EP1583176A1 - Reflector antenna with a 3D structure forming different waves for different frequency bands - Google Patents
Reflector antenna with a 3D structure forming different waves for different frequency bands Download PDFInfo
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- EP1583176A1 EP1583176A1 EP05290679A EP05290679A EP1583176A1 EP 1583176 A1 EP1583176 A1 EP 1583176A1 EP 05290679 A EP05290679 A EP 05290679A EP 05290679 A EP05290679 A EP 05290679A EP 1583176 A1 EP1583176 A1 EP 1583176A1
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
- H01Q19/10—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces
- H01Q19/18—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces having two or more spaced reflecting surfaces
- H01Q19/19—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces having two or more spaced reflecting surfaces comprising one main concave reflecting surface associated with an auxiliary reflecting surface
- H01Q19/195—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces having two or more spaced reflecting surfaces comprising one main concave reflecting surface associated with an auxiliary reflecting surface wherein a reflecting surface acts also as a polarisation filter or a polarising device
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
- H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
- H01Q15/0013—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective
- H01Q15/0033—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective used for beam splitting or combining, e.g. acting as a quasi-optical multiplexer
Definitions
- the invention relates to the field of reflector antennas microwaves (or RF), and more particularly the reflector antennas for transmitting and / or receiving electromagnetic waves belonging to at least two frequency bands.
- frequency band (s) a band comprising at least one frequency.
- a reflector antenna of the aforementioned type, comprises in particular a reflector responsible for reflecting the electromagnetic waves it receives either from a local source when they are destined for a remote collector, either from a remote source when they are destined for a local collector. It is recalled that an antenna may include one or more local sources, one or more local collectors or one or more sources local and one or more local collectors, possibly confused.
- Some applications such as applications spatial constraints impose specific constraints on embedded antennas.
- some telecommunications satellites are intended for transmit and receive several beams (or "brushes").
- An intermediate solution is to achieve what the skilled person calls a "colorful mosaic of sources".
- This solution consists of spread, for example on three or four transmission antennas and three or four receiving antennas, sources to be initially close, so as to free up space for each source.
- Each antenna is then dedicated to a single color or frequency. However, the number antennas remains high (it is for example equal to 6 or 8).
- the size of the reflector defines the size of the beam and his gain.
- an antenna comprising a reflector whose front face is subdivided into a first part "Central”, responsible for reflecting beams of waves at first and second frequencies, and a second "peripheral” part, surrounding the first and responsible for selectively reflecting only the frequency the lower of the two, while diffracting or out of phase Destructive as much as possible the highest frequency.
- Extensions radials of the two parts are chosen so that the electrical dimension of the reflector (in terms of number of wavelengths) is substantially the same for both frequencies, and therefore the widths of both reflected beams are substantially equal.
- R is the radius of the antenna and is used all antenna (reflector) at 20 GHz, ie R, only 2R / 3 is used at 30 GHz to obtain beams of the same size at both frequencies.
- each band has a transverse section rectangular to introduce a destructive phase shift of 180 ° between the waves reflected on the top of the bands and those reflected in the interband space.
- each band has a cross section in the form of a sawtooth so as to diffract in all directions the waves with the greatest frequency.
- the first embodiment can produce the result expected (destruction by destructive phase shift), it is imperative that the profile rectangular of the network is rigorously respected.
- the second embodiment can produce the desired result (diffraction in all directions), it is imperative that the tapered sawtooth profile (right triangle) of the network is rigorously respected.
- the technique used to make the electrical dimension of the reflector is substantially the same for both frequencies, induces a broadening of the main lobe of the antenna pattern for the larger frequencies, without specific and / or precise action on the lobes secondary (or lateral), so that the level of the latter is high, while the quality of the main beam, associated with the main lobe, is low, and that the aggregate isolation parameter (C / I) between beams of the same frequency is low.
- this technique causing the deletion or diffraction of a part of the signal, significantly reduces the energy efficiency of the antenna.
- a multifrequency reflector antenna having a reflector provided with a front face responsible for reflecting electromagnetic wave bundles belonging to at least two bands of different frequency (s).
- This antenna is characterized by the fact that the front of its reflector comprises, preferably over its entire surface, a structure defining a three-dimensional (3D) pattern with symmetry of revolution (or rotation), chosen to shape the beams so that they have radiofrequency (RF) characteristics substantially identical.
- 3D three-dimensional
- RF radiofrequency
- the beams are shaped to present characteristics substantially identical radio frequencies.
- the three-dimensional pattern may consist of concentric bands protruding or recessed having radius leading edges (or curvature) of between about 1 mm and about 200 mm, and preferably between about 10 mm and about 40 mm.
- each concentric band can extend over a chosen width, fixed or variable, and on a chosen height, fixed or variable, and the different concentric bands can be spaced any of the others of a constant or variable step.
- the antenna When the antenna is dedicated to transmitting and receiving, it comprises at least one source delivering a first wave beam electromagnetic transmitters belonging to a first band of frequency (s), and at least one collector, possibly confused with the source, and responsible for collecting a second beam, belonging to a second frequency band (s).
- the reflector is arranged way of transmitting the first beam from the source, after reflection and formatting by its front, and to receive a beam of electromagnetic waves belonging to the second band of frequency (s), to transmit it to the collector in the form of the second beam after reflection and shaping by its front face.
- the antenna When the antenna is dedicated to the only transmission, it includes at least one source of beams to be transmitted.
- the reflector is arranged to transmit the beams of waves electromagnetic devices belonging to at least two frequency bands different and from the source, after reflection and formatting by his front face.
- the three-dimensional pattern is chosen according to the diagram transmission of the source.
- the antenna When the antenna is dedicated to reception only, it includes less a beam collector.
- the reflector is arranged to receive the beams of electromagnetic waves belonging to at least two frequency bands, to transmit them to the collector after reflection and formatting by its front.
- the structure can either be attached to the front face, or integral part of the front face.
- the invention is particularly well adapted, although in a non in the field of space telecommunications, particularly in the field of the Ka band (17.7 to 31 GHz).
- the object of the invention is to allow the shaping of beams by a reflector of a multifrequency antenna, possibly multibeam type preference.
- the invention relates to all types of reflector antenna multi-frequencies, on-board or terrestrial, working in the field of microwaves, especially those above Gigahertz (GHz), and above particularly those belonging to the Ka band (17.7 GHz to 31 GHz).
- GHz Gigahertz
- the antennas are loaded on telecommunications satellites and operate in the Ka band.
- the AR reflector antenna is, for example, exclusively dedicated to the transmission of electromagnetic waves in two bands of frequencies centered on the 20 GHz and 30 GHz values.
- the following is taken to mean the first frequency band at its central value 20 GHz and the second frequency band at its value central 30 GHz.
- the antenna could be dedicated either exclusively to the reception of electromagnetic wave beams belonging to at least two frequency bands, or both to the transmission of electromagnetic waves having at least one frequency and to receiving electromagnetic waves having at least one other frequency.
- the invention relates to at least two-band frequency applications.
- the AR multifrequency reflecting antenna illustrated comprises a source S feeding a reflector R in electromagnetic waves having the first (20 GHz) and second (30 GHz) frequencies. Any type of efficient source known to those skilled in the art can be used for this purpose.
- the reflector R comprises a rigid shell, here secured to an arm deployment or the structure of the spacecraft (here a satellite).
- This rigid shell which will be discussed later, has a front face FA intended to reflect the electromagnetic waves, delivered by the source S according to his transmission diagrams, in the form of first and second beams directed to the same land area.
- the front face FA of the reflector R comprises a ST structure which defines a three-dimensional (3D) pattern with symmetry of revolution (or rotation). This 3D pattern is chosen to shape the two beams so that they exhibit radio frequency (RF) characteristics substantially identical.
- 3D three-dimensional
- radio frequency characteristics the electromagnetic characteristics, such as the width of beam (or beam width), which characterizes the directivity of the antenna, and / or the electromagnetic radiation diagram, such as the energy distribution in a transverse plane (main lobe and lobes side (or lateral)), as well as eventually the weakening (or “roll” off ").
- beams of 20 and 30 GHz may have a width between about 0.5 ° and 1 ° (which corresponds to a large antenna) directivity).
- the diameter of the AR reflector antenna is included between about 1500 mm and about 1600 mm, for example about 1560 mm.
- the invention also applies to more beams wide, even much wider, but also thinner.
- the 3D pattern is calculated using a computer, taking into account the geometric characteristics desired for the two beams.
- the calculation can also take into account the transmission diagrams of source S for each of the first (here 20 GHz) and second (here 30 GHz) frequencies. This makes it possible, advantageously, to correct at least partially the imperfections of the transmission diagrams (but also those of reception when the antenna operates in reception or transmission / reception), as well as improvements not taken into account.
- the calculation of the 3D pattern allowing the shaping of the two beams can be done in two steps: a first step of solving a two-dimensional (2D) antenna illumination problem, then a second step of generalizing the problem to a 3D illumination.
- C T C S * C R , where C T is the total current distribution (i.e., the inverse transform of the desired far field ), C S is the contribution of the source S in amplitude and phase at the reflector R, and C R is the contribution of the reflector R to the amplitude and the phase of the total current (for example the induced phase change by a change of shape of the reflector).
- C S C T / C S.
