Arrangement and method for electronically tracking RF reflector antennas

Abstract

A high-frequency reflector antenna (1) is provided that includes at least one main reflector (2), at least one sub-reflector (3) and at least one horn (4). The stationary elements (5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8) for influencing the direction-dependent reception characteristic are present in the beam path between the main reflector (2) and the horn (4). The stationary elements (5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8) may protrude into the free aperture area (6) of the horn (4). The stationary elements (5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8) are switchable dipole elements (5.1.1, 5.2.1, 5.3.1, 5.4.1, 5.5.1, 5.6.1, 5.7.1, 5.8.1) that are arranged with their dipole axis (15) in a manner to influence the reception characteristics of elliptically to circularly or linearly polarised high-frequency radiation.

Claims

1. A high-frequency reflector antenna comprising: a main reflector; a sub-reflector; a horn, wherein the horn includes a free aperture area and a nearfield area; stationary elements, wherein the stationary elements are positioned in a beam path between the main reflector and the horn, wherein the stationary elements are configured for influencing direction-dependent reception characteristics, wherein the stationary elements protrude into the free aperture area of the horn, wherein the stationary elements are arranged in the near-field area of the horn, wherein the stationary elements include switchable dipole elements each of which switchable dipole elements includes a respective dipole axis, and wherein each of the switchable dipole elements is arranged with its respective dipole axis, along a tangent of a helix which extends coaxially to a horn axis, in order to influence direction-dependent reception characteristics of elliptically or circularly polarised high-frequency radiation, or wherein each of the switchable dipole elements is arranged with its respective dipole axis alternately parallel to a tangent of an outer surface of the horn and parallel to the horn axis in order to influence the reception characteristic of linearly polarised high-frequency radiation, or wherein each of the switchable dipole elements is arranged with its respective dipole axis aligned alternately parallel to the tangent of the outer surface of the horn and radially to the horn axis with only a part of a length of the respective dipole element protruding into the free aperture area of the horn in order to influence the reception characteristic of linearly polarised high-frequency radiation.

2. The high-frequency reflector antenna according to claim 1, and further including, at least one control unit, a) wherein the at least one control unit is operative to activates or tune or both activate and tune the switchable dipole elements to influence the direction-dependent reception characteristic, individually or in groups or both individually and in groups, and b) wherein the at least one control unit is operative to correlate at least one signal strength of at least one reception unit with an activation or tuning pattern or both activation and tuning patterns of the switchable dipole elements to influence the direction-dependent reception characteristic, and c) wherein the at least one control unit in dependence of a correlated pattern is operative to provide control signals for a mechanical change in direction of the high-frequency reflector antenna.

3. The high-frequency reflector antenna according to claim 2, wherein a dipole length of the stationary elements, in the direction of the dipole axis, is between 11 mm and 15 mm for the K.sub.u-band and between 6 mm and 10 mm for the K.sub.a-band.

4. The high-frequency reflector antenna according to claim 3, wherein the switchable dipole elements influence the direction-dependent reception characteristic responsive to activation either individually or in groups.

5. The high-frequency reflector antenna according to claim 4, wherein the switchable dipole elements influence the direction-dependent reception characteristic responsive to being switched on and off or tuned by a high-frequency-capable electronic switching element.

6. The high-frequency reflector antenna according to claim 3, wherein the dipole length of the switchable dipole elements, in the direction of the dipole axis, is approximately 13 mm for the K.sub.u-band and 8 mm for the K.sub.a-band.

7. The high-frequency reflector antenna according to claim 6, wherein the switchable dipole elements influence the direction-dependent reception characteristic responsive to activation individually or in groups or both individually and in groups.

8. The high-frequency reflector antenna according to claim 7, wherein the switchable dipole elements influence the direction-dependent reception characteristic responsive to being switched on and off or tuned by a high-frequency-capable electronic switching element.

9. The high-frequency reflector antenna according to claim 1, wherein the switchable dipole elements influence the direction-dependent reception characteristic responsive to activation individually or in groups or both individually and in groups.

10. The high-frequency reflector antenna according to claim 9, wherein the switchable dipole elements influence the direction-dependent reception characteristic responsive to being switched on and off or tuned by a high-frequency-capable electronic switching element (19).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The exemplary embodiment will now be described in detail with reference to the following figures, in which

(2) FIG. 1 shows a view of a high-frequency reflector antenna according to the exemplary embodiment, of the Cassegrain or Gregory type.

