EP0145597B1 - Plane periodic antenna - Google Patents

Plane periodic antenna Download PDF

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Publication number
EP0145597B1
EP0145597B1 EP84402523A EP84402523A EP0145597B1 EP 0145597 B1 EP0145597 B1 EP 0145597B1 EP 84402523 A EP84402523 A EP 84402523A EP 84402523 A EP84402523 A EP 84402523A EP 0145597 B1 EP0145597 B1 EP 0145597B1
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EP
European Patent Office
Prior art keywords
teeth
antenna according
plane
antenna
tooth
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Expired
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EP84402523A
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German (de)
French (fr)
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EP0145597A3 (en
EP0145597A2 (en
Inventor
Alain Bizouard
Gérard Dubost
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Thales SA
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Thomson CSF SA
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Publication of EP0145597A3 publication Critical patent/EP0145597A3/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
    • H01Q1/38—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith formed by a conductive layer on an insulating support
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q13/00—Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
    • H01Q13/10—Resonant slot antennas
    • H01Q13/106—Microstrip slot antennas

Definitions

  • the present invention relates to flat periodic antennas of the log-periodic type.
  • periodic antennas are very broadband antennas, independent of the frequency of the feed signal. They consist of radiating elements whose dimensions are deduced from each other by a homothety of ratio T from a given expansion pole. Two consecutive radiating elements have the same properties, one at a frequency f which is its resonant frequency, and the other at the frequency f / T or f ⁇ . The factor is generally close to unity, so that this type of antenna has rather little different characteristics over a large frequency band.
  • the flat periodic antennas are formed of flat radiating elements as opposed to the wire radiating elements and in general to the volumetric elements.
  • a flat antenna is therefore understood to mean an antenna whose radiating elements have a small thickness, this dimension being insignificant with respect to the lengths and widths of the elements.
  • a flat periodic antenna consists of two plates in the same plane each formed by two sets of generally trapezoidal teeth.
  • the antenna therefore consists of two half-antennas which are supplied in symmetry from their top.
  • the radiation pattern is symmetrical with respect to the plane of the antenna with maxima following the normal to this plane.
  • the antenna therefore has a normal directivity in terms of its structure.
  • the invention proposes a flat broadband periodic antenna making it possible to operate without disturbance when it is embedded on a flat or curved metal structure and moreover to have a main lobe inclined relative to the normal metallic structure.
  • the invention therefore provides a planar periodic antenna mainly characterized in that it comprises radiating elements formed by two series of planar teeth whose dimensions are deduced from each other from a homothety of ratio T and pale of expansion 0, the teeth of one of the series being inserted between the teeth of the other series and the end of a given tooth being separated from the edge of the plate situated between two teeth of the other series by a predetermined interval ; a feed line placed in a plane close to the plane of the plate makes it possible to feed the teeth from the predetermined interval; a ground plane located at a distance H n from each tooth, varying as a function of the wavelength ⁇ n of resonance of each tooth, the antenna thus being able to be embedded in a flat or curved metallic structure without changing the aerodynamics this structure.
  • the plane of the radiating structure P is defined as being the plane of the sheet and the axis OD, an axis which passes through the expanson pole 0 and which is the longitudinal axis of the antenna.
  • FIG. 2 therefore represents a section along a plane containing the axis AB perpendicular to the axis OD and
  • FIG. 3 represents a section along a plane perpendicular to the plane P and containing the axis OD.
  • Figures 1, 2 and 3 shown being sections along three different planes of the planar periodic antenna according to the invention are described in the following without dissociation.
  • the teeth have a trapezoidal shape according to a preferred embodiment. It is obvious that the invention also applies to antennas whose teeth have a shape commonly used in conventional log-periodic antennas of the rectangular or axis in a circular arc of center the expansion pole.
  • the dimensions of the teeth D 1 , D 2 , D 3 are deduced from each other by a similarity of ratio ⁇ and of pole 0.
