CN110767989A - Cassegrain antenna - Google Patents

Cassegrain antenna Download PDF

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Publication number
CN110767989A
CN110767989A CN201910851240.5A CN201910851240A CN110767989A CN 110767989 A CN110767989 A CN 110767989A CN 201910851240 A CN201910851240 A CN 201910851240A CN 110767989 A CN110767989 A CN 110767989A
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antenna
reflecting surface
main
quarter
cassegrain
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Chinese (zh)
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刘可
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Nanjing University of Aeronautics and Astronautics
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Nanjing University of Aeronautics and Astronautics
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/48—Earthing means; Earth screens; Counterpoises
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/50—Structural association of antennas with earthing switches, lead-in devices or lightning protectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/14—Reflecting surfaces; Equivalent structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q5/00—Arrangements for simultaneous operation of antennas on two or more different wavebands, e.g. dual-band or multi-band arrangements
    • H01Q5/20—Arrangements for simultaneous operation of antennas on two or more different wavebands, e.g. dual-band or multi-band arrangements characterised by the operating wavebands

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Aerials With Secondary Devices (AREA)

Abstract

The invention discloses a Cassegrain antenna, which comprises a feed source antenna (11), a main reflecting surface (13), an auxiliary reflecting surface (12) and a main and auxiliary reflecting surface fixing device (15); the feed source antenna (11) is a horn antenna, the main reflecting surface (13) adopts a paraboloid form, a round hole with the radius approximately equal to the working wavelength of 2.5-4mm is formed in the center of the auxiliary reflecting surface (12), the standing wave characteristic of the feed source antenna can be effectively improved, meanwhile, the energy directly radiated by the round hole can effectively make up the reflected energy lost by the opening, and the gain characteristic of the feed source antenna is also improved to a certain extent; the antenna also comprises a quarter-wave choke groove, wherein the quarter-wave choke groove (14) is positioned at the edge of the main reflecting surface, the width and the depth of the quarter-wave choke groove are quarter of the central working wavelength, diffraction of electromagnetic waves can be effectively reduced, a good inhibiting effect is realized on the level of a secondary lobe of the antenna, and the working frequency of the antenna is 75-110 GHz.

