Plane wave reflection from microstrip-patch arrays--Theory and experiment

Numerical solution of plane wave reflection from an infinite, planar rectangular microstrip-patch array on a grounded dielectric substrate is presented and compared to phased array simulator measurements with a good correlation. In the theory, particular attention is paid to the edge condition and to the convergence of the matrix elements which was accelerated by the Poisson summation technique, as well as to the rate of convergence of the overall solution. The agreement of the values of the resonant frequencies, the associatedQvalues, and their parametric dependence on geometry and frequency, establish confidence in the application of the method used, to prediction of performance of probe-excited microstrip-patch phased arrays.     

地面反射电磁波影响的分析

依据地面电磁波反射的形成原理,探讨了地面对电磁波的反射,对天线架设造成的影响,根据地面反射电磁波的影响,提出短波传播方法,以及天线如何架设,以便在天线及电磁波测量试验中减小测量误差,提高测量精度,达到较好的效果.     

Plane wave reflection and refraction involving a finitely conducting medium

In this work the structure of electromagnetic field in a lossy conducting medium is studied in detail. The meaning of the complex angle of refraction is explained in terms of real parameters involved in this problem. The concepts are illustrated with a wave refracting from air into pure water at a frequency of 95 GHz and an incidence angle of 60/spl deg/. The approach is similar to that used to derive refraction in many electromagnetic textbooks, such as Stratton (J. A. Stratton, 1941), which has been cited in many of the textbooks published since. Our results agree with his for the real angle of the equiphase surface of the refracted fields, but we explore further subjects, including the instantaneous and time-averaged Pointing vectors.     

Coherent wave reflection from a random half-space

An exact solution to the scalar Dyson equation in the bilocal approximation is given for a scalar wave obliquely incident on a random half-space whose mean dielectric constant is the same as that for the uniform nonrandom medium in the conjugate halfspace. It is shown that in addition to the dominant coherent wave, a second highly damped wave is weakly excited at the interface.     

Plane wave pulse backscattering from a low-density dielectric sphere

The solution to the scattering problem of a pulse incident on a low-density dielectric sphere is presented. Pulse modulated harmonic carriers and dc pulses are considered.     

Electromagnetic spherical wave reflection from a perfectly conducting surface of revolution

The problem of electromagnetic spherical wave reflection from a perfectly conducting surface of revolution is considered. The expressions for the first two terms of the high frequency asymptotic expansion for the reflected field are found. The analysis is based on Lee's theory of electromagnetic reflection from a conducting surface.     

Plane wave diffraction from a small half-sphere mounted on a large conducting body

Using image theory and the scattering solution for a sphere, the plane wave scattering by a small, perfectly conducting half-sphere on a conducting plane is obtained first. The scattered field can then be identified as that radiated from a combination of electric and magnetic dipoles on the plane. Equating these dipole fields to the corresponding radiation dipoles, we can solve for the induced scattering dipole moments. These moments can now be used to obtain the scattering of a small half-sphere mounted, for example, on large cones spheres, cylinders etc., provided the simpler problem of radiation dipoles on the large bodies has been solved first.     

Antenna gain calibration on a ground reflection range

The absolute gain of wide-beam antennas may be accurately measured using the method described. Both the theoretical and practiced aspects of gain calibration on a ground reflection antenna range are presented. The measurement procedures developed were used to calibrate a log-periodic antenna at selected frequencies from 250 to 400 MHz. Measured data at 300 MHz is tabulated and error contributions are analyzed, yielding a measurement accuracy ofpm0.27dB with a 95 percent confidence interval.     

Transient response of a dipole over a circular ground screen

The time-domain response of a vertical electric dipole located over a circular ground screen is considered. The relevant time-harmonic solution is used as a starting point. By making a number of approximations a very simple formula is obtained for the transient response of the far field when the dipole current moment is a ramp function of time. It is shown that for early times, the pattern response appears as if the ground screen were of infinite extent, while at very long times, the response approaches that expected for a homogeneous flat ground.     

Plane wave scattering from a cylinder loaded periodically withgroups of metallic rings

The scattering of an electromagnetic plane wave from a cylinder with circular cross-section loaded periodically with groups of metallic annular rings along the longitudinal axes is analysed. The incident plane wave is arbitrarily polarised and impinges on the cylinder at an oblique incidence     

Plane wave scattering from 2-D perfectly conducting superquadriccylinders

The plane-wave scattering from perfectly conducting two-dimensional cylinders of arbitrary squareness parameter is investigated. A uniform geometrical optics (UGO) solution valid across the smooth caustics generated by the surface poles or zero curvature (inflection) points is developed based on physical optics (PO). The classical geometrical optics solution is modified using a multiplicative transition function that compensates for the caustic singularities and accounts for the complex ray contributions emanating from nonspecular scattering centers located near the surface poles. The transition function is heuristically derived on the basis of the PO radiation integral and involves a generalized (higher-order) form of Airy functions. The resulting UGO solution for the scattered field is simple, easy to apply, and computationally efficient for electrically large cylinders. It compares well with physical optics (numerical integration) and moment-method solutions for both backscatter and limited bistatic configurations     