(3) FIG. 2 shows an enlarged cut-out of FIG. 1, showing the elements for influencing the direction-dependent reception characteristic.

(4) Figure shows a side view of the aperture opening of the horn with elements arranged above it for influencing the direction-dependent reception characteristic.

(5) FIG. 4 shows a top view of the horn opening with two groups of annularly arranged elements for influencing the direction-dependent reception characteristic.

(6) FIG. 4.1 for circularly polarised transmit radiation.

(7) FIG. 4.2 for linearly polarised transmit radiation.

(8) FIG. 5 shows two sketches of a relative arrangement of the signal source and high-frequency reflector antenna with plotted three-dimensional antenna diagram.

(9) FIG. 5.1 for an unchanged antenna diagram.

(10) FIG. 5.2 for a changed antenna diagram.

(11) FIG. 6 shows a sketch of a sequence of differently activated elements for influencing the direction-dependent reception characteristic with plotted received signal strength and directional information, using as an example the elements influencing circularly polarised transmit radiation.

(12) FIG. 7 shows a sketch of an attachment on the horn as a wave trap for illustrating the free aperture area, when such an attachment is used.

DETAILED DESCRIPTION

(13) FIG. 1 shows a generic high-frequency reflector antenna 1 of the Cassegrain or Gregory type comprising a main reflector 2, s sub-reflector 3 and a horn 4 for converting the directional electro-magnetic radiation to be received. In the high-frequency reflector antenna 1 shown here, stationary elements 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7 and 5.8 are arranged for influencing the direction-dependent reception characteristic of the high-frequency reflector antenna 1. The elements protrude into the free aperture area 6 of the horn 4 and are thus arranged in the near-field area 7 of the horn 4. The encircled area A around the sub-reflector 3 and the horn 4 is shown enlarged in the next figure, FIG. 2.

(14) In FIG. 2, eight elements 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7 and 5.8 in total for influencing the direction-dependent reception characteristic of the high-frequency reflector antenna 1 can be seen on the rim of the horn 4. Four of the eight elements 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7 and 5.8, respectively, are a first group G1 consisting of elements 5.1, 5.3, 5.5 and 5.7, and a second group G2 consisting of elements 5.2, 5.4, 5.6 and 5.8 respectively form a common group of elements for influencing the opposing circularly polarised high-frequency radiation. These elements 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7 and 5.8 divided into the two groups G1 and G2 protrude into the free aperture area 6 of the horn 4 to such an extent that they just protrude into the near-field area 7, which is very sensitive to interferences. In order to avoid the elements 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7 and 5.8 from interacting with the high-frequency field of the transmit radiation, when the high-frequency reflector antenna 1 is in transmit mode, the dipoles 5.1.1, 5.2.1, 5.3.1, 5.4.1, 5.5.1, 5.6.1, 5.7.1 and 5.8.1 present on the elements 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7 and 5.8 comprise a length specific for a frequency of the transmitter to be received, which for the transmit frequency show a distinctly lesser interaction with the high-frequency field of the transmit radiation. All the same, any positioning of metallic conductors in the near-field area 7 of the horn 4 of a high-frequency reflector antenna 1 indicates an interference of the high-frequency field in this location, an interference which is very difficult or impossible to predict and which is to be avoided if possible.

(15) Surprisingly, however, the high-frequency field in the near-field area 7 in transmit mode of the high-frequency reflector antenna 1 remains unaffected, but at least the interaction between the elements 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7 and 5.8 and the high-frequency radiation in the near field 7 is so small that the high output of the high-frequency reflector antenna 1 in transmit mode is not fed back into a control electronics 10 (not shown in the drawings), which is arranged downstream of the horn 4 and the elements 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7 and 5.8. The surprising behaviour of the elements 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7 and 5.8 is thought to be due to the fact that in the transmit mode of the high-frequency reflector antenna, the near field 11 of the horn 4 is structured in a way different from the reception mode of the high-frequency reflector antenna 1. The different structuring of the near field 11 may be understandable, since the radiation source 12 (not shown) necessary for the transmit mode builds a slightly different near field 11′ at the end of the hollow conductor 13 (not shown) connected with the horn 4 from that which exists there in the reception mode of the high-frequency reflector antenna 1. However, the exact structuring of the near field 11 and 11′, although possible, is insufficient even with computer-aided means for theoretically simulating the wave properties in the near field 11 and 11′ of a Cassegrain or a Gregory antenna.