- This function C R for example has the form of a truncated cosine having a maximum in the center of the reflector, then decreasing, then passing through zero, then becoming negative.
- the 30 GHz wave meets a 3 ⁇ / 4 section, it is reflected and is out of phase with 3 ⁇ / 2 or 180 ° compared to the neighboring section, if although it is in phase with the neighboring section.
- the fineness or precision of the integral is proportional to the width sections.
- a simple three-dimensional generalization (by first-order symmetry of revolution) then makes it possible to obtain the shape of the 3D pattern (and therefore of the reflector R) which makes it possible to obtain the desired total current distribution C T.
- the main purpose of the 3D pattern is thus to modify the phase diagram of the reflector R, or in other words to introduce an offset pattern, with respect to a reference parabola, with symmetry of revolution (or rotation), relative to the standard form of said reflector R, for example parabolic.
- the 3D pattern is preferably in the form of concentric strips BC (or “Crowns”) 3D protruding or recessed. It is important to note that these concentric bands BC may, in some situations, not be continuous 360 °. They may indeed have areas in which they are interrupted. However, the shape of a band concentric BC, that is to say its cross section, is constant (outside possible interruption zones).
- FIGS. 6, Three partial examples of 3D patterns are illustrated in FIGS. 6, in cross-sectional views.
- the illustrated example FIG. 4 corresponds to a projecting symmetrical 3D pattern, in which the concentric bands BC are all identical (width d1 constant and height h constant) and spaced at a constant pitch d2.
- the width d1 and step d2 can be constant, and the height h can vary from one concentric band BC to another.
- FIG. 5 corresponds to a protruding 3D pattern, in which certain concentric bands BC have shapes different and irregular spacings.
- a band concentric BC may have a width d1
- another band concentric BC may have a width d3
- yet another band concentric BC may have a width d5.
- spacing between neighboring concentric bands is preferentially variable (here, the spacing d2 is smaller than the spacing d4), and the height h varies preferentially from one concentric band BC to the other.
- the example illustrated in FIG. 6 also corresponds to a 3D pattern in which all concentric bands BC have different shapes and irregular spacings.
- a band concentric BC may have a width d2
- another band concentric BC may have a width d4
- yet another band concentric BC may have a width d6.
- spacing between neighboring concentric bands varies (here d1d3d5d7), and the height h varies preferentially from one concentric band BC to another.
- the height h is equal to about 7.5 mm, and the widths and spacings di are between about 80 mm and 400 mm.
- the bands concentric BC of the 3D pattern preferentially have edges BA rounded nose with radius of gyration (or curvature) between about 1 mm and about 200 mm, and more preferably between about 10 mm and about 40 mm.
- a control thermal reflector R can be classically obtained by means of a radome placed on its front face FA and thermal insulation, in technology SLI (for Single Layer Insulation) or in MLI technology (for "Multiple Layer Insulation”) multiple), for example a Kapton leaf or laminate, placed on its face back. Alternatively, one can only provide a thermal insulation on the back side.
- FIG. 8 shows in a cross-sectional view, an example of a 3D pattern portion in which the concentric strips BC have a transverse section of the type of that illustrated in FIG. i.e. with rounded BA leading edges.
- the 3D pattern extends over the entire front face FA of the reflector R, as shown in the diagram of Figure 9, but it can also extend only on part of the front face FA of the reflector R, and in this case there is little or no concentric band BC in the zone as shown in the diagram in Figure 10.
- These two diagrams represent, in a planar projection, the positions of the different BC concentric bands (which are here transformed into lines of projection) relative to the center of the reflector R.
- the axis of The abscissa is graduated from 1 to 201, and materializes 200 points between center and the edge of the reflector R.
- the ordinate axis shows the height h (in mm) concentric strips BC, for example about 7.5 mm.
- the ST structure, defining the 3D pattern can be either reported on the front face FA of the reflector R, be an integral part of this one.
- the structure ST consists of several BC concentric band groups reported on the front face FA of the reflector shell R. In this case, each group is made using a specific mold, then reported, by example by gluing, on the front face FA of the hull of the reflector R.
- the ST structure is part of integral part of the reflector shell R.
- the mold allowing the elaboration of the shell, therefore comprises the negative imprint of the ST structure.
- the 3D pattern is therefore manufactured at the same time as the shell, by cooking, by example at 180 ° C (the temperature of course depends on the type of resin used).
- Such molds can be made using technology machining so-called 5D.
- the hull can be made with a spacer of constant thickness or not.
- the ST structure also makes part of the hull of the reflector R.
- the front face FA and the back AR have the 3D pattern.
- This embodiment of the Reflector shell R facilitates its development, especially in series by molding or by hot stamping (between a punch and a counterpunch), or by any other technique. It is important to note that only the front face FA is functional.
- the reflector according to the invention can be installed in the same way as any reflector traditional.
- the reflector R in a view in cross-section, the reflector R, of cellular type in so-called “Thick shell", sandwich concept, is mounted on an arm of BD deployment connected to a satellite platform.
- the reflector R cell type technology called “shell thin stiffened ", sandwich concept, is mounted on a rigid structure SR of satellite, for example by means of L-shaped clips.
- a rigid structure SR of satellite for example by means of L-shaped clips.
- the reflector in a sectional view transverse, is mounted on a rigid structure So-called monolithic SR, consisting of a single element or an assembly monolithic elements, for example by means of L-shaped clips, possibly glued.
- monolithic SR consisting of a single element or an assembly monolithic elements, for example by means of L-shaped clips, possibly glued.
- Such an arrangement also offers good holding mechanical and good dimensional stability.
- the multifrequency reflector antenna according to the invention offers many advantages compared to antennas of the prior art.
- the invention is not limited to antenna embodiments multifrequency reflector described above, only as an example, but it encompasses all the variants that can be envisaged by those skilled in the art in the scope of the claims below.
- the invention relates to any reflector antenna provided with a structure defining a three-dimensional pattern with symmetry of revolution and with rounded and "soft" leading edges.
Abstract
Description
L'invention concerne le domaine des antennes réflecteur hyperfréquences (ou RF), et plus particulièrement les antennes réflecteur destinées à la transmission et/ou la réception d'ondes électromagnétiques appartenant à au moins deux bandes de fréquence(s).The invention relates to the field of reflector antennas microwaves (or RF), and more particularly the reflector antennas for transmitting and / or receiving electromagnetic waves belonging to at least two frequency bands.
On entend ici par bande de fréquence(s), une bande comportant au moins une fréquence.Here is meant by frequency band (s), a band comprising at least one frequency.
Une antenne réflecteur, du type précité, comporte notamment un réflecteur chargé de réfléchir les ondes électromagnétiques qu'il reçoit soit d'une source locale lorsqu'elles sont destinées à un collecteur distant, soit d'une source distante lorsqu'elles sont destinées à un collecteur local. Il est rappelé qu'une antenne peut comporter soit une ou plusieurs sources locales, soit un ou plusieurs collecteurs locaux, soit encore une ou plusieurs sources locales et un ou plusieurs collecteurs locaux, éventuellement confondus.A reflector antenna, of the aforementioned type, comprises in particular a reflector responsible for reflecting the electromagnetic waves it receives either from a local source when they are destined for a remote collector, either from a remote source when they are destined for a local collector. It is recalled that an antenna may include one or more local sources, one or more local collectors or one or more sources local and one or more local collectors, possibly confused.
Certaines applications, comme par exemple des applications spatiales, imposent des contraintes spécifiques aux antennes embarquées. Par exemple, certains satellites de télécommunications sont destinés à transmettre et à recevoir plusieurs faisceaux (ou « pinceaux »). Pour atteindre cet objectif, il a été initialement proposé de mettre en parallèle plusieurs antennes monofréquence et/ou monofaisceau, dédiées chacune à la transmission ou à la réception. Cette solution simple est inefficace. En effet, pour fonctionner selon 50 faisceaux de transmission et 50 faisceaux de réception, avec un faisceau par antenne, il faut utiliser 100 antennes.Some applications, such as applications spatial constraints impose specific constraints on embedded antennas. For example, some telecommunications satellites are intended for transmit and receive several beams (or "brushes"). To reach objective, it was initially proposed to compare several single-frequency and / or single-beam antennas, each dedicated to the transmission or reception. This simple solution is inefficient. Indeed, to operate according to 50 transmission beams and 50 beams of receiving, with a beam per antenna, it is necessary to use 100 antennas.
Certes il est en théorie possible de regrouper tous les faisceaux de transmission sur une antenne de transmission et tous les faisceaux de réception sur une antenne de réception. Mais, cette solution est impossible à mettre en oeuvre en pratique car elle ne permet pas de loger toutes les sources (de transmission ou de réception) les unes à côté des autres sur des antennes de taille et de poids compatibles avec des applications spatiales.Certainly it is theoretically possible to group all the beams of transmission on a transmission antenna and all the beams of receiving on a receiving antenna. But, this solution is impossible to implement in practice because it does not accommodate all sources (transmission or reception) next to each other on antennas of size and weight compatible with space applications.
