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Topic: Cassegrain antenna

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	Parabolic antenna - Wikipedia, the free encyclopedia
		The Parabolic antenna is a high-gain, reflector antenna used for radio, television and data communications, and also for radiolocation (RADAR), on the UHF and SHF frequencies.
		This antenna is typically a low-gain type such as a half-wave dipole or a small waveguide horn.
		In more complex designs, such as the Cassegrain antenna, a sub-reflector is used to direct the energy into the parabolic reflector from a feed antenna located away from the primary focal point.
	en.wikipedia.org /wiki/Dish_antenna (440 words)

	Satellite Receiving Antennas (Site not responding. Last check: 2007-10-18)
		The parabolic antenna's ability to amplify signals is primarily governed by the accuracy of this parabolic curve.
		The feedhorn's illumination of the antenna must be attenuated or tapered to minimize noise contribution from the perimeter of the dish.
		The antenna's efficiency rating is the percentage of signal captured by the parabolic reflector that actually is received by the feedhorn.
	www.mlesat.com /antennas.html (2655 words)

	Antennas
		Antennas are also used in "receive mode" to collect radiation from "free space" and deliver the energy contained in the propagating wave to the feeder and receiver.
		The biconical antenna, and its derivatives, the broad-banded Yagi, the bow-tie antenna and the phantom conical antenna (which doesn't have a complete conical surface, but just conically disposed rod elements), is a good method of broad-banding a dipole type of antenna.
		In a reflector-aperture antenna fed from the front by a sub-reflector and/or a feed, the far field radiation pattern can be calculated from the Fourier Transform of the field distribution across the aperture, accounting as well for phase variations across the illuminated area.
	www.ee.surrey.ac.uk /Personal/D.Jefferies/antennas.html (9048 words)

	Antenna Tutorial on Gain and Beamwidth From ATI Space and Communications Training Courses
		This equation expressed the radiation from an antenna in terms of the power flow per unit area, instead of giving the field strength in volts per meter, and is the foundation of the RF link equation used by satellite communication engineers today.
		For example, an antenna with a diameter of 2 m and an efficiency of 0.55 would have a gain of 8685 at the C-band uplink frequency of 6 GHz and wavelength of 0.050 m.
		The antenna is illuminated by an array of 146 Potter horns.
	www.aticourses.com /antennas_tutorial.htm (4441 words)

	[No title] (Site not responding. Last check: 2007-10-18)
		Antennas in the diameter range 8 m to 15 m with a surface accuracy specification of 25 µm and a pointing requirement of 1/30 th beamwidth at a frequency of 300 GHz have been studied to determine feasibility and cost.
		Also, antenna noise caused by ground reflections from the feedlegs is as much a function of the angle between the feedleg and the reflector axis as it is a function of the blocked area.
		The antenna base sits on the foundation at 3 points, giving a quasi- kinematic support (radially compliant feet accommodate differential thermal expansion between the steel base and the concrete foundation); each antenna and each base are pre-leveled, which allows rapid reconfiguration of the array.
	www.nrao.edu /~pnapier/LSAMMA/finalreport.htm (5381 words)

	Antenna Design and Measurement Facility (Site not responding. Last check: 2007-10-18)
		QuinStar’s near-field antenna measurement system is composed of a state-of-the-art seven-simultaneous-axis scanner housed in an anechoic chamber.
		The antenna under test (AUT) can automatically be rotated 360° along the vertical mounting axis, and 360° along the horizontal mounting axis (typically the E-H plane axis).
		This antenna range includes an Elevation/Azimuth positioner, source/receiver instrumentation and data acquisition subsystem for automated measurement of radiation patterns of most antennas.
	www.quinstar.com /antenna_development_measurement.html (610 words)

