飞机舵面缝隙缺陷建模及电磁散射特性分析

为了研究飞机舵面缝隙在飞机头向威胁角域的散射特性,提取舵面前端缝隙设计了雷达散射截面(Radar Cross Section,RCS)数值仿真分析模型.采用混合场积分方程和多层快速多极子算法进行了RCS仿真计算,并以RCS峰值、波峰宽度、均值增量三个评价指标分析散射特点.舵面前端缝隙的垂直极化散射明显(不同频率下的均值...     

Theoretical and experimental study of the input impedance of thecylindrical cavity-backed rectangular slot antennas

The authors study the input impedance of a cylindrical cavity-backed slot antenna based on mode matching and the complex Poynting theorem. Two cavity-backed slot antennas were fabricated to verify the theory. The numerical results agree very well with measurements. Two resonant frequencies were found from the input impedance. One resonant frequency is attributed to the rectangular slot and the other is due to the cavity. The slot length controls the first resonant frequency and has a much stronger effect on the input impedance at the antenna operating frequency as compared with the cavity length     

Study of Eigenmodes of Coaxial Resonators Using Coupled-Wave Theory

Based on the surface impedance theory (SIT) and the coupled-wave theory (CWT), this paper has established the second-order transmission line equation applicable to coaxial resonators with corrugated inner conductor. By utilizing the equation, the resonant frequency, Q factor and field profiles geometry of the eigenmodes of coaxial resonators can be calculated in view of the mode coupling, and the variables of the slot width and depth in the coupling coefficient can also be applied to calculate their impact on the resonant frequency and Q factor. The numerical results show that, the slot width and depth have significant impact on the resonant frequency, but their effect on Q factor is approximately negligible.     

A novel approach for miniaturization of slot antennas

With the virtual enforcement of the required boundary condition (BC) at the end of a slot antenna, the area occupied by the resonant antenna can be reduced. To achieve the required virtual BC, the two short circuits at the end of the resonant slot are replaced by some reactive BC, including inductive or capacitive loadings. The application of these loads is shown to reduce the size of the resonant slot antenna for a given resonant frequency without imposing any stringent condition on the impedance matching of the antenna. A procedure for designing this class of slot antennas for any arbitrary size is presented. The procedure is based on an equivalent circuit model for the antenna and its feed structure. The corresponding equivalent circuit parameters are extracted using a full-wave forward model in conjunction with a genetic algorithm optimizer. These parameters are employed to find a proper matching network so that a perfect match to a 50 /spl Omega/ line is obtained. For a prototype slot antenna with approximate dimensions of 0.05/spl lambda//sub 0//spl times/0.05/spl lambda//sub 0/ the impedance match is obtained, with a fairly high gain of -3dBi, for a very small ground plane (/spl ap/0.20/spl lambda//sub 0/). Since there are neither polarization nor mismatch losses, the antenna efficiency is limited only by the dielectric and ohmic losses.     

Cross polarization losses in periodic arrays of loaded slots

A periodic array of apertures in a conducting plane can act as a bandpass filter. With proper design the structure will be transparent at its resonant frequency but will have a transmission coefficient below unity at all other frequencies. These periodic surfaces are useful as radomes and in dual frequency antenna feeds. The resonant frequency of such an array may vary with incidence angle. This variation is undesirable for most applications, and can be greatly reduced by reactively loading the slots with the Babinet equivalent of a short circuited two-wire transmission line. It has been found, however, that singly loaded slot arrays have transmission loss due to cross polarized radiation when scanned in theH-plane (perpendicular polarization). It is shown that this cross polarized radiation may be eliminated by using symmetrical loaded slots, which have the further advantage of transmitting waves of arbitrary polarization. In conjunction with this investigation, the modal matching method, previously applied to arrays of rectangular and circular slots, has been extended to the more complicated loaded slot shapes. Both the single loaded and 4-legged symmetrically loaded slots are treated, and good agreement with measured data is obtained.     