Une solution intermédiaire consiste à réaliser ce que l'homme de l'art appelle une « mosaïque colorée de sources ». Cette solution consiste à répartir, par exemple sur trois ou quatre antennes de transmission et trois ou quatre antennes de réception, des sources devant être initialement voisines, de manière à libérer de la place pour chaque source. Chaque antenne est alors dédiée à une unique couleur ou fréquence. Cependant, le nombre d'antennes demeure encore élevé (il est par exemple égal à 6 ou 8).An intermediate solution is to achieve what the skilled person calls a "colorful mosaic of sources". This solution consists of spread, for example on three or four transmission antennas and three or four receiving antennas, sources to be initially close, so as to free up space for each source. Each antenna is then dedicated to a single color or frequency. However, the number antennas remains high (it is for example equal to 6 or 8).
Par ailleurs, dans certaines applications, comme par exemple les applications multimédia en bande Ka, qui nécessitent des antennes multifaisceaux et/ou multifréquences offrant une grande directivité selon plusieurs fréquences différentes, on a fréquemment besoin de nombreux faisceaux (par exemple 50) relativement fins, et donc à fort gain, pour chacune des fréquences, et donc de sources et/ou de collecteurs spécifiques. Or, la conception de telles sources et de tels collecteurs est particulièrement difficile, voire impossible, compte tenu des contraintes rencontrées.Moreover, in certain applications, such as for example Ka-band multimedia applications, which require antennas multi-beam and / or multi-frequency with high directivity different frequencies, we often need many beams (for example 50) relatively fine, and therefore at high gain, for each of the frequencies, and therefore of specific sources and / or collectors. However, the design of such sources and collectors is particularly difficult, if not impossible, given the constraints encountered.
Il est rappelé que la taille du réflecteur définit la taille du faisceau et son gain. Dans une bonne approximation la largeur () d'un faisceau à -3 dB est en effet égale à 65 fois la longueur d'onde λ (en millimètre) des ondes à transmettre divisée par le diamètre D (en millimètre) de l'antenne, soit = 65λ/D. Par conséquent, en présence d'une unique antenne et d'ondes présentant deux fréquences sensiblement différentes, comme par exemple 20 et 30 GHz, la largeur du faisceau de 30 GHz est plus étroite que la largeur du faisceau de 20 GHZ, du fait que la fréquence f (en GHz) et la longueur d'onde λ (en mm) sont liées par la relation λ = 300/f. Les zones qui reçoivent, ou d'où proviennent, les deux faisceaux transmis sont alors (très) différentes. De même, la zone d'où provient l'un des deux faisceaux ne correspond pas à la zone qui reçoit l'autre faisceau. Cela représente un réel inconvénient.It is recalled that the size of the reflector defines the size of the beam and his gain. In a good approximation the width () of a beam at -3 dB is indeed equal to 65 times the wavelength λ (in millimeters) of the waves at transmit divided by the diameter D (in millimeters) of the antenna, ie = 65λ / D. Therefore, in the presence of a single antenna and waves having two substantially different frequencies, such as, for example, and 30 GHz, the beam width of 30 GHz is narrower than the width of the beam of 20 GHZ, because the frequency f (in GHz) and the wavelength λ (in mm) are linked by the relation λ = 300 / f. Areas that receive, or where come, the two transmitted beams are then (very) different. Of the zone from which one of the two beams originates does not correspond to the area that receives the other beam. This represents a real disadvantage.
Afin de tenter de remédier à cet inconvénient, il a été proposé, notamment dans le document brevet EP 1 083 625, une antenne comportant un réflecteur dont la face avant est subdivisée en une première partie « centrale », chargée de réfléchir des faisceaux d'ondes à des première et seconde fréquences, et une seconde partie « périphérique », entourant la première et chargée de ne réfléchir de façon sélective que la fréquence la moins élevée des deux, tout en diffractant ou en déphasant de façon destructive le plus possible la fréquence la plus élevée. Les extensions radiales des deux parties sont choisies de sorte que la dimension électrique du réflecteur (en terme de nombre de longueurs d'onde) soit sensiblement la même pour les deux fréquences, et par conséquent que les largeurs des deux faisceaux réfléchis soient sensiblement égales. Par exemple, dans le cas de faisceaux de 20 et 30 GHz, si R est le rayon de l'antenne et que l'on utilise toute l'antenne (réflecteur) à 20 GHz, c'est-à-dire R, on utilise seulement 2R/3 à 30 GHz pour obtenir des faisceaux de même taille aux deux fréquences.In an attempt to remedy this drawback, it has been proposed, especially in patent document EP 1 083 625, an antenna comprising a reflector whose front face is subdivided into a first part "Central", responsible for reflecting beams of waves at first and second frequencies, and a second "peripheral" part, surrounding the first and responsible for selectively reflecting only the frequency the lower of the two, while diffracting or out of phase Destructive as much as possible the highest frequency. Extensions radials of the two parts are chosen so that the electrical dimension of the reflector (in terms of number of wavelengths) is substantially the same for both frequencies, and therefore the widths of both reflected beams are substantially equal. For example, in the case of beams of 20 and 30 GHz, if R is the radius of the antenna and is used all antenna (reflector) at 20 GHz, ie R, only 2R / 3 is used at 30 GHz to obtain beams of the same size at both frequencies.
Afin d'empêcher que les ondes présentant la plus grande fréquence ne soient réfléchies par la seconde partie de l'antenne, cette dernière comprend un réseau de bandes concentriques, en saillie ou en creux, présentant des dimensions identiques et de pas constant. Dans un premier mode de réalisation, chaque bande présente une section transverse rectangulaire de manière à introduire un déphasage destructif de 180° entre les ondes réfléchies sur le sommet des bandes et celles réfléchies dans l'espace interbandes. Dans un second mode de réalisation, chaque bande présente une section transverse en forme de dent de scie de manière à diffracter dans toutes les directions les ondes présentant la plus grande fréquence.To prevent waves with the highest frequency reflected by the second part of the antenna, the latter includes a network of concentric bands, protruding or recessed, having identical dimensions and constant pitch. Initially embodiment, each band has a transverse section rectangular to introduce a destructive phase shift of 180 ° between the waves reflected on the top of the bands and those reflected in the interband space. In a second embodiment, each band has a cross section in the form of a sawtooth so as to diffract in all directions the waves with the greatest frequency.
Pour que le premier mode de réalisation puisse produire le résultat escompté (suppression par déphasage destructif), il est impératif que le profil rectangulaire du réseau soit rigoureusement respecté. De même, pour que le second mode de réalisation puisse produire le résultat escompté (diffraction dans toutes les directions), il est impératif que le profil en dent de scie effilée (triangle rectangle) du réseau soit rigoureusement respecté.So that the first embodiment can produce the result expected (destruction by destructive phase shift), it is imperative that the profile rectangular of the network is rigorously respected. Similarly, for the second embodiment can produce the desired result (diffraction in all directions), it is imperative that the tapered sawtooth profile (right triangle) of the network is rigorously respected.
De tels profils abruptes peuvent être obtenus dans des matériaux métalliques (typiquement de densité supérieure à 2,7) tels que l'aluminium, ou l'acier, ou encore un alliage. Mais, il est notablement plus difficile de les obtenir à l'aide des matériaux couramment utilisés dans les applications spatiales, comme par exemple les matériaux composites fibres de carbone /résine organique ou autre (par exemple le CFRP pour « Carbon Fiber Reinforced Plastics »). Par conséquent, la solution proposée dans le document brevet précité peut certes être mise en oeuvre dans le cas d'une application terrestre, mais pas dans le cas d'une application spatiale ou lorsque la masse est pénalisante pour le reste d'une mission.Such steep profiles can be obtained in materials metal (typically with a density greater than 2.7) such as aluminum, or steel, or an alloy. But, it is noticeably more difficult to get using materials commonly used in applications such as composite carbon fiber / resin materials organic or otherwise (eg CFRP for "Carbon Fiber Reinforced Plastics "). Therefore, the solution proposed in patent document can certainly be implemented in the case of a terrestrial application, but not in the case of a space application or when the mass is penalizing for the rest of a mission.
En outre, la technique, utilisée pour que la dimension électrique du réflecteur soit sensiblement la même pour les deux fréquences, induit un élargissement du lobe principal du diagramme d'antenne pour la plus grande des fréquences, sans action spécifique et/ou précise sur les lobes secondaires (ou latéraux), si bien que le niveau de ces derniers est élevé, tandis que la qualité du faisceau principal, associé au lobe principal, est faible, et que le paramètre d'isolation agrégée (C/I) entre faisceaux de même fréquence est faible.In addition, the technique used to make the electrical dimension of the reflector is substantially the same for both frequencies, induces a broadening of the main lobe of the antenna pattern for the larger frequencies, without specific and / or precise action on the lobes secondary (or lateral), so that the level of the latter is high, while the quality of the main beam, associated with the main lobe, is low, and that the aggregate isolation parameter (C / I) between beams of the same frequency is low.
Par ailleurs, cette technique provoquant la suppression ou la diffraction d'une partie du signal, réduit sensiblement l'efficacité énergétique de l'antenne.Moreover, this technique causing the deletion or diffraction of a part of the signal, significantly reduces the energy efficiency of the antenna.
Enfin, cette technique ne prend pas en compte le diagramme de transmission de la (ou des) source(s) qui comporte généralement des imperfections qui demeurent de ce fait non corrigées, ou bien des améliorations non prises en compte.Finally, this technique does not take into account the transmission of the source (s) which usually imperfections that remain unadjusted, or improvements not taken into account.
