Showing papers on "Cassegrain antenna published in 2014"

Enclosure for radio, parabolic dish antenna, and side lobe shields

Abstract: Enclosures for radios, parabolic dish antennas, and side lobe shields are provided herein. A dish antenna includes a parabolic circular reflector bounded by a side lobe shield that extends along a longitudinal axis of the dish antenna in a forward direction forming a front cavity, and a sidewall that extends along the longitudinal axis of the dish antenna in a rearward direction forming a rear cavity.

Imaging antenna systems with compensated optical aberrations based on unshaped surface reflectors

Abstract: An offfset imaging antenna system with compensated optical aberrations comprises a main a paraboloid reflector (4), a first paraboloid sub reflector (6), and a first feeding array (8) as an arrangement of first feed array elements to illuminate or to be illuminated by the first sub reflector. The main reflector (4) and the first sub reflector (6) are confocal by sharing a common focal point. The first feeding array (8) has a curved shape that corresponds to a first equivalent array (12) of magnified image feed elements (14) lying on a plane (16) crossing the main optical centre and perpendicular to the main bore-sight axis, all the first feed array elements (10) being positioned as to provide a planar distribution of the positions of the image feed elements (14) onto the first equivalent array (12) after a second reflection by the main reflector (4) with a central image point coinciding with the main reflector optical centre under a maximum illumination condition.

Surface scattering reflector antenna

Abstract: A surface scattering reflector antenna includes a plurality of adjustable scattering elements and is configured to produce a reflected beam pattern according to the configuration of the adjustable scattering elements.

Wideband Dielectric Lens Antenna With Stable Radiation Patterns Fed by Coherent Array of Connected Leaky Slots

Abstract: A broadband reflector feed is presented, which consists of a dielectric extended hemispherical lens fed by a connected array of leaky-wave slots. The slot elements are coherently combined to generate directive radiation patterns that mostly illuminate the central part of the lens, the most efficient one. The array is capable of producing secondary patterns with almost constant -10 dB beamwitdh over a 3:1 bandwidth. This allows efficient illumination of the reflector over a wide frequency range. Performance is estimated in terms of amplitude taper and phase error losses at the reflector, yielding efficiency of about 80% over the entire 3:1 bandwidth. Although the envisaged applications are in the terahertz (THz) and mm-wave frequency bands, a low-frequency prototype demonstrator has been tested in the 4 to 12 GHz band, for experimental validation of the concept.

Surface scattering antenna array

Abstract: An array of scattering and/or reflector antennas are configured to produce a series of beam patterns, where in some embodiments the scattering antenna and/or the reflector antenna includes complementary metamaterial elements. In some embodiments control circuitry is operably connected to the array to produce an image of an object in the beam pattern.

Multiband Dual-Polarization High-Efficiency Array Feed for Ku/Reverse-Band Satellite Communications

Abstract: A dual-band dual-polarized planar passive phased array feed was designed and simulated, with four highly isolated ports and polarizations. The feed design provides an important feasibility demonstration for the deployment of a satellite transponder that transmits a downlink signal at 17.3-17.8 GHz, referred to as reverse band (RB), in the same orbital slot as an existing Ku-band satellite. The design utilizes a multilayer printed circuit board (PCB) to separate the complex feed distribution networks required for the four-port antenna. Simulation results indicate that the feed receives signals in dual linear polarization at Ku-band and dual circular polarization at RB with isolation between all ports better than 20 dB. With the feed illuminating a reflector antenna, the aperture illumination and radiation efficiencies are approximately 70% and 80%, respectively, for all ports, representing one of the most complex yet efficient reported planar array feed designs in the literature.