一种基于缝隙天线阻抗的带缝腔体谐振频率计算方法

电磁波经缝隙进入机箱腔体后,会在某些频率点形成驻波而发生电磁谐振,导致腔体屏蔽效能急剧下降.为快速准确预测谐振频率以指导屏蔽腔体设计,本文基于缝隙天线阻抗理论提出一种带缝腔体谐振频率的计算方法.将电磁场用自由空间和腔体格林函数表示,根据缝隙处的边界条件建立等效磁流源的积分方程.通过矩量法求解积分方程,计算出腔体输入阻抗.根据谐振发生时电抗为零或电阻最小,可从频率-阻抗曲线获得谐振频率.本文方法不仅能预测缝隙谐振和低阶模式腔体谐振,还能预测出高阶谐振.与实验和CST仿真结果对比验证了本文方法的准确性及快速性.最后用本文方法分析了腔体和缝隙尺寸以及缝隙位置对谐振频率的影响.     

Studies of CPW-fed equilateral triangular-ring slot antennas and triangular-ring slot coupled patch antennas

Designs of coplanar waveguide (CPW)-fed equilateral triangular-ring slot antennas with tuning-stub and triangular-ring slot coupled patch antennas are proposed and experimentally investigated. The impedance matching of the resonant frequency can be obtained only by adjusting the tuning-stub length for the proposed triangular-ring slot antenna with tuning-stub. For the design of ring-slot coupled patch antenna, slightly changing the patch size causes the tunable frequency-ratio f/sub 2//f/sub 1/ between the first two operating frequencies to fall in the range of about 1.1-1.42. Details of the proposed designs are investigated by experimental as well as theoretical studies.     

Coplanar waveguide-fed circularly polarized microstrip antenna

Design of a square microstrip antenna for obtaining circular polarization (CP) radiation using a coplanar waveguide (CPW) feed is presented. This CP design is achieved by insetting a slit to the boundary of the square microstrip patch, which makes possible the splitting of the dominant resonant mode into two near-degenerate orthogonal modes for CP radiation and introducing an inclined slot in the CPW feed line for coupling the electromagnetic (EM) energy of the CPW to the square patch. Good impedance matching for CP operation can be obtained by adjusting the inclined slot length and the tuning-stub length of the CPW feed line. Typical experimental results are presented and discussed     

具有谐波抑制功能的宽带圆极化宽缝天线

针对微波无线输能系统中接收天线质量轻、体积小、剖面低、易与微波电路集成的特点,设计了一款新型的具有谐波抑制功能的宽带圆极化宽缝接收天线。通过在长方形缝隙中添加末端具有圆形贴片的交叉结构实现圆极化性能,添加切角结构展宽圆极化带宽。在馈线上添加具有一定长度的开路支节,配合使用缺陷地结构共同实现谐波抑制功能。研究并测试了天线的反射系数、轴比、增益以及远场辐射方向图,仿真与实测基本吻合。仿真结果显示,该天线很好地抑制了基频5.8 GHz的二次谐波和三次谐波,在4.5~6.2 GHz的范围内S11<-10 dB,相对阻抗带宽31.8%;基频5.8 GHz处的轴比AR=1.3 dB,在频率范围4.2~6.15 GHz内轴比AR<3 dB,相对轴比带宽37.7%;基频5.8 GHz仿真增益6.7 dB。     

小型化缝隙加载圆极化及宽带微带贴片天线设计

提出了一种十字形缝隙加载的小型宽带及圆极化微带贴片天线的设计方法。该天线通过在方形贴片上加载一个大尺寸的十字形缝隙实现天线的尺寸缩减,介质基片采用由FR4和空气层组成的层叠结构,在缝隙中嵌入L型枝节,只需通过调整枝节上同轴线馈电点的位置来获得圆极化或宽带阻抗匹配。ANSYS HFSS仿真分析表明,天线的圆极化带宽（AR≤3 dB）为1.7%,阻抗带宽（VSWR≤2）为5.8%,天线在宽带范围内具有稳定的增益,峰值增益为7.8 dB,同时贴片面积缩减了52.3%。改变馈电点的位置可调节两个谐振频率使天线阻抗带宽达到9.4%,比传统的微带贴片天线阻抗带宽提高了114%。     

