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Cassegrain antenna

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


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Patent
15 Aug 1983
TL;DR: In this article, a rod structure coupled with a support head is used to measure the position of the feed horn of a parabolic reflector antenna relative to the satellite reflecting dish of the antenna.
Abstract: A compact, easily manipulable measuring device is provided, particularly useful for properly positioning the feed horn of a parabolic reflector antenna, or the like, relative to the satellite reflecting dish of the antenna. When installing or maintaining an antenna, it is important for optimum signal reception to position the feed horn at or near the focal point of the satellite dish. Such feed horns typically present a central axis, which if aligned with the center point of the satellite dish approximately positions the feed horn at the focal point of the satellite dish. The device of the present invention presents a telescopic rod structure coupled to a support head. The support head presents structure for attachment to the feed horn such that the rod structure preferably lies along the feed horn central axis. With the rod structure extended to a position adjacent the satellite dish, it is readily apparent whether the feed horn central axis is aligned with the satellite dish center point or if adjustment of the feed horn is necessary.

8 citations

Journal ArticleDOI
J. Shen1, N. Brice
TL;DR: In this paper, a method of obtaining the phase taper across the aperture (and hence the near-field on-axis and backscatter gains versus range) given a knowledge of the far-field ON-axis gain versus frequency, and the amplitude of the illumination over the aperture is suggested.
Abstract: In the near field of the Arecibo spherical antenna radar system, i.e., at ranges less than about 260 km, the gain is a function of range and a knowledge of gain is necessary for deducing electron-density information from the power backscattered from the ionosphere. A method of obtaining the phase taper across the aperture (and hence the near-field on-axis and backscatter gains versus range), given a knowledge of the far-field on-axis gain versus frequency, and the amplitude of the illumination over the aperture is suggested. Our studies show that measurements of on-axis far-field gain over a bandwidth of \pm7 MHz are adequate to give an accurate indication of on-axis gain versus range in the near field, while a \pm15 MHz frequency spread is needed to give accurate information on the backscatter gain versus range. The near-field correction for the antenna has also been estimated from measurements made on a model of the new line feed. Confidence in the validity of this approach has been obtained by comparing the measured far-field on-axis gain versus frequency with that calculated using the data from the model feed.

8 citations

Patent
12 Jun 1980
TL;DR: A radar antenna of the Cassegrain type consists of a paraboloidal principal reflector confronting a hyperboloidal or flat auxiliary reflector of smaller radius directing linearly polarized radiation from a source on their common axis toward the principal reflecting node along lines passing through the focal point thereof to produce an axially extending outgoing beam whose central part is intercepted by the auxiliary reflecting node.
Abstract: A radar antenna of the Cassegrain type comprises a paraboloidal principal reflector confronting a hyperboloidal or flat auxiliary reflector of smaller radius directing linearly polarized radiation from a source on their common axis toward the principal reflector along lines passing through the focal point thereof to produce an axially extending outgoing beam whose central part is intercepted by the auxiliary reflector The latter consists of an array of linear conductors generally parallel to the direction of polarization while the principal reflector is formed by another conductor array generally inclined at 45° to that direction, the latter array being backed by a solid mirror separated therefrom by a distance smaller than a quarter wavelength at the midfrequency of the emitted radiation The composite wave leaving the principal reflector has an elliptical polarization which it retains in an annular portion of the outgoing beam bypassing the auxiliary reflector; only a linearly polarized component of that wave rotated through 90° from the original direction of polarization, however, passes the array of the auxiliary reflector in the central beam portion intercepted thereby

8 citations

21 Jun 2011
TL;DR: In this article, a dual-frequency shared aperture Ka/W-band antenna design was proposed for wide-swath imaging via electronic scanning at Ka-band and is specifically applicable to NASA's Aerosol, Cloud and Ecosystems (ACE) mission.
Abstract: This paper describes a novel dual-frequency shared aperture Ka/W-band antenna design that enables wide-swath Imaging via electronic scanning at Ka-band and Is specifically applicable to NASA's Aerosol, Cloud and Ecosystems (ACE) mission. The innovative antenna design minimizes size and weight via use of a shared aperture and builds upon NASA's investments in large-aperture reflectors and high technology-readiness-level (TRL) W-band radar architectures. The antenna is comprised of a primary cylindrical reflector/reflectarray surface illuminated by a fixed W-band feed and a Ka-band Active Electronically Scanned Array (AESA) line feed. The reflectarray surface provides beam focusing at W-band, but is transparent at Ka-band.

8 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present modeling strategies to determine the operating characteristics of a heterodyne phase-conjugate retrodirective Van Atta (1959) array in the presence of a plane reflector.
Abstract: This paper presents modeling strategies to determine the operating characteristics of a heterodyne phase-conjugate retrodirective Van Atta (1959) array in the presence of a plane reflector. The models used are based on physical and geometrical optics principles. Predictions of the operating characteristics of the array due to the close proximity of a plane metallic reflector are compared with experimental measurements. It is shown that provided the reflector is positioned at a distance greater than 1.25 times the separation distance between the transmitter and the retrodirective array its effect on the performance of the retrodirective array appears to be negligible.

8 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202318
202267
202111
202018
201920
201824