Aucune antenne réflecteur connue n'apportant une entière satisfaction, l'invention a donc pour but d'améliorer la situation.No known reflector antenna bringing a whole satisfaction, the invention therefore aims to improve the situation.
Elle propose à cet effet une antenne réflecteur multifréquences comportant un réflecteur muni d'une face avant chargée de réfléchir des faisceaux d'ondes électromagnétiques appartenant à au moins deux bandes de fréquence(s) différentes.It proposes for this purpose a multifrequency reflector antenna having a reflector provided with a front face responsible for reflecting electromagnetic wave bundles belonging to at least two bands of different frequency (s).
Cette antenne se caractérise par le fait que la face avant de son réflecteur comporte, de préférence sur toute sa surface, une structure définissant un motif tridimensionnel (3D) à symétrie de révolution (ou de rotation), choisi de manière à mettre en forme les faisceaux de sorte qu'ils présentent des caractéristiques radiofréquences (RF) sensiblement identiques.This antenna is characterized by the fact that the front of its reflector comprises, preferably over its entire surface, a structure defining a three-dimensional (3D) pattern with symmetry of revolution (or rotation), chosen to shape the beams so that they have radiofrequency (RF) characteristics substantially identical.
Ainsi, contrairement à la technique antérieure dans laquelle une partie du signal est supprimée, soit par déphasage destructif, soit par diffraction, ici les faisceaux sont mis en forme afin de présenter des caractéristiques radiofréquences sensiblement identiques.Thus, unlike the prior art in which a part the signal is suppressed, either by destructive phase shift or by diffraction, here the beams are shaped to present characteristics substantially identical radio frequencies.
Le motif tridimensionnel peut être constitué de bandes concentriques en saillie ou en creux comportant des bords d'attaque à rayon de giration (ou de courbure) compris entre environ 1 mm et environ 200 mm, et préférentiellement entre environ 10 mm et environ 40 mm.The three-dimensional pattern may consist of concentric bands protruding or recessed having radius leading edges (or curvature) of between about 1 mm and about 200 mm, and preferably between about 10 mm and about 40 mm.
Par ailleurs, chaque bande concentrique peut s'étendre sur une largeur choisie, fixe ou variable, et sur une hauteur choisie, fixe ou variable, et les différentes bandes concentriques peuvent être espacées les unes des autres d'un pas constant ou variable.Moreover, each concentric band can extend over a chosen width, fixed or variable, and on a chosen height, fixed or variable, and the different concentric bands can be spaced any of the others of a constant or variable step.
Lorsque l'antenne est dédiée à la transmission et à la réception, elle comprend au moins une source délivrant un premier faisceau d'ondes électromagnétiques à transmettre, appartenant à une première bande de fréquence(s), et au moins un collecteur, éventuellement confondu avec la source, et chargé de collecter un second faisceau, appartenant à une seconde bande de fréquence(s). Dans ce cas, le réflecteur est agencé de manière à transmettre le premier faisceau provenant de la source, après réflexion et mise en forme par sa face avant, et à recevoir un faisceau d'ondes électromagnétiques appartenant à la seconde bande de fréquence(s), pour le transmettre au collecteur sous la forme du second faisceau après réflexion et mise en forme par sa face avant.When the antenna is dedicated to transmitting and receiving, it comprises at least one source delivering a first wave beam electromagnetic transmitters belonging to a first band of frequency (s), and at least one collector, possibly confused with the source, and responsible for collecting a second beam, belonging to a second frequency band (s). In this case, the reflector is arranged way of transmitting the first beam from the source, after reflection and formatting by its front, and to receive a beam of electromagnetic waves belonging to the second band of frequency (s), to transmit it to the collector in the form of the second beam after reflection and shaping by its front face.
Lorsque l'antenne est dédiée à la seule transmission, elle comprend au moins une source de faisceaux à transmettre. Dans ce cas, le réflecteur est agencé de manière à transmettre les faisceaux d'ondes électromagnétiques appartenant à au moins deux bandes de fréquence(s) différentes et provenant de la source, après réflexion et mise en forme par sa face avant.When the antenna is dedicated to the only transmission, it includes at least one source of beams to be transmitted. In this case, the reflector is arranged to transmit the beams of waves electromagnetic devices belonging to at least two frequency bands different and from the source, after reflection and formatting by his front face.
Dans les deux modes de réalisation d'antenne qui précèdent, il est avantageux que le motif tridimensionnel soit choisi en fonction du diagramme de transmission de la source.In the two antenna embodiments that precede, it is advantageous that the three-dimensional pattern is chosen according to the diagram transmission of the source.
Lorsque l'antenne est dédiée à la seule réception, elle comprend au moins un collecteur de faisceaux. Dans ce cas, le réflecteur est agencé de manière à recevoir les faisceaux d'ondes électromagnétiques appartenant à au moins deux bandes de fréquence(s), pour les transmettre au collecteur après réflexion et mise en forme par sa face avant.When the antenna is dedicated to reception only, it includes less a beam collector. In this case, the reflector is arranged to receive the beams of electromagnetic waves belonging to at least two frequency bands, to transmit them to the collector after reflection and formatting by its front.
Enfin, la structure peut soit être rapportée sur la face avant, soit faire partie intégrante de la face avant.Finally, the structure can either be attached to the front face, or integral part of the front face.
L'invention est particulièrement bien adaptée, bien que de façon non exclusive, au domaine des télécommunications spatiales, en particulier dans la bande Ka (17,7 à 31 GHz).The invention is particularly well adapted, although in a non in the field of space telecommunications, particularly in the field of the Ka band (17.7 to 31 GHz).
D'autres caractéristiques et avantages de l'invention apparaítront à l'examen de la description détaillée ci-après, et des dessins annexés, sur lesquels :
- la figure 1 illustre de façon schématique, dans une vue en coupe transversale, un exemple de réalisation d'une antenne réflecteur multifréquences selon l'invention, dédiée à la transmission,
- la figure 2 illustre un exemple de distribution de courant total (CT en unité arbitraire) en fonction du rayon du réflecteur (en unité arbitraire),
- la figure 3 illustre un exemple de surface ou motif de décalage par rapport à une parabole de référence, la barre placée à droite du diagramme matérialisant l'écart par rapport à la parabole de référence en fonction du niveau de gris,
- la figure 4 illustre de façon très schématique, dans une vue en coupe transversale, un premier exemple de réalisation d'une structure de mise en forme de faisceaux, de type symétrique, en saillie,
- la figure 5 illustre de façon très schématique, dans une vue en coupe transversale, un deuxième exemple de réalisation d'une structure de mise en forme de faisceaux, à espacements irréguliers de bandes concentriques en saillie,
- la figure 6 illustre de façon très schématique, dans une vue en coupe transversale, un troisième exemple de réalisation d'une structure de mise en forme de faisceaux, à espacements irréguliers de bandes concentriques en creux,
- la figure 7 illustre de façon très schématique, dans une vue en coupe transversale, une bande concentrique d'une structure de mise en forme de faisceaux,
- la figure 8 illustre de façon schématique, dans une vue en coupe transversale, un quatrième exemple de réalisation d'une partie d'une structure de mise en forme de faisceaux, à espacements irréguliers de bandes concentriques du type de celle illustrée sur la figure 7,
- la figure 9 illustre de façon schématique, dans une vue du dessus, un premier exemple de réalisation d'une projection planaire d'une partie d'une structure de mise en forme de faisceaux, à espacements irréguliers de bandes concentriques,
- la figure 10 illustre de façon schématique, dans une vue du dessus, un second exemple de réalisation d'une projection planaire d'une partie d'une structure de mise en forme de faisceaux, à espacements irréguliers de bandes concentriques,
- la figure 11 illustre de façon schématique, dans une vue en coupe transversale, un premier exemple de réalisation d'une partie d'un réflecteur équipé d'une structure rapportée de mise en forme de faisceaux,
- la figure 12 illustre de façon schématique, dans une vue en coupe transversale, un deuxième exemple de réalisation d'une partie d'un réflecteur comportant une structure de mise en forme de faisceaux réalisée par moulage en creux de sa face avant,
- la figure 13 illustre de façon schématique, dans une vue en coupe transversale, un troisième exemple de réalisation d'une partie d'un réflecteur comportant une structure de mise en forme de faisceaux réalisée par moulage en creux de sa face avant et moulage en saillie de sa face arrière,
- la figure 14 illustre de façon schématique, dans une vue en coupe transversale, un réflecteur cellulaire en technologie dite « coque épaisse », de type sandwich, similaire à celui de la figure 11, monté sur un bras de déploiement relié lui-même à une plateforme de satellite,
- la figure 15 illustre de façon schématique, dans une vue en coupe transversale, un réflecteur cellulaire en technologie dite « coque mince raidie », de type sandwich, monté sur une structure rigide de support d'un satellite, et
- la figure 16 illustre de façon schématique, dans une vue en coupe transversale, un réflecteur à coque ultrafine, monté sur une structure rigide de support constituée à partir d'éléments monolithiques assemblés.
