US3706999A - Cassegraninian antenna having limited spillover energy - Google Patents

Cassegraninian antenna having limited spillover energy Download PDF

Info

Publication number
US3706999A
US3706999A US174600A US3706999DA US3706999A US 3706999 A US3706999 A US 3706999A US 174600 A US174600 A US 174600A US 3706999D A US3706999D A US 3706999DA US 3706999 A US3706999 A US 3706999A
Authority
US
United States
Prior art keywords
antenna
deflector
secondary reflector
ground
spillover
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US174600A
Inventor
Yves Tocquec
Andre Rabadeux
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Alcatel CIT SA
Original Assignee
Compagnie Industrielle de Telecommunication CIT Alcatel SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Compagnie Industrielle de Telecommunication CIT Alcatel SA filed Critical Compagnie Industrielle de Telecommunication CIT Alcatel SA
Application granted granted Critical
Publication of US3706999A publication Critical patent/US3706999A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
    • H01Q19/02—Details
    • H01Q19/021—Means for reducing undesirable effects
    • H01Q19/026—Means for reducing undesirable effects for reducing the primary feed spill-over

Definitions

  • ABSTRACT A deflector is fixed relative to coaxial main and secondary antenna reflectors, after said secondary reflector and between the ground and the axis of the antenna to intercept parasitic radiation spillover.
  • the harmful effect of thisspillover energy causes a deterioration of the gain of the antenna and a lowering of the quality factor which depends upon this gain and upon the noise temperature of the ground and of the sky.
  • the noise temperature of the ground is constant and high. That of the sky, which is variable, depends upon the angle of elevation of the antenna system in relation to the ground. The temperature of the sky increases as the angle of elevation decreases. Nevertheless, at frequencies of the order of 5 Gc/s and at elevations as low as 5, the temperature of the ground is greater than that of the sky.
  • the method generally employed to combat this coupling consists in covering the ground around the antenna by a metallic grating.
  • This reflecting grating which forms a screen, stops the radiation from the ground in the direction of the antenna and the spillover portion of the lobe of this antenna is sent back to the sky, where the luminance temperatures are low.
  • the grating can be employed only with antennas of small dimensions, because the surface to be covered is then only of a few square meters.
  • the grating system is applicable only at low frequencies, because the meshes can be loose at these temperatures.
  • the arrangement according to the invention makes it possible to obviate these disadvantages, since it is possible therein to reduce the coupling between the spillover energy and the ground by means of a simple system occupying a small amount of space.
  • the invention relates to a Cassegrainian antenna for microwave electromagnetic radiation, comprising, in this order, a main reflector, a source of excitation which transmits or receives a radiation lobe, and a secondary reflector coaxial with the said main reflector and receiving on its reflecting face a portion of the said radiation lobe, a spillover portion of the lobe being directed, in certain low positions, from the axis of the antenna in the direction of the ground and thus producing the parasitic spillover coupling through the ground, characterized by the fact that the antenna comprises in addition an electrically conductive deflector which is fast with the said secondary reflector, the said deflector being disposed after the said secondary reflector, on the side remote from he reflecting face of the said secondary reflector, in the space between the ground and the said axis of the antenna, in such manner as to intercept the said spillover portion.
  • the antenna is characterized by the fact that the said deflector comprises a plane surface which is at an angle of about 45 to the said axis of the antenna.
  • FIG. 1 is a geometrical optical diagram of a Cassegrainian antenna provided with a deflector according to the invention.
  • FIG. 2 is a diagrammatic view in perspective of a secondary reflector of a Cassegrainian antenna and of the deflector according to the invention.
  • FIG. 1 there will be seen meridians of the main reflector 1 and of the secondary reflector 2 of a Cassegrainian antenna.
