EP0319753B1 - Exciting or feeding system for a parabolic antenna - Google Patents

Abstract

In order to be able to receive and transmit differently polarised electromagnetic waves with only one supply system, two polarisers are arranged in a waveguide emitter, both of which must be capable of being brought into any required angular positions with respect to one another. This demands high structural complexity and relatively extensive adjusting measures. In order to produce an excitation and supply system which is of much simpler construction and which can be adjusted very much more easily, a 90 DEG phase-shifting component (15) is arranged in a waveguide (5) in the receive direction and a 180 DEG phase-shifting component (17) is arranged downstream from it. The 90 DEG phase-shifting component (15) is installed in a fixed manner such that it cannot rotate vertically or horizontally. Only the 180 DEG phase-shifting component (17) has to be rotated into a specific angular position to receive one of the four differently polarised waves. The excitation and supply system is primarily suitable for the reception of television broadcasting satellites. <IMAGE>

Description

The invention relates to an excitation or feed system, in particular for a parabolic antenna for receiving or transmitting linear and / or circularly polarized electromagnetic waves according to the preamble of claim 1.

The use of orthogonally polarized electromagnetic waves has been known for years, which makes it possible to use double frequencies.

The installation of such receiving antennas also requires exact alignment of the antenna in terms of its polarization to ensure the separation between the different channels. Since the television broadcasting satellites are adjusted geostationarily in space, the orientation with regard to the linear polarization can be preselected once, which doesn't change then. If the antenna is to be swiveled to another satellite, this can be done with a so-called polar mount. It is an antenna structure in which the polar circle is traversed when the antenna is adjusted and aligned with another geostationary satellite, so that the orthogonal polarizations are automatically maintained.

The current generation of broadcasting satellites also send and receive circular polarizations. Double frequency utilization is also possible here, since opposite circular polarizations are possible.

Antennas for double polarization operation would, however, have to have a particularly good polarization separation so that a sufficient decoupling between the channels of the same frequency is possible.

To receive two linear polarizations aligned orthogonally to one another and two circular polarizations rotating in opposite directions, two excitation or supply systems with four adjoining converters must therefore be provided. The two linearly polarized and the oppositely circularly polarized electromagnetic waves are received via a respective feed system, and the one converter mentioned is required for each polarization.

In order to reduce the technical construction costs for this, an excitation or feed system has already become known in which two so-called polarizers have been arranged one behind the other in the axial direction in a waveguide, with each polarizer for the relevant frequency range as a so-called 90 ° phase shifter for the E-vector of the electromagnetic wave is effective.

In order to transmit or receive differently polarized electromagnetic waves with such an excitation or feed system, both 90 ° polarizations must be freely adjustable. For this purpose, both polarizers are each seated on an adjusting axis which is concentric to one another and which can accordingly be actuated, as a rule by means of an electric motor, and brought into a desired angular position with respect to the vertical or horizontal or with respect to one another.

The advantage of only needing a single excitation or feed system for the reception of orthogonally linear and oppositely circular waves is, however, bought with the disadvantage that both 90 ° phase shift plates have to be adjustable at any angle to one another, which separates two continuous ones Controllable axes with a hollow axis and two separately controllable electric motors for adjusting the plates required.

The construction and cost of such an excitation or feed system is therefore not negligible.

The object of the present invention is, based on the last-described prior art, an exciter or. To create a feed system for receiving differently polarized electromagnetic waves, which is designed much simpler and much easier to adjust so that the differently polarized waves can be fed or excited.

An excitation system according to the preamble of claim 1 is known from US-A-4,264,908.

The object is achieved according to the features specified in the characterizing part of claim 1. Advantageous embodiments of the invention are specified in the subclaims.

By means of the present invention, an excitation or feed system is created in a simple manner, in which two linear, mutually perpendicular, as well as two oppositely circular polarizations can be received, using only a microwave converter. According to the invention, a single lamina must now be oriented differently in its setting position with respect to the vertical or horizontal in order to be able to feed in or transmit the different polarizations. According to the invention, this is achieved by using a subordinate 180 ° phase shift plate lying in the receiving direction. The first 90 ° phase plate is firmly and rigidly installed and aligned. An orientation in the vertical but also in the horizontal direction of the linearly polarized wave can be selected. Operation of the excitation or feed system according to the invention is possible in both basic orientations.