Compensation for gravity deformation via subreflector motion of 65 m shaped cassegrain antenna

Abstract: Compensation for degrading electromagnetic performances is one of the most important concerns for engineers involved in the structural design of a large antenna A method is proposed to compensate the degrading electromagnetic performances induced by the main reflector deformation of the large and shaped Cassegrain antenna by adjusting the subreflector position in real time Segmented parabola fitting based on the least squares method of the theoretical discrete data of the main shaped reflector yields a standard group of parabolic torus that is later used to fit the deformed main reflector, with all the parabolic toruses confocal in the fitting The optimised best-fit parameters and the matching between the main reflector and subreflector calculate the adjustment quantity of the subreflector The adjustment quantities, stored in the database of the subreflector, working under various conditions can be called in real time to compensate the gravity deformation of the main reflector The application of the method to a 65 m aperture-reflector antenna was successful, thus, laying a good foundation for its application in engineering practice

A quadraxial feed for ultra-wide bandwidth quadruple-ridged flared horn antennas

Abstract: A quadraxial feed, excited by two orthogonal differential modes, is proposed for ultra wideband quadruple-ridged flared horn (QRFH) antennas that obviates the need for a balun. It is shown that in this configuration the fundamental TE11 mode is most strongly excited over the entire frequency band, while the higher-order modes are significantly suppressed, as compared to the conventional excitation using the ridge-to-coax balun transition. These properties lead to several advantages for QRFH antenna applications which require frequency-invariant beam characteristics, high port isolation and low cross-polarisation level, such as e.g. reflector antenna feeds for future radio telescopes.

A dual-polarized W-band metal patch antenna element for phased array applications

Abstract: This paper describes results of measurements of a 2×2 `unit cell' of dual-polarized metal patch elements intended for electronically scanned array applications. The unit cell is the fundamental building block of a linear array feed to a cylindrical parabolic reflector. The transmit and receive elements are arranged on a triangular grid which provides good isolation between separate transmit and receive modules, obviating the need for circulators. The 2×2 unit cell and associated feed network was implemented in PolyStrata ® technology. Measurements agree very well with simulations in HFSS, with the overall loss of the element and interconnect estimated as 0.5dB at 94 GHz.

A Novel Application of the Active Surface of the Shaped Sardinia Radio Telescope for Primary-Focus Operations

Abstract: The 64-m Sardinia Radio Telescope (SRT) is a shaped dual-reflector antenna designed to optimize secondary-focus operations. A novel application of the SRT active primary reflector aimed at achieving efficient operations also at the primary focus is presented. To this purpose, we show how the panels of the shaped primary mirror can be moved to best fit a parabolic surface. The modified primary reflector permits increasing the maximum frequency for primary-focus operation and also improves low-frequency multifeed capabilities. In fact, our numerical simulations show that at 80 GHz, the aperture efficiency from the primary focus drops only 10% with respect to 300 MHz.

Wideband circularly polarized slotted-patch antenna with a reflector

Abstract: A design for wideband circularly-polarized (CP) antennas with unidirectional radiation is described. The antenna structure is mainly composed of a rectangular slotted patch and a metallic reflector. First, the CP design for the stand-alone slotted patch antenna is investigated, and a 3dB-axial-ratio bandwidth of 53 % is obtained. Then, the metallic reflector is placed at the rear of the slotted patch to generate unidirectional radiation. Experimental results demonstrate that the slotted patch antenna with a reflector has almost the same CP bandwidth as the stand-alone slotted patch antenna, and it has good impedance matching as well as stable radiation patterns across the CP operating frequencies.

Realizing a Flat UWB 2-D Reflector Designed Using Transformation Optics

Abstract: This paper presents the design and experimental validation of a flat ultra-wideband 2-D reflector designed using transformation optics (TO). The flat TO reflector mimics the electromagnetic characteristics of a curved parabolic reflector that is rotated about its apex to reflect the incident wave to a prescribed direction. The TO reflector is true-time-delay (TTD) in nature and it offers a very large bandwidth which is theoretically unconstrained. The proof-of-concept TO reflector design is explored by employing an effective material with an inhomogeneous electric response which is realized by an array of dipoles. We experimentally verify the principle of operation of the reflector over a 67% bandwidth and show that it maintains good radiation characteristics and low beam squint. The design considerations, benefits and drawbacks of the proposed TO reflector are discussed.