  • the main reflector is a paraboloid about 30 meters in diameter and the secondary reflector is a hyperboloid whose diameter is one-tenth as large.
  • the two reflectors are of like focus: F1 represents the focus of the paraboloid and one of the foci of the hyperboloid, and F2 represents the other focus of the hyperboloid.
  • the transmission source of the antenna is disposed at F2.
  • the electromagnetic energy in the form of a lobe (not shown) is radiated from the source in the direction of the secondary reflector 2.
  • a portion of the spillover energy is not intercepted by the secondary reflector 2.
  • a deflector 3 performing the function of a plane mirror is disposed at the level of the secondary reflector 2.
  • the plane of the deflector 3 forms with the axis of symmetry 4 of the Cassegrainian antenna an angle of about 45.
  • a ray 5 emanating from the source is first reflected by the secondary reflector 2 and then by the principal reflector 1. This ray can thereafter take a direction parallel to the axis 4 of the antenna. Conversely, when the antenna operates in reception, the path traveled by the ray is the same but of opposite direction.
  • the deflector 3 is particularly advantageous at low elevations at the anl060ll 0249 tenna, i.e. at the angles formed by the axis of symmetry 4 with the plane of the ground 7 between 5 and The deflector 3 is disposed between the ground 7 and the axis of symmetry 4 of the antenna. In order to avoid an increase of the masking effect caused by the secondary reflector and in order to permit ready fixing, the deflector 3 is set back from the secondary reflector 2.
  • the trace of the plane of the deflector 3 does not extend beyond the extension of the meridian of the secondary reflector 2.
  • FIG. 2 there is shown a perspective view of the secondary reflector 2 and of the deflector 3.
  • the deflector 3 is of substantially square form, the dimensions'bein'g approximately equal to the diameter of the secondary reflector 2.
  • a trapezoidal recess 7 opens into the interior of the square surface of the deflector 3, which consists of a metallic plate made of an alloy of aluminum, zinc and magnesium known under the trade name AG 5. Owing to the recess 7, the weight of the deflector may be reduced to about 100 kg.
  • the recess 7 is masked by the secondary reflector 2 from the rays coming from the source. This recess does not interfere with the reflection of the rays 6 corresponding to the spillover energy directed directed towards the ground.
  • the plate of the deflector 3 is secured by means of a I series of bolts such as 9 and 10 to a right-angled member 8 attached to beams (not shown).
  • rods 11 and 12 connected to two ends of the plate of the deflector 3 abut two points of the right-angled member 8.
  • rods 13 and 14 are connected by rods 13 and 14 to beams (not shown) which support the secondary reflector 2.
  • the arrangement according to the invention may be employed in all cases where a Cassegrainian antenna operating at low elevations produces a coupling of the spillover energy with the ground.
  • Particularly interesting applications may be in the field of telecommunications by satellites in the band from 4 to 6 Gc/s.
  • a Cassegrainian antenna for microwave electromagnetic radiation, including, in this order, a main reflector, a source of excitation which transmits or receives a radiation lobe, a secondary reflector coaxial with the said main reflector and receiving on its reflecting face a part of the said radiation lobe, a spillover portion of the lobe being directed, in certain low positions, from the axis of the antenna in the direction of the ground, thus producing the parasitic spillover coupling through the ground
  • the antenna comprises in addition an electrically conductive deflector fixed relative to said secondary reflector, said deflector being disposed after the said secondary reflector, on the side remote from the reflecting face of the said secondary reflector in the s ace situated betw en the ground and the said axis of t e antenna, in suc manner as to intercept the said spillover portion.
  • said deflector comprises a plane surface which forms an angle of about 45 with said axis of the antenna.

Abstract

A deflector is fixed relative to coaxial main and secondary antenna reflectors, after said secondary reflector and between the ground and the axis of the antenna to intercept parasitic radiation spillover.

