EP0237988A1 - Polarisator für Antennen, die Satellitensignale empfangen - Google Patents

Polarisator für Antennen, die Satellitensignale empfangen Download PDF

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Publication number
EP0237988A1
EP0237988A1 EP87103697A EP87103697A EP0237988A1 EP 0237988 A1 EP0237988 A1 EP 0237988A1 EP 87103697 A EP87103697 A EP 87103697A EP 87103697 A EP87103697 A EP 87103697A EP 0237988 A1 EP0237988 A1 EP 0237988A1
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EP
European Patent Office
Prior art keywords
waveguide
ferrite
rotator
rotator according
inductor
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.)
Withdrawn
Application number
EP87103697A
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English (en)
French (fr)
Inventor
Giuseppe Sacchi
Ettore Cozzi
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.)
IRTE SpA
Original Assignee
IRTE SpA
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Filing date
Publication date
Application filed by IRTE SpA filed Critical IRTE SpA
Publication of EP0237988A1 publication Critical patent/EP0237988A1/de
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/165—Auxiliary devices for rotating the plane of polarisation
    • H01P1/175—Auxiliary devices for rotating the plane of polarisation using Faraday rotators

Definitions

  • This invention generally relates to antennas for receiving transmissions from satellite in linear polarization and, more particularly, to a rotator permitting the antennas to receive both X-polarized and Y-polarized signals.
  • the transmission of signals from satellite is usually made in linear or circular polarization.
  • the electric field vector (assuming the Z-axis as propagation direction in the X,Y,Z Cartesian axes) rotates about the Z-axis by maintaining its absolute value constant.
  • the electric field vector maintains itself,during the propagation, parallel to the X-axis or Y-axis.
  • the satellites operating in linear polarization will transmit to earth both X-polarized signals and Y-polarized signals.
  • the satellite is equipped with 12 transponders for earth transmissions (however, only a maximum of 9 transponders can simultaneously transmit) one half of which operates in X-polarization, whereas the other half is preset for the transmission of Y-polarized signals.
  • the illuminator orientation will determine in univocal manner the possibility of receiving-either of the X-polarized and Y-polarized signals.
  • the illuminator will have to be rotated by 90° (suppose that it is preferred to rotate all the paraboloid).
  • a simpler system consists in inserting within the illuminator a pair of movable plates of a dielectric material, which have a predetermined length and are inclined in a suitable manner with respect to the incident field.
  • the change of polarization will require in-this case the simple rotation by 90° of one of the pair of plates.
  • This is a relatively simple and effective approach which requires, however, for the remote control, the use of electro-mechanical components and therefore the presence of movable mechanical elements.
  • the present invention aims at obviating the disadvantages concerning the known antennas for receiving tmsmissions from satellite, by providing a static device to be applied to receiving parabolic antennas of known construction and of any type in order to permit them to receive both X-polarized signals and Y-polarized signals and which can be operatively mounted also by unskilled labour.
  • the rotator for antennas receiving transmissions from satellite is characterized in that it comprises a waveguide segment of circular cross-section, containing along its longitudinal axis a cylindrical rod of ferrite, supporting means for this ferrite rod and an inductor arranged outside the waveguide segment and intended, when excited, to cause the rotation of polarization of the incoming signals, this waveguide segment being provided with means for fastening it to the illuminator of the receiving antenna.
  • the rotator according to the present invention relies upon the Faraday's effect on its operation, this effect being here concisely explained.
  • the Faraday's effect is well known as responsible of the field rotations found in the propagation of the linearly polarized electromagnetic waves in the high layers of the atmosphere (ionosphere).
  • the Faraday's rotation occurs when a linearly polarized plane wave TEM propagates in an anisotropic dielectric medium.
  • a conventional example of magnetic anisotropy is offered by the ferritic materials immersed in continuous magnetic fields.
  • the magnetic permeability will assume a tensorial form and the component, for example along the X-axis of the induction vector, will be determined not only by the component relating to the same axis of the field vector but also by the components of this vector along the Y-and X-axes.
  • a linearly polarized vector can be always interpreted as the addition of two vectors which are circularly polarized in opposite directions, and each of which has an amplitude which is one half of the original vector amplitude.
  • Kz is the propagation constant in the me dium.
  • the values of Kz for two opposite circular polarizations will be different because, as already said, the values of the magnetic permeability are different.
  • the equation 3) will be therefore rewritten as follows: where:
  • This rotation can be expressed as follows: where 0 is measured in radians and Z in meters. Note that
