【作者】 李顺礼；

【导师】 刘立国；

【作者基本信息】 山东大学 ， 无线电物理， 2010， 硕士

【摘要】 频率选择表面(Frequency Selective Surface, FSS)对电磁波具有频率选择和极化选择特性,能够有效的控制电磁波的传输和反射。频率选择表面对电磁波的频率和极化方式呈现出空间滤波器的功能,因而在科学和工程领域具有较大的理论意义和应用价值,越来越受到研究人员的重视,成为学者们的一个研究热点。频率选择表面的频率特性主要取决于谐振单元的结构形式和组阵方式。谐振单元的结构形式包括形状、尺寸、介质层的厚度和层数以及介质的介电常数等。组阵方式主要有矩形栅格和斜栅格两种。因此,FSS的设计属于多参数优化的问题。为了揭示各个参数对FSS特性(包括谐振频率、传输带宽等)的影响规律,旨在为设计FSS提供依据和规律,本文的主要工作有：1.FSS单元和介质层尺寸的研究。仿真并得到了十字形单元的孔径长度和谐振波长的关系以及单侧和双侧加载介质层对FSS频率特性影响的规律。金属屏谐振时,孔径的尺寸大约为λ0／2。当介质层厚度比较小时(<λ／4),两种加载方式都是随着加载介质层厚度的增加谐振频率逐渐降低。对于单侧加载,随着加载厚度的变化,该曲线围绕f／(?)上下波动并近似的呈现周期性,周期约为λ／2。对于双侧加载,随着加载厚度的变化,该曲线围绕f／(?)上下波动也近似的呈现周期性,周期也为λ／2。2.极化不敏感单元的设计。研究了偶极子形孔径单元对TE波和TM极化入射波频率特性的区别,提出了修正谐振孔径或振子尺寸设计极化不敏感FSS单元的方法,所设计的FSS对不同极化的入射波具有稳定的传输特性。针对传统Y形单元,给出了缩短TM波谐振孔径尺寸和两种延长TE波谐振孔径尺寸的设计方法,设计了三种对极化不敏感的Y形单元,对比了不同入射角度下三种改进方法相对传统设计方法的优点,仿真结果表明修正单元的TE波和TM波谐振频率差值的平均值比传统单元减小70%。3.针对不同入射角度具有稳定特性的FSS的设计方法。仿真了十字形单元和介质层在不同入射角度下谐振频率的变化曲线。由于随着入射角度的增大,介质层的谐振频率是升高的,为了设计对不同入射角度的入射波具有稳定传输特性的FSS,所设计FSS金属屏应当随着入射角度的增加谐振频率是降低的。设计FSS单元时要选择合适的形状和尺寸以满足上述规律,对于设计入射角稳定的FSS是很重要的,也是设计高性能的FSS滤波器需要注意的一点。4.设计了夹层结构的FSS,该夹层结构的FSS在大入射角度范围(0°-75°)下对任意极化入射波都具有良好传输特性,并且具有较大的工作带宽(1.4GHz)。提出了采用准互补单元设计FSS的设计方法并依此改进了夹层结构FSS中的传输异常现象。5.采用本文提出的延长TE波谐振孔径尺寸的Y形单元设计了双频带的FSS,对于不同极化的入射波具有相同的谐振频率和工作频带。在两个工作频带内,对于入射角0°-60°范围中,双频带FSS对任意极化的入射波都具有良好的传输效果。本文的主要创新点是：1.提出了修正谐振孔径或振子尺寸实现极化不敏感FSS单元的设计方法,可以设计对不同极化的入射波具有稳定传输特性的FSS。采用所提出的方法设计了三种对极化不敏感的Y形单元,仿真结果表明修正的Y形单元的TE波和TM波谐振频率差值的平均值比传统单元减小70%,证明该设计思路是可行的。2.提出了采用准互补单元设计多层FSS的设计思路,给出了采用该方法设计的准互补结构的频率选择表面。当入射角度在0°-60°范围内时,对于TE波和TM波,该设计在工作通带内都有良好的传输系数。3.设计了双频带的频率选择表面,该设计对于任意极化的入射波的工作带宽分别为1.5GHz和0.4GHz。当入射角度在0°-60°范围内时,对于TE和TM波,该设计在两个通带内都有良好的传输系数。4.指出了在设计对不同入射角的入射波具有稳定传输特性的FSS时,应当设计随着入射角度的增加谐振频率降低的FSS金属屏,这对于设计入射角稳定的FSS是很重要的。更多还原

