CA1197613A - Antenna feeding with selectively controlled polarization - Google Patents
Antenna feeding with selectively controlled polarizationInfo
- Publication number
- CA1197613A CA1197613A CA000429307A CA429307A CA1197613A CA 1197613 A CA1197613 A CA 1197613A CA 000429307 A CA000429307 A CA 000429307A CA 429307 A CA429307 A CA 429307A CA 1197613 A CA1197613 A CA 1197613A
- Authority
- CA
- Canada
- Prior art keywords
- improvement
- accordance
- dipole antenna
- waveguide
- dipole
- 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
Links
- 230000010287 polarization Effects 0.000 title claims description 19
- 239000004020 conductor Substances 0.000 claims abstract description 11
- 239000000523 sample Substances 0.000 claims abstract description 5
- 238000005286 illumination Methods 0.000 claims description 9
- 230000005540 biological transmission Effects 0.000 claims description 6
- 230000005855 radiation Effects 0.000 claims description 6
- 230000008878 coupling Effects 0.000 claims description 5
- 238000010168 coupling process Methods 0.000 claims description 5
- 238000005859 coupling reaction Methods 0.000 claims description 5
- 230000004323 axial length Effects 0.000 claims description 2
- 230000001154 acute effect Effects 0.000 claims 1
- 230000002463 transducing effect Effects 0.000 claims 1
- 239000002184 metal Substances 0.000 abstract description 9
- 230000001902 propagating effect Effects 0.000 abstract 1
- 230000009977 dual effect Effects 0.000 description 5
- 238000000034 method Methods 0.000 description 4
- 238000010276 construction Methods 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 239000004809 Teflon Substances 0.000 description 2
- 229920006362 Teflon® Polymers 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 229920003223 poly(pyromellitimide-1,4-diphenyl ether) Polymers 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 244000118350 Andrographis paniculata Species 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 229920001721 polyimide Polymers 0.000 description 1
- 230000002618 waking effect Effects 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q21/00—Antenna arrays or systems
- H01Q21/24—Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction
- H01Q21/245—Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction provided with means for varying the polarisation
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q13/00—Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
- H01Q13/06—Waveguide mouths
- H01Q13/065—Waveguide mouths provided with a flange or a choke
Abstract
ABSTRACT OF THE DISCLOSURE
A flat face annular grooved metal surface sur-rounds a circular waveguide opening coupled to a small dipole radiator which excites the circular waveguide in its fundamental propagating mode (TE11). The dipole is arranged to rotate about its axis by means of an ex-tension of its inner conductor, which forms a simple probe in a section of rectangular waveguide situated behind the circular waveguide. A dielectric shaft is fastened to the inner conductor and is brought to the outside of the rectangular waveguide where it is con-nected to a small motor. The motor is arranged so that it may be actuated remotely by any of several circuits.
The dipole may be before the corrugated plate with bent arms. A pair of dipoles may be arranged perpendicular to each other with two separate coaxial connector antenna feed outputs for direct attachment to coaxial-type low-noise amplifiers.
A flat face annular grooved metal surface sur-rounds a circular waveguide opening coupled to a small dipole radiator which excites the circular waveguide in its fundamental propagating mode (TE11). The dipole is arranged to rotate about its axis by means of an ex-tension of its inner conductor, which forms a simple probe in a section of rectangular waveguide situated behind the circular waveguide. A dielectric shaft is fastened to the inner conductor and is brought to the outside of the rectangular waveguide where it is con-nected to a small motor. The motor is arranged so that it may be actuated remotely by any of several circuits.
The dipole may be before the corrugated plate with bent arms. A pair of dipoles may be arranged perpendicular to each other with two separate coaxial connector antenna feed outputs for direct attachment to coaxial-type low-noise amplifiers.
Description
~37~
ANTENNA FEEDING WITH SELECTIVELY CONTROLLED POLARIZATION
The presen-t lnvention relates in general to an-tenna feeding with selective ,polarization and more particularly concerns novel apparatus and -techniques for 5 llluminating a deep paraboloid reflector with a cor-rugated face antenna -Eeed with selec-tively controlled polarization using mechanical elements of relatively low inertia easily driven by a small motor of such low power that it may be energized from the D.C. power supply of an 10 associated receiver.
Earth stations for reception of satellite sig-nals presently use the 3.7-4.2 GHz frequency band and require reflector antennas having diameters of 8 to 20 fee-t. To achieve nigh gain and low noise qualities from 15 these antennas, prior techniques have used (among others), simple corrugated face feeds exci-ted by the fun-damental mode of a circular waveguide. These types of feeds are well-known for producing good performance in these installations because they efficiently illuminate 20 reflectors having focal length-to-diameter (F/D) ratios of about 0.4 and larger, while reducing electrical noise pickup from the ear-th or frorn nearby in-terfering trans-mi-t-ters. zany present antenna reflectors use F/D ratios as srnall as 0.25, thus,creat;ing problems in attaining 25 efficient illumination and high gain.
However, these feeds must be rotate in their entirety together with any connected ~uxlliaryiequipmen-t, such as the low noise amplifier (~NA?, -to adjus-t the ..
j polarization angle. Presen-t clomes-tic sa-tellites use transponders having or-thogonal linear polariza-tion. The apparent polarization (that is, the polarixation angle as measured from the vertical at the earth Station) of the 5 satellite as seen from the earth sta-tion varies con-siderably depending on the location of the ear-th station and the position of the satelli-te's sta-tionary orbit.