- FIG. 1 schematically illustrates, in a cross-sectional view, an exemplary embodiment of a multifrequency reflector antenna according to the invention, dedicated to transmission,
- FIG. 2 illustrates an example of total current distribution (C T in arbitrary unit) as a function of the radius of the reflector (in arbitrary unit),
- FIG. 3 illustrates an example of a surface or offset pattern relative to a reference parabola, the bar placed on the right of the diagram showing the deviation from the reference parabola as a function of the gray level,
- FIG. 4 very schematically illustrates, in a cross-sectional view, a first exemplary embodiment of a beam-forming structure, of symmetrical, protruding type,
- FIG. 5 very schematically illustrates, in a cross-sectional view, a second exemplary embodiment of a beam shaping structure, with irregular spacings of projecting concentric strips,
- FIG. 6 very schematically illustrates, in a cross-sectional view, a third exemplary embodiment of a beam shaping structure, with irregular spacings of hollow concentric strips,
- FIG. 7 very schematically illustrates, in a cross-sectional view, a concentric strip of a beam shaping structure,
- FIG. 8 schematically illustrates, in a cross-sectional view, a fourth embodiment of a portion of a beam-shaping structure, with irregular spacings of concentric strips of the type of that illustrated in FIG. 7 ,
- FIG. 9 schematically illustrates, in a view from above, a first exemplary embodiment of a planar projection of a portion of a beam shaping structure, with irregular spacings of concentric strips,
- FIG. 10 schematically illustrates, in a view from above, a second exemplary embodiment of a planar projection of a portion of a beam shaping structure, with irregular spacings of concentric strips,
- FIG. 11 schematically illustrates, in a cross-sectional view, a first exemplary embodiment of a portion of a reflector equipped with an attached beam shaping structure,
- FIG. 12 schematically illustrates, in a cross-sectional view, a second exemplary embodiment of a portion of a reflector comprising a beam forming structure made by hollow molding of its front face,
- FIG. 13 schematically illustrates, in a cross-sectional view, a third exemplary embodiment of a portion of a reflector comprising a beam-shaping structure made by hollow molding of its front face and projecting molding. from its back side,
- FIG. 14 schematically illustrates, in a cross-sectional view, a cell-type "thick-shell" type cellular reflector, similar to that of FIG. 11, mounted on a deployment arm itself connected to a satellite platform,
- FIG. 15 schematically illustrates, in a cross-sectional view, a cellular reflector in the so-called "sandwiched thin shell" type technology, mounted on a rigid support structure of a satellite, and
- FIG. 16 schematically illustrates, in a cross-sectional view, an ultra-thin shell reflector mounted on a rigid support structure made from assembled monolithic elements.
Les dessins annexés pourront non seulement servir à compléter l'invention, mais aussi contribuer à sa définition, le cas échéant.The accompanying drawings may not only serve to supplement the invention, but also contribute to its definition, if necessary.
L'invention a pour objet de permettre la mise en forme de faisceaux par un réflecteur d'une antenne multifréquences, éventuellement et de préférence de type multifaisceaux.The object of the invention is to allow the shaping of beams by a reflector of a multifrequency antenna, possibly multibeam type preference.
L'invention concerne tous les types d'antenne réflecteur multifréquences, embarqués ou terrestres, travaillant dans le domaine des hyperfréquences, en particulier celles supérieures au gigahertz (GHz), et plus particulièrement celles appartenant à la bande Ka (17,7 GHz à 31 GHz).The invention relates to all types of reflector antenna multi-frequencies, on-board or terrestrial, working in the field of microwaves, especially those above Gigahertz (GHz), and above particularly those belonging to the Ka band (17.7 GHz to 31 GHz).
Dans la description qui suit, on considère, à titre d'exemple illustratif, que les antennes sont embarquées sur des satellites de télécommunications et fonctionnent dans la bande Ka.In the description which follows, it is considered, by way of illustrative example, that the antennas are loaded on telecommunications satellites and operate in the Ka band.
On se réfère tout d'abord à la figure 1 pour décrire un exemple de
réalisation d'une antenne réflecteur multifréquences AR, selon l'invention.
Dans cet exemple, l'antenne à réflecteur AR est, par exemple, exclusivement
dédiée à la transmission d'ondes électromagnétiques selon deux bandes de
fréquences centrées sur les valeurs 20 GHz et 30 GHz. Afin de simplifier la
description, on assimilera dans ce qui suit la première bande de fréquences à
sa valeur centrale 20 GHz et la seconde bande de fréquences à sa valeur
centrale 30 GHz.We first refer to Figure 1 to describe an example of
realization of an AR multifrequency reflector antenna, according to the invention.
In this example, the AR reflector antenna is, for example, exclusively
dedicated to the transmission of electromagnetic waves in two bands of
frequencies centered on the 20 GHz and 30 GHz values. In order to simplify
description, the following is taken to mean the first frequency band at
its
Bien entendu, l'antenne pourrait être dédiée soit exclusivement à la
réception de faisceaux d'ondes électromagnétiques appartenant à au moins
deux bandes de fréquence(s), soit à la fois à la transmission d'ondes
électromagnétiques présentant au moins une fréquence et à la réception
d'ondes électromagnétiques présentant au moins une autre fréquence. D'une
manière générale l'invention concerne les applications au moins bi-bande de
fréquences.
L'antenne réflecteur multifréquences AR illustrée comporte une source S
alimentant un réflecteur R en ondes électromagnétiques présentant les
premières (20 GHz) et seconde (30 GHz) fréquences. Tout type de source
efficace connue de l'homme de l'art peut être utilisé à cet effet.Of course, the antenna could be dedicated either exclusively to the reception of electromagnetic wave beams belonging to at least two frequency bands, or both to the transmission of electromagnetic waves having at least one frequency and to receiving electromagnetic waves having at least one other frequency. In general, the invention relates to at least two-band frequency applications.
The AR multifrequency reflecting antenna illustrated comprises a source S feeding a reflector R in electromagnetic waves having the first (20 GHz) and second (30 GHz) frequencies. Any type of efficient source known to those skilled in the art can be used for this purpose.
Bien entendu, au lieu d'une unique source S délivrant à la fois les première et seconde fréquences, selon des diagrammes de transmission choisis, on pourrait avoir deux sources délivrant chacune l'une des première et seconde fréquences selon un diagramme de transmission choisi. Ce qui est important ici ce n'est pas le nombre de sources utilisés, mais l'écart de fréquence entre les première et seconde fréquences.Of course, instead of a single source S delivering both the first and second frequencies, according to transmission diagrams chosen, we could have two sources each delivering one of the first and second frequencies according to a selected transmission pattern. What is important here it's not the number of sources used but the gap of frequency between the first and second frequencies.
Le réflecteur R comporte une coque rigide, ici solidarisée à un bras de déploiement ou à la structure de l'engin spatial (ici un satellite). Cette coque rigide, sur laquelle on reviendra plus loin, comporte une face avant FA destinée à réfléchir les ondes électromagnétiques, délivrées par la source S conformément à ses diagrammes de transmission, sous la forme de premier et second faisceaux dirigés vers une même zone terrestre.The reflector R comprises a rigid shell, here secured to an arm deployment or the structure of the spacecraft (here a satellite). This rigid shell, which will be discussed later, has a front face FA intended to reflect the electromagnetic waves, delivered by the source S according to his transmission diagrams, in the form of first and second beams directed to the same land area.
Selon l'invention, la face avant FA du réflecteur R comprend une structure ST qui définit un motif tridimensionnel (3D) à symétrie de révolution (ou de rotation). Ce motif 3D est choisi de manière à mettre en forme les deux faisceaux de sorte qu'ils présentent des caractéristiques radiofréquences (RF) sensiblement identiques.According to the invention, the front face FA of the reflector R comprises a ST structure which defines a three-dimensional (3D) pattern with symmetry of revolution (or rotation). This 3D pattern is chosen to shape the two beams so that they exhibit radio frequency (RF) characteristics substantially identical.
On entend ici par « caractéristiques radiofréquences » les caractéristiques électromagnétiques, comme par exemple la largeur de faisceau (ou « beam width »), qui caractérise la directivité de l'antenne, et/ou le diagramme de rayonnement électromagnétique, comme par exemple la répartition énergétique dans un plan transversal (lobe principal et lobes secondaires (ou latéraux)), ainsi qu'éventuellement l'affaiblissement (ou « Roll off »).Here we mean by "radio frequency characteristics" the electromagnetic characteristics, such as the width of beam (or beam width), which characterizes the directivity of the antenna, and / or the electromagnetic radiation diagram, such as the energy distribution in a transverse plane (main lobe and lobes side (or lateral)), as well as eventually the weakening (or "roll" off ").
En raison de cette mise en forme des faisceaux par la structure ST du réflecteur R, on peut obtenir des faisceaux (ou pinceaux) très fins. Par exemple, des faisceaux de 20 et 30 GHz peuvent présenter une largeur comprise entre environ 0,5° et 1° (ce qui correspond à une antenne de grande directivité). Dans ce cas, le diamètre de l'antenne à réflecteur AR est compris entre environ 1500 mm et environ 1600 mm, par exemple environ 1560 mm. Because of this shaping of the beams by the ST structure of the reflector R, it is possible to obtain very fine beams (or brushes). By For example, beams of 20 and 30 GHz may have a width between about 0.5 ° and 1 ° (which corresponds to a large antenna) directivity). In this case, the diameter of the AR reflector antenna is included between about 1500 mm and about 1600 mm, for example about 1560 mm.
