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EP0651461B1 - Antenna with array of radiating elements - Google Patents

Antenna with array of radiating elements Download PDF

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Publication number
EP0651461B1
EP0651461B1 EP94402449A EP94402449A EP0651461B1 EP 0651461 B1 EP0651461 B1 EP 0651461B1 EP 94402449 A EP94402449 A EP 94402449A EP 94402449 A EP94402449 A EP 94402449A EP 0651461 B1 EP0651461 B1 EP 0651461B1
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EP
European Patent Office
Prior art keywords
antenna
radiating elements
antenna according
arrays
circuits
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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EP94402449A
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German (de)
French (fr)
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EP0651461A1 (en
Inventor
André Champeau
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Thales SA
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Thomson CSF SA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q21/00—Antenna arrays or systems
    • H01Q21/29—Combinations of different interacting antenna units for giving a desired directional characteristic
    • H01Q21/293—Combinations of different interacting antenna units for giving a desired directional characteristic one unit or more being an array of identical aerial elements
    • H01Q21/296—Multiplicative arrays
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q21/00—Antenna arrays or systems
    • H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
    • H01Q21/22—Antenna units of the array energised non-uniformly in amplitude or phase, e.g. tapered array or binomial array

Definitions

  • the present invention relates to beam formation at the reception in a network antenna.
  • a network antenna consists of an assembly of elements radiant distributed in a network, mostly surface, according to a mesh of approximately half ⁇ / 2 of the wavelength of the emitted radiation or received to avoid the appearance of lobes of the network disturbing the directivity of the antenna.
  • the dimensioning of an antenna depends on the amplitude of the signal to be received, i.e. the signal to noise ratio desired in reception and the desired angular resolution.
  • the signals to be received are characterized by a uniform power surface density instead of receiving so that the strength of the useful signal received grows as the useful surface of the antenna.
  • the angular resolution is, for its part, defined in each direction by the linear dimension L of the antenna in the direction considered relative to the wavelength ⁇ in the relation ⁇ / L, the solid angular resolution being defined in the ratio ⁇ 2 / S where S is the surface of the antenna.
  • the absence of certain radiating elements means that the mesh at approximately ⁇ / 2 is no longer respected which leads to the appearance of network lobes if the disposition missing radiating elements is periodic or diffuse lobes if this arrangement is random. It is important to minimize these network and diffuse lobes.
  • a network antenna can be mechanically pointing or electronic.
  • the score is electronic, it can be associated with a analog beamforming or beamforming by the calculation.
  • Analog beam formation requires equipping the radiating elements of individual phase shifting modules allowing to orient the plane of the waves transmitted or received in the desired direction. She has the advantage of working both on transmission and on reception.
  • attenuators or a distribution network allow amplitude weighting.
  • Beam formation by calculation consists in digitizing the signals received by each of the radiating elements after they have been demodulated in a coherent way and then to phase them individually and to make a weighted sum by calculator to orient the wave plane received in the desired direction. It has the advantage of giving great flexibility in beam formation since it is possible to form simultaneously by calculating several beams pointing in directions different. It also allows for anti-jamming by adjustment the position of the zeros in the radiation diagram. However, she has the disadvantage of not being usable on the show, of requiring a expensive equipment for digitizing element signals radiant and claim a very large amount of calculations.
  • an antenna network is often used for both transmitting and receiving it is usual to equip the radiating elements with an antenna array of modules individual phase shifters allowing pointing by beam formation analog and group the radiating elements of the antenna into subnets to carry out anti-jamming on reception by training reduced beam by calculation, grouping of radiating elements taking place in surface sub-networks and beam formation by the calculation performed in the two pointing directions, deposit and site.
  • the reduced beam formation by calculation generates a radiation pattern whose main lobe retains the direction of pointing produced by the phase shift modules but whose zeros are moved in the direction of the jammers, this by playing second order on the relative phase shifts imposed on the reception signals of the sub-networks.
  • This radiation diagram keeps the disadvantage of having network lobes at angular positions discrete or diffuse lobes depending on whether the organization of the subnets areal in the network is periodic or random because the subnetworks necessarily have phase centers spaced a distance apart greater than or equal to ⁇ reflecting a subsampling of the surface of the network.
  • the object of the present invention is to form a beam for an array antenna with a low level of side lobes or lobes diffuse, whether this network antenna is full, incomplete or rarefied and provided or not of a reduced beam formation by calculation.
  • Its object is an antenna with a network of radiating elements which has its radiating elements grouped in reception, in two sets of parallel linear sub-networks oriented in two different directions, and which comprises two beam forming circuits each receiving the signals from one of the sets of subnets and each delivering a reduced beamforming signal, and an output circuit providing a reception signal from a non-linear combination of the two signals generated by the two beam forming circuits.
  • the directions of the two sets of subnets linear are orthogonal and oriented one according to the site plan and the other according to the network antenna field plan.
  • the output circuit does not combine linear the two signals generated by the two formation circuits of beam by performing for example either their product or their convolution.
  • Figure 1 illustrates a prior art array antenna with a planar network of 48 radiating elements distributed in a mesh of approximately ⁇ / 2, individually equipped with phase shift modules and shown under shape of contiguous blocks 1.
  • Each phase shift module allows to adjust individually the phase of each radiating element to obtain the emission or the reception a wave plane directed at the same time in deposit and in site.
  • the 48 radiant elements and their modules phase shifters 1 are grouped in parallel in groups of four into twelve Areal subnets 2 whose contours are shown in lines supported.
  • the reception signals of the twelve surface subnets 2 are then directed to a beam forming circuit 3 by calculation which performs reduced beam formation for anti-jamming, that is to say to obtain a reception radiation diagram with a main lobe in the pointing direction imposed by the modules phase shifters and zeros in the directions of the jammers. Bearing on twelve receive source signals this reduced beam formation allows to place zeros of the radiation diagram in eleven different directions and therefore eliminate eleven jamming directions. However, its performance is severely limited by the existence of large lobes or diffuse lobes due to equal spacing or greater than ⁇ between the phase centers of the surface sub-networks.
  • the radiating elements are distributed on reception a network antenna and their possible individual phase shift modules in two sets of parallel linear sub-networks oriented in two separate directions, we proceed to a reduced beam formation on each of two sets of parallel linear subnets and one combines the two signals obtained non-linearly by multiplication or convolution after a possible thresholding.
  • FIG. 2 represents a directive network antenna which can be electronically orientated on site and in a field implementing this solution.
  • This network antenna is composed of m ⁇ n radiating elements 4 associated with individual phase-shifting modules 5 and arranged in rows and columns according to a planar network with a mesh of approximately ⁇ / 2 to meet the surface sampling criterion guaranteeing the absence of network lobes in the case of an electronic scan over a wide angle.
  • Each radiating element with its phase shift module participates to the two sets of linear subnetworks by dividing its signal from output in two identical components in amplitude and in phase.
  • FIG. 3 separately represents the two nested sets of linear sub-networks 6, 7 to facilitate the explanation.
  • the antenna is pointed electronically at reception, and at transmission in the case of a radar, by means of phase shift modules.
  • all of the n horizontal linear sub-networks 6 supply n signals to a first beam forming circuit 8 which performs a reduced n- order beam formation in elevation while all of the m sub-networks vertical lines 7 provides m signals to a second beam forming circuit 9 which performs reduced beam formation of order m in bearing.
  • the reduced formation of beam in elevation gives a radiation pattern without grating lobes or diffuse lobes in the direction of the deposit since it takes place on the signals of solid horizontal linear sub-grids and with grating lobes or diffuse lobes in direction of the site compensated by the possibility of an adjustment of n -1 zeros in site.
  • the reduced formation of beam in bearing gives a radiation diagram without lobes of lattice or diffuse lobes in direction of the site since it is carried out on the signals of the vertical linear sub-networks full and with lobes of lattice or diffuse lobes in direction of the deposit offset by the possibility of adjusting m -1 zeros in the deposit.
  • the two beam forming circuits 8 and 9 can operate reduced beam formations by calculation and be produced by means of a computer.
  • the n + m output signals of the n + m horizontal and vertical linear sub-networks 6 and 7 are then demodulated in coherence and digitized before being applied to it.
  • the computer can perform the reduced beam formation in elevation and in bearing alternately, the order of formation in elevation then in bearing or vice versa having no influence.
  • the signals delivered by the two training circuits of bundle 8 and 9 are then applied to a combination circuit 10 which performs the product or convolution and issues a single output signal antenna.
  • the single antenna output signal appears, when it has origin a single transmitting source picked up by the antenna, as the signal of reception of an antenna which would have, for radiation diagram, the produces two radiation patterns of reduced formations of beam in site and in deposit; radiation pattern which is lacking network lobes and diffuse lobes due to subsampling because one of the component diagrams does not have a lobe or lobe diffuse in the site map and the other component diagram has no lobes of network or diffuse lobe in the deposit plan.
