摘要:

The paper presents the general theory of an entire-domain Galerkin method for the analysis of metallic (i.e. perfectly conducting) antennas and scatterers. The antenna and scatterer surfaces are approximated by generalised quadrangles (i.e. curved curvilinear quadrangles defined by means of parametric equations, whose edges coincide with local coordinate lines). Surface currents are expanded in such local coordinate systems and the general form of the corresponding electric field integral equation is derived. A procedure is decribed for obtaining entire-domain basis functions which satisfy automatically the continuity equation along the surface element interconnections and free edges, and the expressions are derived for the impedance matrix elements in this case. Starting from the general theory, two new particular methods are presented. The first is intended for the analysis of general structures, and is based on application of truncated cones and bilinear surfaces for the approximation of geometry. The second is aimed for the analysis of spherical scatterer, and is based on the application of generalised rectangular elements which follow the sphere shape. Both methods use polynomials for approximation of currents. Very good agreement of the results obtained by the proposed method with available experimental and numerical results is achieved by using small number of unknowns per wavelength squared (about ten for large surfaces of simple form).

DOI:10.1049/ip-h-2.1993.0001

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The analysis of unilateral finlines has been completed using a new method, regular solution of singular integral equation (RSSIE). It is demonstrated that the results obtained by this method are more accurate than those computed by the spectral domain method (SDM) by comparing the data measured. In some special cases where the results can be obtained exactly, the new method gives more accurate values than those calculated by the SDM. Dominant and higher-order modes can be calculated effectively and accurately. The computer time required by this method is decreased considerably compared with SDM (about 1/45 of the time required by SDM).

DOI:10.1049/ip-h-2.1993.0002

出版商:IEE    

年代:1993

数据来源: IET

摘要:

A parametric study of the co- and crosspolarisation characteristics of tapered planar and antipodal slotline antennas having different tapers has been undertaken with the aim of using them as elements of wideband phased arrays on a stand-alone basis or in conjunction with the reflectors/lenses of imaging systems. The planar tapered slotline antennas have better crosspolarisation characteristics than their antipodal counterparts which have better input impedance characteristics. The study reported here was conducted in the 3–12 GHz band and yielded a wealth of information which will complement the theoretical studies which are in progress.

DOI:10.1049/ip-h-2.1993.0003

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The conventional finite difference time domain (FDTD) algorithm for solving electromagnetic scattering problems, which uses a uniform Cartesian grid for enmeshing the problem domain, is limited in its ability to model scatterers of arbitrary shapes. In this paper, we extend the FDTD algorithm to a general obliquely Cartesian coordinate system, and apply it in conjunction with an edge-type absorbing boundary condition (ABC) to solve a number of representative TM scattering problems. In addition to extending the FDTD algorithm to obliquely Cartesian grids, we also derive the stability condition for the twodimensional obliquely Cartesian FDTD algorithm.

DOI:10.1049/ip-h-2.1993.0004

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The electrostatic field distribution inside a split conductor cylinder filled with a dielectric tube is studied. The solution procedure is based on imposing more matching equations than the number of unknown coefficients, so that an overdetermined system of equations is obtained. The edge singularity of the field is rigorously taken into account. The described configuration represents a canonical problem related to the measurement of dielectric materials within a TM010microwave cavity.

DOI:10.1049/ip-h-2.1993.0005

出版商:IEE    

年代:1993

数据来源: IET

摘要:

A perturbation/iterative method (the PPP method) is proposed for the analysis of electromagnetic fields in inhomogeneous media. It consists of increasing the values of the parameters the medium at all points in small increments, starting from their vacuum values, and computing the induced sources by means of the total field (the incident field, plus that of the induced sources as obtained in the preceding step). Thus, in all the perturbation/iterative steps the total excitation field is known, and therefore the solution of any problem using the method is based solely on the expression for the field of an elemental source in a vacuum. The method appears to be very versatile, conceptually the simplest possible and remarkably rapid. It also has extremely low memory requirements even for very large problems, provided that computing time is not critical. In addition, it can be combined very efficiently with other available methods, e.g. with the method of moments for the analysis of conducting antennas in a vacuum to analyse such antennas in the presence of arbitrary dielectric or magnetic bodies.

DOI:10.1049/ip-h-2.1993.0006

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The feasibility of using diodes in linear microstrip antenna arrays to facilitate electronic beam scanning is investigated. The first concept concerns a microstrip line loaded with varactor diodes serving the dual purpose of phase shifter and feeder for a linear travelling wave array. Theoretical and practical results provide antenna design data on the number and type of diodes, optimisation of the radiating elements and temperature effects. Likely noise figure degradation, transient beam scanning response, and the antenna construction are other design aspects discussed. An array at 7.5 GHz containing 24 varactor diodes demonstrates that some 20° of beam scan is achievable before the travelling wave action is disrupted, and confirms the usefulness of the concept for applications demanding modest beam scan range and a simple low cost construction. The second concept introduced is a novel microstrip patch element with embedded diode and polariser enabling mixer action to take place. The theoretical and practical design of this antenna mixer element, and its deployment in an eight element linear beam scanning array at 2.92 GHz, is presented. Other mixer configurations, using additional diodes offering superior suppression of spectral products, are noted and the possible influence of the polariser on interelement mutual coupling investigated. Computations and measurements show that coupling effects are not significantly increased and confirm the usefulness of the antenna mixer element concept in beam forming array applications where no premixer low noise amplification is demanded.

DOI:10.1049/ip-h-2.1993.0007

出版商:IEE    

年代:1993

数据来源: IET

摘要:

In arrays of waveguide fed slots, the periodicity of the slots causes grating lobes off the principal planes, referred to as second-order beams. To suppress these lobes, parallel plates baffles) on both sides of the array can be used. In this paper, a linear array of longitudinal slots radiating between such baffles of finite height is analysed. The three-dimensional (3D) field problem is reduced to a two-dimensional (2D) problem via a Fourier transform. An integral equation for the 2D problem is developed and solved. The 3D radiation pattern, including the effect of a finite ground plane outside the baffles, is calculated from the 2D solutions. Results for various baffle dimensions, showing the attenuation of second-order beams, are presented and computed solution has been verified by measurements.

DOI:10.1049/ip-h-2.1993.0008

出版商:IEE    

年代:1993

数据来源: IET

摘要:

An integral equation formulation for analysing frequency selective surfaces (FSS) in cascade with dissimilar lattice geometries is described. The tangential field vectors are expanded by defining their Floquet modes according to the convolution theorem. The plane wave transmission coefficient of a multiresonant structure which has triangular and square lattices, with noninteger multiple ratios of their sides, has been computed.

DOI:10.1049/ip-h-2.1993.0009

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The contour-integral procedure is used to analyse the microstrip sectorialn-way power divider. The principal advantage of the present approach is that the resulting model is able to handle arbitrary sector angles, in contrast to the Green's function approach used by other researchers, which is valid only if the sector angle is a submultiple of Φ. Computational and experimental tests indicate that numerical accuracies of better than ± 1% are obtainable from the present model.

DOI:10.1049/ip-h-2.1993.0010

出版商:IEE    

年代:1993

数据来源: IET