Analysis of an array of line sources above a finite ground plane

A simplified analysis which gives insight into and physical interpretation on the radiation mechanism of an array of line sources above a finite ground plane is presented. Computations have been restricted to an array of two line sources since data are available for comparison. Results on the variation of the maximum field intensity, the angle of maximum field intensity, and the field intensity at the axis of the counterpoise as functions of the size of the ground plane are presented. Variations of the maximum field intensity and the angle of maximum field intensity as functions of the distance of the source above the ground plane are also illustrated. These data become very important in the design of antennas for aircraft navigation taking into account the presence of the finite counterpoise which otherwise could lead to erroneous designs.     

The effect of an imperfectly conducting plane upon an incidentelectromagnetic field

Expressions are derived for the far field that results when electromagnetic radiation is incident upon an imperfectly conducting nonhomogeneous plane surface. In particular, these expressions include the second-order far field and thus allow consideration of surface wave effects. It is shown that the far field satisfies an integral equation and this is used to study the field resulting from a dipole that sits above a finite ground screen     

The radiation efficiency of a dipole antenna located above an imperfectly conducting ground

The dyadic Green's function technique is used to develop integral expressions for the radiation efficiency of three types of dipole antennas located above an imperfectly conducting, infinite ground plane. The three antennas treated are: 1) vertical Hertzian dipole, 2) horizontal Hertzian dipole, and 3) a vertical half-wave dipole with sinusoidal current distribution. The results of numerical evaluation of the integral expressions for several values of ground constants are presented in graphical form. The radiation efficiency of a vertical Hertzian dipole is found to exhibit a distinct peak when located at a height of one-eighth wavelength.     

The transient electromagnetic field of an electric line sourceabove a plane conducting earth

The pulsed electromagnetic radiation from an electric line source above a conducting earth is investigated theoretically. The modified Cagniard method is used to derive closed-form expressions for the electric and magnetic field anywhere above the conducting earth. Numerical results are presented for the electric field for different points of excitation and observation above the earth, as well as for different values of the earth's material parameters, i.e. permittivity and electrical conductivity. It is shown that the effect of the conductivity is of significant importance to the calculation of interfering transient electromagnetic fields in the presence of a conducting earth     

Calculation of radiation patterns of a Yagi antenna above imperfectly conducting ground

A computer program is presented for the calculation of radiation patterns of Yagi antennas, having up to ten elements, located above a plane imperfectly conducting ground.     

The inverse electromagnetic scattering problem for a perfectly conducting cylinder

The problem of determining the shape of the cross section of a simply connected perfectly conducting infinite cylinder from a knowledge of the far-field pattern for all angles of observation and small values of the wavenumber is considered. The method proposed relies heavily on conformal mapping techniques. In particular it is shown that if the transfinite diameter is known each Fourier coefficient of the far-field pattern of the electric field determines a Laurent coefficient of the conformal mapping taking the exterior of the unit disk onto the exterior of the unknown cross section. The transfinite diameter is determined by changing the polarization of the incoming wave and measuring the far-field pattern of the resulting magnetic field. Of particular interest is the case when only a finite number of the Fourier coefficients of the far-field pattern are known. In this situation error estimates are obtained by using results on coefficient estimates for univalent functions.     

Radiation and scattering from electrically small conducting bodies of arbitrary shape above an infinite ground plane

A simple moment solution is given for the low-frequency electromagnetic scattering or radiation problem involving a small perfectly conducting body of arbitrary shape placed close to an infinite ground plane. The method of images is used to account for the presence of the ground plane. The dynamic problem is approximated by two uncoupled problems, an electrostatic one and a magnetostatic one. Each static problem is then solved using the method of moments. The surface of the perfectly conducting scatterer is modeled by a set of planar triangular patches. Pulse expansion and point-matching testing are used in the electrostatic problem. For the magnetostatic problem, a set of solenoidal vector expansion functions is used. The induced dipole moments are computed from the induced electrostatic charge and the magnetostatic current densities. The scattered field is the field of these induced dipoles oscillating with the frequency of the incident field. Scatterers of various shapes are studied. Special attention is given to a conducting box on the ground plane.     

Electric field intensity at surface of a coronating wire above a ground plane

An assumption commonly used in the solution of the DC corona equations is that the electric field intensity at the coronating wire is always constant at the onset value. However, the validity of this assumption has been questioned in the literature. An algorithm in which this difficulty is alleviated is proposed.     

A uniform geometrical theory of diffraction for an imperfectly conducting half-plane

Diffraction tensors are presented in the context of the uniform geometrical theory of diffraction (UTD) for the high frequency scattering by an impedance half-plane at normal and oblique (skew) incidence. These are based on the exact Wiener-Hopf solution and were derived according to the UTD ansatz. In addition, unlike previous uniform diffraction coefficients, the ones given here reduce to the known UTD diffraction coefficients for the perfectly conducting case. The coefficients are explicit and therefore appropriate for practical applications. Several scattering patterns are also presented and compared to a previous heuristic solution.     