  • Figures 4a and 4b show, plotted in a trihedron of reference whose OX axis is graduated in bearing angle, OY axis in angle of the site and the OZ axis in signal level, the cross-sections in the XOZ planes and YOZ of the surfaces of the radiation patterns obtained at the output of two reduced beam formation circuits 9 and 8.
  • FIG. 4a represents the radiation diagram obtained at the output of the beam forming circuit 9 operating on the signals of the m vertical linear sub-networks 7. It comprises a fine main lobe oriented in the pointing direction imposed by the settings of the phase shift modules individual surrounded by side lobes of small amplitudes in the YOZ site plane because the sub-networks at the base of the reduced beam formation are full vertical linear sub-networks, and of more marked amplitudes in the XOZ field plane but with spacer zeros whose positions are adjustable by the adaptive action of reduced beamforming.
  • FIG. 4b represents the radiation diagram obtained in output of the beam forming circuit 8 operating on the signals of n Horizontal linear sub-networks 6. Like the previous one, it has a fine main lobe oriented in the direction of pointing imposed by the individual phase shift module settings. But this one is surrounded by small amplitude side lobes in the XOZ plane, because the subnets at the base of reduced beam formation are subnets full horizontal lines, and of more marked amplitudes in the YOZ site map but with insert zeros whose positions are adjustable by the adaptive action of reduced beam formation.
  • the adaptive actions of the two reduced beam formations one independently in the site plan, the other in the plan deposit by creating zeros in the form of valleys recalled in the figures 4a, 4b by dotted lines, each valley consuming only one degree of freedom on only one of the two reduced beam formations.
  • the product of the two diagrams presents two sets of adjustable zeros angularly one in the site plan, the other in the deposit plan which shows the advantage of performing between the signals of the two training circuits reduced beam a nonlinear combination such as a product or a convolution.
  • it is interesting to subject the thresholds to signals from the two reduced beam forming circuits to prevent a parasitic signal received by one of the two formations reduced beam is only validated by thermal noise from the other reduced beam formation. There is then no incompatibility so that the threshold chosen is not that of limiting false alarms by noise in a detection process.
  • FIG. 5 illustrates the network antenna diagram to which we end up.
  • This comprises a network of radiating elements arranged in rows and columns in a mesh of approximately ⁇ / 2 and equipped with individual phase-shifting modules.
  • the radiating elements are shown without their phase shift modules and the network is shown split in 12 and 12 '.
  • At 12 appears the first grouping in reception of the radiating elements in m vertical linear sub-networks 13 delivering m signals to a first reduced beam forming circuit 14 operating in the plane of the deposit.
  • Two threshold circuits 17, 18 placed at the output of the two beam forming circuits 14, 16 provide a basing of their signals before the latter are applied to a nonlinear combination circuit 19 which produces the product or the convolution thereof.
  • the product operation can be a simple multiplication, a addition of signals which we have taken the logarithm or a logical operation of type "and" controlled by signals made previously bivalent.
  • Multiplication improves angular resolution because, at width of identical main lobe, the attenuation in dB is double that of each of the two sets of subnets considered in isolation, but this at the price of a 6 dB loss in signal to noise ratio.
  • the two signals delivered by the two training circuits of beam being of identical amplitudes, we are in optimal conditions of a multiplication operation.
  • the convolution operation allows to mitigate even more strongly the interfering signals received in one of the reduced formations of beam and not in the other, by absence of correlation with the signal emitted by the radar, or between them.
  • the spacing between the linear sub-networks of each set grows, in geometric progression, from one edge to the other of the antenna, but other spacings without harmonic periodicity are possible.
  • the radiating elements located at the crossing points of the vertical and horizontal linear subnets participate in both assemblies and are fitted with individual output phase shift modules double delivering identical signals in amplitude and phase.
  • the other radiating elements have individual phase shift modules with output simple. Whether coming from single or double output modules, the signals are of the same magnitude and have relative phases which are those of the law pointing the antenna.
  • the outputs of the vertical linear sub-networks 20 of the first together are connected to the inputs of a first training circuit 22 beam in the reservoir plane while the outputs of the subnetworks horizontal lines 21 of the second set are connected to inputs of a second beam-forming circuit 23 in the site plan.
  • the two outputs of the two beam forming circuits 22, 23 are, as in the case of FIG. 5, connected via two threshold circuits at the two inputs of a combination circuit no linear performing a product or a convolution to generate the signal of antenna output.
  • the antenna is pointed electronically by the modules individual phase shifters, on reception and also on transmission in the case of a radar.
  • the first circuit 22 of reduced beam formation delivers, at the reception, a signal corresponding to that of an antenna having a radiation pattern with weak lobes in the site plane secondary defined by the weighting law applied analogically.
  • Figure 7a gives an example of such a diagram with diffuse lobes.
  • the second circuit 23 of reduced beam formation delivers, at reception, a signal corresponding to that of an antenna having a radiation pattern with weak lobes in the deposit plane secondary defined by the law of weighting applied analogously to each horizontal linear sub-network 21 and, in the site plane, lobes of diffuse network or lobes depending on whether the scarcity of all the sub-networks full horizontal linear 21 is distributed periodically or randomly.
  • Figure 7b gives an example of such a diagram with diffuse lobes.
  • the two formations beam reductions obtained can be fixed or adaptive and, in the latter case, allowing the positioning of zeros, separately in site and deposit as illustrated previously in Figures 4a and 4b.
  • the thresholding of the two signals resulting from the two reduced beam formations separated in the site and deposit planes and their non-linear combination by product or convolution makes it possible to obtain a reception signal having properties similar to that of a beam-forming antenna total with only two reduced orthogonal beam formations of cumulative moments n + m .
  • the number of degrees of freedom in other words, the number of adaptive zeros achievable is of course only ( m -1) + ( n -1) but the lattices or diffuse lobes have been eliminated by the product operation or convolution subject only to the fact that the secondary lobes orthogonal to these lattices or diffuse lobes have themselves been eliminated by the thresholding operation on the two channels, hence the advantage of adaptive thresholds taking into account the level disturbing signals, such as clutter residue. Interference-type disturbers will be treated in the first degree by zeros in the two reduced adaptive beam formations, but possible residues will receive additional treatment by the combination of thresholding and product or convolution operations.
  • the proposed network antenna architecture avoids the limitations of the prior art by an organization of its radiating elements based on a juxtaposition side by side in parallel, of m linear sub-networks of n elements contiguous to each other and whose centers of phase are spaced according to sampling criteria of the antenna surface which avoid the creation of high lobe or diffuse lobes. Limited to this organization, the antenna could only be provided with beam formation in the plane perpendicular to the sub-arrays. To avoid this, the radiating elements of the antenna are reused to form a second juxtaposition side by side in parallel with n sub-arrays of m elements orthogonal to the first sub-arrays and completely nested in them.
  • two beam formations are produced at m and n moments in two orthogonal planes whose signals are combined non-linearly by product or convolution to obtain a reception signal similar to that of '' a network antenna forming a two-plane network at n ⁇ m moments.
  • the proposed antenna architecture presents two ways of reception from the two reduced beam formations on which it may be advantageous to carry out, before the product or convolution, certain treatments such as Doppler filtering of fixed echoes in the case of a radar, which are then split.
  • the cost of this duplication is however much less than that of a total formation of beam in two planes and is fully justified by performance obtained in comparison with those of a reduced beam formation two plans of the prior art.
  • Figure 8 gives an example of an antenna rarefied non-periodic network with reduced beam formations putting in the proposed architecture.
  • the radiating elements are fitted with phase shift modules individual.
  • the element-to-element spacing in subnets is 0.55 ⁇ .
  • the spacing between their sub-networks is variable and grows from one edge to the other of the antenna by example in geometric progression.
  • the antenna obtained is part of a 49.5 ⁇ by 41.8 ⁇ surface giving a directivity of about 3 dB 1.45 degrees by 1.7 degrees.
  • the full antenna equivalent in this aspect would include 6,840 radiating elements and individual phase shift modules whereas this one comprises only 1835. The coefficient of rarefaction is therefore 3.73.
  • the output signals of the eleven linear subnetworks horizontal 30 of the first set are scanned before being applied to a first beam forming circuit by calculation 32 which performs reduced adaptive beam formation in the vertical or planar plane eleven-point site, allowing ten directions anti-jamming different on site.
  • the output signals of the thirteen vertical linear sub-networks 31 of the second set are digitized before being applied to a second beamforming circuit by calculation 33 which performs a reduced adaptive beamforming in the horizontal or planar plane deposit at thirteen points, thus allowing the jamming of twelve different directions in deposit.
  • the two signals delivered by the two training circuits of beam by calculation 32, 33 or rather, their modules are applied to two threshold circuits 34, 35.
  • the signals delivered by the two threshold circuits 34 and 35 are then applied to the inputs of a type 36 logic circuit performing their produces and delivers the antenna reception signal.

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  • Variable-Direction Aerials And Aerial Arrays (AREA)
  • Aerials With Secondary Devices (AREA)

Description

La présente invention concerne la formation de faisceau à la réception dans une antenne réseau.The present invention relates to beam formation at the reception in a network antenna.

