Showing papers on "Cassegrain antenna published in 2008"

Millimeter-Wave Substrate Integrated Waveguide Multibeam Antenna Based on the Parabolic Reflector Principle

Abstract: A novel substrate integrated waveguide (SIW) multibeam antenna based on the parabolic reflector principle is proposed and implemented at 37.5 GHz, which takes the advantages of low loss, low profile, high gain, and mass producible. A prototype of the proposed antenna with seven input ports generating a corresponding number of output beams is fabricated in a standard PCB process. The measurements are in good agreement with the simulations, and the results demonstrate that this type of printed multibeam antenna is a good choice for communications applications where mobility and high gain are simultaneously required.

Enhanced EBG Resonator Antenna as Feed of a Reflector Antenna in the Ka Band

Abstract: Recent studies have shown that a multibeam reflector antenna could be illuminated by a multifeed electromagnetic bandgap (EBG) structure, in order to achieve a high gain multispot coverage with the simple "one feed by beam" concept and only one aperture. This letter deals with the design of a metallic EBG antenna in the Ka band, feeding a side-fed offset cassegrain antenna (SFOCA) for a European multispot coverage. This reflector presents a high focal-length-to-diameter ratio limiting the defocusing effects for multibeam applications. It, therefore, requires focal feeds with a high directivity and a good radiation pattern quality. The well-known drawbacks of an EBG antenna are the narrow radiation bandwidth for high directivities and also the high sidelobes level reducing the reflector antenna efficiency. Consequently, the work presented in this letter consisted in improving the EBG antenna performances by using a more efficient feed. The replacement of the usual microstrip patch by a horn allowed to double the radiation bandwidth while decreasing the sidelobes level (-15 dB) of a 24-dB EBG antenna. A metallic prototype excited by a single horn has been manufactured at 30 GHz, and the measurements agree with the simulation. This device with one feed allows good SFOCA performances, similar to those obtained with a conventional focal feed like a Potter horn.

Automotive radar using a metamaterial lens

Abstract: An example apparatus comprises an electromagnetic source, such as an antenna, a metamaterial lens, and a reflector The antenna is located proximate the metamaterial lens, for example supported by the metamaterial lens, and the antenna is operable to generate radiation when the antenna is energized The reflector is positioned so as to reflect the radiation through the metamaterial lens The reflector may have a generally concave reflective surface, for example having a parabolic or spherical cross-section The metamaterial lens may have an area similar to that of the aperture of the reflector In some examples, the antenna is located proximate a focal point of the reflector, so that a generally parallel beam is obtained after reflection from the reflector

Reply to “Comments on `Design of High Efficiency Circular Horn Feeds for Multibeam Reflector Applications'”

Abstract: The above paper (Chan and Rao, 2008), has been read with considerable interest. We wish to point out that the design, including radiation and wide-bandwidth characteristics, of multiflared high-efficiency horns has already been published in an invention disclosure (Bhattacharyya and Sor, 2004) which has been in the public domain since June 8, 2006. The high-efficiency multiflared horn structure was first designed in 2003 at the company of the first author. Since then, the structure has been used as radiating elements for arrays and as reflector feeds in several communication satellite projects.

Analysis of dual-reflector antennas with a reflectarray as subreflector

Abstract: In this paper, a modular technique is described for the analysis of dual-reflector antennas using a reflectarray as a subreflector. An antenna configuration based on a sub-reflectarray and a parabolic main reflector provides better bandwidth than a single reflectarray, and has a number of advantages compared with a conventional dual-reflector antenna. Examples include the possibility of beam shaping by adjusting the phase on the sub-reflectarray, and potential capabilities to scan or reconfigure the beam. The modular technique implemented for the antenna analysis combines different methods for the analysis of each part of the antenna. First, the real field generated by the horn is considered as the incident field on each reflectarray element. Second, the reflectarray is analyzed with the same technique as for a single reflectarray, i.e., considering local periodicity and the real angle of incidence of the wave coming from the feed for each periodic cell. Third, the main reflector is analyzed using the Physical Optics (PO) technique, where the current on the reflector surface is calculated by summing the radiation from all the reflectarray elements. Finally, the field is calculated on a rectangular periodic mesh at a projected aperture, and then a time-efficient fast Fourier transform (FFT) algorithm is used to compute the radiation pattern of the antenna. The last step significantly improves the computational efficiency. However, it introduces a phase error, which reduces the accuracy of the radiation patterns for radiation angles far away from the antenna's axis. The phase errors have been evaluated for two integration apertures. It has been demonstrated that accurate patterns are obtained in an angular range of plusmn6deg, which is sufficient for large reflectors. The method of analysis has been validated by comparing the results with simulations obtained from GRASP8. Finally, the theoretical beam-scanning performance of the antenna is analyzed.