Ro-tating the entire feed and LNA causes severe practical problems with cable wrap-ups and alignment ox the feed 10 with respect to -the focal poin-t of the reflec-tor. Both o-f these problems cause loss of signal and reliability degradation. Also, for those earth station installations which are configured to receive bo-th simultaneous orthogonal polarizatlons a relatively expensive device 15 known as an or-tho-mode transducer is required to be con-nected to the feed to separate the -two signals into two waveguide ports.
Accordingly, it is an impor-tant object of this $ invention to provide a device which permits remote rota-20 tion of the polarization angle of the an-tenna feed without the above disadvantages, and with only one moving part, while utilizing the proven qualities of the cor-rugated face.
A further object of this invention is to permit 25 efficient illumination of deep reflectors (in the range of 0.25-0.35 F/D ratios with -the simultaneous ability to remotely adjust the polarization angle, if desired.
I-t is a still further object of this invention to provide means for achieving the dual polariza-tion 30 capability with coaxial-type LNA's while also achieving the advantages of efficient illumination for deep re-flec-tors.
It is a further object of the invention to pro-vide the above objects wi-th a device which is compac-t, 35 simple in construction, lightweight, low cost, weather resistant, and which fixes the feed body and the LNA, thus obviating cable wraps and alignment problems.
Accoxding to the inven-tion, there is a corrugated face metal plate surrounded by a circular wavegulde opening excited by rotatable polarized antenna means polarized in a predetermined direction, such as a dipole or dipole pair.
In the case of the slngle dipole, remote means of polariza-tion adjustment àre afforded by extending the inner conduc-tor of the dipole into a rectangular waveguide placed behind the circular waveguide so as to excite it in its fundamental TEol propagation mode. There is means, such as a dielectric shaft connected between the inner conductor and the shaft of a small motor or other actuator, for selectively rotating the polarized radiating means. The depth of the circular waveguide cavity and the consequent axial position of the dipole is preferably adjusted for optimum illumination of a given F/D-ratio reflector. According to another feature of the invention, a pair of crossed dipoles with coaxial-LNA's provide dual polarized operation.
According to a further broad aspect of the present invention there is provided in an antenna feed having a corrugated surface concentric about the axis of an adjacent circular waveguide having an open end and a closed end formed with a central opening an improvement comprising polarized dipole antenna means polarized in a predetermined direction rotatably mounted about the axis and coupled to the circular waveguide and spaced from the circular waveguide closed end. Means is provided for rotatably supporting the antenna means for rotation about the axis. An output wave-guide means is provided for exchanging energy with the dipole antenna means through the central opening. Means is provided for coupling the dipole antenna means to the output waveguide means through the central opening comprising an insulating mechanical bearing sleeve seated in the central opening and a coaxial transmission line seated in the sleeve connected to the dipole antenna means and incIuding a coaxial impedance transformer for improving the impedance match between the dipole antenna means and the output waveguide means. Means is provided for rotating the assembly to, 7~13 3a and comprising the coaxial transmission line and the dipole antenna means to selectively control the polarization oE
the antenna feed about the axis. The axial length of the central opening is substantially a quarter wavelength and the dipole antenna means includes at least one pair of arms each substantially a quarter wavelength long extending radially outward from the axis. The distance between the arms and the closed end is substantially a quarter wave-length.
Numerous other features, objects and advantages of the invention will become apparent from the following specification when read in connection with the accompany-ing drawings in which:
FIG. 1 is a diametrical sectional view of one embodiment of the invention, FIG. lA is a partial diametrical sectional view of a variation of the embodiment of FIG. 1 with the corru-gated surface comprising a conical surface FIG. 2 is an exploded view of the dipole assembly FIG. 3 is a schematic representation of circuitry for actuating the drive motor with a remotely located shorting-type switch, FIG. 4 shows circuitry for actuating the drive motor in either direction, FIG 5 shows circuitry for actuating the drive motor to move between only two orthogonal positions, FIG. 6 shows feedback circuitry for selectively positioning the drive motor, FIG. 7A is a plan view of another embodiment of the invention, FIG. 7B is an end view of the dipole of FIG. 7A, FIG. 8 is a graphical representation illustrating the radiation intensity as a function of angle with the embodiment of FIGS. 7A and 7B, i13 FIG. 9A is a diametrical sectional view of a modification of the emhodiment of FIGS. 7A and 7B using a pair of crossed dipoles, and FIG. 9B i5 an end view of the dipoles of FIG. 9A.
With reference now to the drawing and more parti-cularly FIG. 1 thereof, there is shown a diametrical sectional view illustrating one embodiment of the invention. A front corrugated metal face 11 is connected to a short length of circular waveguide 12 before a section of rectangular wave-guide 13 aligned perpendicularly thereto. A small motor 14 is located concentrically to the circular waveguide 12 behind the assembly as shown. A dipole radiator 15 is one quarter waveguide wavelength before a metal wall 16 forming the end of the circular waveguide 12.
Referring to FIG. lA, there is shown a partial diametrical sectional view of a variation of the embodiment of FIG. 1 in which a front corrugated metal face 11' is substituted for corrugated metal face 11 and comprises a conical surface for improving the subtended illumination angle of the antenna feed.