  • the dimensions Q 1 and Q 2 are deduced from each other by a similarity of ratio ⁇ and pole 0, the dimensions of Q 1 with respect to D, being obtained by multiplying by ⁇ .
  • the dimensions of the tooth closest to the pole define a first resonance frequency f M giving the order of magnitude of the upper limit of the pass band of the antenna as well as the dimensions of the tooth the most distant from the pale define a resonance frequency f m giving the order of magnitude of the lower limit of the pass band of the antenna.
  • the teeth D 1 , D 2 and D 3 are inscribed in an envelope defined by the lines E 1 and E 2 intersecting at the pole 0 and forming an angle a.
  • the teeth Q 1 and Q 2 are inscribed in an envelope defined by the lines F, and F 2 also intersecting at the pole 0 and making the same angle a.
  • This plate 1 is produced on the single metallized face of a printed circuit 2 of small thickness compared to the working wavelengths and which is shown in section in FIG. 2.
  • the wavelength ⁇ of the wave emitted varies between the extreme wavelengths ⁇ m and ⁇ M defined by the bandwidth.
  • a feed line 3 shown in dotted lines in FIG. 1 makes it possible to feed the antenna by exciting the radiating elements from points 4 and 5 which will be defined later.
  • This supply line 3 is produced by a metallized ribbon printed on a printed circuit 6, also of small thickness.
  • the metallized face of this circuit 6 is on the side of the non-metallized face of circuit 2, circuit 6 thus plays a protective role similar to that of a radome vis-à-vis the outside.
  • This circuit 6 is situated in a plane close to the plane of the circuit 2 and containing for example the expansion blade 0 or also in a plane parallel to the plane of the circuit 2 and close to the latter.
  • the two circuits 2 and 6 are separated by a dielectric 8 which can be (at the limit) the air medium or a honeycomb.
  • Line 3 describes trapezoidal teeth deduced by a similarity of pole 0 and of ratio ⁇ , the sides of which are parallel to the sides of the radiating teeth and pass through the midpoints 4 of the extreme segments l n of each tooth and through the midpoints 5 of the opposite segments L n .
  • the cut in width ⁇ n between these two points 4 and 5 makes it possible to excite the radiating elements.
  • the circuit 2 is integral with the metal structure 9 (its ground plane) on which the antenna is placed and the circuit 1 is maintained in electrical contact with this structure 9 at the level of the straight sections OE, and OF 2 passing through the points 5 and 15 respectively. This contact is ensured, for example by means of screws 10 and 11 shown in FIG. 1.
  • the section shown in Figure 3 highlights the height H n between the ground plane of each radiating element.
  • the choice of the dimensions of the radiating elements is carried out in such a way that, when the microstrip supply line 3 transmits a wave whose frequency is lower than the natural resonance frequency of a given tooth, the latter presents, at the level of its breaking, a low impedance which hardly disturbs the transmission of the line.
  • the electrical length K n must be less than ⁇ n / 2 so that the antenna is not mismatched.
  • the partial reflections due to the insertions of the radiating elements along the line do not accumulate.
  • Line 3 is closed on its characteristic impedance by means of a resistor 13 adapted at its end furthest from pole 0.
  • This resistor can be an element with localized constants or a dipole with distributed constants.
  • the supply line 3 is printed on the opposite face of the circuit 2, this circuit comprising on the other face the radiating elements.
  • it is a metallized dielectric substrate on its two faces.
  • the embodiment which has been described relates to a planar antenna, that is to say, to an antenna whose radiating elements have a very small thickness with respect to their length and their width. Furthermore, this antenna has a planar structure as a whole, that is to say that it can be embedded on a planar metallic structure. It is obvious that the invention also relates to antennas with a generally curved structure intended to be built into curved metallic structures (of the aircraft type). For this, it suffices to conform the circuits on which the elements of the antenna are placed to the shape of the metal structure while respecting the operating conditions given in the description.
  • the antenna according to the invention has first of all the advantages of a conventional log-periodic antenna, since it has a very wide bandwidth.
  • it is easily built into a metallic structure and therefore does not modify its aerodynamics since it is planar and its ground plane adapted to the embodiment can be embedded in the metallic structure.
  • It also has the advantage of being able to radiate in a direction inclined with respect to the normal to the plane of its structure, which is useful when for example the antenna is placed on an airplane.