Application of the SWE-to-PWE antenna diagnostics technique to an offset reflector antenna

Abstract: A new antenna diagnostics technique has been developed for the DTU-ESA Spherical Near-Field Antenna Test Facility, which is operated by the Technical University of Denmark (DTU) for the European Space Agency (ESA). The technique is based on the transformation of the spherical-wave expansion (SWE) of the radiated field, obtained from a spherical near-field measurement, to the plane-wave expansion (PWE). It allows an accurate reconstruction of the field in the extreme near-field region of the antenna under test (AUT), including the aperture field. The fundamental properties of the SWE-to-PWE transformation, as well as the influence of finite measurement accuracy, have been reported previously. We validate here the new antenna diagnostics technique through an experimental investigation of a commercially available offset reflector antenna, where a tilt of the feed horn and surface distortions were intentionally introduced. The effects of these errors were detected inthe antenna's far-field pattern, and the accuracy and ability of the diagnostic technique to subsequently identify them were investigated. Real measurement data were employed for each test case.

A vehicle mounted antenna and methods for transmitting and/or receiving signals

Abstract: An antenna for communicating with a satellite from a moving vehicle. The antenna comprises a transmitter for generating a transmission signal, main and sub reflectors, and a waveguide associated with the transmitter for conducting the transmission signal toward the sub reflector. The sub reflector is configured for redirecting the transmission signal toward the main reflector; the main reflector is configured for projecting the redirected transmission signal as an antenna beam toward the satellite.

Retro-directive ground-terminal antenna for communication with geostationary satellites in slightly inclined orbits

Abstract: A retro-directive antenna for communicating with a geostationary satellite autonomously detects the direction from which a signal is received, and transmits a beam that points back along the same direction. An array feed is used to illuminate a parabolic reflector. Each feed element of the retro-directive antenna is associated with a unique pointing direction of the beam in the far field. As the transmit energy is switched to different feed elements, the far-field beam is scanned, making it possible to track a geostationary satellite in a slightly inclined orbit. This eliminates the need for mechanical tracking and maintains high antenna gain in the direction of the geostationary satellite. The use of a toroidal reflector with multiple linear array feeds spaced in the azimuth direction enables multi-beam operation, allowing multiple geostationary satellites, spaced by up to fifteen beam widths in azimuth, to be tracked simultaneously and independently.

Leaky-wave slot array antenna fed by a dual reflector system

Abstract: A dual offset Gregorian system leaky-wave antenna realized in PCB technology has been presented. An antenna prototype has been manufactured and tested. The measured radiation patterns as a function of the frequency have been presented. A pins-made feed, that uses EBG concepts, PCB extension of the one presented in [4] has been used to efficiently feed the dual reflector system. However it has not been discussed here for the sake of brevity. Good performance of the antenna has been observed. The planar dual reflector system could be used in future planar imaging system applications, to achieve antennas with independent beams in the azimuth and elevation planes, resorting to frequency reuse and multiple focal plane feeds. The scanning of the pointing angle with the frequency is observed. In particular since the final user of these antenna is a radar system whose beam is scanned as a function of the frequency, the frequency squint that was observed in Fig. 3 should not be considered a disadvantage.

Novel Ku Band Fan Beam Reflector Back Array Antenna

Abstract: In this paper, a Ku band fan beam reflector back array antenna is introduced. This is made up of two main parts that are planar array and main reflector. The proposed antenna has dimensions of 103.3×27.5×12 mm 3 including the reflector. This antenna with high gain for incorporating in Ku band radars at 13.4-14 GHz is described. The fan beam radiation patterns with monopolar characteristics i.e., the cross-polarization is at least 10 dB lower than the co-polarization and are obtained in the frequency band of interest. The maximum gain for proposed antenna is 16.6 dBi at 13.75 GHz and the peak gain generally >16 dBi throughout the frequency band of interest.