  • S is the cross-section of the waveguide in m 2.
  • the rotator according to the invention is formed of a waveguide segment, generally indicated at 10, having a circular cross-section and at its ends a flange 11 and 12, respectively, each of these flanges being provided with four holes 13 for securing the rotator to the usual illuminator of a parabolic antenna for receiving signals coming from satellite.
  • a ferrite rod 14 Arranged along the longitudinal axis of the waveguide segment 10 is a ferrite rod 14 having a circular cross-section and critical dimensions which will be given in the description of the various components and which, at its ends, terminates in two points 15 and 16.
  • the ferrite rod is held in position within the waveguide segment 10 by two discs 17 and 18 of a material exhibiting good mechanical and electrical characteristics, as well as a good dimensional stability, the discs being provided centrally with a hole 19 having substantially the same diameter as the ferrite rod 14.
  • the ferrite rod 14 is fastened by means of an adhesive on the two discs which are then secured within the waveguide segment in the desired positions.
  • the supporting discs 17 and 18 have holes 20 which are spaced apart the same distance along a circumference and which have been provided for the purpose of minimizing the interferences between the dielectric material and the incident electromagnetic field.
  • an inductor 21 Arranged outside the waveguide segment is an inductor 21 connected to a power supply and which is intended, when excited, to rotate the polarization of the signal entering the waveguide segment.
  • the dimensions of the ferrite rod 10 have been selected so as to obtain field rotations wider than ⁇ 90° so as to be sure to have a good reception also in the case that the antenna parabola has been rotated in the polar plane to track a satellite, with relative rotation of the illuminator.
  • the purpose of the inductor 21 is to generate a constant magnetic field within the waveguide segment 10, directed along the axis thereof.
  • the material used is aluminium anticorodal paralluman 7.
  • the inside diameter of the waveguide is 17,5 mm.
  • the order mode TE has therefore a cut-off frequency of about 10 GHz, while the first upper mode TH 01 has a cut-off frequency of 13,2 GHz.
  • the selected working band ranges from 10,9 to 11,7 GHz. In the case of the ECS this band includes the working frequencies of the first 10 transponders. None prevents, however, without making particular changes to the design, of widening the band up to 12,6 GHz so as to include also the remaining two transponders (12,50-12,58 GHz).
  • the length of the waveguide segment is 80 mm exclusive of the flange thickness but, since this is not a critical parameter, it cannot be excluded that in the manufacturing stage, different dimensions can be adopted.
  • the inductor is formed of a coil of about 55 mm in length and which is arranged around the waveguide body so as to generate a magnetic field Ho directed along the waveguide axis.
  • the magnetic field values have been experimentally evaluated: it has been noted that with a field Ho of about 6000 Ampere.tums/m it is possible to obtain rotations wider than 90° over the entire band with the used ferrite rod.
  • the indicated field value has been obtained by winding 3500 turns over 55 mm and employing excitation currents of a maximum of 1100 mA.
  • the physical dimensions of the inductor are relatively reduced and the thickness is such as to be below the flange limits.
  • the used material is an yttrium-gadolinium-aluminium gamet having a saturation magnetization of about 150 kA/m, a Curie temperature of 205°C, a ⁇ f of 15,5 (relative dielectric constant). Other significant parameters are the loss tangent ⁇ 2 x 10 -4 and the line length A H of 0,8 kA/m.
  • the nowaday used ferrite rod is 42 mm in length and 4,5 mm in diameter.
  • the measures have been carried out in laboratory at a temperature of 20°C.
  • the measured ROS value over all the band (see Fig.4) is always lower than 1,3 (reflection coefficient better than -18 dB).
  • the insertion losses of the waveguide with ferrite rod with respect to the same waveguide without ferrite rod and without excitation are in the order of 0,25 dB.
  • the field polarization rotation of 90° is obtained with current values ranging from 40 mA for the higher frequencies to 80-90 mA for the lower frequencies (see Fig.6).
  • the maximum rotation which can be obtained with the nowaday dimensions of the ferrite rod are in the order of 1100°.
  • the rotator according to the present invention allows both X-polarized signals and Y-polarized signals to be received from a satellite, which signals are at present usually transmitted in linear polarization.
  • This rotator when experimentally mounted on an antenna having a parabola of 1,5 m of diameter aimed at the satellite ECS, has proved to operate in a very effective manner.
  • This device is also simple in construction, does not contain moving mechanical elements, requires low supply powers and can readily applied without the intervention of skilled labour to the usual parabolic antennas for receiving from satellite linearly polarized signals.
EP87103697A 1986-03-18 1987-03-13 Polarisator für Antennen, die Satellitensignale empfangen Withdrawn EP0237988A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT1978586 1986-03-18
IT8619785A IT1188455B (it) 1986-03-18 1986-03-18 Rotatore di polarizzazione per antenne riceventi di trasmissioni da satellite