Landscapes

  • Variable-Direction Aerials And Aerial Arrays (AREA)
  • Waveguide Aerials (AREA)

Description

La présente invention se rapporte aux antennes périodiques planes du type log-périodique.The present invention relates to flat periodic antennas of the log-periodic type.

De manière générale, les antennes périodiques sont des antennes très large bande, indépendantes de la fréquence du signal d'alimentation. Elles sont constituées par des éléments rayonnants dont les dimensions se déduisent les unes des autres par une homothétie de rapport T a partir d'un pôle d'expansion donné. Deux éléments rayonnants consécutifs présentent les mêmes propriétés l'un à une fréquence f qui est sa fréquence de résonance, et l'autre à la fréquence f/T ou fτ. Le facteur est généralement voisin de l'unité si bien que ce type d'antenne présente des caractéristiques assez peu différentes sur une grande bande de fréquence.In general, periodic antennas are very broadband antennas, independent of the frequency of the feed signal. They consist of radiating elements whose dimensions are deduced from each other by a homothety of ratio T from a given expansion pole. Two consecutive radiating elements have the same properties, one at a frequency f which is its resonant frequency, and the other at the frequency f / T or fτ. The factor is generally close to unity, so that this type of antenna has rather little different characteristics over a large frequency band.

Les antennes périodiques planes sont formées d'éléments rayonnants plats par opposition aux éléments rayonnants filaires et de manière générale aux éléments volumétriques. On entend donc par antenne plane, une antenne dont les éléments rayonnants ont une faible épaisseur, cette dimension étant non significative par rapport aux longueurs et aux largeurs des éléments.The flat periodic antennas are formed of flat radiating elements as opposed to the wire radiating elements and in general to the volumetric elements. A flat antenna is therefore understood to mean an antenna whose radiating elements have a small thickness, this dimension being insignificant with respect to the lengths and widths of the elements.

Classiquement, une antenne périodique plane est constituée de deux plaques dans un même plan formées chacune de deux séries de dents généralement trapézoïdales. L'antenne est par conséquent constituée de deux demi-antennes qui sont alimentées en symétrie à partir de leur sommet. Le diagramme de rayonnement est symétrique par rapport au plan de l'antenne avec des maxima suivant la normale à ce plan. L'antenne présente donc une directivité normale au plan de sa structure.Conventionally, a flat periodic antenna consists of two plates in the same plane each formed by two sets of generally trapezoidal teeth. The antenna therefore consists of two half-antennas which are supplied in symmetry from their top. The radiation pattern is symmetrical with respect to the plane of the antenna with maxima following the normal to this plane. The antenna therefore has a normal directivity in terms of its structure.

Dans certaines applications, notamment lorsqu'on désire placer l'antenne périodique sur une structure métallique plate ou galbée sans perturber l'aérodynamisme de cette structure, il est nécessaire d'utiliser des antennes périodiques planes. Or, le fonctionnement de l'antenne est perturbé car elle est plaquée sur la structure métallique qui se comporte alors comme un réflecteur non adapté au fonctionnement de l'antenne.In certain applications, in particular when it is desired to place the periodic antenna on a flat or curved metallic structure without disturbing the aerodynamics of this structure, it is necessary to use flat periodic antennas. However, the operation of the antenna is disturbed because it is pressed against the metal structure which then behaves like a reflector not suitable for the operation of the antenna.

Par ailleurs, il est quelquefois également nécessaire d'obtenir un diagramme de rayonnement dont le faisceau principal est incliné par rapport à la structure de l'antenne. Or une antenne périodique plane classique ne permet pas d'avoir une inclinaison du lobe principal par rapport au plan de sa structure.In addition, it is sometimes also necessary to obtain a radiation diagram whose main beam is inclined relative to the structure of the antenna. However, a conventional flat periodic antenna does not make it possible to have an inclination of the main lobe relative to the plane of its structure.

C'est pour pallier à ces deux inconvénients que l'invention propose une antenne périodique plane large bande permettant de fonctionner sans perturbation lorsqu'elle est encastrée sur une structure métallique plate ou galbée et de plus d'avoir un lobe principal incliné par rapport à la normale de la structure métallique.It is to overcome these two drawbacks that the invention proposes a flat broadband periodic antenna making it possible to operate without disturbance when it is embedded on a flat or curved metal structure and moreover to have a main lobe inclined relative to the normal metallic structure.

L'invention propose donc une antenne périodique plane principalement caractérisée en ce qu'elle comprend des éléments rayonnants formés de deux séries de dents planes dont les dimensions se déduisent les unes des autres à partir d'une homothétie de rapport T et de pâle d'expansion 0, les dents de l'une des séries étant intercalées entre les dents de l'autre série et l'extrémité d'une dent donnée étant séparée du bord de la plaque situé entre deux dents de l'autre série par un intervalle prédéterminé; une ligne d'alimentation placée dans un plan proche du plan de la plaque permet d'alimenter les dents à partir de l'intervalle prédéterminé; un plan de masse situé à une distance Hn de chaque dent, variant en fonction de la longueur d'onde Àn de résonance de chaque dent, l'antenne pouvant ainsi être encastrée dans une structure métallique plate ou galbée sans changer l'aérodynamisme de cette structure.The invention therefore provides a planar periodic antenna mainly characterized in that it comprises radiating elements formed by two series of planar teeth whose dimensions are deduced from each other from a homothety of ratio T and pale of expansion 0, the teeth of one of the series being inserted between the teeth of the other series and the end of a given tooth being separated from the edge of the plate situated between two teeth of the other series by a predetermined interval ; a feed line placed in a plane close to the plane of the plate makes it possible to feed the teeth from the predetermined interval; a ground plane located at a distance H n from each tooth, varying as a function of the wavelength Àn of resonance of each tooth, the antenna thus being able to be embedded in a flat or curved metallic structure without changing the aerodynamics this structure.

L'invention sera mieux comprise à l'aide de la description ci- après, donnée à titre d'exemple non limitatif et illustrée par les dessins annexes sur lesquels:

  • - la figure 1 représente une coupe de l'antenne selon l'invention suivant le plan de sa structure rayonnante;
  • - la figure 2 représente une coupe suivant un axe AB selon la figure 1;
  • - la figure 3 représente une coupe suivant un axe OD selon la figure 1;
  • - la figure 4 représente une variante de réalisation de l'antenne vue en coupe suivant l'axe AB.
The invention will be better understood with the aid of the description below, given by way of nonlimiting example and illustrated by the accompanying drawings in which:
  • - Figure 1 shows a section of the antenna according to the invention along the plane of its radiating structure;
  • - Figure 2 shows a section along an axis AB according to Figure 1;
  • - Figure 3 shows a section along an axis OD according to Figure 1;
  • - Figure 4 shows an alternative embodiment of the antenna seen in section along the axis AB.