Une antenne réseau est constituée d'un assemblage d'éléments rayonnants répartis en un réseau, la plupart du temps surfacique, selon un maillage d'environ la moitié λ/2 de la longueur d'onde du rayonnement émis ou reçu pour éviter l'apparition de lobes du réseau perturbant la directivité de l'antenne.A network antenna consists of an assembly of elements radiant distributed in a network, mostly surface, according to a mesh of approximately half λ / 2 of the wavelength of the emitted radiation or received to avoid the appearance of lobes of the network disturbing the directivity of the antenna.

Le dimensionnement d'une antenne est fonction de l'amplitude du signal à recevoir c'est-à-dire du rapport signal à bruit désiré en réception et de la résolution angulaire souhaitée.The dimensioning of an antenna depends on the amplitude of the signal to be received, i.e. the signal to noise ratio desired in reception and the desired angular resolution.

Dans la plupart des cas, les signaux à recevoir sont caractérisés par une densité surfacique de puissance uniforme au lieu de réception de sorte que la puissance du signal utile reçu croít comme la surface utile de l'antenne.In most cases, the signals to be received are characterized by a uniform power surface density instead of receiving so that the strength of the useful signal received grows as the useful surface of the antenna.

La résolution angulaire est, quant à elle, définie dans chaque direction par la dimension linéaire L de l'antenne dans la direction considérée rapportée à la longueur d'onde λ dans la relation λ/L, la résolution angulaire solide étant définie dans le rapport λ2/S où S est la surface de l'antenne.The angular resolution is, for its part, defined in each direction by the linear dimension L of the antenna in the direction considered relative to the wavelength λ in the relation λ / L, the solid angular resolution being defined in the ratio λ 2 / S where S is the surface of the antenna.

Dans la pratique, une fine résolution angulaire et un rapport signal/bruit élevé sont tous deux souhaitables ce qui conduit, si aucun compromis n'est accepté, à des éléments rayonnants en surnombre. Comme l'on cherche, pour des raisons de coût, à limiter le plus possible le nombre d'éléments rayonnants d'une antenne réseau, il est intéressant de lutter contre ce surnombre en laissant des vides dans le maillage des éléments rayonnants à la surface d'une antenne réseau. L'antenne réseau est alors dite lacunaire ou raréfiée selon que le nombre d'éléments rayonnants manquants est inférieur ou supérieur au nombre d'éléments rayonnants présents.In practice, a fine angular resolution and a ratio high signal / noise are both desirable which leads, if none compromise is not accepted, to excess radiating elements. As we try, for cost reasons, to limit as much as possible the number radiating elements of a network antenna, it is interesting to fight against this excess by leaving gaps in the mesh of elements radiant on the surface of a network antenna. The network antenna is then said to be incomplete or rarefied according to whether the number of radiating elements missing is less than or greater than the number of radiating elements present.

Dans une antenne réseau lacunaire ou raréfiée, l'absence de certains éléments rayonnants fait que le maillage à environ λ/2 n'est plus respecté ce qui conduit à l'apparition de lobes de réseau si la disposition des éléments rayonnants manquants est périodique ou de lobes diffus si cette disposition est aléatoire. Il importe de réduire le plus possible ces lobes de réseau et diffus.In a patchy or scarce network antenna, the absence of certain radiating elements means that the mesh at approximately λ / 2 is no longer respected which leads to the appearance of network lobes if the disposition missing radiating elements is periodic or diffuse lobes if this arrangement is random. It is important to minimize these network and diffuse lobes.

Une antenne réseau peut être à pointage mécanique ou électronique. Lorsque le pointage est électronique, il peut être associé à une formation de faisceau analogique ou à une formation de faisceau par le calcul.A network antenna can be mechanically pointing or electronic. When the score is electronic, it can be associated with a analog beamforming or beamforming by the calculation.

La formation de faisceau analogique nécessite d'équiper les éléments rayonnants de modules individuels déphaseurs permettant d'orienter le plan des ondes émises ou reçues dans la direction voulue. Elle a l'avantage de fonctionner aussi bien à l'émission qu'à la réception. Eventuellement, des atténuateurs ou un réseau de distribution permettent une pondération en amplitude.Analog beam formation requires equipping the radiating elements of individual phase shifting modules allowing to orient the plane of the waves transmitted or received in the desired direction. She has the advantage of working both on transmission and on reception. Optionally, attenuators or a distribution network allow amplitude weighting.

La formation de faisceau par le calcul consiste à numériser les signaux reçus par chacun des éléments rayonnants après qu'ils aient été démodulés de façon cohérente puis à les déphaser individuellement et à en faire une somme pondérée par calculateur pour orienter le plan des ondes reçues dans la direction voulue. Elle a l'avantage de donner une grande souplesse à la formation de faisceau puisqu'il est possible de former simultanément par le calcul plusieurs faisceaux pointant dans des directions différentes. Elle permet en outre de faire de l'antibrouillage par ajustement de la position des zéros dans le diagramme rayonnement. Cependant, elle a le désavantage de ne pas être utilisable à l'émission, de nécessiter un équipement coûteux pour la numérisation des signaux des éléments rayonnants et de réclamer une quantité de calculs très importante.Beam formation by calculation consists in digitizing the signals received by each of the radiating elements after they have been demodulated in a coherent way and then to phase them individually and to make a weighted sum by calculator to orient the wave plane received in the desired direction. It has the advantage of giving great flexibility in beam formation since it is possible to form simultaneously by calculating several beams pointing in directions different. It also allows for anti-jamming by adjustment the position of the zeros in the radiation diagram. However, she has the disadvantage of not being usable on the show, of requiring a expensive equipment for digitizing element signals radiant and claim a very large amount of calculations.

Pour limiter le coût d'une formation de faisceau par le calcul on a pensé diviser le réseau de l'antenne en sous-réseaux et la réaliser sous forme réduite non pas sur les signaux individuels des éléments rayonnants mais sur les signaux délivrés individuellement par les sous-réseaux. Le maillage de l'antenne à environ λ/2 n'est plus respecté ce qui conduit à l'apparition de lobes de réseau et/ou de lobes diffus de sorte que la formation réduite de faisceau conduit à des performances médiocres de l'antenne sur un large champ angulaire. Elle reste cependant intéressante pour l'antibrouillage angulaire ponctuel car celui-ci ne nécessite pas, pour être efficace, que la formation de faisceau porte sur un grand nombre de signaux d'éléments rayonnants. To limit the cost of beam formation by calculation, we have thought of dividing the antenna network into sub-networks and carrying it out reduced form not on the individual signals of the radiating elements but on the signals delivered individually by the sub-networks. The mesh size of the antenna at around λ / 2 is no longer respected, which leads to the appearance of network lobes and / or diffuse lobes so that the reduced beam formation leads to poor performance of the antenna over a wide angular field. However, it remains interesting for the point angular jamming because it does not require, for to be effective, that beamforming involves a large number of radiating element signals.

Compte tenu de ces considérations et du fait qu'une antenne réseau est souvent employée à la fois à l'émission et à la réception, il est usuel d'équiper les éléments rayonnants d'une antenne réseau de modules déphaseurs individuels permettant un pointage par formation de faisceau analogique et de regrouper les éléments rayonnants de l'antenne en sous-réseaux pour effectuer un antibrouillage à la réception par une formation réduite de faisceau par le calcul, le regroupement des éléments rayonnants s'effectuant en sous-réseaux surfaciques et la formation de faisceau par le calcul s'effectuant dans les deux directions de pointage, gisement et site.Given these considerations and the fact that an antenna network is often used for both transmitting and receiving it is usual to equip the radiating elements with an antenna array of modules individual phase shifters allowing pointing by beam formation analog and group the radiating elements of the antenna into subnets to carry out anti-jamming on reception by training reduced beam by calculation, grouping of radiating elements taking place in surface sub-networks and beam formation by the calculation performed in the two pointing directions, deposit and site.

La formation réduite de faisceau par le calcul engendre un diagramme de rayonnement dont le lobe principal conserve la direction de pointage produite par les modules déphaseurs mais dont les zéros sont déplacés en direction des brouilleurs, cela en jouant au second ordre sur les déphasages relatifs imposés aux signaux de réception des sous-réseaux. L'énergie totale étant conservée, ce diagramme de rayonnement garde l'inconvénient de présenter des lobes de réseau à des positions angulaires discrètes ou des lobes diffus selon que l'organisation des sous-réseaux surfaciques dans le réseau est périodique ou aléatoire car les sous-réseaux ont nécessairement des centres de phase espacés d'une distance supérieure ou égale à λ traduisant un sous-échantillonnage de la surface du réseau.The reduced beam formation by calculation generates a radiation pattern whose main lobe retains the direction of pointing produced by the phase shift modules but whose zeros are moved in the direction of the jammers, this by playing second order on the relative phase shifts imposed on the reception signals of the sub-networks. The total energy being conserved, this radiation diagram keeps the disadvantage of having network lobes at angular positions discrete or diffuse lobes depending on whether the organization of the subnets areal in the network is periodic or random because the subnetworks necessarily have phase centers spaced a distance apart greater than or equal to λ reflecting a subsampling of the surface of the network.