	Cassini-Huygens: Spacecraft-Orbiter Engineering Subsystems
		The high-gain antenna is a Cassegrain antenna consisting of a 4-meter (13.1-foot) parabolic primary reflecto, a sub-refractor mounted in front of the focal point of the primary reflector and the fee horn between the two.
		To shield the harmful hot rays of the sun from the spacecraft's instruments during most of the early portion of the long journey to Saturn, the high-gain antenna was positioned toward the sun, functioning as an umbrella.
		Low-gain antennas also have the added bonus to provide omni directional coverage, as opposed to the high-gain antenna, which must be accurately pointed Once Cassini-Huygens was far enough from the Sun, it finally began using the high-gain antenna for communicating with Earth, thus achieving much faster transmission rates.
	saturn.jpl.nasa.gov /spacecraft/subsystems-cassini.cfm (1452 words)

	EMS AnTools Software (Site not responding. Last check: 2007-10-18)
		However, offset reflectors and antennas can be analyzed as long as their components (primary, secondary, feed and subreflector) are consistent with the parent optics parameters defined here.
		For antenna assemblies (prime focus, Cassegrain and Gregorian), measurement data from any or all of the components may be included in the analysis.
		Antenna definitions (optics layout, reflector geometry, measurements, reference points, etc.) may be saved for future reference as project files for future reference and updating.
	www.engr-metr.com /antools.html (1539 words)

	tutorials (Site not responding. Last check: 2007-10-18)
		For wireless communications, EM signals are not sent through a transmission line, and, therefore, antennas are required for the transmission and reception of the signals.
		The most common one is the wire antenna used in radio, television and cellular telephones; and the reflector/horn antenna that can be found in direct broadcast satellite terminals.
		The Cassegrain antenna system is designed to produce extremely low side lobes to minimize the noise temperature.
	ctd.lerc.nasa.gov /5640/Tutorials.html (1305 words)

	Chp 1: Space and Ground Antennas (part 2)
		Photonic antennas (antennas with opto-electronic components) are not an active subject for RandD at European organizations, being primarily of interest to academic researchers.
		Active and passive phased array antennas with microstrip radiating elements (Figure 2.26) constitute one of the busiest areas of antenna research.
		The ANT antenna laboratory includes a standard outdoor range for far-field measurements, a semi-closed range for far-field measurements in a controlled environment over a limited angular range (30 degrees from boresight), and a spherical near field range.
	www.wtec.org /loyola/satcom/c2_s1b.htm (5523 words)

	Cassegrain Antenna
		A Cassegrain telescope consists of primary and secondary reflecting mirrors.
		In telecommunication and radar use, a Cassegrain antenna is an antenna in which the feed radiator is mounted at or near the surface of a concave main reflector and is aimed at a convex subreflector.
		E.G. it is practiced at the antenna of the tracking radar of the SkyGuard, manufactured in the company Oerlikon/Contraves AG.
	www.itnu.de /radargrundlagen/antennen/at35-en.html (434 words)

	Cassegrain Antenna (Site not responding. Last check: 2007-10-18)
		Cassegrain antenna Definition / Cassegrain antenna Research Related Links Please wait...
		In telecommunication, a Cassegrain antenna is an antenna in which the feed radiator is mounted at or near the surface of a...
		Analysis of a Twisting Cassegrain Antenna (Analyse van een Twisting...
	www.telescopes-and-binoculars.info /optics/cassegrain-antenna.html (120 words)

	Chp 2: Space And Ground Antennas
		The size of an antenna is often stated in terms of its "aperture," which can be taken to mean either the physical area of the radiating part of the antenna or the diameter of a circle having this area, depending on context.
		Moving the beam of an antenna in a particular direction is called "scanning." Reflector antennas are usually scanned by mechanically moving the reflector or the feed or both.
		The antenna itself is a 2.4 m reflector fed by an array of helical elements.
	www.wtec.org /loyola/satcom/c2_s1a.htm (3947 words)

	RADIO TELESCOPE
		The antenna is mounted on a five-inch naval gun mount converted specifically for an application in positioning a large parabolic reflector dish.
		Channel A and B: The absolute encoders have 2 channels, which are channels A and B. By implementing a second channel B with the phase position displaced by 90°, it is possible to determine the direction of rotation by evaluating the phase-position of the pulses.
		The reflector antenna is constructed with a main reflector and a subreflector, also known as a Cassegrain Feed Antenna.
	seniord.ee.iastate.edu /SSOL/RT1/rtfinal98.html (7137 words)

