Cassegrain Antenna : Report

R. V. COLLEGE OF ENGINEERING, BANGALORE subdivision OF TELECOMMUNICATION ENGINEERING Radiating System Report on Cassegrain forward pass Under the guidance of Dr K. ShreeLakshmi Submitted by Santosh H. R 1RV09TE047 Kishore B 1RV09TE025 Mayank 1RV09TE030 Kirthi K 1RV09TE024Table of limit ContentsPage no. 1)Introduction to Cassegrain aerial. 01 2)Geometry of Cassegrain overture. 02-03 3)Advantages and Draw binding of Cassegrain antenna. 04 4)Applications of Cassegrain antenna . 05-06 5) decision. 07 6)References. 08 Introduction The two-reflecting scope trunk invented by Nicholas Cassegrain has been used extensively in optical telescopes, primarily to achieve a long efficacious central length with a convenient physical configuration. During the late 1950s, general interest developed in the use of this type of organization for nuke frequencies.Axially symmetrical dual-reflector antennas (Cassegrain) classical or shaped) are of interest in radio set astronomy and in Earth -station antenna technology. The design of such plans is often cut back by both(prenominal) mechanical constraints, the type of feed horn used, and the compute of the project (closely related to the surface of the reflectors). Taking into account all of the above, non-homogeneous sets of input parameters, representing various solutions, are considered. From these input parameters, the overall geometry of the antenna is derived in closed form. What is a Cassegrain antenna?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 important reflector and is aimed at a convex subreflector. Both reflectors have a common focal point. Energy from the feed unit (a feed horn mostly) illuminates the secondary reflector, which reflects it back to the main(prenominal) reflector, which then forms the desired forward putz. Cassegrain antenna is a image reflector system which has many interesting fea tures such as utmost efficiency, low noise temperature performance, and easy accessibility to electronic equipment. 1 flick Cassegrain antenna 02 Geometry The classical Cassegrain geometry, shown in the below fig, employs a parabolic cast for the main dish and a hyperbolic contour for the sub dish. hotshot of the two foci of the hyperbola is the real number focal point of the system, and is located at the midst of the feed the different is a virtual feed point which is the real focal point of the system, and is located at the center of the feed the other is a virtual focal point which is located at the direction of the parabola.As a result, all fates reflected from both surfaces, travel equal distances to a plane in front of the antenna. Fig Geometry of Cassegrain overture Geometrical parameters for selected Cassegrain antenna Type Cassegrain Focal length fm=1. 5meter Aperture size X Dx=2meter Aperture size Y Dy=2meter Magnification M=5 Interfocal length fs=1. m 03 Advan tages 1. Less prone to back scatter than simple parabolic antenna. 2. much(prenominal) more compact for a given f/d ratio. 3. reducing in spill over and minor lobe radiation. 4. Ability to place the welkin in a convenient position. 5. Capability of the scanning and broadening of the beam by moving one of the reflector surfaces. Drawback of Cassegrain antenna Antenna,which whether transmits or receives redress signal or not is our main care and our direction,is an important part in any communication systems.Because of the characteristics of laser different from radio,the antenna system of point-to-point laser communication system must be designed strictly. northward system,Green system and Cassegrain system are accepted commonly in optical antenna systems as eye socket lens which include refraction system,inflection system and refraction-and-inflection system. In this paper,Cassegrain antenna is discussed. However,the potential problem of sheltering ratio in Cassegrain system lea ds to a loss of effective power of the optical system so called vignette phenomena.The other is related to optical aberration,because Cassegrain antenna sacrifices sight field for perfect image. 04 Applications 1)ASTRO-G/VSOP-2 off-set Cassegrain telescope The VSOP-2 satellite has an offset Cassegrain antenna. The antenna consists of a 9-m mesh-surface paraboloid main reflector, a solid hyperboloid sub-reflector, and three feed horns. The satellite has 8. 0, 22, 43 gigacycle band receivers. The main reflector is consisting Of 7 hexagonal modules. The radial shout structure is newly adopted for the modules to shape a surface with accuracy of 0. mm-rms. And three band feed horns are juxtaposed at the Cassegrain focus. 05 2)Cassegrain Antenna With Hybrid Beam Steering intrigue for Mobile Satellite Communications. A hybrid antenna (HA) with a modified beam steering regularity is proposed. This antenna has a Cassegrain structure composed of two reflectors and a feeder. The parabolic -shaped main reflector is designed for high gain, while the subreflector is rotational and flat. The feeder is a phased array with arbitrary shaped aperture and 20 element antennas.The HA is resourceful of two-dimensional beam steering by means of two operations rotation of the subreflector and phase control of the feed array. The subreflector is small in size and weight, so it can provide rapid beam scanning. Designed to be loaded in vehicles, the HA and can communicate with satellites on the fire by tracking the beam control of the feed array. A range of a function of the HA is fabricated with aluminum using a machining center operated by computerized numerical control. The prototype is operated at Ka-band for TX and K-band for RX with gains of 47 dBi and 44. dBi, respectively, at a steering angle of 0 . The two-dimensional beam steering within +/- 2 degrees with respect to 45 elevation is realized by the subreflector and feed array. each(prenominal) radiation patterns in the beam steering zone meet ITU-R s. 465-5 regulations. 06 Conclusion This report contains the information of what is a Cassegrain Antenna and its design parameters. We learnt of how the parabolic reflector and hyperbolic subreflectors are designed based on the geometry of the Cassegrain Antennas. We have shown some of the advantages of this antenna over other antennas and the principle drawback of this antenna.We have shown two major(ip) applications of this Antenna which deals with the design of Cassegrain telescope and a beam steering scheme for mobile satellite telecommunications. 07 References 1. John D. Kraus,Antennas for All Applications,Mac-Graw Hill Publications,4th edition. 2. Srinivasan Ashwyn,Introduction to Cassegrain antenna 3. Christophe Granet,Designing Axially Symmetric cassegrain or Dual-reflector Antennas from combinations of prescribed geometric antennas,IEEEAntennas and prolongation Magazine, Vol. 40, No. , April 1998 4. Young-Bae Jung, Alexander V. Shishlov, Membe r, IEEE, and Seong-Ook Park, Member, IEEE, Cassegrain Antenna With Hybrid Beam Steering Scheme for Mobile Satellite Communications, IEEE proceeding ON ANTENNAS AND PROPAGATION, VOL. 57, NO. 5, MAY 2009 5. K. KIMURA, H. OGAWA,H. UJIHARA,ASTRO-G/VSOP-2 off-set Cassegrain telescope, 6. Ravi Subrahmanyan, Photogrammetric Measurement of the Gravity Deformation in a Cassegrain Antenna, IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 53, NO. 8, AUGUST 2005 08