Pour faciliter la compréhension, on définit le plan de la structure rayonnante P comme étant le plan de la feuille et l'axe OD, un axe qui passe par le pôle d'expanson 0 et qui est l'axe longitudinal de l'antenne.To facilitate understanding, the plane of the radiating structure P is defined as being the plane of the sheet and the axis OD, an axis which passes through the expanson pole 0 and which is the longitudinal axis of the antenna.

La figure 2 représente donc une coupe suivant un plan contenant l'axe AB perpendiculaire à l'axe OD et la figure 3 représente une coupe suivant un plan perpendiculaire au plan P et contenant l'axe OD.FIG. 2 therefore represents a section along a plane containing the axis AB perpendicular to the axis OD and FIG. 3 represents a section along a plane perpendicular to the plane P and containing the axis OD.

Par ailleurs, les figures 1, 2 et 3 représentées étant des coupes suivant trois plans différents de l'antenne périodique plane selon l'invention sont décrites dans ce qui suit sans dissociation.Furthermore, Figures 1, 2 and 3 shown being sections along three different planes of the planar periodic antenna according to the invention are described in the following without dissociation.

L'antenne représentée sur ces figures est une antenne périodique de pôle d'expansion 0. Une plaque conductrice 1 est constituée par une série de dents Dl à Dm, et une série de dents Q1 à Op, p - m ou p = m - 1, s'intercalant entre les dents de la première serie.The antenna shown in these figures is a periodic antenna of expansion pole 0. A conductive plate 1 is constituted by a series of teeth D l to D m , and a series of teeth Q 1 to Op, p - m or p = m - 1, inserted between the teeth of the first series.

Le nombre de dents varie selon les caractéristiques de rayonnement désirées pour l'antenne. On s'est limité à ne représenter que trois dents dans la première série et deux dans la deuxième série (m - 3 et p = 2).The number of teeth varies according to the radiation characteristics desired for the antenna. We limited ourselves to representing only three teeth in the first series and two in the second series (m - 3 and p = 2).

Les dents ont une forme trapézoïdale selon une forme préférée de réalisation. Il est bien évident que l'invention s'applique également aux antennes dont les dents ont une forme couramment utilisées dans les antennes log-périodique classiques du type rectangulaire ou à axe en arc de cercle de centre le pôle d'expansion.The teeth have a trapezoidal shape according to a preferred embodiment. It is obvious that the invention also applies to antennas whose teeth have a shape commonly used in conventional log-periodic antennas of the rectangular or axis in a circular arc of center the expansion pole.

Les dimensions des dents D1, D2, D3 se déduisent les unes des autres par une similitude de rapport τ et de pôle 0. De la même façon les dimensions Q1 et Q2 se déduisent l'une de l'autre par une similitude de rapport τ et de pôle 0, les dimensions de Q1 par rapport à D, étant obtenues en multipliant par τ.The dimensions of the teeth D 1 , D 2 , D 3 are deduced from each other by a similarity of ratio τ and of pole 0. In the same way the dimensions Q 1 and Q 2 are deduced from each other by a similarity of ratio τ and pole 0, the dimensions of Q 1 with respect to D, being obtained by multiplying by τ.

De manière connue en soi, les dimensions de la dent la plus proche du pôle définissent une première fréquence de resonance fM donnant l'ordre de grandeur de la limite supérieure de la bande passante de l'antenne de même que les dimensions de la dent la plus éloignée du pâle définissent une fréquence de resonance fm donnant l'ordre de grandeur de la limite inférieure de la bande passante de l'antenne.In a manner known per se, the dimensions of the tooth closest to the pole define a first resonance frequency f M giving the order of magnitude of the upper limit of the pass band of the antenna as well as the dimensions of the tooth the most distant from the pale define a resonance frequency f m giving the order of magnitude of the lower limit of the pass band of the antenna.

Les dents D1, D2 et D3 s'inscrivent dans une enveloppe définie par les droites E1 et E2 sécantes au pôle 0 et faisant un angle a.The teeth D 1 , D 2 and D 3 are inscribed in an envelope defined by the lines E 1 and E 2 intersecting at the pole 0 and forming an angle a.

Les dents Q1 et Q2 s'inscrivent dans une enveloppe définie par les droites F, et F2 sécantes également au pôle 0 et faisant le même angle a.The teeth Q 1 and Q 2 are inscribed in an envelope defined by the lines F, and F 2 also intersecting at the pole 0 and making the same angle a.

