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The influence of the ground on the fields of antennas has been discussed sporadically in the literature for many years. In most propagation calculations, it is assumed that the transmitting antenna has a fixed di-pole moment and the ground is taken to be a perfect conductor or possibly a homogeneous imperfectly conducting half-space. In practice, however, some kind of ground system is employed. Usually...
A theoretical study is presented of the input impedance and bandwidth of biconical microstrip antennas asymmetrically excited by a coaxial probe feed. The antenna consists of a conducting cone cap on a grounded cone separated by an electrically thin dielectric. The structure is of biconical type. The analytic results for zero order modes (including the special case, TEM mode) of the biconical structure...
Parallel plate EMP simulators can be made from two sets of parallel wires to reduce wind loading, weight, and icing problems. The available literature on this kind of simulator construction is inadequate for the prediction of such basic design information as characteristic impedance and field enhancement.
The Transmission-Line Matrix (TLM) method, originated by Johns and Beurle [1] is based on equivalent circuit models of Maxwell's equations and has been used extensively to analyze electromagnetic field problems [2]. In this paper the application of the TLM method to the simulation of radiation and scattering problems, in which there is a plane interface separating two infinite homogeneous media, is...
This paper describes how a linear relationship between control voltage and transmission coefficient can be obtained for a PIN diode biphase attenuator. This linearisation comes out from a theoretical study of the attenuator. Results given here, are obtained for a microstrip biphase attenuator optimised at 1.59 GHz.
The usefulness of broadband impedance matching to increase the bandwidth of a microstrip patch antenna is illustrated using three different antenna configurations. Measured data for a patch antenna was incorporated into commercial CAD software to design a matching network. Design limitations are also discussed. Practical design examples and experimental results are given which clearly demonstrate...
The software EMsim™∗ has a graphical shell and a field theory “engine” WATMIC. This paper discusses the adjustments to the engine to improve the accuracy to 1 % error or less. The only limitation for new WATMIC is that it does not account for surface wave of substrates thicker than 0.05λd (in the substrate).
The objective of this paper is to present a numerical technique for the analysis of printed circuits and antennas using the grounded dielectric slab Green's functions. For the dynamic case, the Green's functions are quite complicated and require the numerical computation of certain semi-infinite integrals commonly known as the Sommerfeld integrals. In this paper certain approximations have been made...
Interest in the use of microstrip patches for array antennas has prompted investigations into numerous feed mechanisms. One of the most interesting, which offers considerable advantages over the others, is aperture coupling. In the paper that follows, the coupling of a feedline to a rectangular patch, through an aperture in the ground plane separating them, is described. Modal field expansion is used...
An analysis of slot-coupled double layer microstrip lines is presented. A modal field expansion method and the Poynting theorem are applied to derive the input impedance as seen by the feed line at the slot. By comparing the theoretical results with measured values, the accuracy of the method is verified.
A theoretical and experimental study of the patch antenna input impedance variation with feedline width is presented. Measured results were compared with some of the currently available numerical models. A limitation of these numerical models was established and the techniques will be modified to overcome this shortcoming.
A moment method solution for the Electric Field Integral Equation is used to analyse a rectangular patch air-dielectric microstrip antenna on an infinite size ground plane. The patch surface is modelled by surface patch modes. The mutual impedance between the surface patch modes are calculated using a simple formula. The effect of the fringing field at the edges of the rectangular patch is derived...
This paper presents some original results on mutual coupling between two identical stacked microstrip antennas. The mutual coupling is calculated by using the reciprocity theorem in the Spectral Domain. The theoretical results are in good agreement with experiments. As expected, we observe that the mutual coupling between stacked patches is stronger than that between unstacked patches.
In this paper, after an overview of Moment Method, a cylindrical dipole with arbitrary feed location and arbitrary diameter is analysed. Elements of impedance matrix are formulated with piecewise linear and piecewise sinusoid functions, in a Galerkin procedure. Thereafter current distribution and input impedance of the antenna are computed. Numerical results are in agreement with variational solution...
A circular array receiving antenna is highly attractive for radio direction finding because of its geometrically circular symmetry and, thereby, the periodicity of its electromagnetic features, such as mutual coupling between elements of the array, when its beam is scanned electronically through 360 degrees. In radio direction finding systems, the elements of an array are considered to be sensors...
This paper considers the modal current distribution on a loop antenna which is situated coaxially on the interface of a double-layered cylindrically stratified media. The loop is modelled as a ΣNn=1cos nφδ(z) electric current distribution under the influence of a unit amplitude rectangular voltage pulse function. The determination of the modal amplitudes of the current distribution follows an exact...
Electromagnetically coupled (EM fed) microstrip patches have their feed structure fabricated on a thin substrate located between the patch antenna and its ground plane as shown in Figure 1. This dual layer design has two main advantages over conventional single layer microstrip antennas. First, spurious radiation from the feed network can be reduced by decreasing the height and increasing the dielectric...
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