(16) In order to enable signal source tracking to be performed specifically with respect to a circular polarisation of the high-frequency radiation, the elements 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7 and 5.8 in the two groups G1 consisting of odd-numbered elements 5.1, 5.3, 5.5 and 5.7, and G2 consisting of even-numbered elements 5.2, 5.4, 5.6 and 5.8 are arranged in such a way that electronically switchable dipole arrays 5.1.1, 5.3.1, 5.5.1 and 5.7.1 and 5.2.1, 5.4.1, 5.6.1 and 5.8.1 arranged on these elements 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7 and 5.8 are arranged with their dipole axis 15 (FIG. 4.1) tangentially on a helix 17 coaxial to the horn axis 16.

(17) In order to enable signal source tracking to be performed specifically with respect to a linear polarisation of the high-frequency radiation, the elements 5.1′, 5.2′, 5.3′, 5.4′, 5.5′, 5.6′, 5.7′ and 5.8′ in the two groups with G1′ consisting of odd-numbered elements 5.1′, 5.3′, 5.5′ and 5.7′, and G2′ consisting of even-numbered elements 5.2′ 5.4′, 5.6′ and 5.8′ are arranged in such a way that electronically switchable dipole arrays 5.1.1′, 5.3.1′, 5.5.1′ and 5.7.1′ and 5.2.1′, 5.4.1′, 5.6.1′ and 5.8.1′ arranged on these elements 5.1′, 5.2′, 5.3′, 5.4′, 5.5′, 5.6′, 5.7′ and 5.8′ are arranged alternately with their dipole axis 15′ (FIG. 4.2) once in parallel to a tangent 4.2 of the outer surface 4.1 and once in parallel to the horn axis 16.

(18) FIG. 3 shows a side view of the horn 4 together with the sub-reflector 3, which is hereby the sub-reflector of a Cassegrain antenna. For clarification of the electronically switchable dipole arrays 5.1.1, 5.3.1, 5.5.1 and 5.7.1 and 5.2.1, 5.4.1, 5.6.1 and 5.8.1 tangentially aligned with a helix 17, an imaginary helix 17 is indicated in FIG. 3, wherein the gradient of the helix 17 does not necessarily correspond to the gradient of the electrical, circularly polarised field to be received. For a wavelength of the high-frequency field of a few millimetres this gradient shown in FIG. 3 is clearly too flat. Rather the gradient of the imaginary helix 17 on which the switchable dipole arrays 5.1.1, 5.3.1, 5.5.1 and 5.7.1 and 5.2.1, 5.4.1, 5.6.1 and 5.8.1 are tangentially arranged, presumably corresponds to the alignment of the locally extended electrical field in the near-field area 7 of the horn 4.

(19) The switchable dipole arrays mentioned in the beginning are illustrated in both FIGS. 4.1 and 4.2 by a top view of the open horn 4. FIG. 4.1 clearly shows that for circular polarisation switchable dipole arrays 5.1.1, 5.3.1, 5.5.1 and 5.7.1 and 5.2.1, 5.4.1, 5.6.1 and 5.8.1 sit on the elements 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7 and 5.8, which with their dipole axis 15 are aligned along a tangential direction of a right-wound and a left-wound helix 17 and 17′. The switchable dipole arrays 5.1.1, 5.3.1, 5.5.1 and 5.7.1 and 5.2.1, 5.4.1, 5.6.1 and 5.8.1, respectively, consist of conductor track elements 18 and 18′ applied to a dielectric carrier, which lie coaxially opposite each other and in the present circuit are electrically conductively connected with each other via an electronic switching element 19, for example a PIN diode. In the electrically conductive state of the electronic switching element 19, the circuit board elements 18 and 18′ together with the conductive electronic switching element 19 form a very small dipole antenna, which when the latter is activated, cause a spatially locally limited impedance change of the near-field area 7, wherein the impedance change is ramp-like over time. Insofar as the electronic switching element 19 between two conductor track elements 18 and 18′ is rendered non-conductive—with PIN diodes by switching a direct current across the two circuit board elements 18 and 18′ off—the resonance condition is interrupted, but at the least the impedance change of the near-field area 7 is decreased, which, among others, depends upon the length of the electrically conductive dipole. Since the individual dipole arrangement, after the electronic switching element 19 has been switched off, is no longer in resonance with the local high-frequency field, at the least however causes only a negligible change in the impedance of the near-field area 7, it absorbs no radiation or at least less radiation, and therefore has no influence or at least only very little influence on the electro-magnetic high-frequency field in the near-field area 7.

