【作者】 高瑾；

【导师】 杨阳； 何小祥；

【作者基本信息】 南京航空航天大学 ， 电磁场与微波技术， 2019， 硕士

【摘要】 雷达隐身天线罩设计中广泛应用频率选择表面（Frequency Selective Surface,FSS）技术,但随着能够接收探测目标散射到其他方向的信号的雷达技术的发展,针对带内透波/带外吸波的吸透一体频率选择表面（Frequency Selective Rasorber,FSR）的深入研究已经迫在眉睫。本文针对FSR在目前实际应用中的迫切需求展开研究,主要工作分为以下三个部分:（1）首先给出了无源多频FSR的一种设计方法,随后本文基于该方法设计了一款双频透波/三频吸波的无源FSR,其上下层分别基于不同谐振单元。该FSR结构实现了在5.92GHz和9.30GHz处|S₂₁|分别为-0.94dB和-0.2dB的透波性能,|S₂₁|>-3dB的带宽为1.92GHz;在2.94GHz、7.84GHz和10.89GHz处分别实现了93.7%、88.4%和95.5%的吸收率,吸波率超过80%的频带带宽为1.98GHz。该双频透波/三频吸波FSR结构满足了多频FSR的应用需求。本FSR结构的透波频带与吸波频带之间存在过渡的反射频带,其|S₁₁|最高值达到了-3dB。（2）为了增强天线的带外隐身能力,降低因为过渡频带的高反射而被敌方雷达探测到的风险,本文设计了第二款双频透波/三频吸波的无源FSR,使得带内|S₁₁|<-10dB,该结构的上下层基于相同谐振单元。该结构实现了在7.86GHz和9.28GHz处|S₂₁|分别为-1.6dB和-0.98dB的透波性能,|S₂₁|>-3dB的频带带宽为3.97GHz;在4.18GHz、8.59GHz和10.82GHz处分别实现了84.7%、77.1%和88.8%的吸收率,吸波率超过75%的频带带宽为1.69GHz。此双频透波/三频吸波FSR的整个工作频段满足|S₁₁|<-10dB,大大改善了带外隐身能力。（3）最后,由于天线为强散射源,为了增强天线的带内隐身性能,本文在无源FSR的研究基础上结合有源FSS的设计方法,设计了一款透波窗口可控的有源FSR结构,其上层有源可控,下层为无源带通FSS。TE极化下,当PIN二极管断开时,在4.28GHz处的透波性能良好,插入损耗为-1.29dB,|S₂₁|>-3dB的频带为4.04-4.56GHz;透波频带两侧分布吸波频带,在2.39GHz和5GHz处分别实现了96.4%和82.0%的吸收率。当PIN二极管导通时,在4.28GHz处的透波窗口关闭,此时该频带内|S₂₁|最大值变为-7.39dB,|S₁₁|的最大值为-6.84dB,吸收率超过61.3%;两侧的吸波频带几乎未变。该有源FSR结合结构隐身技术,便可以在能够满足天线正常工作条件的前提下,当天线未工作时,整个雷达系统实现全频段隐身。总体上,本文首先设计了第一款双频透波/三频吸波FSR,在其基础上改进,设计了第二款双频透波/三频吸波FSR,实现工作频段内|S₁₁|<-10dB的设计目标,增强了天线的带外隐身性能。最后,设计透波窗口可调控的有源FSR来对天线的带内隐身能力进行改善。三款FSR结构的设计结果均圆满实现了预期的设计目的。更多还原

【Abstract】 Frequency Selective Surface（FSS）technology is widely used in radar stealth radome design.However,with the development of radar technology which is capable of receiving signals that are scattered to other directions by the detection target,it is imminent to research deeply on the Frequency Selective Rasorber（FSR）,which can transmit electromagnetic waves in passbands and absorb outside passbands.This paper focuses on the urgent needs of FSR in the current practical application.The main work is divided into the following three parts:（1）Firstly,an approach of designing passive multi-band FSR is described.With this method,a passive FSR with two passbands and three absorption bands is proposed,which has different resonant units on the upper and lower layers.The FSR structure achieves a transmission performance of-0.94dB and-0.2 dB at 5.92 GHz and 9.30 GHz,respectively.The bandwidth of|S₂₁|>-3dB is 1.92 GHz.The absorption rates of 93.7%,88.4%,and 95.5%are achieved at 2.94 GHz,7.84 GHz,and 10.89GHz,respectively.The bandwidth of the frequency range with absorption rates exceeding 80%is 1.98GHz.The FSR structure with two passbands and three absorption bands satisfies the application requirements of multi-band FSRs.There are transitional reflection bands between the transmission bands and the absorption bands of the FSR,and the highest value of|S₁₁|reaches-3dB.（2）In order to enhance the out-of-band stealth capability of the antenna and reduce the risk detected by enemy radar due to the high reflection of the transition band,this paper designs the second passive FSR with two passbands and three absorption bands,which makes|S₁₁|<-10dB in the whole work band.The upper and lower layers of the structure are based on the same resonant unit.The structure achieves a transmission performance of-1.6dB and-0.98dB at 7.26 GHz and 9.28 GHz,respectively.And the bandwidth of|S₂₁|>-3dB is 3.97 GHz;the absorption rates of 84.7%,77.1%and88.8%are respectively achieved at 4.18 GHz,8.59 GHz and 10.82 GHz,and the bandwidth of the frequency range with absorption rates exceeding 75%is 1.69GHz.The entire operating frequency band of the second FSR satisfies|S₁₁|<-10dB,which greatly improves the out-of-band stealth capability.（3）Finally,because the antenna is a strong scattering source,in order to enhance the in-band stealth performance of the antenna,this paper designs an active FSR with a controllable transparent window based on the research of passive FSR.The upper layer is actively controllable,while the lower layer is a passive bandpass FSS.Under TE polarization,when the PIN diode is turned off,the transmission performance at 4.28 GHz is good,whose insertion loss is-1.29 dB.The transmission band of|S₂₁|=-3 dB is 4.04-4.56 GHz.Two absorption bands are distributed on both sides of the transmission band.Absorption rates of 96.4%and 82.0%are achieved at 2.39 GHz and 5 GHz,respectively.When the PIN diode is turned on,the transmission window at 4.28 GHz is turned off,at which time the maximum value of|S₂₁|in this frequency band becomes-7.39 dB,the maximum value of|S₁₁|is-6.84 dB,and the absorption rates of the frequency band exceed 61.3%.The absorbing bands on both sides are almost unchanged.This active FSR combined with the structure stealth technology can realize the full-band stealth of the entire radar system when the antenna is not working,under the premise of satisfying the normal working condition of the antenna.In general,this paper designed the first FSR with two passbands and three absorption bands.After improving on it,the second FSR with two passbands and three absorption bands is designed.The second FSR achieves the design goal of|S₁₁|<-10dB in the whole work band,which enhances the out-of-band stealth performance of the antenna.Finally,an active FSR whose transmission window is adjustable is designed to improve the in-band stealth capability of the antenna.The design results of the three FSR structures have successfully achieved the expected design goals.更多还原