EP0134611B1 - A flat microwave emitting or receiving antenna array, and microwave signal emitting or receiving system comprising a such flat antenna - Google Patents

Description

The present invention relates to a planar antenna with an array of receiving elements, said antenna comprising on the one hand first and second plane arrays of microwave transmission lines, electrically independent and each carried by a thin dielectric sheet and situated respectively on the side and on the other of a first layer and coupled, for the reception, or the emission, of the signals, with first recesses provided in the first layer and according to a coupling produced by as many receiving or excitatory ends, as there are has receiving elements, said ends being arranged along two perpendicular axes of these recesses, and on the other hand of the second and third layers situated with respect to said first layer on the other side of dielectric sheets one and the another respectively of the two and themselves comprising, aligned with said first recesses, second and third recesses, the third of which are short-circuited d in a plane parallel to the faces of the layers, and said first, second and third layers being either metallic or dielectric with metallization of the walls of the recesses, characterized in that each end section of the single end, opposite to said receiving or exciting ends, of the two networks of transmission lines also forms an excitation or receiving probe and is coupled to a waveguide situated at the rear of the antenna and oriented towards the rear of the latter, said waveguide comprising successively and in alignment a first recess in the rear layer, called the third, of the antenna, a second recess in the central layer, called the first, and, in the front layer called the second, a third recess short-circuited in a plane parallel to the faces of the layers, to a depth equal to that of the short-circuit plane of the receiving elements of the front face of the antenna.

The invention also relates to a system for transmitting or receiving microwave signals equipped with such an antenna, and finds an important application in systems for receiving 12 gigahertz television signals, in particular television signals retransmitted by the through geostationary satellites.

European patent application EP-A-0 108 463 describes a planar microwave antenna comprising an array of radiating or receiving elements produced on the one hand from three layers and on the other hand from two supply networks placed respectively between these layers for receiving signals. More specifically, the elements include a first layer with a first circular recess, first and second networks of microwave transmission lines located on either side of this first layer and coupled for receiving signals with each recess along two perpendicular axes. (but parallel from one element to another) and, on the other side of both of these so-called supply networks, a second and a third layer with circular recesses corresponding to the first, the three layers or plates thus provided being metallic or made of a dielectric material with metallization of the walls of the recesses which pass through them. The recesses of the back plate or layer are also short-circuited, to a depth close to X / 4 in general.

In this document, however, the following drawback appears, namely that the supply networks collecting the signals which propagate in the recesses are not in the same plane but at a distance from each other equal to l thickness of the first layer and that this arrangement results in a phase shift between the signals received by one and by the other network.

A first aim of the invention is therefore to propose a planar antenna with arrays of elements in which the above-mentioned drawback is completely eliminated.

To this end, the invention relates to, in a reception or transmission system taking into account the reciprocal nature of the antennas, microwave signals with orthogonal polarizations, an antenna characterized in that each terminal section of the single end, opposite at said receiving or exciting ends, of the two networks of transmission lines also forms an exciting, or receiving, probe and is coupled to a waveguide located at the rear of the antenna and oriented towards the rear of the latter , said waveguide comprising successively and in alignment a first recess in the rear layer, called the third, of the antenna, a second recess in the central layer, called the first, and, in the front layer called the second, a third recess short-circuited in a plane parallel to the faces of the layers, to a depth equal to that of the short-circuit plane of the receiving elements of the front face of the antenna.

The structure thus proposed ensures, thanks to the presence, on the back of the antenna, of an element inverted with respect to the receiving elements of the front face, the reshaping, the rigorous synchronization of the signals traversing respectively each network of transmission: in fact, in this inverted element but not similar to the others, the excitation probes re-emitting the signals they carry have the same "vertical" deviation as those of the elements of the front face, deviation which is equal to thickness of the central layer. This provides a broadband antenna.

French patent application FR-A-2 408 921 describes a structure having certain analogies with the present antenna output, in that said structure comprises metallized dielectric layers comprising aligned recesses and enclosing transmission lines coupled to the space delimited by these recesses. However, in this structure, said recesses are slits resulting in a lowering of the radiation frequencies by creation of phase delays, which is not compa In the case of the present antenna outlet, in which, the recesses being circular, on the contrary, these recesses are associated with means for eliminating delays which appeared on reception of the signals in the recesses.

Another object of the invention is to provide an antenna located in the center of the latter and therefore avoiding the installation of additional transmission line lengths, which would adversely affect the efficiency of the antenna.