A Practical Approach to Locate Offset Reflector Focal Point and Antenna Misalignment Using Vectorial Representation of Far-Field Radiation Patterns

Abstract: A direct and unambiguous approach to determine the focal point of a single offset reflector is presented. The proposed approach makes use of the vectorial form of far-field radiation patterns, both amplitude and phase. The method is based on iteratively defocusing the primary feed laterally and axially. First, mathematical expressions of the offset reflector with a small lateral and axial defocused feed are reviewed. Then, the numerical results are presented. It is shown how the corresponding far-field phase pattern information can be utilized to optimally locate the focal point of an offset parabolic reflector. The method can also be used to place the phase center of an unknown feed on the reflector focal point, and align the reflector on a test tower.

Design and measurement of W-band offset stepped parabolic reflector antennas for airport surface foreign object debris detection radar systems

Abstract: Debris on the airport surface may cause severe damage to aircraft. To detect these obstacles, foreign object debris (FOD) detection systems have been developed recently. By utilizing high-sensibility and weather robustness characteristics, the millimeter-wave radar is an essential sensor device for these systems. This paper discusses an offset parabolic reflector antenna for airport surface FOD detection radar systems. Firstly, the overview of the FOD detection radar systems, which employs a band of between 92 GHz and 100 GHz, is shown. For the azimuth beam scanning antenna, the antenna is required to achieve both a narrow azimuth beamwidth and a wide elevation beamwidth. Secondly, the stepped parabolic reflector is newly designed to obtain an 8 degree elevation -20 dB down power beamwidth. Finally, the designed reflector is fabricated based on chemical wood materials. The measured result shows the 38 dBi gain and the 8.4 degree beamwidth for the elevation plane.

A Compact 118-GHz Radiometer Antenna for the Micro-Sized Microwave Atmospheric Satellite

Abstract: A linear polarized 118-GHz antenna is designed for a radiometer payload hosted aboard a 3U atmospheric CubeSat. The radiometer antenna is a horn-fed offset parabolic reflector. The antenna has a maximum +37 dBi realized gain, 2.4 ° half-power beamwidth, and a minimum 95% beam efficiency within the operational bandwidth. The antenna is compact, meeting the MicroMAS mission requirement for a highly integrated and ultra-compact radiometer. CubeSats present stringent size/volume and weight constraints on overall component design. We present our design, along with simulated and measured results, that meet the size/volume, weight, and electrical requirements for the radiometer antenna and comply with CubeSat standards.

Directional multi-band antenna

Abstract: There is disclosed a directional multi-band antenna comprising: a primary reflector, at least one secondary reflector, a multi-layer dielectric layer selectively reflective or transmissive of incident radiation according to wavelength, the layer being provided at the surface of either the primary or the secondary reflector, an RF unit comprising a collocated sensor and transmitter, an Optical unit comprising a collocated sensor and transmitter, arranged such that the primary reflector is for passing signals between the secondary reflector and the environment, the secondary reflector is firstly for passing signals between the primary reflector and the RF unit, and secondly for passing signals between the primary reflector and the Optical unit and arranged such that the antenna is operable to transmit or receive, RF or Optical signals, along a common beam axis.

Radar antenna system

Abstract: A device is described. The device includes a chip, a reflector, and an antenna. The reflector is disposed on a surface of the chip. The reflector is a metalized layer on the surface of the chip.

Dense Focal Plane Arrays for Pushbroom Satellite Radiometers

Abstract: Performance of a dense focal plane array feeding an offset toroidal reflector antenna system is studied and discussed in the context of a potential application in multi-beam radiometers for ocean surveillance. We present a preliminary design of the array feed for the 5-m diameter antenna at X-band. This array is optimized to realize high antenna beam efficiency (∼ 95%) over a wide scan range (±20°) with very low side-lobe and cross-polarization levels.