Due to the alignment perpendicular or parallel to the incident e-vector, the 90 ° plate does not cause a spatial rotation, but only a phase shift of the linearly polarized wave. A circularly polarized wave hitting the 90 ° plate is converted into a linearly polarized wave, the vector of which, depending on the direction of rotation of the circularly polarized wave, is rotated by ± 45 ° against the orientation of the plate. The following 180 ° plate now serves to spatially rotate the e-vector appearing at the output of the 90 ° plate, depending on the orientation (0 °, 90 °, + 45 °, -45 °), so that the Vector always has a constant direction, to which the converter coupling is then set.

According to the invention, therefore, only a 180 ° phase shift plate or block has to be adjusted, which is why only one only electric drive is needed for this. In addition, the entire adjustment range can be limited to 67.5 °, since no further adjustment swiveling movements are necessary.

Of course, 180 ° phase shifters are known in principle from the prior art. However, the use of two components which cause a different phase shift to achieve such a simple and inexpensive excitation or feed system has so far not become known and was also not obvious.

Instead of the phase-shifting dielectric plates mentioned, other construction measures, for example in the manner of a waveguide constriction, can of course also be used to carry out the desired phase shift.

Fig. 1 :

eine schematische Längsschnittdarstellung durch ein erfindungsgemäßes Erreger- bzw. Speisesystem;

Fig. 2a bis 2d:

unterschiedliche Beispiele für linear- und zirkularpolarisierte Wellen, die bei entsprechender Ausrichtung des 180°-Plättchens zu dem 90°-Plättchen jeweils einen gleichgerichteten E-Vektor erzeugen;

Fig. 3a bis 3d :

unterschiedliche Beispiele für linear- und polarisierte Wellen, die bei entsprechender Ausrichtung des 180°-Plättchens zu dem 90°-Plättchen jeweils einen gleichgerichteten E-Vektor erzeugen, der senkrecht zu dem in Fig. 2a bis 2d erzeugten E-Vektor liegt;

Fig. 4a bis 5d :

unterschiedliche Darstellungen zur Erläuterung der Funktionsweise eines 180°-Plättchens bei linear bzw. zirkular polarisierten Wellen.

Further advantages, details and features of the invention result below from the exemplary embodiments illustrated with reference to drawings. The following show in detail:

Fig. 1:

a schematic longitudinal sectional view through an excitation or feed system according to the invention;

2a to 2d:

different examples of linearly and circularly polarized waves which each generate a rectified E-vector when the 180 ° plate is aligned with the 90 ° plate;

3a to 3d:

different examples of linear and polarized waves, which with appropriate orientation of the 180 ° plate generate a rectified E-vector for the 90 ° plate, which is perpendicular to the E-vector generated in FIGS. 2a to 2d;

4a to 5d:

different representations to explain the mode of operation of a 180 ° plate for linearly or circularly polarized waves.

In Fig. 1 a so-called. Horn 1 is shown in the schematic longitudinal cross section, as it is generally used in cooperation with a parabolic antenna for transmitting or for receiving electromagnetic waves. The horn 1 is constructed in the manner of a waveguide radiator. A waveguide 5 connects to the front, for example, funnel-shaped extension 3, which is terminated at the rear with a short circuit 7. At right angles to this, a waveguide section 9 is shown in the exemplary embodiment shown, which leads, for example, to a converter (not shown).

So that the differently polarized electromagnetic waves can be received with an excitation and feed system according to FIG. 1 and a downstream converter or corresponding polarizations can be sent, it is necessary that the E-vector in the waveguide section 9 perpendicular to the plane of the drawing or perpendicular to the narrow waveguide side is aligned.

In the excitation or feed system, a so-called polarizer 15 is first rigidly installed in the receiving direction adjacent to the funnel-shaped extension 3, which must be aligned perpendicularly or parallel to the E-vector. The polarizer consists, for example, of a dielectric Platelet which causes an at least approximately 90 ° phase shift for the E-vector in the frequency range, for example 11.7 to 12.5 GHz.

This polarizer 15 is followed by a so-called polarization converter 17 in the direction of reception of the electromagnetic waves, which, for example, causes a 180 ° phase shift for the E-vector for the frequency range from 10.95 to 12.75 GHz in accordance with the following explanations. This polarization converter 17 can be pivoted about its longitudinal axis 19 at least in a partial angular range. For this purpose, the longitudinal axis can protrude through the rear short circuit 7, where a motor drive (not shown in more detail), as a rule electromotive, is located, for which the polarization converter 17 can be pivoted into predetermined angular positions.

