| Metametarials(MM),as a kind of artificial electromagnetic(EM)composites with extraordinary physical phenomenon,how to control EM wave polarization by the electromagnetic coupling effect of structure units has been the highlight in recent years.Compared with conventional polarization converters,the geometrical dimension of MMs are much smaller.In this article,to overcome narrow bandwidth、 single polarization mechanism and low effciency of exsiting converters,we mainly study the transmission properties when EM waves penetrate through transmission-type MMs,furthermore,we explore new physical origins and propose wideband or high efficiency MM converters.The major works are as follow:1.Multi-layer design based on the spil ring resonator(SRR).(1)SRRs could perfectly control the EM waves in microwave domain as a kind of resonator,so we propose a multi-layer transmission-type MM with the combination of cut wires and SRR.The designed MM could convert EM waves in the frequency bandwidths of 14.5~18.2GHz with a high efficiency over 0.8,and the efficiency of resonant frequency is almost 1.0.(2)A three-layer MM design based on diagonal spil ring resonator(DSRR),and the asymmetric transmission(AT)property could be realized by the dislocation of the higher and lower DSRR.The efficiency of the converter is over 0.8 in the bandwidths of 8~11GHz and 17~21GHz,its has different transmission property when the EM wave with opposite incident direction.Moreover,the angle independent from 0o to 60o of this converter can be explained by the surface current distributions.The physical mechanism of the structure could be understandd by constituting two F-P like cavities,the F-P like cavity could enhance the transmission magnitude and the polarization of the transmission wave could be rotated by 90° when the EM wave penetrates through the two Fabry–Pérot-like resonant cavities.The measured cross-polarization transmissions are in good agreement with the simulated ones,validate the high efficiency and wideband polarization of the structure.(3)The design of complemantary structure of two-tiered DSRR based on Babinet principle.The structure could convert the polarization of EM waves in the frequency rigion of 8.5GHz~12.5GHz and 21.5GHz~24.5GHz by the duality of electricity and magnetism.The two-tiered structure could better gather electric field and lay a foundation of the design of SIW structures.2.The design of polarization converter MM based on SIW(1).Design of two-tiered SIW structure.As a microwave device,SIW has the advantage of controlling EM waves due to its cavity characteristics.At first,a y-x polarization converter is designed utilizing the empirical formulas of SIW,the electric field of EM waves could be converted by the coupling of high-mode electric field in the cavity,and the device has an efficiency over 0.9 in the resonat frequency.Secondly,a two-tiered polarization insensitive converter is proposed,it could concert arbitrary polarization of the incident EM wave into x-polarized wave transmitted by the ultilizing two perpendicular slot in the upper metal,and its has an efficiency over 0.8 in resonat frequency.(2).Based on the two-layered SIW structure,we add a complementary of cut wire during the upper and lower DSRR to expand the bandwidth of the device 200%,and the polarization conversion efficiency is over 0.9 in the resonat frequency.Futhermore,the AT property could be observed in the oppsite EM incident.The physical origin is still the coupling of high-mode electric field in the cavity,but the particular change process of electric field can be observed by x-/y-direction electric field distributions.Finally the measured results could validate the high-effciency and selective polarization conversion.(3)The design of complementary two-layered converter based on the combination of SIW and Babinet principle,its has a high efficiency in the frequency rigion of 6.3GHz~7.7GHz and 12.8GHz~14.9GHz and the mechanisn could be explained by the surface current distributions... |
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