Based On The Design And Electromagnetic Properties Of Absorbing Materials With Negative Refractive Index

Negative refractive index materials (NRIMs) are kinds of artificial composed materials which possess both the negative effective permittivity and permeability. Since the NRIMs have some novel EM properties such as the negative refraction, reversals of both Doppler shift and Cherenkov radiation, and enhancement of evanescent wave, much attention has been attracted on designing various structured NRIMs and investigating properties and applications. In this dissertation, based on the National Science Foundation of China"The composed method and characteristic research on tunable negative refractive index microwave materials", the fabricated method, EM properties, and the absorber applications of the NRIMs consisting of YIG and wires are analyzed step by step. The main research topics and innovative achievements gained are as following:1. The interactions between YIG and wires of the NRIMs are analyzed by using theoretical method, nurmical simulation, and physics experiment. The design and fabricated method of a revised NRIMs consisting of YIG slabs and PCBs are proposed. Such kind of NRIM sample is also fabricated. The test results show that NRIM have a pass band at 9 GHz with a 3-dB bandwidth of 0.5 GHz. And the pass band can be tuned by changing the applied magnetic field. While the applied magnetic field changed from 2300 Oe to 2700 Oe, the centre frequency of the pass band shift from 8.42 GHz to 9.50 GHz with a 2.8 MHz/Oe step. The test result of a prism like NRIM sample based on Snell's law also show that the NRIM have a negative refractive angle of -32°. These results confirm the validity of such composed method.2. The EM waves transmission properties in a special NRIMs which both the effective permittivity and permeability equal to–1 are analyzed by using both the theoretical and nurmical simulation methods. The tunneling effect in such NRIM and the microwave applications are also analyzed. The simulated results indicate that the NRIM filter have a pass band in 9.55 GHz-10.60 GHz with insert loss of 4 dB and out band attenuation of 30 dB. The NRIM linear shifter have a phase slope of about 80°/GHz and a maximum deviation of phase from linear of just±10°. These results indicate that the NRIM can be used in various microwave and millimeter wave area.3. A special three pass band metamaterial consisting of YIG and wires and a THz achievable tunable NRIM are analyzed by using both the theoretical and nurmical simulation methods. The design methods of the two media are presented and the EM waves transmission and refraction characteristics are demonstrated nurmically. The simulated results show that the three pass band metamaterial have three transmission peak at 7.1 GHz, 10.9 GHz, and 15.5 GHz, respectively. The refraction characteristics at the corresponding frequency indicate the positive-negative-positive properties of such metamaterial. And the THz NRIM has a negative pass band of 8 GHz at 0.145 THz.4. The absorber fabricated by NRIM is analyzed by using both the theoretical and nurmical simulation methods. The interaction between the incidence EM waves and the NRIM are presented. A tunable, broadband, high absorbed, microwave absorber consisting of YIG and wires are proposed. The optimal parametric values of the NRIM absorber are solved by using HFSS software. The simulated result show that the high absorptivity such absorber is more than 94.4%.