一种双阻带红外频率选择表面

为实现中、远红外大气窗口的双波段低红外透过率,设计了由2层不同尺寸圆环单元构成的双屏红外频率选择表面(FSS),仿真结果表明该FSS在3~5μm和8~12μm波段形成两个平均透过率低于5%的阻带.对FSS表面电流分析的结果说明,谐振单元表面感应出的对称分布电流使散射总场增强,形成增强型反射,而不同尺寸的谐振单元具有不同的谐振波长,两层谐振单元共同作用形成了两个阻带.研究了入射角以及介质层属性(厚度、介电常数和损耗角正切)对FSS传输特性的影响,结果表明FSS在两个大气窗口内具有良好的角度稳定性,介质层介电常数对FSS的传输特性有较大影响.     

Ka波段频率合成器

本文介绍了一种基于毫米波谐波混频、中频锁相的Ｋａ波段频率合成器的设计方案及实现结果。合成器的频率范围为２６．５￣４０ＧＨｚ,输出功率大于＋５ｄＢｍ,频率步进值为１ＭＨｚ,相噪指标为（１０ｋＨｚ）〈－６５ｄＢｃ／Ｈｚ,杂散低于－５５ｄＢｃ。     

双波段频率选择表面复合材料的性能研究

以三阶正十字分行贴片旋转45°得到的图形为基本周期单元,设计了一种新型周期图案的频率选择表面(FSS)。将FSS和聚甲基丙烯酰亚胺泡沫复合制备得到双波段频选复合材料,通过对频率选择表面尺寸和泡沫厚度的设计,研究了其在1～18 GHz内的电磁波插损。研究结果表明,当FSS厚为12 μm,边界宽为30 μm,两侧泡沫厚为5 mm时,双波段频率选择超材料在特定的频段内电磁波插损的实验值和仿真值基本一致,即在2.5~35 GHz及8.5~11 GHz频段内,90%频点插损值小于0.9 dB;随着电磁波入射角的偏移,带内插损值增大,有效带宽减小。     

一种新型红外频率选择表面

为实现在中、远红外两个大气窗口的低透过率,设计了一种基于六边形环状结构的双屏红外频率选择表面,利用CST 电磁软件进行仿真分析,发现该频率选择表面在3～5 mm 和8～15 mm 两个波段内的平均透过率低于0.025,实现了红外波段的双阻带;采用等效表面阻抗和表面电流法分析了该频率选择表面的滤波机理,发现不同极值点处由于屏间耦合或屏内单元间的耦合在谐振单元表面感应出对称分布的电流从而使散射总场增强,形成增强型反射,即比较理想的红外光阻带;最后研究了电磁波的入射角度、极化方式以及介质层的厚度对频率选择表面传输特性的影响.     

一种基于六边形环状结构的双阻带红外频率选择表面

为实现中红外大气窗口(3～5μm)和远红外大气窗口(8～14μm)的低红外透过率,设计了一种双频红外频率选择表面(FSS),该FSS由两个外侧六边形内侧圆形的环状结构组成.CST电磁软件仿真结果表明,该FSS在中远红外两个大气窗口内的平均透过率低于5％,实现了中远红外的双阻带.采用表面电流分析法分析了该FSS的滤波机理,该结构通过屏内单元间的耦合形成对称电流模式,使散射场增强,透过率降低,形成了相应波段的阻带.仿真结果表明该结构具有极化稳定性,且对于不同入射角的TE波具有良好的角度稳定性,介质层厚度和损耗角正切值对传输特性影响较小,介电常数对其影响较大.     

一种新型复合单元频率选择表面

提出了一种新型复合单元频率选择表面,用模式匹配方法得到了该周期表面未知电场的积分方程.给出了这种新型复合单元的电场基函数,用矩量法求解该积分方程,得到了不同入射角对这种新型复合单元FSS的频率响应特性曲线.计算结果表明,这种新型复合单元频率选择表面具有两个角稳定性很好的频带,这在通信系统和雷达系统中具有广泛的应用前景.     