La présente invention a pour but une formation de faisceau pour une antenne réseau avec un bas niveau de lobes secondaires ou de lobes diffus, que cette antenne réseau soit pleine, lacunaire ou raréfiée et pourvue ou non d'une formation réduite de faisceau par le calcul.The object of the present invention is to form a beam for an array antenna with a low level of side lobes or lobes diffuse, whether this network antenna is full, incomplete or rarefied and provided or not of a reduced beam formation by calculation.

Elle a pour objet une antenne à réseau d'éléments rayonnants qui a ses éléments rayonnants regroupés en réception, en deux ensembles de sous-réseaux linéaires parallèles orientés selon deux directions différentes, et qui comporte deux circuits de formation de faisceau recevant chacun les signaux de l'un des ensembles de sous-réseaux et délivrant chacun un signal de formation réduite de faisceau, et un circuit de sortie délivrant un signal de réception à partir d'une combinaison non linéaire des deux signaux engendrés par les deux circuits de formation de faisceau. Its object is an antenna with a network of radiating elements which has its radiating elements grouped in reception, in two sets of parallel linear sub-networks oriented in two different directions, and which comprises two beam forming circuits each receiving the signals from one of the sets of subnets and each delivering a reduced beamforming signal, and an output circuit providing a reception signal from a non-linear combination of the two signals generated by the two beam forming circuits.

Avantageusement, les directions des deux ensembles de sous-réseaux linéaires sont orthogonales et orientées l'une selon le plan site et l'autre selon le plan gisement de l'antenne réseau.Advantageously, the directions of the two sets of subnets linear are orthogonal and oriented one according to the site plan and the other according to the network antenna field plan.

Avantageusement, le circuit de sortie combine de façon non linéaire les deux signaux engendrés par les deux circuits de formation de faisceau en effectuant par exemple soit leur produit soit leur convolution.Advantageously, the output circuit does not combine linear the two signals generated by the two formation circuits of beam by performing for example either their product or their convolution.

D'autres caractéristiques et avantages de l'invention ressortiront de la description ci-après d'un mode de réalisation donné à titre d'exemple. Cette description sera faite en regard du dessin dans lequel :

  • une figure 1 représente une antenne réseau avec formation réduite de faisceau selon l'art antérieur,
  • une figure 2 représente une antenne réseau selon l'invention avec ses éléments rayonnants organisés en réception en deux sous-ensembles de sous-réseaux linéaires,
  • une figure 3 représente cette même antenne réseau, dans laquelle on a désimbriqué les deux sous-réseaux pour la clarté de l'opposé,
  • des figures 4a et 4b représentent des diagrammes de rayonnement obtenus avec des circuits de formation de faisceau utilisés dans l'antenne réseau de la figure 3,
  • une figure 5 représente l'architecture d'antenne réseau selon l'invention, à laquelle ont été apportées des fonctions de seuil,
  • une figure 6 illustre une répartition possible des éléments rayonnants dans une antenne réseau raréfiée conforme à l'invention, répartition qui s'effectue selon deux ensembles de sous-réseaux linéaires alimentant chacun un circuit de formation de faisceau,
  • des figures 7a et 7b représentent des diagrammes de rayonnement obtenus avec les circuits de formation de faisceau de l'antenne de la figure 6, et
  • une figure 8 représente une architecture d'antenne réseau raréfiée selon l'invention.
Other characteristics and advantages of the invention will emerge from the description below of an embodiment given by way of example. This description will be made with reference to the drawing in which:
  • FIG. 1 represents a network antenna with reduced beam formation according to the prior art,
  • FIG. 2 represents a network antenna according to the invention with its radiating elements organized in reception in two subsets of linear sub-networks,
  • FIG. 3 represents this same network antenna, in which the two sub-networks have been nested for the clarity of the opposite,
  • FIGS. 4a and 4b represent radiation diagrams obtained with beam forming circuits used in the array antenna of FIG. 3,
  • FIG. 5 represents the architecture of the network antenna according to the invention, to which threshold functions have been added,
  • FIG. 6 illustrates a possible distribution of the radiating elements in a rarefied network antenna according to the invention, distribution which is carried out according to two sets of linear sub-networks each supplying a beam forming circuit,
  • FIGS. 7a and 7b represent radiation patterns obtained with the beam forming circuits of the antenna of FIG. 6, and
  • FIG. 8 represents a rarefied network antenna architecture according to the invention.

La figure 1 illustre une antenne réseau de l'art antérieur avec un réseau plan de 48 éléments rayonnants répartis selon un maillage d'environ λ/2, équipés individuellement de modules déphaseurs et représentés sous forme de pavés contigus 1. Chaque module déphaseur permet d'ajuster individuellement la phase de chaque élément rayonnant pour obtenir à l'émission ou à la réception un plan d'onde orienté à la fois en gisement et en site. A la réception les 48 éléments rayonnants et leurs modules déphaseurs 1 sont regroupés en parallèle par groupes de quatre en douze sous-réseaux surfaciques 2 dont les contours sont représentés en traits appuyés. Les signaux de réception des douze sous-réseaux surfaciques 2 sont ensuite dirigés vers un circuit 3 de formation de faisceau par le calcul qui effectue une formation réduite de faisceau pour de l'antibrouillage c'est-à-dire pour obtenir un diagramme de rayonnement en réception avec un lobe principal dans la direction de pointage imposée par les modules déphaseurs et des zéros dans les directions des brouilleurs. Portant sur douze signaux de sources de réception, cette formation réduite de faisceau permet de placer des zéros du diagramme de rayonnement dans onze directions différentes et donc d'éliminer onze directions de brouillage. Cependant, ses performances sont sévèrement limitées par l'existence de lobes de réseau ou de lobes diffus élevés due à l'espacement égal ou supérieur à λ entre les centres de phase des sous-réseaux surfaciques.Figure 1 illustrates a prior art array antenna with a planar network of 48 radiating elements distributed in a mesh of approximately λ / 2, individually equipped with phase shift modules and shown under shape of contiguous blocks 1. Each phase shift module allows to adjust individually the phase of each radiating element to obtain the emission or the reception a wave plane directed at the same time in deposit and in site. Upon receipt, the 48 radiant elements and their modules phase shifters 1 are grouped in parallel in groups of four into twelve Areal subnets 2 whose contours are shown in lines supported. The reception signals of the twelve surface subnets 2 are then directed to a beam forming circuit 3 by calculation which performs reduced beam formation for anti-jamming, that is to say to obtain a reception radiation diagram with a main lobe in the pointing direction imposed by the modules phase shifters and zeros in the directions of the jammers. Bearing on twelve receive source signals this reduced beam formation allows to place zeros of the radiation diagram in eleven different directions and therefore eliminate eleven jamming directions. However, its performance is severely limited by the existence of large lobes or diffuse lobes due to equal spacing or greater than λ between the phase centers of the surface sub-networks.

On propose de réduire les inconvénients des lobes de réseau ou lobes diffus dus aux regroupements des éléments rayonnants en sous-réseaux tels qu'ils se font actuellement ou à la lacunarité ou la raréfaction d'une antenne réseau.It is proposed to reduce the drawbacks of network lobes or diffuse lobes due to grouping of radiating elements in sub-arrays as they are currently done or with lacunarity or scarcity a network antenna.

Pour ce faire, on répartit en réception les éléments rayonnants d'une antenne réseau et leurs éventuels modules déphaseurs individuels en deux ensembles de sous-réseaux linéaires parallèles orientés selon deux directions distinctes, on procède à une formation réduite de faisceau sur chacun de deux ensembles de sous-réseaux linéaires parallèles et on combine les deux signaux obtenus de façon non linéaire par multiplication ou convolution après un éventuel seuillage.To do this, the radiating elements are distributed on reception a network antenna and their possible individual phase shift modules in two sets of parallel linear sub-networks oriented in two separate directions, we proceed to a reduced beam formation on each of two sets of parallel linear subnets and one combines the two signals obtained non-linearly by multiplication or convolution after a possible thresholding.

La figure 2 représente une antenne réseau directive orientable électroniquement en site et en gisement mettant en oeuvre cette solution. Cette antenne réseau est composée de m×n éléments rayonnants 4 associés à des modules déphaseurs individuels 5 et disposés en lignes et colonnes selon un réseau plan avec un maillage d'environ λ/2 pour répondre au critère d'échantillonnage de surface garantissant l'absence de lobes de réseau dans le cas d'un balayage électronique sur un grand angle. FIG. 2 represents a directive network antenna which can be electronically orientated on site and in a field implementing this solution. This network antenna is composed of m × n radiating elements 4 associated with individual phase-shifting modules 5 and arranged in rows and columns according to a planar network with a mesh of approximately λ / 2 to meet the surface sampling criterion guaranteeing the absence of network lobes in the case of an electronic scan over a wide angle.

Cette antenne est organisée à la réception en deux ensembles de sous-réseaux linéaires orthogonaux imbriqués :

  • un premier ensemble formé d'une superposition de n sous-réseaux linéaires horizontaux 6 constitués chacun de m éléments rayonnants 4 et de leurs modules déphaseurs 5,
  • un deuxième ensemble formé d'une juxtaposition horizontale de m sous-réseaux linéaires verticaux 7 constitués chacun de n éléments rayonnants 4 et de leurs modules déphaseurs 5.
This antenna is organized at reception into two sets of nested orthogonal linear sub-networks:
  • a first assembly formed by a superposition of n horizontal linear sub-networks 6 each consisting of m radiating elements 4 and their phase-shifting modules 5,
  • a second assembly formed by a horizontal juxtaposition of m vertical linear sub-networks 7 each consisting of n radiating elements 4 and their phase-shifting modules 5.

