A General Procedure To Set Up The Dyadic Green's Function Of Multilayer Conformal Structures And Its Application To Microstrip Antennas


Book Description

This paper presents a generalized approach to derive the dyadic Green's function of arbitrary multilayer structures in planar, cylindrical and spherical coordinate systems. It is based on a full-wave equivalent-circuit representation that makes it possible to apply simple network analysis techniques. The planar stratified structures may be laterally bounded or open, the cylinders or spheres circumferentially closed or limited sectors. The procedure can be extended to other coordinate systems and anisotropic materials by means of a generalized transmission-line approach. For a demonstration of the applicability of this method, the derivation of the dyadic Green's functions in spectral domain of some commonly used cylindrical and spherical microstrip structures is presented.




Foundations of Antenna Engineering: A Unified Approach for Line-of-Sight and Multipath


Book Description

This is the first textbook that contains a holistic treatment of antennas both for traditional antennas mounted on masts (Line-of-Sight antenna systems) and for small antennas used on modern wireless devices such as smart phones being subject to signal variations (fading) due to multipath propagation. The focus is on characterization, as well as describing classical antennas by modern complex vector theory - thereby linking together many disciplines such as electromagnetic theory, classical antenna theory, wave propagation, and antenna system performance. Overall, this book represents a rethinking of the way basic antenna theory is presented. The book contains many references to important old and new papers and books on the analysis and design of the most useful antenna types, for the most interested readers.







Dyadic Green,Äôs Function for Multilayered Planar, Cylindrical, and Spherical Structures with Impedance Boundary Condition


Book Description

The integral equation (IE) method is one of the efficient approaches for solving electromagnetic problems, where dyadic Green,Äôs function (DGF) plays an important role as the Kernel of the integrals. In general, a layered medium with planar, cylindrical, or spherical geometry can be used to model different biomedical media such as human skin, body, or head. Therefore, in this chapter, different approaches for the derivation of Green,Äôs function for these structures will be introduced. Due to the recent great interest in two-dimensional (2D) materials, the chapter will also discuss the generalization of the technique to the same structures with interfaces made of isotropic and anisotropic surface impedances. To this end, general formulas for the dyadic Green,Äôs function of the aforementioned structures are extracted based on the scattering superposition method by considering field and source points in the arbitrary locations. Apparently, by setting the surface conductivity of the interfaces equal to zero, the formulations will turn into the associated problem with dielectric boundaries. This section will also aid in the design of various biomedical devices such as sensors, cloaks, and spectrometers, with improved functionality. Finally, the Purcell factor of a dipole emitter in the presence of the layered structures will be discussed as another biomedical application of the formulation.
















Efficient Asymptotic Closed Form Approximation for Dyadic Green's Function for Anisotropic Substrates


Book Description

An efficient closed form asymptotic representation for a grounded double-layered anisotropic uniaxial geometry is developed. The large parameter of this asymptotic development is directly proportional to the lateral separation between the source and observation point. However the asymptotic solution remains accurate even for very small (a few tenths of a wavelength) lateral separation of the source and field points. the asymptotic closed form dyadic Green's function has been cast in such a form that the physical behavior of the electromagnetic fields due to anisotropy of the medium reveals itself through a simple mathematical parameters. Thus, the physical understanding of the interaction of the spatially confined source with an anisotropic (uniaxial) double-layered grounded slab is greatly enhanced through the newly developed asymptotic closed form representation of the dyadic Green's function. Also, this efficient representation is very useful in the moment method (MM) solution of the current excited on the microstrip antennas and arrays in a grounded double- layered uniaxial geometry, as well as the volumetric current excited within a dielectric scatterer buried in a grounded double layered anisotropic uniaxial slab. The MM analysis, especially for microstrip arrays and guided wave structures, requires a very large number of computations where the lateral distance between the source and the field points in the dyadic Green's function can range from extremely small to very large values.




Coplanar Waveguide Circuits, Components, and Systems


Book Description

Up-to-date coverage of the analysis and applications of coplanar waveguides to microwave circuits and antennas The unique feature of coplanar waveguides, as opposed to more conventional waveguides, is their uniplanar construction, in which all of the conductors are aligned on the same side of the substrate. This feature simplifies manufacturing and allows faster and less expensive characterization using on-wafer techniques. Coplanar Waveguide Circuits, Components, and Systems is an engineer's complete resource, collecting all of the available data on the subject. Rainee Simons thoroughly discusses propagation parameters for conventional coplanar waveguides and includes valuable details such as the derivation of the fundamental equations, physical explanations, and numerical examples. Coverage also includes: Discontinuities and circuit elements Transitions to other transmission media Directional couplers, hybrids, and magic T Microelectromechanical systems based switches and phase shifters Tunable devices using ferroelectric materials Photonic bandgap structures Printed circuit antennas