606 research outputs found
Effect of imperfect flat earth on the vertically polarized radiation of a cylindrical reflector antenna
Cataloged from PDF version of article.The radiation of a circular cylindrical reflector
antenna in the presence of imperfect flat earth is treated in an
accurate manner. The boundary value problem is formulated in
terms of a full-wave integral equation converted to the dual-series
equations and then regularized by using analytical inversion
of the static part. The resulting Fredholm second-kind matrix
equation is solved numerically with guaranteed accuracy. The
feed directivity is included in the analysis by using the complex
source-point method. Various antenna features, which include the
overall directivity, efficiency, gain, and radiated and absorbed
power fractions have been calculated and compared with the
free-space antenna characteristics. They show some phenomena
not predicted by approximate techniques
Integral equation anlaysis of an arbitrary-profile and varying-resistivity cylindrical reflector illuminated by an E-polarized complex-source-point beam
Cataloged from PDF version of article.A two-dimensional reflector with resistive-type boundary conditions and varying resistivity is considered. The
incident wave is a beam emitted by a complex-source-point feed simulating an aperture source. The problem is
formulated as an electromagnetic time-harmonic boundary value problem and cast into the electric field integral
equation form. This is a Fredholm second kind equation that can be solved numerically in several ways.
We develop a Galerkin projection scheme with entire-domain expansion functions defined on an auxiliary circle
and demonstrate its advantage over a conventional moment-method solution in terms of faster convergence.
Hence, larger reflectors can be computed with a higher accuracy. The results presented relate to the elliptic,
parabolic, and hyperbolic profile reflectors fed by in-focus feeds. They demonstrate that a partially or fully resistive
parabolic reflector is able to form a sharp main beam of the far-field pattern in the forward half-space;
however, partial transparency leads to a drop in the overall directivity of emission due to the leakage of the
field to the shadow half-space. This can be avoided if only small parts of the reflector near the edges are made
resistive, with resisitivity increasing to the edge. © 2009 Optical Society of Americ
Analysis of an arbitrary conic section profile cylindrical reflector antenna, H-polarization case
Cataloged from PDF version of article.Two-dimensional scattering of waves by a perfectly electric
conducting reflector having arbitrary smooth profile is studied in the H-polarization
case. This is done by reducing the mixed-potential integral equation
to the dual-series equations and carrying out analytical regularization.
To simulate a realistic primary feed, directive incident field is taken as a
complex source point beam. The proposed algorithm shows convergence
and efficiency. The far field characteristics are presented for the reflectors
shaped as quite large-size curved strips of elliptic, parabolic, and hyperbolic
profiles
Accurate Simulation of Reflector Antennas by the Complex Source-Dual Series Approach
Cataloged from PDF version of article.The radiation from circular cylindrical reflector antennas is treated in an accurate manner for both polarizations. The problem is first formulated in terms of the dual series equations and then is regularized by the Riemann-Hilbert problem technique. The resulting matrix equation is solved numeridy with a guaranteed accuracy, and remarkably Little CPU time is needed. The feed directivity is included in the analysis by the complex source point method. Various characteristic patterns are obtained for the front and offset-fed reflector antenna geometries with this analysis, and some comparisons are made with the high frequency techniques. The directivity and radiated power properties are also studied
Analysis of the elliptic-profile cylindrical reflector with a non-uniform resistivity using the complex source and dual-series approach: H-polarization case
Cataloged from PDF version of article.An elliptic-profile reflector with varying resistivity is analyzed under the illumination
by an H-polarized beam generated by a complex-source-point (CSP) feed. The
emphasis is done on the focusing ability that is potentially important in the applications in
the optical range related to the partially transparent mirrors. We formulate the corresponding
electromagnetic boundary-value problem and derive a singular integral equation from
the resistive-surface boundary conditions. This equation is treated with the aid of the regularization
technique called Riemann Hilbert Problem approach, which inverts the stronger
singular part analytically, and converted to an infinite-matrix equation of the Fredholm 2nd
kind. The resulting numerical algorithm has guaranteed convergence. This type of solution
provides more accurate and faster results compared to the known method of moments. In
the computations, a CSP feed is placed into a more distant geometrical focus of the elliptic
reflector, and the near-field values at the closer focus are plotted and discussed. Various far-
field radiation patterns including those for the non-uniform resistive variation on the reflector
are also presented
Analysis of an arbitrary-profile, cylindrical, impedance reflector surface illuminated by an E-polarized complex line source beam
Cataloged from PDF version of article.Electromagnetic scattering from a cylindrical reflector surface having an arbitrary
conic section profile is studied. We assumed an electrically thin layer antenna
illuminated by a complex line source in E-polarization mode. Our boundary value
formulation, without loss of generality, involves an integral equation approach
having impedance-type thin-layer boundary conditions. For simplicity, we also
considered both faces of the reflector of the same uniform impedance value. Our
computation employs the Method of Analytical Regularization (MAR) technique:
the integral equations are converted into the discrete Fourier transform domain
yielding two coupled dual series equations, which are then solved by the Fourier
inversion and Riemann Hilbert Problem techniques. We demonstrate the accuracy
and the convergence behaviors of our numerically solved MAR results that can
serve as an accurate benchmark for comparison with widely used results obtained
by approximate boundary conditions
Numerical optimization of a cylindrical reflector-in-radome antenna system
Cataloged from PDF version of article.Accurate numerical optimization based on the rigorous
solution of the integral equation using the method of
analytical regularization is performed for the cylindrical reflector
antenna in a dielectric radome. It is shown that the multiple
scattering in this system is more significant for the optimum
radome design than any nonplane-wave effects or the curvature of
the radome. We claim that, although the common half-wavelength
design is a good approximation to avoid negative effects of the
radome (such as the loss of the antenna directivity), one can, by
carefully playing with the radome thickness, its radius, reflector
location, and the position of the feed, improve the reflector-inradome
antenna performance (e.g., increase the directivity) with
respect to the same reflector in free-space
Validity and limitations of the median-line integral equation technique in the scattering by material strips of sub-wavellength thickness
Cataloged from PDF version of article.Considered is the 2-D scattering of a plane wave by a thin flat material strip. The data obtained by using the empirical method of generalized boundary conditions and singular integral equations on the strip median line are compared with the results of solving the Muller boundary integral equation that takes full account of strip thickness. Discretization of integral equations in both cases is performed using the Nystrom methods that lead to convergent algorithms. Numerical results cover E and H polarizations and two types of thin strips: conventional dielectric and metal in the optical range. The validity and limitations of approximate model are established and discussed
Calculation of radome-enclosed aperture antenna IN 3-D
The exact mathematical model of an aperture antenna and the image theory are used to develop exact and PO integral representations of the fields radiated by radome-enclosed aperture antenna. The desired problem is reduced to finding fields of a plane wave diffracted on the "symmetrized" radome. The passage of the wave through the wall of the radome is analysed by means of geometrical optics. Caustic influence is taken into account, and the contribution of stationary phase points of reflected field to the far-side radiation is discussed. Radiation patterns for antennas with a specified ampliphase distribution enclosed in spherical and parabolic radomes are analysed. © 2010 IEEE
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