New plane wave spectrum formulations for the near-fields of circular and strip apertures

The plane wave spectrum (PWS) method has previously been applied to analyze the near-field of planar apertures. The main goal of this paper is to present new PWS formulations for the near-fields of strip and circular apertures. Only special cases are developed in detail. For example, the uniform and parabolic aperture distributions are developed for the circular aperture. These new formulations are expressed in terms of either elementary functions or Fresnel integrals. Consequently, they permit considerably more rapid and efficient calculations than previous near-field formulations, by either the PWS or the aperture integration approach. The new formulations are especially advantageous for large circularly symmetric apertures (on the order of100lambdaand larger) in that computational efficiencies are improved by an order of magnitude or two over the original PWS formulation. The improvement over aperture integration techniques is more than a factor of 1000 for the100lambdaaperture.     

Diffraction of a plane wave by a thick strip grating

The diffraction of a plane electromagnetic wave by a thick strip grating is solved rigorously by the Wiener-Hopf technique. The solution contains an infinite number of unknowns, which are shown to satisfy a certain infinite set of equations. By applying the modified residue calculus technique, this set of equations is solved and the approximate solution is derived. Representative numerical examples are given and the transmission characteristics of the grating are discussed     

Multiple penetration of a TEz-polarized plane wave intomultilayered cylindrical cavity-backed apertures

A generalized mathematical procedure is developed for investigating a TE_z-polarized plane wave penetration through two-dimensional (2-D) multilayered cylindrical cavity-backed apertures. The mathematical treatment is based on the direct integral equation technique combined with the Galerkin's procedure. Both the near- and far-zone field solutions to such a multiple coupling system are obtained in an analytical form. By taking the aperture edge effects into account, the magnetic currents on the surrounded multiple apertures are expanded in terms of a series of Chebyshev polynomials of the first kind. Furthermore, parametric studies are performed to show the variation of the penetrated near-zone magnetic field in various cylindrical cavity-backed apertures with the aperture number and geometrical sizes     

Electromagnetic plane wave scattering by large and finite strip array on dielectric slab

Plane wave scattering from a large but finite strip array on dielectric substrate is analysed in the frequency domain via a decomposition into plane wave spectra by using the method of moments and a closed analytical form of the spectral Green’s function for the structure under examination. Closed form asymptotic expressions are developed for mutual coupling terms which lead to a highly efficient and accurate procedure. New results for radar cross section in the ultra-wideband frequency range of the finite strip array are shown. Influence of the resistivity of the strips in the variation of the radar cross section is noted and discussed. Variations of the radar cross section with the scattering angle are presented as well.     

对称双圆孔傅里叶变换干涉条纹法测焦距

提出用照相缩微法制作一个小孔距对称双圆孔作为待测透镜傅里叶变换输入函数,利用其傅里叶变换频谱面上的干涉条纹间距的测量值计算透镜焦距。该法装置简单,调节方便,测量精度较高。分析了测量原理和测量误差,并给出了与理论分析相符的结果。     

On the aperture and pattern space factors for rectangular and circular apertures

A consequence of a recently discovered edge condition for planar apertures is that all planar aperture distributions are separable physically into a product of an edge factor and an aperture space factor, analogous to the way in which the radiation pattern separates into a product of an element factor and a pattern space factor. An exact relationship between these aperture and pattern space factors for physically realizable vector fields is derived here for rectangular and for circular apertures. For rectangular apertures it leads to a two-dimensional set of doubly orthogonal functions that are characteristic of the aperture geometry. Characteristic functions for circular apertures, however, are shown to exist only if the vector fields are circularly symmetric, although for scalar fields they exist for completely arbitrary aperture distributions with arbitrary edge taper. For rectangular apertures the characteristic functions consist of products of spheroidal functions and for circular apertures they are obtained from a generalization of the spheroidal functions. Some of the properties of these generalized spheroidal functions are developed here.     

