What is IFF?
IFF (Indirect Far Field) is a 3GPP-approved over-the-air (OTA) test methodology that transforms near-field measurements into equivalent far-field results without requiring the physical far-field distance between the test antenna and the DUT. IFF encompasses techniques such as CATR (Compact Antenna Test Range) and NFTF (Near-Field to Far-Field Transform), which are essential for 5G NR FR2 (mmWave) device testing where the far-field distance would be impractically large for direct measurement.
How Does IFF Work?
IFF methods work by either creating synthetic far-field conditions (as in CATR, using a reflector to generate plane waves) or by measuring the electromagnetic field in the near region and mathematically transforming it to predict far-field performance (as in NFTF). In CATR, a parabolic reflector converts a feed antenna’s spherical wavefront into a planar wavefront within a quiet zone where the DUT is placed. In NFTF, probes sample the amplitude and phase of the DUT’s radiated field on a surface (planar, cylindrical, or spherical) in the near-field, and a Fourier transform computes the far-field pattern. Both methods are valid for 3GPP conformance testing.
Use Cases
5G NR FR2 (mmWave) OTA conformance testing, device certification for PTCRB and GCF, massive MIMO base station antenna characterisation, phased array antenna development and validation, and antenna pattern measurement for devices with integrated antennas.
3GPP / Standards Reference
3GPP TR 38.810 (Study on test methods for NR), 3GPP TS 38.141-2 (NR BS conformance testing — radiated), 3GPP TS 38.521-3 (NR UE conformance testing — radiated)
Related Terms
Learn More
This glossary entry is part of the 5GWorldPro Complete 5G Glossary. To go deeper into 5G architecture and technology, explore our 5G Training courses.