Description

Cassegrain antenna
Technical Field
The present invention relates to an antenna.
Background
The remote sensing technology is a technology for collecting electromagnetic radiation information of a ground object target from a satellite, an airplane or other aircrafts and judging the earth environment and resources. In remote sensing, the cassegrain antenna is the most commonly used one, and can well meet the requirements of remote sensing due to the narrow wave beam, high gain and low return loss. The cassegrain antenna is a double-reflector antenna, and comprises a feed source antenna, a main reflector, an auxiliary reflector and a fixing device for the main and auxiliary reflectors, wherein the focus of the main reflector is coincided with the virtual focus of the auxiliary reflector hyperboloid, a conical horn is positioned at the other virtual focus of the hyperboloid, electromagnetic waves are radiated on the paraboloid, reflected on the hyperboloid and reflected again, and focused on the conical horn. In the prior design, the hyperboloid is adopted as the sub-reflecting surface, so that the vertical incidence of electromagnetic waves is avoided, and the loss can not be completely avoided.
Disclosure of Invention
The invention aims to provide a Cassegrain antenna with excellent standing wave characteristics.
In order to solve the technical problem, the invention provides a cassegrain antenna, which comprises a feed source antenna, a main reflecting surface, an auxiliary reflecting surface and a main and auxiliary reflecting surface fixing device, wherein the main reflecting surface is in a paraboloid form, and the parabolic equation is as follows: y is2＝4fmAnd x, the paraboloid is formed by rotating a parabola around an x axis, the diameter of the mouth surface is 130mm-180mm, a round hole with the radius approximately equal to the working wavelength of 2.5mm-4mm is formed in the center of the auxiliary reflecting surface, the working frequency of the antenna is 75-110GHz, and the standing wave characteristic of the Cassegrain antenna is improved.
Preferably, the sub-reflecting surface is in the form of a hyperboloid, one focus of the hyperboloid is coincident with a focus of the parabola, and the feed antenna is located at the other focus of the hyperboloid, so that the standing wave characteristic of the cassegrain antenna is further improved.
Preferably, the sub-reflecting surface adopts a conical table, and the curve y of the conical table is 0.5e0.03*x+0.02x, rotating 360 ° around the y axis, the electromagnetic wave irradiates the conical table, and the non-perpendicular irradiation will be reflected to other directions, so it can play the role of reducing the standing wave coefficient of the antenna, and its position is located at the midpoint of the feed antenna and the focus of the main reflection surface 13.
Preferably, the sub-reflecting surface is a circular metal flat plate with the radius of 15mm-25mm, the sub-reflecting surface with the size can be balanced between shielding and diffraction, the processing is simple, compared with a hyperboloid, the processing difficulty is greatly reduced, the cost is saved, the rear lobe level of the antenna can be effectively reduced, and the position of the rear lobe level is located at the midpoint of the focal points of the feed source antenna and the main reflecting surface 13.
Preferably, the cassegrain antenna further comprises a choke groove with the width and the depth of one fourth of the central working wavelength and about 0.8mm, which is called a quarter-wave choke groove, the quarter-wave choke groove is positioned at the edge of the main reflecting surface, and the width and the depth of the quarter-wave choke groove are one fourth of the central working wavelength by grinding and slotting, so that diffraction of electromagnetic waves is effectively reduced, a good inhibiting effect is achieved on the level of a secondary lobe of the antenna, and the level of the secondary lobe is reduced by 3 dB.
Preferably, the feed source antenna is a conical horn, the structure is simple, the feed mode is simple, the wave beam width is moderate, the reflecting surface can be well utilized under a proper distance, and the antenna is a gradually-enlarged waveguide port in structure view and has strong directivity.
Preferably, the main and auxiliary reflecting surface connecting and fixing device adopts three support rods to connect the main reflecting surface and the edge of the auxiliary reflecting surface, and the support rods adopt metal rods with the radius of 0.5mm-1.5mm, so that the device has the characteristics of small shielding and light weight.
Drawings
Embodiments of the invention are described in further detail below with reference to the attached drawing figures, wherein:
FIG. 1 is a diagram of the overall structure of a Cassegrain antenna;
FIG. 2 is a hyperboloid open-cell type secondary reflector of a Cassegrain antenna;
FIG. 3 is a diagram of the secondary reflective surface of a conical frustum of a Cassegrain antenna;
