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Showing papers on "Cassegrain antenna published in 2018"


Journal ArticleDOI
TL;DR: In this paper, a compact Ka-band monopulse Cassegrain antenna based on the reflectarray elements is presented, which consists of a main-reflectarray, a sub-reflect array, a substrate integrated waveguide comparator, and a monopulse feed to achieve good sum-difference characteristics.
Abstract: A compact Ka-band monopulse Cassegrain antenna based on the reflectarray elements is presented in this letter. The proposed antenna consists of a main-reflectarray, a subreflectarray, a substrate integrated waveguide comparator, and a monopulse feed to achieve good sum–difference characteristics. Compared with traditional monopulse Cassegrain antenna, the total length of the proposed antenna is shrunken to 67.85%. The results of measurement agree with that of simulation very well. The measured SUM beam gain of the proposed antenna is 29.4 dBi by eliminating the loss of Ka-band comparator, the 3 dB beamwidth is 3.85°, the first sidelobe level is under −12 dB, the cross-polarization level is better than −20 dB, and the gain ratios between the SUM and DIFF are about 3 and 5 dB in azimuth and elevation plane, respectively. The measured results show that the proposed antenna is a good candidate for the low-cost multimode tracking system with limited space, especially for that working at high frequency.

38 citations


Journal ArticleDOI
TL;DR: A holistic design procedure for such novel multibeam radiometers has been developed, where the antenna system specifications are derived directly from the requirements to oceanographic surveys for future satellite missions and the numbers of FPA elements/receivers are determined through a dedicated optimum beamforming procedure minimizing the distance to coast.
Abstract: The present-day ocean remote sensing instruments that operate at low microwave frequencies are limited in spatial resolution and do not allow for monitoring of the coastal waters. This is due to the difficulties of employing a large reflector antenna on a satellite platform, and generating high-quality pencil beams at multiple frequencies. Recent advances in digital beamforming focal-plane arrays (FPAs) have been exploited in this paper to overcome the above problems. A holistic design procedure for such novel multibeam radiometers has been developed, where: 1) the antenna system specifications are derived directly from the requirements to oceanographic surveys for future satellite missions and 2) the numbers of FPA elements/receivers are determined through a dedicated optimum beamforming procedure minimizing the distance to coast. This approach has been applied to synthesize FPAs for two alternative radiometer systems: a conical scanner with an offset parabolic reflector and a stationary wide-scan torus reflector system, each operating at $C$ -, $X$ -, and Ku-bands. Numerical results predict excellent beam performance for both systems with as low as 0.14% total received power over the land.

32 citations


Journal ArticleDOI
Guoping Gao1, Chen Yang1, Bin Hu1, Shaofei Wang1, Rui-Feng Zhang1 
TL;DR: In this paper, a high-gain and low-profile quasi-Cassegrain antenna based on metasurfaces (MS) is proposed, which achieves the peak gain of 13.7−dBi, sidelobe level less than −19−dB, and half-power beamwidth of 38° (H -plane) and 28° (E -plane).
Abstract: In this letter, a high-gain and low-profile quasi-Cassegrain antenna based on metasurfaces (MS) is proposed. Thanks to the structure of the dual reflectors and the phase compensation technology achieved by MS, the proposed antenna presents a balance between high gain and low profile. This antenna achieves the peak gain of 13.7 dBi, sidelobe level less than −19 dB, and half-power beamwidth of 38° ( H -plane) and 28° ( E -plane). At the same time, it has a low profile of 12.6 mm (0.244 λ 0) and occupies an area of 132 mm × 132 mm (2.55 λ 0 × 2.55 λ 0). The proposed quasi-Cassegrain antenna in this letter provides an alternative for the high-gain and low-profile antenna and also enriches the applications of MS in the microwave band.