Dipole 15 is of conventional construction, as shown in the exploded view of FIG. 2. Dipole 15 comprises a short cylinder 21 which is slotted at its outer end, an inner conductor 22 concentric to the short cylinder 21, and two flat metal arms 23 attached at right angles to cylinder 21. Inner conductor 22 extends through a short hole 24 in the metal wall connecting the circular 12 and rectangular 13 waveguides and then into rectangular waveguide 13 approxi-mately one eighth wavelength. A dielectric shaft 25 (for example, of Teflon* material), is fastened to the inner conductor 22 at this point and extends through the outer wall of the rectangular waveguide 13 and is connected to motor 14 through shaft coupling 26.
* Registered Trademark The position of the -top wall of rectangular waveguide 13 is chosen in accordance with well-known engineer-ing principles to be approximately one quarter waveguide length behind the axis of circular waveguide 12 for best impedance match. The dipole itself is tuned by adjusting its arm lengths to approximately 0.4 wavelength, and inner conductor 22 is fitted with a coaxial impedance transformer 27 so as to result in a good impedance match for the assembly.
In practice, a thin wall Teflon* sleeve 28 is placed between dipole cylinder 21 and hole 24 through the common wall so as to act as a mechanical bearing. The hole length itself is chosen to be approximately one quarter wavelength for best operation. Environmental sealing of this assembly is accomplished by the use of a high-temperature dielectric window 17 in the form of a polyimide film with an adhesive backing (for example, Dupont "Kapton'`* material which is placed between the corrugated face and -the rear metal housing. Such material provides for environmental sealing while preventing performance deterioration during solar "outage" conditions in satellite service in which the sun focuses thermal energy at the antenna feed.
Motor 14 may be any one of a large number of types of standard motors, depending on the interconnection require-ments to the attached equipment. A preferred motor is a small, 0.1 watt DC permanent magnet ge~rmotor capable of rotation speeds approximately 7 RPM at 12-15 volts DC and with a current drain of 2 milliamperes. Such a motor is easily capable of rotating dipole 15 because of the low inherent inertia and friction in the assembly. Actuation of motor 14 may be accomplished in a variety of ways, again depending on the interconnection requîrements. Alternatively, dipole 15 may be rotated and positioned manually.
FIG. 3 shows a circuit for causing motor 14 to rotate in one direction only through a remotely located shorting-type switch 31 which permits the earth station * Registered Trademark ~L~19~
user to adjust the polarization for the best recep-tion by starting and stopping motor 14, which may use the satellite receiver as a source of DC current. Shorting switch 31 short circuits the motor windings when the switch is "off`', thus abruptly stopping the motor shaft and preventing "coasting`'.
FIG. 4 shows a circuit allowing reversal of the rotation of the motor 14. A double-pole, three position shorting-type switch 41 is used with the same stopping advantages as described above and moves between a stable first disconnected position as shown to momentary contact with respective pairs of end terminals of switch 41.
FIG. 5 shows a circuit limiting antenna feed motor 14 to exactly 90 of rotation. This feature may be useful where the feed is utilized with reflectors placed on polar or equatorial-type mountings. In this case, the motor is arranged to rotate its shaft into fixed mechanical stops where it continues to draw current until energized into the opposite direction as shown. A voltage dropping resistor 51 has been found useful to guard against excessive motor heating in this instance.
FIG. 6 shows a drive circuit with motor 14 coupled to potentiometer 61 which forms one part of a simple feed-back loop. A fixed resistor 62 is switched in to command motor 14 to rotate exactly 90, Vernier potentiometer 63 is used for fine adjustments of the polarization angle. The latter is useful when changing the earth station antenna's position from one satellite to another, or for waking vernier adjustments on a given satellite.
FIG. 1 also shows some optional configurations of the preferred embodiment. An E-plane rectangular waveguide bend 18 may be incorporated so as to permit the LEA to extend along the axis of the feed. Also, a coaxial connector 19 may be placed on the broad wall of rectangular waveguide 13 and a shorting plate 110 fastened to the rectangular waveguide flange. With the connector situated one quarter wavelength from the shorting plate and with a probe 111 extending into the I.
7~13 rectangular waveguide from the coaxial connector inner conductor, an ef-ficient coupling is afforded to rec-tangular waveguide l This latter feature is useful when desiring to connect the antenna feed to coaxial-type 5 LNA's.
FIGS. 7A and 7B show another embodiment of the invention with -the circular waveguide cavity depth reduced and dipole 72 placed outside the face of the corrugations in the corruga-ted face. A hemispherical lQ dielectric weather cover 71 is placed over the dipole 72 in lieu of the Kapton window 17, Other features remain the same as previously discussed..
This embodiment is useful for illuminating very deep reflectors those having F/D ratios in the 0.25 to 15 0.35 range). The dipole arms are bent downward approx-imately 30~-45. This bending broadens out the radiation pattern of dipole 72, thus illuminating the reflector more efficiently -than the flat dipole 15. The presence of the corrugated face, however, sharply tapers the 20 radiation pattern ln a direction along the surface of the corrugations. This~tapering leads to a radiation pattern from the feed similar to that shown in FIG.. 8, FIG. 8 shows that the illumination of the angular aperture subtended by a deep reflector is 25 excellent while the sharp amplitude taper for larger angles greatly reduces electrical noise pickup from undesired sources. Such a radiation pattern can improve the ~ain/noise temperature ratio of an earth s-tation by as much as one dB.