FIG. 4 is a diagram of a cassegrain antenna disk-type subreflector;
FIG. 5 is a diagram of a cassegrain antenna disk aperture-type subreflector;
FIG. 6 is a return loss of a cassegrain antenna subreflector without an aperture;
FIG. 7 shows the return loss of a 2.5mm hole formed in the secondary reflection surface of a Cassegrain antenna;
FIG. 8 shows the return loss of a 4mm hole formed in the secondary reflection surface of a Cassegrain antenna;
FIG. 9 shows the return loss of a Cassegrain antenna by making a 6mm hole in the secondary reflection surface;
FIG. 10 is a diagram (94GHz) of the sub-reflector of the Cassegrain antenna with a 3mm aperture;
FIG. 11 is a diagram (94GHz) of a 6mm aperture opening in the secondary reflector of a Cassegrain antenna;
FIG. 12 is a return loss of the Cassegrain antenna with the subreflector in the form of a frustum;
FIG. 13 is a return loss of a cassegrain antenna subreflector in the form of a disk;
FIG. 14 is the return loss of the cassegrain antenna subreflector in the form of a perforated disc;
FIG. 15 is a directional pattern in the form of an apertured disk of the subreflector of a Cassegrain antenna (94 GHz);
detailed description of the invention
A Cassegrain antenna comprises a feed antenna 11, a main reflecting surface 13, an auxiliary reflecting surface 12 and a main and auxiliary reflecting surface fixing device 15, wherein the main reflecting surface 13 is in a paraboloid form, and the parabolic equation is as follows: y is2＝4fmAnd x, the paraboloid is formed by rotating a parabola around an x axis, the diameter of the mouth surface is 130mm-180mm, a round hole with the radius approximately equal to the working wavelength of 2.5mm-4mm is formed in the center of the auxiliary reflecting surface 12, the working frequency of the antenna is 75-110GHz, and the standing wave characteristic of the Cassegrain antenna is improved.
Preferably, the sub-reflecting surface 12 is in the form of a hyperboloid, one focal point of which coincides with the focal point of a parabola, and the feed antenna 11 is located at the other focal point thereof, so as to further improve the standing wave characteristic of the cassegrain antenna.
Preferably, the sub-reflecting surface 12 adopts a conical table 31, and the curve y of the conical table is 0.5e0.03*x+0.02x, rotating 360 degrees around the y axis, the electromagnetic wave irradiates the conical table, and the non-vertical irradiation will be reflected to other directions, so the function of reducing the standing wave coefficient of the antenna can be achieved, and the position of the electromagnetic wave is located at the midpoint of the focal points of the feed antenna and the main reflecting surface (13).
Preferably, the sub-reflecting surface 12 is a circular metal flat plate 41 with the radius of 15mm-25mm, the sub-reflecting surface with the size can be balanced between shielding and diffraction, the processing is simple, compared with a hyperboloid, the processing difficulty is greatly reduced, the cost is saved, the rear lobe level of the antenna can be effectively reduced, and the position of the rear lobe level is located at the midpoint of the focal points of the feed source antenna and the main reflecting surface (13).
Preferably, the cassegrain antenna further comprises a choke groove 14 with width and depth of one fourth of the central operating wavelength and about 0.8mm, which is called a quarter-wave choke groove, the quarter-wave choke groove 14 is located at the edge of the main reflection surface, and the width and depth of the quarter-wave choke groove 14 are one fourth of the central operating wavelength by grinding and slotting, so that diffraction of electromagnetic waves is effectively reduced, a good suppression effect is achieved on the level of a secondary lobe of the antenna, and the level of the secondary lobe is reduced by 3 dB.
Preferably, the feed source antenna 11 is a conical horn, and has a simple structure, a simple feed mode, and a moderate beam width, and a reflection surface can be well utilized at a proper distance.
Preferably, the main and sub-reflecting surface connecting and fixing device 15 adopts three support rods to connect the edges of the main reflecting surface 13 and the sub-reflecting surface 12, and the support rods adopt metal rods with the radius of 0.5mm-1.5mm, so that the shielding effect is small and the weight is light.
Embodiment 1, a cassegrain antenna, comprising a feed antenna 11, a main reflector 13, an auxiliary reflector 12, and a main and auxiliary reflector fixture 15; wherein the feed antenna 11 is a horn antenna.
The parabolic equation of the main reflecting surface 13 is as follows: y is2＝4fmx, the paraboloid is formed by rotating a parabola around an x axis, and the diameter of the mouth surface is 130-180 mm. The energy of the Cassegrain antenna is converged at the focus of the paraboloid by adopting a paraboloid form and mainly applying the focusing characteristic of the parabola, so that the radiation energy of a measured target is enhanced.
