Sandro R. Zang

Synthesis and rigorous analysis of omnidirectional dual-reflector antennas with shaped main reflector described by local conic sections

This work presents a formulation for shaping the main reflector of an axis-symmetric dual reflector antenna designed to offer an omnidirectional coverage with an arbitrary radiation pattern in the vertical plane. The subreflector is generated by an axis-displaced confocal conic and the main reflector is shaped to achieve a prescribed far-field radiation pattern. The shaping procedure is based on geometrical optics (GO) principles. For validation of the antenna designs, the wotk employs technique by the accurate method of moments technique.

Improvements on the Search Modal Propagation Constants in Lossy Circular Waveguides

In this letter, we review the calculation of the propagation constants in a circular lossy waveguide. We highlighted some improvements in order to find the propagation constants of the guided modes. We present a new characteristic equation that simplifies the application of the winding number technique described in previous publications, and also we discussed some numerical criteria for the application of this technique.

Electromagnetic analysis of wireless telemetry for oil fields

The monitoring and control of the sensors in an oil well casing have been classically performed by electrical cables that connect sensors and actuators in the deep end to the surface station. Classical telemetry techniques have critical aspects in ultra-deep wells, and in some cases its use is impractical. This motivates the investigation of methods for wireless telemetry. In this paper, the electromagnetic characteristics of an oil well casing are analyzed rigorously. Approximations are derived from modal analysis, and the oil well is modeled as a coaxial waveguide heterogeneously filled with lossy matters. The problem of propagation is modeled by the mode matching technique and feasibility of wireless telemetry in oil wells is discussed.

Omnidirectional Dual-Reflector Antennas for Flexible Coverage

This letter discusses the design of an omnidirectional dual-reflector antenna, where the main reflector has a circular generating curve. Under geometrical optics approximations, the subreflector is shaped to produce a uniform phase distribution on a cylindrical aperture placed in front of the main reflector to maximize radiation on the horizon line. Closed-form design equations are presented for the subreflector shape. To provide the scanning of the main beam direction along the vertical plane, the displacement of the subreflector along the symmetric axis is explored. For the analysis of the antennas, method-of-moments technique is employed .

Use of parabolic sections to shape the main reflector of omnidirectional dual-reflector antennas

This work presents a formulation for shaping the main reflector of an axis-symmetric dual reflector antenna designed to offer an omnidirectional coverage with an arbitrary radiation pattern in the vertical plane. The subreflector surface is generated by a hyperbola while the shaped main reflector is generated by a series of local parabolic sections sequentially concatenated. As case studies, two representative axis-displaced Cassegrainian configurations are synthesized to radiate, under GO principles, a cosecant radiation pattern in the elevation plane. For a rigorous antenna analysis, a hybrid technique based on Mode Matching and Method of Moments is employed.

Design of omnidirectional dual reflector antenna: Case of the main reflector with circular generatrix

This work considers the synthesis and analysis of dual reflector antennas designed to radiate omnirectional radiation patterns. The reflectors are circularly symmetric concentric surfaces. Here, the case of the main reflector obtained from a circular generating curve is considered. By applying Geometrical Optics approximations, The main reflector is kept fixed and the subreflector is shaped to produce different tilt angle of the main lobe radiation pattern over the horizon line, considering a uniform phase distribution on a conical aperture placed in front of the main reflector. Depending on the type of ray mapping between the reflectors, two kinds of configurations are identified. By employing the aperture method, the performance of these antennas is predicted and a full wave analysis based on Method of Moments analysis is employed to validate these results.

GO Shaping of Omnidirectional Dual-Reflector Antennas with Arbitrary Main-Beam Direction in Elevation Plane by Connecting Conic Sections

This work discusses an alternative geometrical optics (GO) technique to synthesize omnidirectional dual-reflector antennas with uniform aperture phase distribution together with an arbitrary main-beam direction for the antenna radiation pattern. Sub- and main reflectors are bodies of revolution generated by shaped curves defined by local conic sections consecutively concatenated. The shaping formulation is derived for configurations like ADC (axis-displaced Cassegrain) and ADE (axis-displaced ellipse) omnidirectional antennas. As case studies, two configurations fed by a TEM coaxial horn are designed and analyzed by a hybrid technique based on mode matching and method of moments in order to validate the GO shaping procedure.

Analysis of a coaxial horn antenna using FDTD bidimensional method

In this work an analysis of a coaxial TEM horn with loaded dielectric coupling structure is proposed, which is excited by pulsed signal with short duration. Due to the circularly symmetry of this horn a bi-dimensional analysis with FDTD technique was possible, and the results for the radiation pattern are compared with measurements.

Comparative study of omnidirectional shaped reflector antenna analyses

The implementation of methods for the EM analysis of reflector antennas based on the integration of (surface and edge) induced currents is compared with that of a numerical analysis based on the Method of Moments, chosen as a reference due to its ability of properly addressing the interaction between reflector and feed structures. This is explored herein in connection with the synthesis of shaped reflectors encountered in certain terrestrial systems prescribing omnidirectional coverage. These antennas are usually employed in a LMDS system base station to operate with the distribution of digital TV signals.