Design, fabrication and test of parabolic cylinder reflector and horn for increasing the gain of vlasov antenna

Abstract: This paper proposes two methods for increasing the Gain of Vlasov Antenna. The first method, using a Parabolic Cylinder Reflector, results in a 7 dB increase in the Gain. The second method, constructing a Horn on the aperture, increases the Gain by about 5 dB. The results were checked using a prototype antenna and there was a close agreement.

Automatic Satellite Tracking System

Abstract: A satellite tracking system for tracking a synchronous satellite includes a satellite antenna system movably supported on a roof of a vehicle via a roof frame to move between an operation position and a folded position. At the operation position, the satellite antenna system is rotated on the roof frame to adjust a horizontal orientation of a parabolic reflector of the satellite antenna system while the parabolic reflector is pivotally lift at a predetermined inclination angle to align with the satellite. At the folded position, the parabolic reflector is pivotally dropped down until the parabolic reflector faces downwardly to the roof of the vehicle to conceal a signal transmitting device of the satellite antenna system between the parabolic reflector and the roof of the vehicle. Therefore, the satellite antenna system provides a relatively low profile at the folded position when the vehicle travels.

A modified Bow-Tie Antenna for Microwave Imaging Applications

Abstract: Due to the growing demand for traffic communication, the requirement for reconfigurable antennas for future generation of satellites is growing steadily. This article presents designs examples of reconfigurable satellite contour beam reflector antennas via multi-objective evolutionary optimization. One configuration is composed of shaped reflector illuminated by a single feed horn. To explore the concept, we consider the case of a satellite that can be placed in three orbital positions to provide different coverage: Europe, North America and South America. A second example considers a single shaped reflector illuminated by two feed horns to simultaneously provide dual coverage with frequency reuse

Satellite transmission antenna and satellite-based mobile telecommunication station

Abstract: A satellite antenna for transmitting and receiving an electromagnetic signal has at least one parabolic reflector, a source arm, and a high-power amplifier, in which antenna the high-power amplifier includes a traveling wave tube on the source arm and a high-voltage power supply off the source arm and adapted to supply power to the tube. A satellite mobile telecommunications station includes such a satellite antenna and a storage structure into which the antenna is folded and in which the high-voltage power supply sits.

A simplified simultaneous X/Ka-band feed-system design

Abstract: A variation on an existing antenna feed system for use on simultaneous X/Ka-band satellite ground terminals is presented. The modified design retains the important functionality of the existing feed system, using a simplified approach that aims to significantly reduce the weight and the cost of manufacture.

Basic Element for Square Kilometer Array Training (BEST): Evaluation of the Antenna Noise Temperature

Abstract: In this paper, a rigorous procedure for calculating the antenna noise temperature is described, and applied to the antenna of BEST-1 (basic element for SKA training - version 1), which represents one of the SKA (square kilometer array) demonstrators. The SKA will be a new-generation radio telescope, with a collecting area 50 times larger than the area of today's largest radio telescope. BEST is the Italian reduced-scale SKA demonstrator, based on the re-instrumentation of about 8000 m2 of the Northern Cross radio telescope, built with cylindrical parabolic antennas. In order to perform the antenna-temperature analysis, an electromagnetic tool to accurately evaluate the antenna pattern in the whole space surrounding the antenna itself is required. We used the commercial software GRASP8, developed by TICRA, to characterize reflector antennas. The antenna temperature was evaluated using the guideline adopted by the Antenna Task Force of the SKA world consortium. For BEST-1 at 408 MHz, we found an antenna temperature equal to 30 K in the zenith direction and 60 K at the horizon. The numerical results have been verified through several celestial calibration radio sources.

Space Fed Arrays for Overlapping Feed Apertures

Abstract: An overlapping feed concept for a multiple feed per beam (MFB) antenna architecture is considered. As a first realization a space fed array configuration is focused within this paper. A demonstrator model consisting of a primary and a secondary antenna array was manufactured. The measurement results are in good agreement with the simulation results. Although, the characteristics of the farfield pattern are less appropriate for the required performance. Alternative solutions will be investigated in the future.