FIGS. 9A and 9B show a modification of the embodiment of FIGS. 7A and 7B. The single dipole is re-placed by a pair ox dipoles 91 in a standard turnstile arrangement. For illuminating deep reflectors, the dipoles are bent downwàrds as for the single dipole case.
35 Dual LNA's are connected to these dipoles by means of short sections of coaxial line 92. A weather cover 93 is placed over the dipoles for environmental protection.
~7~13 This scheme provides the advantages of superior illu-mination efficiency wi-th -the simplicity of a dual polarized feed and without the high cost of an or-thomode transducer An example of one construction of the subject invention in a particular frequency band and -the electrical performance which has been measured is sum-marized as follows. The corrugated face is flat and is designed for optimum dimensions for -the 3.7-4.2 GHz 10 frequency band. It utilizes four grooves one inch deep and 0~75 inch apart. The circular waveguide 12 is 2.5 inches in diameter and the rectangular waveguide 13 has standard WR229 dimensions (1.145 inches by 2.290 inches internally). The dipole arms are 1.38 inches long, and 15 the dipole is spaced 0.63 inches in from the circular waveguide end. The probe internal to the rectangular waveguide is 0.50 inches long. Electrical charac-teristics for such a feed with -the circular opening flush to the plane of the corrugations are as follows:
Frequency Band 3.7-4.2 GHz Maximum VSWR 1,3 Polarization purity 30 dB, minimum insertion Loss Q.05 dB maximum Overall Feed Efficiency 77% for F/D = 0.4 reflector With the same dimensions as above, but with the dipole placed a distance of 0.63 inches in front of the corrugations, the same pérformance obtains except that the overall feed efficiency improves to 80% for reflect tors, having an F/D ratio of 0.3.
A dual dipole arrangement similar to the above provides iden-tical performance in both ports with an isolation of be-tter than 24 dB between ports.
The invention is embodied in the commercially available Model ESR~40 all~polarization prime focus feed 35 from Seavey Engineering Associates, Inc,, 339 Beechwood Street, Cohasse-t, VIA 02025.
There has been described novel apparatus and techniques for constructing a high gain antenna -feed offering a simple means for remotely ro-tating the polarization angle and, for use wi-th deep reflectors, offering improved efficiency through better illumination 5 of the reflector surface. It is eviden-t -that those skilled in the art may now make numerous uses and modifications of and departures from the specific embodiments described herein wi-thout departing from the inventive concepts. Consequently, the inventioh is to be 10 cons-trued as embracing each and every novel fea-ture and novel combination of features present in or possessed by the apparatus and techniques herein disclosed and limited solely by the spirit and scope of the appended claims, What is claimed is:
ANTENNA FEEDING WITH SELECTIVELY CONTROLLED POLARIZATION
The presen-t lnvention relates in general to an-tenna feeding with selective ,polarization and more particularly concerns novel apparatus and -techniques for 5 llluminating a deep paraboloid reflector with a cor-rugated face antenna -Eeed with selec-tively controlled polarization using mechanical elements of relatively low inertia easily driven by a small motor of such low power that it may be energized from the D.C. power supply of an 10 associated receiver.
Earth stations for reception of satellite sig-nals presently use the 3.7-4.2 GHz frequency band and require reflector antennas having diameters of 8 to 20 fee-t. To achieve nigh gain and low noise qualities from 15 these antennas, prior techniques have used (among others), simple corrugated face feeds exci-ted by the fun-damental mode of a circular waveguide. These types of feeds are well-known for producing good performance in these installations because they efficiently illuminate 20 reflectors having focal length-to-diameter (F/D) ratios of about 0.4 and larger, while reducing electrical noise pickup from the ear-th or frorn nearby in-terfering trans-mi-t-ters. zany present antenna reflectors use F/D ratios as srnall as 0.25, thus,creat;ing problems in attaining 25 efficient illumination and high gain.
However, these feeds must be rotate in their entirety together with any connected ~uxlliaryiequipmen-t, such as the low noise amplifier (~NA?, -to adjus-t the ..
j polarization angle. Presen-t clomes-tic sa-tellites use transponders having or-thogonal linear polariza-tion. The apparent polarization (that is, the polarixation angle as measured from the vertical at the earth Station) of the 5 satellite as seen from the earth sta-tion varies con-siderably depending on the location of the ear-th station and the position of the satelli-te's sta-tionary orbit.
Ro-tating the entire feed and LNA causes severe practical problems with cable wrap-ups and alignment ox the feed 10 with respect to -the focal poin-t of the reflec-tor. Both o-f these problems cause loss of signal and reliability degradation. Also, for those earth station installations which are configured to receive bo-th simultaneous orthogonal polarizatlons a relatively expensive device 15 known as an or-tho-mode transducer is required to be con-nected to the feed to separate the -two signals into two waveguide ports.
Accordingly, it is an impor-tant object of this $ invention to provide a device which permits remote rota-20 tion of the polarization angle of the an-tenna feed without the above disadvantages, and with only one moving part, while utilizing the proven qualities of the cor-rugated face.
