EP0422551B1 - Electronically scanned transmitting antenna - Google Patents

Description

The invention relates to an antenna with electronic scanning in transmission.

A work entitled "space telecommunications" of the technical and scientific collection of telecommunications in particular in its volume I pages 92 to 94 and pages 259 to 261 (Masson, 1982) describes on the one hand the fact of grouping several antennas, fed simultaneously by the same transmitter with the interposition of power dividers and phase shifters, the radiation characteristics of this group depending both on the diagram of each antenna and on the distribution of powers in amplitude and phase. This property is used to obtain a diagram which could not be obtained with a single radiating source. If, in addition, the characteristics of the power dividers and phase shifters are modified by electronic means, it is possible to obtain an almost instantaneous modification of the diagram. The simplest grouping of radiating sources is the network, in which all the sources are identical and are deduced from each other by any translation. One can thus realize rectilinear or planar networks.

This document describes, on the other hand, the use of reflector antennas for the generation of several mobile beams which have the advantage of a low mass linked to the use of optimized amplifier stages. The illumination system of the reflector is generally off-center with respect to the latter so as to avoid any blockage of the radiating opening and to facilitate installation on the platform in the case of a spatial application. The main reflector is for example a paraboloid. The mobile beams are in fact the combination of elementary beams, obtained by placing a set of sources of illumination in the vicinity of the focal point, each source corresponding to an elementary beam.

Because they cannot be placed exactly at the focal point, the illumination is not geometrically perfect and there are phase aberrations which somewhat degrade the radiation performance, therefore decreases in gain compared to the values achievable at home. These degradations are all the more important away from the focus and the curvature of the reflector is large. Reflectors must therefore be made as "flat" as possible, that is to say with a focal distance to large aperture diameter ratio. This leads to large structures which pose problems of precision and mechanical strength.

European patent application EP-A-0 368 121 in the name of the Applicant published on May 16, 1990 and enjoying the priority of November 3, 1988 is a document referred to in Article 54 (3) of the European Patent Convention . This document describes an electronic scanning antenna operating in reception or in emission, comprising a reflector focusing energy, a network of elementary sources located in the focal zone of this reflector, the coverage zone being produced by one or more spots illuminated by one or more beams, each beam being generated by several elementary sources, the elementary sources not used simultaneously being grouped in classes in which only one source can be active, the agility of beams being ensured by a switching of the elementary sources carried out by acting on the power supply of the amplifiers associated respectively with the latter. In this embodiment, it is however necessary for each elementary source: an amplifier, a filter, a controllable phase shifter, and a controllable attenuator, as well as the electronics for controlling the phase shifter, the attenuator, and the power supply of the amplifier.

It is known from the document International Symposium Digest Antennas and Propagation, vol. II, June 6, 1988, Syracuse NY, pages 506-509: R. Lenormand et al. : "A versatile array-fed reflector antenna for satellite communications, part B- transmission" a multibeam antenna adjustable by switching comprising an energy-focusing reflector, a network of elementary sources located in the focal zone of the reflector so as to carry out the synthesis of the electromagnetic field in this focal area and an electronic unit comprising an electronic control of phases and amplitudes, an amplification stage with m inputs and m outputs, and a switch. This antenna can be reconfigured in a conventional manner by means of a beam forming network (BFN in English) placed before the amplification stage and a switching network placed after the amplification stage. This BFN makes it possible to adjust the phases and amplitudes of the signals from the elementary sources before amplification, and the sources contributing to each beam are selected by the switching network located between the amplification stage and the elementary sources. It is therefore a high level (amplified) switching, which selects the amplified signals which will actually be supplied to the radiating sources. Conversely, certain amplified signals will not be supplied to the radiating sources, resulting in a loss of effective efficiency of the assembly, since we will have amplified signals which will not contribute to the radiated fields. The invention overcomes this problem.

It is known from document EP-A-0 333 166 in the name of the Applicant an antenna with electronic reconfiguration in transmission having essentially the same configuration of the control electronics as the previous document, and in particular the high switching network. level (30) which selects the radiating sources contributing to the formation of the beams. The same problem occurs as in the previous document.

