Showing papers on "Cassegrain antenna published in 2006"

Satellite ground station antenna with wide field of view and nulling pattern using surface waveguide antennas

Abstract: The present invention is applicable to satellite ground station antennas having a wide field of view in comparison to the satellites with which the antenna connects One embodiment includes a parabolic reflector having a size that corresponds to a beam with an angular half-width larger than the spacing between neighboring interfering satellites It also has a feed comprising at least two dielectric rod-based surface waveguides coupled to the parabolic reflector configured to have a high sensitivity for a target satellite within the angular half-width of the reflector beam and a low sensitivity for neighboring interfering satellites within the angular half-width of the reflector beam

Antenna with Shaped Asymmetric Main Reflector and Subreflector with Asymmetric Waveguide Feed

Abstract: A low-profile antenna system includes a main reflector (102) formed as a shaped main reflector surface that is approximately, but not precisely, parabolic. The main reflector (102) has a main reflector edge configuration (103) that is asymmetric. A feed system (104) for the main reflector includes a subreflector (106) formed as a shaped subreflector surface that is approximately, but not precisely, elliptical. The subreflector has a subreflector edge configuration (107) that is also asymmetric. An RF feed horn (108) associated with the feed system 104 has an aperture profile which also has an asymmetric shape.

A Multiband Antenna for Satellite Communications on the Move

Abstract: The design of a multiband reflector antenna for an on-the-move satellite communications terminal is presented. This antenna was designed to operate with numerous modern and future military communications satellites, which in turn requires the antenna to be capable of operation at multiple frequencies and polarizations while maintaining high aperture efficiency. Several feed antenna concepts were developed to accomplish this task, and are discussed in detail. Multiple working prototypes based on this design have been realized, with excellent performance. Measured data of individual antenna components and the complete assembly is also included

High performance communications and tracking multi-beam antennas

Abstract: Next generation multimedia satellite systems will need to deliver optimal performance while being lighter, smaller and less costly than current systems. Current systems often have four reflector antennas for transmit and another four reflector antennas for receive. A more optimal solution can be obtained by combining transmit and receive on each reflector antenna, thus halving the required number of reflectors and feed chains. Several enabling technologies had to be developed to alleviate, and often eliminate, the resulting RF performance degradation. These technologies include high efficiency feed chains, methods of equalizing transmit and receive beam widths, and RF sensing systems to minimize pointing error. This paper describes these technologies and how they address the needs of the next generation of multimedia satellites.

Multiple Phase Center Performance of Reflector Antennas Using a Dual Mode Horn

Abstract: A new application for reflector antennas is proposed and developed. Using the aperture theory, a phase center on the reflector aperture is determined and shown that, its location is dependent on the field distribution. The proposed concept is, initially, verified by using a symmetric reflector. It is shown that the phase center is located at the aperture geometric center, when the reflector is illuminated symmetrically about its principal planes. Then, a dual mode feed, employing TE11 and TM01 modes, is used for generating different reflector illuminations, and causing displacement of its phase center. The concept is then extended to offset reflectors, and the influence of the reflector geometry on the phase center displacement and other reflector electrical parameters is investigated. Based on the established feed radiation pattern requirements, a feed horn is designed using circular waveguide that can propagate both modes. By modifying the amplitude and phase of the modes in the horn, a controlled asymmetric reflector aperture field is achieved. A prototype feed horn is fabricated and tested for its dual mode radiation patterns. The results are in good agreement with simulations. The reflector phase center properties are then investigated, by using the designed feed. A reflector-feed assembly, with its dual phase center capability, was developed for improving the performance of the ground moving target indicator radars. The concept allows the conversion of a single reflector to two or more reflectors, simply by modifying the mode excitation amplitudes and phases, in the feed alone

A shaped and reconfigurable reflector antenna with sectorial beams for LMDS base station

Abstract: In this communication a reflector antenna is presented as a feasible solution for Local to Multipoint Distribution System base station with a reconfigurable number of sectorial beams. The antenna is an improved version of the hourglass reflector antenna with a shaped profile to obtain a cosecant-squared elevation pattern, and with a feed array which is designed to achieve adequate and reconfigurable beamwidth in the horizontal plane.

