Theoretical Investigations Of Wave-absorbers And Filters Based On Metamaterials

Metamaterials are new artificial materials with some electromagnetic properties that natural medium do not own, by artificially embedding designed electromagnetic cell units in the natural medium. At present, left-handed materials (LHM) (the materials with negative permittivity and permeability),εsingle-negative materials (the materials with negative permittivity and positive permeability),μsingle-negative materials (the materials with positive permittivity and negative permeability), near-zero refractive index materials (the materials with the permittivity or permeability approach to zero), composite left/right handed transmission line, and so on. The left handed materials are those one that are studied earliest and also most among the metamaterials. Due to the fantastic electromagnetic properties of metamaterials, these materials have huge and promising applications in many fields. This paper mainly studied the theories of wave-absorbers and filters based on metamaterials, of which the innovative points as following:(1) The theoretical analysis on the electromagnetic performance of metamaterials was studied, giving the transmission formula of electromagnetic wave in the LHM single-layer medium, and RHM double-layer medium structures, and obtaining the mutual relationships among the wave impedance, electromagnetic parameters of metamaterials, and the electromagnetic frequency.(2) The basic idea to design absorbers using metamaterials was proposed, giving the design principles and methods of microwave absorbers based on many kinds of metamaterials, and the design examples.(3) The design theories and methods of transmission-type and reflection-type filters based on single-negative structures were studied following the basic theory of metamaterials, deducing the relationships between the filtering performance of transmission-type/reflection-type filters and the electromagnetic parameters, thickness of medium, the ratio of medium thickness, center frequency and filter bandwidth of the metamaterials. We completed the simulation of theoretical model for the transmission-type and reflection-type filters made from metalmaterials, and gave the interpretations of physical meanings for simulating results. The simulation results confirmed the relationships between electromagnetic parameters, thickness of medium, the ratio of medium thickness, the center frequency and filter band width.(4) The study shows that the designed filters own perfect filtering performance within some certain frequency bands, and the center frequency and band width can be adjusted by regulating the parameters of equal elements within some range, providing the reference for the engineering design.