(19)
(11)EP 3 893 323 A1

(12)EUROPEAN PATENT APPLICATION

(43)Date of publication:
13.10.2021 Bulletin 2021/41

(21)Application number: 21167497.3

(22)Date of filing:  08.04.2021
(51)International Patent Classification (IPC): 
H01P 1/161(2006.01)
H01Q 13/02(2006.01)
(52)Cooperative Patent Classification (CPC):
H01P 1/161; H01Q 13/0208
(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR
Designated Extension States:
BA ME
Designated Validation States:
KH MA MD TN

(30)Priority: 09.04.2020 IT 202000007681

(71)Applicant: PICOSATS S.R.L.
34149 Trieste (IT)

(72)Inventors:
  • Pagana, Enrico
    10023 Chieri (TO) (IT)
  • Gotti, Gianbattista
    9475 Sevelen (SG) (CH)
  • Gregorio, Anna
    34135 Trieste (IT)

(74)Representative: Petraz, Gilberto Luigi et al
GLP S.r.l.
Viale Europa Unita, 171 33100 Udine
Viale Europa Unita, 171 33100 Udine (IT)

  


(54)ORTHOMODE TRANSDUCER FOR AN ANTENNA, AND ANTENNA FOR SATELLITES


(57) The orthomode transducer for antenna comprises a waveguide body extended along a longitudinal axis and comprising a first end and a second end, a first port connected to the first end of the waveguide body, and a second port, the two ports being suitable to be connected to an electronic circuit. The application also describes an antenna for satellites that comprises the orthomode transducer, a polarizer connected to the orthomode transducer, and an interception member connected to the polarizer.




Description

FIELD OF THE INVENTION



[0001] The present invention concerns an orthomode transducer for an antenna for satellites, and an antenna for satellites which comprises said orthomode transducer. In particular, the satellites for which the antenna is provided are of the miniaturized and modular type, known as Cubesats.

BACKGROUND OF THE INVENTION



[0002] The commitment to reduce the size and weight of satellites has long been known, in order to make their launch into space easier and above all less expensive. In fact, because of the costs, the launch of classic satellites, of big sizes, is accessible to very few national or supranational agencies.

[0003] With the advance in the engineering of miniaturized satellites, it has been possible to obtain satellites in the order of ten centimeters in size and weighing less than one kilogram. Such satellites are called picosatellites.

[0004] Among picosatellites, the so-called Cubesat is known, a satellite with a cubic shape, with sides 10 cm long. The Cubesat, in addition to being of very limited size and weight, also has the advantage of being modular, that is, it is possible to assemble several Cubesats to obtain a picosatellite with a shape and size that can be adapted according to requirements.

[0005] Obviously, to obtain miniaturized satellites that can perform well, it is also necessary to miniaturize the internal components, in particular the electronic circuit for signal processing and the antenna, without affecting the performance of the system. Indeed, with space exploration missions that provide to send satellites and robots further and further away, it is also desirable to have a material with ever higher performance.

[0006] By way of example of the expected performance, currently satellites have to operate in the K and Ka frequency bands, and connection balances of current missions provide a minimum gain of the satellite antenna that is greater than 20dBi at minimum frequency, which is generally 17.8 GHz.

[0007] Furthermore, satellites, and in particular their antenna, must be able to function both in reception and in transmission. In reception, the antenna normally receives a signal with a circular polarization and must be able to separate the received signal into two signals with linear polarizations. Vice versa, in transmission the antenna must process two signals with linear polarizations and transmit a signal with a circular polarization.

[0008] To perform this specific function, the antennas are equipped with a polarizer and an orthomode type transducer. Generally, this type of transducer comprises two ports for single-mode signals, with polarizations of the signals orthogonal to each other, and a common port which allows to propagate the two previously mentioned single-mode signals. An orthomode transducer of this type is described in patent application EP 2600465. Such transducers can sometimes be difficult to integrate inside miniaturized satellites, even more so in Cubesats.

[0009] US-A-2010/123636 describes an antenna equipped with an orthomode transducer which comprises a waveguide body with a circular internal shape, a junction body and a single port defined by the combination of the end of the waveguide body and the end of the junction body.

[0010] US-B-4,047,128 shows an orthomode transducer comprising a waveguide body equipped with a port, and a second port parallel to the waveguide body and connected to it by means of two junctions. This transducer does not provide any junction body to carry the second port.

[0011] The scientific article identifiable by the number XP000266379 shows an orthomode transducer equipped with a circular waveguide body and a junction body. This orthomode transducer comprises a first port connected to the waveguide body and a second port defined at one end of the junction body. The first port extends transversely from the waveguide body, and is perpendicular to the second port.