	26.5GHz - 140GHz Cassegrain Antenna Series for OEM Market
		Antennas of ECA - XX series are available for frequencies from 26.5GHz to 140GHz with reflector diameters ranging from 100mm to 600mm.
		The antenna feed is a circular waveguide of appropriate diameter with an optional circular-to-rectangular transition.
		Each antenna can be shipped with antenna bracket and radome as standard options.
	www.elva-1.spb.ru /products/microwave/dual_reflect.html (463 words)

	Beam Switching Cylindrical Array Antenna System (Site not responding. Last check: 2007-10-18)
		The antenna functions in conjunction with a multifunction primary phased array radar meant for the guidance of Akash missile.
		The role of IFF array is to supplement an important decision about friend or foe to the primary radar system to take decision about the delivery of the weaponry.
		It is capable of generating interrogate and control radiation patterns in transmission mode and sum and difference pattern in receive mode using monopulse technique.
	www.drdo.com /pub/techfocus/apr2000/Phased%20array%20antenna.htm (177 words)

	U.S. Radio Astronomy Observatories
		Remarks: This antenna is sometimes used as an array element with the 64-m antenna located in Parkes, Australia.
		The 4.6-m antenna is configured for 21 cm (1.42 GHz), 4.829, 6.668, and 11.178 GHz reception.
		The antenna was part of early NASA experiments at 30GHz with the ATS (advanced technology) satellite.
	www7.nationalacademies.org /bpa/US_radio_astronomy_observatories.html (1311 words)

	Debian -- cassbeam
		A Cassegrain antenna is a double reflector system which works on the principle of cassegrain optical telescope.
		A high gain cassegrain reflector antenna in Ku-band has been successfully developed for command transmit application for the missile programme.
		Based on an input text file, it computes several properties of the antenna including gain, zenith system temperature, and the beam, in full polarization.
	packages.debian.org /unstable/science/cassbeam.html (204 words)

	18 - 40 GHz Cassegrain Antenna with Motorised Sub-Reflector (Site not responding. Last check: 2007-10-18)
		18 - 40 GHz Cassegrain Antenna with Motorised Sub-Reflector
		Leominster, UK Although Q-par Angus designs and manufactures a number of standard cassegrain microwave antennas, we have also produced this unusual design with a motorised sub-reflector.
		This antenna is widely used in both military and civilian markets.
	www.q-par.com /pages/18to40_Cassegrain_Ant.htm (94 words)

	Deutsche Welle: Radio Training Centre
		Antenna shall be positioned with line of sight to the satellite.
		Antenna shall be mounted on a proper foundation.
		Efficiency of Antenna is important and depends mainly on surface roughness
	www9.dw-world.de /rtc/infotheque/satellite/sat_broadcast3.html (469 words)

	ALMA MEMO #456 (Site not responding. Last check: 2007-10-18)
		The goal is to make available in one place information which is useful for the analysis of antenna measurements and radio astronomy observations.
		The computations and the derived illustrations are made with the aid of Mathematica and all Mathematica expressions are included at the end of the report.
		This collection of data is an extension of my earlier summary of antenna parameters, issued as and NRAO Electronic Division Internal Report (EDIR), No. 57 of August 1966.
	www.mma.nrao.edu /memos/html-memos/abstracts/abs456.html (154 words)

	Terme (Site not responding. Last check: 2007-10-18)
		An antenna in which the feed radiator is mounted at or near the surface of a concave main reflector and is aimed at a convex secondary reflector slightly inside the focus of the main reflector.
		2: The Cassegrain antenna design is adapted from optical telescope technology and allows the feed radiator to be more easily supported.(TG)
		The antenna principle that utilizes a subreflector at the focal point which reflects energy to or from a feed located at the apex of the main reflector.
	doc-telecom.enst-bretagne.fr /doc-telecom/terme.jsp?2811 (108 words)