The problem of a conducting sphere resting on an earthed plane in a uniform perpendicular field and its applications

The total field in the neighbourhood of a conducting sphere resting on an earthed plane forming the boundary of a perpendicular uniform field is given. Its application to the problem of a contacting sphere on the centre line of the broad wall of a rectangular waveguide is discussed.     

精确分析任意导体地面上的套筒单极子天线

利用矩量法分析任意形状导体地面上的套筒单极子天线.对面结构选用三角形面元矢量基函数,对细线结构选用三角基函数,对线面结合处采用一种特殊的基函数,将导体地面和天线作为整体进行分析,大大提高了分析计算的精度.分别分析了两付位于圆形和方形地面上的实用套筒天线,其数值计算结果与实验结果或软件模拟结果吻合良好,表明了该方法的有效性.     

The transient electromagnetic field of a pulsed line source located above a dispersively reflecting surface

An exact representation for the transient field of a pulsed line source above a plane reflecting surface is obtained as a finite integral over the transient plane-wave solution for complex angles of incidence. When applied to the reflection from a conducting half-space, a solution for the transient field is obtained as a finite double integral, which permits accurate calculations in a minimum of computer time. Comparison with early-time and late-time approximations available in the literature shows that there is a wide range of times for which neither is accurate.     

Image theory for electromagnetic sources in chiral medium above thesoft and hard boundary

The classical image theory valid for electromagnetic (EM) sources in an isotropic medium above a planar perfect electric conductor (PEC) or perfect magnetic conductor (PMC) surface was extended to involve the planar soft-and-hard surface (SHS) boundary that can be realized with tuned corrugations. The image principle is now generalized to EM sources in isotropic chiral medium above an SHS boundary. The problem is solved by two consecutive decompositions of the sources reducing the problem to four classical ones involving electric and magnetic sources above PEC and PMC boundaries; each involving an isotropic nonchiral medium and possessing a known image solution. One of the decompositions is based on the fact that the two eigenwaves of a chiral medium do not couple at a soft-and-hard surface; and, the other one, on the eigenpolarizations of the reflection dyadic     

High-frequency analysis of an array of line sources on a truncatedground plane

A uniform high-frequency solution is presented for the field radiated at finite distance by a semi-infinite beam-scanning array of magnetic line sources located on a perfectly conducting half-plane. The field is represented in terms of Floquet waves plus their relevant singly and doubly diffracted rays, which arise from both the end of the array and the edge of the half-plane. This representation is uniformly valid also when transition conditions from propagating to evanescent Floquet waves occur. Furthermore, it provides a simple and attractive physical interpretation and is found numerically very effective, due to the fast convergence of the Floquet wave expansion for the field     

Distributed equivalent sources for the analysis of multiconductortransmission lines excited by an electromagnetic field

The interaction of multiconductor lines with electromagnetic radiation is commonly studied in terms of field-induced voltage and current sources distributed along the line. The author presents the relationships between these sources and the incident fields for the general case of a transmission line with its conductors embedded in different dielectric volumes of arbitrary shape. It is shown that the sources can be expressed directly in terms of the incident fields and some vector parameters which are determined from the solution of a series of electrostatic problems with appropriate boundary conditions independent of the incident electric fields. It is noted that the multiconductor lines are suitable for direct applications in microwave transmission lines with rather arbitrary configurations     

Analysis of an arbitrarily inclined slot on the ground plane of amicrostrip line

The analysis of an arbitrarily inclined slot on the ground plane of a microstrip line is presented using the spectral domain approach and reciprocity theorem. Comparison of numerical results for the special case of a perpendicular slot with other available computed and measured data shows a good agreement. It is found that the impedance level can be controlled over a wide range by varying inclination angle. Results should be useful in antenna and multilayer circuit integration applications     

Response of circular symmetric multiconductor microstrip line to an electromagnetic field

The primary-secondary field idea is used to determine the response of a circular symmetric multiconductor microstrip line (CSMSL) to an external electromagnetic plane wave. The primary field is obtained analytically for the cases of oblique TM/sup z/ and TE/sup z/ polarized incidence. The secondary field is determined using excited multiconductor transmission line theory. The method is examined to obtain the effect of external illumination on a four-strip CSMSL and some useful results are obtained.     

求解电磁场边界问题时逆规则的物理意义

本文在分析Laurent’s规则应用于光栅理论时产生慢收敛的原因的基础上 ,首次提出了用于解决这种慢收敛问题的逆规则的物理意义 ,并应用实例对逆规则的物理意义进行了详细的阐述 ,使大家对逆规则这一重要理论在物理上有了更深刻的理解