Showing papers on "Cassegrain antenna published in 2015"
TL;DR: In this paper, a planar lower reflector with an incorporated feed at its center and a polarizing grid on top as an upper reflector was proposed for beam steering in reconfigurable, high gain, low profile, and low-cost antennas.
Abstract: A reconfigurable antenna based on the liquid crystal technology is presented in this paper. The antenna comprises a planar lower reflector with an incorporated feed at its center and a polarizing grid on top as an upper reflector. The lower reflector is utilized to collimate the beam and to twist the polarization. The polarizing grid selects the polarization for the transmission and reflects the orthogonally polarized waves toward the lower reflector. Combining reflector elements with a polarizing grid allows performing additional phase adjustment on the upper reflector for beam steering. Reconfigurability is maintained by the upper reflector, in which a liquid crystal mixture is used as a tunable substrate. The liquid crystal layer is tuned with a bias voltage configuration to obtain an appropriate phase adjustment for the beam steering. As a proof of concept, the beam steering capability of the antenna is demonstrated by steering the main beam to $-6^{\circ}$ , 0 $^{\circ}$ , and 6 $^{\circ}$ at 78 GHz. The measured gain at 78 GHz is 25.1 dB. The proposed antenna configuration is a promising candidate for reconfigurable, high-gain, low-profile, and low-cost antennas.
174 citations
TL;DR: Not all worldwide aspects of reflector antenna developments are touched upon in this paper, and the authors have confined themselves to the areas that have influenced their research activities.
Abstract: i»?Reflector antennas confine most of the electromagnetic energy captured over their apertures into a focal plane or redirect the radiated field of the feed into far field. This paper presents a concise history of reflector antenna developments over an extended time span. Representative examples are provided for different periods that impacted various developments of reflector antennas covering past, present, and future. Due to page limitations, not all worldwide aspects of reflector antenna developments are touched upon in this paper, and the authors have confined themselves to the areas that have influenced their research activities.
63 citations
TL;DR: In this article, the design of a reflectarray antenna consisted of metallic elements, which can be manufactured via the simple die casting process as that for the reflector antennas, resulting in very high radiation efficiency at a low manufacture cost.
Abstract: This letter presents the design of a reflectarray antenna consisted of metallic elements, which can be manufactured via the simple die casting process as that for the reflector antennas. In the design, the reflecting elements are integrated as a whole piece of metal without using any dielectric or air substrates, and result in very high radiation efficiency at a low manufacture cost. The antenna is prototyped at Ku-band for the civilian satellite DTV applications. The experimental results show a radiation efficiency up to 90% comparable to the reflector antennas, and demonstrate the feasibility of the design concept.
52 citations
07 Mar 2015
TL;DR: Various PAFR architectures that are widely applicable to a diverse set of space missions (both earth sensing and interplanetary) are reviewed, the RF performance of these architectures are compared and key hardware design and implementation trades are described.
Abstract: Communication link and target ranges for satellite communications (SATCOM) and space-based sensors (e.g. radars) vary from approximately 400–1000 km for low earth orbits (LEO) to 35,800 km for geosynchronous orbits (GEO). At these long ranges, large antenna gains are required and most legacy systems use high gain reflectors with beams that are either fixed or mechanically steered. However, for some radio frequency (RF) sensor applications, mechanical beam scanning has inherent limitations.
49 citations
TL;DR: It is found that the MFB architecture applied in C-band is a more realistic approach when compared to the SFB option, and is the key to get compact feed clusters that can be allocated in large and medium-size platforms.
