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In this paper, two designs of bandstop filters are presented and implemented, each one composed of a coplanar waveguide loaded with a resonator. The first design has a structure with circular resonators, and the second design is a frequency reconfigurable filter with a rectangular spiral resonator and PIN diodes. The designs are based on the use of metamaterial to create notch filters for microwave applications. The Nicolson-Ross-Weir method, used to extract the refractive index, is also described to highlight the supernatural electromagnetic characteristic of metamaterials. From the simulation results, the filters exhibit high frequency selectivity via the presence of reflection zeros. In addition, for one or two rejection bands to isolate the WiFi band in a wireless communication system (depending on states of PIN diodes, small dimension, and low in-band insertion loss of better than 1 dB), the bandpass response could be dynamically tuned to different frequency bands and achieve good out-of-band suppression and linearity. The experimental results of the proposed structures are reported; the extracted data are also compared with simulation results, revealing good agreement.

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