Cassegrain Antenna : Report

R. V. COLLEGE OF ENGINEERING, BANGALORE DEPARTMENT OF TELECOMMUNICATION ENGINEERING Radiating governing body Report on Cassegrain feeler Under the guidance of Dr K. ShreeLakshmi Submitted by Santosh H. R 1RV09TE047 Kishore B 1RV09TE025 Mayank 1RV09TE030 Kirthi K 1RV09TE024Table of Contents ContentsPage no. 1)Introduction to Cassegrain antenna. 01 2)Geometry of Cassegrain antenna. 02-03 3)Advantages and Drawback of Cassegrain antenna. 04 4)Applications of Cassegrain antenna . 05-06 5)Conclusion. 07 6)References. 08 Introduction The two-reflecting telescope form invented by Nicholas Cassegrain has been rehearsed extensively in optical telescopes, primarily to turn over a long effective focal length with a satisfactory physical configuration. During the late 1950s, widespread interest developed in the use of this fount of system for microwave frequencies.Axially symmetrical dual-reflector antennas (Cassegrain) classical or forged) be of interest in radio astronomy and in E arth-station antenna technology. The mark of such systems is often restricted by some mechanical constraints, the type of render horn used, and the budget of the project (closely related to the size of the reflectors). pickings into account all of the above, various sets of commentary parameters, representing various solutions, atomic number 18 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 eat up radiator is mounted at or near the surface of a cuplike main(prenominal) reflector and is aimed at a convex subreflector. Both reflectors contract a common focal horizontal surface. Energy from the make unit (a race horn mostly) illuminates the secondary reflector, which reflects it back to the main reflector, which then forms the desired frontwards slam. Cassegrain antenna is a double reflector system which h as many fire features such as high efficiency, low noise temperature performance, and easy availableness to electronic equipment. 1 Photo Cassegrain antenna 02 Geometry The classical Cassegrain geometry, shown in the on a lower floor fig, employs a parabolic contour for the main dish and a increased contour for the sub dish. One of the two foci of the hyperbola is the real focal menses of the system, and is located at the center of the feed the other is a practical(prenominal) 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 focus of the parabola.As a result, all parts reflected from both(prenominal) surfaces, travel equal distances to a plane in front of the antenna. image Geometry of Cassegrain Antenna 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 In terfocal length fs=1. m 03 Advantages 1. Less prone to back disrupt than simple parabolic antenna. 2. Much more compact for a given over f/d ratio. 3. Reduction in spill over and pip-squeak lobe radiation. 4. Ability to place the field in a convenient position. 5. might of the s corporationning and broadening of the beam by moving one of the reflector surfaces. Drawback of Cassegrain antenna Antenna,which whether transmits or receives correct signal or not is our main care and our direction,is an important part in any communication systems.Because of the characteristics of optical maser different from radio,the antenna system of point-to-point laser communication system must(prenominal) be designed strictly. Newton system,Green system and Cassegrain system are authorized commonly in optical antenna systems as field lense which include refraction system,inflection system and refraction-and-inflection system. In this paper,Cassegrain antenna is discussed. However,the potential occupation of sheltering ratio in Cassegrain system leads to a loss of effective office 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 startle 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 GHz band receivers. The main reflector is consisting Of 7 hexagonal modules. The radial rib 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 hybridization Beam Steering organization for Mobile Satellite Communications. A hybrid antenna (HA) with a modified beam direct method is proposed. This antenna has a Cassegrain structure be of two reflectors and a feeder. The parabolic-shaped main reflector is designed for high gain, small-arm the subreflector is rotational and flat. The feeder is a phased array with arbitrary shaped aperture and 20 element antennas.The HA is capable of two-dimensional beam steering by means of two operations rotation of the subreflector and phase train of the feed array. The subreflector is small in size and weight, so it can provide fast beam scanning. Designed to be loaded in vehicles, the HA and can communicate with satellites on the move by tracking the beam control of the feed array. A prototype of the HA is fabricated with aluminum victimization 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 recognize by the subreflector and feed arra y. 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 base on the geometry of the Cassegrain Antennas. We have shown some of the advantages of this antenna over other antennas and the rationale drawback of this antenna.We have shown two major 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 Propagation Magazine, Vol. 40, No. , April 1998 4. Yo ung-Bae Jung, Alexander V. Shishlov, Member, IEEE, and Seong-Ook Park, Member, IEEE, Cassegrain Antenna With Hybrid Beam Steering Scheme for Mobile Satellite Communications, IEEE TRANSACTIONS 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