Antenna array system for producing dual circular polarization signals utilizing a meandering waveguide

Abstract: An antenna array system for directing and steering an antenna beam is described in accordance with the present invention. The antenna array system may include a feed waveguide having a feed waveguide length, at least two directional couplers in signal communication with the feed waveguide, at least two pairs of planar coupling slots along the feed waveguide length, and at least two horn antennas.

Axially symmetric dual-reflectarray antennas

Abstract: An axially symmetric dual-reflectarray antenna is proposed. A main reflectarray is designed to mimic a paraboloidal main reflector, and a sub-reflectarray is designed to mimic a hyperboloidal or an ellipsoidal sub-reflector. The dual-reflectarray antenna is more compact than the conventional curved dual reflector. The dual-reflectarray antenna is designed at W-band and compared with its equivalent Cassegrain antenna.

High-Performance Dual-Circularly Polarized Reflector Antenna Feed

Abstract: This letter presents a high-performance dualcircularly polar ized feed employing a dielectric -filled circular waveguide. Novel features are incorporated in the proposed feed such as a dielectric rod radiator for high gain and good impedance matching, dual quarter wave chokes for low axial ratio over wide angles and for low back radiation, an integrated septum polarizer, and coaxial -to-waveguide transitions for dual-circularly polarized . The proposed feed shows excellent performance at 5.0-5.2 GHz.

High gain conical beam antenna with large beam-pointing angle by using hemitorus lens-reflector

Abstract: In this paper, a high gain conical beam antenna with large beam-pointing angle has been investigated. Total prototype contains a three section circular waveguide aperture antenna which operates in TM03 mode in order to generate a primary conical beam and a new hemitorus lens-reflector as the secondary large aperture radiator. Through optimized design, the gain of 12 dB and a beam-pointing angle of 50° have been achieved at the central frequency of 35 GHz.

Antenna reflector system

Abstract: A scan range of a steerable antenna is extended using a reflecting surface or surfaces within the scan range. Various implementations may also include lenses, and the reflecting surface, lenses, or both may include meta-materials. The antenna may be steered to interact with the reflecting surface, lenses, or both to reflect the beam in a direction not possible using the antenna alone. The scan range may be extended in azimuth, elevation, or both, and beam pattern, and antenna freespace impedance may be controlled.

Electro-Magnetic Band-Gap feed overlapping apertures for multi-beam antennas on communication satellites

Abstract: An `EBG antenna (Electro-Magnetic Band Gap)' is built with a semi-reflective screen over a set of horns feeding a reflector. A clever application of the partial spreading of the electro-magnetic field in such a structure is to provide `overlapped radiating apertures', which generate `overlapped beams' when feeding a reflector. This is a unique single-antenna solution, fitting with multi-beams missions from satellite which require low gain ripple over a regional coverage, e.g. for high data-rate communication in Ka-band. A prototype has been optimised and built, as a co-operation between Thales Alenia Space France & XLIM/Antenna Lab, supported by space agencies ESA & CNES. Adding a very light meanderline polariser (honeycomb based) transforms the alternated orthogonal linear polarisations into orthogonal circular ones, coping with most recent missions.

Ka-band reflectarray antenna system for SAR applications

Abstract: This paper presents two reflectarray antenna configurations used as receive and transmit antennas for a ku-band Synthetic Aperture Radar system (SAR). The receive antenna is constituted by nine equal single offset reflectarray modules. The transmit antenna is based in two dual offset parabolic reflector antenna with a rectangular reflectarray as main reflector. Both receive and transmit antennas are able to work in two different modes using orthogonal polarizations, the narrow swath mode and wide swath mode.