18 citations


Journal ArticleDOI
TL;DR: The development process of electrical performance compensation methods for radio telescope antennas is introduced, and four typical large antennas that have been designed with active main reflector technology are presented and compared.
Abstract: With the development of radio telescope antennas with large apertures, high gain, and wide frequency bands, compensation methods, such as mechanical or electronic compensation, are obviously essential to ensure the electrical performance of antennas that work in complex environments. Since traditional compensation methods can only adjust antenna pointing but not the surface accuracy, which are limited for obtaining high surface precision and aperture efficiency, active surface adjustment has become an indispensable tool in this field. Therefore, the development process of electrical performance compensation methods for radio telescope antennas is introduced. Further, a series of analyses of the five key technologies of active surface adjustment is presented. Then, four typical large antennas that have been designed with active main reflector technology are presented and compared. Finally, future research directions and suggestions for reflector antenna compensation methods based on active surface adjustment are presented.

16 citations


Journal ArticleDOI
TL;DR: A procedure based on using multimode Gaussian optics to pick the optimum design and using PO for final verification of the system performance is presented, finding the best antenna efficiency is achieved when the beam illuminating the subreflector is truncated with the optimum edge taper.
Abstract: The latest generation of Cassegrain radio astronomy antennas is designed for multiple frequency bands with receivers for individual bands offset from the antenna axis. The offset feed arrangement typically has two focusing elements in the form of ellipsoidal mirrors in the optical path between the feed horn and the antenna focus. This arrangement aligns the beam from the offset feed horn to illuminate the subreflector. The additional focusing elements increase the number of design variables, namely the distances between the horn aperture and the first mirror and that between the two mirrors, and their focal lengths. There are a huge number of possible combinations of these four variables in which the optics system can take on. The design aim is to seek the combination that will give the optimum antenna efficiency, not only at the centre frequency of the particular band but also across its bandwidth. To pick the optimum combination of the variables, it requires working through, by computational mean, a continuum range of variable values at different frequencies which will fit the optics system within the allocated physical space. Physical optics (PO) is a common technique used in optics design. However, due to the repeated iteration of the huge number of computation involved, the use of PO is not feasible. We present a procedure based on using multimode Gaussian optics to pick the optimum design and using PO for final verification of the system performance. The best antenna efficiency is achieved when the beam illuminating the subreflector is truncated with the optimum edge taper. The optimization procedure uses the beam’s edge taper at the subreflector as the iteration target. The band 6 receiver optics design for the Atacama Large Millimetre Array (ALMA) antenna is used to illustrate the optimization procedure.

7 citations


Journal ArticleDOI
TL;DR: In this article, the effect of antenna strut elongation on propagation measurements was investigated, which caused an additional reduction of 1-2 dB in the received signal during sunny days in the Alphasat Aldo Paraboni propagation experiment, where two large ground terminals were deployed in Tito Scalo (South of Italy) and Spino d'Adda (North of Italy).
Abstract: Large gateways of future satellite communications (Satcom) systems will likely operate at Q-/V-band frequencies (40–50 GHz) to take advantage of the larger available bandwidth. On the other hand, Q-/V-band Satcom systems suffer from highly variable propagation losses, which must be accurately assessed and modeled. The Alphasat Aldo Paraboni propagation experiment, conceived and realized by the Italian Space Agency (ASI), Rome, Italy, has been running since 2014 to carefully investigate the propagation effects in the Ka- and Q-band and, thus, to support the design of high-throughput systems and propagation impairment mitigation techniques. In the framework of this experiment, ASI deployed two large ground terminals (Cassegrain antenna with 4.2 m diameter) in Tito Scalo (South of Italy) and Spino d’Adda (North of Italy). This contribution investigates the effect of antenna strut elongation on propagation measurements, which causes an additional reduction of 1–2 dB in the received signal during sunny days.