Abstract: Nowadays, broadband satellites operating at Ka-band and providing high capacity (above 100 Mbps) are mostly based on single-feed-per-beam (SFB) antenna configurations. This antenna farm, using typically three or four reflectors to produce the full dual-band (Tx/Rx) multiple beam coverage, provides high performance but leaves no or little room on the spacecraft for other missions. Accommodation constraints and the desire of operators to maximize and diversify their revenues per satellite have led to several studies on innovative antenna solutions enabling to reduce the number of reflector apertures. Multiple-feed-per-beam (MFB) antenna configurations, using only two apertures, are currently under development for broadband missions at Ka-band. C-band is a more mature business and operators are contemplating the possibility to apply the benefits of multiple beam antennas (MBA) to this frequency band. Due to the lower operating frequency, accommodation constraints are even more stringent and although still scarcely discussed, MFB antenna configurations at C-band are clearly of interest. This paper presents investigations on this topic. In particular, it is found that the MFB architecture applied in C-band is a more realistic approach when compared to the SFB option. Beam Forming Networks (BFNs) with periodic structure is the key to get compact feed clusters that can be allocated in large and medium-size platforms. A new four color scheme compatible with a very compact MFB feed array architecture is introduced.
41 citations
TL;DR: In this paper, a dual-surface reflector (DSR) antenna working in dual circular polarization (CP) is presented, which consists in a linearly polarized dual-gridded reflector that is made of a solid parabolic reflector on which a reflectarray that reflects horizontal polarization (HP) and is transparent to the vertical polarization (VP) is affixed.
Abstract: This paper presents the design of a dual-surface reflector (DSR) antenna working in dual circular polarization (CP) This DSR consists in a linearly polarized dual-gridded reflector (DGR) that is made of a solid parabolic reflector on which a reflectarray that reflects horizontal polarization (HP) and is transparent to the vertical polarization (VP) is affixed The conversion from linear polarization (LP) to CP of this antenna is realized by introducing a three-layer meander-line circular polarizer optimized for oblique incidence The antenna system was designed to generate two main beams in different directions and orthogonal CPs This antenna has been fabricated and characterized For the two polarizations, the realized gain is higher than 30 dB with a cross-polarization discrimination (XPD) higher than 27 dB in the 18–20 GHz frequency band
33 citations
TL;DR: In this paper, a parabolic reflector antenna with an azimuthally deformed Cassegrain subreflector is proposed to effectively generate arbitrary orbital angular momentum (OAM) modes.
Abstract: A parabolic reflector antenna with an azimuthally deformed Cassegrain subreflector is proposed to effectively generate arbitrary orbital angular momentum (OAM) modes. The Cassegrain dual-reflector antenna was fabricated for 18 GHz and measured in the near-field range. The near-field to far-field transformed radiation phase around a full azimuth shows that the proposed antenna generates fields with the l
= 1 OAM mode. Simulated and measured feed reflection coefficients are below -10 dB for 15.1-21.2 GHz, even though the distance between a horn feed and a deformed subreflector is 15.6 mm, thus it is expected that the proposed structure can be used for a broadband low-profile antenna.
31 citations
TL;DR: In this article, a design for wideband circularly polarized (CP) antennas with unidirectional radiation is described, and the antenna structure is mainly composed of a rectangular slotted patch and a metallic 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, an optimum CP design for the standalone slotted patch antenna is investigated, and a 3-dB-axial-ratio bandwidth of 53% is obtained. Then, the metallic reflector is placed at the rear of the slotted patch for generating unidirectional radiation, and the effects of various reflector sizes on CP performances are studied. Measured results show that the slotted patch antenna with a reflector has almost the same CP bandwidth as the standalone slotted patch antenna, and it has good impedance matching as well as stable radiation patterns across the CP operating frequencies.
27 citations
TL;DR: Three-dimensional ray tracing simulation and the experimental test show that the aberrations caused by on-axial defocusing, off-axia defocusing and deflection of receiving antenna can be well corrected by the optical fiber coupling system.
Abstract: A Cassegrain antenna system and an optical fiber coupling system which consists of a plano-concave lens and a plano-convex lens are designed based on the vector theory of reflection and refraction, so as to improve the transmission performance of the optical antenna and fiber coupling system. Three-dimensional ray tracing simulation are performed and results of the optical aberrations calculation and the experimental test show that the aberrations caused by on-axial defocusing, off-axial defocusing and deflection of receiving antenna can be well corrected by the optical fiber coupling system.