Ka band Cassegrain monopulse antenna fed by tapered rod antennas

Abstract: A Ka band Cassegrain monopulse antenna has been designed and measured. The tapered rod antennas are used as the feeds of the Cassegrain antenna because their blockage is small and their bandwidths are very wide. The measurements show that the gain of sum pattern is 28 dBi, the sidelobe levels of the sum pattern are less -15 dB, the null depths of the difference pattern are less then -25 dB and the bandwidth of VSWRz<2 is more than 6.5 GHz.

Low cost design & development of conical horn feed for parabolic reflector antenna

Abstract: We have designed the unusual types of feed antenna for parabolic dish that is used for both reception and transmission purpose. This different frequency band performance having horn and helical feed, works for the parabolic reflector antenna. We have worked on frequency band between 4.8 GHz to 5.9 GHz for horn type of feed. Here function of the horn is to produce uniform phase front with a larger aperture than that of the waveguide and hence greater directivity. Parabolic dish antenna is the most commonly and widely used antenna in communication field mainly in satellite and radar communication.

Calibration of Cylindrical Reflector Antennas With Linear Phased Array Feeds

Abstract: The phase of the elements of a phased array feed is optimized to yield a maximum directivity for front fed and offset cylindrical parabolic reflector antennas. Calibration improves the reflector antenna performance, especially for front fed reflectors with larger feeds.

Radar level gauge system with multi band patch antenna array arrangement

Abstract: A radar level gauge system ( 1 ) having an antenna arrangement ( 3 ) adapted to emit microwaves towards a surface ( 7 ) of the product ( 6 ) and to receive microwaves reflected from the surface ( 7 ) The antenna arrangement ( 3 ) includes a reflector ( 8 ) and a multi band patch antenna array ( 9 ) arranged at a distance from the reflector ( 8 ) and adapted to emit electromagnetic waves to be reflected by the reflector towards the surface ( 6 ). The array ( 9 ) has first and second groups of radiator elements ( 19 ) adapted to emit electromagnetic radiation with first and second radiation footprints ( 14, 15 ), wherein the second radiation footprint ( 15 ) is substantially equal to the first radiation footprint ( 14 ), and wherein the reflector ( 8 ) has a size corresponding to the first and second radiation footprints ( 14, 15 ). According to the present invention, the reflector will be adapted to receive most of the radiation in the first and second radiation footprints. This results in an optimized antenna arrangement, where the amount of radiation energy emitted without reaching the reflector is reduced, while at the same time the full reflector size is used for both frequency bands.

A Sparse Antenna Array with offset Parabolic Cylinder Reflector at Millimeter Wave Band

Abstract: In order to meet the spatial resolution requirement of passive microwave remote sensing from space, aperture synthesis radiometer is used. An antenna array is an important part in synthetic aperture radiometer. A Sparse Antenna Array with Parabolic Cylinder Reflector at Millimeter Wave Band is presented in this paper. The overall requirements for antenna array are listed, followed by design and characterization of the entire antenna array architecture and each part of it including offset reflector geometry, sparse feed array and support structures. The theoretical computation and measured results of electrical parameters of the antenna array are also summarized.

Far field millimeter-wave imaging via optical upconversion

Abstract: Millimeter-wave imaging has the unique potential to penetrate through poor weather and atmospheric conditions and create a high-resolution image. In pursuit of this goal, we have implemented a far-field imaging system that is based on optical upconversion techniques. Our imaging system is passive, in which all native blackbody radiation that is emitted from the object being scanned is detected by a Cassegrain antenna on a rotating gimbal mount. The signal received by the Cassegrain is passed to an optical modulator which transfers the radiation onto sidebands of a near-infrared optical carrier frequency. The signal is then passed to a low-frequency photodetector that converts remaining sideband energy to a photocurrent. Even though optical upconversion can produce loss, our system demonstrates low noise equivalent powers (NEP) due to the low-noise of the photodetection process. Herein, we present our experimental results and images obtained by using the far-field scanning system, which was assembled with commercially available components. In addition, we detail efforts to increase the resolution of the image and to compact the imaging system as a whole.