Cette plaque 1 est réalisée sur l'unique face métallisée d'un circuit imprimé 2 de faible épaisseur par rapport aux longueurs d'ondes de travail et qui est représenté en coupe sur la figure 2. La longueur d'onde λ de l'onde émise varie entre les longueurs d'ondes extrême µm et µM définies par la bande passante.This plate 1 is produced on the single metallized face of a printed circuit 2 of small thickness compared to the working wavelengths and which is shown in section in FIG. 2. The wavelength λ of the wave emitted varies between the extreme wavelengths µ m and µ M defined by the bandwidth.

Une ligne d'alimentation 3 représentée en pointillés sur la figure 1 permet d'alimenter l'antenne en excitant les éléments rayonnants à partir de points 4 et 5 qui seront définis ultérieurement. Cette ligne d'alimentation 3 est réalisée par un ruban métallisé imprimé sur un circuit imprimé 6, également de faible épaisseur. La face métallisée de ce circuit 6 se trouve du côté de la face non métallisée du circuit 2, le circuit 6 joue ainsi un rôle de protection analogue à celui d'un radome vis-à-vis de l'extérieur. Ce circuit 6 est situé dans un plan proche du plan du circuit 2 et contenant par exemple le pâle d'expansion 0 ou encore dans un plan parallèle au plan du circuit 2 et à proximité de celui-ci. Les deux circuits 2 et 6 sont séparés par un diélectrique 8 qui peut être (a la limite) le milieu air ou un nid d'abeilles.A feed line 3 shown in dotted lines in FIG. 1 makes it possible to feed the antenna by exciting the radiating elements from points 4 and 5 which will be defined later. This supply line 3 is produced by a metallized ribbon printed on a printed circuit 6, also of small thickness. The metallized face of this circuit 6 is on the side of the non-metallized face of circuit 2, circuit 6 thus plays a protective role similar to that of a radome vis-à-vis the outside. This circuit 6 is situated in a plane close to the plane of the circuit 2 and containing for example the expansion blade 0 or also in a plane parallel to the plane of the circuit 2 and close to the latter. The two circuits 2 and 6 are separated by a dielectric 8 which can be (at the limit) the air medium or a honeycomb.

La ligne 3 décrit des dents trapézoïdales se déduisant par une similitude de pôle 0 et de rapport τ, dont les côtés sont parallèles aux côtés des dents rayonnantes et passent par les milieux 4 des segments ln extrêmes de chaque dent et par les milieux 5 des segments opposés Ln. La coupure de largeur εn entre ces deux points 4 et 5 permet d'exciter les éléments rayonnants.Line 3 describes trapezoidal teeth deduced by a similarity of pole 0 and of ratio τ, the sides of which are parallel to the sides of the radiating teeth and pass through the midpoints 4 of the extreme segments l n of each tooth and through the midpoints 5 of the opposite segments L n . The cut in width ε n between these two points 4 and 5 makes it possible to excite the radiating elements.

Le circuit 2 est solidaire de la structure métallique 9 (son plan de masse) sur laquelle est plaquée l'antenne et le circuit 1 est maintenu en contact électrique avec cette structure 9 au niveau des tronçons de droites OE, et OF2 passant par les points respectivement 5 et 15. Ce contact est assuré, par exemple au moyen de vis 10 et 11 représentées sur la figure 1.The circuit 2 is integral with the metal structure 9 (its ground plane) on which the antenna is placed and the circuit 1 is maintained in electrical contact with this structure 9 at the level of the straight sections OE, and OF 2 passing through the points 5 and 15 respectively. This contact is ensured, for example by means of screws 10 and 11 shown in FIG. 1.

La coupe représentée sur la figure 3 permet de mettre en évidence la hauteur Hn séparant le plan de masse de chaque élément rayonnant.The section shown in Figure 3 highlights the height H n between the ground plane of each radiating element.

Bien entendu, les paramètres référencés avec un indice n varient en fonction de n ou n est l'indice repérant la dent, le nombre total de dents étant désigné par N (N = 5 dans le cas de la figure 1). Pour la première dent, on aura donc une longueur h1, un intervalle ε1 et une hauteur Hl.Of course, the parameters referenced with an index n vary as a function of n or n is the index identifying the tooth, the total number of teeth being designated by N (N = 5 in the case of FIG. 1). For the first tooth, there will therefore be a length h 1 , an interval ε 1 and a height H l .