基于快速群体智能算法的毫米波天线设计

针对毫米波天线阻抗不匹配的问题,该文提出基于粒子群蚁群(Particle Swarm Ant Colony Optimization, PSACO)的天线贴片参数优化算法,利用蚁群算法的信息素引导机制获得粒子群算法的最优贴片长、宽及馈电位置;并采用模糊决策综合评价模型(Fuzzy Decision-Making Comprehensive Evaluation, FD-MCE)求解毫米波天线的地面开槽位置,实现带宽扩展。对28.0 GHz中心频率进行设计与仿真,结果证明所提方法能有效且快速实现毫米波天线阻抗匹配,保证谐振频率与中心频率的一致,且在开槽面积不大于接地面总面积30%时带宽可扩展约33%,回波损耗特性也得到明显改善。所提算法具有计算复杂度低,收敛速度快的优点。     

The design of small slot arrays

The differences in mutual coupling for a central slot and a peripheral slot cannot be ignored in small arrays if good patterns and impedance are to be obtained. A theory has been developed whereby the length and offset of every slot in the array can be determined, in the presence of mutual coupling, for a specified aperture distribution and impedance match. The theory enlarges on Stevenson's method, and uses a modified form of Booker's relation based on Babinet's principle to treat nonresonant longitudinal shunt slots in the broad wall of a rectangular waveguide. A general relation between slot voltage and mode voltage is developed, and then formulas are derived for the active, self-, and mutual admittances among slots. These formulas result in a design procedure. Analogous treatments of inclined series slots in rectangular guide and of strip-line-fed slots are possible. Comparison between various experiments and the theory is presented. Tests of the theory include the resonant length of a zero offset slot, resonant conductance versus offset and resonant conductance versus frequency for a single slot, and self- and mutual admittances for two staggered slots. The design and performance of a two-by-four longitudinal shunt slot array is also described.     

Terahertz Wave Polarization Beam Splitter Using Asymmetrical Coupler

This study has proposed and numerically demonstrated a compact terahertz wave polarization beam splitter. The splitter is built by using a asymmetrical directional coupler consisting of a bend waveguide and a slot bend waveguides and achieves a high extinction ratio of 24.88 dB and 16.55 dB for cross and through ports. The optimal coupling region length is found to be 26 μm. By using such a polarization beam splitter, the size of the terahertz wave system could be reduced significantly. The simulation results show that the designed polarization beam splitter can split TEand TM-polarized terahertz wave into different propagation directions with high efficiency over the terahertz wave frequency range from 9.40 THz to 9.65 THz. The device obtained is readily used for a polarization diversity terahertz wave integrated circuit field, particularly for platforms with slot waveguide.     

Circularly Polarized Square Ring Slot Antenna with Arrow‐Shaped Structure

A novel design of a compact square‐ring slot microstrip antenna for achieving circular polarization (CP) operation is proposed and experimentally studied. By using an arrow‐shaped slot structure as a radiating element, the resonant frequency of the proposed antenna is significantly lowered, which can lead to a large size reduction for fixed frequency operation. The CP radiation characteristics are achieved by loading with proper asymmetry, which can be placed diagonally. A prototype of the proposed design is implemented and its performance is measured. Measured results show that radiation patterns with good CP characteristics are obtained at the resonant frequency.     

矩形波导宽边偏置交叉缝研究

提出了一种新的矩形波导缝隙阵列的单元形式－宽边偏置交叉缝，并采用全域正弦基Ｇａｌｅｒｋｉｎ法对其散射特性和谐振特性进行了理论分析。数值结果表明，这种缝隙单元的散射作用与宽边偏置纵缝相似，二者均可以用等效传输线上的一个并联导纳来表示，但交叉缝的谐振长度比纵缝显著缩短，因而交叉缝阵列中单元间的互耦相对较弱，频带相对较宽。理论计算结果与实验测量数据的良好吻合验证了上述分析方法的准确性。     