Improved feeding structures to enhance the performance of the reflector impulse radiating antenna (IRA)

Abstract: This paper considers the improvement of the feeding structure of the reflector impulse radiating antenna (IRA). Full-wave analysis and measured results of the orthogonal cross-coplanar plate reflector IRA shows that the aperture fields are not uniform. The arm angle is varied as an optimization factor and it is shown that the arm angle of 70deg has the maximum radiation efficiency. The termination load and the arm tapering effects are studied using simulation and measurement results. Furthermore, the effect of radius of circle of symmetry is studied and it is shown that a greater circle provides higher gain. A combination of transverse electromagnetic (TEM) horn antenna and the conical coplanar TEM transmission line is investigated to avoid tiny structure at the focal point and make the connection between the coaxial cable and the feeding arms more convenient. It is shown that a small triangle does not degrade the antenna performance but helps to excite the antenna by a coaxial cable. Finally a combination of the Vivaldi antenna and the coplanar transmission line is introduced to improve the antenna performance. The simulation results for the new antenna show that the antenna efficiency is improved to 45% at the frequency band between 2 GHz to 6 GHz in comparison to the 20.9% for the traditional design and 29.7% for the tapered design. The calculated far-field results of all these antennas are used to radiate a 0.5 ns impulse. The radiated impulse from the Vivaldi fed reflector IRA is 3.55, 2.41, and 2.12 dB higher than the same radiated impulses from the reflector IRA fed by a 45deg traditional feeding arms, 70deg traditional feeding arms, and 70deg tapered feeding arms, respectively

Shaped single-feed-per-beam multibeam reflector antenna

Abstract: Current Ka-band multibeam satellite antenna systems often use one feed per beam, but involve a high number of reflector antennas (four for transmit and four for receive) to realise both acceptable crossover levels and spillover losses (Rao, 1999). Several developments go on to reduce the number of reflectors to one for transmit and one for receive at the cost of much complexity in the feed array and beamforming. Orthogonal efforts aim at developing antennas that both receive and transmit. Here we present a new concept (patent pending) where a shaped reflector reduces both the number of feeds per beam and the number of reflectors to one (with separate receive and transmit antennas). The price paid is an oversizing of the reflector making the reflector area comparable to the total area of the conventional four-reflector solution.

Antenna beam controlling system for cellular communication

Abstract: An antenna beam controlling system (ABCS) for use in cellular communication systems. The ABCS allows the antenna's horizontal beam direction and horizontal beam width to be remotely adjusted for optimum reception and transmission. The ABCS, in its basic design, is comprised of at least one antenna reflector that incorporates a reflecting disk for receiving and transmitting RF signals, an antenna rotating assembly, and an electronic controller. All the elements of the ABCS are housed within an antenna enclosure, such as a radome, which is maintained in an environmentally shielded condition by a top and bottom cover. The electronic controller is designed to remotely activate the ABCS and to control and optimize the position of the antenna reflector.