7 citations


Patent
21 Dec 2018
TL;DR: In this paper, a large-aperture offset feed Cassegrain deployment antenna consisting of a main reflective surface assembly and a sub-reflective surface assembly is proposed, where a fixed surface, a first expanded surface and a second expanded surface, respectively installed on a corresponding fixed surface back frame,a first expanded-surface back frame and an expanded-surface back frame through an adjusting device.
Abstract: A large-aperture offset feed Cassegrain deployment antenna comprises a main reflective surface assembly and a sub-reflective surface assembly, wherein the main reflective surface assembly is a 5-meter-diameter rotating paraboloid, which is divided into a fixed surface, a first expanded surface and a second expanded surface, and is respectively installed on a corresponding fixed surface back frame,a first expanded surface back frame and a second expanded surface back frame through an adjusting device; A sub-reflecting surface combination comprise a first sub-reflecting part and a second sub-reflecting part, which are respectively mounted on that sub-anti-unfolding arm by an adjusting device; The first pair is a 1-meter hyperboloid and the second pair is a 1.4-meter plane. The invention canrealize the ground folding of the large-caliber offset-fed Cassegrain antenna to meet the requirements of the carrier envelope, realize deployment and position maintenance on the orbit, and finally form an antenna system to realize the requirements of remote sensing and signal transmission functions on the orbit.

6 citations


Patent
06 Nov 2018
TL;DR: In this paper, a passive millimeter wave dual-channel synchronous imaging system for security inspection and an imaging method thereof is presented, where the smooth metal reflecting plane is fixed on the longitudinal rotary plate at an angle of 45 degrees.
Abstract: The invention discloses a passive millimeter wave dual-channel synchronous imaging system for security inspection and an imaging method thereof, and belongs to the technical fields of millimeter waveimaging, security inspection and the like. The passive millimeter wave dual-channel synchronous imaging system comprises a smooth metal reflecting plane, a Cassegrain antenna, a radiometer, a longitudinal rotary plate, an optical fiber sensor, a horizontal rotary plate, a sensor retaining piece, a proximity switch, a data acquisition unit, a computer and a scanning control unit, wherein the smoothmetal reflecting plane is fixed on the longitudinal rotary plate at an angle of 45 degrees, the longitudinal rotary plate and the Cassegrain antenna are coaxially fixed on the horizontal rotary plate, a feed source of the Cassegrain antenna is connected with the radiometer, the radiometer is connected with the data acquisition unit, and the data acquisition unit is connected with the computer. The imaging system has the advantages of simple structure, low cost, small size, low power consumption, high stability and high imaging speed, can effective detect dangerous articles hidden on a human body, and can simultaneously perform security inspection imaging on inspected people in security inspection channels at the left and right of a scanning platform, thereby greatly improving the securityinspection efficiency.

5 citations


Patent
15 Jun 2018
TL;DR: In this paper, a single-pulse cassegrain antenna for terahertz wave band was proposed. But the advantages of the singlepulse antenna have not yet been analyzed.
Abstract: The invention discloses a single-pulse cassegrain antenna applicable to a terahertz wave band. The single-pulse cassegrain antenna comprises a sum and difference channel radio frequency interface (1)and a cassegrain antenna (5) and also comprises a quasi-optical sum and difference network (3), a beam waveguide (4) and a feeding network (2). The quasi-optical sum and difference network (3) and thebeam waveguide (4) are employed, a metal reflection surface and a device such as a dielectric lens are used for converging and guiding an electromagnetic wave beam, and transmission and conversion ofan electromagnetic signal in a free space are achieved; and compared with traditional waveguide transmission, the single-pulse cassegrain antenna has the advantage that the defects of large loss andlow power capacity of a terahertz wave band waveguide transmission device are overcome.

5 citations


Patent
15 Nov 2018
TL;DR: In this article, a Cassegrain-type antenna is described, which consists of a main reflector, a sub-reflector, and a radiator radiating beams by using a plurality of emitters.
Abstract: Disclosed is a Cassegrain-type antenna. The Cassegrain-type antenna may comprise a main-reflector; a sub-reflector; and a radiator radiating beams by using a plurality of emitters. Also, a reflective surface of the sub-reflector has a shape of a trace formed by rotating a first curve having a vertex and being convex toward the main-reflector around a rotation axis spaced apart from the vertex.