26 citations
TL;DR: A promising architecture based on dual frequency printed Fresnel reflectors is presented in this paper, which can either be combined with electric motors or transformed into a reconfigurable reflectarray system by replacing the passive reflecting cells by reconfigured ones.
Abstract: Satellite-based telecommunication systems operating in Ka-band require high gain ground terminal antennas. A promising architecture based on dual frequency printed Fresnel reflectors is presented in this paper. The complete development of this antenna including its design methodology, manufacturing, and testing is described. In order to scan its beam, the proposed antenna system can either be combined with electric motors or be transformed into a reconfigurable reflectarray system by replacing the passive reflecting cells by reconfigurable ones. A possible way of implementing such electronically reconfigurable reflecting cells is also presented.
24 citations
TL;DR: An optical model with a hyperbola-parabola primary mirror added in the Cassegrain optical antenna, which can effectively improve the transmission efficiency, is proposed in this paper.
Abstract: An optical model with a hyperbola-parabola primary mirror added in the Cassegrain optical antenna, which can effectively improve the transmission efficiency, is proposed in this paper. The optimum parameters of a hyperbola-parabola primary mirror and a secondary mirror for the optical antenna system have been designed and analyzed in detail. The parabola-hyperbola primary structure optical antenna is obtained to improve the transmission efficiency of 10.60% in theory, and the simulation efficiency changed 9.359%. For different deflection angles to the receiving antenna with the emit antenna, the coupling efficiency curve of the optical antenna has been obtained.
TL;DR: In this article, the problem of beam squinting in circularly polarized offset reflector antennas is solved by using a novel focal plane array concept that consists of sequentially rotated linearly polarized elements.
Abstract: The problem of beam squinting in circularly polarized offset reflector antennas is solved by using a novel focal-plane array concept that consists of sequentially rotated linearly polarized elements. This concept can be used to facilitate beam steering in full-duplex communication with satellite Internet (VSAT) operating in the Ka-band. A prototype consisting of a 75-cm offset dish illuminated by a $2 \times 2$ array of sequentially rotated aperture-coupled microstrip antennas was developed and tested at 20 GHz. Experimental results clearly demonstrate the removal of the beam-squint and resulted in an axial ratio (AR) below 1 dB within the 1-dB beamwidth of the main beam.
TL;DR: In this paper, results of modeling of the temperature and stressed-strained states of the reflector of a mirror space antenna installed on a spacecraft that conducts a flight on geostationary and low near-earth orbits have been presented.
Abstract: Results of modeling of the temperature and stressed-strained states of the reflector of a mirror space antenna installed on a spacecraft that conducts a flight on geostationary and low near-earth orbits have been presented.
Proceedings Article•
01 Nov 2015TL;DR: In this article, a novel planar printed quasi-Yagi antenna with a single director and a concave parabolic reflector operating in S-band is proposed, and the measured results indicate that the antenna which can operate at 2.28-2.63GHz can achieve an average gain of 6.5dBi within the operating frequency range.
Abstract: The simplicity and intuitive design of traditional planar printed quasi-Yagi antennas has led to its widespread popularity for its good directivity. In this paper, a novel quasi-Yagi antenna with a single director and a concave parabolic reflector, operating in S-band, is proposed. The impedance characteristic and radiation characteristic are simulated with CST-Microwave Studio, and the antenna is fabricated and measured. The measured results indicate that the antenna which can operate at 2.28–2.63GHz can achieve an average gain of 6.5dBi within the operating frequency range, especially a highest gain of 7.5dBi at 2.5GHz. The proposed antenna can be widely used in WLAN/TD-LTE/BD1 and so on.
Proceedings Article•
13 May 2015TL;DR: In this paper, a dual-reflector antenna geometry combining multiple-feed-per-beam feed systems and a dichroic subreflector was proposed to produce a full dual-band (Tx/Rx) multiple beam coverage as typically required for broadband satellite missions.
