Design And Research Of A Novel Active Frequency Selective Surface Absorber

Although passive frequency selective surface(FSS)absorber can effectively widen the absorption bandwidth and reduce the thickness of the absorber,the fixed and immutable characteristics of the absorption frequency band and the absorption bandwidth limit the flexibility of its application.The Active Frequency Selective Surface(AFSS)absorber composed of active devices loaded on the metal FSS can realize the adjustable absorption intensity and frequency band,which makes up for the deficiency of passive absorber.In this paper,specific research is carried out on the application requirements of tunable absorption frequency band and reflection/absorption switchable absorber.The main contents are as follows:First of all,this paper studies the basic characteristics of the resonant absorber represented by the Salisbury screen,combined with the basic theory of two-dimensional metal frequency selective surface,discusses the design and analysis method of the passive circuit simulating wave absorbing structure,and discusses the methods used in this paper.The preparation process and test method are briefly introduced.Secondly,this paper introduces the equivalent impedance characteristics of PIN diodes and the commonly used feeding network design,and based on this,a broadband tunable absorber with PIN diode-loaded diagonal cross-ring unit and a PIN diode-loaded multi-frequency absorber are proposed.Branch square ring unit multi-frequency adjustable absorber.Under different resistance states of the diode,the adjustable absorbing body of the inclined cross ring unit can realize two absorbing frequency bands,various absorbing states can be adjusted,and the absorbing frequency band that can be covered under different resistance states is 3.5～14.8 GHz.The multi-branched square ring unit adjustable absorber uses a composite unit composed of a square ring and dipoles to increase the resonance length and resonance path.The absorber has five resonance peaks in the working frequency band,and the resonant peaks are shifted by adjusting the diode blocking state,so that the resonant peaks are distributed in the frequency band of 4～20 GHz.Finally,this paper proposes a switchable absorber/reflector of Minkowski ring unit.For the passive Minkowski ring unit broadband absorber,eight lumped resistors of the same size are loaded on the ring unit.When the lumped resistance is 100 Ω,the absorption rate of the absorber is more than 90% in the broadband frequency range of 3.95～17.1 GHz.when the lumped resistance is150 Ω,the absorption rate of the absorber in the broadband frequency range of5.8～15.95 GHz exceeds 96.8%.The polarization of the absorber is stable and the absorption stability of oblique incidence is maintained at an incident angle of less than 30°.Further,using PIN diodes to replace lumped resistors in passive absorbers,and the switchable absorber/reflector of the Minkowski ring unit is obtained,which can achieve 2.8～12 GHz absorption/reflection switchable.A continuous change in reflectivity from 0 to-10 d B can be achieved by controlling the diodes resistance.The test results are in good agreement with the simulation results.