Thin Film Antenna Development and Optimization

Abstract: The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) and SRS Technologies (SRS) are collaborating on research and development of lightweight thin-film adaptive antennas. On-axis, off-set, and Cassegrain antennas, from 0.3m to 4m in aperture, are currently being designed, fabricated, and radio frequency (RF) characterized via range testing. The designs address requirements for space based systems as well as inflatable terrestrial radome antennas. Fixed, deployable, and adaptive test structures are being developed to support the antennas during testing and future operations. RF characterizations of off-set and on-axis antennas have been performed in the NASA GRC Far Field and Near Field facilities at frequencies from X-band to Ka-band. Thus far, frequencies through Ku-band have indicated excellent antenna performance. Kaband test results indicate that improved antenna surface shape accuracy (sub-millimeter values) is required for efficient operation. Thus, shape optimization, tooling technology, fabrication processes, and active shape control techniques are being developed to enable Kaband operations. SRS has developed and demonstrated thin film antenna shape control via a 5m aperture electro-statically controlled thin film. Recently, SRS and NASA collaborated with Georgia Tech to validate an adaptive beam forming algorithm that could enable a network of lower cost thin film antenna system clusters to replace the large costly antenna systems currently in use. In 2006, SRS and NASA will assemble and RF characterize a 2.4m thin film Cassegrain antenna system that could enable the use of large aperture satellitebased antennas with feed components that are integrated with the satellite bus. All of this successful lightweight thin-film adaptive antenna research and development has the potential to enhance current RF communications capabilities and enable many future RF requirements that need efficiently packaged deployable antennas with large apertures.

On the optimal dimensions of helical antenna with truncated-cone reflector

Abstract: This paper presents optimization of a helical antenna with a truncated-cone reflector. We have found that the dimensions of the truncated-cone reflector and the dimensions of the helical antenna need to be optimized simultaneously to obtain the optimal design. Furthermore, we have found that the truncated-cone reflector can significantly increase the gain of the helical antenna compared to a circular or a square flat reflector. A set of diagrams is made to enable simple design of helical antennas with truncated-cone reflectors. Finally, the results are experimentally verified.

Millimeter-wave reflector antenna system and methods for communicating using millimeter-wave signals

Abstract: Embodiments of millimeter-wave chip-array reflector antenna system are generally described herein. Other embodiments may be described and claimed. In some embodiments, the millimeter-wave chip-array reflector antenna system includes a millimeter-wave reflector to shape and reflect an incident antenna beam and a chip-array antenna comprising an array of antenna elements to direct the incident antenna beam at the surface of the reflector to provide a reflected antenna beam.

Variable beam controlling antenna for a mobile communication base station

Abstract: A variable beam controlling antenna for a mobile communication base station having at least two radiator portions that are arranged vertically, with each portion having a reflector with at least one radiator installed therein. At least one force generator provides rotational force when applied on external control signal, and a force transfer portion transfers the rotational force generated from the force generator to at least one reflector, thus rotating the at least one reflector. The variable beam controlling antenna can be fabricated at a low cost and allows for easy automatic optimization, which is required for a mobile communication wireless network since it is configured to be a one-column antenna capable of controlling a horizontal beam width. Although conventionally many kinds of antennas with different beam widths are needed for base station sectors, the single antenna can easily change its beam width.

Reconfigurable payload using non-focused reflector antenna for hieo and geo satellites

Abstract: An antenna system for generating and configuring at least one defocused beam is provided. The antenna system includes a reflector having a focal plane and a non-parabolic curvature for forming the at least one defocused beam, and a plurality of feed antennas that illuminate the reflector. Each feed antenna is disposed in the focal plane of the reflector. The antenna system further includes at least one incoming signal dividing network that divides at least one incoming signal into a plurality of sub-signals, each corresponding to one of the feed antenna; a plurality of variable phase shifters, each receiving one of the sub- signals from the incoming signal dividing network and phase shifting the sub-signal to generate a corresponding phase-shifted sub-signal, and a plurality of fixed-amplitude amplifiers, at least one corresponding to each of the feed antennas. The at least one amplifier for each feed antenna amplifies the corresponding phase-shifted sub-signal to generate an amplified phase-shifted sub-signal which is provided to the corresponding feed antenna.

Optimum Design for Optical Antenna of Space Laser Communication System

Abstract: A new aspheric surface pre-collimation lenses system for the optical antenna of space laser communication has been optimum designed by optical design software CODE-V. Meanwhile, a Cassegrain antenna with aspheric surface has been designed. By the use of Visual C++, an optical system design software has been set up to analyze optical antenna for the space laser communication system, and some simulation results have been obtained.

