenna is determined. During the test, the required forward power is calculated from this relationship and the target field strength. Chambers can adjust field strength levels provided that the linearity of the system can be demonstrated. The level setting is valid as long as the setup of the test instrumentation used remains unchanged for testing. Since even small displacements can significantly affect the field, it is important, especially at high frequencies, that the position of test instrumentation such as antennas, absorbers, cables, etc., is recorded. and fixed into place.
Overview of the Leveling Process
The lower edge of the UFA can be any height in most cases. It is the intention that the EUT is fully illuminated by the field. The setup of the EUT can help determine the height of the UFA's lower edge.
The distance between the transmitting antenna and the UFA shall be such that the UFA requirements can be met. A distance of 3 m between the antenna and the UFA is preferred. The minimum distance shall be 1 m. This distance is measured from the center of a biconical antenna, or from the front tip of a log periodic or combination antenna, or from the front edge of horn or double ridge wave guide antenna.
The distance used shall be recorded and shall be the same distance adopted for the test. The preferred dimension for the UFA is 1,5 m × 1,5 m, however,
HOW OFTEN DO YOU VERIFY THE UFA?
- Changes to the enclosure configuration (absorber replaced, area moved, equipment changed, etc.).
- or Annually
Small DUT and 5 Point UFA Level Setting
If the EUT can be fully illuminated with a smaller UFA, a smaller UFA is allowed down to 0.5 m × 0.5 m minimum. For the minimum UFA of 0.5 m x 0.5 m, a fifth grid point is placed in the centre of the UFA.