A Frequency Selective Surface With Miniaturized Elements

We demonstrate a new class of bandpass frequency selective surface (FSS), the building block of which, unlike the traditional FSSs, makes use of resonant dipole and slot structures that have dimensions much smaller than the operating wavelength. This design allows localization of bandpass characteristics to within a small area on the surface which in turn facilitates flexible spatial filtering for an arbitrary wave phasefront. The proposed FSS is made up of periodic array of metallic patches separated by thin air-gaps backed by a wire mesh having the same periodicity (Ltlambda). The array of metallic patches constitute a capacitive surface and the wire mesh a coupled inductive surface, which together act as a resonant structure in the path of an incident plane wave. Like traditional FSSs, the capacitive and inductive surfaces of the proposed FSS can easily be fabricated using printed circuit technology on both sides of microwave substrates. It is shown that by cascading such bandpass surfaces in a proper fashion, any arbitrary multipole filter or non-commensurate multiband response can be obtained. The frequency response of the proposed miniaturized-element frequency selective surface (MEFSS) is demonstrated for various incident angles and it is shown that one-pole designs are less sensitive than two-pole designs to the angle of incidence. Dual band designs are also possible based on two-pole designs, but are more sensitive to incident angle than single band designs because of their larger (in terms of wavelengths) spacing. Prototypes of single-pole and dual-pole MEFSSs are fabricated and tested in a waveguide environment at X-band frequencies and excellent agreements between the measured and simulated results are demonstrated     

曲线三极子频率选择表面单元

设计了一种新型小型化宽带频率选择表面单元——曲线三极子单元,该单元外形轮廓为圆弧组成的曲线,相对于谐振波长尺寸小,可以三角形方式紧密排列,单元间距小,可调参数多,可设计性好,能够用于带阻型、带通型不同频段、不同带宽的频选表面。基于该单元给出了一个三屏频选的设计实例,实例表明,采用曲线三极子单元的频选表面带宽宽,角度稳定性好,透波率高,有效抑制栅瓣和二次谐振,改进了带外抑制性能。     

方环可调频率选择表面吸收体

讨论了带金属导电背板的可调频率选择表面(FSS)吸收体,这种FSS吸收体的阻抗层是无损耗的,集总器件被对称加载到FSS周期单元上.FSS周期单元的谐振频率在特定的频带内会随着集总器件电阻值的改变而发生平移,反射损耗低于-20dB的可调带宽可以覆盖6～12GHz,而且该吸收体的反射、传输特性基本不受入射波入射角度的影响.人射波经过FSS吸收体后基本被消除,而且吸收体的厚度要比传统FSS吸收体薄得多.     

A New Technique for Design of Low-Profile, Second-Order, Bandpass Frequency Selective Surfaces

In this study, a new method for designing low profile frequency selective surfaces (FSS) with second-order bandpass responses is presented. The FSSs designed using this technique utilize non-resonant subwavelength constituting unit cells with unit cell dimensions and periodicities in the order of $0.15lambda _{0}$. It is demonstrated that using the proposed technique, second-order FSSs with an overall thickness of $lambda _{0}/30$ can be designed. This is considerably smaller than the thickness of second-order FSSs designed using traditional techniques and could be particularly useful at lower frequencies with long wavelengths. To facilitate the design of this structure, an equivalent circuit based synthesis method is also presented in this paper. Two bandpass FSS prototypes operating at X-band are designed, fabricated, and tested. A free space measurement setup is used to thoroughly characterize the frequency responses of these prototypes for both the TE and TM polarizations and various angles of incidence. The frequency responses of these structures are shown to have a relatively low sensitivity to the angle of incidence. Principles of operation, detailed design and synthesis procedure, and measurement results of two fabricated prototypes are presented and discussed in this paper.      

用于Ka波段锁相环的宽带注入锁定分频器

基于0.13 μm CMOS工艺,提出了一种用于Ka波段锁相环频率综合器的宽带注入锁定分频器。分析了传统注入锁定分频器的结构、自谐振频率和锁定范围。采用2位可变电容阵列和差分信号互补谐振腔直接注入方法,实现了宽带的注入锁定分频。仿真结果表明,当注入信号幅度V_p为0.6 V时,该注入锁定分频器在24.1~35.6 GHz频率范围内的锁定范围为38.5%。与VCO联合仿真,结果表明,该分频器能准确实现二分频,适用于Ka波段锁相环。     

基于六边形环状结构的远红外频率选择表面

为实现远红外大气窗口(8～14 μm)的低红外透过率,基于六边形环状结构设计了双屏远红外频率选择表面(FSS).仿真结果表明,该结构在8～14 μm波段的平均透过率低于5％.对该结构的表面电流分析说明,谐振单元表面感应出的对称分布电流以及双屏结构之间的耦合效应使得散射场增强,透过率降低.研究了该结构在不同入射角和不同极化条件下的传输特性,结果表明该结构在8～14μm具有良好的角度稳定性和极化稳定性.分析了介质层介电常数、厚度以及损耗角正切对该FSS传输特性的影响,结果表明介质层介电常数对FSS的谐振频率和带宽有较大影响.     