A document published in Patent Abstracts of Japan, vol.12, no.60, (E-584) (2907), February 23, 1988, describes a switching device for a network antenna, comprising two levels of switching in series between the elementary sources and a bank of phase shifters each having a fixed value of phase shift. The elementary sources are divided into k groups of n elements, and k switches are used to select a source from each group; then the k elementary sources selected by these k switches are connected by these k switches to the k inputs of a switching matrix (k) x (m) and through this switching matrix to a bank of m phase shifters, this bank of phase shifters being characterized by a fixed phase shift law for each phase shifter. The desired phase shift for each source is thus obtained by switching the source in two stages, to connect it to a phase shifter having the appropriate phase shift value. We imagine that the control electronics of these k switches and of the switching matrix will have to be quite complicated.

Space applications, which require an electronic deflection of the ray wave over a wide field of view, lead to angular deviations of several brush widths. Consequently, the possibility of precisely controlling the shape of the antenna diagram is essential.

• limitation en volume du satellite, liée à la nécessité pour une antenne de transmettre et de recevoir simultanément ;
• compatibilité d'un agencement mécanique aisé sur la plate-forme, et sur le lanceur avant et pendant le fonctionnement ;
• bon contrôle thermique ;
• multiplicité éventuelle des missions et des utilisateurs.

The configuration of these large antennas must also take into account several system aspects:

• volume limitation of the satellite, linked to the need for an antenna to transmit and receive simultaneously;
• compatibility of an easy mechanical arrangement on the platform, and on the launcher before and during operation;
• good thermal control;
• possible multiplicity of missions and users.

The invention aims to solve these various problems.

• au moins un diviseur de puissance (15) à une entrée et m sorties qui forment m voies (V1 a Vm) séparées ;
• et en outre sur chaque voie (Vi) :
  • . un dispositif de contrôle (16), et
  • . un commutateur (19) permettant de relier une entrée à l'une des f sorties dudit commutateur (19) ; f n'étant pas obligatoirement identique d'une voie (Vi) à l'autre ;
     cette électronique d'alimentation et de contrôle permettant la création des faisceaux avec accès indépendants et de solliciter une seule source élémentaire appartenant à une classe à chaque instant ; caractérise en ce que ledit commutateur (19) est un commutateur bas niveau.

To this end, it proposes an antenna with electronic scanning in emission comprising a reflector (10) focusing energy, a network (11) of elementary sources located in the focal zone of the reflector so as to carry out the synthesis of the electromagnetic field in this zone. focal, this antenna having a coverage area produced by several adjacent spots, these spots being defined by the tracing on the ground of corresponding beams, the coverage area being partially and simultaneously covered by one or more beams whose accesses are independent and using for that the same number m of active elementary sources (or groups of sources) each selected from among m classes of sources which are never solicited simultaneously in the same beam, so that at each instant an elementary source belonging to a class and a only be solicited, the switching of the sources ensuring the agility of the or s beams, said antenna includes supply and control electronics further comprising:

• at least one power divider (15) with one input and m outputs which form m separate channels (V1 to Vm);
• and in addition on each channel (Vi):
  • . a control device (16), and
  • . a switch (19) for connecting an input to one of the f outputs of said switch (19); f not necessarily being identical from one channel (Vi) to the other;
  this supply and control electronics allowing the creation of beams with independent access and soliciting a single elementary source belonging to a class at any time; characterized in that said switch (19) is a low level switch.

Compared to mechanical solutions, the invention has the advantage of not requiring movement of the source or the reflector. It makes it possible to use weak focal lengths (compact antenna), and to ensure several simultaneous links.

• La performance de l'antenne n'est pas liée directement à la dimension totale du réseau ;
• L'implantation n'est pas obligatoirement sur la face terre du satellite.

The advantages compared to a direct radiation network solution are as follows:

• The performance of the antenna is not directly linked to the total size of the network;
• The installation is not necessarily on the earth face of the satellite.

• la dimension hors tout de réseau est réduite ;
• l'efficacité antenne est améliorée.

Compared to a simple reflector imaging network solution, the proposed solution has the following advantages:

• the overall dimension of the network is reduced;
• antenna efficiency is improved.

Finally, if we compare the proposed solution to an imaging network solution with double reflector, the compactness of the antenna of the invention is clearly highlighted.

• la figure 1 illustre schématiquement l'antenne à balayage selon l'invention ;
• la figure 2 illustre l'arrangement en classe du réseau ;
• la figure 3 illustre une première réalisation d'un électronique d'alimentation et de commande de l'antenne selon l'invention ;
• la figure 4 illustre un étage de l'électronique telle que représentée à la figure 3 ;
• la figure 5 illustre une seconde réalisation d'une électronique d'alimentation et de commande de l'antenne selon l'invention.

