Research And Design Of Bandpass Frequency Selective Rasorber

Radar antenna is a significant scatterer contributes most to an aircraft’s Radar Cross Section（RCS）.In order to improve the stealth performance,Frequency selective surfaces（FSS）have been widely used on Radar radome for RCS reduction,by reflecting the out-of-band incident wave to unimportant directions.Obviously,this method is effective only for monostatic RCS reduction because the reflective signals may also be detected by bistatic radar systems.So the stealth performance of Radar radome based on FSS reflection is greatly reduced.An ideal stealth radome should have the spatial filtering characteristic with a low insertion loss passband and an absorptive stopband.This kind of special electromagnetic absorber which is transparent to the electromagnetic waves at some frequencies is called as Frequency selective rasorber（FSR）.This paper studied the principle and design method of FSR.In addition,a miniaturized FSR and a FSR with an inserted passband are designed.The performance of two FSRs was verified by experimental tests.The main work of this paper is as follows:1.A miniaturized FSR is designed using miniaturized FSS design method.Firstly,lossy layer of FSR is designed with the theory of circuit analog absorbers,meandering square-loop structure is adopted for size reduction of lossy FSS unit.The miniaturized lossless FSS is based on nonresonant element,lumped capacities are introduced in the nonresonant element for further miniaturization.The miniaturized FSR is obtained after optimization of the cascade structure with lossy and lossless layer.The unit cell dimension of designed structure is miniaturized toλ₀/23.44,whereλ₀ represents the resonant wavelength of center frequency at passband.In addition,the miniaturized FSR has wide absorbing band from 3.3GHz to 8.9GHz.2.A FSR with an inserted passband is designed.The dual-stop-band FSS is used for lossless layer.And two separate absorbing bands are designed at the two stop-bands of lossless layer respectively.The FSR with an inserted passband is obtained after optimizing the structural parameters of lossy layer.The center frequency of passband is at 5.25GHz and the bandwidth for reflection less than-10dB is from 2.87 GHz to 7.9GHz.The passband of FSR is designed within a wide absorbing band.