Study On Design Mechanism And Performance Of Flexible Periodic Absorbing Structures

With the development of electromagnetic radiation control technology,the demand for thin and efficient broadband absorbing materials has become increasingly stringent.At present,the absorbing material is still mostly a hard structural material.The dielectric substrate is mainly made of epoxy resin(FR4)and other materials.This type of material has high flatness,smooth surface,and stable mechanical properties,but its hardness is high and it does not have machinery.Flexibility,such as stretching,bending,folding,twisting,and other mechanical deformations,is only applicable to the surface of a regular shape object.The surface of most objects that require electromagnetic shielding is often irregular,requiring that the wave absorbing material can be changed according to the shape of the object,and therefore the requirement for mechanical flexibility is proposed.Flexible wave-absorbing materials can be flexibly loaded on objects with special shapes and meet the development trend of the next generation of wave-absorbing materials.In addition,the position of portable and wearable wave-absorbing equipment in electronic technology is also increasingly prominent.In this paper,microwave periodic absorption structure as the research object,the establishment of equivalent circuit model,through the deformation of the surface current and field distribution analysis,the deformation state of the periodic structure of the performance of the law and its causes,to solve the wave absorbing material in the deformation Under the state of unstable absorption performance,the following major results have been achieved:1.Mainly analyzes the regularity of the absorption performance of several conventional periodic absorbing structures(square,cross,square)under tensile state,and establishes a reasonable equivalent circuit model for different graphic structures;second,according to the proposed The equivalent circuit model,combined with the surface current and electromagnetic field distribution of the pattern layer before and after stretching,analyzes the causes of the change in absorption properties.In the case of stretching,since the structural dimension parameters change after the structure is stretched,the equivalent circuit parameters change accordingly,resulting in a change in the resonant frequency.Based on the principle of wave-absorbing structure design,a compensating mechanism is proposed,and a single-layer and two-layer compensating periodic structure are designed to achieve a stable absorbing performance of the structure under tension.2.Mainly compare the absorption performance of several conventional periodic structures(squares,crosses,open rings)under bending condition with that under normal incidence plane conditions,and analyze and summarize the structural bending behavior change rules and their causes of change.Under curved or oblique incident conditions,there is a path difference between the electromagnetic wave of the same phase surface and the surface of the structure,resulting in a difference in the field distribution of the pattern layer and the distribution of the vertical incident field,and the distribution is not uniform,resulting in secondary scattering.For these reasons,two kinds of periodic structures,square ring periodic structure and umbrella periodic structure were designed.The results show that both structures can effectively ensure the stability of the structure under bending or oblique incidence.3.To solve the problem that traditional conductive pastes and dielectric substrates do not have mechanical flexibility,a flexible printable conductive paste is prepared,and a flexible conductive paste is printed on a PDMS flexible substrate by a screen printing technique to obtain a mechanically prepared Flexible test sample,conductivity can reach 1300S/cm,elongation can reach 100% can still maintain continuous without breaking,and can maintain good conductivity.