(20) According to the idea of the exemplary embodiment, no provision is necessarily made to withdraw part of the reception power in the spatial area which is overshadowed by the switchable dipole arrays 5.1.1, 5.3.1, 5.5.1 and 5.7.1 and 5.2.1, 5.4.1, 5.6.1 and 5.8.1, from the total reception power by electrical discharge, but rather it is the idea of the exemplary embodiment to position 7 node points in the near-field area 7, which change the formation of the wave present in the near-field area 7. This change in the boundary conditions for forming a complex structured near field wave is distinctly different from, for example, hollow conductors fitted laterally to the horn with a switchable element for properly short-circuiting a preselected undesirable mode (e.g. a TEM.sub.00, TEM.sub.01) or other mode for selective frequency reception of a non-short-circuited mode.

(21) In order to minimise the interaction of the electrical supply lines 20 for the electronic switching element 19 with the local high-frequency field, provision is made, according to an advantageous development of the exemplary embodiment, for these supply lines 20 to be configured as conductor tracks to extend radially to the horn axis 16, wherein a directional component is arranged distinctly outside the free aperture area 6 of the horn 4 in parallel to the horn axis 16. Due to this arrangement of the supply lines 20, electro-magnetic radiation is prevented from being fed back into the control electronics 10 (not shown) in an undesirable manner in the transmit mode.

(22) FIG. 4.2 reveals that for linear polarisation, switchable dipole arrays 5.1.1′, 5.3.1′, 5.5.1′ and 5.7.1′ and 5.2.1′, 5.4.1′, 5.6.1′ and 5.8.1′ sit on the elements 5.1′, 5.2′, 5.3′, 5.4′, 5.5′, 5.6′, 5.7′ and 5.8′, which dipoles, with their dipole axis 15′, are arranged alternately with their dipole axis 15′ once parallel to a tangent 4.2 of the outer surface 4.1 and once parallel to the horn axis 16. In principle, the elements 5.1′, 5.2′, 5.3′, 5.4′, 5.5′, 5.6′, 5.7′ and 5.8′ work in the same way as the elements 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7 and 5.8 described for circular polarisation, but their spatial alignment is different compared to the spatial alignment of the elements for circular polarisation. As with the elements for circular polarisation, the elements 5.1′, 5.2′, 5.3′, 5.4′, 5.5′, 5.6′, 5.7′ and 5.8′ for horizontal and vertical polarisation perpendicular to each other, are divided into two groups, that is group G1′ consisting of elements 5.1′, 5.3′, 5.5′ and 5.7′ and group G2′ consisting of elements 5.2′ 5.4′, 5.6′ and 5.8′. The first group G1′ therefore, comprises an element 5.1′, for example, in the 12:00 position and an element 5.5′, for example, in the 06:00 position, wherein the dipole 5.1.1′ and 5.5.1′ positioned on it is, respectively, axially aligned in parallel to the horn axis 16. By contrast elements 5.3′ and 5.7′ are arranged, respectively, in the approximately 09:00 position and the approximately 03:00 position, and the dipoles 5.3.1′ and 5.7.1′ are aligned in parallel with a tangent 4.2 of the outer surface 4.1 of the horn 4.

(23) This first group G1′ shows an interaction with a linear polarisation vertical in this view, of the wave front moving towards the aperture area 6 of the horn 4. With respect to the vertically aligned electric vector of the vertical polarisation the two dipoles 5.3.1′ and 5.7.1′ are correspondingly vertically aligned and the two dipoles 5.1.1′ and 5.5.1′ of elements 5.1′ and 5.5′ are axially aligned, corresponding to the spatial phase difference of the high-frequency field in propagation direction of the wave front moving towards the aperture area 6. The spatial alignment of the dipoles 5.1.1′ and 5.5.1′ in the axial direction of the horn 4, which corresponds to the propagation direction of the wave front moving towards the aperture area 6, is due to the fact that these dipoles are interacting both with horizontally polarised wave fronts and with vertically polarised wave fronts. Each group G1′ and G2′ therefore has two elements, respectively, which work polarisation-specifically, and two elements which work polarisation-unspecifically. In order to make the interaction of all to dipoles polarisation- specific, provision is made for the dipoles on the elements 5.1′ and 5.5′ to extend in radial direction, protruding, for a small part of their length, into the free aperture area 6 of the horn 4.

