Research On Scattering Characteristics Of Reflective Arrays Based On Terahertz Metamaterials

The metamaterial has important application value in the terahertz frequency band,and the metamaterial unit structure with different frequency response characteristics can effectively improve the performance of the core components such as the terahertz wave modulation device,the polarization conversion device,and the planar array antenna.This paper focuses on the scattering mechanism of the terahertz band in the cross and wire grid structure of Jerusalem,obtains the scattering and phase shift characteristics of the unit structure,realizes the control of the phase,polarization and propagation direction of the terahertz wave according to the scattering and phase shift changes.The main research content is as follows:The scattering and phase shift characteristics of the cross grid-type cell structure in Jerusalem were studied.The effects of dielectric constant?,dielectric thickness h,wire grid length Lx and Ly on the phase shift and scattering properties were studied.The results show that the increase of dielectric constant leads to the gradual decrease of the resonant frequency of the cell structure,the increase of the thickness of the dielectric layer,the decrease of the resonant frequency and the increase of the reflectivity.The effect of the length of the grid on the phase characteristics is studied.The results show that the maximum phase shift of the traditional Jerusalem cross type and the wire grid structure is close to 360 degrees,but the cross grid structure in Jerusalem not only has a good phase shift smoothness and linearity,but also has a greater bandwidth advantage,at the center frequency of 275GHz,its relative bandwidth is up to 54%.The phase shift dynamic control characteristics of a coded resonant ring structure are studied.The results show that the phases corresponding to the 00,01,10 and 11 states of the 315GHz frequency point are respectively 38~?-51~?-142~?and-226~?,that is,the phase difference between the adjacent states is close to 90 degree,and there is a bandwidth characteristic of 20GHz,which realizes the accurate regulation of the phase shift characteristics of the four coding states.Using the static cell structure designed in the previous chapters of this paper,a reflective array was designed according to a certain rule.The designed reflector array can form a beam with a reflection angle of 29 degree at a frequency of 340 GHz for the linearly incident plane wave.The deflection angle meets the theoretical design requirements,and can convert the linearly polarized plane wave into a circularly polarized plane wave.Its sidelobe gain is below-5dB,and its-3db beamwidth is 3degrees,which has good directivity.The advantage is that a bandwidth of 30 GHz is realized near the resonance point of 340GHz,and both the phase shift range and the smoothness of the phase curve can be well guaranteed.Using the cell structure designed in the previous chapters,a multi-beam reflective array was designed through a specific coding arrangement.When the electromagnetic wave is perpendicularly incident on the array plane,the reflective front is decomposed into four beams with an angle of 29 degree.