Chaque élément rayonnant avec son module déphaseur participe aux deux ensembles de sous-réseaux linéaires par division de son signal de sortie en deux composantes identiques en amplitude et en phase.Each radiating element with its phase shift module participates to the two sets of linear subnetworks by dividing its signal from output in two identical components in amplitude and in phase.

Pour la suite, on se réfère à la figure 3 qui représente séparément les deux ensembles imbriqués de sous-réseaux linéaires 6, 7 pour faciliter l'explication. L'antenne est pointée électroniquement à la réception, et à l'émission dans le cas d'un radar, par l'intermédiaire des modules déphaseurs. A la réception, l'ensemble des n sous-réseaux linéaires horizontaux 6 fournit n signaux à un premier circuit de formation de faisceau 8 qui réalise une formation réduite de faisceau d'ordre n en site tandis que l'ensemble des m sous-réseaux linéaires verticaux 7 fournit m signaux à un deuxième circuit de formation de faisceau 9 qui réalise une formation réduite de faisceau d'ordre m en gisement.For the rest, reference is made to FIG. 3 which separately represents the two nested sets of linear sub-networks 6, 7 to facilitate the explanation. The antenna is pointed electronically at reception, and at transmission in the case of a radar, by means of phase shift modules. On reception, all of the n horizontal linear sub-networks 6 supply n signals to a first beam forming circuit 8 which performs a reduced n- order beam formation in elevation while all of the m sub-networks vertical lines 7 provides m signals to a second beam forming circuit 9 which performs reduced beam formation of order m in bearing.

Ces deux formations réduites de faisceau ne participent pas au pointage du lobe principal de l'antenne mais à l'antibrouillage dans les autres directions. Les lobes principaux de leurs diagrammes de rayonnement pointent dans la même direction imposée par les modules déphaseurs.These two reduced beam formations do not participate in the pointing the main lobe of the antenna but to the jamming in the other directions. The main lobes of their diagrams radiation point in the same direction imposed by the modules phase shifters.

La formation réduite de faisceau en site donne un diagramme de rayonnement sans lobes de réseau ou lobes diffus en direction du gisement puisqu'elle s'effectue sur les signaux de sous-réseaux linéaires horizontaux pleins et avec des lobes de réseau ou lobes diffus en direction du site compensés par la possibilité d'un ajustement de n-1 zéros en site.The reduced formation of beam in elevation gives a radiation pattern without grating lobes or diffuse lobes in the direction of the deposit since it takes place on the signals of solid horizontal linear sub-grids and with grating lobes or diffuse lobes in direction of the site compensated by the possibility of an adjustment of n -1 zeros in site.

La formation réduite de faisceau en gisement donne un diagramme de rayonnement sans lobes de réseau ou lobes diffus en direction du site puisqu'elle s'effectue sur les signaux des sous-réseaux linéaires verticaux pleins et avec des lobes de réseau ou lobes diffus en direction du gisement compensé par la possibilité d'ajustement de m-1 zéros en gisement.The reduced formation of beam in bearing gives a radiation diagram without lobes of lattice or diffuse lobes in direction of the site since it is carried out on the signals of the vertical linear sub-networks full and with lobes of lattice or diffuse lobes in direction of the deposit offset by the possibility of adjusting m -1 zeros in the deposit.

Les deux circuits de formation de faisceau 8 et 9 peuvent opérer des formations réduites de faisceau par le calcul et être réalisés au moyen d'un calculateur. Les n+m signaux de sortie des n+m sous-réseaux linéaires horizontaux et verticaux 6 et 7 sont alors démodulés en cohérence et numérisés avant de lui être appliqués. Le calculateur peut effectuer les formations réduites de faisceau en site et en gisement de manière alternée, l'ordre de formation en site puis en gisement ou l'inverse n'ayant aucune influence.The two beam forming circuits 8 and 9 can operate reduced beam formations by calculation and be produced by means of a computer. The n + m output signals of the n + m horizontal and vertical linear sub-networks 6 and 7 are then demodulated in coherence and digitized before being applied to it. The computer can perform the reduced beam formation in elevation and in bearing alternately, the order of formation in elevation then in bearing or vice versa having no influence.

Les signaux délivrés par les deux circuits de formation de faisceau 8 et 9 sont ensuite appliqués à un circuit de combinaison 10 qui en effectue le produit ou la convolution et délivre un signal unique de sortie d'antenne.The signals delivered by the two training circuits of bundle 8 and 9 are then applied to a combination circuit 10 which performs the product or convolution and issues a single output signal antenna.

Le signal unique de sortie d'antenne apparaít, lorsqu'il a pour origine une seule source émettrice captée par l'antenne, comme le signal de réception d'une antenne qui aurait, pour diagramme de rayonnement, le produit des deux diagrammes de rayonnement des formations réduites de faisceau en site et en gisement ; diagramme de rayonnement qui est dépourvu de lobes de réseau et de lobes diffus dû au sous-échantillonnage car l'un des diagrammes composants n'a pas de lobe de réseau ou de lobe diffus dans le plan site et l'autre diagramme composant n'a pas de lobes de réseau ou de lobe diffus dans le plan gisement.The single antenna output signal appears, when it has origin a single transmitting source picked up by the antenna, as the signal of reception of an antenna which would have, for radiation diagram, the produces two radiation patterns of reduced formations of beam in site and in deposit; radiation pattern which is lacking network lobes and diffuse lobes due to subsampling because one of the component diagrams does not have a lobe or lobe diffuse in the site map and the other component diagram has no lobes of network or diffuse lobe in the deposit plan.

On obtient alors les propriétés d'une antenne à formation de faisceau non réduite portant sur n×m points en utilisant seulement deux formations de faisceau réduites à n+m points.We then obtain the properties of an antenna with unreduced beamforming on n × m points by using only two beamformings reduced to n + m points.

Les figures 4a et 4b montrent, tracées dans un trièdre de référence dont l'axe OX est gradué en angle de gisement, l'axe OY en angle de site et l'axe OZ en niveau de signal, les coupes dans les plans XOZ et YOZ des surfaces des diagrammes de rayonnement obtenus en sortie des deux circuits de formation réduite de faisceau 9 et 8.Figures 4a and 4b show, plotted in a trihedron of reference whose OX axis is graduated in bearing angle, OY axis in angle of the site and the OZ axis in signal level, the cross-sections in the XOZ planes and YOZ of the surfaces of the radiation patterns obtained at the output of two reduced beam formation circuits 9 and 8.

La figure 4a représente le diagramme de rayonnement obtenu en sortie du circuit de formation de faisceau 9 opérant sur les signaux des m sous-réseaux linéaires verticaux 7. Il comporte un lobe principal fin orienté dans la direction de pointage imposée par les réglages des modules déphaseurs individuels entouré de lobes secondaires de faibles amplitudes dans le plan site YOZ car les sous-réseaux à la base de la formation réduite de faisceau sont des sous-réseaux linéaires verticaux pleins, et d'amplitudes plus marquées dans le plan gisement XOZ mais avec des zéros intercalaires dont les positions sont ajustables par l'action adaptative de la formation réduite de faisceau.FIG. 4a represents the radiation diagram obtained at the output of the beam forming circuit 9 operating on the signals of the m vertical linear sub-networks 7. It comprises a fine main lobe oriented in the pointing direction imposed by the settings of the phase shift modules individual surrounded by side lobes of small amplitudes in the YOZ site plane because the sub-networks at the base of the reduced beam formation are full vertical linear sub-networks, and of more marked amplitudes in the XOZ field plane but with spacer zeros whose positions are adjustable by the adaptive action of reduced beamforming.

La figure 4b représente le diagramme de rayonnement obtenu en sortie du circuit de formation de faisceau 8 opérant sur les signaux de n sous-réseaux linéaires horizontaux 6. Comme le précédent, il comporte un lobe principal fin orienté dans la direction de pointage imposée par les réglages des modules déphaseurs individuels. Mais celui-ci est entouré de lobes secondaires de faibles amplitudes dans le plan gisement XOZ car les sous-réseaux à la base de la formation réduite de faisceau sont des sous-réseaux linéaires horizontaux pleins, et d'amplitudes plus marquées dans le plan site YOZ mais avec des zéros intercalaires dont les positions sont ajustables par l'action adaptative de la formation réduite de faisceau.FIG. 4b represents the radiation diagram obtained in output of the beam forming circuit 8 operating on the signals of n Horizontal linear sub-networks 6. Like the previous one, it has a fine main lobe oriented in the direction of pointing imposed by the individual phase shift module settings. But this one is surrounded by small amplitude side lobes in the XOZ plane, because the subnets at the base of reduced beam formation are subnets full horizontal lines, and of more marked amplitudes in the YOZ site map but with insert zeros whose positions are adjustable by the adaptive action of reduced beam formation.

