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(Color online) (a) Schematic representation of metamaterial absorber. The incident wave is reflected back with no transmitted wave due to backside metal layer. The wave is absorbed at resonance frequency when electric field is parallel to the gap of the SRR as shown in the figure. Layout of the metamaterial array for (b) single band and (c) dual band absorbers. The dimension of the unit cell is square in shape and their periodical distribution forms 2D square lattice.
(Color online) Simulated results of the absorbers: (a) single band absorber at 77 GHz, showing power reflection, transmission, and estimated absorption coefficients for the electric field polarization parallel to the gap of (SRR). Also, the reflection coefficient for the perpendicular electric field polarization is presented, showing complete reflection of the wave energy. (b) Dual band absorber: power reflection coefficient of individual resonators (dotted lines) and response when imbedded (continuous lines). Power loss density of absorbers is shown in the inset; resonators are represented with false colors.
(Color online) Comparison of simulated (continuous lines) and modeled (dotted lines) power reflection coefficient: (a) single band absorber and (b) dual band absorber showing individual resonators and imbedded resonator response with mutual inductive coupling (M = 0.07).
(Color online) Schematic of the custom made backward wave oscillator spectrometer setup used for the reflection measurement.
(Color online) Measured (continuous lines) and simulated (dotted lines) power reflection and absorption coefficients of the single and dual band absorbers: (a) 77 GHz absorber with reflections for both parallel and perpendicular polarizations, (b) 95 GHz, and (c) 110 GHz absorbers. (d) Dual band absorber. Inset showing microphotograph of fabricated absorbers and image of absorber wrapped around cylindrical surface. These results show that absorption frequency can be tuned by changing dimensions of the metamaterial unit cell.
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