Bien entendu, l'invention s'applique également à des faisceaux plus larges, voire beaucoup plus larges, mais également plus fins.Of course, the invention also applies to more beams wide, even much wider, but also thinner.
Le motif 3D est calculé à l'aide d'un ordinateur, compte tenu des caractéristiques géométriques désirées pour les deux faisceaux. Le calcul peut également tenir compte des diagrammes de transmission de la source S pour chacune des première (ici 20 GHz) et seconde (ici 30 GHz) fréquences. Cela permet en effet, avantageusement, de corriger au moins partiellement les imperfections des diagrammes de transmission (mais également ceux de réception lorsque l'antenne fonctionne en réception ou en transmission/réception), ainsi que des améliorations non prises en compte.The 3D pattern is calculated using a computer, taking into account the geometric characteristics desired for the two beams. The calculation can also take into account the transmission diagrams of source S for each of the first (here 20 GHz) and second (here 30 GHz) frequencies. This makes it possible, advantageously, to correct at least partially the imperfections of the transmission diagrams (but also those of reception when the antenna operates in reception or transmission / reception), as well as improvements not taken into account.
Le calcul du motif 3D permettant la mise en forme des deux faisceaux peut être effectué en deux étapes : une première étape consistant à résoudre un problème d'illumination d'antenne bidimensionnelle (2D), puis une seconde étape consistant à généraliser le problème à une illumination 3D.The calculation of the 3D pattern allowing the shaping of the two beams can be done in two steps: a first step of solving a two-dimensional (2D) antenna illumination problem, then a second step of generalizing the problem to a 3D illumination.
Le problème 2D à résoudre porte sur la détermination du champ électromagnétique E, issu de l'ouverture, en fonction de l'angle représentant les angles de visée de l'antenne (en général compris entre 0° et 180°), donné par la formule suivante : où Id est le courant dans l'ouverture, k est le nombre d'onde (k=2π/λ), d est une distance dans l'ouverture, et λ est la longueur d'onde.The 2D problem to be solved relates to the determination of the electromagnetic field E, resulting from the opening, as a function of the angle representing the viewing angles of the antenna (generally between 0 ° and 180 °), given by the following formula: where I d is the current in the opening, k is the wave number (k = 2π / λ), d is a distance in the aperture, and λ is the wavelength.
Afin de faciliter la résolution, on peut effectuer le changement de variable suivant : ψ = π.cos() + α.In order to facilitate the resolution, the change of following variable: ψ = π.cos () + α.
On cherche à déterminer une distribution de courant permettant d'obtenir un diagramme de champ lointain aussi proche que possible d'une fonction de type « porte » (ou créneau) ou d'un diagramme de type Chebychev présentant des lobes secondaires (ou latéraux) de très faible niveau (par exemple de -30 dB).We seek to determine a current distribution allowing to get a far field diagram as close as possible to a "gate" type function (or slot) or a type diagram Chebychev with very low side (or lateral) lobes level (for example -30 dB).
Une fois le champ lointain désiré choisi, on lui applique une transformée de Fourier inverse afin d'obtenir la distribution de courant correspondante. Par exemple, lorsque le diagramme de champ lointain est une fonction porte, la distribution de courant est proche d'une fonction sinx/x. Once the desired far field has been chosen, we apply a inverse Fourier transform to obtain the current distribution corresponding. For example, when the far field diagram is a gate function, the current distribution is close to a sinx / x function.
On peut ensuite séparer en deux parties la distribution de courant total selon la formule suivante : CT = CS * CR, où CT est la distribution de courant total (c'est-à-dire la transformée inverse du champ lointain désiré), CS est la contribution de la source S en amplitude et en phase au niveau du réflecteur R, et CR est la contribution du réflecteur R à l'amplitude et à la phase du courant total (par exemple le changement de phase induit par un changement de forme du réflecteur).The total current distribution can then be divided into two parts according to the following formula: C T = C S * C R , where C T is the total current distribution (i.e., the inverse transform of the desired far field ), C S is the contribution of the source S in amplitude and phase at the reflector R, and C R is the contribution of the reflector R to the amplitude and the phase of the total current (for example the induced phase change by a change of shape of the reflector).
Il est ici rappelé que la contribution CS de la source S dépend de son diagramme de transmission (lequel peut être adapté en fonction de la largeur d'ouverture de la source S). CS étant connue et CT ayant été déterminée, on peut alors déduire CR de la dernière formule : CR = CT / CS.It is recalled here that the contribution C S of the source S depends on its transmission diagram (which can be adapted according to the opening width of the source S). C S being known and C T having been determined, it is then possible to deduce C R from the last formula: C R = C T / C S.
Il est important de noter que la contribution CR du réflecteur porte à la fois sur l'amplitude et la phase, signes compris.It is important to note that the C R contribution of the reflector relates to both amplitude and phase, including signs.
Cette fonction CR a par exemple la forme d'un cosinus tronqué présentant un maximum au centre du réflecteur, puis décroissant, puis passant par zéro, puis devenant négatif.This function C R for example has the form of a truncated cosine having a maximum in the center of the reflector, then decreasing, then passing through zero, then becoming negative.
Pour approximer cette fonction on peut juxtaposer des sections de
réflecteur de hauteur 0 mm (section normale) et des sections de hauteur
égale à 7,5 mm (section rehaussée) ou bien à - 7,5 mm (section abaissée),
dans le cas des deux fréquences 20 et 30 GHz. En effet, les longueurs d'onde
sont alors de 15 et 10 mm, et 7,5 mm représente λ/2 et 3λ/4 respectivement
pour les deux fréquences.To approximate this function we can juxtapose sections of
0 mm height reflector (normal section) and height sections
equal to 7.5 mm (raised section) or to - 7.5 mm (lowered section),
in the case of the two
Lorsque l'onde à 20 GHz rencontre une section λ/2, elle se réfléchit et se retrouve déphasée de λ par rapport à la section voisine, si bien qu'elle est en phase avec l'onde voisine.When the wave at 20 GHz encounters a section λ / 2, it is reflected and is out of phase with λ compared to the neighboring section, so that it is in phase with the neighboring wave.
Lorsque l'onde à 30 GHz rencontre une section 3λ/4, elle se réfléchie et se retrouve déphasée de 3λ/2 ou 180° par rapport à la section voisine, si bien qu'elle est en phase avec la section voisine.When the 30 GHz wave meets a 3λ / 4 section, it is reflected and is out of phase with 3λ / 2 or 180 ° compared to the neighboring section, if although it is in phase with the neighboring section.
L'intégrale de sections voisines est donc d'autant plus positive que les sections sont « normales ». Elle est d'autant plus négative que le nombre de sections rehaussées (ou abaissées) est important. Ainsi, on peut approximer la fonction CR en juxtaposant des sections normales (ou positives) et des sections rehaussées (ou négatives, ou abaissées) en proportions nécessaires selon l'amplitude et le signe local de CR.The integral of neighboring sections is therefore all the more positive if the sections are "normal". It is all the more negative as the number of sections raised (or lowered) is important. Thus, we can approximate the function C R by juxtaposing normal sections (or positive) and raised sections (or negative, or lowered) in necessary proportions according to the amplitude and the local sign of C R.
La finesse ou précision de l'intégrale est proportionnelle à la largeur des sections.The fineness or precision of the integral is proportional to the width sections.
Un exemple de distribution de courant total CT en fonction du rayon du réflecteur est donné sur la figure 2.An example of total current distribution C T as a function of the radius of the reflector is given in FIG.
Une simple généralisation à trois dimensions (par symétrie de révolution au premier ordre) permet alors d'obtenir la forme du motif 3D (et donc du réflecteur R) qui permet d'obtenir la distribution de courant total CT désirée. Le motif 3D a donc pour objet principal de modifier le diagramme de phase du réflecteur R, ou en d'autres termes d'introduire un motif de décalage, par rapport à une parabole de référence, à symétrie de révolution (ou de rotation), par rapport à la forme standard dudit réflecteur R, par exemple parabolique.A simple three-dimensional generalization (by first-order symmetry of revolution) then makes it possible to obtain the shape of the 3D pattern (and therefore of the reflector R) which makes it possible to obtain the desired total current distribution C T. The main purpose of the 3D pattern is thus to modify the phase diagram of the reflector R, or in other words to introduce an offset pattern, with respect to a reference parabola, with symmetry of revolution (or rotation), relative to the standard form of said reflector R, for example parabolic.
Un exemple d'un tel motif de décalage est illustré sur la figure 3.An example of such an offset pattern is illustrated in FIG.
Afin de mettre en oeuvre le motif de décalage précité, le motif 3D est préférentiellement réalisé sous la forme de bandes concentriques BC (ou « couronnes ») 3D en saillie ou en creux. Il est important de noter que ces bandes concentriques BC peuvent, dans certaines situations, ne pas être continues sur 360°. Elles peuvent en effet présenter des zones dans lesquelles elles sont interrompues. Cependant, la forme d'une bande concentrique BC, c'est-à-dire sa section transverse, est constante (en dehors des éventuelles zones d'interruption).In order to implement the aforementioned offset pattern, the 3D pattern is preferably in the form of concentric strips BC (or "Crowns") 3D protruding or recessed. It is important to note that these concentric bands BC may, in some situations, not be continuous 360 °. They may indeed have areas in which they are interrupted. However, the shape of a band concentric BC, that is to say its cross section, is constant (outside possible interruption zones).