A New Type of Combined Element Multiband Frequency Selective Surface

It is well known that a multiband frequency selective surface (FSS) can be obtained by arranging multiple simple apertures in a periodic array. However, this simple combination can not achieve a perfect resonance response in a wide band due to the restriction of the grating lobe frequency determined by the array. A new type of element, the multiperiodicity combined element (MPCE), is presented to solve this problem. Its feasibility on restraining the grating lobes is proven by numerical experiments and theoretical analysis. The electromagnetic performance of the MPCEs was studied. The results show that the MPCE FSSs have much weaker grating lobes than the traditional FSSs and their frequency performance can be well predicted through the properties of the member element FSSs. An approximate formula for predicting the transmission coefficients of the grating lobes is provided.      

A Fast Terahertz Spectrometer Based on Frequency Selective Surface Filters

We present a fast spectrometer working in the 0.7–4.8 THz range. Broadband radiation from a blackbody source is focused first on a rotating silicon wafer, whose surface was patterned with 18 metal band-pass filters, then on the sample under test and finally is detected by a superconducting microbolometer with microsecond time constant. The bolometer sensor is coupled to a spiral antenna whose frequency band matches the spectral range of the filters. The spectral resolution is set by the filters quality factor of about 3. A dynamic range of 100 and a S/N ratio of 20 are achieved by integrating for less than 10 second. The detector can operate up to 6 K in a closed-cycle cooler, hence making the present apparatus suitable for building up a simple terahertz video-rate spectrometer.     

Design of a Multiband Frequency Selective Surface

A frequency selective surface (FSS), whose unit cell consists of a ternary tree loop loaded with a modified tripole, is proposed to block multiple frequency bands. Target frequency bands correspond to Korean personal communication services, cellular mobile communication, and 2.4 GHz industrial, scientific, and medical bands. Through the adjustment of inter‐element and inter‐unit cell gaps, and adjustment of the length of elements, we present an FSS design method that makes the precise tuning of multiple resonance frequencies possible. Additionally, to verify the validity of our approach, simulation results obtained from a commercial software tool and experimental data are also presented.     

宽带多屏频率选择表面的设计研究

多屏频率选择表面传输曲线具有优秀的平顶和陡截止的带通滤波特性,特别适用于天线隐身的应用要求。文中首先设计了一种排列紧凑的通带六边形环单元,基于此单元,利用谱域法,分别进行了3屏和2屏频率选择表面的设计计算。采用激光刻蚀和中温固化工艺制备了试验件,并进行了传输系数测试,测试值与计算值基本符合,结果表明,所设计的3屏频率选择表面具有宽带宽角和陡截止的性能,传输性能优于双屏频率选择表面。     

紧凑的频率选择性表面阵列的谐振特性研究

该文对紧凑的频率选择性表面阵列的谐振特性进行了详细的研究。这类新型谐振单元尺寸大大缩小,结构紧凑,为低频段的频率选择性表面阵列的实现提供了可能。计算仿真与测量结果基本相符合。     

毫米波频段频率选择表面的分析计算

首先介绍了如何用辅助场量的FDTD方法分析计算毫米波波段的频率选择表面,然后给出了一种能快速计算多层FSS频率响应的方法——拟合电路法,并和FDTD计算的结果比较,结果吻合较好。     

采用粒子群算法的频率选择表面优化设计

 粒子群优化算法作为优秀的群体智能算法之一,已经被广泛应用于电磁优化问题中.通过与时域有限差分(FDTD)算法相结合,粒子群优化算法被运用于频率选择表面的优化设计.在此过程中,通过使用图形处理器(GPU)加速技术将FDTD算法速度提高近100倍,配合FDTD的宽频特性显著加速了优化过程.在此基础上,针对给定单元结构以及未知单元结构两种频率选择表面设计情况,分别采用带惯性权重的粒子群优化算法以及二进制离散粒子群优化算法进行优化.提出的两种优化流程在算例中得到验证与分析,证明了其可行性及高效性.     

Evaluation of Electromagnetic Compatibility of Onboard X- and Ka-Band Radars

A two-stage method for calculation of the input crosstalk of two airborne radars is considered. Electromagnetic compatibility of two closely located onboard X- and Ka-band radars is evaluated and a possibility of simultaneous work is assessed.