Probes are the mechanism by which near-field spatial distributions of E-field, H-field and SAR can be mapped out around a DUT or other signal source.

With 3 orthogonal mini-antennas in their tip, probes have an impressive isotropic response largely independent of orientation. Diodes across each mini-antenna detect the RF fluctuations, and downconvert them to baseband, which can then be measured by a fast amp connected directly on top of the probe.

The primary distinction between types of probe is according to the medium in which the signal is measured:

• SAR probes are optimised to measurements in a dielectric medium which simulates the electrical performance of the brain or muscle
• HAC probes (“Hearing Aid Compatibility”), on the other hand, respond best to RF signals in air. HAC probes are further split into E and H types according to whether they detect electric or magnetic RF fields.