Abstract: This paper describes a dual-reflector antenna geometry combining multiple-feed-per-beam feed systems and a dichroic sub-reflector to produce a full dual-band (Tx/Rx) multiple beam coverage as typically required for broadband satellite missions. The proposed antenna configuration has several advantages as it requires only one main reflector aperture to produce the full coverage and makes use of two single band (Tx and Rx) multiple-feed-per-beam feed systems that are scaled versions of each other. Preliminary results are presented at antenna level assuming perfect dichroic screen and feed systems. These results confirm the potential of the proposed configuration for missions having strong satellite accommodation constraints and requiring a relatively small number of beams (typically less than 50 beams). This could particularly be of interest on board of small platforms or for secondary payloads. The dichroic sub-reflector being the critical point in this configuration, a preliminary feasibility study is also included, providing promising results.
TL;DR: In this paper, a special conical lens and photonic crystal reflector are used to increase transmission efficiency of the Cassegrain antenna, and the Gauss beam is shaped into a hollow beam, which could avoid the loss of energy caused by the subreflector center reflection in the CSA.
15 Oct 2015
TL;DR: In this article, the authors presented a brief summary of their attempt to calibrate a 6-m dish telescope used in Belgium for solar spectrography by using an Unmanned Aerial Vehicle (UAV) carrying a small emitter.
Abstract: Paraboloid antenna telescopes have been used for the last 70 years to perform radio astronomy observations and their main characteristics are well known. Over the years, telescopes operated at a given facility are often modified or upgraded with new feeds or support struts, or see their immediate surrounding environment modified. The gain of such instruments needs therefore to be measured to account for these external factors. Radio astronomers typically use galactic or extra galactic sources to assess the directional pattern. However, small radio telescopes (5–6 m) might not have the proper sensitivity to observe, in good conditions, such sources at different elevations in the sky. We present in this article a brief summary of our attempt to calibrate a 6-m dish telescope used in Belgium for solar spectrography by using an Unmanned Aerial Vehicle (UAV) carrying a small emitter.
TL;DR: In this article, a matched feed structure for an offset parabolic reflector antenna is presented, where the feed aperture formed by an intersection of circular and rectangular waveguides provides wide cross-polar bandwidth due to the cutoff wave numbers being close for the two modes used in conjugate matching.
Abstract: This letter presents the details of a novel matched feed structure which promises improved cross-polar performance for an offset parabolic reflector antenna. Feed aperture formed by an intersection of circular and rectangular waveguides provides wide cross-polar bandwidth due to the cutoff wave numbers being close for the two modes used in conjugate matching. The mode coefficients and relative phase difference are estimated using particle swarm optimization (PSO) technique for the specified antenna system. Physical optics (PO) is used to evaluate the reflector pattern; feed radiation pattern is obtained using mode field patterns and cutoff wave numbers, which are computed using 2-D finite element method (FEM). The higher order mode which is combined with the main operating mode of the waveguide for conjugate matching is generated using two posts placed behind the aperture. The antenna system performance is evaluated using HFSS and CST Microwave Studio.
TL;DR: In this paper, a Vlasov antenna with curved cut shape and improved reflector position and geometry suitable for high power microwave applications is presented. And the proposed antenna results in increased antenna gain and in good performance in terms of sidelobe level and half-power beamwidth, with maximum radiation directed toward the axis of the waveguide center.
Abstract: This paper presents a Vlasov antenna with curved cut shape and improved reflector position and geometry suitable for high power microwave applications. The curved shape of the proposed cut totally eliminates the sharp edges and angles present in Vlasov antennas with step and bevel cuts. Furthermore, with the proposed reflector configuration, the wave is radiated in the direction of the axis of the waveguide. A Vlasov antenna, designed for operation at 3 GHz, is used to compare the three cut types. An additional comparison is conducted to validate the concept of the enhanced reflector position, using the bevel-cut antenna and the improved cut. The proposed antenna results in increased antenna gain and in good performance in terms of sidelobe level and half-power beamwidth, with maximum radiation directed toward the axis of the waveguide center.
17 May 2015
TL;DR: This paper reviews some recent development in millimetre-wave smart antennas for satellite communications as well as show some results of case studies on this topic.