STUB loaded microstrip reflect array

Abstract: A stubloaded reflectarray antenna, which combines the features of conventional parabolic reflector and planar microstrip patch array, is presented Equiphase distribution at the aperture of the reflectarray is realized by adding stubs of appropriate lengths at each element A reflectarray of 10×10 elements designed at 10 GHz exhibiting a gain of 225 dB and first side lobe level of -124 dB is presented MATLAB program has been used in the design of stub loaded reflectarray

Test and Analysis of an Inflatable Parabolic Dish Antenna

Abstract: NASA is developing ultra-lightweight structures technology for large communication antennas for application to space missions. With these goals in mind, SRS Technologies has been funded by NASA Glenn Research Center (GRC) to undertake the development of a subscale ultra-thin membrane inflatable antenna for deep-space applications. One of the research goals is to develop approaches for prediction of the radio frequency and structural characteristics of inflatable and rigidizable membrane antenna structures. GRC has teamed with NASA Langley Research Center (LaRC) to evaluate inflatable and rigidizable antenna concepts for potential space missions. GRC has completed tests to evaluate RF performance, while LaRC completed structural tests and analysis to evaluate the static shape and structural dynamic responses of a laboratory model of a 0.3 meter antenna. This paper presents the details of the tests and analysis completed to evaluate the radio frequency and structural characteristics of the antenna.

Radio communication antenna fitted with a radome and method of assembling this kind of radio communication antenna fitted with a radome

Abstract: The present invention concerns a radio communication antenna comprising a reflector fitted to a first opening of a cylindrical lateral screen and a radome formed by a flexible material covering a second opening of this lateral screen so as to have a protective surface facing the reflector According to the invention, this kind of antenna is characterized in that the protective surface is curved by the mechanical action of a deformation element of the antenna coming into contact with this protective surface

Gimbaled dragonian antenna

Abstract: In one embodiment, a gimbaled reflector antenna is provided that includes: a Dragonian antenna having a sub-reflector and a main reflector; a feed; a third reflector adapted to reflect a beam from the feed to the sub reflector; an azimuth gimbal adapted to rotate the Dragonian antenna with respect to the third reflector; and an elevation gimbal adapted to rotate the flat reflector with respect to the feed.

Analysis of radiation patterns and feed illumination of the reflector antenna using the physical and geometrical optics

Abstract: Reflector antennas are characterized by very high gains (30 dB and higher) and narrow main beams. They are widely used in satellite and line-of-sight microwave communications as well as in radar. Reflector antennas operate on principles known long ago from the theory of geometrical optics. The first reflector system was made by Hertz back in 1888 (a cylindrical reflector fed by a dipole). The radiation fields from aperture antennas, such as slots, open-ended waveguides, horns, reflector and lens antennas, are determined from the knowledge of the fields over the aperture of the antenna. In this paper, we analyzed the effects of feeds relating to the parabolic reflectors such as waveguide and horn. We show the variations of the gain in the electric and magnetic planes (E and H) according to the angle of incidence. In our case, we use the origin to be at the focus.

Hybrid Reflector-Array Antenna Concept

Abstract: This paper describes a concept for a hybrid antenna that combines the conventional reflector with an array of printed circuit elements that uses the reflector surface as the array aperture. The objective is to increase the gain and the functionality of the antenna by reusing the conical surface of the reflector as a direct radiating array. The reflector surface can be a single parabolic or a dual reflector surface that uses a combination of conical surfaces. The main reflector surface may contain a conformal printed circuit array with spacing between the conductive elements such that the reflector function is not affected. The gain of the hybrid antenna in a Cassegrain configuration will be a function of the gains of the reflector and the array. The combined gain is reduced by combiner (divider) and blockage losses. The enhanced gain is afforded by magnifying the aperture of one element in the printed array through the reflector system and adding its radiation coherently with that of the direct radiating array. The elements of the printed circuit conformal array are fed with the right phase progression to account for the non-planar surface shape. The paper describes four different arrangements for the hybrid antenna: combined-aperture antennas, dual-band antenna, transmit/receive antenna and dual-beam antenna. Other arrangements can be devised.

