F. Schwering

Bio: F. Schwering is an academic researcher from United States Department of the Army. The author has contributed to research in topics: Antenna (radio) & Microstrip antenna. The author has an hindex of 11, co-authored 41 publications receiving 474 citations.

Planar lower cost multilayer dual-band microstrip antenna

Abstract: A planar dual band antenna comprising three superimposed dielectric layers, ground plane on one external surface, a conductive patch on the other and parallel conductive strips at the interface of dielectric layers that is closer to the patch. The dielectric constant of the middle layer is different from that of the two other layers.

Diakoptic theory for multielement antennas

Abstract: A theory is presented for the analysis of multielement antennas which consist of interconnected, conductive structure elements of electrically small dimensions. The theory is based on the retarded electromagnetic potentials which permit a diakoptic approach to the problem. The antenna is broken up into its individual structure elements. Each element is assumed to be excited by currents which are impressed at its terminals, i.e., junctions with adjacent elements (current coupling) and by the electric fields of the currents and charges on all the other elements (fieid coupling). Both excitations are treated independently. Each impressed current produces a "dominant" current distribution, a characteristic of the element, which can be readily computed. Current coupling is formulated by "intrinsic" impedance matrices which relate the scaler potentials at the terminals of an element, caused by its dominant current distributions, to the impressed currents of the element. Field coupling produces "scatter" currents on all the elements and is formulated by a "fieid-coupling" matrix which relates the scalar potentials at the terminals, caused by field coupling, to the impressed currents at all the terminals. Intrinsic and "field-coupling" matrices are combined to form the "complete" impedance matrix of the diakopted antenna. Enforcing continuity of the currents and equality of the scalar potentials at all the interconnections between the elements yields a system of linear equations for the junction currents and the input impedance of the antenna. Current coupling dominates field coupling. Fieid coupling is primarily affected by the dominant current distributions of the elements, and in general the scatter currents have negligible effect on it. Although detailed numerical investigations will be presented in another paper, a simple example is included here to demonstrate that the diakoptic theory yields very good results even if greatly simplified assumptions are made.

A millimeter-wave omnidirectional circular dielectric rod grating antenna

Abstract: A millimetre-wave omnidirectional circular dielectric rod grating antenna is investigated theoretically and experimentally. As an eigenvalue problem, the antenna is analyzed with the rigorous mode matching method. The radiation characteristics of the antenna are calculated and measured in the Ka-band frequency range. A comparison between the experimental results and the theoretical predictions is made and good agreement is found. The practicality of the omnidirectional antenna and the effectiveness of the theory are thus justified. >

Scattering by periodic metal surfaces with sinusoidal height profiles--A theoretical approach

Abstract: A theory of scattering by periodic metal surfaces is presented that utilizes the physical optics approximation to determine the current distribution in the metal surface to first order, but modifies this approximate distribution by multiplication with a Fourier series whose fundamental period is that of the surface profile (Floquet's theorem). The coefficients of the Fourier series are determined from the condition that the field radiated by the current distribution into the lower (shielded) half-space must cancel the primary plane wave in this space range. The theory reduces the scatter problem to the familiar task of solving a linear system. For certain basic types of surface profiles, including the sinusoidal profile considered here, the coefficients of the linear system are obtained as closed form expressions in well-known functions (Bessel functions for sinusoidal profiles and exponential functions for piecewise linear profiles). The theory is thus amenable to efficient computer evaluation. Comparison of numerical results based on this theory with data obtained by recent numerical schemes shows that for depths of surface grooves less than a wavelength and for unrestricted groove widths, reliable and comparable, if not more accurate, data is obtained, in many cases at considerably cheaper computational cost.

Planar dual-band microstrip antenna

Abstract: A novel dual-band microstrip antenna is introduced. The entire structure is planar and can be easily mass-produced by using printed-circuit technology. The antenna consists of multiple layers with metallic strips placed at one of the dielectric interfaces under the radiating patch. The resonant frequencies can be selected over a wide frequency range, and the impedance matching at those two frequencies is relatively simple. The physically intuitive cavity model is used for the analysis. A relatively simple design scheme is included. >

Waves in active and passive periodic structures: A review

Abstract: The theory and recent applications of waves in periodic structures are reviewed. Both the Floquet and coupled waves approach are analyzed in some detail. The theoretical part of the paper includes wave propagation in unbounded and bounded active or passive periodic media, wave scatterring from periodic boundaries, source radiation (dipole, Cerenkov, transition, and Smith-Purcell) in-periodic media, and pulse transmission through a periodic slab. The applications part covers the recent development in a variety of fields: distributed feedback oscillators, filters, mode convertors, couplers, second-harmonic generators, deflectors, modulators and transducers in the fields of integrated optics and integrated surface acoustics. We also review the work on insect compound eyes, mehanical structures ocean waves, pulse compressions, temperature waves, and cholestric liquid crystals. Particles interaction with crystals is briefly reviewed, especially in the case of zeolite crystals and supelattices. Recent advances in fabrication techniques for very fine gratings me also covered. Finally, speculations about future problems and development in the field of waves in periodic structures are given.

A critical survey of approximate scattering wave theories from random rough surfaces

Abstract: This review is intended to provide a critical and up-to-date survey of the analytical approximate methods that are encountered in scattering from random rough surfaces. The underlying principles of the different methods are evidenced and the functional form of the corresponding scattering amplitude or cross-section is given. The reader is referred to the original papers in order to obtain the explicit expressions of the coefficients and kernels. We have tried to identify the main strengths and weaknesses of the various theories. We provide synthetic tables of their respective performances, according to a dozen important requirements a valuable method should meet. Both scalar acoustic and vector electromagnetic theories are equally addressed.

Wave-front Transformation with Gradient Metasurfaces

Abstract: Metasurfaces are engineered systems that enable advanced control of electromagnetic waves over deeply subwavelength thicknesses. Researchers make a careful study of the use of metasurfaces to transform the impinging optical wave front.

Conformal wide band surface wave radiating element

Abstract: Conformal antennas and methods for radiating radio frequency energy using conformal antennas are provided. In particular, one or more tapered feeds can be provided as part of or interconnected to a conductive top plate. The one or more tapered feeds have a depth that decreases from a feed point to a tip. The tip of the one or more tapered feeds is adjacent a cavity formed over a lens region. An aperture over the lens region can be covered or filled by an impedance surface. This impedance surface may comprise a frequency selective surface. Alternatively, a frequency selective surface can be provided over the lens region of an antenna incorporating one or more stripline feeds.

Continuous transverse stub element devices and methods of making same

Abstract: A dielectric material is formed into a structure having two parallel broad surfaces with one or more raised integral portions extending transversely across at least one of the broad surfaces. The exterior is uniformly conductively coated resulting in a parallel plate waveguide having a continuous transverse stub element disposed adjacent one plate thereof. Purely reactive elements are formed by leaving the conductive coating on the terminus of the stub element, or by narrowing the terminus of the stub element. Radiating elements are formed when stub elements of moderate height are opened to free space. Radiating, coupling and/or reactive continuous transverse stub elements may be combined in a common parallel plate structure in order to form a variety of microwave, millimeter wave and quasi-optical components including integrated filters, couplers and antenna arrays. Fabrication of the dielectrically-loaded continuous transverse stub element can be efficiently accomplished by machining, extruding or molding the dielectric structure, followed by uniform conductive plating in order to form the parallel plate transmission line. In the case of antenna applications, machining or grinding is performed on the stub terminus to expose the dielectric material at the end of the stub element.