Abstract: This paper reviews some recent development in millimetre-wave smart antennas for satellite communications as well as show some results of case studies on this topic. Two case studies are presented, including one Ka-band fully integrated active reflectarray with wide-angle beam steering capabilities for SatCom on the move, and one beam-switching array-fed reflector antenna for advanced satellite communications. Design concept of the antenna elements and arrays in each case studies are explained and discussed.
02 Jul 2015
TL;DR: Hybrid-reflector multibeam antennas employed in satellite navigation systems transform adopted accelerated spatial filtering algorithms to select an amplitude-phase distribution from a set of precalculated distributions for various interference signaling environments in the beam where the interference signal affects the radiation pattern of the main lobe.
Abstract: Hybrid-reflector multibeam antennas employed in satellite navigation systems transform adopted accelerated spatial filtering algorithms. In order to accelerate the algorithm, the adaptive system selects an amplitude-phase distribution from a set of precalculated distributions for various interference signaling environments in the beam where the interference signal affects the radiation pattern of the main lobe. Specification of the weighted coefficients is performed after the most appropriate amplitude-phase distribution has been selected. Data from the weighted coefficients calculations is used for null formation in radiation patterns of beams where interference affects the side lobes.
Proceedings Article•
13 May 2015
TL;DR: An optimal beamforming algorithm for phased-array antenna systems designed to operate as focal plane arrays (FPA) in push-broom radiometers is presented, yielding much higher spatial and radiometric resolution as well as much closer distance to coast, as compared to the present-day systems.
Abstract: Strict requirements for future spaceborne ocean missions using multi-beam radiometers call for new antenna technologies, such as digital beamforming phased arrays. In this paper, we present an optimal beamforming algorithm for phased-array antenna systems designed to operate as focal plane arrays (FPA) in push-broom radiometers. This algorithm is formulated as an optimization procedure that maximizes the beam efficiency, while minimizing the side-lobe and cross-polarization power in the area of Earth, subject to a constraint on the beamformer dynamic range. The proposed algorithm is applied to a FPA feeding a torus reflector antenna (designed under the contract with the European Space Agency) and tested for multiple beams. The results demonstrate an improved performance in terms of the optimized beam characteristics, yielding much higher spatial and radiometric resolution as well as much closer distance to coast, as compared to the present-day systems.
19 Jul 2015
TL;DR: In this article, the design of a X/Ku multiband feed antenna is described, which exhibits a fixed phase center at each band and low cross-polarity levels, and provides 15-25% bandwidth.
Abstract: The design of a X/Ku multiband feed antenna is described. Narrowband components from a previously designed Ka/Q band feed were modified to provide 15–25% bandwidth. This feed antenna exhibits a fixed phase center at each band and low cross polarization levels.
01 Dec 2015
TL;DR: In this article, a planar Yagi-Uda antenna using the parabolic reflector is designed and compared to that of using the conventional straight reflector, which can reduce the occupied antenna area by about 29.4%.
Abstract: A planar Yagi-Uda antenna using the parabolic reflector is designed and compared to that of using the conventional straight reflector. Both antennas are designed to have the same performance. Simulation results show that the parabolic reflector design can reduce the occupied antenna area by about 29.4% as compared to that of the straight reflector design, while the antenna directivity and efficiency are retained at 7.16 dBi and −0.70 dB, respectively. Thus the parabolic reflector design is suitable for designing compact directive antennas in the low-profile devices.
01 Dec 2015
TL;DR: In this paper, a technique for performance enhancement of a ribcage dipole antenna using a Frequency Selective Surface (FSS) based corner reflector in the C band (4-6 GHz) has been demonstrated.
Abstract: A technique for performance enhancement of a ribcage dipole antenna using a Frequency Selective Surface (FSS) based corner reflector in the C band (4–6 GHz) has been demonstrated in this paper. The proposed corner reflector is composed of two reflective FSS screens at an angle of 90° and is placed at a specific distance from the antenna. The reflector improves impedance bandwidth of the antenna from 27% to 53%. An improvement of 7–9dB is achieved in antenna gain over the frequency range of interest and it is maintained near 11 dBi with a variation of ±1dB in the C band. The proposed design offers a significant antenna front to back ratio of upto 28 dB.
