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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.
The pattern synthesis technique described here is unique in that it allows the power pattern to be optimized in a very useful sense over the desired operating band of the array. This is an improvement over previous techniques involving constraints on such artificial parameters as source norm and superdirectivity ratio which do not in fact ensure a useful pattern bandwidth. The procedure described...
A model for determining the antenna phase center and its movement due to multipath reception is defined and analyzed. It is shown that for the azimuth antenna in the Microwave Landing System (MLS) the phase center is susceptible to interaction of the direct signal and the indirect signals reflected by the ground.
The development of high speed devices and materials for millimetre wave integrated antenna systems has sustained a need for ever faster and more flexible measurement systems. Several methods of performing time and frequency domain measurements of antenna near-field patterns and substrate electric fields exist using electro-optic sampling (EOS). An important feature of electro-optic sampling in antenna...
Electromagnetic scattering from axisymmetric conducting bodies partially coated by thin materials is computed numerically. The formulation of the problem is based on an existing formula for a completely coated object. This formulation is valid as the coating thickness approaches zero. Other existing implementations fail to obtain correct results in this case. Numerous examples are considered. The...
The quasi-TEM characteristics of a microstrip line on a multilayered cylindrical dielectric substrate partially embedded in a perfectly conducting ground plane are rigorously determined. Exact expressions for the potential distributions inside and outside the substrate, charge distributions on the strip, and capacitance are derived.
In this paper, an approximate method is described for solving the problem of electromagnetic scattering by two coaxial prolate spheroids, with their major axes along the common axis. The incident wave is considered to be a monochromatic uniform plane electromagnetic wave of arbitrary polarization, and angle of incidence. The method is based on the exact solution to scattering of a plane wave by a...
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...
The effect of a finite distance of the signal source on the performance of an Applebaum array has been studied extensively in the literature. It has been concluded that unless the Applebaum Array is focused at the exact source location, the degradation of the output signal-to-noise ratio becomes unacceptable. The Automatic focusing technique (AFT) developed by the author for long wavelength imaging...
This paper describes a novel method for the measurement of the frequency response of the indoor RF propagation channel utilizing an HP network analyzer. Preliminary measurements of the frequency response of the channel in the frequency bands 900–1000MHz and 1.6–1.8GHz are reported. These measurements determine the dependence of the rms excess delay time on the separation between the transmitting and...
When making ground plane based antenna pattern measurements in small anechoic chambers or compact ranges one is often restricted to a ground plane which is only a few wavelengths in extent. The fields scattered from the edges of this finite ground plane interfere with the fields radiated by the antenna, and are usually apparent in the radiation pattern as scalloping on the frontside of the pattern,...
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.
A radial line slot antenna (RLSA) is a kind of slotted waveguide array for DBS reception [1][2]. It is free of conductor loss and the aperture efficiency is more than 75%, twice as high as conventional planar antennas [3]. Those performances have been realized for double-layered RLSAs with uniform slot length.
Dielectric resonator are high permittivity ceramic structures which couple easily into planar and waveguide circuits. One of their more practical uses is in realizing high Q tuned circuits on planar microwave circuits. For such applications the important resonator parameters are, the resonant frequency, the Q of the mode and the coupling coefficients, among others. Most of the work in the past on...
An antenna pattern measurement system has been developed which operates over the frequency range 1 to 12.4 GHz. The system makes pattern measurements and tests gain, beamwidths, and sidelobe levels under far-field conditions. Measurements using a Hewlett-Packard 8410A vector network analyzer as the receiver are managed by an in-house-developed software package for use on an IBM PC-AT microcomputer.
Analytic expressions are derived for the input admittance and the current distribution along the arbitrarily-fed insulated antenna in air which is excited across a gap of non-zero width. In this work, the Wiener-Hopf type analysis for a center fed insulated antenna is extended to the case of asymmetrically excited antenna. Present analysis which does not employ superposition yields final expressions...
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...
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