Design of Dual-Band Double Negative Metamaterials

A dual-band artificial magnetic material and then a dual-band double-negativemetamaterial structure based on symmetric spiral resonators are presented. an approximateanalytical model is used for the initial design of the proposed structures. theelectromagnetic parameters of the proposed metamaterial structure retrieved using anadvanced parameter retrieval method based on the causality principle show its dual-bandnature at microwave frequencies. the proposed double negative metamaterial structure withunit cells with transverse dimensions of 2.5 mm × 2.5 mm has two negative refractive indexregions around 6 ghz and 8 ghz. the designed structure can be scaled to other frequenciesand is also suitable for planar fabrication