有限长金属圆锥柱体侧天线三维辐射场的计算

本文以微分几何为工具,应用一致性几何绕射理论(UTD),导出了有限长金属圆锥柱侧天线三维辐射场的计算公式。这些公式同样适用于有限金属圆柱或圆锥。应用上述公式计算了锥柱侧横向缝隙及其排阵的任意平面方向图,并与实测结果进行了比较,两者吻合良好。     

金属截锥柱侧天线辐射场的研究

根据实测的单元天线方向图，利用几何绕射理论，给出了金属截锥柱侧天线三维辐射场的一种有效的数值分析方法。这些公式同样适用于金属截柱或截锥，应用上述公式计算了截锥侧微带天线及其排阵的任意平面方向图，并与实测结果进行了比较，两者吻合良好。     

金属截锥柱侧天线辐射场的研究

根据实测的单元天线方向图,利用几何绕射理论,给出了金属截锥柱侧天线三维辐射场的一种有效的数值分析方法。这些公式同样适用于金属截柱或截锥。应用上述公式计算了截锥侧微带天线及其排阵的任意平面方向图,并与实测结果进行了比较,两者吻合良好。     

微带天线RCS及其减缩

分析了影响微带天线RCS的公式，利用公式时微带天线的RCS减缩进行分析．计算了RCS减缩效果和在此情况下天线的辐射性能。结果表明，微带天线RCS与来波增益，天线本身增益和天线辐射效率有关。谐振点RCS的减缩通常伴随着天线增益和辐射效率的下降。     

金属基座对微带天线特性的影响

针对放置于柱形金属基座的普通圆极化微带天线,利用HFSS仿真分析了金属基座厚度对天线的驻波、增益、轴比等特性的影响,结果表明柱形基座的厚度变化不会对驻波产生显著影响,对增益会产生一定影响.但对轴比会产生比较显著的影响,通过选择合适的基座厚度可以在一定程度上改善天线的增益特性和轴比特性,同时进行了实验验证,该结果可以为实际设计微带天线提供参考依据.     

宽频带高增益微带天线元研究

本文提出了一种微带天线元的新结构,它具有宽频带和高增益特性。用谱域法推导了特征方程。用等效电路观点得到输入驻波比的频率特性公式、数值计算设计了一个C波段微带天线元。实测驻波比带宽达16％(VSWR1.5)或25％(VSWR2),增益在10.2～11.3 dB范围。这表明其带宽和增益都比普通微带天线元的带宽(5～6)％和增益(6～7)dB大得多。     

宽频带高增益微带天线元研究

本文提出了一种微带天线元的新结构，它具有宽频带和高增益特性。用谱域法推导了特征方程。用等效电路观点得到输入驻波比的频率特性公式，数值计算设计了一个Ｃ波段微带天线元。实测驻波比带宽达１６％或２５％，增益在１０．２－１１．３ｄＢ范围。这表明其带宽和增益都比普通微带天线元的带宽（５－６）％和增益（６－７）ｄＢ大得多。     

UHF圆极化微带天线

利用经验公式和软件仿真相结合的方法设计UHF波段的圆极化双层微带天线。对双层微带天线的圆极化特性进行分析研究,得到比较好的轴比、增益和方向图。     

一种基于SIW技术的喇叭天线

设计了一种新型微带天线。天线印制板为基片集成波导结构,天线前端用金属过孔形成喇叭状,从而构成一种微带H面波导喇叭,通过微带线--波导转换结构进行馈电,在辐射主方向具有较高的增益。该天线集合了传统微带天线低剖面以及H面波导喇叭的集束、高增益的特性,最后应用Ansoft HFSS进行了设计和仿真,验证了设计的正确性。     

新型宽波束圆极化天线--微带介质天线

通过在微带天线中引入介质天线原理，提出了一种以简单方式展宽微带天线波束和提高低仰角增益的新方法，从而发明了一种新型宽波束天线－微带介质天线。该天线具有极宽的波束、较高的低仰角增益和波束范围内有较好的圆极化性能等特点。文中给出了天线的原理、设计公式和实验结果。     

Compound Fresnel Zone Lens Conformal to Truncated Cone: Antenna Application

A millimeter wave antenna consisting of two Fresnel zone plate lenses, plane and conical, is examined numerically by use of the vector diffraction theory. The lenses are of Wood-Wiltse (double-dielectric) or Soret (half-open) type, and are designed for the frequency of 117 GHz. The lenses are made conformal to a truncated circular cone with a base diameter of 500 mm and a plateau diameter of 250 mm. Designs for two opening semi-angles, 45° and 75° each of them with a particular lens thickness are presented. For the angle of 90° the cone lens becomes a plane ring lens, which in combination with the plateau zone lens forms a plane lens of size equal to the cone base diameter. Illuminated by directive feeds set at a focal distance of 525 mm from the cone apex, the double-dielectric and half-open compound and plane lenses, form three pairs of Fresnel zone lens antennas, the co-polar and cross-polar radiation characteristics of which have been compared numerically. The double-dielectric lens antennas examined are about 5 dB superior in gain to the half-open lens antennas, which has a gain of approximately 45 dBi. Because all lenses are of equal transverse aperture, the corresponding lens antennas exhibit the same ?3 dB beamwidth of about 0.33 degrees. The plane zone lens antenna is very thin and simple. Instead, the antenna comprising a 3-D compound Fresnel zone lens is thicker but can be made conformal to a specific surface shape and possesses more levels of design and optimization freedom.     