Les actions adaptatives des deux formations réduites de faisceau s'effectuent indépendamment l'une dans le plan site, l'autre dans le plan gisement en créant des zéros en forme de vallées rappelées sur les figures 4a, 4b par des traits en pointillés, chaque vallée ne consommant qu'un degré de liberté sur une seule des deux formations réduites de faisceau. Le produit des deux diagrammes présente deux séries de zéros ajustables angulairement l'une dans le plan site, l'autre dans le plan gisement ce qui montre l'intérêt d'effectuer entre les signaux des deux circuits de formation réduite de faisceau une combinaison non linéaire telle qu'un produit ou une convolution. De plus, il est intéressant de soumettre à un seuillage les signaux des deux circuits de formation réduite de faisceau afin d'éviter qu'un signal parasite capté par l'intermédiaire de l'une des deux formations réduites de faisceau ne soit validé par du bruit thermique provenant de l'autre formation réduite de faisceau. Il n'y a alors aucune incompatibilité pour que le seuil choisi ne soit pas celui de limitation des fausses alarmes par bruit dans un processus de détection.The adaptive actions of the two reduced beam formations one independently in the site plan, the other in the plan deposit by creating zeros in the form of valleys recalled in the figures 4a, 4b by dotted lines, each valley consuming only one degree of freedom on only one of the two reduced beam formations. The product of the two diagrams presents two sets of adjustable zeros angularly one in the site plan, the other in the deposit plan which shows the advantage of performing between the signals of the two training circuits reduced beam a nonlinear combination such as a product or a convolution. In addition, it is interesting to subject the thresholds to signals from the two reduced beam forming circuits to prevent a parasitic signal received by one of the two formations reduced beam is only validated by thermal noise from the other reduced beam formation. There is then no incompatibility so that the threshold chosen is not that of limiting false alarms by noise in a detection process.

La figure 5 illustre le schéma d'antenne réseau auquel on aboutit. Celle-ci comporte un réseau d'éléments rayonnants disposés en lignes et colonnes selon un maillage d'environ λ/2 et équipés de modules déphaseurs individuels. Pour plus de clarté les éléments rayonnants sont montrés sans leurs modules déphaseurs et le réseau est représenté dédoublé en 12 et 12'. En 12 apparaít le premier regroupement en réception des éléments rayonnants en m sous-réseaux linéaires verticaux 13 délivrant m signaux à un premier circuit de formation réduite de faisceau 14 opérant dans le plan gisement. En 12' apparaít le deuxième regroupement en réception des éléments rayonnants en n sous-réseaux linéaires horizontaux 15 délivrant n signaux à un deuxième circuit de formation réduite de faisceau 16 opérant dans le plan site. Deux circuits à seuil 17, 18 placés en sortie des deux circuits de formation de faisceau 14, 16 assurent un ébasage de leurs signaux avant que ces derniers ne soient appliqués à un circuit de combinaison non linéaire 19 qui en effectue le produit ou la convolution.FIG. 5 illustrates the network antenna diagram to which we end up. This comprises a network of radiating elements arranged in rows and columns in a mesh of approximately λ / 2 and equipped with individual phase-shifting modules. For clarity, the radiating elements are shown without their phase shift modules and the network is shown split in 12 and 12 '. At 12 appears the first grouping in reception of the radiating elements in m vertical linear sub-networks 13 delivering m signals to a first reduced beam forming circuit 14 operating in the plane of the deposit. In 12 'appears the second grouping on reception of the radiating elements in n horizontal linear sub-arrays 15 delivering n signals to a second reduced beam formation circuit 16 operating in the site plane. Two threshold circuits 17, 18 placed at the output of the two beam forming circuits 14, 16 provide a basing of their signals before the latter are applied to a nonlinear combination circuit 19 which produces the product or the convolution thereof.

L'opération produit peut être une simple multiplication, une addition de signaux dont on a pris le logarithme ou une opération logique de type "et" commandée par des signaux rendus préalablement bivalents.The product operation can be a simple multiplication, a addition of signals which we have taken the logarithm or a logical operation of type "and" controlled by signals made previously bivalent.

La multiplication améliore la résolution angulaire car, à largeur de lobe principal identique, l'atténuation en dB est double de celle de chacun des deux ensembles de sous-réseaux considérés isolément, mais cela, au prix d'une perte de 6 dB en rapport signal sur bruit.Multiplication improves angular resolution because, at width of identical main lobe, the attenuation in dB is double that of each of the two sets of subnets considered in isolation, but this at the price of a 6 dB loss in signal to noise ratio.

L'opération "et" logique n'apporte ni gain en résolution ni perte en rapport signal sur bruit.The logical "and" operation brings neither gain in resolution nor loss in signal to noise ratio.

Les deux signaux délivrés par les deux circuits de formation de faisceau étant d'amplitudes identiques, on est dans les conditions optimales d'une opération de multiplication.The two signals delivered by the two training circuits of beam being of identical amplitudes, we are in optimal conditions of a multiplication operation.

L'opération de convolution, plus performante mais plus complexe à mettre en oeuvre que l'opération produit, permet d'atténuer encore plus fortement les signaux brouilleurs captés dans l'une des formations réduites de faisceau et pas dans l'autre, par absence de corrélation avec le signal émis par le radar, ou entre eux.The convolution operation, more efficient but more complex to implement that the operation produced, allows to mitigate even more strongly the interfering signals received in one of the reduced formations of beam and not in the other, by absence of correlation with the signal emitted by the radar, or between them.

L'antenne réseau peut être lacunaire ou raréfiée au lieu d'être pleine. Dans ce cas, ses éléments rayonnants et leurs modules déphaseurs individuels sont disposés, comme représenté sur la figure 6, selon un quadrillage lâche de rangées 21 et colonnes 20 pleines, et organisés, à la réception, en deux ensembles imbriqués de sous-réseaux linéaires pleins :

  • un premier ensemble non plein de x sous-réseaux 20 linéaires, pleins, verticaux, juxtaposés, constitués chacun de m éléments rayonnants, et
  • un deuxième ensemble non plein de y sous-réseaux 21 linéaires, pleins, horizontaux, superposés, constitués chacun de n éléments rayonnants.
The network antenna may be incomplete or scarce instead of being full. In this case, its radiating elements and their individual phase-shifting modules are arranged, as shown in FIG. 6, according to a loose grid of rows 21 and full columns 20, and organized, at reception, in two nested sets of linear sub-networks full:
  • a first non-full set of x linear, solid, vertical, juxtaposed sub-networks 20, each consisting of m radiating elements, and
  • a second non-full set of linear, solid, horizontal, superimposed y subnetworks 21, each consisting of n radiating elements.

Avantageusement, l'espacement entre les sous-réseaux linéaires de chaque ensemble croít, en progression géométrique, d'un bord à l'autre de l'antenne, mais d'autres espacements sans périodicité harmonique sont possibles.Advantageously, the spacing between the linear sub-networks of each set grows, in geometric progression, from one edge to the other of the antenna, but other spacings without harmonic periodicity are possible.

Les éléments rayonnants situés aux points de croisement des sous-réseaux linéaires verticaux et horizontaux participent aux deux ensembles et sont équipés de modules déphaseurs individuels à sortie double délivrant des signaux identiques en amplitude et en phase. Les autres éléments rayonnants ont des modules déphaseurs individuels à sortie simple. Qu'ils soient issus de modules à sortie simple ou double, les signaux sont de même amplitude et ont des phases relatives qui sont celles de la loi de pointage de l'antenne.The radiating elements located at the crossing points of the vertical and horizontal linear subnets participate in both assemblies and are fitted with individual output phase shift modules double delivering identical signals in amplitude and phase. The other radiating elements have individual phase shift modules with output simple. Whether coming from single or double output modules, the signals are of the same magnitude and have relative phases which are those of the law pointing the antenna.

Les sorties des sous-réseaux linéaires verticaux 20 du premier ensemble sont connectées aux entrées d'un premier circuit 22 de formation de faisceau dans le plan gisement tandis que les sorties des sous-réseaux linéaires horizontaux 21 du deuxième ensemble sont connectées aux entrées d'un deuxième circuit 23 de formation de faisceau dans le plan site.The outputs of the vertical linear sub-networks 20 of the first together are connected to the inputs of a first training circuit 22 beam in the reservoir plane while the outputs of the subnetworks horizontal lines 21 of the second set are connected to inputs of a second beam-forming circuit 23 in the site plan.

Bien que cela ne soit pas représenté dans un but de simplification de la figure, les deux sorties des deux circuits de formation de faisceau 22, 23 sont, comme dans le cas de la figure 5, connectées par l'intermédiaire de deux circuits à seuil aux deux entrées d'un circuit de combinaison non linéaire effectuant un produit ou une convolution pour engendrer le signal de sortie d'antenne.Although this is not shown for the sake of simplification in the figure, the two outputs of the two beam forming circuits 22, 23 are, as in the case of FIG. 5, connected via two threshold circuits at the two inputs of a combination circuit no linear performing a product or a convolution to generate the signal of antenna output.

L'antenne est pointée électroniquement par les modules déphaseurs individuels, à la réception et également à l'émission dans le cas d'un radar.The antenna is pointed electronically by the modules individual phase shifters, on reception and also on transmission in the case of a radar.