Improved Cross-Polarization Performance of a Multi-Phase-Center Parabolic Reflector Antenna

Abstract: This letter addresses the cross-polarization properties of electronically controlled multi-phase-center parabolic reflector antennas, illuminated by over-moded primary feeds. Due to the presence of the higher-order modes in the primary feed, the secondary cross-polarization levels deteriorate in the case of symmetric reflector antennas. As for the offset reflectors, the primary multimode feed required to displace the phase-center location may produce a significant crosstalk in the orthogonal polarization. It is shown how one can improve the cross-polarization performances of aforementioned adaptive antennas, which are capable of providing axial beams while their phase-center locations are displaced. The conventional array technique with a simple signal processing is used for the symmetric case, whereas a trimode primary feed is employed for the offset case.

A Corrugated Printed Dipole Antenna With Equal Beamwidths

Abstract: A corrugated printed dipole antenna with equal beamwidths in the principal planes is proposed, designed, and evaluated. Orthogonal stubs are added to the dipole arms to equalize its radiation patterns. They also reduce the size of the dipole arms. The antenna is designed to operate at 3 GHz, and has dimension of 36 × 80 × 1.58 mm3. The -10 dB S 11 bandwidth of the antenna is from 2.75 to 3.62 GHz, i.e., 27.3%. The E- and H-plane radiation patterns of the antenna are nearly equal up to 135 ° from the boresight. To confirm the simulation results, the antenna is fabricated and tested, showing good agreement between simulation and measurement results. Its performance as a feed on a deep reflector, with f/D = 0.25 and D = 45 cm is also studied, where f is the focal length of the reflector and D is its diameter. It provides an enhanced bandwidth of 29.6%, equal E- and H-plane radiation patterns of the reflector, and a gain of 21.4 dBi or an efficiency of 69%. The reflector is only 4.5 λ0 in diameter and would suffer significant blockage losses with conventional waveguide feeds. The proposed feed causes negligible blockage, and provides a respectable efficiency. It is a suitable feed for small symmetric reflectors.

Box-shaped fan-beam antenna

Abstract: The invention provides a box-shaped fan-beam antenna. The box-shaped fan-bean antenna comprises a feed horn, a main cylindrical reflector, an auxiliary cylindrical reflector, an upper cover plate, a lower cover plate, a left baffle and a right baffle. The Cassegrain antenna geometric form is adopted in a bus of the main cylindrical reflector and a bus of the auxiliary cylindrical reflector, the upper side of the main cylindrical reflector, the lower side of the main cylindrical reflector, the left side of the main cylindrical reflector, the right side of the main cylindrical reflector, the upper side of the auxiliary cylindrical reflector, the lower side of the auxiliary cylindrical reflector, the left side of the auxiliary cylindrical reflector and the right side of the auxiliary cylindrical reflector form a box-shaped cavity through the upper cover plate, the lower cover plate, the left baffle and the right baffle respectively, the horn conducting feed on the box-shaped cavity is hidden inside the box-shaped cavity and a waveguide port in the rear portion of the horn serves as a feed port. The box-shaped fan-beam antenna can provide fan beams with a wide pitch (azimuth) range and a narrow azimuth (pitch) range, and is simple in structural form, easy to process and manufacture and very suitable for being applied to millimeter-wave and over-submillimeter-wave frequency bands.

Utilization of cassegrain feed parabolic antenna design in increasing the efficiency of photovoltaic module

Abstract: This paper presents the design of a transportable solar concentrating and tracking parabolic trough reflector that gathers higher energy yield in its photovoltaic (PV) module using the concept of the Cassegrain antenna system wherein the sun's rays are dashed to the structure's primary and secondary reflector before they are converged to the polycrystalline solar panel located at the trough's focus Based from the system evaluation, the power output gathered from the whole system is 3605% and 905% more effective than the static and sun-tracking solar panel, respectively Likewise, the project yielded a solar panel efficiency of 1294% which is 467% and 117% greater than the ones produced by the static and sun-tracking PV cell, correspondingly Moreover, it has been calculated that the whole system charges 2 hours and 1681 minutes faster than the static PV cell's battery, and 2415 minutes quicker than the sun-tracking solar panel's battery