[0012] WO-A-2020/051459 shows an antenna for a satellite comprising a paraboloid interception member with corrugations longitudinal to its longitudinal axis.

[0013] CN-B-102800993 shows a satellite with an antenna that comprises an interception member connected to a polarizer, which in turn is connected to an orthomode transducer. The polarizer has a square cross section and is oriented so that its longitudinal surfaces are inclined by an angle of 45° with respect to the orthomode transducer. All the longitudinal surfaces of the polarizer are smooth.

[0014] Another limitation of known orthomode transducers is that they function at a single frequency, that is, they are able to separate signals into two different polarizations but always at the same frequency and over a limited frequency bandwidth.

[0015] There is therefore a need to perfect an orthomode transducer as well as an antenna that can overcome at least one of the disadvantages of the state of the art.

[0016] In particular, one purpose of the present invention is to provide an orthomode transducer that is of limited size and weight.

[0017] Within this aim, another purpose of the invention is to provide an orthomode transducer that has a performance in accordance with the requirements given by the connection balances.

[0018] Another purpose of the present invention is to provide an antenna for satellites that can be integrated into miniaturized satellites, in particular Cubesats, while maintaining high performance.

[0019] The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION



[0020] The present invention is set forth and characterized in the independent claim. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea.

[0021] In accordance with the above purposes, we describe an orthomode transducer, as well as an antenna for satellites, which overcome the limits of the state of the art and eliminate the defects present therein.

[0022] In accordance with some embodiments, an orthomode transducer is provided comprising a preferably cylindrical waveguide body, which acts as a waveguide. This waveguide body is extended along a longitudinal axis and comprises a first end and a second end. The second end is suitable to be connected with the rest of the antenna, for example a polarizer.

[0023] The orthomode transducer comprises a first port, suitable to be connected to an electronic circuit. This first port is connected directly to the first end of the waveguide body.

[0024] The orthomode transducer also comprises a junction body, preferably in the shape of a plate, that is, having a surface extension greater than its thickness. The junction body has a first end, facing the first end of the waveguide body, and a second end, facing the second end of the waveguide body. The junction body is advantageously disposed parallel to the waveguide body.

[0025] The orthomode transducer is provided with at least one junction that connects the junction body to the waveguide body. The junction is connected to the waveguide body in correspondence with a junction zone.

[0026] According to some embodiments, the junction extends at least in part in a direction orthogonal to the axis of the cylindrical waveguide body.

[0027] It is advantageous to provide that the orthomode transducer comprises two junctions connected to the waveguide body in correspondence with two junction zones symmetrical to each other with respect to the longitudinal axis of the waveguide body, that is, diametrically opposite with respect to each other.

[0028] According to some embodiments, the two junctions are symmetrical with respect to a symmetry plane which comprises the longitudinal axis of the waveguide body.

[0029] The orthomode transducer also comprises a second port, suitable to be connected to an electronic circuit, and connected directly to the first end of the junction body. Advantageously, the first port comprises its own end surface and the second port comprises its own end surface disposed parallel to the end surface of the first port. These end surfaces each have their own extension axis oriented in a direction orthogonal to the extension axis of the other end surface.

[0030] Preferably, the first port is connected to the first end of the waveguide body by means of a first transition portion configured stepped, that is, which comprises a plurality of sections of progressively increasing lateral size. Even more preferably, at least part of the sections as above also have a progressively varying shape, so as to connect the first port with a rectangular section with the waveguide body with a circular section.

[0031] Advantageously, the second port is connected to the junction body by means of a second transition portion configured stepped, that is, which comprises a plurality of sections of progressively increasing lateral size.

[0032] The orthomode transducer comprises a separator, technically also called dichroic separator, configured to separate frequencies, that is, configured to allow the passage of signals with a frequency lower than a threshold frequency, and reflect signals with a frequency greater than the threshold frequency, or vice versa. Advantageously, the separator is configured to also separate the polarizations.

[0033] Preferably, the dichroic separator comprises a reflection member, which is also called dichroic, suitable to selectively reflect a predetermined frequency band. More preferentially, the separator comprises a plurality of septa that pass through the waveguide body and are oriented transversely to the waveguide body. For example, the separator can comprise a central septum that is centered with respect to the waveguide body, and which has a greater longitudinal extension than the other septa. By longitudinal extension we mean the extension measured longitudinally with respect to the waveguide body.