Les éléments rayonnants se comportent comme des demi- doublets court-circuités à la résonance quart d'onde. Pour cela, on doit avoir la relation Hn + hn = λn/4. Chaque élément rayonnant est donc court-circuité à l'une de ses extrémités 15 à la structure métallique 9 sur laquelle l'antenne est plaquée. L'autre extrémité 4 est isolée de la structure métallique et la coupure qui en résulte est excitée par la ligne d'alimentation. L'impédance de rayonnement de la plaque court-circuitée à la résonance quart d'onde s'insere en série dans la ligne microbande 3 à l'endroit de la coupure.The radiating elements behave like half-doublets short-circuited at quarter wave resonance. For that, one must have the relation H n + h n = λ n / 4. Each radiating element is therefore short-circuited at one of its ends 15 to the metal structure 9 on which the antenna is pressed. The other end 4 is isolated from the metal structure and the resulting cut is excited by the supply line. The radiation impedance of the plate short-circuited at quarter-wave resonance is inserted in series in the microstrip line 3 at the place of the cut.

Le choix des dimensions des éléments rayonnants est effectué de telle sorte que, lorsque la ligne d'alimentation microbande 3 transmet une onde dont la fréquence est inférieure à la fréquence de resonance propre d'une dent donnée, celle-ci présente, au niveau de sa coupure, une impédance faible qui perturbe peu la transmission de la ligne.The choice of the dimensions of the radiating elements is carried out in such a way that, when the microstrip supply line 3 transmits a wave whose frequency is lower than the natural resonance frequency of a given tooth, the latter presents, at the level of its breaking, a low impedance which hardly disturbs the transmission of the line.

L'angle d'inclinaison du diagramme de rayonnement sur le plan de la structure est directement lié à la longueur kn géométrique ou électrique de la ligne d'alimentation microbande 3 comprise entre les coupures de deux sources rayonnantes adjacentes. On considère la longueur électrique lorsque la ligne se trouve en présence d'un materiau diélectrique. Il est donc aisé par construction de modifier l'angle d'inclinaison en modifiant cette longueur. La relation existant entre l'angle d'inclinaison entre le faisceau principal et le plan de la structure de l'antenne et la longueur de la ligne kn alimentant deux doublets court-circuités à la résonance quart d'onde résulte de calculs théoriques connus que l'on peut trouver dans les revues IEEE transaction dans les articles de G.DUBOST intitulés:

  • - "Propagation along two radiating coupled waveguides applications to a multimode radiating array", on Antennas and Propagation de mai 1981.
  • - "Bandwith of a low sidelobe level multimode radiating coupled waveguide array", on Antennas and Propagation 1983.
The angle of inclination of the radiation diagram on the plane of the structure is directly related to the geometric or electrical length k n of the microstrip supply line 3 between the cuts of two adjacent radiating sources. The electrical length is considered when the line is in the presence of a dielectric material. It is therefore easy by construction to modify the angle of inclination by modifying this length. The relationship between the angle of inclination between the main beam and the plane of the antenna structure and the length of the line k n feeding two doublets short-circuited at quarter wave resonance results from known theoretical calculations which can be found in the IEEE transaction journals in the articles by G.DUBOST entitled:
  • - "Propagation along two radiating coupled waveguides applications to a multimode radiating array", on Antennas and Propagation of May 1981.
  • - "Bandwith of a low sidelobe level multimode radiating coupled waveguide array", on Antennas and Propagation 1983.

Cependant une condition doit être respectée pour qu'il n'y ait pas d'aberration dans le fonctionnement. En effet, la longueur électrique Kn doit être inférieure à λn/2 afin que l'antenne ne soit pas désadaptée. Ainsi, les réflexions partielles dues aux insertions des éléments rayonnants le long de la ligne ne se cumulent pas.However, a condition must be met so that there is no aberration in operation. Indeed, the electrical length K n must be less than λ n / 2 so that the antenna is not mismatched. Thus, the partial reflections due to the insertions of the radiating elements along the line do not accumulate.

Le cas le plus faborable se présente lorsque cette longueur kn est égale à λn/4 car elle permet une compensation pratiquement idéale de toutes les réflections. Cependant, pour des raisons pratiques, une longueur intermédiarie s'impose par exemple 0,3 Àn, ce qui correspond compte tenu des autres parametres géométriques et électriques, à une impédance d'entrée bien adaptée. Pour obtenir la longueur la mieux adaptée, il est donc nécessaire que les éléments rayonnants soient intercalés.The most fabulous case is when this length k n is equal to λ n / 4 because it allows practically ideal compensation for all reflections. However, for practical reasons, an intermediate length is necessary for example 0.3 λ, which corresponds taking into account the other geometric and electrical parameters, to a well adapted input impedance. To obtain the most suitable length, it is therefore necessary that the radiating elements are inserted.

Il est évident que pour modfier la longeuur électrique de la ligne 3, on peut d'une part agir en modifiant le diélectrique 8, (sa constante diélectrique ou l'épaisseur) et d'autre part, donner une forme différente à la ligne de sorte que par exemple si on veut diminuer sa longueur géométrique elle ne suive pas rigoureusement l'axe médian de chaque plaque comme cela est représenté sur la figure 1, en passant toutefois au milieu des diverses coupures.It is obvious that to modify the electrical length of the line 3, one can on the one hand act by modifying the dielectric 8, (its dielectric constant or the thickness) and on the other hand, give a different shape to the line of so that for example if we want to reduce its geometric length it does not strictly follow the median axis of each plate as shown in Figure 1, however passing in the middle of the various cuts.