The characteristics and advantages of the invention will become apparent from the description which follows, by way of nonlimiting example, with reference to the appended figures in which:

• Figure 1 schematically illustrates the scanning antenna according to the invention;
• Figure 2 illustrates the class arrangement of the network;
• Figure 3 illustrates a first embodiment of an electronic power supply and antenna control according to the invention;
• Figure 4 illustrates a stage of electronics as shown in Figure 3;
• FIG. 5 illustrates a second embodiment of an electronics supply and control of the antenna according to the invention.

The antenna of the invention, represented in FIG. 1, comprises an eccentric parabolic reflector 10 supplied by a planar network 11 of sources located in the vicinity of the focal point F of the reflector, the network 12 representing the network of virtual sources, corresponding to this network 11.

In the antenna according to the invention, one plays only on the phase of each elementary source; which allows the optimal synthesis of each elementary source to be carried out as if it were at focus F of the reflector.

Such an operation makes it possible to produce an antenna whose gain does not depend on the pointing direction, while keeping the reflector 10 and the network 11 of elementary sources.

When the specified coverage is achieved using several spots corresponding to beams emitted by the antenna, the antenna directivity performance is defined by the level of coverage of the spots. We can also give appropriate forms to the sources in the focal plane to improve the efficiency of the antenna.

Thus, the antenna of the invention is provided for a number Sp, of spots, a number m of radiating elements or sources (or group of sources) corresponding to each spot.

To achieve full coverage, Sp spots are used, each spot comprising m sources. Some sources only belong to a spot. The sources are grouped into classes so that at a given time only one source of a class is used.

By forcing the spots to use the same number of active sources and by limiting the control of the sources, for example to a phase control (all the sources having the same weight in amplitude), one obtains limited performances of the antenna. On the other hand, the architecture of the subsystem is simplified.

The originality of the invention therefore lies in the arrangement of elementary sources in class. A class consisting of a set of sources which are not used simultaneously for the formation of the different beams. This observation therefore makes it possible to group these classes and to choose by switching one source per class; these sources associated with each other by the input divider will form the chosen beam.

By considering the matrix making the Sp spots correspond to the n sources, by the relation of the m active sources for a given spot, it is possible to identify classes of sources operating not simultaneously. An adequate definition of the spots makes it possible to obtain a configuration according to which the m active sources correspond to m classes of sources operating in a non-simultaneous manner, and this for all the spots.

Thus the coverage area produced by several adjacent spots is partially and simultaneously covered by one or more beams, the accesses of which are independent and using the same number m of elementary sources (of the group of sources) each selected from among m source classes never being solicited simultaneously in the same beam, so that at each instant an elementary source belonging to a class and only one is solicited , switching sources ensuring the agility of the beam (s).

An example of class organization for a network of 64 radiating elements or sources corresponding to 8 classes with 8 sources is given in Figure 2: each class being represented by a different number ranging from 1 to 8.

• un diviseur de puissance 15 à une entrée E et m sorties qui forment m voies V1 à Vm séparées ;
• et sur chaque voie (Vi) (qui correspond à une classe) :
  • . un dispositif de contrôle 16 comprenant un déphaseur réglable 17 ;
  • . un commutateur, ou "switch", bas niveau 19 permettant de relier une entrée à une des f sorties ;
  • . un étage d'amplification 20 à f entrées et f sorties comprenant un premier et un second coupleurs généralisés 21 et 22 disposés de part et d'autre de f amplificateurs 23 disposés en parallèle ;
  • . f filtres 24 disposés en parallèle entre les f sorties de l'étage d'amplification 20 et f sources Si1 à Sif du réseau ; f n'étant pas obligatoirement identique d'une voie à l'autre ;

   Le diviseur de puissance 15 est constitué d'un ensemble de coupleurs hybrides 25 qui sont combinés entre eux pour former m sorties.An embodiment of electronic supply and control of such an antenna according to the invention, as shown in FIG. 3, comprises:

• a power divider 15 with an input E and m outputs which form m separate channels V1 to Vm;
• and on each channel (Vi) (which corresponds to a class):
  • . a control device 16 comprising an adjustable phase shifter 17;
  • . a switch, or "switch", low level 19 making it possible to connect an input to one of the f outputs;
  • . an amplification stage 20 with f inputs and f outputs comprising a first and a second generalized couplers 21 and 22 arranged on either side of f amplifiers 23 arranged in parallel;
  • . f filters 24 arranged in parallel between the f outputs of the amplification stage 20 and f sources Si1 to Sif of the network; f not necessarily being identical from one channel to another;

The power divider 15 consists of a set of hybrid couplers 25 which are combined together to form m outputs.