The reception of the different electromagnetic polarizations is explained in more detail below. 2a to 3d, the case is initially shown in which the front polarizer 15, in contrast to the illustration according to FIG. 1, is not fixed and installed in a vertical orientation but in a horizontal position. In contrast, the polarization converter 17 is rotated into the different representations shown in FIGS. 2a to 3d. 1, the received polarization is exemplified on the left using the E-vector 21. The position of the front polarizer 15 and the downstream polarization converter 17 are shown in an axial view in their respective position, the middle E-vector representation and the E-vector representation behind the polarization converter 17 in front of the waveguide section.

A vertical linear polarization is illustrated in FIG. 2a by a vertically oriented e-vector 21.

Since the e-vector 21 is oriented transversely to the polarizer 15, this has no influence on the spatial orientation of the e-vector. The downstream polarization converter 17 is aligned parallel to the E vector. In addition to a certain, slight, negligible attenuation, the polarization converter 17 does not cause any changes, so that the vertical position of the e-vector 21 ″ also after the polarization converter 17 parallel to the position of the e-vector 21 ′ after or the e-vector 21 the polarizer 15 remains unchanged.

In the exemplary embodiment according to FIG. 2b, a linear polarization orthogonal to FIG. 2a with an E vector 21 lying horizontally is explained. The polarizer 15 lying parallel to this likewise only leads to a negligible attenuation without the E-vector 21 being changed in its spatial position. With a corresponding orientation of 45 °, the downstream polarization converter 17 causes the horizontal E vector 21 'to be reflected in the vertical position, so that this polarization 17 also has the same position at the output as in FIG. 2a.

This also results in a more detailed representation from FIGS. 4a and 4b, to which reference is made below.

4a, the polarization converter 17 is pivoted at a 45 ° angle to the vertical in the case of a horizontal e-vector 21 '. The vector decomposition perpendicularly and in the plane of the polarization converter 17 results in the vectors shown in dashed lines in FIG. 4a.

The component of the decomposed E-vector 21 lying perpendicular to the plane of the polarization converter 17 is now opposite the component perpendicular thereto is 180 ° out of phase, so that this component now assumes the position shown in FIG. 4b. The component lying parallel to the plane of the polarization converter 17 remains unchanged, so that the sum of the two components now results in the e-vector 21 ″ rotated by 90 °.

The two cases in which the differently circularly polarized waves are received are discussed below.

2c shows the case when a circularly polarized wave is received. Since the circularly polarized wave is caused by the fact that the E-vector is phase-shifted by 90 ° with respect to two mutually perpendicular axes, a 90-degree phase shifter in the manner of the polarizer 15 is always a phase shift of the E-vector component in the plane of this plate 90 ° so that the two orthogonal components of the e-vector after the polarizer 15 are in the same phase with each other and thus a linear e-vector 21 'rotated by 45 ° to the plane of the polarizer is generated.

The downstream polarization converter 17, on the other hand, is pivoted in the opposite direction by 22.5 ° to the vertical, as is shown enlarged on the basis of FIG. The linear e-vector 21 ', which is oriented at 45 ° to the vertical, gives a component decomposition as shown in broken lines in FIG. 5a. Since again only the smaller component of the e-vector 21 'is phase-shifted by 180 ° in the plane of the polarization converter 17, the phase shift of this component leads to an e-vector 21''which now assumes an exactly vertical position. In general, in a polarization converter with a 180 ° phase shift - as can also be seen in principle from FIGS. 4 and 5 - the linear E vectors always mirrored around the plane of the polarization converter, whereby the orthogonality of two vertical incoming E-vectors in relation to the outgoing E-vectors is maintained.

FIG. 2d relates to the case opposite to FIG. 2c in the case of an opposite circular polarization, which is first of all via the polarizer 15 in a linearly polarized E-vector 21 ′ oriented at −45 ° to the vertical and then via the correspondingly opposite to FIG. 5a 22.5 ° adjusted plane of the polarization converter 17 also leads to a vertically aligned E-vector 21 ''.

From the system analysis according to FIGS. 2a to 2d it follows that for receiving a linear vertical polarization according to FIG. 2a the 180 ° polarization converter 17 vertically, for receiving a horizontal polarization according to FIG. 2b the plane of the polarization converter 17 by 45 ° Vertical, and in order to receive a positive and negative circularly polarized wave, the plane of the polarization converter 17 must be pivoted by + or -22.5 ° to the vertical in accordance with the exemplary embodiment according to FIGS. 2c and 2d. In the four cases mentioned, with the four different input polarizations, a vertically lying E-vector is always reached at the output, which can now be fed into a waveguide branching off from the receiver system.

Similarly, a horizontal output vector can also be achieved for all four input polarizations, as can be seen from FIGS. 3a to 3d.

