A.J. Giarola

Analysis of microstrip wraparound antennas using dyadic Green's functions

The radiation pattern of microstrip wraparound antennas was obtained here using a theory based on dyadic Greens functions for concentric-cylindrical layered media. The dielectric layer that is usually neglected as a first-order approximation was considered here. An asymptotic expression for the dyadic Greens function that takes into account only the space wave is first obtained. Radiation patterns for various radii, permittivities, and thicknesses of the dielectric layer of a microstrip wraparound antenna were obtained using as a source a uniform annular magnetic current obtained by means of a cavity model with conducting magnetic walls. The calculated values of the percent pattern coverage decreases as the thickness and the permittivity of the dielectric layer increase. The influence of the dielectric layer is more pronounced for radiation direction near that of the axis of the cylindrical surface. It is also shown that the radiation patterns at a frequency of 2.0 GHz are not much dependent on the diameter of the antenna for values from 3 to 120 in.

Microstrip antenna on a conical surface

A theoretical analysis of microstrip antennas on conical conducting surfaces is presented. The resonant frequency, input impedance, radiation pattern, quality factor, and efficiency are obtained for a general geometry. Numerical results for a patch antenna with a cone angle theta /sub 0/=33.88 degrees operating in the fundamental TM/sub 01/ mode are shown. >

Analysis of an infinite array of rectangular anisotropic dielectric waveguides using the finite-difference method

The finite-difference method is used in the analysis of the propagation characteristics of an infinite array of rectangular dielectric waveguides. Particular attention is devoted to the mode coupling analysis and a comparison with results from an integral equation method is presented. The wave equation is solved in terms of the transverse components of the magnetic field, resulting in an eigenvalue problem with the elimination of spurious modes. The formulation is general and may be applied to the solution of other problems, including those with anisotropic dielectrics and with a continuous variation of the index of refraction profile in the waveguide cross section. >

Electromagnetic wave propagation in multilayer dielectric periodic structures

The propagation characteristics in multilayer dielectric periodic structures, that extends a previous analysis by introducing additional dielectric layers, is presented. It is applied to propagating electromagnetic modes along the longitudinal and transverse directions of the structures periodicity. The use of Floquets theorem reduces the analysis to a single cell of the propagating fields for both, TE and TM polarizations. Results showing the effect of varying the layers thickness and electric permittivity on the propagation constant and on the field distributions within each cell are presented as well as the band structure associated with the periodic structure. >

Dyadic Green's Functions and Their Use in the Analysis of Microstrip Antennas

Publisher Summary This chapter discusses the influence of the dielectric substrate on some electrical properties of microstrip antennas and uses dyadic Greens functions in media consisting of plane parallel or cylindrical concentric layers. It provides the definition and basic properties of dyadic functions and of the free-space dyadic Greens function. The cavity model with conducting magnetic side walls for the calculation of the radiated fields from the antenna has been presented. The chapter introduces the expansion of the free-space dyadic Greens functions in vector wave functions in the rectangular and cylindrical coordinate systems. Expressions of the dyadic Greens functions for media with three and four layers, plane and parallel to each other, and with three concentric cylindrical layers are then obtained. The chapter considers the effect of a dielectric cover on the radiation patterns of microstrip ring antennas and the effect of the dielectric substrate on the radiation patterns of wraparound antennas. Analysis of the problem of excitation of surface waves in the dielectric-air boundary of microstrip disk antennas has been developed with the objective of obtaining the effect of the dielectric substrate on the directivity and efficiency of excitation of space waves.

Analysis of the selective behavior of multilayer structures with a dielectric grating

The potential use as dichroic surfaces in the millimeter frequency band of multilayer dielectric structures with a grating in one of the layers is examined. It is shown that the selectivity of the structure may be increased by using a convenient array of dielectric sections in the characteristic cell of the periodic layer. It is also shown how the selective behavior of the structure depends on the angle of incidence of the wave that excites the structure and on the height-periodicity ratio of the periodic layer. In addition, for an unloaded periodic layer, an approximate procedure is described to predict how many times and at which frequencies maximum reflection occurs. The effect of loading the periodic layer with increasing number of dielectric layers is examined with the conclusion that the number of frequencies where maximum reflection occurs may be increased. >

PACMO: A Comprehensive CAD Package for Microwave Devices

An introduction to a new computer-aided-design (CAD) package (PACMO), particularly useful for graduate courses in microwave devices, is presented. It contains subroutines for the design and analysis of ten microwave devices. The subroutines were developed to give rapid and practical help in obtaining design parameters based on the performance of the devices to be constructed. Although they are based mainly on established classical theories, their development required additional studies due to the complexity of the analyses involved.

Microstrip antenna on a circular cylindrical substrate with a dielectric cover

The dyadic Greens function formalism and the method of moments were used to analyze a microstrip patch on a circular cylindrical substrate with a dielectric cover. The patch is fed on the side by means of a microstripline running parallel to the cylinder axis. The results showed a strong influence of the cover on the resonant frequency of the antenna.<<ETX>>

Microstrip antenna on a spherical surface

A cavity model with magnetic sidewalls is used for the analysis of a microstrip antenna on a spherical surface. Expressions for the fields in the cavity and for the calculation of the resonant frequency are obtained for each of the operating modes. The input impedance for the cavity fed by a coaxial line through its ground conducting spherical surface is obtained using a procedure similar to that presented by K.M. Luk et al. (1989). The fields radiated by the antenna are obtained by using dyadic Greens functions, and by replacing the cavity by its equivalent magnetic current existing at the side wall of the cavity. Numerical results are presented.<<ETX>>

Dispersion in finlines on semiconductor and the S-parameters of a step discontinuity

The Transverse Transmission Line method is used for the characterization of bilateral and unilateral finlines on a semiconductor substrate and in conjunction with the modal method, for the calculation of the scattering parameters due to a step discontinuity on a unilateral finline with a lossless dielectric substrate.Numerical results of the effective dielectric constant, attenuation constant and characteristic impedance for the bilateral and unilateral finlines on semiconductor substrates, and results of scattering parameters of a step discontinuity for unilateral finline, are presented.