2 citations


Proceedings ArticleDOI
01 Aug 2018
TL;DR: In this paper, the authors proposed a point-to-point communication system using the combination of high-gain antennas and an amplifier chain, which achieved an effective isotropic radiated power of more than 40 dBm.
Abstract: We propose a THz communication system using the combination of high-gain antennas and an amplifier chain. A Cassegrain antenna used as a high-gain antenna enhances a link gain with an antenna gain of 40 dBi or more. Finally, an effective isotropic radiated power is achieved more than 40 dBm. The proof-of-concept demonstration is performed for the realization of THz point-to-point communication systems with moderate spectral efficiency.

Patent
13 Nov 2018
TL;DR: In this paper, a metasurface-based cassegrain antenna was proposed to solve the problems that the existing cassegrained antenna is high in phase error, complex in structure, and long in focal length.
Abstract: The invention discloses a metasurface-based cassegrain antenna, and mainly aims to solve the problems that the existing cassegrain antenna is high in phase error, complex in structure, and long in focal length The metasurface-based cassegrain antenna comprises a carrier (1), a main reflecting mirror (2), an auxiliary reflecting mirror (3), a feed source (4) and a supporting structure (5); the carrier adopts a convex structure; the main reflecting mirror is conformal with the carrier; each of the main reflecting mirror and the auxiliary reflecting mirror adopts a phase change metasurface structure established based on generalized Snell law, wherein the auxiliary reflecting mirror is located below the focal point of the main reflecting mirror and has a hyperbolic characteristic phase, and is used for dispersing the electromagnetic waves emitted by the feed source into spherical waves; the main reflecting mirror and the auxiliary reflecting mirror are connected through the supporting structure; and the virtual focal point of the auxiliary reflecting mirror coincides with the focal point of the main reflecting mirror, and the solid focal point coincides with the phase center of the feed source By virtue of the metasurface-based cassegrain antenna, the focal length of the cassegrain antenna can be shortened, wave beam calibration can be realized; and meanwhile, the antenna phase compensation error is lowered, the structure is simple, and the antenna can be used for communication and radar

Patent
06 Nov 2018
TL;DR: In this paper, the authors proposed a metasurface-based transmissive Cassegrain antenna for solving the technical problem that effective radiation of electromagnetic waves is hindered due to the fact that a secondary reflector of a reflective Cassegr antenna shields a main reflector in the prior art.
Abstract: The invention provides a metasurface-based transmissive Cassegrain antenna for solving the technical problem that effective radiation of electromagnetic waves is hindered due to the fact that a secondary reflector of a reflective Cassegrain antenna shields a main reflector in the prior art. The metasurface-based transmissive Cassegrain antenna comprises a parallel planar waveguide, a secondary reflector, a main transmitting mirror and a feed source, wherein the secondary reflector, the main transmitting mirror and the feed source are located between two metal plates of the parallel planar waveguide; multiple uniformly arranged annular metal patches are printed on one side surface of the secondary reflector and a metal bottom plate is printed on the other side surface; the main transmittingmirror is of a multilayer dielectric layer structure; multiple uniformly arranged annular gaps are etched at the front sides of an odd number of dielectric layers; multiple uniformly arranged metal strips are printed at the front sides of an even number of dielectric layers; multiple uniformly arranged annular gaps are etched at the back side of the last dielectric layer; a rectangular horn antenna structure is adopted by the feed source; and a phase jump metasurface structure constructed on the basis of a generalized Snell's theorem is adopted by the main transmitting mirror and the secondary reflector.

Patent
29 Aug 2018
TL;DR: In this paper, a beam waveguide (BWG) type multi-band Cassegrain antenna which can be used to receive S band and X band radio waves radiated from the moon, the sun, a satellite, etc., communicate with a moon′s position orbiter, and be installed on the ground to control a probe or a satellite and transceive signals with a payload is presented.
Abstract: The present invention relates to a beam waveguide (BWG) type multi-band Cassegrain antenna which can be used to receive S band and X band radio waves radiated from the moon, the sun, a satellite, etc., communicate with a moon′s position orbiter, and be installed on the ground to control a probe or a satellite and transceive signals with a payload. The Cassegrain antenna of the present invention comprises a main reflector having a width of 20 to 40 meters, a main reflector support frame for supporting the main reflector, a sub reflector disposed on the front surface of the main reflector, a sub reflector support frame for supporting the sub reflector, a pedestal for supporting an antenna body on a base station, a vertical rotating means for rotating the antenna body in an elevation direction, a horizontal rotating means for rotating the antenna body in an azimuth direction, and a beam wave guide installed between the center of the main reflector and the base station for guiding the propagating beam, whereby it is possible to use four frequencies of S-band transceiving and X-band transceiving at the same time in a configuration of a large reflector radio telescope having a diameter of 20 to 40 meters.

