IEEE URSI AP-S

The Fraunhofer boundary r = 2D²/λ is the IEEE standard definition. Below this distance, wavefronts are not yet planar and far-field measurements become invalid. This is precisely why near-field measurement techniques exist.

Directivity and beamwidth are inversely correlated. A narrow beam means the radiated energy is concentrated into a smaller angular region, resulting in higher directivity.

At 1 mm, we are in the immediate reactive near-field region. The individual radiating elements are still spatially resolved. This is one of the key strengths of near-field measurements: you can literally "see" the antenna.

This rotational signature is characteristic of a spiral antenna. It is a classic example of an antenna "fingerprint" in the near field—and a textbook diagnostic case for Anyfields.

A Rat Race (hybrid ring) coupler provides two operating modes: a sum output (ports in phase) and a difference output (ports 180° out of phase). At 180°, the radiation from each antenna is out of phase in the boresight direction and therefore interferes destructively, so no field is observed. Far-field visualization immediately reveals which port is active without requiring a vector network analyzer.

Electronic beam steering, changing the relative phase between elements is the defining signature of a phased-array antenna. A reflector or a Yagi can only steer by physically rotating. Captured here in a single measurement campaign, each steering state was imaged in seconds.

As frequency increases, the horn's aperture becomes electrically larger: the field structure tightens, lobes multiply, and the energy concentrates. Distance or power changes would only rescale the image here, the spatial structure itself transforms, the unmistakable signature of a frequency sweep. One acquisition per frequency, no band limitation: that's broadband infrared imaging at work.

The absorbing film converts EM energy into heat, which the IR camera images. Below a certain field level, the thermal contrast vanishes into noise ; that's the real limit. Everything else (chamber, band restrictions) is precisely what this technology frees you from.

All four! Each element is imaged individually so anomalies are localized at a glance, the full map is captured in seconds, the technology is inherently broadband, and nothing touches or perturbs the field being measured.

Anyfields technology enables easy troubleshooting to identify defective radiating elements, as seen in the image below.

A known-good unit is measured once to create a gauge reference. Every subsequent unit is compared to it automatically: any deviation beyond tolerance triggers a fail, in seconds, directly on the line.

If it radiates, Anyfields can image it: antennas, absorbers, leaks, EMC hot spots on PCBs, even teaching demos. DC resistance is the one thing on this list with no field to see.