[0034] According to one aspect, there is provided an antenna for satellites, in particular for picosatellites, comprising an orthomode transducer, a polarizer connected to the orthomode transducer, and an interception member connected to the polarizer. The orthomode transducer in turn comprises a first port and a second port, both suitable to be connected to an electronic circuit.

[0035] Preferably, the orthomode transducer is of the type described above. In other words, preferably the orthomode transducer comprises a waveguide body extended along a longitudinal axis between a first end and a second end, a first port connected to the first end of the waveguide body and suitable to be connected to an electronic circuit, a junction body comprising a first end, facing the first end of the waveguide body, and a second end, facing the second end of the waveguide body, at least one junction connected both to the junction body and also to the waveguide body in correspondence with a junction zone, and a second port connected to the first end of the junction body, and suitable to be connected to an electronic circuit.

[0036] The polarizer comprises a hollow body with a rectangular or square section, therefore comprising four longitudinal surfaces facing each other two by two.

[0037] The polarizer is corrugated on two longitudinal surfaces which are counter-facing each other.

[0038] Preferably, each corrugated wall comprises a plurality of transverse septa which extend toward the inside of the hollow polarizer, defining deviation septa. The transverse septa are parallel to each other. Preferably, there are at least two transverse end septa and at least one central septum.

[0039] It is advantageous to provide that the transverse septa have a substantially rectangular section. It is even more advantageous to provide that the transverse septa that extend from the same longitudinal surface have a progressively variable depth, or extension, with respect to each other, starting from an end septum to the central septum. The deepest septum, that is, the septum with the greatest extension, is preferably the central septum.

[0040] Preferably, the corrugated longitudinal surface of the polarizer is disposed in a longitudinal direction with respect to the waveguide body of the orthomode transducer and inclined with respect to the orientation of the ports.

[0041] The corrugated longitudinal surface is inclined by an angle of 45° with respect to the orientation of the ports, in order to obtain a circular polarization starting from the two linear polarizations.

[0042] According to some embodiments, the interception member comprises a body with a shaped profile that connects two cylindrical sections, one connected to the polarizer and the other to the radiant aperture, with a progressively increasing section. According to some embodiments, the shaped profile follows a substantially exponential, or paraboloid, trend or a composite curve.

[0043] In order to operate with high radiation performance over a very broad frequency band, typically greater than 50%, the internal surface of the interception member is preferentially corrugated. In particular, the internal surface comprises a plurality of circular fins disposed parallel to each other.

BRIEF DESCRIPTION OF THE DRAWINGS



[0044] These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein:
  • fig. 1 is a perspective view of an antenna according to the present description;
  • figs. 2A and 2B are a perspective view of an orthomode transducer of the antenna of fig. 1, and a perspective view of the same orthomode transducer in partial section;
  • fig. 3 is a perspective view of a polarizer of the antenna of fig. 1;
  • fig. 3A is a section view along plane III-III of fig. 3;
  • figs. 4A and 4B are a perspective view of a section of an interception member of the antenna of fig. 1, and a section view of a part of the same interception member; and
  • figs. 5A and 5B are perspective views of two details of the antenna of fig. 1.


[0045] To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can conveniently be incorporated into other embodiments without further clarifications.

DETAILED DESCRIPTION OF SOME EMBODIMENTS



[0046] We will now refer in detail to the possible embodiments of the invention, of which one or more examples are shown in the attached drawings. Each example is supplied by way of illustration of the invention and shall not be understood as a limitation thereof. For example, one or more characteristics shown or described insomuch as they are part of one embodiment can be varied or adopted on, or in association with, other embodiments to produce another embodiment. It is understood that the present invention shall include all such modifications and variants.

[0047] Before describing these embodiments, we must also clarify that the present description is not limited in its application to details of the construction and disposition of the components as described in the following description using the attached drawings. The present description can provide other embodiments and can be obtained or executed in various other ways. We must also clarify that the phraseology and terminology used here is for the purposes of description only, and cannot be considered as limitative.

[0048] Fig. 1 shows an antenna for satellites, in particular for picosatellites, according to one embodiment of the invention, and indicated as a whole with number 10.

[0049] The antenna 10 is suitable to be connected to an electronic circuit, for example of the type that transmits and receives electromagnetic signals.

[0050] The antenna 10 comprises an orthomode transducer 20, suitable to be connected to the electronic circuit as above, a polarizer 30, connected to the orthomode transducer 20, and an interception member 40, connected to the polarizer 30. Advantageously, the orthomode transducer 20, the polarizer 30 and the interception member 40 are directly connected to each other.