Le premier circuit 22 de formation réduite de faisceau délivre, à la réception, un signal correspondant à celui d'une antenne ayant un diagramme de rayonnement avec, dans le plan site, de faibles lobes secondaires définis par la loi de pondération appliquée analogiquement.à chaque sous-réseau linéaire vertical plein 20 et, dans le plan gisement, des lobes de réseau ou lobes diffus selon que la raréfaction de l'ensemble des sous-réseaux linéaires verticaux pleins 20 est répartie périodiquement ou aléatoirement. La figure 7a donne un exemple d'un tel diagramme avec des lobes diffus.The first circuit 22 of reduced beam formation delivers, at the reception, a signal corresponding to that of an antenna having a radiation pattern with weak lobes in the site plane secondary defined by the weighting law applied analogically. each full vertical linear sub-network 20 and, in the reservoir plane, network lobes or diffuse lobes depending on whether the scarcity of all full vertical linear subnets 20 is distributed periodically or randomly. Figure 7a gives an example of such a diagram with diffuse lobes.

Le deuxième circuit 23 de formation réduite de faisceau délivre, à la réception, un signal correspondant à celui d'une antenne ayant un diagramme de rayonnement avec, dans le plan gisement, de faibles lobes secondaires définis par la loi de pondération appliquée analogiquement à chaque sous-réseau linéaire horizontal 21 et, dans le plan site, des lobes de réseau ou lobes diffus selon que la raréfaction de l'ensemble des sous-réseaux linéaires horizontaux pleins 21 est répartie périodiquement ou aléatoirement. La figure 7b donne un exemple d'un tel diagramme avec des lobes diffus.The second circuit 23 of reduced beam formation delivers, at reception, a signal corresponding to that of an antenna having a radiation pattern with weak lobes in the deposit plane secondary defined by the law of weighting applied analogously to each horizontal linear sub-network 21 and, in the site plane, lobes of diffuse network or lobes depending on whether the scarcity of all the sub-networks full horizontal linear 21 is distributed periodically or randomly. Figure 7b gives an example of such a diagram with diffuse lobes.

Dans leur plan respectif site et gisement, les deux formations réduites de faisceau obtenues peuvent être figées ou adaptatives et, dans ce dernier cas, permettre le positionnement de zéros, de façon séparée en site et en gisement comme illustré précédemment aux figures 4a et 4b.In their respective site and deposit plan, the two formations beam reductions obtained can be fixed or adaptive and, in the latter case, allowing the positioning of zeros, separately in site and deposit as illustrated previously in Figures 4a and 4b.

Le seuillage des deux signaux résultant des deux formations réduites de faisceau séparées dans les plans site et gisement et leur combinaison non linéaire par produit ou convolution permet d'obtenir un signal de réception ayant des propriétés similaires à celui d'une antenne à formation de faisceau totale avec seulement deux formations réduites de faisceau orthogonales de moments cumulés n+m. Le nombre de degrés de liberté, autrement dit, le nombre de zéros adaptatifs réalisables n'est bien sûr que (m-1)+(n-1) mais les lobes de réseau ou diffus ont été éliminés par l'opération de produit ou de convolution sous la seule réserve que les lobes secondaires orthogonaux à ces lobes de réseau ou diffus aient bien été eux-mêmes éliminés par l'opération de seuillage sur les deux voies d'où, l'intérêt de seuils adaptatifs prenant en compte le niveau des signaux perturbateurs, résidus de fouillis par exemple. Les perturbateurs du type brouillage seront traités au premier degré par pointage de zéros dans les deux formations réduites de faisceau adaptatives, mais des résidus éventuels recevront un traitement complémentaire par la combinaison des opérations de seuillage et de produit ou de convolution.The thresholding of the two signals resulting from the two reduced beam formations separated in the site and deposit planes and their non-linear combination by product or convolution makes it possible to obtain a reception signal having properties similar to that of a beam-forming antenna total with only two reduced orthogonal beam formations of cumulative moments n + m . The number of degrees of freedom, in other words, the number of adaptive zeros achievable is of course only ( m -1) + ( n -1) but the lattices or diffuse lobes have been eliminated by the product operation or convolution subject only to the fact that the secondary lobes orthogonal to these lattices or diffuse lobes have themselves been eliminated by the thresholding operation on the two channels, hence the advantage of adaptive thresholds taking into account the level disturbing signals, such as clutter residue. Interference-type disturbers will be treated in the first degree by zeros in the two reduced adaptive beam formations, but possible residues will receive additional treatment by the combination of thresholding and product or convolution operations.

L'architecture d'antenne réseau proposée évite les limitations de l'art antérieur par une organisation de ses éléments rayonnants basée sur une juxtaposition côte à côte en parallèle, de m sous-réseaux linéaires de n éléments contigus entre eux et dont les centres de phase sont espacés selon des critères d'échantillonnage de la surface d'antenne qui évitent la création de lobes de réseau ou de diffus élevés. Limitée à cette organisation, l'antenne ne pourrait être dotée que d'une formation de faisceau dans le plan perpendiculaire aux sous-réseaux. Pour éviter cela, les éléments rayonnants de l'antenne sont réutilisés pour former une deuxième juxtaposition côte à côte en parallèle de n sous-réseaux de m éléments orthogonaux aux premiers sous-réseaux et totalement imbriqués dans ceux-ci. A partir de ces deux ensembles de sous-réseaux orthogonaux, on réalise deux formations de faisceau à m et n moments dans deux plans orthogonaux dont on combine les signaux de façon non linéaire par produit ou convolution pour obtenir un signal de réception similaire à celui d'une antenne réseau à formation de réseau deux plans à n×m moments.The proposed network antenna architecture avoids the limitations of the prior art by an organization of its radiating elements based on a juxtaposition side by side in parallel, of m linear sub-networks of n elements contiguous to each other and whose centers of phase are spaced according to sampling criteria of the antenna surface which avoid the creation of high lobe or diffuse lobes. Limited to this organization, the antenna could only be provided with beam formation in the plane perpendicular to the sub-arrays. To avoid this, the radiating elements of the antenna are reused to form a second juxtaposition side by side in parallel with n sub-arrays of m elements orthogonal to the first sub-arrays and completely nested in them. From these two sets of orthogonal subnetworks, two beam formations are produced at m and n moments in two orthogonal planes whose signals are combined non-linearly by product or convolution to obtain a reception signal similar to that of '' a network antenna forming a two-plane network at n × m moments.

Dans l'art antérieur, il était possible d'obtenir une réduction analogue du nombre de moments pour une formation de faisceau deux plans par regroupement des éléments rayonnants de l'antenne réseau en sous-réseaux surfaciques non imbriqués mais cela s'accompagnait de l'existence de lobes de réseau ou de diffus à des niveaux élevés.In the prior art, it was possible to obtain a reduction analog of the number of moments for a two-plane beam formation by grouping the radiating elements of the network antenna into sub-networks non-nested surfaces but this was accompanied by the existence network or diffuse lobes at high levels.

En réalisant une opération de seuillage sur les deux signaux résultant des deux formations réduites de faisceau un plan, avant de les combiner pour simuler une formation de faisceau deux plans, on améliore le rapport signal à perturbateur car on supprime quasiment l'intervention du bruit thermique de chacun des deux signaux dans l'opération de produit ou de convolution permettant l'élaboration du signal de réception.By performing a thresholding operation on the two signals resulting from the two reduced beam formations a plane, before combine to simulate beam formation two planes, we improve the signal-to-disruptor ratio because it almost eliminates the intervention of the thermal noise of each of the two signals in the product operation or convolution allowing the development of the reception signal.

L'architecture d'antenne proposée présente deux voies de réception issues des deux formations réduites de faisceau sur lesquelles il peut être avantageux de réaliser, avant l'opération de produit ou de convolution, certains traitements tels que le filtrage Doppler des échos fixes dans le cas d'un radar, qui sont alors dédoublés. Le coût afférent à ce dédoublement est toutefois bien moindre que celui d'une formation totale de faisceau dans deux plans et est entièrement justifié par les performances obtenues en comparaison de celles d'une formation réduite de faisceau deux plans de l'art antérieur.The proposed antenna architecture presents two ways of reception from the two reduced beam formations on which it may be advantageous to carry out, before the product or convolution, certain treatments such as Doppler filtering of fixed echoes in the case of a radar, which are then split. The cost of this duplication is however much less than that of a total formation of beam in two planes and is fully justified by performance obtained in comparison with those of a reduced beam formation two plans of the prior art.

Dans l'art antérieur, les antennes réseau, lacunaires ou raréfiées sont affectées de puissants lobes de réseau ou diffus. L'architecture d'antenne proposée évite cet inconvénient majeur. De plus, il convient de remarquer que si les propriétés d'adaptativité ne sont pas requises dans les formations réduites de faisceau, ces dernières peuvent être réalisées en analogique.In the prior art, network antennas, incomplete or rarefied are affected by powerful lattices or diffuse lobes. Architecture proposed antenna avoids this major drawback. In addition, note that if the adaptivity properties are not required in the reduced beam formations, these can be achieved by analog.