(24) This second group G2′ shows an interaction with a linear polarisation horizontal in this view, of the wave front moving towards the aperture area 6 of the horn 4. With respect to the horizontally aligned electric vector of the horizontal polarisation, the two dipoles 5.8.1′ and 5.4.1′ are correspondingly approximately horizontally aligned, and the two dipoles 5.2.1′ and 5.6.1′ of elements 5.2′ and 5.6′ are axially aligned, corresponding to the spatial phase difference of the high-frequency field in propagation direction of the wave front moving towards the aperture area 6. The spatial alignment of the dipoles 5.2.1′ and 5.6.1′ in the axial direction of the horn 4, which corresponds to the propagation direction of the wave front moving towards the aperture area 6, is due to the fact that these dipoles are interacting both with horizontally polarised wave fronts and with vertically polarised wave fronts. Each group G1′ and G2′ therefore has two elements, respectively, which work polarisation-specifically, and two elements which work polarisation-unspecifically. In order to make the interaction of all dipoles polarisation-specific, provision is made for the dipoles on the elements 5.1′ and 5.5′ to extend in a radial direction, protruding, for a small part of their length, into the free aperture area 6 of the horn 4.

(25) The effect of the influence of the reception characteristic of a high-frequency reflector antenna is shown in FIG. 5. FIG. 5 shows a reflector 30 with a reception lobe 31 projected thereon. The reception lobe 31 is shown as a three-dimensional graph which maps the spatially dependent antenna gain as an improvement of the received signal strength as compared to an antenna without reflector as coherent area of a plot depicted in polar coordinates. The reception lobe 31 thus has no spatial extension or other kind of spatial structure. Rather it maps the above-mentioned improvement as a linear or logarithmic factor in dependence of two spatial angles, i.e. azimuth which on the earth surface corresponds essentially to the compass direction, and elevation which on the earth surface at mid altitudes corresponds essentially to the angle above the horizon. In direction of the symmetry axis 32 of reflector 30, the high-frequency reflector antenna has the highest antenna gain. For a strong signal reception of the signal source, e.g. a satellite signal from the aimed-at satellite 33 sketched here, the symmetry axis 32 is aligned exactly with the position of the aimed-at satellite 33. This ideal situation is shown in the left sub-figure 5.1 of FIG. 5.

(26) Satellites which due to their age are on a so-called “inclined” orbit, i.e. on a no longer exactly geo-stationary orbit around the earth with an angled eclipse with a mostly elliptical orbit compared to the ideal eclipse, describe in relation to the moving observer on the earth surface, a figure-eight orbit 34. In order to track this orbit 34 with a small high-frequency reflector antenna, it is proposed that the alignment of the high-frequency reflector antenna of, for example, a mobile transmission vehicle of a broadcasting station or the alignment of a communication antenna of a commercial ship, a passenger ship or a warship, or finally the communication antenna of an aircraft or that of a rocket, always follows a variable relative position of the satellite 33. To this end the switchable dipole arrays 5.1.1, 5.2.1, 5.3.1, 5.4.1, 5.5.1, 5.6.1, 5.7.1 and 5.8.1 are activated in variable patterns, but usually one after the other, and during activation the received signal strength 41 of the signal source is measured. Insofar as the received signal strength 41 becomes distinctly weaker or may be stronger for a predefined transient activation pattern because the structure of the reception lobe 31 has changed, this is to be understood as an indicator for the signal source outside the alignment of the symmetry axis 32 of the high-frequency reflector antenna 1. By correlating the activation pattern of the electronically switchable dipole arrays 5.1.1, 5.3.1, 5.5.1 and 5.7.1 and 5.2.1, 5.4.1, 5.6.1 and 5.8.1 with the received signal strength 41, which correlates with the antenna diagram 40, directional information can be derived regarding the direction into which the high-frequency reflector antenna 1 can be moved by means of electro-mechanical or hydraulic final control devices, in order to re-align the symmetry axis 32 of the high-frequency reflector antenna 1, which, depending on the position of the reception unit on the high-frequency reflector antenna 1 is pre-defined by the symmetry axis 32 of the reception lobe 31, again with the symmetry axis 32 of the reception lobe 31.

