In the actual work, we present the phenomenon of electromagnetically induced transparency (EIT) and Fano resonances by one-dimensional microwave coaxial waveguides for the aim to achieve a filtering system either by transmission or by reflection with very high performance. Our proposed system is composed of coupled asymmetric loops of lengths d2 and d3, and two asymmetric resonators of lengths d5 and d6. This system creates the resonance modes, which are sensitive to certain lengths, while they are insensitive to other lengths. The very narrow EIT resonance appears as a maximum transmission peak stuck between two transmissions zeros, this EIT is due to the interaction of the Eigen modes of symmetric resonators and the incident electromagnetic waves. On the other hand, a resonance near to a zero of transmission is called a Fano resonance, its appearance is due to the interaction between the Eigen modes of symmetric loops and the incoming electromagnetic waves. The theoretical results are obtained using the continuous medium interface response theory, which allows calculating the Green function of composite systems and the transmission rate T. This structure can be utilized for electromagnetic filtering by transmission or reflection with high transmittance and good quality factor. According to these results, this filtering system can be used in the field of microwave communication antennas.
We study in this work, the occurrence of defects modes in the transmission spectrum and the band structure of a perfect photonic asymmetric serial loops structure (ASLS) utilized for narrow-band filtering. The perfect structure presents large photonic bandgaps that result from the modes of the loops resonances and the system periodicity. Besides that, the existence of defects within this perfect ASLS, whether at the segment or loop level, or both of them, causes the appearance of two, three, or four defect modes within gaps with good transmission rates and high-quality factors. These defects modes are extremely sensitive to changes in structural parameters. This system can be used to filter or guide the incoming electromagnetic waves. The interface response theory has been used to accomplish the analytical calculation. Green's function of the full system is determinated using this method. It allows us to calculate the dispersion relation and the transmission rate. Therefore, this paper can provide ideas for the design of multi-channel tunable filter using for frequency division multiplexing and microwave and signal processing.
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