A further object of this invention is to permit 25 efficient illumination of deep reflectors (in the range of 0.25-0.35 F/D ratios with -the simultaneous ability to remotely adjust the polarization angle, if desired.
I-t is a still further object of this invention to provide means for achieving the dual polariza-tion 30 capability with coaxial-type LNA's while also achieving the advantages of efficient illumination for deep re-flec-tors.
It is a further object of the invention to pro-vide the above objects wi-th a device which is compac-t, 35 simple in construction, lightweight, low cost, weather resistant, and which fixes the feed body and the LNA, thus obviating cable wraps and alignment problems.
Accoxding to the inven-tion, there is a corrugated face metal plate surrounded by a circular wavegulde opening excited by rotatable polarized antenna means polarized in a predetermined direction, such as a dipole or dipole pair.
In the case of the slngle dipole, remote means of polariza-tion adjustment àre afforded by extending the inner conduc-tor of the dipole into a rectangular waveguide placed behind the circular waveguide so as to excite it in its fundamental TEol propagation mode. There is means, such as a dielectric shaft connected between the inner conductor and the shaft of a small motor or other actuator, for selectively rotating the polarized radiating means. The depth of the circular waveguide cavity and the consequent axial position of the dipole is preferably adjusted for optimum illumination of a given F/D-ratio reflector. According to another feature of the invention, a pair of crossed dipoles with coaxial-LNA's provide dual polarized operation.
According to a further broad aspect of the present invention there is provided in an antenna feed having a corrugated surface concentric about the axis of an adjacent circular waveguide having an open end and a closed end formed with a central opening an improvement comprising polarized dipole antenna means polarized in a predetermined direction rotatably mounted about the axis and coupled to the circular waveguide and spaced from the circular waveguide closed end. Means is provided for rotatably supporting the antenna means for rotation about the axis. An output wave-guide means is provided for exchanging energy with the dipole antenna means through the central opening. Means is provided for coupling the dipole antenna means to the output waveguide means through the central opening comprising an insulating mechanical bearing sleeve seated in the central opening and a coaxial transmission line seated in the sleeve connected to the dipole antenna means and incIuding a coaxial impedance transformer for improving the impedance match between the dipole antenna means and the output waveguide means. Means is provided for rotating the assembly to, 7~13 3a and comprising the coaxial transmission line and the dipole antenna means to selectively control the polarization oE
the antenna feed about the axis. The axial length of the central opening is substantially a quarter wavelength and the dipole antenna means includes at least one pair of arms each substantially a quarter wavelength long extending radially outward from the axis. The distance between the arms and the closed end is substantially a quarter wave-length.
Numerous other features, objects and advantages of the invention will become apparent from the following specification when read in connection with the accompany-ing drawings in which:
FIG. 1 is a diametrical sectional view of one embodiment of the invention, FIG. lA is a partial diametrical sectional view of a variation of the embodiment of FIG. 1 with the corru-gated surface comprising a conical surface FIG. 2 is an exploded view of the dipole assembly FIG. 3 is a schematic representation of circuitry for actuating the drive motor with a remotely located shorting-type switch, FIG. 4 shows circuitry for actuating the drive motor in either direction, FIG 5 shows circuitry for actuating the drive motor to move between only two orthogonal positions, FIG. 6 shows feedback circuitry for selectively positioning the drive motor, FIG. 7A is a plan view of another embodiment of the invention, FIG. 7B is an end view of the dipole of FIG. 7A, FIG. 8 is a graphical representation illustrating the radiation intensity as a function of angle with the embodiment of FIGS. 7A and 7B, i13 FIG. 9A is a diametrical sectional view of a modification of the emhodiment of FIGS. 7A and 7B using a pair of crossed dipoles, and FIG. 9B i5 an end view of the dipoles of FIG. 9A.
With reference now to the drawing and more parti-cularly FIG. 1 thereof, there is shown a diametrical sectional view illustrating one embodiment of the invention. A front corrugated metal face 11 is connected to a short length of circular waveguide 12 before a section of rectangular wave-guide 13 aligned perpendicularly thereto. A small motor 14 is located concentrically to the circular waveguide 12 behind the assembly as shown. A dipole radiator 15 is one quarter waveguide wavelength before a metal wall 16 forming the end of the circular waveguide 12.
Referring to FIG. lA, there is shown a partial diametrical sectional view of a variation of the embodiment of FIG. 1 in which a front corrugated metal face 11' is substituted for corrugated metal face 11 and comprises a conical surface for improving the subtended illumination angle of the antenna feed.
Dipole 15 is of conventional construction, as shown in the exploded view of FIG. 2. Dipole 15 comprises a short cylinder 21 which is slotted at its outer end, an inner conductor 22 concentric to the short cylinder 21, and two flat metal arms 23 attached at right angles to cylinder 21. Inner conductor 22 extends through a short hole 24 in the metal wall connecting the circular 12 and rectangular 13 waveguides and then into rectangular waveguide 13 approxi-mately one eighth wavelength. A dielectric shaft 25 (for example, of Teflon* material), is fastened to the inner conductor 22 at this point and extends through the outer wall of the rectangular waveguide 13 and is connected to motor 14 through shaft coupling 26.