Description

United States Patent Tocquec et al.
[451 Dec. 19, 1972 CASSEGRANINIAN ANTENNA HAVING LIMITED SPILLOVER ENERGY Inventors: Yves Tocquec, Marcoussis; Andre Rabadeux, Palaiseau, both of France lndustrielle Des Cit-Alcetel,
Campagnle Telecommunications Paris, France Filed: Aug. 25, 1971 Appl. No.: 174,600
Assignee:
Foreign Application Priority Data Aug. 28, 1970 France "7031536 US. Cl ..343/7s2, 343/837 1m. Cl. ..l-l01q 19/14 [58] Field 01 Search ..343/781, 782, 833, 837
[56] References Cited UNITED STATES PATENTS 3,209,361 9/1965 Webb, ..343/781 3,430,244 2/1969 Bartlett et a1 ..343/781 X 3,530,476 9/1970 Ravenscroft ..343/837 X Primary Examiner-Stanley D. Miller, Jr. Attorney-Richard C. Sughrue et al.
[5 7] ABSTRACT A deflector is fixed relative to coaxial main and secondary antenna reflectors, after said secondary reflector and between the ground and the axis of the antenna to intercept parasitic radiation spillover.
4 Claims, 2 Drawing Figures l x 2 1 a" l I I l I CASSEGRANINIAN ANTENNA HAVING LIMITED SPILLOVER ENERGY BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION The present invention concerns a Cassegrainian antenna which is so improved that its spillover energy is limited.
2. DESCRIPTION OF THE PRIOR ART Cassegrainian antennas for electromagnetic waves are known, which consist of a main reflector, which may be parabolic or pseudo-parabolic, of a pseudohyperbolic or elliptical secondary reflector and of a source of excitation whose transmission or reception pattern is directed towards the secondary reflector.
It is known that an important factor in the impairment of the performances of antennas of this type is the loss due to spillover energy. The transmission energy does not entirely reach'the secondary reflector and a part may fall to the ground.
The harmful effect of thisspillover energy causes a deterioration of the gain of the antenna and a lowering of the quality factor which depends upon this gain and upon the noise temperature of the ground and of the sky. The noise temperature of the ground is constant and high. That of the sky, which is variable, depends upon the angle of elevation of the antenna system in relation to the ground. The temperature of the sky increases as the angle of elevation decreases. Nevertheless, at frequencies of the order of 5 Gc/s and at elevations as low as 5, the temperature of the ground is greater than that of the sky.
It is mainly at low elevations that the coupling of the spillover energy with the ground is maximum.
The method generally employed to combat this coupling consists in covering the ground around the antenna by a metallic grating. This reflecting grating, which forms a screen, stops the radiation from the ground in the direction of the antenna and the spillover portion of the lobe of this antenna is sent back to the sky, where the luminance temperatures are low. However, the grating can be employed only with antennas of small dimensions, because the surface to be covered is then only of a few square meters. Moreover, the grating system is applicable only at low frequencies, because the meshes can be loose at these temperatures. In the case of large antennas operating at high frequencies, the cost of such gratings and the space occupied thereby become prohibitive, it being necessary for the grating to extend over lengths of hundreds of meters and for the meshes to be close together so as to exhibit a spacing of the order of a centimeter.
SUMMARY OF THE INVENTION The arrangement according to the invention makes it possible to obviate these disadvantages, since it is possible therein to reduce the coupling between the spillover energy and the ground by means of a simple system occupying a small amount of space.
The invention relates to a Cassegrainian antenna for microwave electromagnetic radiation, comprising, in this order, a main reflector, a source of excitation which transmits or receives a radiation lobe, and a secondary reflector coaxial with the said main reflector and receiving on its reflecting face a portion of the said radiation lobe, a spillover portion of the lobe being directed, in certain low positions, from the axis of the antenna in the direction of the ground and thus producing the parasitic spillover coupling through the ground, characterized by the fact that the antenna comprises in addition an electrically conductive deflector which is fast with the said secondary reflector, the said deflector being disposed after the said secondary reflector, on the side remote from he reflecting face of the said secondary reflector, in the space between the ground and the said axis of the antenna, in such manner as to intercept the said spillover portion.
In accordance with one feature of the invention, the antenna is characterized by the fact that the said deflector comprises a plane surface which is at an angle of about 45 to the said axis of the antenna.
BRIEF DESCRIPTION OF THE DRAWINGS Referring to the diagrammatic figures, there will now be described an example of the application of the present invention, this example being intended purely for illustration and having no limiting character. In these two figures, like elements are denoted by like references throughout.
FIG. 1 is a geometrical optical diagram of a Cassegrainian antenna provided with a deflector according to the invention.