The secondary reflecting surface 12 is in a hyperboloid form, and the hyperboloid equation is as follows:
Figure BDA0002195768640000041
the hyperboloid is formed by rotating the hyperboloid around an x axis, the diameter of the mouth surface is 15-25mm, one focal point of the hyperboloid is coincided with the focal point of the parabola, and the feed source antenna is positioned on the other focal point of the hyperboloid, so that the effect of directly radiating electromagnetic waves from the focal point of the parabola can be achieved.
The cassegrain antenna also includes a choke slot 14, referred to as a quarter-wave choke slot, having a width and depth of one quarter of the center operating wavelength, about 0.8 mm. The quarter-wave choke groove 14 is located at the edge of the main reflecting surface, and the width and the depth of the quarter-wave choke groove are quarter of the central working wavelength by polishing and grooving, so that diffraction of electromagnetic waves is effectively reduced, the level of a secondary lobe of the antenna is well inhibited, and the level of the secondary lobe is reduced by 3 dB.
The feed source antenna 11 is a conical horn which is a horn antenna, and adopts a hollow cone with the radius of 10mm at the bottom edge and the height of 15mm-20mm, and then is connected with a circular tube waveguide with the radius of 2mm for feeding. The antenna has the advantages of simple structure, simple feeding mode, moderate beam width, good utilization of the reflecting surface at a proper distance, and strong directivity due to the fact that the antenna is a gradually-enlarged waveguide port in structure view.
The main and auxiliary reflecting surface connecting and fixing device 15 adopts three supporting rods to connect the edges of the main reflecting surface 13 and the auxiliary reflecting surface 12, and the supporting rods adopt metal rods with the radius of 0.5mm-1.5mm, so that the device has the characteristics of small shielding and light weight.
A round hole with the radius approximately equal to the working wavelength of 2.5mm-4mm is formed in the center of the auxiliary reflecting surface 12, electromagnetic waves are radiated onto the auxiliary reflecting surface, reflection is not generated at the center, reflection of the antenna can be effectively reduced, return loss of a rear lobe and the antenna is reduced, the return loss of the antenna is smaller than 20dB, gain is improved to 39.5dB, the return loss of the rear lobe is reduced by 8.6dB, holes are not formed, the holes are formed by 2.5mm and 4mm 6mm, return loss of the holes is formed by 3mm and 6mm directional diagrams, and the directional diagrams are shown in figures 6-11.
Example 2, the sub-reflecting surface 12 of example 1 uses a tapered table 31, the curve y of which is 0.5e0.03*x+0.02x, formed by a rotation of 360 about the y-axis,the antenna has the advantages that the antenna can reduce the standing wave coefficient of the antenna, the position of the antenna is located at the middle point of the focal points of the feed antenna and the main reflecting surface 13, electromagnetic waves are radiated to the auxiliary reflecting surface from the conical horn 11, the vertical reflection of the electromagnetic waves can be avoided due to the fact that the antenna is opposite to the frustum 31 at a certain angle, and the effect of reducing the return loss of the antenna to be less than 20dB can be achieved, as shown in fig. 12.
In embodiment 3, the sub-reflecting surface 12 described in embodiment 1 is a circular metal flat plate 41 with a radius of 15mm to 25mm, and the position of the circular metal flat plate is located at the midpoint of the focal points of the feed antenna and the main reflecting surface 13, so that the processing is simple, compared with a hyperboloid, the processing difficulty is greatly reduced, the cost is saved, the antenna characteristics are slightly reduced, but still acceptable, and the return loss of the antenna is less than 18dB, as shown in fig. 13.
In example 4, a circular hole 51 with a radius of 2.5mm to 4mm is formed in the middle of the sub-reflecting surface 12 in example 1, and the circular hole is located at the midpoint of the focal points of the feed antenna and the main reflecting surface 13, so that the processing is simple, compared with a hyperboloid, the processing difficulty is greatly reduced, the cost is saved, and the back lobe of the antenna can be effectively reduced.
By implementing the invention, the return loss of the Cassegrain antenna can be effectively reduced, the optimal effect is less than-20 dB, the gain of the antenna is effectively increased, the maximum gain is 39.3dB, the back lobe level is reduced by 9.3dB, and the side lobe level is reduced.
It is to be noted that all other embodiments obtained by a person skilled in the art based on the embodiments of the present invention without any inventive step are within the scope of the present invention.

