摘要:

A further study is made of the resonant frequency of circular microstrip patches. Based on earlier work, the resonant frequency problem is formulated in terms of an integral equation. Galerkin's method is used to calculate the resonant frequencies of nonaxial symmetric modes in different circular microstrip patches. Using the database built by Galerkin's method, a curvefitting formula is developed to reproduce the accurate resonant frequency rapidly. The accuracy of this formula is within 1.0%. This formula is useful for the computer-aided design of microstrip antennas and microwave integrated circuits.

DOI:10.1049/ip-h-2.1988.0060

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Methods are available for the independent synthesis of array excitations which provide either optimum sum or optimum difference pattern performance. In the paper a technique is described to effect the simultaneous synthesis of both sum and difference patterns of a linear antenna array which utilises sub-arraying to increase the number of degrees of freedom above that available with the usual two-section feed network. The particular approach (referred to here as excitation matching) attempts to obtain an optimum sum (difference) and a ‘best compromise’ difference (sum) pattern, by dealing directly with the independently optimum excitations and appropriately adjusting the sub-array weights.

DOI:10.1049/ip-h-2.1988.0061

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The paper deals with the evaluation of Sommerfeld integrals that appear in the rigorous analysis of radiating objects embedded in a layered medium. The discrete images of a horizontal electric dipole above or within a multilayered medium, can be obtained by numerically approximating the kernel in a Sommerfeld type integral, using a series of exponential functions with different complex coefficients. The distance limitation of the image theory expression is eliminated by cooperating the contribution of the surface waves. The validity of the image theory is examined by the method of numerical integration.

DOI:10.1049/ip-h-2.1988.0062

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The dichroic microstrip antenna concept is reported which enables an antenna aperture to function at two widely separated frequenciesfHandfL. The innovation centres on the utilisation of printed frequency selective mesh conductors as microstrip patch antennas atfL, which in turn become transparent to near-field radiation atfH, from another microstrip array in close proximity. An approximate analysis shows that the mesh perimeter scattering has a dominant effect on the degree of invisibility achievable, and for simple configurations the NEC computer program models the behaviour which also includes a leaky wave action. Radiation pattern measurements on several microwave and millimetre dual band arrays using low permittivity (εr= 1.05) substrates illustrating the concept are presented and a further development concerning an array that also functions as an electromagnetic window. The measurements show the effect of mesh strip width, patch impedance levels, band separation and feeder radiation, but the small dissipative loss in the mesh is difficult to precisely ascertain. Despite the complexity of effects produced by the mesh its transparency is good and radiation pattern perturbations, reduced by the array factor, are typically 1 to 2 dB. However, the use of higher permittivity substrates may lead to some bandwidth restrictions and some increased mesh dissipation loss. Finally, numerous possible applications for the innovative dual band structures presented, are noted.

DOI:10.1049/ip-h-2.1988.0063

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The electromagnetic boundary value problem of finite thickness orthogonal waveguides coupled by inclined slots is studied using a moment method and dyadic Green's function theories. The coupling properties between two inclined slots are analysed and a model of equivalence circuits is put forward. Theoretical results are presented for scattering and impedance parameters of slots. In general, these are in good agreement with the experimental measurement.

DOI:10.1049/ip-h-2.1988.0064

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The moment method solution for the scattering parameters of radiating slots in waveguides has recently been shown to be of sufficient accuracy to form the basis of a purely theoretical CAD synthesis package for slotted-waveguide array antennas. However, the efficient implementation of such a package can be considerably aided if some prior knowledge of the functional relationships between the slot scattering or admittance characteristics, and its dimensional parameters is available. These relationships have been discussed fully, in the literature, for all dimensional parameters with the exception, curiously, of the width parameter. The paper includes some theoretical and experimental observations of those width effects that are most relevant to CAD developments.

DOI:10.1049/ip-h-2.1988.0065

出版商:IEE    

年代:1988

数据来源: IET

摘要:

We present a simple model for the input impedance of a rectangular microstrip patch antenna. This model is well suited for computer aided design (CAD). It is based on classical methods: (a) the cavity model determining the frequency and the input resistance at resonance, (b) the dynamic permittivity of a rectangular microstrip patch antenna (to take into account the influence of the fringing field at the edges of the rectangular patch antenna) and (c) the resonant parallelRLCcircuit with an inductive reactance. This model is valid for electrically thick substrates. The theoretical results are in good agreement with experimental data.

DOI:10.1049/ip-h-2.1988.0066

出版商:IEE    

年代:1988

数据来源: IET

摘要:

A technique is proposed that evaluates efficiently the coefficients of a spherical wave expansion and is applicable to the optical synthesis of shaped beams. The method which extends previously published work, avoids the need to directly evaluate numerically a double integral to compute each coefficient. Examples are given of the technique when applied to Westcott's far-field optical synthesis procedure. The use of a tapered optical field distribution to improve the radiation characteristics of a shaped beam antenna is demonstrated.

DOI:10.1049/ip-h-2.1988.0067

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The methods currently used for computation of resonant frequencies of a microwave dielectric resonator all require knowledge of the field structures, both inside and outside the resonator, and therefore are strictly limited. The paper discusses the general principle of solution of resonant frequencies of the dielectric resonator by the boundary element method (BEM). Through discretisation, the boundary integral equations are reduced to a generalised eigenvalue equation, with the eigenvalues as the resonant frequencies. The method presented is, in principle, applicable to an arbitrarily shaped dielectric resonator. Some results are given and compared with previous data published as a demonstration of the validity of the method.

DOI:10.1049/ip-h-2.1988.0068

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The paper offers a new approach to boundary value problems. It is a variant of the least squares boundary residual method (LSBRM), combined with the fast Fourier transform (FFT) of basis functions and boundary conditions. This variant makes possible a considerable saving of computation time in comparison with the original LSBRM. The procedure was successfully demonstrated on diffraction and eigenvalue problems.

DOI:10.1049/ip-h-2.1988.0069

出版商:IEE    

年代:1988

数据来源: IET