[0051] Advantageously, the antenna 10 also comprises a first waveguide transition 50 and a second waveguide transition 60 disposed respectively between the polarizer 30 and the orthomode transducer 20, and between the polarizer 30 and the interception member 40.

[0052] It should be noted that the components of the antenna 10 are disposed aligned with each other and define a development axis X of the antenna 10, along which the antenna 10 is extended (fig. 1). These components have been designed so that, once assembled, the antenna 10 has a total length of no more than 30 cm. In this way, the antenna 10 can be contained in three aligned Cubesat modules of 10 cm on each side.

[0053] The orthomode transducer 20 comprises a waveguide body 21 connected, in correspondence with its first end 21A, to a port 22 for the passage of an electromagnetic signal (fig. 2A). This port 22 is suitable to be connected directly with an electronic circuit. The waveguide body 21 also has a second end 21B, opposite the first, suitable to connect with the transducer 30, as shown in fig. 1.

[0054] It should be noted that the waveguide body 21 has an elongated shape extended, during use, along the development axis X of the antenna 10. At least part of the waveguide body 21 acts as a waveguide, both for waves received by the antenna, and therefore coming from the polarizer 30, and also for the waves transmitted by the antenna, and therefore coming from the electronic circuit.

[0055] As can be seen from fig. 2A, the first port 22 has a rectangular end surface 22A, the long side of which is oriented in a first direction D1, shown vertically in the drawing.

[0056] Preferably, the port 22 has a cuboid body, that is, in the shape of a parallelepiped the faces of which are rectangular.

[0057] The orthomode transducer 20 also comprises a junction body 23 advantageously in the shape of a shaped plate and disposed parallel to the waveguide body 21. The junction body 23 is connected to the waveguide body 21 by means of at least one junction 24, preferably two, as shown in figs. 2A and 2B.

[0058] According to some embodiments, the junction body 23 and the junctions 24 define a "T" shape, in which the two junctions 24 extend in an orthogonal direction, and on opposite sides with respect to a central longitudinal portion.

[0059] The junctions 24 are preferably shaped substantially as a rounded C, with the concavity facing inward with respect to the orthomode transducer 20, and a rectangular-shaped section. They extend from the junction body 23 and are connected integral with the waveguide body 21 so as to guarantee contact both with the junction body 23 and also with the waveguide body 21.

[0060] Preferably, the junctions 24 are symmetrical to each other with respect to a plane which comprises the longitudinal axis of the waveguide body 21, which in the present case coincides with the development axis X of the antenna 10. More preferably, the symmetry plane also comprises a median longitudinal axis of the junction body 23. Even more preferably, the junctions 24 come into contact with the waveguide body 21 in correspondence with two junction zones 21C of the external surface of the waveguide body 21 which are symmetrical to each other with respect to the longitudinal axis of the same waveguide body 21.

[0061] The junction body 23 comprises a first end 23A disposed substantially facing the first end 21A of the waveguide body 21, and with a rectangular-shaped section, and a second end 23B disposed substantially facing the second end 21B of the waveguide body 21. To the first end 23A of the junction body 23 there is connected a second port 25 for the passage of an electromagnetic signal (fig. 2A), which also comprises a preferably cuboid body and therefore having an end surface 25A of rectangular shape. The second port 25 is suitable to be directly connected to the electronic circuit.

[0062] The end surface 25A (that is, its long side) of the second port 25 is oriented in a second direction D2, suitably orthogonal to the first direction D1. It should be noted that the end surfaces 22A, 25A of the first and second port 22, 25 are disposed parallel to each other, in this example they are both orthogonal to the development axis X of the antenna 10.

[0063] The orthomode transducer 20 preferably comprises a first transition connector 26 conformed stepped which reciprocally connects the first port 22 and the waveguide body 21. This connector preferably comprises a plurality of sections 26A of decreasing lateral size starting from the waveguide body 21 to the first port 22, so as to gradually converge toward the first port 22.

[0064] According to some embodiments, the first transition connector 26 is also configured to act as a transition of shape between the waveguide body 21, with a circular section, and the first port 22, with a rectangular section. In particular, the sections 26A of the first transition connector 26 also have progressively variable shapes with the edges consisting of rectilinear segments with rounded edges, the rectilinear segments progressively increasing in length to the detriment of the rounded edges until the latter disappear.

[0065] More precisely, the first section 26A in contact with the first end 21A of the waveguide body has a substantially circular edge with four rectilinear segments, opposed two by two and regularly distributed, of limited length. The lateral size of the first section 26A is slightly smaller than the lateral size, that is, the diameter, of the waveguide body 21.