Les limites de cette architecture appliquée à une antenne réseau lacunaire ou raréfiée résident dans le fait qu'elle ne permet l'obtention que d'un seul lobe principal ce qui reste cependant compatible avec une écartométrie monopulse, et qu'elle nécessite deux voies de réception dont le coût est bien moindre que celui d'une antenne pleine et entièrement justifié par les propriétés et performances obtenues en comparaison de celles d'une antenne lacunaire ou raréfiée de l'art antérieur.The limits of this architecture applied to a network antenna incomplete or scarce resides in the fact that it only allows obtaining of a single main lobe which remains compatible with a monopulse variometry, and that it requires two reception channels, the cost is much lower than that of a full and fully justified antenna by the properties and performances obtained in comparison with those of a incomplete or rarefied antenna of the prior art.

La figure 8 donne un exemple de réalisation d'une antenne réseau raréfiée non périodique à formations réduites de faisceau mettant en oeuvre l'architecture proposée.Figure 8 gives an example of an antenna rarefied non-periodic network with reduced beam formations putting in the proposed architecture.

Cette antenne est constituée de deux ensembles imbriqués de sous-réseaux linéaires orthogonaux d'éléments rayonnants :

  • un premier ensemble de onze sous-réseaux linéaires horizontaux 30 de quatre vingt dix éléments rayonnants chacun, et
  • un deuxième ensemble de treize sous-réseaux linéaires verticaux 31 de soixante seize éléments rayonnants chacun.
This antenna consists of two nested sets of orthogonal linear sub-networks of radiating elements:
  • a first set of eleven horizontal linear sub-networks 30 of ninety radiating elements each, and
  • a second set of thirteen vertical linear sub-networks 31 of seventy-six radiating elements each.

Les éléments rayonnants sont équipés de modules déphaseurs individuels. Pour permettre un balayage électronique sur ± 45° sans lobes de réseau sur les axes non lacunaires des deux ensembles d'éléments rayonnants, l'espacement d'élément à élément dans les sous-réseaux est de 0,55 λ. Pour éviter les lobes de réseau à niveau élevé sur les axes lacunaires des deux ensembles d'éléments rayonnants, et avoir préférablement du diffus étalé et à crêtes plus basses l'espacement entre leurs sous-réseaux est variable et croít d'un bord à l'autre de l'antenne par exemple en progression géométrique. L'antenne obtenue s'inscrit dans une surface de 49,5 λ sur 41,8 λ donnant une directivité à 3 dB d'environ 1,45 degré par 1,7 degré. L'antenne pleine équivalente sous cet aspect comporterait 6.840 éléments rayonnants et modules déphaseurs individuels alors que celle-ci n'en comporte que 1835. Le coefficient de raréfaction est donc de 3,73.The radiating elements are fitted with phase shift modules individual. To allow electronic scanning over ± 45 ° without lobes of network on the non-incomplete axes of the two sets of elements radiant, the element-to-element spacing in subnets is 0.55 λ. To avoid high level lobes on the axes gaps in the two sets of radiating elements, and having preferably spread diffuse and lower ridges the spacing between their sub-networks is variable and grows from one edge to the other of the antenna by example in geometric progression. The antenna obtained is part of a 49.5 λ by 41.8 λ surface giving a directivity of about 3 dB 1.45 degrees by 1.7 degrees. The full antenna equivalent in this aspect would include 6,840 radiating elements and individual phase shift modules whereas this one comprises only 1835. The coefficient of rarefaction is therefore 3.73.

Les signaux de sortie des onze sous-réseaux linéaires horizontaux 30 du premier ensemble sont numérisés avant d'être appliqués à un premier circuit de formation de faisceau par le calcul 32 qui effectue une formation adaptative réduite de faisceau dans le plan vertical ou plan site sur onze points en permettant ainsi l'antibrouillage de dix directions différentes en site.The output signals of the eleven linear subnetworks horizontal 30 of the first set are scanned before being applied to a first beam forming circuit by calculation 32 which performs reduced adaptive beam formation in the vertical or planar plane eleven-point site, allowing ten directions anti-jamming different on site.

Les signaux de sortie des treize sous-réseaux linéaires verticaux 31 du deuxième ensemble sont numérisés avant d'être appliqués à un deuxième circuit de formation de faisceau par le calcul 33 qui effectue une formation adaptative réduite de faisceau dans le plan horizontal ou plan gisement sur treize points en permettant ainsi l'antibrouillage de douze directions différentes en gisement.The output signals of the thirteen vertical linear sub-networks 31 of the second set are digitized before being applied to a second beamforming circuit by calculation 33 which performs a reduced adaptive beamforming in the horizontal or planar plane deposit at thirteen points, thus allowing the jamming of twelve different directions in deposit.

Les deux signaux délivrés par les deux circuits de formation de faisceau par le calcul 32, 33 ou plutôt, leurs modules sont appliqués à deux circuits à seuil 34, 35.The two signals delivered by the two training circuits of beam by calculation 32, 33 or rather, their modules are applied to two threshold circuits 34, 35.

Les signaux délivrés par les deux circuits à seuil 34 et 35 sont ensuite appliqués aux entrées d'un circuit logique de type 36 effectuant leur produit et délivrant le signal de réception d'antenne.The signals delivered by the two threshold circuits 34 and 35 are then applied to the inputs of a type 36 logic circuit performing their produces and delivers the antenna reception signal.

On remarque que le nombre total de moments des formations réduites de faisceau réalisées est de 24 ce qui donne la possibilité d'antibrouiller 22 directions différentes. cette caractéristique est très appréciable, surtout si l'on prend en compte le fait que des brouilleurs alignés sur un même axe en site ou en gisement sont traités simultanément par la création d'un seul zéro en raison de sa conformation en vallée. Ceci est très intéressant face au concept de brouillage diffus par illumination d'une surface diffusante.We note that the total number of moments of the formations beam reduced realized is 24 which gives the possibility to jam 22 different directions. this characteristic is very appreciable, especially if we take into account the fact that jammers aligned on the same axis in site or in deposit are treated simultaneously by creating a single zero due to its conformation in the valley. This is very interesting when faced with the concept of diffuse interference by illumination of a diffusing surface.

Claims (13)

  1. Antenna with array of radiating elements, characterized in that its radiating elements are grouped, for reception, into two sets of parallel linear sub-arrays (6, 7) pointing in two different directions, and in that it includes two beam formation circuits (8, 9) each receiving the signals from one of the sets of linear sub-arrays (6, 7) and each delivering a reduced-beam-formation signal, and an output circuit (10) delivering a reception signal from a nonlinear combination of the two reduced-beam-formation signals generated by the two beam formation circuits (8, 9).
  2. Antenna according to Claim 1, characterized in that the directions of the linear sub-arrays (6, 7) of the two sets are mutually orthogonal.
  3. Antenna according to Claim 2, characterized in that the direction of the linear sub-arrays (6) of one of the sets is horizontal whilst the direction of the linear sub-arrays (7) of the other set is vertical.
  4. Antenna according to Claim 1, characterized in that the two sets of linear sub-arrays (6, 7) are nested.
  5. Antenna according to Claim 1, characterized in that it is sparse, its array of radiation elements including gaps and the missing radiating elements being fewer in number than the radiating elements present.
  6. Antenna according to Claim 1, characterized in that it is rarefied, its array of radiating elements including gaps and the missing radiating elements being greater in number than the radiating elements present.
  7. Antenna according to Claim 1, characterized in that in each set of parallel linear sub-arrays (20, 21), the parallel linear sub-arrays (20, 21) are separated by a spacing which varies from one edge to the other of the antenna.
  8. Antenna according to Claim 7, characterized in that the said spacing varies from one edge to the other of the antenna according to a geometric progression.
  9. Antenna according to Claim 1, characterized in that it furthermore includes two threshold circuits (17, 18) interposed between the two beam formation circuits (8, 9) and the output circuit (10).
  10. Antenna according to Claim 1, characterized in that the output circuit (10) is a convolution circuit.
  11. Antenna according to Claim 1, characterized in that the output circuit (10) is a multiplier circuit.
  12. Antenna according to Claim 1, characterized in that it furthermore includes, interposed between the two beam formation circuits (32, 33) and the output circuit (36), two threshold circuits (34, 35) which transform the signals delivered by the two beam formation circuits (32, 33) into bivalent signals, and in that the output circuit (36) is a logic circuit of the "and" type.
  13. Antenna according to Claim 1, characterized in that the beam formation circuits (8, 9) are computerized beam formation circuits affording an antijamming function.
EP94402449A 1993-11-02 1994-10-28 Antenna with array of radiating elements Expired - Lifetime EP0651461B1 (en)

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FR9312995A FR2712121B1 (en) 1993-11-02 1993-11-02 Array of radiating elements antenna.

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JPH07273530A (en) 1995-10-20
CA2134055A1 (en) 1995-05-03
DE69410059D1 (en) 1998-06-10
FR2712121B1 (en) 1995-12-15
DE69410059T2 (en) 1998-09-03
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FR2712121A1 (en) 1995-05-12
US5675343A (en) 1997-10-07

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