(27) The right sub-figure 5.2 of FIG. 5 shows, how the reception lobe 31′ through selectively changing the spatial reception characteristic comprises a dent, which is linked to a reduction in received signal strength 41 in this spatial area. In order to depict the reception lobe in a two-dimensional manner, a distorted perspective of a two-dimensional diagram 40 has been plotted above the dented reception lobe 31′. The changeability of the reception lobe 31′ with different activation patterns of the electronically switchable dipole arrays is shown in the next figure, FIG. 6.

(28) FIG. 6 is a view into the open horn 4 along the symmetry axis 32 of the reception lobe 31′ with eight different activation patterns of the electronically switchable dipole arrays 5.1.1, 5.2.1, 5.3.1, 5.4.1, 5.5.1, 5.6.1, 5.7.1 and 5.8.1. In this sketch, a black filled area of the respectively drawn element 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7 and 5.8 indicates activation of the respective dipole array 5.1.1, 5.3.1, 5.5.1 and 5.7.1 and 5.2.1, 5.4.1, 5.6.1 and 5.8.1 activated on the respective element 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7 and 5.8. The profile of the reception lobe 31′ of the two-dimensional antenna diagram 40 shown only for the azimuth is drawn around the sketched opening of the horn 4 with elements 5.1.1, 5.3.1, 5.5.1 and 5.7.1 and 5.2.1, 5.4.1, 5.6.1 and 5.8.1, as it would look in FIG. 5.2 when viewed from the target or from the signal source. Starting in the left upper corner of FIG. 6 an electronically switchable dipole array 5.1.1 on the black-filled element 5.1 is activated in the 09:00 position. In consequence, assumed here as an example, the received signal strength 41 is reduced in the signal intensity time diagram 42, which depicts the signal intensity I above time t, of a signal source which has migrated in relation to this direction, as shown in the almost circular antenna diagram 40 with a dent in the 09:00 position. In this example, the electronically switchable dipole arrays 5.1.1, 5.3.1, 5.5.1, 5.7.1 are activated one after the other, overlapping with each other in the switching times t=1, t=2, t=3, t=4, t=5, t=6, t=7 and t=8, which correlates with a reduction in received signal strength 41 of a signal source which has migrated in the respective direction. Insofar as a signal source—by way of example—has migrated in approximately 11:00 direction, the received signal strength 41 will be reduced, in this example by t=2, over a cycle for exactly this activation pattern, which is depicted by the received signal strength 41 plotted over time. For tracking, the high-frequency reflector antenna 1 would therefore have to be guided in approximately the 11:00 direction, in order to standardise the received signal strength 41 for all activation patterns at t=1, t=2, t=3, t=4, t=5, t=6, t=7 and t=8. At this point it is important to emphasise that the formation of the near field 11 in the high-frequency reflector antenna 1 is changed due to the electronically switchable dipoles. Thus, the correlation of the activation pattern at t=1, t=2, t=3, t=4, t=5, t=6, t=7 and t=8 with a change in received signal strength 41 is dependent on the exact formation of the high-frequency wave in the near field 11.

(29) The dented reception lobe 31′ shown in FIG. 5, sub-figure 5.2, is shown here only by way of example. The actual change of the three-dimensional antenna diagram is far more complex and coincides with a distortion and also twisting of the lob shape. For measuring the migration of a target or a signal source the eight patterns shown by way of example in FIG. 6 are activated one after the other, and at the same time as activation takes place, the strength of the signal intensity is measured. Measurements are taken cyclically over a cycle of t=1 over t=2, t=3, t=4, t=5, t=6, t=7 up to t=8, where a further cycle starts which is carried out identically to the start at t=1. This cycle runs with a frequency of 10 Hz to 100 Hz, 100 Hz to 1,000 Hz or 1,000 Hz to 1 MHz, and if it is found that the received signal strength has weakened, then directional information in accordance with the known activation pattern is generated, which the high-frequency reflector antenna has to follow for tracking. For tracking, it is not necessary to constantly interfere with the signal. Rather it is possible to intermittently take measurements of the target or signal source drift.

