Cassegrain antenna

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

Offset cylindrical reflector antenna fed by a parallel-plate Luneburg lens for automotive radar applications in millimeter-wave

Abstract: Using a single offset cylindrical parabolic reflector and a parallel-plate Luneburg lens, a novel high-gain and high-efficiency antenna is developed for automotive radar at mm-wave frequencies. Particularly, a pair of small corrugated extensions is added to the lens for a cylindrical wave. Thus, by feeding a cylindrical wave to the reflector, especially the performance in elevation is enhanced, keeping the complete antenna compact. For verification, a prototype antenna for an adaptive cruise control radar at 76.5 GHz is designed and measured. The theoretical results are verified with good agreement.

Possibilities of dimensioning doubly curved reflectors for azimuth-search radar antennas

Abstract: To produce directional antenna patterns having a shaped beam in one plane such as is required, for instance, in the case of rotating-search radar antennas having a vertical radiation pattern of cosecant-squared shape, doubly curved reflectors are used as a rule. Besides the well-known composition of such reflectors from a stack of strips of parabolic shape, the paper delineates possibilities of an assembly from strips of elliptic shape that are also segments of parabolic dishes. With reflectors assembled in this way certain antenna characteristics such as directivity, sidelobe suppression, etc., can be modified and improved, depending on the type of strip configuration proposed. Experimental results gained with two different reflectors (width 12.5\lambda , height 5.6\lambda ) assembled from strips of elliptic shape are discussed. One of the strip configurations devised turns out particularly favorable for small reflectors.

Analysis of dual-reflector antennas with a reflectarray as subreflector

Abstract: In this paper, a modular technique is described for the analysis of dual-reflector antennas using a reflectarray as a subreflector. An antenna configuration based on a sub-reflectarray and a parabolic main reflector provides better bandwidth than a single reflectarray, and has a number of advantages compared with a conventional dual-reflector antenna. Examples include the possibility of beam shaping by adjusting the phase on the sub-reflectarray, and potential capabilities to scan or reconfigure the beam. The modular technique implemented for the antenna analysis combines different methods for the analysis of each part of the antenna. First, the real field generated by the horn is considered as the incident field on each reflectarray element. Second, the reflectarray is analyzed with the same technique as for a single reflectarray, i.e., considering local periodicity and the real angle of incidence of the wave coming from the feed for each periodic cell. Third, the main reflector is analyzed using the Physical Optics (PO) technique, where the current on the reflector surface is calculated by summing the radiation from all the reflectarray elements. Finally, the field is calculated on a rectangular periodic mesh at a projected aperture, and then a time-efficient fast Fourier transform (FFT) algorithm is used to compute the radiation pattern of the antenna. The last step significantly improves the computational efficiency. However, it introduces a phase error, which reduces the accuracy of the radiation patterns for radiation angles far away from the antenna's axis. The phase errors have been evaluated for two integration apertures. It has been demonstrated that accurate patterns are obtained in an angular range of plusmn6deg, which is sufficient for large reflectors. The method of analysis has been validated by comparing the results with simulations obtained from GRASP8. Finally, the theoretical beam-scanning performance of the antenna is analyzed.

The multiple spot beam antenna project “Medusa”

Abstract: This paper describes the design of a multiple spot beam satellite antenna with overlapping beams in Ka-band. It has been designed in the frame of the DLR granted R&D program “Medusa”. We discuss the principle of a multiple feeds per beam (MFB) antenna in comparison to a classical single feed per beam (SFB) antenna. Results for the optimisation of antenna and feed network are given.

Testing of a 1.5-m reflector antenna at 322 GHz in a CATR based on a hologram

Abstract: Hologram-based compact antenna test range (CATR) is a potential method for testing large antennas at submillimeter wavelengths. This paper describes testing of a 1.5-m single offset parabolic reflector antenna with a 3-m-diameter hologram-based CATR. This is the first time such a measurement is carried out at submillimeter wavelengths. The antenna tests were done in a CATR that was specifically designed and constructed for these tests. The measured radiation pattern at the frequency of 322 GHz is presented. The measured pattern corresponds reasonably well to the simulated pattern of the antenna. The effect of the quiet-zone field nonidealities on the measurement results and the reasons for the discrepancies in the measured antenna beam are discussed.