When used as an excitation system, the conditions explained apply analogously, with the electromagnetic wave above the waveguide section 9 is fed into the horn 1. With corresponding positions of the polarization converter 17, depending on the position of the polarization converter 17, a linear vertical or horizontal or alternatively a right and left circular polarization can be generated from a horizontally oriented e-vector.

In a departure from the exemplary embodiment shown, the front polarizer 15 can also be brought into a stationary vertical position instead of the horizontal position. This has no fundamental influence and leads to the same results.

It is also clear from the exemplary embodiment described that the maximum pivoting angle range for the plane of the polarization converter 17 only has to range from + 45 ° to -22.5 ° or from -45 ° to + 22.5 °, ie 67 Does not exceed 5 °. Corresponding exact retrieval of one of the explained angle settings can be reproduced via operation of the motor drive via certain presettable locking points.

Instead of the plate-shaped dielectric polarizer 15 and polarization converter 17 explained, other components which produce a 90 ° or 180 ° phase shift can also be used. For example, cross-section-reducing waveguide constrictions that bring about the desired phase shift come into question.

When using dielectric platelets as phase shifters, the dielectric platelet for the polarization converter 17 can, for example, be approximately twice as long as the polarizer 15 with the same thickness. Of course, however, both components 15 and 17 could also have approximately the same length and size, in which case then As a rule, the thickness of the polarization converter 17 is approximately twice as large as the thickness of the polarizer 15, in order thereby to bring about a phase shift which is twice as great, namely by 180 ° compared to 90 ° for the polarizer 15.

For the sake of completeness, it should be noted that, of course, a phase shifter component can also be used as the polarizer 15, which produces a phase shift that is 180 ° larger, for example 270 °. All other phase shifts that are larger by 180 ° ultimately only result in a basic phase shift of 90 °. In addition, larger phase shifts do not make sense, since these also only result in a 90 ° phase shift in terms of their end effect with only greater damping.

The use of a polarization switch enables the simultaneous reception of both orthogonal polarizations after the 180 ° plate.

Claims (9)

1. An exciting or feed system, more particularly for a parabolic antenna for transmitting and receiving of either orthogonally linearly polarized or orthogonally circularly polarized electromagnetic waves, comprising two phase shifting components arranged in a wave guide section (15) which in the direction of propagation of the electromagnetic wave are arranged one behind the other, characterized in that the component which is the first in the receiving direction and is the second in the direction of transmission is in the form of a 90° or, respectively, 90°·(2m - 1) phase shifter (15) (m = 1, 2,...) and the second component following the same in the receiving direction which is the first component in the transmission direction is in the form of a 180° or, respectively, 180°·(2m - 1) phase shifter (17) and in that the 90° phase shifter component (15) has a parallel or perpendicular alignment in relation to a linear polarization and in that the 180° phase shifter component (17) is able to be rotated in an angular range of 67.5° around the direction of propagation of the electromagnetic wave.
2. The exciting or feed system as claimed in claim 1, characterized in that the 90° phase shifter component (15) and/or the 180° phase shifter component (17) is or are designed in the form of dielectric plates.
3. The exciting or feed system as claimed in claim 1, characterized in that the 90° phase shifter component (15) and/or the 180° phase shifter component (17) is or are designed in the form of cross section constricting wave guide constrictions.
4. The exciting or feed system as claimed in any one of the claims 1 through 3, characterized in that a polarization switch is arranged following the 180° phase shifter component (17) in the receiving direction.
5. The exciting or feed system as claimed in any one of the claims 1 through 4, characterized in that the 180° phase shifter component (17) is able to be rocked out of a position, which is parallel or perpendicular to the E vector (21, 21' and 21'') of a linear polarization at least through + or - 45° in order to be able to receive both orthogonal linear polarizations adjustably.
6. The exciting or feed system as claimed in any one of the claims 1 through 5, characterized in that for receiving both oppositely polaraized circular polarizations the 180° phase shifter component (17) is able to be rotated at least between + or - 22.5° in relation to the position of the 90° phase shifter component (15) or the plane which is perpendicular thereto.
7. The exciting or feed system as claimed in claim 5 or in claim 6, characterized in that the range of angular rotation of the 180° phase shifter component (17) amounts top 67.5°.
8. The exciting or feed system as claimed in any one of the claims 1 through 7, characterized in that the 90° phase shifter component (17) is designed for a frequency range of 11.7 to 12.5 GHz.
9. The exciting or feed system as claimed in any one of the claims 1 through 8, characterized in that the 180° phase shifter component (17) is designed for a frequency range of 10.95 to 12.75 GHz.

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