An amplification stage 20 comprises a first and a second generalized couplers 21 and 22 respectively formed from a combination of hybrid couplers 25 on either side of amplifiers 23 so that each input of the first coupler 21 is distributed over all the amplifiers 23 and therefore on all the outputs of the hybrid couplers of the first generalized coupler 21.

In this amplification stage 20 a signal applied to the first input, for example, spring amplified on the first output. So if a signal is applied to one of the inputs of a floor (of rank i by example), at the corresponding output (of rank i) the signal will be amplified by all the amplifiers and no other output will receive a signal.

A detailed diagram of the amplification stage is shown in Figure 4.

The power amplifiers 23 receive on their respective inputs a signal coming from each beam, at an almost identical level. An almost uniform charge distribution is obtained over all the inputs of the amplifiers 23. The signals are then reconstituted using the second generalized coupler 22 which has a structure opposite to that of the first.

The amplifiers 23 thus have a constant input power and can thus operate at their nominal capacity.

Thus in the supply and control electronics, as represented in FIG. 3, a switch (19), called "class switch", can address any source of a class, without the operation of the amplifiers is not affected. The same is true for all classes, and therefore for all amplifiers.

The phase shift circuits (17) are controlled by a control unit not shown in the figures.

The antenna supply and control electronics, as shown in FIG. 3, has only one input E, that is to say that it only works with a single user, but it can also work with p users, as shown in figure 5.

By way of example, the power and control electronics of FIGS. 3 and 5 are represented with 8 classes (m = 8), and 8 sources per class (f = 8); We thus define a network of 64 sources corresponding to 8 classes of 8 sources. The realization of a given beam is therefore obtained when 8 sources, respectively belonging to each of the 8 classes, are addressed with 8 phase values, to achieve after amplification a set of 8 spots. This gives simultaneous multi-spot operation and therefore optimum synthesis of the emitted beam.

Claims (5)

1. An electronic scanning transmit antenna comprising an energy-focusing reflector (10), and an array (11) of elementary sources situated in the focal zone of the reflector in such a manner as to perform electromagnetic field synthesis in said focal zone, the antenna possessing a coverage zone constituted by a plurality of adjacent spots, said spots being defined by the ground tracks of the corresponding beams, the coverage zone being covered partially and simultaneously by one or more beams having independent accesses, this being achieved by using the same number m of elementary sources (or groups of sources) each selected from m classes of sources which are never used simultaneously in the same beam such that at any one instant one, and only one, elementary source belonging to any class is in use, with the agility of the beam(s) being provided by source switching, said antenna including power supply and control electronics further comprising:
      at least one power divider (15) having one input and m outputs forming m separate paths (V1 to Vm); and
      each path (Vi) further comprising:
      a control device (16), and
      a switch (19) for connecting an input to a selected one of f outputs of said switch (19); f not necessarily being identical from one path (Vi) to another;
      said power supply and control electronics enabling beams to be created with independent accesses and with only one elementary source belonging to any one class being in use at each instant, the antenna being characterized in that the said switch (19) is a low level switch.
2. An antenna according to claim 1, characterized in that said power supply and control electronics further comprises on each path (Vi):
      an amplification stage (20) having f inputs and f outputs comprising first and second generalized couplers (21, 22) disposed on either side of f amplifiers (23), connected in parallel, in such a manner that a signal applied to one of the inputs (of order i) of a stage (20) is amplified by all of the amplifiers (23) in parallel and is present on the corresponding output (of order i) after amplification, and none of the other outputs receives any signal; and
      f filters (24) disposed in parallel between f outputs of the amplification stage (20) and f elementary sources (Si1 to Sif) of the array.
3. An antenna according to claim 2, characterized in that the power divider (15) comprises a set of hybrid couplers (25) combined with one another to form m outputs.
4. An antenna according to claim 2, characterized in that the control device (16) comprises an adjustable phase shifter (17).
5. An antenna according to claim 2, characterized in that the first and second generalized couplers (21 and 22) are respectively constituted by hybrid couplers (25) associated in such a manner that each input to the first coupler (21) is spread over all of the amplifiers (23) and thus over all of the hybrid coupler outputs of the first generalized coupler (21), with the structure of the second generalized coupler (22) being the inverse of the first.

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