Radio-frequency field measurement using thin artificial magnetic conductor absorber

The thin radio-frequency (RF) absorber constructed with an artificial magnetic conductor (AMC) surface is used as a sensor array to measure incident 2-d RF field (amplitude and phase) distributions. The AMC surface employs a 2-d dense array of mushroom-type square metal patches on a dielectric substrate. Incident waves are absorbed by the lumped resistors interconnecting the metal patches on the surface, when they are matched with the incident wave impedance at the resonance frequency of the mushroom structure. A 2-d distribution of the amplitude and phase of the incident RF field is obtained by directly measuring those of the voltages induced on the individual resistors. The validity of this new technique of RF field measurement is evaluated using electromagnetic simulation. It is confirmed that the voltage induced on the resistor can be used to monitor the incident (absorbed) RF electric field. For a finite-sized absorber the measurement accuracy is degraded near the outer edge due to edge reflections. This technique is expected to be useful for capturing the snapshots of RF field distributions in situ, while the electromagnetic environment is almost undisturbed by the AMC absorber.