Publications (1)

Publication Number Publication Date
EP0237988A1 true EP0237988A1 (de) 1987-09-23

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP87103697A Withdrawn EP0237988A1 (de) 1986-03-18 1987-03-13 Polarisator für Antennen, die Satellitensignale empfangen

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EP (1) EP0237988A1 (de)
IT (1) IT1188455B (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0351840A2 (de) * 1988-07-21 1990-01-24 CSELT Centro Studi e Laboratori Telecomunicazioni S.p.A. Mit Dielektrikum belasteter Hohlraumresonator
WO1990006002A1 (en) * 1988-11-14 1990-05-31 Motson & Company Limited Microwave signal receiving apparatus
WO1990010958A1 (en) * 1989-03-15 1990-09-20 Cambridge Computer Limited Improvements in antenna polarizers
GB2254491A (en) * 1991-04-05 1992-10-07 Marconi Electronic Devices Polarisers.

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3023165A (en) * 1956-08-17 1962-02-27 Bell Telephone Labor Inc Magnesium ferrite containing aluminum and method of making same
DE1591362A1 (de) * 1967-04-21 1970-12-23 Philips Patentverwaltung Koaxialleitungsstuetze fuer starre und flexible Hochfrequenzleitungen
US3938158A (en) * 1973-12-19 1976-02-10 Raytheon Company Antenna element for circular or linear polarization

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3023165A (en) * 1956-08-17 1962-02-27 Bell Telephone Labor Inc Magnesium ferrite containing aluminum and method of making same
DE1591362A1 (de) * 1967-04-21 1970-12-23 Philips Patentverwaltung Koaxialleitungsstuetze fuer starre und flexible Hochfrequenzleitungen
US3938158A (en) * 1973-12-19 1976-02-10 Raytheon Company Antenna element for circular or linear polarization

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, vol. 3, no. 153 (E-159), 15th December 1979, page 56 E 159; & JP - A - 54 133 049 (MITSUBISHI DENKI) 16-10-1979 *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0351840A2 (de) * 1988-07-21 1990-01-24 CSELT Centro Studi e Laboratori Telecomunicazioni S.p.A. Mit Dielektrikum belasteter Hohlraumresonator
EP0351840A3 (en) * 1988-07-21 1990-12-05 Cselt Centro Studi E Laboratori Telecomunicazioni S.P.A. Dielectric-loaded cavity resonator
WO1990006002A1 (en) * 1988-11-14 1990-05-31 Motson & Company Limited Microwave signal receiving apparatus
WO1990010958A1 (en) * 1989-03-15 1990-09-20 Cambridge Computer Limited Improvements in antenna polarizers
GB2254491A (en) * 1991-04-05 1992-10-07 Marconi Electronic Devices Polarisers.
US5229737A (en) * 1991-04-05 1993-07-20 Marconi Electronic Devices Limited Ferrite polarizer
GB2254491B (en) * 1991-04-05 1995-03-22 Marconi Electronic Devices Polarisers

Also Published As

Publication number Publication date
IT8619785A1 (it) 1987-09-18
IT1188455B (it) 1988-01-14
IT8619785A0 (it) 1986-03-18

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