Patent
26 Jan 2018
TL;DR: In this article, an optical antenna of a free space optical communication system and an automatic alignment method of the optical antenna is described. But the alignment is performed by using coordinate transformation of space to right angle, with the three vertexes of an equilateral triangle formed in the detector as foundation.
Abstract: The invention discloses an optical antenna of a free space optical communication system, and an automatic alignment method thereof, and belongs to the field of optical communication technology. The optical antenna comprises an antenna transmission head shell arranged at the top of a telescopic rod in a manner of being rotated for 360 degrees, and the telescopic rod is connected to the surface of the base via a rotating shaft that can rotate around the surface of the base, wherein a stray light aperture, a collimator, a Cassegrain antenna with an open secondary mirror, a pre-collimating deviceand a laser transmitting and receiving device are arranged on one side in the antenna transmission head shell away from the telescopic rod in sequence; the laser transmitting and receiving device comprises a semiconductor laser emission laser and a receiver; and the collimator comprises three detectors in central symmetry, and laser intensity sensors are arranged in the detectors. The laser beamsof the optical antenna are primarily aligned by using coordinate transformation of space to right angle, with the three vertexes of an equilateral triangle formed in the detector as foundation, accurate alignment is achieved by one-by-one alignment method, and the optical antenna can be applied to waveforms subjected to any deformation and information loss.

Patent
15 May 2018
TL;DR: In this article, the utility model discloses an optical antenna of free space optical communications system belongs to light communication technology field, including 360 rotatory setting in the first shells of the antenna transmission at a telescopic link top, this antenna link is linked in the base surface through following the rotatory pivot in base surface.
Abstract: The utility model discloses an optical antenna of free space optical communications system belongs to light communication technology field. This optical antenna including can 360 rotatory setting in the first shells of the antenna transmission at a telescopic link top, this telescopic link is linked in the base surface through following the rotatory pivot in base surface, wherein, the first shellof antenna transmission is inside keeps away from cassegrain antenna, collimating device and the laser emission reception device in advance that telescopic link top one side was equipped with the parasitics light diaphragm that disappears, sight, secondary mirror trompil in proper order, laser emission reception device includes semiconductor laser and receiver, the sight includes the three centrosymmetric of being detector, is equipped with laser light -intensity sensor in this detector. The utility model discloses after optical antenna's the laser beam adoption space commentaries on classicsrectangular coordinate transform preliminary alignment, the utilization is based on the equilateral triangle's of detector formation three summit, and the rigid alignment is carried out to the methodof going on aiming at one by one, can be directed against any deformation and information loss's wave form.


Proceedings ArticleDOI
22 Jul 2018
TL;DR: Numerical simulation results indicate that, with the benefits of using a predesigned Earch model, or even using a simple disc target, SA-MWR can greatly reduce the imaging error especially in the areas near to the Earth contour, and thus achieve a higher imaging accuracy than RA- MWR.
Abstract: The dream of launching a microwave radiometer into geostationary orbit (GEO) for atmosphere sounding has lasted for over four decades. Several concepts have been proposed, but none of them has come into reality by now. All these concepts can be divided into two different ways, using real aperture microwave radiometer (RA-MWR) and using synthetic aperture microwave radiometer (SA-MWR). This paper is dedicated to make a preliminary comparison between the imaging performances of the RA-MWR and SA-MWR in GEO applications. In the comparison, a similar concept with the Geostationary Observatory for Microwave Atmospheric Sounding (GOMAS) with a Cassegrain antenna proposed by ESA is taken as the RA-MWR example, while the concept of Geostationary Interferometric Microwave Sounder (GIMS) with a circular antenna array pursued in China is taken as the example of SA-MWR. The numerical simulation results indicate that, with the benefits of using a predesigned Earch model, or even using a simple disc target, SA-MWR can greatly reduce the imaging error especially in the areas near to the Earth contour, and thus achieve a higher imaging accuracy than RA-MWR.