To this end, the invention relates either to the antenna which has just been described, with three plates and two networks of transmission lines, or, more simply, to a flat antenna with networks of receiving elements, said antenna comprising a on the one hand a planar network of microwave transmission lines and on the other hand the first and second layers enclosing said network and themselves comprising, respectively, first recesses and second recesses aligned with the first but short-circuited in a plane parallel to the faces of the layers, said grating being coupled, for the reception, or the emission, of microwave signals with a single polarization, with said recesses according to a coupling produced by as many receiving or excitatory ends, as there are receiving elements, and said first and second layers being either metallic or dielectric with metallization of the walls of the recesses, characterized in that the end section of the end ity single, opposite to said receiving or exciting ends of the network of transmission lines also forms an exciting probe, or receiver, and is coupled to a waveguide located at the rear of the antenna and oriented towards the rear of the latter, said waveguide comprising successively and in alignment a first recess in the rear layer, called the second layer, of the antenna and, in the front layer, said first layer, a second recess short-circuited in a plane parallel to the faces of the layers, at a depth equal to that of the short-circuit plane of the receiving elements of the front face of the antenna.

With such a structure, the presence of additional transmission lines is avoided, but also the installation of external connectors since the antenna according to the invention leads directly to the reception head or heads of the system.

• - la figure 1 est une vue partielle de la face arrière de l'antenne selon l'invention;
• - la figure 2 est une coupe selon l'axe AA de la figure 1.

The features and advantages of the invention will now appear more precisely in the description which follows and in the appended drawings, given by way of nonlimiting example and in which:

• - Figure 1 is a partial view of the rear face of the antenna according to the invention;
• - Figure 2 is a section along the axis AA of Figure 1.

The planar microwave antenna according to the invention comprises, with reference to the figures, an array of receiver elements produced in the following manner. On either side of a first layer 10, in which are provided first circular recesses 11 arranged in a two-dimensional network, are placed the conductive strips of two networks 20 and 30 of transmission lines, electrically independent and each carried by a thin dielectric sheet providing mechanical support for these line networks. On the other side of the networks 20 and 30 are provided respectively a second layer 40 with circular recesses 41 and a third layer 50 with circular recesses 51.

These second and third recesses 41 and 51 are located opposite the recesses 11. The recesses 51 of the third layer are short-circuited in a plane 52 parallel to the faces of the layers 10, 40, 50 to a depth of course less than thickness of the layer 50, so as to constitute a reflective plane for the received microwave signals. The recesses 41 end here, without this arrangement being essential, by a tapered flare 42 which contributes to reinforcing the gain. The first, second and third layers 10, 40, 50 are either metallic or made of dielectric material with metallization of all the walls of the recesses 11, 41, 51 which pass through them respectively.

The ends of the networks 20 and 30 of suspended ribbon transmission lines are arranged, on the receiving element side, along two perpendicular axes opposite the recesses 11 of these receiving elements. These ends (not shown here because of the increase in complexity of the figures which would result therefrom) form, in a known manner, excitation probes, carrying out in each of the elements the guide-network coupling which allows the reception of microwave signals from the medium of spread; the penetration lengths of these probes can possibly be different from each other in order to optimize this coupling. From these ends which are equal in number to that of the receiving elements, the networks 20 and 30 progress in successive stages of combination towards a single opposite end, 121 and 131 respectively, constituting a point of convergence reached after electrical paths of equal length. These two ends 121 and 131 collect, for one, the set of received microwave signals having respectively a determined linear polarization and, for the other, the set of received microwave signals having the perpendicular linear polarization.

A single circular waveguide 60, located here in the center of the rear face of the antenna, is then associated with these two ends 121 and 131 in the following manner. This waveguide 60 occupies a position opposite to that of the waveguides formed in the receiving elements by the association of successive recesses 41, 11, 51, which means, more precisely, that this guide 60, oriented towards the the rear of the antenna successively comprises a circular recess 65 in the rear layer 50 of the antenna, a circular recess 61 in the central layer 10, and a circular recess 64 in the front layer 40. Only the latter recess 64 ( as in the case of rear recesses 51 of the antenna receiving elements) is short-circuited in a plane 62 parallel to the faces of the layers 10, 40, 50, to a depth of course less than the thickness of the layer 40, this depth being further here equal to that provided for the short-circuit planes 52 in the recesses 51.

This structure of the waveguide 60 being specified, terminal sections 122 and 132 of the ends 121 and 131 of the transmission networks 20 and 30 are put in place opposite the recesses 65, 61, 64, in a similar manner to the positioning. places opposite ends of the arrays 20 and 30 in each of the receiver elements oriented towards the front of the antenna, so as to also constitute excitation probes. It then appears now that if one of the networks, in this case, is reached first by the microwave signals arriving from the propagation medium and penetrating into the receiving elements, the advance phase shift created in this network is compensated by the phase shift in the opposite direction obtained during the retransmission in the waveguide 60 of the signals present on the terminal sections 122 and 132 after their progression through the networks 20 and 30, the lengths of these sections forming exciting probes being , possibly also reversed if they are different from each other.