* Registered Trademark The position of the -top wall of rectangular waveguide 13 is chosen in accordance with well-known engineer-ing principles to be approximately one quarter waveguide length behind the axis of circular waveguide 12 for best impedance match. The dipole itself is tuned by adjusting its arm lengths to approximately 0.4 wavelength, and inner conductor 22 is fitted with a coaxial impedance transformer 27 so as to result in a good impedance match for the assembly.
In practice, a thin wall Teflon* sleeve 28 is placed between dipole cylinder 21 and hole 24 through the common wall so as to act as a mechanical bearing. The hole length itself is chosen to be approximately one quarter wavelength for best operation. Environmental sealing of this assembly is accomplished by the use of a high-temperature dielectric window 17 in the form of a polyimide film with an adhesive backing (for example, Dupont "Kapton'`* material which is placed between the corrugated face and -the rear metal housing. Such material provides for environmental sealing while preventing performance deterioration during solar "outage" conditions in satellite service in which the sun focuses thermal energy at the antenna feed.
Motor 14 may be any one of a large number of types of standard motors, depending on the interconnection require-ments to the attached equipment. A preferred motor is a small, 0.1 watt DC permanent magnet ge~rmotor capable of rotation speeds approximately 7 RPM at 12-15 volts DC and with a current drain of 2 milliamperes. Such a motor is easily capable of rotating dipole 15 because of the low inherent inertia and friction in the assembly. Actuation of motor 14 may be accomplished in a variety of ways, again depending on the interconnection requîrements. Alternatively, dipole 15 may be rotated and positioned manually.
FIG. 3 shows a circuit for causing motor 14 to rotate in one direction only through a remotely located shorting-type switch 31 which permits the earth station * Registered Trademark ~L~19~
user to adjust the polarization for the best recep-tion by starting and stopping motor 14, which may use the satellite receiver as a source of DC current. Shorting switch 31 short circuits the motor windings when the switch is "off`', thus abruptly stopping the motor shaft and preventing "coasting`'.
FIG. 4 shows a circuit allowing reversal of the rotation of the motor 14. A double-pole, three position shorting-type switch 41 is used with the same stopping advantages as described above and moves between a stable first disconnected position as shown to momentary contact with respective pairs of end terminals of switch 41.
FIG. 5 shows a circuit limiting antenna feed motor 14 to exactly 90 of rotation. This feature may be useful where the feed is utilized with reflectors placed on polar or equatorial-type mountings. In this case, the motor is arranged to rotate its shaft into fixed mechanical stops where it continues to draw current until energized into the opposite direction as shown. A voltage dropping resistor 51 has been found useful to guard against excessive motor heating in this instance.
FIG. 6 shows a drive circuit with motor 14 coupled to potentiometer 61 which forms one part of a simple feed-back loop. A fixed resistor 62 is switched in to command motor 14 to rotate exactly 90, Vernier potentiometer 63 is used for fine adjustments of the polarization angle. The latter is useful when changing the earth station antenna's position from one satellite to another, or for waking vernier adjustments on a given satellite.
FIG. 1 also shows some optional configurations of the preferred embodiment. An E-plane rectangular waveguide bend 18 may be incorporated so as to permit the LEA to extend along the axis of the feed. Also, a coaxial connector 19 may be placed on the broad wall of rectangular waveguide 13 and a shorting plate 110 fastened to the rectangular waveguide flange. With the connector situated one quarter wavelength from the shorting plate and with a probe 111 extending into the I.
7~13 rectangular waveguide from the coaxial connector inner conductor, an ef-ficient coupling is afforded to rec-tangular waveguide l This latter feature is useful when desiring to connect the antenna feed to coaxial-type 5 LNA's.
FIGS. 7A and 7B show another embodiment of the invention with -the circular waveguide cavity depth reduced and dipole 72 placed outside the face of the corrugations in the corruga-ted face. A hemispherical lQ dielectric weather cover 71 is placed over the dipole 72 in lieu of the Kapton window 17, Other features remain the same as previously discussed..
This embodiment is useful for illuminating very deep reflectors those having F/D ratios in the 0.25 to 15 0.35 range). The dipole arms are bent downward approx-imately 30~-45. This bending broadens out the radiation pattern of dipole 72, thus illuminating the reflector more efficiently -than the flat dipole 15. The presence of the corrugated face, however, sharply tapers the 20 radiation pattern ln a direction along the surface of the corrugations. This~tapering leads to a radiation pattern from the feed similar to that shown in FIG.. 8, FIG. 8 shows that the illumination of the angular aperture subtended by a deep reflector is 25 excellent while the sharp amplitude taper for larger angles greatly reduces electrical noise pickup from undesired sources. Such a radiation pattern can improve the ~ain/noise temperature ratio of an earth s-tation by as much as one dB.
FIGS. 9A and 9B show a modification of the embodiment of FIGS. 7A and 7B. The single dipole is re-placed by a pair ox dipoles 91 in a standard turnstile arrangement. For illuminating deep reflectors, the dipoles are bent downwàrds as for the single dipole case.
35 Dual LNA's are connected to these dipoles by means of short sections of coaxial line 92. A weather cover 93 is placed over the dipoles for environmental protection.
