| The effective regulation of electromagnetic wave propagation characteristics is of great significance in the field of civilian antielectromagnetic radiation interference and military radar stealth technology.As a new type of artificial material,metamaterials have different characteristics from conventional materials for microwave electromagnetic fields and are expected to be a technical mean for effective regulation of electromagnetic waves.In this thesis,the modulation on amplitude and polarization characteristic of microwave electromagnetic fields by metamaterial absorbers and polarization converters is studied through theoretical analysis,simulation design,and experimental verification.The main works are as follows:(1)A chaotic phase portrait-assigned metamaterial absorber was designed and fabricated achieving a broadband absorption effect on microwave electromagnetic fields.To excite multiple resonant modes,the contour envelope of chaotic attractor phase portraits are used as the surface resonator,and the model size parameters such as the pattern zooming ratio are used as the degrees of freedom for regulation,which can change the position and intensity of resonant modes;the adjustment of size parameters can regulate the proximity of multiple adjacent resonant modes to broaden the electromagnetic wave absorption bandwidth;through the simulation analysis of surface current,electric field and power density loss distribution,and the related absorbing mechanism are explained.(2)Applying the splitting degenerate modes of filters and antennas into the electromagnetic modulation design of metamaterials,two dualmode single-band and four-mode dual-band ultrathin polarization converters with high selectivity are designed and fabricated.A square patch pattern of etched orthogonal cross-slot is used as the surface resonator,and the splitting of degenerate modes is controlled by adjusting the length and width of the cross-slot;a pair of orthogonal degenerate modes in any narrow band corresponds to a second-order response,which enhances its frequency selectivity for electromagnetic waves in the operating frequency band;the effect of the cross-slot size on the splitting of the degenerate mode and the diffraction process of the resonator pattern from dual-mode single-band to four-mode dual-band design are investigated. |
