Cassegrain antenna

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

Comparison of spillover loss of offset Gregorian and Cassegrain antennas

Abstract: The author discusses comparison of Gregorian and Cassegrain antennas with respect to spillover loss and selection of subreflector optics. It was shown that the Cassegrain antenna with the bottom arm has spillover noise lower by at least 5 K at elevation angles 30 degrees and lower as compared to the Gregorian antenna with the arm at the top. Also, from the viewpoint of maintenance, accessibility to the receivers, the feeds, and the subreflector is easy with the arm at the bottom, with the telescope stowed at low elevation angles. However, the National Radio Astronomy Observatory has chosen the Gregorian antenna for the following reasons: first, with the arm at the top, the elevation bearings of the telescope need to be located at a lower height from the ground and, hence, the elevation tower is shorter, saving $3 M to $4 M in steel. Secondly, with the Gregorian antenna, the subreflector can stay installed permanently on the arm, even when prime focus feeds are used. The excess spillover noise of the Gregorian antenna can be reduced by about 2 K by resorting to a feed taper of -15 dB. >

Theory and design of reflectors

Abstract: Numerical Methods for Reflector Antennas Classical Reflector Antennas Reflector Antennas for Adaptive Apertures Reflector Shaping Techniques Bifocal Dual Reflector Antennas Advanced Reflector Antennas Reflectarray Antennas

Synthesis of offset dual shaped subreflector antennas for control of Cassegrain aperture distributions

Abstract: Many existing large ground reflector antennas have been designed as Cassegrain systems-i.e., paraboloid/hyperboloid combinations. Other large ground antennas are simply paraboloid designs. Upgrading the gain of these systems to a gain comparable to that obtainable with a dual shaped reflector antenna system has been an important and costly objective of many such ground stations. A potentially economic method for such an antenna upgrade is presented herein. It involves a redesign of only the subreflector portion of a Cassegrain antenna or the introduction of a subreflector feed system for a parabaloid. A pair of offset subreflectors are synthesized which will give a controllable high gain amplitude distribution in the aperture of the large paraboloid. The synthesis method that is used is based on an approximate formulation for an offset dual shaped high gain antenna that was first presented by Galindo-Israel and Mittra in 1977. In that approximate formulation, the geometrical optics (GO) energy was scattered from a subreflector and then from a second large reflector which reflected a uniform phase distribution. In the present offset dual shaped subreflector (DSS) antenna, the second reflection is from a smaller (sub) reflector and it scatters a spherical wave that feeds a hyperboloid or feeds a large paraboloid directly. Excellent results are shown for the approximate synthesis of the DSS.

Dual-band shared aperture reflector/reflectarray antenna: Designs, technologies and demonstrations for nasa's ACE radar

Abstract: NASA's planned Aerosol, Cloud and Ecosystems (ACE) mission will provide RF measurements for studying the role of aerosols on cloud development The space-borne radar requires a fixed-beam at W-band and a wide-swath (>100 km) scanning beam at Ka-band The full scale antenna is comprised of a parabolic cylinder reflector/reflectarray with a fixed W-band feed and a Ka-band Active Electronic Scanning Array (AESA) feed Cassegrain folded optics is employed to reduce the required mass, volume, mechanical complexity and cost An innovative reflectarray design provides a focused low-loss pencil beam at W-band, and is RF transparent at Ka-band The AESA transmit/receive (T/R) modules provide high RF output power and low noise figure Several planar reflector/reflectarray prototypes were designed and fabricated to validate the novel reflectarray element/surface technology and design methodology The measured W/Ka band reflector/reflectarray gains and patterns agree very well with predictions thereby confirming the viability of the full scale design

A planar passive dual band array feed antenna for Ku band satellite communication terminals

Abstract: A planar passive array feed antenna for bidirectional Ku band satellite communication was designed, fabricated and measured. The feed antenna achieved 50 dB isolation between transmit and receive ports across the transmitting band. An on-reflector test was conducted by mounting the array feed with external low noise amplifier and block downconverter (LNB) on a 90 cm dish to verify the feed radiation efficiency and illumination pattern. The measured signal to noise ratio (SNR) with the planar feed including loss in test connectors was within 2 dB of that of a commercial horn feed.