Comments on "Surface wave enhanced broadband planar antenna for wireless applications"

For original paper see K.M.K.H. Leong et al., ibid., vol. 11, pp.62-4 (2001). The above paper claims to present "a new class of broadband antenna in which TE/sub 0/ surface-wave is used as the primary source of free space radiation". After reviewing the references, and analyzing the parameters published, it does not appear that the antenna can operate in the manner claimed.     

Scattering of a plane wave by a circular cylinder with uniformlyincreasing radius

The interest in the problems of diffraction by moving objects has become obvious due to the applications of nonstationary models for the simulation of different processes. Among them are radar control for the industry ejections or military explosions in the atmosphere and scattering by moving fronts of ionization, or by mobile artificial space objects. The detailed analysis of such processes implies the choice of an adequate model that on the one hand can be effectively investigated but on the other hand ensures a reliable approximation for the complex nonstationary processes. From this point of view, the set of canonical problems that can be solved accurately has great practical significance. We study the diffraction of an electromagnetic plane wave by a circular cylinder with a uniformly increasing radius. The formulation and analysis include propagating singularities as well as the continuous component of the solution. An accurate result is developed by means of separation of variables. Some numerical examples are discussed     

贝塞尔-高斯光束通过圆孔与圆环光阑的衍射

为了研究贝塞尔-高斯光束通过圆孔硬边光阑和圆环光阑的衍射特性,从Collins公式出发,采用数值模拟的方法模拟出光强分布.模拟结果表明,贝塞尔-高斯光束经圆孔光阑衍射后轴上光强随菲涅耳数F呈周期振荡;贝塞尔-高斯光束经圆环光阑后轴上光强随F呈振动衰减.在F相同时,贝塞尔-高斯光束经圆孔光阑衍射后横向光强分布比经圆环光阑衍射后横向光强分布平滑,孔径越小,光强调制越明显;当孔径与束腰相等时候,横向光强分布与菲涅耳数没有关系.     

An SEM analysis of the voltage induced upon a printed strip antennaby a transient plane wave

The singularity expansion method (SEM) is applied to study the interaction of a transient electromagnetic plane wave with a printed strip antenna. In SEM, the time-domain response of the element is separated into excitation-independent natural resonances and modes, which have considerable physical significance, and closed-form coupling terms which can be rapidly evaluated as the geometric or temporal properties of the source change. The SEM is demonstrated as applied to the transient microstrip problem, and the effect of varying the properties of the printed circuit substrate over a range of values typically found in microstrip antenna applications is studied. The transient response due to a step and Gaussian excitation is studied. It is found that the level of transient signal induced on a printed element increases with increasing substrate permittivity. The shape of the induced voltage or current waveform is highly dependent on the geometric and temporal properties of the source for elements printed on relatively thin substrates, while, for elements printed on thicker substrates, the shape of the induced waveform is much less sensitive to the form of the excitation, and resembles the oscillation of the fundamental resonance of the antenna     

Comments on time-to-frequency and frequency-to-time domain matrix formulations

This is a discussion of previous letters in the PROCEEDINGS and includes two possible extensions on the formulation of matrix coefficients.     

圆形螺旋相位板的平面波夫琅和费衍射特性

为了研究圆形螺旋相位板(SPP)对平面波的夫琅和 费衍射特性,基于标量衍射理论给出了圆形SPP对 有限孔径平面波进行夫琅和费衍射时所产生涡旋光束的光强表达式。理论模拟分析了圆 形SPP的拓 扑荷数n、半径R等参数对涡旋光束光强分布的影响,结果表明,当圆形SPP半 径R不变时,随着拓扑荷n的增大,涡旋光束半径逐渐增大,并且光强分布中旁 瓣的比重显著增强;当拓扑荷n不变时,圆形SPP的半径R增 大,产生的涡旋光束半径反而会变小,但涡旋光束的相对形状基本保持不变。基于纯相位空 间光调制器(SLM)实现了圆形SPP对有限孔径平面波的夫琅和费衍射, 并对理论结果进行了实验验证,实验结果与理论分析一致。