On peut également agir sur la longueur des plaques rayonnantes en plaçant un matériau diélectrique 12 dans l'espace compris entre la structure métallique 9 et la plaque métallique 1 (comportant les dents). En diminuant ainsi la longueur hn de chaque élément rayonnant, cela permet de diminuer la longueur de la ligne 3 entre deux coupures.One can also act on the length of the radiating plates by placing a dielectric material 12 in the space between the metallic structure 9 and the metallic plate 1 (comprising the teeth). By thus reducing the length h n of each radiating element, this makes it possible to reduce the length of the line 3 between two cuts.

La ligne 3 est fermée sur son impédance caractéristique au moyen d'une résistance 13 adaptée à son extrémité la plus éloignée du pôle 0. Cette résistance peut être un élément à constantes localisées ou un dipôle à constantes réparties.Line 3 is closed on its characteristic impedance by means of a resistor 13 adapted at its end furthest from pole 0. This resistor can be an element with localized constants or a dipole with distributed constants.

Quelques résultats théoriques sont donnés ci-dessous pour un choix des differents paramètres et de la bande passante, déterminés. En choisissant:

  • fm = 0,9 GHz
  • f M = 9 GHz
  • τ = 0,95
  • Figure imgb0001
    = 0,166
  • Figure imgb0002
    =0,1
  • t = 0,35
Some theoretical results are given below for a choice of different parameters and bandwidth, determined. By choosing:
  • f m = 0.9 GHz
  • f M = 9 GH z
  • τ = 0.95
  • Figure imgb0001
    = 0.166
  • Figure imgb0002
    = 0.1
  • t = 0.35

Ra impédance caractéristique de la ligne 3 égale à 150 Q et N = 50, obtient les résultats suivants:

  • L'angle d'inclinaison théorique du faisceau, c'est-à-dire l'angle entre la direction du maximum de rayonnemant et la direction perpendiculaire au plan de la structure est de 50°.
  • L'ouverture à 3dB du faisceau principal sensiblement de révolution est égale à 45°.
  • Le rapport d'ondes stationnaires de l'impédance d'entrée de l'antenne rapportée à la résistance caractéristique de la ligne est inférieur à 2 dans toute la bande 0,9 GH - 9 GHz.
R has characteristic impedance of line 3 equal to 150 Q and N = 50, obtains the following results:
  • The theoretical angle of inclination of the beam, that is to say the angle between the direction of the maximum of radiation and the direction perpendicular to the plane of the structure is 50 °.
  • The opening at 3dB of the main beam substantially of revolution is equal to 45 °.
  • The standing wave ratio of the antenna input impedance related to the characteristic resistance of the line is less than 2 in the whole 0.9 GH - 9 GHz band.

Sur la figure 4, on a représenté une variante de réalisation. L'antenne est vue en coupe comme sur la figure 2.In Figure 4, an alternative embodiment is shown. The antenna is seen in section as in Figure 2.

Dans cette variante, la ligne d'alimentation 3 est imprimée sur la face opposée du circuit 2, ce circuit comportant sur l'autre face les éléments rayonnants. C'est dans ce cas un substrat diélectrique métallisé sur ses deux faces. Cette variante est avantageuse sur le plan de l'encombrement.In this variant, the supply line 3 is printed on the opposite face of the circuit 2, this circuit comprising on the other face the radiating elements. In this case, it is a metallized dielectric substrate on its two faces. This variant is advantageous in terms of size.

La réalisation qui a été décrite est relative à une antenne plane, c'est-à-dire, à une antenne dont les éléments rayonnants ont une très faible épaisseur vis-à-vis de leur longueur et de leur largeur. Par ailleurs, cette antenne a une structure plane dans son ensemble, c'est-à-dire qu'elle peut être encastrée sur une structure métallique plane. Il est bien évident que l'invention concerne également les antennes à structure générale galbée destinées à être encastrées sur des structures métalliques galbées (du type avions). Il suffit pour cela de conformer les circuits sur lesquels sont placés les éléments de l'antenne à la forme de la structure métallique tout en respectant les conditions de fonctionne ment données dans la description.The embodiment which has been described relates to a planar antenna, that is to say, to an antenna whose radiating elements have a very small thickness with respect to their length and their width. Furthermore, this antenna has a planar structure as a whole, that is to say that it can be embedded on a planar metallic structure. It is obvious that the invention also relates to antennas with a generally curved structure intended to be built into curved metallic structures (of the aircraft type). For this, it suffices to conform the circuits on which the elements of the antenna are placed to the shape of the metal structure while respecting the operating conditions given in the description.