【Abstract】 Frequency selective surface (FSS) which is featured by frequency selectivity and polarization selectivity of electromagnetic waves can effectively control the transmission and reflection of electromagnetic waves.Due to the spatial filter function to the electromagnetic wave of frequency selective surface and its great theoretical significance and application value in science and engineering, it has been the subject of intensive investigation and many researchers attach more importance to this hotspot.The element type and dimension, inter-element space and the substrate parameters generally determine the frequency response, such as resonance frequency, bandwidth, and its dependence on the incidence angle and polarization. The design of FSS is a problem of optimization of multi-parameters. In order to reveal the effect of the parameters to the FSS characteristics (including resonance frequency, transmission bandwidth, transmission loss, etc.)and to provide a basis for the design of FSS,the work of this dissertation are as follows:1.Research of the size of FSS unit and the dielectric layer. Simulations have been carried out to find the relationship between the length of cross unit aperture and the resonance wavelength and effect of the unilateral and bilateral loading dielectric layer to the frequency characteristics of the FSS.When the metal screen is resonant, the dimension of the aperture is aboutλ0/2.When the thickness of the dielectric layer is comparatively small(<λ/4),two loading methods will both decrease resonant frequency when increasing the thickness of the dielectric layer. For the unilateral side loading method, when the thickness of the dielectric layer change, the resonant frequency fluctuates around f/(?) and presents periodicity with period aboutλ/2.For the bilateral side loading method, when the thickness of the dielectric layer change, the resonant frequency fluctuates around f f/(?) and presents periodicity with period also aboutλ/2.2.Design of polarization insensitive unit.The different frequency characteristics of dipole-shaped aperture unit on the TE wave and TM polarized incident wave are studied. This dissertation proposed amendment methods to the design of polarization insensitive FSS element by changing the size of aperture or dipole, and the designed FSSs show stable transmission characteristics for different polarization incident wave. For the traditional Y-shaped unit, the methods of shorten TM wave resonance pore size and extend the size of TE wave resonator are given in this paper and three pairs of polarization-insensitive Y-shaped unit are designed.Comparisons are made between the three improvements and the traditional design methods at different incident angles and simulation results show that the average of difference of TE wave and TM wave resonant frequency of the modified unit decreases by 70% compared to the traditional units.3.Design method for FSS with stable characteristics at different incident angles. Simulations have been carried out of the cross unit and a dielectric layer at different incident angles and the resonance frequency curves are given in this paper. As with the incident angle increases, the dielectric layer resonant frequency is increased. In order to design FSS with stable characteristics at different incident angles, FSS metal screen should be designed with reduced resonant frequency when the incident angle increases. Suitable shape and size meeting the above rules for the FSS unit is very important in the design process, which is very important for the design of FSS with stable characteristics at different incident angles and high performance FSS filter.4. The design of sandwich structure FSS.The sandwich structure FSS has good transmission characteristics in a large incident angle range(0°-75°)for arbitrary polarization incident wave and has a large operating bandwidth(1.4GHz). Quasi-complementary FSSs are proposed to improve the transmission anomalies of the sandwich structure FSS.5.A dual band FSS is designed using the proposed extension of TE wave resonance pore size of Y-shaped unit. For different polarization of the incident wave, the dual band FSS has the same resonant frequency and frequency band. In two working bands, dual-band FSS has a good transmission for any polarization of the incident wave in the incidence angle range 0°-60°.The main innovations of this dissertation are as follows:1.Methods to the design of polarization insensitive FSS element by changing the size of aperture or dipole are proposed.These methods can be used to the design of polarization-insensitive FSS with stable transmission characteristics for different polarization incident wave. Using the proposed method, we designed three pairs of polarization-insensitive Y-shaped unit, and the simulation results show that the average of difference of TE wave and TM wave resonant frequency of the modified unit decreases by 70% compared to the traditional units, which shows that the design methods are feasible.2.A new method using quasi-complementary unit for the design of multilayer FSS is proposed. A FSS is given designed using quasi-complementary unit which shows good transmission characteristics in the incident angle range 0°-60°for both of the TE wave and TM wave.3.A dual band FSS is designed using the proposed extension of TE wave resonance pore size of Y-shaped unit. For different polarization of the incident wave, the dual band FSS has the same resonant frequency and frequency band of 1.5GHz and 0.4GHz respectively. In two working bands, dual-band FSS has a good transmission for both of the TE and TM incident wave in the incidence angle range 0°-60°.4. On the design of the FSS with stable characteristics at different incident angles, the paper pointed out that FSS metal screen should be designed with reduced resonant frequency when the incident angle increases, which is very important for the design of FSS with stable characteristics at different incident angles.更多还原