Plane wave diffraction by a thin dielectric half-plane

Expressions that apply for all observation points are derived for the field produced by a plane wave incident on a thin dielectric half-plane when the electric vector of the incident wave is parallel to the edge. Away from shadow boundaries the total field comprises an edge wave and a surface wave in addition to the transmitted and reflected waves of geometrical optics. The nature of the edge wave differs from that of a perfectly conducting half-plane in that both the amplitude and phase vary with the observation angle, for a given angle of incidence.     

Plane wave diffraction by a thick-walled parallel-plate impedancewaveguide

The diffraction of E-polarized plane waves by a thick-walled parallel-plate impedance waveguide is investigated rigorously by using the Fourier transform technique in conjunction with the mode-matching method. This mixed method of formulation gives rise to a scalar Wiener-Hopf equation of the second kind, the solution of which contains infinitely many constants satisfying an infinite system of linear algebraic equations. A numerical solution of this system is obtained for various values of the plate impedances, plate thickness, and the distance between the plates through which the effect of these parameters on the diffraction phenomenon are studied     

Plane wave scattering by slots on a ground plane loaded withsemicircular dielectric cylinders in case of oblique incidence andarbitrary polarization

Plane wave scattering by single or double slots loaded with semicircular dielectric cylinders is investigated in the most general case of oblique incidence and arbitrary polarization. To this end, systems of singular integral-integrodifferential equations of the first kind are constructed and discretized on the basis of recently developed algorithms. Several internal tests and extensive comparisons with available results were made in order to validate the numerical codes. Plotted results both for the surface magnetic current densities and the radar cross sections reveal how the scattering properties may be controlled by changing several physical and geometrical parameters of the structure     

Plane wave scattering by a material coated parabolic cylinder

An eigenfunction solution to the problem of transverse magnetic (TM) or transverse electric (TE) scattering by a coated parabolic cylinder is presented. Paralleling the well-known solution for the coated circular cylinder, eigenfunction expansions involving parabolic cylinder functions are obtained for the fields in the exterior and coating regions. Next, boundary conditions are enforced to obtain a pair of coupled equations for the unknown coefficients in the eigenfunction expansions for the fields. Unlike the corresponding solution for the coated circular cylinder, the eigenfunctions in the exterior and coating regions are not orthogonal, and an exact term-by-term solutions of these equations is not possible. Instead, the equations are solved by the method of moments. For thin coatings both an uncoupled-mode approximation and a surface-impedance model are described. In particular, for the TM polarization it is shown that a thin coating can be modeled by a specific nonuniform surface impedance for which an exact term-by-term solution is possible. Numerical data are presented, showing the convergence of the solution and comparing the solutions for the uncoupled-mode and surface-impedance models     

Plane wave scattering from an infinite planar dipole array buried in a lossy half-space

The plane wave scattering from an infinite planar impedance-loaded dipole array buried in a lossy half-space is investigated theoretically and experimentally. Formulations for the scattering field and the input impedance of the dipole are derived by using Floquet's theorem and the induced electromotive force (EMF) method. In order to demonstrate the validity of these formulations, the numerical examples for a concrete as the lossy medium at frequency 9.32 (GHz) are compared with the experimental data. The results show that this array, even when loaded by zero impedance, can greatly suppress the radio wave reflection from the concrete surface by choosing the array dimensions properly and the depth of the array surface.     

Plane wave scattering by a corrugated conducting cylinder atoblique incidence

The problem of scattering from a corrugated conducting cylinder due to an obliquely incident plane wave is solved by a boundary-value method. The region between the corrugations is considered as a medium with tensor permeability and tensor permittivity, which is a valid assumption when the corrugation constant is much less than the free-space wavelength. By loading this region with a dielectric material, one of the components of the scattered electric field in the far-field region can be altered significantly with no change in the other component. These components, in turn, determine the bistatic scattering cross sections, and the dielectric loading of the corrugated region appears to have no effect on the cross section due to the polarized component, while showing significant changes in the cross section due to the depolarized component     

On electromagnetic wave reflection from a randomly inhomogeneous medium with fluctuations of the complex permittivity

The Einstein-Fokker equation is solved in order to obtain an expression for the probability density of the absolute value of the correcting term for the reflection coefficient of a dielectric layer with 1D fluctuations of the real and imaginary parts of the permittivity. The applicability of the obtained results to studying multiyear ice in the Arctic is discussed, and computation taking into account the corresponding values of the input parameters of the problem is preformed.