Patent
20 Jul 2018
TL;DR: In this article, the authors proposed a Cassegrain antenna based on a super surface, which aims to reduce the phase compensation error of the antenna and simplify the antenna structure at the same time.
Abstract: The invention provides a Cassegrain antenna based on a super surface, and aims to reduce the phase compensation error of the antenna and simplify the antenna structure at the same time. The Cassegrainantenna comprises a slab waveguide, a main reflector, an auxiliary reflector and a feed source, wherein the main reflector, the auxiliary reflector and the feed source are clamped between two metal plates of the slab waveguide, both the main reflector and the auxiliary reflector adopt a phase sudden change super surface structure constructed based on a generalized Snell's law, the size of a metalring microstructure on a phase control layer of the main reflector is decided by the electromagnetic wave incident angle and the scattering parameter phase at the location so as to realize an electromagnetic wave phase compensation characteristic similar to that of a paraboloid, the size of a metal ring microstructure on a phase control layer on the auxiliary reflector is decided by the electromagnetic wave incident angle and the scattering parameter phase at the location so as to realize an electromagnetic wave phase compensation characteristic similar to that of a hyperboloid; and the feedsource is located at the midpoint of the main reflector which is opposite to the phase control layer of the auxiliary reflector, a virtual focus of the auxiliary reflector is overlapped with a focus of the main reflector, and a real focus of the auxiliary reflector is overlapped with a phase center of the feed source.

Patent
13 Jul 2018
TL;DR: In this paper, a frequency selection surface type curved surface dielectric and a cassegrain antenna system is described. But the authors do not specify the shape of the substrate.
Abstract: The invention discloses a frequency selection surface type curved surface dielectric and a cassegrain antenna system. The curved surface dielectric comprises a dielectric substrate; the upper surfaceof the dielectric substrate is a pot cover-shaped curved surface, while the lower surface adopts a shape which is cut towards the upper surface of the dielectric substrate on the basis of the same shape of the upper surface, so that the perpendicular distance from the upper surface to the lower surface of the dielectric substrate is gradually reduced from the outer edge to the center of the dielectric substrate; the upper surface of the dielectric substrate is attached with a metal layer of the set thickness; total reflection of energy at the required waveband is realized in the middle regionof the pot cover-shaped metal layer; and gap units of the same sizes are arranged on the metal layer of a peripheral region in an annular array form, so that transmission of the energy at the requiredwaveband is realized. The curved surface dielectric has the advantages as follows: by adjusting the thicknesses from the outer edge to the center of the dielectric substrate, changes of the dimensions of the gaps in the metal layer from the outer edge to the center is not needed even if the projection angle is changed, thereby greatly lowering the processing difficulty.

Patent
13 Nov 2018
TL;DR: In this paper, a metasurface-based convex conformal cassegrain antenna is proposed to solve the problems that the existing antenna is high in phase error, complex in structure, and hard to realize convex casse grain beam calibration.
Abstract: The invention discloses a metasurface-based convex conformal cassegrain antenna, and mainly aims to solve the problems that the existing antenna is high in phase error, complex in structure, and hardto realize convex cassegrain beam calibration The metasurface-based convex conformal cassegrain antenna comprises a carrier (1), a main reflecting mirror (2), an auxiliary reflecting mirror (3), a feed source (4) and a supporting structure (5); the carrier adopts a convex structure; the main reflecting mirror is conformal with the carrier; each of the main reflecting mirror and the auxiliary reflecting mirror adopts a phase change metasurface structure established based on generalized Snell law, wherein the auxiliary reflecting mirror is located below the focal point of the main reflecting mirror and has a hyperbolic characteristic phase, and is used for dispersing the electromagnetic waves emitted by the feed source into spherical waves, wherein the virtual focal point of the auxiliary reflecting mirror coincides with the focal point of the main reflecting mirror, and the solid focal point coincides with the phase center of the feed source; and the supporting structure is connected with the main reflecting mirror and the auxiliary reflecting mirror By virtue of the metasurface-based convex conformal cassegrain antenna, wave beam calibration of the convex cassegrain antenna can be realized; and meanwhile, the antenna phase compensation error is lowered, the structure is simple, and the antenna can be used for communication and radar

