Impedance Matching Regulation And Research On Broadband Composite Absorbing Materials

Absorbing materials absorb electromagnetic radiation incident into their interior to reduce the energy of reflected waves.Absorbing materials have a wide range of applications in low observable technology,electromagnetic radiation control and electromagnetic pollution protection and so on.To meet the increasing demands of complex electromagnetic environments,attenuation characteristics and impedance matching characteristics of absorbing materials are improved by optimizing electromagnetic parameters and constructing structural design.Greater development is sought to obtain absorbing materials with higher performance.Structural design and integrated manufacturing become an effective means of obtaining absorbing materials with broadband,strong absorption and load-bearing properties,which has become a research hotspot in the field of absorbing materials.In this paper,structural absorbing unit was taken as the research object to improve absorbing and loadbearing properties of absorbing materials.Impedance characteristics were regulated and optimized to achieve broad bandwidth and strong absorption.Synergistic regulations were implemented including electrical loss and magnetic loss,optimization of electromagnetic parameters and the structural unit composition.Load-bearing properties and excellent absorbing properties were achieved through the integration design and synergistically regulation.The main research contents and results are as follows:(1)Impedance characteristics and reflectivity characteristics under imperfect matching conditions was analyzed in correlation.Numerical correlate relation between the absorption band,reflection loss intensity and the input impedance were established under the reflection threshold of-8 dB and-10 dB.If the reflection loss is under the reflection threshold,the input impedance is within the impedance characteristics region,which was used for the optimal design of structural absorbing materials.Correlate relation was verified by the electrical loss gradient structure,the magnetic loss gradient structure and the magnetic structure embedded with electric resonant ring.The construction of multilayer gradient structure broadens the absorption band of electrical loss material,and shifting the absorption peak to lower frequencies.By introducing a periodic planar structure into magnetic loss material,the absorption band in the low-frequency range can also be broadened.(2)Multilayer structural nano-resistive films with magnetic loss layer composite structure was constructed.Broadband absorption from L-band to Ku-band was achieved by synergistic regulation of electrical loss and magnetic loss.A circuit parametric model of isotropic and anisotropic structure was developed.A two-step optimization method was constructed including the reactance compensation design of multilayer nano-resistive films structure and layer matching design of magnetic loss layer.Broadband absorption problems at high and low frequencies are solved jointly.Double-layer isotropic nano-resistive film structure realized broadband absorption in high frequency.Compared with the double-layer Salisbury screen structure,the relative bandwidth of-10 dB was increased by 135.19%.Impedance and surface current analyses showed that double-layer anisotropic structure broaden the absorption band through reactance compensation design and multiple resonance modes.Relative bandwidth was increased by 48.48%.After the magnetic loss layer compounded with multilayer nanoresistive film structure,the absorbing performance was improved in the low frequency range of L and S bands.Regulated absorption in different frequency bands were obtained by nanoresistive film structure compounded with magnetic loss layer through electric and magnetic absorption mechanisms.(3)Impedance gradient absorbing structure was constructed based on the dual-factor modulation of the electromagnetic parameters optimization and the structural unit composition.Process preparation of gradient geometric configurations was achieved using additive manufacturing technology.Impedance characterization analysis was performed based on a layer-by-layer iterative model.Material gradient and structural gradient achieved continuously varying intrinsic wave impedance and matched input impedance in broadband frequency range.Multi-material absorbing structures with continuously varying structural parameters obtained broadband absorption performance from 2 to 18 GHz(S/C/X/Ku band).(4)Absorbing materials with integrated absorbing and load-bearing characteristics were obtained through structural design.The associated regulation mechanisms and enhancement mechanisms of bifunctionality were elaborated.The integration of absorption and load-bearing properties was achieved through nano-resistive film with honeycomb core composite structure and impedance gradient honeycomb core structure.Analytical relation between the intrinsic mechanical parameters,the structural parameters and the structural mechanical parameters of the honeycomb core were correlated according to the Y-shaped unit model.Stress distributions of the composite structure were analyzed by the finite element method to obtain the influence rules of compressive and flexural properties.The associative regulation mechanism of bifunctionality was obtained in decoupled and coupled situations.Decoupled regulation was achieved by multilayer nano-resistive films with honeycomb core composite structure.Absorption performance can be tuned by nano-resistive film structure.Load-bearing performance can be regulated by the double-layer honeycomb core structure.Coupled regulation was achieved by impedance gradient honeycomb core structure.Dual parameters had a common enhancement effect on absorption and load-bearing properties.