Cassegrain antenna

About: Cassegrain antenna is a research topic. Over the lifetime, 3207 publications have been published within this topic receiving 28278 citations.

In-band scattering of dipole array with edge loaded rectangular reflector

Abstract: The metallic reflector forms an important part of a practical dipole array. To study the contribution of the reflector edges to the overall scattering cross section, the edges of the reflector are loaded with resistance, and the back-scattering cross sections are compared to that of an array without edge-loading. Some preliminary results will be shown. Further investigation is in progress.

Scanning antenna having a spherical main reflector with moveable subreflector

Abstract: An antenna having a large spherical reflector and a small reflector, wherein the main lobe may be oriented with respect to the large spherical reflector by virtue of the displacement of the small reflector, these displacements being rotations around the center of curvature of the large reflector, and the waves irradiating the small reflector being spherical around the same center, the beam formed by these waves shifting with the displacement of the small reflector.

Mushroom surface cloaks for making struts invisible

Abstract: There are many situations where electromagnetic waves are obstructed by some mechanical structure. If the structure is part of or close to an antenna, the obstruction may represent aperture blockage, causing increased sidelobes and reduced gain. The blocking cylinders can be struts supporting the subreflector in a Cassegrain antenna or the feed in a prime-focus paraboloid. The increased sidelobes and reduced gain for these cases are previously studied in detail in several articles, and some simple analytical expressions and design curves are given in (Kildal et al., 1988). The above mentioned blockage effects are a result of the forward scattered field. This is often characterized in terms of an induced field ratio (IFR). However, the blockage losses and sidelobes caused by forward scattering are proportional to the product of the IFR and the physical width (Kildal et al., 1988). Therefore, the paper (Kildal et al., 1996) chose to characterize the forward scattering in terms of this product, being referred to as the equivalent blockage width or simply the blockage width. Thereby, it is easier to compare struts of different widths and types with respect to their electrical performance and mechanical strength. For opaque objects the blockage width becomes at high frequency equal to the physical width. The blockage width becomes by the definition a complex value, where both the real part and the absolute value are representative for characterizing invisibility. We here choose the absolute value only, to save space. The equivalent blockage width is readily computed by considering a plane wave incident on an infinitely long strut, which is a two-dimensional scattering problem. In this paper we treat for simplicity only normally incident plane waves.

A new method of analysis of the near and far fields of paraboloidal reflectors

Abstract: An analytical technique for predicting accurately the near (electric and magnetic) fields as well as the far fields of a reflector antenna with a pencil beam is presented. The technique proposed involves the near-field geometrical theory of diffraction (GTD) analysis of reflector antennas developed earlier and spherical vector mode functions. The proposed technique does not place any restriction on the range of polar angles or radial distances of the observation point. It is demonstrated that the technique proposed can predict the fields radiated by the reflector with greater accuracy by comparing the calculated results with the available measured results. A few important applications of the analysis proposed are also highlighted.

Radar level gauge system with multi band patch antenna array arrangement

Abstract: A radar level gauge system ( 1 ) having an antenna arrangement ( 3 ) adapted to emit microwaves towards a surface ( 7 ) of the product ( 6 ) and to receive microwaves reflected from the surface ( 7 ) The antenna arrangement ( 3 ) includes a reflector ( 8 ) and a multi band patch antenna array ( 9 ) arranged at a distance from the reflector ( 8 ) and adapted to emit electromagnetic waves to be reflected by the reflector towards the surface ( 6 ). The array ( 9 ) has first and second groups of radiator elements ( 19 ) adapted to emit electromagnetic radiation with first and second radiation footprints ( 14, 15 ), wherein the second radiation footprint ( 15 ) is substantially equal to the first radiation footprint ( 14 ), and wherein the reflector ( 8 ) has a size corresponding to the first and second radiation footprints ( 14, 15 ). According to the present invention, the reflector will be adapted to receive most of the radiation in the first and second radiation footprints. This results in an optimized antenna arrangement, where the amount of radiation energy emitted without reaching the reflector is reduced, while at the same time the full reflector size is used for both frequency bands.