加载介质透镜的超宽带平面螺旋天线设计

针对乳腺癌检测、成像等医疗领域对天线高增益及宽频带的需求,研究设计了一款加载介质透镜的超宽带平面螺旋天线。该天线采用双臂平面阿基米德螺旋天线作为辐射单元,在辐射臂外围间隔一定距离处加载金属圆环以改善驻波性能,并由指数渐变式微带巴伦作为馈电结构。天线顶部加载介质透镜,底部设置金属圆台形反射背板,实现了调整波束形状和提高天线增益的目的。加装圆柱形天线罩后天线高度约为87.53 mm,直径约为46.50 mm。仿真结果显示,天线在3－12 GHz 工作频带内回波损耗小于-10 dB,辐射方向图呈现良好的定向辐射特性,实测结果与仿真结果基本一致。     

Radiation from a monopole excited cone

This paper considers radiation from a finite, right circular, perfectly conducting cone which is excited by a quarter-wave monopole protruding from the center of its base. The cone is assumed to be of a size which places it above the resonance region, making a solution by the geometrical theory of diffraction possible. A formula which allows determination of the tip radiated ray from a semi-infinite cone excited by a uniform, in-phase, magnetic ring current is first derived. This is then used in conjunction with certain other known canonical solutions to obtain a complete solution for the proposed excitation. Radiation patterns, computed on a digital machine from the formulas derived, are compared with measured results and good agreement demonstrated.     

Time-domain radiation from large two-dimensional apertures via narrow-waisted Gaussian beams

This paper deals with the short-pulse radiation of three-dimensional (3-D) vector electromagnetic fields from arbitrarily polarized large two-dimensional (2-D) truncated aperture distributions, which are parameterized in terms of narrow-waisted ray-like pulsed Gaussian basis beams centered on a discretized Gabor lattice in a four-dimensional (4-D) configuration-spectrum phase space. The study extends our previous Gabor-based investigation of time-domain (TD) short-pulse radiation of 2-D fields from 1-D large truncated apertures with nonphased, linearly phased (delayed) and nonlinearly phased focusing aperture field profiles . We begin with, and summarize, a Gabor-based frequency domain (FD) formulation of the 2-D aperture problem which has been presented and tested elsewhere, but we include additional numerical examples for validation and quality assessment. As done by Galdi, Felsen and Castanon (see ibid., vol 49, p. 1322-32, Sept. 2001) we access the time domain by Fourier inversion from the FD, starting from the initial 3-D space-time Kirchhoff formulation (whose numerical integration furnishes reference solutions), and then passing on to Gabor-parameterized field representations in terms of pulsed beam (PB) wavepackets which are launched by linearly and nonlinearly phase-delayed focusing aperture distributions. Example calculations and comparisons with numerically generated reference data serve to calibrate the Gabor-PB algorithms and assess their domains of validity.     

地下三维目标电磁散射特性研究

本文推出集总电阻加载圆柱形天线在时域有限差分（FD-TD）法中的计算公式。对Mur二阶吸收边界条件在三维FD-TD法计算中的稳定性进行了研究，提出保证Mur二阶吸收边界条件稳定所必须注意的问题。在集总电阻加载圆柱形天线激励下，对色激媒质中三维目标的瞬态电磁散射特性进行了计算和分析，并将部分计算结果与实验测试的结果进行了比较，二者具有比较好的一致性。研究了色散媒质和目标特性对目标回波信号的影响，并对有耗媒质中细导线型目标的瞬态散射机理进行了分析。     

A Hybrid GMT-PO Method for Calculating the NDC of the Irregular Edge of a Semi-Infinite Cone

In this paper, the GMT-PO hybrid method accompanying with the iterative technique is applied successfully to calculate 3-D diffraction coefficients(3D-NDC) of the irregular cone edge. The computed RCS (backward NDC) of a finite cone with regular top is in good agreement with the measured data from the reference.     

Radiation from slot antennas on cones

Integral representations are given for the radiation field from slots on the surface of a semi-infinite conducting cone. The corresponding normal mode representations for delta function circumferential slots are evaluated numerically for various cone angles, slot positions, and azimuthal variations. Experimentally measured patterns for two finite models are reported and compared with the semi-infinite cone theory. In particular, effects due to finite cone length and finite tip radius are discussed.     

椭圆锥带线的严格解

本文研究椭圆锥带线的特性阻抗等基本参数.假定中心导体带是无限薄理想导体,传输的主模是TEM模,通过坐标变换和共形映射,椭圆锥带线变为平面周期性结构,然后用椭圆积分变换处理变换后的有限宽带线问题,得到了椭圆锥带线的严格解.     

Taylor series based two-dimensional digital differentiators

A new type of Taylor series based 2-D finite difference approximation is presented, and it is shown that the coefficients of these approximations are not unique. Explicit formulas are presented for one of the possible sets of coefficients for an arbitrary order, by extending the previously presented 1-D approximations. These coefficients are implemented as maximally linear 2-D FIR digital differentiators, and their formulas are modified to narrow the inaccuracy regions on the resultant frequency responses, close to the Nyquist frequencies