Analysis of Power Flow around Metasurface Sensor

Thin metasurface structures have been used as electromagnetic sensors to measure two-dimensional (2-d) radiofrequency (RF) field distributions incident on the surface. For example the electric field distribution was detected by the lumped resistors embedded in a mushroom-shaped metasurface absorber, which worked as a short-dipole array. The resistors interconnecting the square metal patches on the surface in the x - and y -directions absorbed the incident power of the Ex and Ey polarizations at the resonance frequency of the mushroom structure [1]. While the single-layer mushroom structure provided high absorption inherently at a single resonance, a broadband characteristic was achieved by using a stacked structure of two mushroom layers [2]. The voltages on the individual resistors were monitored by RF detectors to map the 2-d amplitude and phase profiles of the RF electric field vectors incident on the surface. The measured field distributions were used for in-situ and real-time monitoring and localization of RF noise sources. The accuracy and effectiveness of the measurement technique was evaluated and confirmed for spherical wave illumination based on a numerical analysis using the plane-wave spectrum (PWS) technique [3]. The electromagnetic field of the spherical wave incident on the absorber surface was expanded into a large number of plane waves, for each of which reflected and absorbed fields were calculated by treating the metasurface as an equivalent impedance surface using an effective medium model. The plane wave fields were then synthesized to obtain the spatial distributions of the reflected and absorbed fields on the absorber surface. The results of the numerical analysis were practically in good agreement with those of electromagnetic simulations and experiments.