Trois exemples partiels de motifs 3D sont illustrés sur les figures 4 à 6, dans des vues en coupe transversale. Plus précisément, l'exemple illustré sur la figure 4 correspond à un motif 3D symétrique en saillie, dans lequel les bandes concentriques BC sont toutes identiques (largeur d1 constante et hauteur h constante) et espacées d'un pas d2 constant. En variante, la largeur d1 et le pas d2 peuvent être constants, et la hauteur h peut varier d'une bande concentrique BC à l'autre.Three partial examples of 3D patterns are illustrated in FIGS. 6, in cross-sectional views. Specifically, the illustrated example FIG. 4 corresponds to a projecting symmetrical 3D pattern, in which the concentric bands BC are all identical (width d1 constant and height h constant) and spaced at a constant pitch d2. Alternatively, the width d1 and step d2 can be constant, and the height h can vary from one concentric band BC to another.
L'exemple illustré sur la figure 5 correspond à un motif 3D en saillie, dans lequel certaines bandes concentriques BC présentent des formes différentes et des espacements irréguliers. Par exemple, une bande concentrique BC peut présenter une largeur d1, une autre bande concentrique BC peut présenter une largeur d3, et encore une autre bande concentrique BC peut présenter une largeur d5. Dans ce cas, l'espacement entre bandes concentriques voisines est préférentiellement variable (ici, l'espacement d2 est plus petit que l'espacement d4), et la hauteur h varie préférentiellement d'une bande concentrique BC à l'autre.The example illustrated in FIG. 5 corresponds to a protruding 3D pattern, in which certain concentric bands BC have shapes different and irregular spacings. For example, a band concentric BC may have a width d1, another band concentric BC may have a width d3, and yet another band concentric BC may have a width d5. In this case, spacing between neighboring concentric bands is preferentially variable (here, the spacing d2 is smaller than the spacing d4), and the height h varies preferentially from one concentric band BC to the other.
L'exemple illustré sur la figure 6 correspond également à un motif 3D en creux, dans lequel toutes les bandes concentriques BC présentent des formes différentes et des espacements irréguliers. Par exemple, une bande concentrique BC peut présenter une largeur d2, une autre bande concentrique BC peut présenter une largeur d4, et encore une autre bande concentrique BC peut présenter une largeur d6. Dans ce cas, l'espacement entre bandes concentriques voisines varie (ici d1 ≠ d3 ≠ d5 ≠ d7), et la hauteur h varie préférentiellement d'une bande concentrique BC à l'autre.The example illustrated in FIG. 6 also corresponds to a 3D pattern in which all concentric bands BC have different shapes and irregular spacings. For example, a band concentric BC may have a width d2, another band concentric BC may have a width d4, and yet another band concentric BC may have a width d6. In this case, spacing between neighboring concentric bands varies (here d1d3d5d7), and the height h varies preferentially from one concentric band BC to another.
Par exemple, la hauteur h est égale à environ 7,5 mm, et les largeurs et espacements di sont compris entre environ 80 mm et 400 mm.For example, the height h is equal to about 7.5 mm, and the widths and spacings di are between about 80 mm and 400 mm.
Comme cela est mieux illustré sur la figure 7, les bandes concentriques BC du motif 3D comportent préférentiellement des bords d'attaque BA arrondis présentant un rayon de giration (ou de courbure) compris entre environ 1 mm et environ 200 mm, et plus préférentiellement entre environ 10 mm et environ 40 mm.As best illustrated in Figure 7, the bands concentric BC of the 3D pattern preferentially have edges BA rounded nose with radius of gyration (or curvature) between about 1 mm and about 200 mm, and more preferably between about 10 mm and about 40 mm.
Cela permet avantageusement de réaliser la structure ST définissant le motif 3D à l'aide des matériaux ultralégers couramment utilisés dans les applications spatiales, et notamment en matériaux composites fibres de carbone / matrice organique ou autre (par exemple en CFRP pour « Carbon Fiber Reinforced Plastics »), ou en tout autre matériau équivalent connu de l'homme de l'art, comme par exemple des laminés préimprégnés carbone /résine (unidirectionnels ou tissés).This advantageously makes it possible to produce the ST structure defining the 3D pattern using the ultra-light materials commonly used in space applications, and in particular in composite fiber materials carbon / organic matrix or other (for example CFRP for "Carbon Fiber Reinforced Plastics "), or any other equivalent material known to those skilled in the art, such as laminates prepreg carbon / resin (unidirectional or woven).
Le matériau constituant le motif 3D peut être éventuellement métallisé afin de minimiser les pertes radioélectriques. Par ailleurs, un contrôle thermique du réflecteur R peut être classiquement obtenu au moyen d'un radome placé sur sa face avant FA et d'un isolant thermique, en technologie SLI (pour « Single Layer Insulation » ou Isolation à une couche) ou en technologie MLI (pour « Multiple Layer Insulation » ou Isolation à couche multiple), par exemple une feuille ou un feuilleté de Kapton, placé sur sa face arrière. En variante, on peut seulement prévoir un isolant thermique sur la face arrière.The material constituting the 3D pattern can be optionally metallized to minimize radio losses. In addition, a control thermal reflector R can be classically obtained by means of a radome placed on its front face FA and thermal insulation, in technology SLI (for Single Layer Insulation) or in MLI technology (for "Multiple Layer Insulation") multiple), for example a Kapton leaf or laminate, placed on its face back. Alternatively, one can only provide a thermal insulation on the back side.
Il est important de noter que d'autres matériaux plus lourds, comme par exemple l'aluminium, l'acier, ou un alliage, peuvent être utilisés dans des applications pour lesquelles le poids ne représente pas un inconvénient, comme par exemple dans les applications terrestres.It is important to note that other heavier materials, such as for example, aluminum, steel, or an alloy, can be used in applications for which the weight does not represent a disadvantage, as for example in terrestrial applications.
On a représenté sur la figure 8, dans une vue en coupe transversale, un exemple de portion de motif 3D dans lequel les bandes concentriques BC présentent une section transverse du type de celle illustrée sur la figure 7, c'est-à-dire à bords d'attaque BA arrondis.FIG. 8 shows in a cross-sectional view, an example of a 3D pattern portion in which the concentric strips BC have a transverse section of the type of that illustrated in FIG. i.e. with rounded BA leading edges.
En général le motif 3D s'étend sur toute la face avant FA du réflecteur R, comme illustré sur le diagramme de la figure 9, mais il peut également s'étendre seulement sur une partie de la face avant FA du réflecteur R, et dans ce cas il y a peu ou pas de bande concentrique BC dans la zone centrale, comme illustré sur le diagramme de la figure 10. Ces deux diagrammes représentent, dans une projection planaire, les positions des différentes bandes concentriques BC (qui sont ici transformées en lignes du fait de la projection) par rapport au centre du réflecteur R. L'axe des abscisses est gradué de 1 à 201, et matérialise 200 points compris entre le centre et le bord du réflecteur R. L'axe des ordonnées matérialise la hauteur h (en mm) des bandes concentriques BC, par exemple environ 7,5 mm.In general, the 3D pattern extends over the entire front face FA of the reflector R, as shown in the diagram of Figure 9, but it can also extend only on part of the front face FA of the reflector R, and in this case there is little or no concentric band BC in the zone as shown in the diagram in Figure 10. These two diagrams represent, in a planar projection, the positions of the different BC concentric bands (which are here transformed into lines of projection) relative to the center of the reflector R. The axis of The abscissa is graduated from 1 to 201, and materializes 200 points between center and the edge of the reflector R. The ordinate axis shows the height h (in mm) concentric strips BC, for example about 7.5 mm.
Par ailleurs, la structure ST, définissant le motif 3D, peut être soit rapportée sur la face avant FA du réflecteur R, soit faire partie intégrante de celui-ci. Ainsi, dans l'exemple illustré sur la figure 11 (ainsi que dans les exemples des figures 14 à 16 sur lesquels on reviendra plus loin), la structure ST est constituée de plusieurs groupes de bandes concentriques BC rapportés sur la face avant FA de la coque du réflecteur R. Dans ce cas, chaque groupe est réalisé à l'aide d'un moule spécifique, puis rapporté, par exemple par collage, sur la face avant FA de la coque du réflecteur R.Furthermore, the ST structure, defining the 3D pattern, can be either reported on the front face FA of the reflector R, be an integral part of this one. Thus, in the example illustrated in FIG. 11 (as well as in examples of Figures 14 to 16 which will be discussed later), the structure ST consists of several BC concentric band groups reported on the front face FA of the reflector shell R. In this case, each group is made using a specific mold, then reported, by example by gluing, on the front face FA of the hull of the reflector R.