16 Mar 2015
TL;DR: The benefits of the active multifeed Ka-band developments for satellite communication are shown as well as first project results.
Abstract: Recent results on active multifeed Ka-band developments for satellite communication are presented. Basically, the active multifeed system is an array-fed, single-offset reflector antenna. The antenna array is fed by an active microstrip beamforming network based on a low temperature cofired ceramics substrate with monolithic microwave integrated circuit based phase and amplitude actuators. In this paper, the benefits of such a technology are shown as well as first project results.
TL;DR: In this article, a method to generate several phase centers on a single parabolic reflector antenna fed by a digital beamforming array is presented for along-track SAR interferometry at higher frequencies, as for example, in the Ka-band.
Abstract: A method to generate several phase centres on a single parabolic reflector antenna fed by a digital beamforming
array is presented. Among other applications, along-track SAR interferometry at higher frequencies, as for example, in the Ka-band, is considered. Flexibility in size, position and amount of phase centres is similar as for a setup using a direct radiating array.
Patent•
29 Oct 2015TL;DR: In this article, the second reflector is arranged relative to the first reflector in order to satisfy a near-field interference isolation criterion between the first and second antennae, where the distance between the antenna mounts is less than a distance between antenna mounts arranged in a plane.
Abstract: In one implementation, an apparatus includes: a first reflector portion having a first mount for a first antenna that is configured to operate in a first frequency range, where the first mount characterizes an emission point of a main lobe of the first antenna; and a second reflector portion having a second mount for a second antenna that is configured to operate in a second frequency range that overlaps the first frequency range, where the second mount characterizes an emission point of a main lobe of the second antenna. The second reflector portion is arranged relative to the first reflector portion in order to satisfy a near-field interference isolation criterion between the first and second antennae. In some implementations, the distance between the antenna mounts is less than a distance between the antenna mounts arranged in a plane due to increased spatial diversity between the first and second antennae.
Patent•
08 Dec 2015
TL;DR: In this paper, a spacecraft with a linear extension boom, an antenna feed, and a rigid antenna reflector is provided, and the rigid antenna is connected with the linear extension by a positioning mechanism that provides for adjustment in the angular orientation of the reflector relative to the LBO.
Abstract: A spacecraft with a linear extension boom, an antenna feed, and a rigid antenna reflector is provided. The rigid antenna reflector may be connected with one end of the linear extension boom, and the other end of the linear extension boom may be connected with the spacecraft main body. In a launch configuration of the spacecraft, the linear extension boom may be retracted into a stowed configuration, and in an on-orbit configuration of the spacecraft, the linear extension boom may be extended into a deployed configuration, thereby moving the rigid antenna reflector away from the yaw axis of the spacecraft and positioning the rigid antenna reflector such that the focal point of the rigid antenna reflector may be oriented to align on, and be collocated with, the antenna feed. The rigid antenna reflector may be connected with the linear extension boom by a positioning mechanism that provides for adjustment in the angular orientation of the rigid antenna reflector relative to the linear extension boom.
19 Jul 2015
TL;DR: By expanding the scale of feed array as well as the RF switch matrix, a much more comprehensive feed subsystem can be developed to produce multiple independent hopping beams in association with a reflector.
Abstract: This paper introduces the design of a feed subsystem for a multiple-beam array-fed reflector antenna. The prototype is composed of 37 circularly polarized horns and a complicated RF switch matrix. The feed horns are divided into four interleaved groups. Each time four adjacent feed horns, i.e., each from one group, are selected by the RF switch matrix to connect to a signal processor where the delivered signals are weighted and combined to form a radiation beam. The beam can be controlled to hop in a certain zone with the response time at the level of μs. The use of RF switch matrix reduces the cost of signal processing. By expanding the scale of feed array as well as the RF switch matrix, a much more comprehensive feed subsystem can be developed to produce multiple independent hopping beams in association with a reflector. The scheme and experimental results of the prototype are presented in the context.