	Compact Cassegrain Antenna Design for Collective Thomson Scattering Exeriments on TEXTOR (Site not responding. Last check: 2007-10-18)
		The first stage antenna will be installed in the poloidal plane of the probe, using near back scattering geometry, near perpendicular to the magnetic field.
		The second stage will operate at large angles to the field and a second antenna, implementing a 90° scattering geometry, will be installed.
		In the first system an on-axis smooth rectangular horn is used as feed for a 10cm diameter parabolic mirror with focal length of 5cm.
	flux.aps.org /meetings/YR99/DPP99/abs/S655092.html (212 words)

	Vertex Antennas (Site not responding. Last check: 2007-10-18)
		Model 4.8 KPC Compact Cassegrain antenna feature all metal reflectors which incorporate doubly-contoured, formed panels with matched radials and hub assemblies for easy bolt-together installation with no field alignment required.
		This antenna is designed to become the technical standard for responsible, reliable, and high quality VSAT systems worldwide.
		The VertexRSI lightweight 2.4 M flyaway antenna is designed for worldwide transmit and receive operation in C, X or Ku-Band.
	www.jrsat.com /id75.htm (888 words)

	Virginia Tech Antenna Group (VTAG)
		R. Allnut, T. Pratt, and A. Dissanayake', "A Study in Small Scale Antenna Diversity as a Means of Reducing Effects of Satellite Motion Induced Multipath Fading for Handheld Satellite Communications Systems," Proceedings of International Conference on Antennas and Propagation, vol.
		A. Safaai-Jazi, and J.C. Cardoso, "Radiation Characteristics of a Spherical Helical Antenna," IEE Proc.-Microw.
		Stanislav Licul and William A. Davis, “Unified Frequency and Time-Domain Antenna Modeling and Characterization”, IEEE Transactions on Antennas and Propagation, September 2005.
	lab.ant.ee.vt.edu /publications.html (5803 words)

	Cassegrain (Site not responding. Last check: 2007-10-18)
		antenna has a parabolic reflector that focuses the incoming radiation in satellite communications onto a hyperbolic sub-reflector and thence into the waveguide.
		antenna is that it does not require the receiver electronics to be placed at the focus of the parabola.
		Please contact us if you wish to propose related words or phrases to extend our glossaries.
	www.argospress.com /Resources/satellite/casseg.htm (170 words)

	Cassegrain antenna -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-18)
		Cassegrain antenna -- Facts, Info, and Encyclopedia article
		Note 1: Energy from the feed unit illuminates the secondary reflector, which reflects it back to the main reflector, which then forms the desired forward (Long thick piece of wood or metal or concrete, etc., used in construction) beam.
		Source: from (Click link for more info and facts about Federal Standard 1037C) Federal Standard 1037C
	www.absoluteastronomy.com /encyclopedia/c/ca/cassegrain_antenna.htm (85 words)

	Satcom Resources VertexRSI Model 16.4 THC - 16.4 meter Cassegrain Antenna (Site not responding. Last check: 2007-10-18)
		The VertexRSI Model 16.4THC "Turning Head" antenna is the most receint state-of-the-art antenna design in the industry.
		Tasked with the goal of providing a cost-effective antenna subsystem installation, the design was approached, in part, to minimize field installation time by increasing the level of factory-controlled subassembly.
		This was achieved by precision fabrication tooling and higher level of factory subassemblies.
	satcomresources.com /product.do?mode=11&productId=3718 (179 words)

	· MILLIFLECT · Microwave Antenna Specialists
		Milliflect, The Microwave Antenna Specialists builds a broad array of High Performance and Standard Antennas for line-of-sight applications.
		Our antennas are of quality construction, high efficiency, rugged, long-life antennas field proven since 1972.
		Specially aligned microwave feed support structures for simplified antenna installations.
	www.milliflect.com (72 words)

	MMA Memo #175 (Site not responding. Last check: 2007-10-18)
		Gain Degradation in a Symmetrical Cassegrain Antenna Due to Laterally Offset Feeds
		The maximimum distance off-axis that a feed can be placed in a symmetrical Cassegrain antenna without significant degradation in efficiency is investigated.
		The results place limits on the size and position of receivers at the secondary focus.
	www.mma.nrao.edu /memos/html-memos/abstracts/abs175.html (117 words)

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