| National defense technology has always been a top priority in China’s technological development,and the field of military stealth is a key research direction in contemporary national defense.In order for combat equipment and weapons to avoid detection by enemy radar,it is necessary to absorb the electromagnetic waves emitted by the radar.This prevents the receiving radar from detecting signals and generating alarms.Therefore,weapons and equipment need to cooperate with microwave absorbers to complete the absorption of electromagnetic waves.In recent years,honeycomb absorbers have gained popularity in the field of stealth.The reason is that the honeycomb structure has better load-bearing capacity compared to traditional coated stealth technology,and the application of aramid paper makes the honeycomb absorber have better physical and chemical properties,greatly reducing the weight of the absorber itself.In the existing research on honeycomb absorbers,most of them use paper frames immersed in liquid absorbers.However,their drawbacks include complex manufacturing processes,high costs,and easy detachment.Although research on composite paperbased materials is less prone to peeling off,the manufacturing process is refined to the fiber nano level,and the low-frequency absorption performance is limited.This article proposes a new design approach for honeycomb microwave absorbers in response to the above issues.The main job responsibilities are as follows:(1)Design and Analysis of Conical Electromagnetic Loss Absorbers.Extract the equivalent electromagnetic parameters of honeycomb microwave absorbers using homogenization theory.Combining the hierarchical recursive method with the cascade transmission matrix,the electromagnetic patch is designed to have a structure that gradually changes the direction of electromagnetic wave propagation in a continuous manner.The goal is to enable completion of impedance gradient while maintaining the strong load-bearing capacity of the honeycomb structure.Compared to electromagnetic patches,it significantly improves absorption bandwidth,with reflectivity between 3 GHz and 18 GHz below-10 d B.Physical processing tests were conducted on this design.(2)Design of Honeycomb Absorbers Loaded with Electromagnetic Patches.An electromagnetic patch with an impedance gradient has been added to the honeycomb structure made of carbon fiber aramid paper,which experiences electrical losses.Compared to honeycomb structures made with carbon fiber and aramid paper of the same size,this design exhibits superior low-frequency performance,a wider absorption band,and lower reflectivity.The starting point for its low-frequency reflectivity,which was previously below-10 d B in the C band,has been shifted to the P band.Additionally,its high-frequency absorption has increased.The antenna’s electrical size is 0.087 times the wavelength at low frequencies,and it has a working bandwidth of 184%.(3)Design of Broadband Microwave Absorber Based on Ring Circuit.Use screen printing technology to print circuit structures onto aramid paper.Based on the analysis approach of Jaumann absorbers,mixed graphite slurry is used to replace the resistance screen,and silver slurry is used to replace the metal screen.Qualitative analysis of printed resistance rings and metal rings summarizes the relationship between the impedance of resistance rings and metal rings,and the changes in honeycomb parameters.It also examines the relationship between the transmittance of metal rings and the changes in honeycomb parameters.The impedance matching of the designed structure was carried out using Smith’s circle diagram,and the absorption rate was higher than 80% in the4.78~16.60 GHz frequency band,with a working bandwidth of 110.6%.They conducted screenprinted circuits and handmade honeycomb processing for this design.They also tested the reflection and transmission coefficients using the free space testing method and analyzed the reasons for any errors. |