~7~13 This scheme provides the advantages of superior illu-mination efficiency wi-th -the simplicity of a dual polarized feed and without the high cost of an or-thomode transducer An example of one construction of the subject invention in a particular frequency band and -the electrical performance which has been measured is sum-marized as follows. The corrugated face is flat and is designed for optimum dimensions for -the 3.7-4.2 GHz 10 frequency band. It utilizes four grooves one inch deep and 0~75 inch apart. The circular waveguide 12 is 2.5 inches in diameter and the rectangular waveguide 13 has standard WR229 dimensions (1.145 inches by 2.290 inches internally). The dipole arms are 1.38 inches long, and 15 the dipole is spaced 0.63 inches in from the circular waveguide end. The probe internal to the rectangular waveguide is 0.50 inches long. Electrical charac-teristics for such a feed with -the circular opening flush to the plane of the corrugations are as follows:
Frequency Band 3.7-4.2 GHz Maximum VSWR 1,3 Polarization purity 30 dB, minimum insertion Loss Q.05 dB maximum Overall Feed Efficiency 77% for F/D = 0.4 reflector With the same dimensions as above, but with the dipole placed a distance of 0.63 inches in front of the corrugations, the same pérformance obtains except that the overall feed efficiency improves to 80% for reflect tors, having an F/D ratio of 0.3.
A dual dipole arrangement similar to the above provides iden-tical performance in both ports with an isolation of be-tter than 24 dB between ports.
The invention is embodied in the commercially available Model ESR~40 all~polarization prime focus feed 35 from Seavey Engineering Associates, Inc,, 339 Beechwood Street, Cohasse-t, VIA 02025.
There has been described novel apparatus and techniques for constructing a high gain antenna -feed offering a simple means for remotely ro-tating the polarization angle and, for use wi-th deep reflectors, offering improved efficiency through better illumination 5 of the reflector surface. It is eviden-t -that those skilled in the art may now make numerous uses and modifications of and departures from the specific embodiments described herein wi-thout departing from the inventive concepts. Consequently, the inventioh is to be 10 cons-trued as embracing each and every novel fea-ture and novel combination of features present in or possessed by the apparatus and techniques herein disclosed and limited solely by the spirit and scope of the appended claims, What is claimed is:
Claims (13)
1. In an antenna feed having a corrugated surface concentric about the axis of an adjacent circular waveguide having an open end and a closed end formed with a central opening the improvement comprising, polarized dipole antenna means polarized in a predetermined direction rotatably mounted about said axis and coupled to said circular waveguide and spaced from the circular waveguide closed end, means for rotatably supporting said antenna means for rotation about said axis, an output waveguide means for exchanging energy with said dipole antenna means through said central opening, means for coupling said dipole antenna means to said output waveguide means through said central opening comprising an insulating mechanical bearing sleeve seated in said central opening and a coaxial transmission line seated in said sleeve connected to said dipole antenna means and including a coaxial impedance transformer for improving the impedance match between said dipole antenna means and said output waveguide means, and means for rotating the assembly comprising said coaxial transmission line and said dipole antenna means to selectively control the polarization of said antenna feed about said axis, wherein the axial length of said central opening is substantially a quarter wavelength, said dipole antenna means includes at least one pair of arms each substantially a quarter wavelength long extending radially outward from said axis, and the distance between said arms and said closed end is substantially a quarter wavelength.
2. The improvement in accordance with claim 1 wherein said output waveguide means is a rectangular waveguide adjacent to said circular waveguide closed end, and said coaxial transmission line has an inner conductor extending through said central opening into said rectangular waveguide comprising a probe.
3. The improvement in accordance with claim 2 and further comprising a dielectric shaft connected to said probe and passing through a wall of said rectangular waveguide opposite said central opening, and motor means connected to said dielectric shaft for selectively rotating said assembly.
4. The improvement in accordance with claim 3 and further comprising control means for establishing fixed stop positions of said motor means in space quadrature for selec-tively positioning said dipole antenna means in a selected one of two polarizations in space quadrature.
5. The improvement in accordance with claim 3 and further comprising position transducing means for providing a signal representative of the angular orientation of said dipole antenna means, and closed loop servo circuit means responsive to a command signal and said position signal for energizing said motor means until said command signal and said position signal substantially coincide.
6. The improvement in accordance with claim 5 wherein said source of a position signal comprises a potentiometer mechanically coupled to said dielectric shaft, and further comprising selectively variable resistance means for providing said command signals.
7. The improvement in accordance with claim 3 wherein said dipole antenna means is outside said circular waveguide.
8. The improvement in accordance with claim 1 wherein said output waveguide means comprises a fixed coaxial connector.
9. The improvement in accordance with claim 3 wherein said dipole antenna means is formed with arms forming an acute angle with said axis to broaden the beam width of said antenna field while establishing a sharp taper to the radiation pattern along the direction of said corrugated surface.
10. The improvement in accordance with claim 9 wherein said corrugated surface comprises a conical surface for improving the subtended illumination angle of said antenna feed.
11. The improvement in accordance with claim 3 wherein said dipole antenna means comprises first and second dipoles having first and second pairs of arms respectively in space quadrature about said axis coacting to form a turnstile, a second output waveguide means, and means for coupling said first and second dipoles to said first and second output waveguide means respectively.
12. The improvement in accordance with claim 11 wherein said first and second output waveguide means comprise first and second coaxial connectors respectively.