FIG. 2 is a diagrammatic view in perspective of a secondary reflector of a Cassegrainian antenna and of the deflector according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, there will be seen meridians of the main reflector 1 and of the secondary reflector 2 of a Cassegrainian antenna. The main reflector is a paraboloid about 30 meters in diameter and the secondary reflector is a hyperboloid whose diameter is one-tenth as large. The two reflectors are of like focus: F1 represents the focus of the paraboloid and one of the foci of the hyperboloid, and F2 represents the other focus of the hyperboloid. The transmission source of the antenna is disposed at F2. The electromagnetic energy in the form of a lobe (not shown) is radiated from the source in the direction of the secondary reflector 2. A portion of the spillover energy is not intercepted by the secondary reflector 2. A deflector 3 performing the function of a plane mirror is disposed at the level of the secondary reflector 2. The plane of the deflector 3 forms with the axis of symmetry 4 of the Cassegrainian antenna an angle of about 45. In accordance with the laws of geometrical optics, a ray 5 emanating from the source is first reflected by the secondary reflector 2 and then by the principal reflector 1. This ray can thereafter take a direction parallel to the axis 4 of the antenna. Conversely, when the antenna operates in reception, the path traveled by the ray is the same but of opposite direction.
In the case where a radiated energy spillover is considered, the ray 6 not passing through the secondary reflector 2 and directed in the direction of the ground 7 is intercepted by the deflector 3. The ray 6 is thereafter reflected towards the sky. Coupling of the spillover energy with the ground is thereby avoided. It may be observed that the deflector according to the invention is particularly advantageous at low elevations at the anl060ll 0249 tenna, i.e. at the angles formed by the axis of symmetry 4 with the plane of the ground 7 between 5 and The deflector 3 is disposed between the ground 7 and the axis of symmetry 4 of the antenna. In order to avoid an increase of the masking effect caused by the secondary reflector and in order to permit ready fixing, the deflector 3 is set back from the secondary reflector 2.
The trace of the plane of the deflector 3 does not extend beyond the extension of the meridian of the secondary reflector 2.
In FIG. 2, there is shown a perspective view of the secondary reflector 2 and of the deflector 3. The deflector 3 is of substantially square form, the dimensions'bein'g approximately equal to the diameter of the secondary reflector 2. A trapezoidal recess 7 opens into the interior of the square surface of the deflector 3, which consists of a metallic plate made of an alloy of aluminum, zinc and magnesium known under the trade name AG 5. Owing to the recess 7, the weight of the deflector may be reduced to about 100 kg.
The recess 7 is masked by the secondary reflector 2 from the rays coming from the source. This recess does not interfere with the reflection of the rays 6 corresponding to the spillover energy directed directed towards the ground.
The plate of the deflector 3 is secured by means of a I series of bolts such as 9 and 10 to a right-angled member 8 attached to beams (not shown). In order to counteract the forces due to the wind, rods 11 and 12 connected to two ends of the plate of the deflector 3 abut two points of the right-angled member 8. Likewise, two other ends of the plate of the deflector 3 are connected by rods 13 and 14 to beams (not shown) which support the secondary reflector 2.
Although the arrangement just described appears to be the most advantageous, it will be appreciated that various modifications may be made thereto without departing from the scope of the invention, it being possible for some of the elements of the arrangement to be replaced by others capable of performing the same technical function therein.
The arrangement according to the invention may be employed in all cases where a Cassegrainian antenna operating at low elevations produces a coupling of the spillover energy with the ground.
Particularly interesting applications may be in the field of telecommunications by satellites in the band from 4 to 6 Gc/s.
What is claimed is:
1. In a Cassegrainian antenna for microwave electromagnetic radiation, including, in this order, a main reflector, a source of excitation which transmits or receives a radiation lobe, a secondary reflector coaxial with the said main reflector and receiving on its reflecting face a part of the said radiation lobe, a spillover portion of the lobe being directed, in certain low positions, from the axis of the antenna in the direction of the ground, thus producing the parasitic spillover coupling through the ground, the improvement wherein the antenna comprises in addition an electrically conductive deflector fixed relative to said secondary reflector, said deflector being disposed after the said secondary reflector, on the side remote from the reflecting face of the said secondary reflector in the s ace situated betw en the ground and the said axis of t e antenna, in suc manner as to intercept the said spillover portion.
2. The antenna according to claim 1, wherein said deflector comprises a plane surface which forms an angle of about 45 with said axis of the antenna.
3. The antenna according to claim 2, wherein the plane surface of the deflector has an approximately square form within which lies a trapezoidal recess.
4. The antenna according to claim 2, wherein the overall dimensions of said plane surface are substantially equal to the diameter of said secondary reflector.
* s: a a
l060ll 0250