Claims (7)

1. A Cassegrain antenna comprises a feed source antenna (11), a main reflecting surface (13), an auxiliary reflecting surface (12) and a main and auxiliary reflecting surface fixing device (15), wherein the main reflecting surface (13) is in a paraboloid form, and the parabolic equation is as follows: y is2＝4fmx, paraboloid of revolution about x-axis by parabolaThe diameter of the mouth surface is 130mm-180mm, and the antenna is characterized in that a round hole with the radius equal to 2.5mm-4mm of the working wavelength is formed in the center of the sub-reflecting surface (12), and the working frequency of the antenna is 75-110 GHz.
2. Cassegrain antenna according to claim 1, characterized in that the secondary reflecting surface (12) takes the form of a hyperboloid, one focal point of which coincides with the parabolic focal point, the feed antenna (11) being located at its other focal point.
3. Cassegrain antenna according to claim 1, characterized in that the subreflector (12) is a cone-shaped platform (31) having a curve y of 0.5e0.03*x+0.02x, formed by a 360 ° rotation around the y-axis, at the midpoint of the feed antenna and the focal point of the main reflecting surface (13).
4. Cassegrain antenna according to claim 1, characterised in that the subreflector (12) is a circular metal plate (41) with a radius of 15mm to 25mm and is positioned at the midpoint of the focal points of the feed antenna and the main reflector (13), the subreflector being of such a size as to balance the shadowing and diffraction.
5. Cassegrain antenna according to claim 1, 2, 3 or 4, characterized in that it further comprises a choke groove (14), called quarter-wave choke groove, of width and depth of one quarter of the central operating wavelength, about 0.8mm, said quarter-wave choke groove (14) being located at the edge of the main reflecting surface, the width and depth of which is one quarter of the central operating wavelength by grinding the slot.
6. Cassegrain antenna according to claim 1, 2, 3 or 4, characterized in that the feed antenna (11) is a conical horn.
7. Cassegrain antenna according to claim 1, characterized in that the main and secondary reflecting surface connection fixing means (15) use three support rods to connect the main reflecting surface (13) and the edge of the secondary reflecting surface (12), the support rods being metal rods with a radius of 0.5mm-1.5 mm.
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3983560A (en) * 1974-06-06 1976-09-28 Andrew Corporation Cassegrain antenna with improved subreflector for terrestrial communication systems
CN2610506Y (en) * 2003-03-31 2004-04-07 北京科迪安科技有限公司 Improved small aperture deformed cassegrain antenna
CN104124533A (en) * 2013-04-28 2014-10-29 深圳国人通信有限公司 Backward-feedback type reflector antenna
CN104767036A (en) * 2015-05-05 2015-07-08 中国电子科技集团公司第五十四研究所 Design method for secondary mirror for increasing bimirror antenna gains
US20170229773A1 (en) * 2009-06-04 2017-08-10 Jude Lee Antenna isolation shrouds and reflectors

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3983560A (en) * 1974-06-06 1976-09-28 Andrew Corporation Cassegrain antenna with improved subreflector for terrestrial communication systems
CN2610506Y (en) * 2003-03-31 2004-04-07 北京科迪安科技有限公司 Improved small aperture deformed cassegrain antenna
US20170229773A1 (en) * 2009-06-04 2017-08-10 Jude Lee Antenna isolation shrouds and reflectors
CN104124533A (en) * 2013-04-28 2014-10-29 深圳国人通信有限公司 Backward-feedback type reflector antenna
CN104767036A (en) * 2015-05-05 2015-07-08 中国电子科技集团公司第五十四研究所 Design method for secondary mirror for increasing bimirror antenna gains

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
HAO LIU、ALEXANDER DENISOV、HUA ZONG、SHU LIN: "Design and analysis of a cassegrain antenna with an annular sub-reflector", 《2016 IEEE INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION (APSURSI)》 *

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Application publication date: 20200207