What is Direct Far-Field or DFF?

Direct Far-Field (DFF) refers to an antenna and over-the-air (OTA) measurement method in which the device under test is measured directly in the region where its electromagnetic radiation has fully formed into a plane wave. Every antenna produces a field that transitions from a reactive region near the radiator to a radiating near-field, and finally to the far-field, where the wavefront becomes essentially flat, and the antenna’s real radiation pattern emerges.

Direct Far-Field works by positioning the measurement antenna far enough away beyond the far-field boundary so that gain, directivity, beamwidth, TRP, and other radiation characteristics can be captured exactly as they appear in real-world operation. Because no mathematical transformations or synthetic field reconstructions are used, DFF is considered the an accurate method of measuring antenna performance. The measured results correspond directly to what the antenna radiates, making DFF the reference technique for validating patterns, evaluating polarization, and characterizing radiated power with high confidence. This is particularly important when antennas must meet strict regulatory or performance requirements, since the far-field represents the antenna’s true operational behaviour.

DFF is a reliable way to measure the performance of antennas at practical far-field distances. It can be used for IoT devices, GNSS antennas, mobile terminals, and many RF sensors. It also serves as the calibration reference for validating compact range and near-field systems used in 5G/6G testing.