Claims (4)

1. In a Cassegrainian antenna for microwave electromagnetic radiation, including, in this order, a main reflector, a source of excitation which transmits or receives a radiation lobe, a secondary reflector coaxial with the said main reflector and receiving on its reflecting face a part of the said radiation lobe, a spillover portion of the lobe being directed, in certain low positions, from the axis of the antenna in the direction of the ground, thus producing the parasitic spillover coupling through the ground, the improvement wherein the antenna comprises in addition an electrically conductive deflector fixed relative to said secondary reflector, said deflector being disposed after the said secondary reflector, on the side remote from the reflecting face of the said secondary reflector in the space situated between the ground and the said axis of the antenna, in such manner as to intercept the said spillover portion.
2. The antenna according to claim 1, wherein said deflector comprises a plane surface which forms an angle of about 45* with said axis of the antenna.
3. The antenna according to claim 2, wherein the plane surface of the deflector has an approximately square form within which lies a trapezoidal recess.
4. The antenna according to claim 2, wherein the overall dimensions of said plane surface are substantially equal to the diameter of said secondary reflector.
US174600A 1970-08-28 1971-08-25 Cassegraninian antenna having limited spillover energy Expired - Lifetime US3706999A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7031536A FR2101144B1 (en) 1970-08-28 1970-08-28

Publications (1)

Publication Number Publication Date
US3706999A true US3706999A (en) 1972-12-19

Family

ID=9060697

Family Applications (1)

Application Number Title Priority Date Filing Date
US174600A Expired - Lifetime US3706999A (en) 1970-08-28 1971-08-25 Cassegraninian antenna having limited spillover energy

Country Status (6)

Country Link
US (1) US3706999A (en)
BE (1) BE771448A (en)
DE (1) DE2141047A1 (en)
FR (1) FR2101144B1 (en)
LU (1) LU63757A1 (en)
NL (1) NL7111608A (en)

Cited By (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
US6611238B1 (en) 2001-11-06 2003-08-26 Hughes Electronics Corporation Method and apparatus for reducing earth station interference from non-GSO and terrestrial sources
US6778810B1 (en) 1999-12-03 2004-08-17 The Directtv Group, Inc. Method and apparatus for mitigating interference from terrestrial broadcasts sharing the same channel with satellite broadcasts using an antenna with posterior sidelobes
US6975837B1 (en) 2003-01-21 2005-12-13 The Directv Group, Inc. Method and apparatus for reducing interference between terrestrially-based and space-based broadcast systems
US7369809B1 (en) 2000-10-30 2008-05-06 The Directv Group, Inc. System and method for continuous broadcast service from non-geostationary orbits

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2920781C2 (en) * 1979-05-22 1984-07-12 Siemens AG, 1000 Berlin und 8000 München Reflector antenna, consisting of a main reflector, a primary radiator and a subreflector
DE2954351C2 (en) * 1979-05-22 1986-07-17 Siemens AG, 1000 Berlin und 8000 München Reflector antenna

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3209361A (en) * 1963-01-14 1965-09-28 James E Webb Cassegrainian antenna subreflector flange for suppressing ground noise
US3430244A (en) * 1964-11-25 1969-02-25 Radiation Inc Reflector antennas
US3530476A (en) * 1966-07-04 1970-09-22 Post Office Multiple reflector antenna with offset feed