Blockage Minimization in Symmetric Dual-Reflector Antennas for Different Edge Taper Values

Abstract: A new scheme in designing symmetric dual-reflector antennas is presented in this work. The main purpose in the design is to suppress blockage without any substantial variations in the configuration of these antennas. Some modifications in the subreflector antenna structure using a lens antenna are made to minimize blockage. A comparison is made between the new design and the conventional Cassegrain using various feed patterns. Simulation results verify the increase in efficiency of the structure.

Sidelobe Level Reduction in Symmetric Dual-Reflector Antennas Using a Small Lens Antenna

Abstract: In many applications, sidelobe level (SLL) reduction of a reflector antenna in a particular direction is needed. In this paper, a novel method to achieve this reduction in a symmetric dual-reflector antenna is presented. An offset lens antenna is attached to the center of the subreflector to direct some rays in a desired direction and yet reduce the SLL effectively. The new designs are compared with the conventional Cassegrain for various feed patterns. Simulation results demonstrate the effective suppression of sidelobe level in the desired directions of the proposed designs.

Recent developments in feed array for Ka-band FAFR antenna

Abstract: The present paper focuses on TCS21 achieved results, which have not been published so far and that are fully consistent with CDR predictions. A synthesis of study main achievements is presented.

Folded reflectarray antennas for shaped beam applications

Abstract: Folded reflectarrays in general consist of a feed, a reflectarray, and a second substrate with printed structures in front of feed and reflectarray, acting as polarizing filter. In this way, compact and possibly lowcost antennas can be designed. This contributions demonstrates the possibilities of this approach for shaped beam antennas using a phase-only design approach and extending the polarizer with additional phase-adjusting elements to allow all types of dual reflector approaches. As examples, two sector antennas, a multibeam antenna, and a multibeam antenna with sector-shaped lobes are presented.

A New Method for Analyzing Large Size Parabolic Cylindrical Reflector Antenna

Abstract: This paper proposes a new method for analyzing the reflector antenna by incorporating the simulating results from EM software into the theoretical computation, and the coupling effect between the horns can be considered by this method. To show the accuracy and validity of the proposed method, a parabolic cylindrical reflector antenna with a horn array feed is investigated. Compared with entire simulation by EM software, this method can save the computation time and improve the computational efficiency. It is very proper to analyze the large size reflector antenna

Multi-beam reflector antenna with feeds covered by an EBG structure used as a spatial angular filter

Abstract: In this paper, we present a frequency wide band electronic band gap (EBG) design of a multilayer dielectric structure with defects used as a spatial angular filter to generate a virtual aperture in the reflector focal plane. This structure is placed in front of few small feeds located in the focal plane of a parabolic reflector. The efficiency of the antenna, its gain and its directivity, compared to a parabolic reflector antenna fed by conventional horn feeds, was examined.

Antenna with reduced interference

Abstract: The present invention relates generally to the field of reflector-type antennas based on the offset Gregorian design having a substantially paraboloidal-shaped primary reflector and a substantially ellipsoidal secondary reflector displaced from the optical axis of the primary reflector. The first focus of the secondary reflector is substantially coincident with the focus of the primary reflector and a feed or detector is placed substantially at the second focus of the secondary reflector. A partially open shroud placed between the primary reflector and the secondary reflector is shown to result in reduced ground interference and improved antenna efficiency and sensitivity.

Device for transmitting and/or receiving electromagnetic waves for aerodynes

Abstract: The device has a blade antenna (2) presented above a fuselage (1) of an aerodyne, and a main reflector array (3) disposed horizontally at the base of the blade antenna. A main lighting cone (4) is disposed at the top of the blade antenna for illuminating the reflector array. Two secondary reflector arrays are disposed vertically on both sides of the antenna. Two secondary lighting cones are disposed at the base of the antenna in a plane of the main reflector array for illuminating the secondary reflector arrays.