(30) The method according to the exemplary embodiment is therefore characterised by individual or group activation and/or tuning of the elements for influencing the direction-dependent reception characteristic, correlating at least one signal strength of at least one reception unit with the activation and/or tuning pattern of the elements for influencing the reception characteristic and providing control signals for a mechanical change of direction of the high-frequency reflector antenna in dependence of the measured correlation. To this end provision is made for the control signals for a mechanical change in direction of the high-frequency reflector antenna to be generated by at least one reception unit, based on the correlation of a change in signal strength coupled with the group activation and/or tuning of one of the elements for influencing the direction-dependent reception characteristic. With respect to their spatial arrangement the elements for influencing the direction-dependent reception characteristic can be activated and/or tuned at a constant or randomly variable frequency in a point-symmetrical, rotating or random manner. The activating pattern sequence is of secondary importance as long as the patterns succeed each other quickly enough, e.g. 10 Hz to 100 Hz, 100 Hz to 1000 Hz or 1000 Hz to 1 MHz, in order to ensure uninterrupted reception.

(31) Since the received signal strength 41 can vary significantly, which may depend upon atmospheric disturbances, undesirable beats of adjacent frequencies or other interfering influences, the exemplary embodiment has been developed to provide for the received signal strength 41 to be correlated, not statically with the activation of a specific activation pattern at times t=1, t=2, t=3, t=4, t=5, t=6, t=7 and t=8, but to allow individual activation patterns of a predetermined frequency to follow one after the other in a loop, so that the dent in the antenna diagram shown in FIG. 5.2 goes round in circles. The received signal strength 41 modulated in this way is supplied via a lock-in amplifier to a further stage for phase correlation, wherein this stage for phase correlation correlates the phase of the activation pattern, which runs in circles, with the phase of the signal from the lock-in amplifier. The phase correlation can also be used for deriving directional information, which has the advantage, in contrast to static correlation of the activation pattern with the direction, that interfering frequencies modulated in an undesirable manner onto the high-frequency signal to be received can be suppressed and directional information can be derived in a more secure manner.

(32) In order to change the direction of the high-frequency reflector antenna 1, an electro-mechanical setting means can be provided, or a hydraulic adjusting means. Finally, for a highly precise alignment of the high-frequency reflector antenna 1, a peristaltic piezo motor can vary the position of the freedom levels of the directional high-frequency reflector antenna. In order to prevent mechanical resonance frequencies of the high-frequency reflector antenna 1 with dimensions of 40 cm minor diameter to 3 m minor diameter and of the carrier system from being stimulated in the case of moving high-frequency reflector antennas, such as in the case of a moving transmission vehicle of a broadcasting station, a ship at sea, a moving aircraft or a rocket in flight, provision is made according to an advantageous development of the exemplary embodiment that the activation patterns are varied remotely from a mechanical resonance frequency or at random, at a randomly varying frequency. This ensures that mountings and carrier elements do not become detached due to resonant vibrations, when the system is in use.

(33) Finally, FIG. 7 shows an attachment on a horn, a so-called grooved horn radiator 50, which is used as a wave trap for avoiding undesirable side maxima (side lobes) of a directional radiator. If a grooved horn radiator is used as a wave trap and for better focussing of the transmitting beam, then the free aperture area 6 of the horn 4 is replaced by the free aperture area 51 of the grooved horn radiator 50, for positioning the elements.

REFERENCE LIST

(34) 1 high-frequency reflector antenna 2 main reflector 3 sub-reflector 4 horn 4.1 outer surface 4.2 tangent 5.1 element 5.1′ element 5.1.1 dipole array 5.1.1′ dipole array 5.2 element 5.2′ element 5.2.1 dipole array 5.2.1′ dipole array 5.3 element 5.3′ element 5.3.1 dipole array 5.3.1′ dipole array 5.4 element 5.4′ element 5.4.1 dipole array 5.4.1′ dipole array 5.5 element 5.5′ element 5.5.1 dipole array 5.5.1′ dipole array 5.6 element 5.6′ element 5.6.6 dipole array 5.6.6′ dipole array 5.7 element 5.7′ element 5.7.1 dipole array 5.7.1′ dipole array 5.8 element 5.8′ element 5.8.1 dipole array 5.8.1′ dipole array 6 aperture s 7 near-field area 10 control electronics 11 near field 11′ near field 12 radiation source 13 hollow conductor 15 dipole axis 15′ dipole axis 16 horn axis 17 helix 17′ helix 18 circuit board element 18′ circuit board element 19 switching element 30 reflector 31 reception lobe 31′ reception lobe 32 symmetry axis 33 satellite 34 orbit 41 received signal strength 42 signal intensity time diagram 50 grooved horn radiator 51 aperture area I signal intensity T time