En conclusion, l'antenne selon l'invention a tout d'abord les avantages d'une antenne log-périodique classique, car elle a une très large bande passante. De plus, elle est facilement encastrable dans une structure métallique et ne modifie donc pas son aerodynamisme puisqu'elle est plane et que son plan de masse adapté à la réalisation peut être encastré dans la structure métallique.In conclusion, the antenna according to the invention has first of all the advantages of a conventional log-periodic antenna, since it has a very wide bandwidth. In addition, it is easily built into a metallic structure and therefore does not modify its aerodynamics since it is planar and its ground plane adapted to the embodiment can be embedded in the metallic structure.

Elle a en plus l'avantage de pouvoir rayonner suivant une direction incliné par rapport à la normale au plan de sa structure, ce qui est utile lorsque par exemple l'antenne est placée sur un avion.It also has the advantage of being able to radiate in a direction inclined with respect to the normal to the plane of its structure, which is useful when for example the antenna is placed on an airplane.

Claims (14)

1. A plane periodic antenna which can be integrated in a flat or shaped metallic structure without changing the aerodynamics of this structure, comprising a conducting plate (1) which includes radiating elements made of two series of plane teeth (DI - Dm), (Q1 - Qp), characterized in that the dimensions are derived from one another according to a homothetic similarity of the factor τ and the expansion pole 0, the teeth of one of the series being interposed between the teeth of the other series and the end (4) of a given tooth being separated from the edge (5) of the plate situated between two teeth of the other series by a predetermined interval (εn), and that a feed line (3) placed in a plane close to the plane of the plate (1) feeds the teeth from the predetermined interval (εn), and characterized by a ground plane (9) situated at a distance Hn of each tooth, which distance varies in accordance with the resonance wavelength λn of each tooth.
2. A periodic antenna according to claim 1, characterized in that the longitudinal axes of the teeth (D, - Dm), (Qi - Qp) are parallel.
3. An antenna according to any one of claims 1 or 2, characterized in that the teeth are trapezoidal in shape.
4. An antenna according to any one of claims 1 to 3, characterized in that the sum of the lengths Hn and hn should be substantially equal to Xn n/4, each tooth and its ground plane thus constituting a half pair which is short-circuited at the quarter wave-length resonance, hn being the length of a tooth.
5. An antenna according to any one of claims 1 to 4, characterized in that the two series of teeth are realised on the metal surface (1) of a first printed circuit (2) of small thickness with respect to the transmission frequency wave- lengths.
6. An antenna according to any one of claims 1 to 5, characterized in that the metal ground plane (9) situated at the height Hn of each tooth is integral with the first printed circuit (2) and is electrically connected to the metal surface (1) of this circuit (2).
7. An antenna according to claim 6, characterized in that the ground plane (9) is electrically connected to the metal surface (1) by means of screws (10, 11) spaced out over the entire plate (1).
8. An antenna according to any one of claims 1 to 7, characterized in that the space between the ground plane (9) and the plate (1) is filled with a dielectric material (12).
9. An antenna according to any one of claims 1 to 8, characterized in that the feed line (3) is a microstrip line realised on the metal surface of a second printed circuit (6) of small thickness with respect to the transmission frequency wavelengths.
10. An antenna according to claim 9, characterized in that the mefallized surface of the second printed circuit (6) is situated in a plane including the expansion pole (0) and close to the plane in which the second printed crcuit (2) is located, such that the feed line (3) is placed in the centre of the interval In and Ln defining the quarter weave-length cuts of the teeth.
11. An antenna according to claim 10, characterized in that a dielectric material (8) is placed between the first (2) and the second (6) printed circuit.
12. An antenna according to claim 5, characterized in that the feed line (3) is a microstrip line realised on the rear metallized surface of the first printed circuit (2).
13. An antenna according to any one of claims 1 to 12, characterized in that the feed line (3) is terminated by its characteristic impedance (Ra) by means of a matched impedance (13), and that the length kn of the line (3) between two cut points is smaller than λn/2, thus contributing to an antenna radiation along an inclined direction with respect to the normal to the plane (P) of this structure.
14. An antenna according to any one of claims 1 to 13, characterized in that the planes in which the radiating elements (D1 - Dm), (Q1 - Qp) and the feed line (3) are located, are shaped in such a way, that the antenna may be integrated into a metal structure which itself is shaped without modifying the aerodynamics of this structure.
EP84402523A 1983-12-13 1984-12-06 Plane periodic antenna Expired EP0145597B1 (en)

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FR8319924A FR2556510B1 (en) 1983-12-13 1983-12-13 PERIODIC PLANE ANTENNA
FR8319924 1983-12-13

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EP0145597A3 EP0145597A3 (en) 1985-07-10
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EP0145597A3 (en) 1985-07-10
DE3476496D1 (en) 1989-03-02
EP0145597A2 (en) 1985-06-19
US4652889A (en) 1987-03-24
FR2556510A1 (en) 1985-06-14
FR2556510B1 (en) 1986-08-01

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