Integrated ODU controller for antenna pointing

Abstract: A method and system for aligning an antenna reflector with satellites in a satellite configuration. A method in accordance with the present invention comprises pointing the reflector to a position along an orbital arc used in the satellite configuration, commanding a Single Wire Multiswitch circuits which is coupled to the reflector of the antenna to output a signal from at least one satellite at the orbital slot, and adjusting the reflector to maximize reception of the signal from the orbital slot.

Solar parabolic trough mirror/receiver alignment

Abstract: The alignment of a parabolic trough reflector and its receiver pipe in a solar thermal field for collecting sunlight energy can be verified by acquiring an aerial image of the parabolic trough reflector from above the thermal field while passing through the sun-receiver-vertices plane of the parabolic trough reflector. By analyzing the aerial image to determine whether any reflection of the sun is visible in the parabolic trough reflector in the aerial image, one can determine whether the parabolic trough reflector and its receiver pipe is properly aligned. If a reflection of the sun is visible in the parabolic trough reflector in the aerial image, the parabolic trough reflector and its receiver pipe are out of alignment and require an adjustment.

Design of a Prime-Focus Feed with Backward Radiation

Abstract: This paper describes the design of a highly effective parabolic dish antenna primary feed based on backward radiation. This assembly, comprising a dielectric lens and reflecting plate, supports both linear and circular polarization and may be directly attached to a circular waveguide. The current design is intended to work in the 10 GHz band with the specified parabolic dish antenna.

Versatile wideband phased array fed reflector antenna system and method for varying antenna system beamwidth

Abstract: An antenna system includes a reflector having a focal point, and a phased array having feed elements. Each feed element is disposed a same distance from the focal point of the reflector. A method for varying the beamwidth of an antenna system includes providing the antenna system with a reflector having a focal point and feed elements disposed a same distance from the focal point. The feed elements includes one or more inner feed elements and one or more outer feed elements. The method further includes adjusting relative amplitudes of the inner feed elements and the outer feed elements to adjust the beamwidth of the antenna system. An antenna system includes a parabolic reflector having a focal point, and a phased array having one or more inner feed elements and one or more outer feed elements. Each of the feed elements is disposed a same distance in wavelengths from the focal point, and is oriented towards the focal point.

Design Method for a Low-Profile Dual-Shaped Reflector Antenna with an Elliptical Aperture by the Suppression of Undesired Scattering

Abstract: A design method is proposed for a low-profile dual-shaped reflector antenna for the mobile satellite communications. The antenna is required to be low-profile because of mount restrictions. However, reduction of its height generally causes degradation of antenna performance. Firstly, an initial low-profile reflector antenna with an elliptical aperture is designed by using Geometrical Optics (GO) shaping. Then a Physical Optics (PO) shaping technique is applied to optimize the gain and sidelobes including mitigation of undesired scattering. The developed design method provides highly accurate design procedure for electrically small reflector antennas. Fabrication and measurement of a prototype antenna support the theory.

Circularly polarized loop reflector antenna and associated methods

Abstract: The antenna may include a planar reflector having a plurality of loop electrical conductors defining an array of parasitically drivable antenna elements, and a circularly polarized antenna feed spaced from the planar reflector to parasitically drive the array of parasitically drivable antenna elements and impart a traveling wave current distribution therein The antenna may have properties that are hybrid between parabolic reflectors and driven arrays, providing a relatively compact circularly polarized antenna capable of having low wind load Closed circuit or loop elements may provide increased gain over antennas using dipole turnstile reflector elements

Measurement and Evaluation of Submillimeter-Wave Antenna Quasioptical Feed System by a Phase-Retrieval Method in the 640-GHz Band

Abstract: A phase-retrieval method is applied to the quasioptical feed system of the offset Cassegrain antenna of the Superconducting Submillimeter-Wave Limb-Emission Sounder (JEM/SMILES) to be aboard the International Space Station for evaluating the beam alignment by estimating the phase pattern from the beam amplitude pattern measurements. As the result, the application of the phase retrieval method is demonstrated to be effective for measuring and evaluating the quasioptical antenna feed system. It is also demonstrated that the far-field radiation pattern of the antenna main reflector can be estimated from the phase-retrieved beam pattern of the feed system.