Dans l'exemple illustré sur la figure 12, la structure ST fait partie intégrante de la coque du réflecteur R. Le moule, permettant l'élaboration de la coque, comporte par conséquent l'empreinte en négatif de la structure ST. Le motif 3D est donc fabriqué en même temps que la coque, par cuisson, par exemple à 180°C (la température dépend bien entendu du type de résine utilisé). De tels moules peuvent être réalisés au moyen de la technologie d'usinage dite 5D. On peut noter que la coque peut être réalisée avec un espaceur d'épaisseur constante ou non.In the example illustrated in FIG. 12, the ST structure is part of integral part of the reflector shell R. The mold, allowing the elaboration of the shell, therefore comprises the negative imprint of the ST structure. The 3D pattern is therefore manufactured at the same time as the shell, by cooking, by example at 180 ° C (the temperature of course depends on the type of resin used). Such molds can be made using technology machining so-called 5D. It can be noted that the hull can be made with a spacer of constant thickness or not.
Dans l'exemple illustré sur la figure 13, la structure ST fait également partie intégrante de la coque du réflecteur R. Contrairement à l'exemple de la figure 12 dans lequel seul la face avant comporte le motif 3D, ici la face avant FA et la face arrière AR comportent le motif 3D. Cela nécessite un moule comportant une première portion munie du motif 3D en négatif et une seconde portion munie du motif 3D en positif. Ce mode de réalisation de la coque du réflecteur R facilite son élaboration, notamment en série par moulage ou par estampage à chaud (entre un poinçon et un contre-poinçon), ou encore par toute autre technique. Il est important de noter que seule la face avant FA est fonctionnelle.In the example illustrated in FIG. 13, the ST structure also makes part of the hull of the reflector R. Unlike the example of the 12 in which only the front face has the 3D pattern, here the front face FA and the back AR have the 3D pattern. This requires a mold having a first portion provided with the negative 3D pattern and a second portion provided with the 3D pattern in positive. This embodiment of the Reflector shell R facilitates its development, especially in series by molding or by hot stamping (between a punch and a counterpunch), or by any other technique. It is important to note that only the front face FA is functional.
Comme cela est illustré sur les figures 14 à 16, le réflecteur selon l'invention peut être installé de la même façon que n'importe quel réflecteur traditionnel. Ainsi, dans l'exemple illustré sur la figure 14, dans une vue en coupe transversale, le réflecteur R, de type cellulaire en technologie dite « coque épaisse », en concept sandwich, est monté sur un bras de déploiement BD relié à une plateforme du satellite.As illustrated in FIGS. 14 to 16, the reflector according to the invention can be installed in the same way as any reflector traditional. Thus, in the example illustrated in FIG. 14, in a view in cross-section, the reflector R, of cellular type in so-called "Thick shell", sandwich concept, is mounted on an arm of BD deployment connected to a satellite platform.
Dans l'exemple illustré sur la figure 15, dans une vue en coupe transversale, le réflecteur R, de type cellulaire en technologie dite « coque mince raidie », en concept sandwich, est monté sur une structure rigide SR du satellite, par exemple au moyen de clips en L. Un tel agencement offre une bonne tenue mécanique et une bonne stabilité dimensionnelle.In the example illustrated in FIG. 15, in a sectional view transverse, the reflector R, cell type technology called "shell thin stiffened ", sandwich concept, is mounted on a rigid structure SR of satellite, for example by means of L-shaped clips. Such an arrangement provides a good mechanical strength and good dimensional stability.
Dans l'exemple illustré sur la figure 16, dans une vue en coupe transversale, le réflecteur, à coque ultrafine, est monté sur une structure rigide SR dite monolithique, constituée d'un unique élément ou d'un assemblage d'éléments monolithiques, par exemple au moyen de clips en L, éventuellement collés. Un tel agencement offre également une bonne tenue mécanique et une bonne stabilité dimensionnelle.In the example illustrated in FIG. 16, in a sectional view transverse, the reflector, with ultrafine shell, is mounted on a rigid structure So-called monolithic SR, consisting of a single element or an assembly monolithic elements, for example by means of L-shaped clips, possibly glued. Such an arrangement also offers good holding mechanical and good dimensional stability.
L'antenne réflecteur multifréquences selon l'invention offre de nombreux avantages comparée aux antennes de l'art antérieur.The multifrequency reflector antenna according to the invention offers many advantages compared to antennas of the prior art.
Ainsi, elle permet d'obtenir des faisceaux présentant des largeurs de faisceau, sensiblement identiques, sans perte d'efficacité.Thus, it makes it possible to obtain beams having widths of beam, substantially identical, without loss of efficiency.
Elle permet en outre de réduire les lobes secondaires (ou latéraux) quelle que soit la fréquence considérée, ce qui confère une bonne isolation des différentes fréquences et un bon rapport C/I d'isolation agrégée.It also makes it possible to reduce the side (or lateral) lobes whatever the frequency considered, which gives good insulation different frequencies and a good C / I ratio of aggregate insulation.
Elle permet également d'obtenir des faisceaux présentant des roll-offs comparables, voire même sensiblement identiques, et réduits.It also makes it possible to obtain bundles presenting roll-offs comparable, or even substantially identical, and reduced.
Elle permet également de prendre en compte le diagramme d'émission de la source et/ou le diagramme de réception du collecteur, afin d'en corriger les éventuelles imperfections.It also allows to take into account the diagram of the source and / or the collector's reception pattern, in order to to correct any imperfections.
Elle permet enfin une utilisation dans tout type d'application et en particulier dans les applications spatiales, notamment du fait que le nombre d'antennes peut être divisé par deux (ce nombre peut en effet, par exemple, être ramené à 3 ou 4 quand dans la technique antérieur il est égal à 6 ou 8).It finally allows use in any type of application and in particular in space applications, especially as the number of of antennas can be divided by two (this number can indeed, for example, to be reduced to 3 or 4 when in the prior art it is equal to 6 or 8).
L'invention ne se limite pas aux modes de réalisation d'antenne réflecteur multifréquences décrits ci-avant, seulement à titre d'exemple, mais elle englobe toutes les variantes que pourra envisager l'homme de l'art dans le cadre des revendications ci-après.The invention is not limited to antenna embodiments multifrequency reflector described above, only as an example, but it encompasses all the variants that can be envisaged by those skilled in the art in the scope of the claims below.
Ainsi, l'invention concerne toute antenne réflecteur munie d'une structure définissant un motif tridimensionnel à symétrie de révolution et présentant des bords d'attaque de forme arrondie et « doux ».Thus, the invention relates to any reflector antenna provided with a structure defining a three-dimensional pattern with symmetry of revolution and with rounded and "soft" leading edges.
Claims (19)
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FR0450662A FR2868611B1 (en) | 2004-04-02 | 2004-04-02 | REFLECTIVE ANTENNA HAVING A 3D STRUCTURE FOR FORMING WAVE BEAMS BELONGING TO DIFFERENT FREQUENCY BANDS |
FR0450662 | 2004-04-02 |
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US (1) | US7280086B2 (en) |
EP (1) | EP1583176B1 (en) |
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DE (1) | DE602005005098T2 (en) |
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CA2917044A1 (en) * | 2013-06-28 | 2014-12-31 | Associated Universities, Inc. | Randomized surface reflector |
US10797401B2 (en) | 2016-12-13 | 2020-10-06 | Mitsubishi Electric Corporation | Reflection mirror antenna device |
US20180337460A1 (en) * | 2017-05-18 | 2018-11-22 | Srg Global Inc. | Vehicle body components comprising retroreflectors and their methods of manufacture |
US10723299B2 (en) * | 2017-05-18 | 2020-07-28 | Srg Global Inc. | Vehicle body components comprising retroreflectors and their methods of manufacture |
FR3086105B1 (en) * | 2018-09-13 | 2020-09-04 | Thales Sa | RADIOFREQUENCY REFLECTOR NETWORK FOR SATELLITE ANTENNA AND RADIOFREQUENCY REFLECTOR NETWORK FOR SATELLITE ANTENNA INCLUDING AT LEAST ONE SUCH PANEL |
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EP1020953A2 (en) * | 1999-01-15 | 2000-07-19 | TRW Inc. | Multi-pattern antenna having frequency selective or polarization sensitive zones |
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US20040036661A1 (en) * | 2002-08-22 | 2004-02-26 | Hanlin John Joseph | Dual band satellite communications antenna feed |
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2004
- 2004-04-02 FR FR0450662A patent/FR2868611B1/en not_active Expired - Fee Related
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2005
- 2005-03-25 DE DE602005005098T patent/DE602005005098T2/en active Active
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EP1020953A2 (en) * | 1999-01-15 | 2000-07-19 | TRW Inc. | Multi-pattern antenna having frequency selective or polarization sensitive zones |
EP1083625A2 (en) * | 1999-09-10 | 2001-03-14 | TRW Inc. | Frequency selective reflector |
US20040036661A1 (en) * | 2002-08-22 | 2004-02-26 | Hanlin John Joseph | Dual band satellite communications antenna feed |
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WO2009032418A2 (en) | 2007-08-28 | 2009-03-12 | Cryovac, Inc. | Multilayer film having passive and active oxygen barrier layers |
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US7280086B2 (en) | 2007-10-09 |
EP1583176B1 (en) | 2008-03-05 |
US20050219146A1 (en) | 2005-10-06 |
ES2302149T3 (en) | 2008-07-01 |
CA2500990A1 (en) | 2005-10-02 |
FR2868611B1 (en) | 2006-07-21 |
DE602005005098D1 (en) | 2008-04-17 |
FR2868611A1 (en) | 2005-10-07 |
ATE388502T1 (en) | 2008-03-15 |
DE602005005098T2 (en) | 2009-03-26 |
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