Design And Application Of Frequency Selective Surface Absorber

Frequency selective surface absorber,as a structure-type absorber,has a wider absorption bandwidth than coated absorbers,and can flexibly design different absorption bands by designing the structure and parameters of the frequency-selective surface.Therefore,the frequency-selective surface absorber is widely used in various scenarios of electromagnetic wave absorption.One of the main application scenarios includes the radar scattering cross section(RCS)control of the platform.The size of RCS indicates the target's intensity of radar wave scattering.In the battlefield,it has become an important indicator for measuring the anti-detection ability of weapons.Loading effective absorbing materials can greatly reduce the RCS of the target and improve the system's battlefield survivability.At the same time,in order to reduce the RCS of various large antenna systems loaded on military targets,it is necessary to design an absorber structure that does not affect the antenna radiation performance.In this paper,according to the project requirements,the RCS reduction in the X-band of antenna systems with center frequencies of 18 GHz and 7 GHz on military targets is achieved.After systematically introducing the basic theory of frequency selective surface absorbers,we have designed circular ring-shaped frequency selective surface absorbers that can be applied to the 18GHz antenna system's X-band RCS reduction,and a Rasorber structure that can be applied to 7GHz antenna system in X-band RCS reduction.It also focuses on solving the problem of angular stability,and proposes a multi-angle performance optimization method based on impedance conditions.The designed structure can achieve absorption in a wider band covering the X-band and has obvious advantages in angular stability.At the same time,the reference antennas in the corresponding frequency bands of the target antenna systems are designed,and the RCS reduction effect of the absorbers are simulated and analyzed.The specific results are as follows:First,a circular ring-shaped frequency selective surface absorber with lumped resistance was designed to achieve an absorption bandwidth of 4.7-15.5 GHz,with a percentage bandwidth of 108%.In terms of angular stability,when TE electromagnetic waves are incident,the incident angle increases up to 40°,it can still maintain an absorption rate greater than 90%in the 4.8-15.0GHz frequency band,and the bandwidth.When the TM electromagnetic wave is incident,it has almost no effect on the absorption rate at low frequencies,and the X-band Can still achieve more than 90%of the absorption rate.The steps of the absorber design and the range of values of the absorption layer resistance R and the absorption layer reactance X that meet the absorption conditions are summarized,and a new angle for parameter optimization is proposed.Secondly,band-pass frequency selective surface and a parallel lumped capacitor inductor are introduced to design a Rasorber structure with high angular stability.The insertion loss at the center band of the passband is only-0.15d B,meanwhile,S₁₁ is less than-10d B in the3.1GHz-15.2GHz frequency band,and the fractional bandwidth reaches 172.8%.In terms of angular stability,for different polarized incident waves,when the incident angle reaches 40°,it can still maintain an absorption rate of more than 80%in a large frequency range,and maintain a small insertion in a stable passband range.loss.Finally,a slot-coupled microstrip antenna with a center frequency of 17.8GHz was designed to replace the 18GHz target antenna system.The designed circular ring frequency selective surface absorber structure was applied to its RCS reduction.Achieved the RCS reduction of the antenna in the 4.7-16GHz.At the same time,a microstrip array antenna with a center frequency of 6.9GHz was designed to replace the 7GHz target antenna system.In the end,the Rasorber structure effectively reduced the RCS of the microstrip array antenna in the2.8-6.7GHz and 8.5-15.3GHz frequency bands.