Patent
12 Jan 2018
TL;DR: The utility model discloses a routing equipment for information engineering, including routing equipment main part, master antenna, main antenna feed, main reflector, subreflector, slave antenna, liquid cooling system, louvre, cooling tube, liquid transfer duct, liquid conveying pump, heat sink and sucking disc.
Abstract: The utility model discloses a routing equipment for information engineering, including routing equipment main part, master antenna, main antenna feed, main reflector, subreflector, slave antenna, liquid cooling system, louvre, cooling tube, liquid -transfer duct, liquid conveying pump, heat sink and sucking disc, the master antenna has the structure the same with the cassegrain antenna antenna, belocated routing equipment main part both sides respectively, for ordinary antenna, routing equipment main part bottom is through buckle and liquid cooling system fixed connection, buckle and suckingdisc fixed connection are passed through to liquid cooling system's bottom. This practicality adopts the structure master antenna the same with cassegrain antenna to realize radio signal's reinforcingand orientation transmission, adopts liquid cooling system to make routing equipment's fixed mode diversified for the long -time routing equipment who works provides good heat -sinking capability with its performance of full play, the sucking disc of bottom, saves the desktop space.

Book ChapterDOI
01 Jan 2018
TL;DR: In this paper, the main aspects of the electromagnetic theory of the reflector antenna are summarized and a quantitative information on the relation between EM parameters and the resulting requirements on the hardware realisation of the antenna is presented.
Abstract: The purpose of the reflector antenna is to concentrate the radiation from a desired direction as effectively as possible in the focal point while suppressing interfering signals from other directions. The electromagnetic (EM) analysis of the antenna provides the basis for the definition and specification of the geometrical layout. This in turn has a strong influence on the structural and mechanical design and realisation of the antenna. Therefore, we devote this chapter to a summary of the main aspects of the electromagnetic theory of the reflector antenna. In particular, we present quantitative information on the relation between EM parameters and the resulting requirements on the hardware realisation of the antenna. The electromagnetic characteristics of even the largest radio telescope reflector cannot be properly described by geometrical optics only, as is usual for optical telescopes. A wave-based EM diffraction analysis is required to derive the parameters of the antenna: in particular its beam shape with sidelobes, polarisation state, gain and beam efficiency.

Journal ArticleDOI
TL;DR: In this article, a new method based on parameters iteration technique has been developed to determine the optimal subreflector position for shaped Cassegrain antennas to improve the electromagnetic (EM) performance distorted by gravity.
Abstract: A new method based on parameters iteration technique has been developed to determine the optimal subreflector position for shaped Cassegrain antennas to improve the electromagnetic (EM) performance distorted by gravity. Both the features of shaped surface and the relationship between optical path difference (OPD) and far field beam pattern are employed. By describing the shaped dual-reflector surface as a standard discrete parabola set, we can utilize the optical features of the standard Cassegrain system in the classical OPD relationship. Then, the actual far field beam pattern is expressed as the synthesis of ideal beam and error beam by decomposing subreflector adjustment parameters using mechanical-electromagnetic-field-coupling-model (MEFCM). Furthermore, a numerical method for determining optimal subreflector position is presented. The proposed method is based on the iteration technique of subreflector adjustment parameters, and the optimal far field pattern is used as the iteration goal. The numerical solution of optimal adjustment parameters can be obtained rapidly. Results of a 25 m Shaped Cassegrain antenna demonstrate that the adjustment of the subreflector to the optimal position determined by the proposed method can improve the EM performance effectively.