The microwave signals received being thus again rigorously in phase, it only remains to place in the waveguide 60 a depolarizing structure (not shown, because of known type: it is generally a dielectric wafer placed longitudinally and diametrically in the guide), then a mode separator (therefore having two outputs as symmetrical as possible towards two frequency converters) to again dispose of microwave signals with orthogonal polarizations which had been emitted (or retransmitted by the geostationary satellites). The mode separator can be for example such as that described in the article "A wide-band square-waveguide array polarizer" published in the journal IEEE Transactions on Antennas and Propagation, May 1973, pages 389 to 391 (see in particular the figure 1 of this document). The two frequency converters, or reception heads, grouping the electronic circuits associated with the antenna can be in particular, in the case of the reception of 12 gigahertz television signals transmitted via satellites, of the head type reception described in the review "L'Onde Electrique", volume 62, n ° 3, March 1982, pages 39 and 40.

Of course, the present invention is not limited to the embodiment described above and shown, from which variants can be proposed without departing from the scope of the invention. In particular, the proposed antenna remains advantageous even for an antenna called upon to receive signals of only one type of polarization and comprising for this purpose only one network of transmission lines enclosed between two layers; indeed, even in this case, the proposed structure remains very economical, for the reasons indicated above, compared to current solutions with additional transmission lines and external connectors. In addition, the invention extends to any system for receiving microwave signals comprising a planar antenna as described, the choice of the example of 12 gigahertz television signals not being limiting of the operating frequency or of the nature of this system (it can be incorporated into terrestrial as well as satellite transmission networks).

Claims (4)

1. A planar antenna array of receiving elements including first and second planar arrays of high-frequency transmission lines, electrically independent and each of them supported by a thin dielectric film, situated on either one of the two sides respectively, of a first layer and, for the reception or transmission of orthogonally polarized high-frequency signals, coupled to first cavities provided in the first layer and having a coupling realised by as many receiving or exciting probes as there are receiving elements, the said probes being located along two perpendicular axes of these cavities, and also third and fourth layers disposed with respect to the said first layer on the opposite sides of either one of the two sides respectively, of the two dielectric films and they themselves including second and third-layer cavities, which are in-line with the said first-layer cavities, said third-layer cavities being short-circuited in a plane parallel to the surfaces of the films, and the said first, second and third layers being either metal-plated or dielectric material with metal-plated cavity walls, characterized in that each terminating section (122, 132) of the single probe, which probe faces the said receiving or exciting probes of the two arrays of transmission lines also constitutes an exciting or receiving probe, and is coupled to a waveguide located at and opening toward the rear of the antenna, said waveguide including, in succession and in line, a first cavity in the rear layer, called the third layer of the antenna, a second cavity in the central layer, called the first layer, and disposed in the front layer, called the second layer, a third cavity short-circuited in a plane parallel to the surfaces of the layers, at a depth equal to that of the short-circuiting plane of the receiving elements of the surface before the antenna.

2. A planar antenna comprising an array of receiving elements, including an array of high-frequency transmission lines supported by a thin dielectric film, and also first and second layers into which the said array is inserted and the layers themselves including first cavities and second cavities which are in line with the first cavities but short-circuited in a plane parallel to the surfaces of the layers, said array being coupled for the reception or transmission of the high-frequency signals at a single polarization with the said cavities by means of a coupling by as many receiving or exciting probes as there are receiving elements, and the first and second layers being made of metal or of a dielectric material with metal-plated walls of the cavities, said antenna being characterized in that the terminating section of the single probe, which probe faces the said receiving or exciting probes of the array of transmission lines also constitutes an exciting or receiving probe, and is coupled to a waveguide located at and opening toward the rear of the antenna, said waveguide including, in succession and in line, a first cavity in the rear layer, called the second layer of the antenna and, in the front layer, called the first layer, a second cavity which is short-circuited in a plane parallel to the surfaces of the layers, at a depth equal to the depth of the short-circuiting plane of the receiving elements of the front surface of the antenna.

3. A planar antenna as claimed in one of the Claims 1 and 2, characterized in that the lengths of the terminating sections forming exciting or receiving probes in the receiving elements of the surface before the antenna and also in the waveguide of the surface at the rear of the antenna are inverted if they are different from one another.

4. A system for transmitting or receiving high-frequency signals comprising a planar antenna having an array of radiating or receiving elements as claimed in one of the claims 1 to 3.

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