13. The improvement in accordance with claim 1 wherein said coaxial transmission line includes an inner conductor extending through said central opening into said output waveguide means for a distance corresponding substantially to an eighth wavelength.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/383,822 US4504836A (en) | 1982-06-01 | 1982-06-01 | Antenna feeding with selectively controlled polarization |
| US383,822 | 1982-06-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1197613A true CA1197613A (en) | 1985-12-03 |
Family
ID=23514858
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000429307A Expired CA1197613A (en) | 1982-06-01 | 1983-05-31 | Antenna feeding with selectively controlled polarization |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4504836A (en) |
| CA (1) | CA1197613A (en) |
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| US4622559A (en) * | 1984-04-12 | 1986-11-11 | Canadian Patents & Development Limited | Paraboloid reflector antenna feed having a flange with tapered corrugations |
| US4554553A (en) * | 1984-06-15 | 1985-11-19 | Fay Grim | Polarized signal receiver probe |
| US4672388A (en) * | 1984-06-15 | 1987-06-09 | Fay Grim | Polarized signal receiver waveguides and probe |
| US4755828A (en) * | 1984-06-15 | 1988-07-05 | Fay Grim | Polarized signal receiver waveguides and probe |
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| US4829313A (en) * | 1984-11-15 | 1989-05-09 | Chaparral Communications | Drive system and filament for a twistable septum in a feedhorn |
| JPS6297401A (en) * | 1985-10-24 | 1987-05-06 | Shimada Phys & Chem Ind Co Ltd | Waveguide type linearly polarized wave changeover equipment |
| US4785302A (en) * | 1985-10-30 | 1988-11-15 | Capetronic (Bsr) Ltd. | Automatic polarization control system for TVRO receivers |
| US4740795A (en) * | 1986-05-28 | 1988-04-26 | Seavey Engineering Associates, Inc. | Dual frequency antenna feeding with coincident phase centers |
| US4841261A (en) * | 1987-09-01 | 1989-06-20 | Augustin Eugene P | Microwave rotary junction with external rotary energy coupling |
| US5255003B1 (en) * | 1987-10-02 | 1995-05-16 | Antenna Downlink Inc | Multiple-frequency microwave feed assembly |
| US4903037A (en) * | 1987-10-02 | 1990-02-20 | Antenna Downlink, Inc. | Dual frequency microwave feed assembly |
| US5103237A (en) * | 1988-10-05 | 1992-04-07 | Chaparral Communications | Dual band signal receiver |
| US4862187A (en) * | 1988-10-24 | 1989-08-29 | Microwave Components And Systems, Inc. | Dual band feedhorn with two different dipole sets |
| US5066958A (en) * | 1989-08-02 | 1991-11-19 | Antenna Down Link, Inc. | Dual frequency coaxial feed assembly |
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| GB2261771B (en) * | 1991-11-20 | 1995-08-30 | Northern Telecom Ltd | Flat plate antenna |
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| CA2551621C (en) * | 2003-12-31 | 2013-04-23 | Brunello Locatori | Method and device for tv receiving and internet transreceiving on a satellite antenna |
| GB0422179D0 (en) * | 2004-10-06 | 2004-11-03 | Sarantel Ltd | Antenna feed structure |
| CN1815811B (en) * | 2005-01-31 | 2012-05-09 | 东南大学 | Composite microband printing vibrator wide-band antenna |
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| JP2009267672A (en) * | 2008-04-24 | 2009-11-12 | Nec Corp | Primary radiator for antenna, and the antenna |
| CN102136632A (en) * | 2011-01-26 | 2011-07-27 | 浙江大学 | Circularly-polarized highly-directive periodic groove plate antenna |
| US10024954B1 (en) * | 2012-11-05 | 2018-07-17 | The United States Of America As Represented By The Secretary Of The Navy | Integrated axial choke rotary offset parabolic reflector |
| WO2016147242A1 (en) * | 2015-03-17 | 2016-09-22 | 日本電気株式会社 | Antenna device, communication device and communication system |
| JP6835358B2 (en) * | 2017-11-24 | 2021-02-24 | 森田テック 株式会社 | Antenna device, antenna system, and measurement system |
| TWI736854B (en) * | 2019-03-05 | 2021-08-21 | 啓碁科技股份有限公司 | Communication device and antenna structure |
| US11050151B2 (en) * | 2019-06-04 | 2021-06-29 | City University Of Hong Kong | Multi-band antenna |
| US11063357B2 (en) * | 2019-06-04 | 2021-07-13 | City University Of Hong Kong | Dual-band antenna for global positioning system |
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| US2680810A (en) * | 1952-02-12 | 1954-06-08 | Us Army | Microwave antenna system |
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| US3215957A (en) * | 1962-03-05 | 1965-11-02 | Bendix Corp | Variable polarization for microwaves |
| US4021814A (en) * | 1976-01-19 | 1977-05-03 | The United States Of America As Represented By The Secretary Of The Army | Broadband corrugated horn with double-ridged circular waveguide |
| US4168504A (en) * | 1978-01-27 | 1979-09-18 | E-Systems, Inc. | Multimode dual frequency antenna feed horn |
| US4375052A (en) * | 1980-07-11 | 1983-02-22 | Microdyne Corporation | Polarization rotatable antenna feed |
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-
1982
- 1982-06-01 US US06/383,822 patent/US4504836A/en not_active Expired - Fee Related
-
1983
- 1983-05-31 CA CA000429307A patent/CA1197613A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4504836A (en) | 1985-03-12 |
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