| Periodic absorbing structures efficiently dissipate electromagnetic(EM)energy that impinges on their surfaces.They find significant applications in radar stealth technology,wireless communication technology,EM shielding and protection technology,sensing technology,and various other fields.However,as the EM and application environments become increasingly complex,higher requirements have been placed on the absorption bandwidth,thickness,and stability of periodic absorbing structures.How to break through the limits of theoretical bandwidth and thickness,design lightweight and broadband periodic absorbing structures,and improve their adaptability in different environments has become a key issue that urgently needs to be solved in the design of periodic absorbing structures.Therefore,this dissertation focuses on investigating periodic absorbing structures.Through in-depth research on the influence mechanism and regulation mechanism of EM characteristics.By analysis of the interaction mechanism between magnetic materials and metal resonant structures,a magnetic multi-resonant periodic absorbing structure and a magnetic broadband periodic absorbing structure were designed and prepared.By analyzing factors such as device packaging,feeding methods,polarization methods,EM wave incidence angles,stacking methods,and the number of devices,the modulation mechanism of periodic absorbing structures was analyzed.Based on tunable structures,the absorption bandwidth of periodic absorbing structures was further expanded.By analyzing the influence mechanism of temperature on periodic absorbing structures,the temperature stability of magnetic and non-magnetic periodic absorbing structures was improved based on high-temperature resistant materials and compensation methods,respectively.The primary research work and innovations are outlined below:(1)A novel multi-resonant periodic absorbing structure has been designed based on a slotted structure and magnetic materials.The absorption peaks of this structure,with absorptivity greater than 90%,are situated in the L-,S-,C-,X-,and Ku-band,while displaying strong reflection in the frequency bands beyond these resonant peaks.On this basis,a novel broadband periodic absorbing structure design methodology was proposed by suppressing the strong reflection frequency band of multi-resonant structures.By employing square perforated magnetic materials and negative inductance circuits,the strong reflection of the multi-resonant structure in both 1.9～8.7 GHz and 0.5～1 GHz were effectively suppressed,leading to the successful design of a broadband periodic absorbing structure that covers the absorption frequency bands from P-band to Ku-band.The average absorption rate of this structure is 78.3%,with a thickness of only 7.4 mm.Compared with existing structures,the structure designed in this dissertation has significant advantages in terms of absorption bandwidth and thickness.(2)This dissertation investigated the active device’s influence on periodic absorbing structures’ performance,and employed the superposition principle to broaden their absorption bandwidth.By analyzing the effects of device packaging,feeding methods,and structural parameters on the control performance of a single polarization structure,a dual polarization design was successfully achieved from a single polarization structure.Furthermore,a broadband tunable periodic absorbing structure with S-,C-,and X-band was successfully designed based on the dual polarization structure and the superposition of PIN diodes.Furthermore,the absorption bandwidth of resistance film structures was significantly enhanced through the combination of variable capacitance diodes and resistance film structures.This resulted in an increased from 3.5～18 GHz to 2.53～18 GHz.(3)This dissertation investigated the angular stability of absorption efficiency in periodic absorbing structures,specifically addressing the challenge of compromised angle stability in tunable structures relying on capacitance control.A novel technique was introduced to enhance angle stability by incorporating slotting and loading resonances.Based on this method,a passive periodic absorbing structure with narrowband absorption in the range of 0° to 80° was designed,and the angle stability of the tunable periodic absorbing structure based on capacitance regulation was improved from 30° to 45°.(4)This dissertation investigated the effect of temperature on the absorption performance of periodic absorbing structures.By utilizing high-temperature resistant and heat-insulating materials,the temperature resistance of magnetic materials and magnetic multi-resonant periodic absorption structures were enhanced,allowing them to maintain consistent absorption within the temperature range of room temperature to 300 ℃.A method for designing temperature insensitive non-magnetic periodic absorption structures through compensation was proposed.Specifically,when significant variations in substrate′s EM parameters occur with temperature,the resistance film′s square resistance and active devices are employed to compensate for the shifts and changes in peak strength of the absorption.Conversely,when the substrate′s EM parameters remain relatively stable at elevated temperatures,enhancing the curing temperature of the conductive paste improves the temperature stability of the resistance film′s square resistance,thereby ensuring overall temperature stability for the periodic absorbing structure.In summary,this dissertation comprehensively investigates the absorption,tunable,and temperature resistance mechanism of periodic absorbing structures,and introduced strategies to broaden the operating frequency band and improve temperature stability.This dissertation successfully demonstrated the design of broadband,wide-angle,tunable,and temperature insensitive periodic absorbing structures,accompanied by experimental validation.These findings hold significant implications for the advancement and practical application of periodic absorbing structures. |
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