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3209361A (en) * 1963-01-14 1965-09-28 James E Webb Cassegrainian antenna subreflector flange for suppressing ground noise
US3430244A (en) * 1964-11-25 1969-02-25 Radiation Inc Reflector antennas
US3530476A (en) * 1966-07-04 1970-09-22 Post Office Multiple reflector antenna with offset feed

Cited By (9)

* 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
US6778810B1 (en) 1999-12-03 2004-08-17 The Directtv Group, Inc. Method and apparatus for mitigating interference from terrestrial broadcasts sharing the same channel with satellite broadcasts using an antenna with posterior sidelobes
US20040235418A1 (en) * 1999-12-03 2004-11-25 Anderson Paul R. Method and apparatus for mitigating interference from terrestrial broadcasts sharing the same channel with satellite broadcasts using an antenna with posterior sidelobes
US7257370B2 (en) 1999-12-03 2007-08-14 The Directv Group, Inc. Method and apparatus for mitigating interference from terrestrial broadcasts sharing the same channel with satellite broadcasts using an antenna with posterior sidelobes
US20090004967A1 (en) * 1999-12-03 2009-01-01 Anderson Paul R Method and apparatus for mitigating interference from terrestrial broadcasts sharing the same channel with satellite broadcasts using an antenna with posterior sidelobes
US7917080B2 (en) 1999-12-03 2011-03-29 The Directv Group, Inc. Method and apparatus for mitigating interference from terrestrial broadcasts sharing the same channel with satellite broadcasts using an antenna with posterior sidelobes
US7369809B1 (en) 2000-10-30 2008-05-06 The Directv Group, Inc. System and method for continuous broadcast service from non-geostationary orbits
US6611238B1 (en) 2001-11-06 2003-08-26 Hughes Electronics Corporation Method and apparatus for reducing earth station interference from non-GSO and terrestrial sources
US6975837B1 (en) 2003-01-21 2005-12-13 The Directv Group, Inc. Method and apparatus for reducing interference between terrestrially-based and space-based broadcast systems

Also Published As

Publication number Publication date
LU63757A1 (en) 1972-04-04
FR2101144B1 (en) 1973-11-23
BE771448A (en) 1972-02-18
DE2141047A1 (en) 1972-03-02
FR2101144A1 (en) 1972-03-31
NL7111608A (en) 1972-03-01

Similar Documents

Publication Publication Date Title
US4626863A (en) Low side lobe Gregorian antenna
US3448455A (en) Armoured structure antenna
Love Some highlights in reflector antenna development
US4673945A (en) Backfire antenna feeding
US3430244A (en) Reflector antennas
US4282530A (en) Cylindrical paraboloid weather cover for a horn reflector antenna with wave absorbing means
US4096483A (en) Reflector with frequency selective ring of absorptive material for aperture control
US3733609A (en) Shrouded offset parabolic reflector antenna
US3706999A (en) Cassegraninian antenna having limited spillover energy
US3176301A (en) Plural horns at focus of parabolic reflector with shields to reduce spillover and side lobes
US3810187A (en) Capped antenna of the offset cassegrainian type
US4777491A (en) Angular-diversity radiating system for tropospheric-scatter radio links
US3530480A (en) Cassegrain antenna having dielectric supporting structure for subreflector
US3696436A (en) Cassegrain antenna with absorber to reduce back radiation
US4521783A (en) Offset microwave feed horn for producing focused beam having reduced sidelobe radiation
US4783664A (en) Shaped offset-fed dual reflector antenna
US3122745A (en) Reflection antenna employing multiple director elements and multiple reflection of energy to effect increased gain
US4356494A (en) Dual reflector antenna
JP2687412B2 (en) Reflector antenna
JP2687413B2 (en) Reflector antenna
EP0136817A1 (en) Low side lobe gregorian antenna
RU2795755C1 (en) Method for reducing the noise temperature of multibeam two-mirror antennas with a shifted focal axis
JPH09312518A (en) Dual reflection mirror antenna system
JP2687415B2 (en) Reflector antenna
JP2687414B2 (en) Reflector antenna