Design of an efficient miniaturized UHF planar antenna

The design aspects and the measured results of a novel miniaturized planar antenna are described. Such architectural antenna design is of great importance in mobile military communications where low visibility and high mobility are required. Slot radiating elements, having a planar geometry and capable of transmitting vertical polarization when placed nearly horizontal, are appropriate for the applications at hand. Slot antennas also have another useful property, so far as impedance matching is concerned. Basically, slot dipoles can easily be excited by a microstrip line and can be matched to arbitrary line impedances simply by moving the feed point along the slot. Antenna miniaturization can be achieved by using a high permittivity or permeability substrate and superstrate materials and/or using an appropriate antenna topology. We demonstrate miniaturization by designing an appropriate geometry for a resonant narrow slot antenna. A very efficient radiating element that occupies an area as small as 0.12/spl lambda//sub 0//spl times/0.12/spl lambda//sub 0/ is designed and tested. Simulation results, as well as the measured input impedance and radiation patterns of this antenna, are presented. This structure shows a measured gain of 0.5 dBi on FR4 substrate, which has a loss-tangent of the order of 0.01. Also, the effect of finite ground plane size on gain and resonant frequency is investigated experimentally.     

一种宽带双极化波导阵列天线的设计

设计了一种适用于雷达、通信等领域的宽带双极化波导阵列天线。天线的垂直极化信号通过波导阻抗变换直接馈电实现,水平极化信号通过由垂直极化信号馈电、缝隙耦合的方式实现。设计的阵列天线在12 GHz～15 GHz的频带内驻波比小于2,交叉极化低于25 dB,单元增益在带内大于8 dB,波束宽度大于60°。加工天线后实测结果与仿真结果吻合,该种阵列天线既适合固定波束阵列天线,又适合具有相扫功能的阵列天线。     

Investigation of wide-band microstrip slot antenna

This paper presents the simulation and experimental investigations of a printed microstrip slot antenna. It is a quarter wavelength monopole slot cut in the finite ground plane edge, and fed electromagnetically by a microstrip transmission line. It provides a wide impedance bandwidth adjustable by variation of its parameters, such as the relative permittivity and thickness of the substrate, width, and location of the slot in the ground plane, and feed and ground plane dimensions. The ground plane is small, 50 mm/spl times/80 mm, and is about the size of a typical PC wireless card. At the center frequency of 3.00 GHz, its width of 50 mm is about /spl lambda//2 and influences the slot impedance and bandwidth significantly. An impedance bandwidth (S/sub 11/=-10 dB) of up to about 60% is achieved by individually optimizing its parameters. The simulation results are confirmed experimentally. A dual complementary slot antenna configuration is also investigated for the polarization diversity.     

一种双频双圆极化共面波导馈电缝隙天线

一种新型加载两个开口环形接地导带的双频共面波导（CPW）馈电缝隙天线,被提出来实现双旋向圆极化辐射。从天线信号带伸入槽隙的水平矩形调谐短截线用于改善频带内的阻抗和轴比。对天线进行仿真和实物测量。实验结果表明,该天线的10 dB 回波损耗阻抗带宽分别是,在1.55 GHz 频段为27.69％（1.4~1.85 GHz）,在2.55 GHz频段为26.17％（2.075~2.7 GHz）。在1.55 GHz的频段和2.55 GHz频段所测量的3 dB轴比带宽分别是20.51％（1.4~1.72 GHz）和13.44％（2.36~2.7 GHz）。其辐射极化方向分别是低频段右旋圆极化和高频段左旋圆极化,天线在两频段内的峰值增益分别是3.69 dB和3.81 dB。实物测试结果与仿真结果基本吻合。     

A dual-polarized slot antenna for millimeter waves

We describe a new dual-polarized slot antenna to be used with quad-optical devices such as superconductor-insulator-superconductor (SIS) mixers at millimeter and submillimeter wavelengths. The radiation and impedance characteristics of the antenna were obtained from a moment-method calculation. The antenna has an excellent radiation pattern, a low impedance, wide bandwidth, and low cross polarization