[0066] The second section 26A, directly in contact with the first, follows the same external shape, with the difference that the rectilinear segments have a length slightly greater than the rectilinear segments of the first section 26A (fig. 2A). The lateral size of the second section is, in turn, slightly smaller than the lateral size of the first section.

[0067] This pattern is repeated until sections 26A with a rectangular external shape and sizes equal to the sizes of the first port 22 are obtained.

[0068] According to some embodiments, the orthomode transducer 20 also comprises a second transition connector 27 which reciprocally connects the first end 23A of the junction body 23 with the second port 25.

[0069] The second transition connector 27 preferentially comprises a plurality of sections 27A of progressively increasing lateral sizes starting from the junction body 23 to the second port 25. Since both the first end 23A of the junction body and also the second port 25 have a rectangular section, the sections 27A of the second transition connector 27 all have a rectangular shape. However, they could have different shapes, for example if the first end 23A of the junction body and the second port 25 had sections of different shapes.

[0070] The orthomode transducer 20 is equipped with a separator 28, also called dichroic separator 28. Advantageously, the dichroic separator 28 is configured to work not only in polarization, but also in frequency. In other words, the dichroic separator 28 is suitable to separate the electromagnetic signals according to their frequency. In this way, the orthomode transducer 20 can be configured to separate the signals being received from the signals being transmitted.

[0071] The dichroic separator 28 is disposed inside the waveguide body 21 (figs. 2A and 2B) and comprises a dichroic reflection member suitable to selectively reflect a predetermined first frequency band, and to allow the passage of a predetermined second frequency band, with polarization orthogonal with respect to the first frequency band. For example, the first frequency band reflected comprises the interval 17.8-20.2 GHz, corresponding to the frequencies of the signals being transmitted, while a second frequency band made to pass comprises the interval 27.5-30 GHz, corresponding to the frequencies of the signals being received. In this way, the antenna 10 works both in signal reception and also transmission.

[0072] Advantageously, the dichroic separator 28, or dichroic reflection member, comprises a plurality of septa 28A which pass through the waveguide body 21, preferably disposed in a cross-section of the waveguide body 21. In the example shown, the dichroic separator 28 comprises four septa 28A distributed in a cross-section of the waveguide body 21. It is possible to provide a different number of septa 28A, for example five, six, seven or other depending on the frequencies to be reflected.

[0073] According to some embodiments, the septa 28A have a square cross-section. Preferably, and regardless of the shape of their section, the septa 28A are preferably oriented in a predetermined direction, which corresponds to the polarization that couples to the junctions 24 (fig. 2A). The septa 28A and 28B can consist of elements with a square section which, based on the frequencies involved, have a thickness of the order of a few tenths of a millimeter.

[0074] Advantageously, the dichroic separator also comprises a central septum 28B, disposed in a substantially central position with respect to the septa 28A and parallel to them, more preferably also in a central position with respect to the waveguide body 21. Preferably, the central septum 28B extends longitudinally to the waveguide body 21, and has a greater length than the septa 28A.

[0075] According to some embodiments, the central septum 28B has a thickness equal to that of the elements 28A with a square section and a length, deriving from the frequencies of the waves involved, of less than 10 mm.

[0076] This central septum 28B has the function of widening the frequency band coupled to the junctions 24 connected with the transmitter.

[0077] Preferably, the dichroic separator 28 is located between the first end 21A of the body and the longitudinal end of the junction zones 21C facing toward the first end 21A of the waveguide body 21. More preferably, the dichroic separator 28 is disposed in correspondence with the longitudinal end of the junction zones 21C facing toward the first end 21A of the waveguide body 21, as in the example shown (fig. 2A and 2B).

[0078] The antenna 10 for satellites also comprises a polarizer 30. This polarizer is connected directly to the orthomode transducer 20, more precisely to the second end 21B of the waveguide body 21, as shown in fig. 1.

[0079] The polarizer 30 comprises an elongated body 30A with a circular or square section, preferably square (fig. 3, 3A). In the example shown, the body 30A of the polarizer 30 is a parallelepiped with a square section.

[0080] The body 30A therefore comprises four longitudinal walls 32 facing each other parallel two by two and possibly two transverse walls 31, at its two ends.

[0081] Advantageously, at least two of the longitudinal walls 32 are corrugated. The two corrugated longitudinal walls 32 are parallel to each other, that is, they are two longitudinal walls 32 opposite each other.

[0082] According to some embodiments, the corrugated longitudinal walls 32 comprise a plurality of transverse septa 34 that extend toward the inside of the hollow body 30A.

[0083] According to some embodiments, the body 30A is defined by a sheet 35 and the corrugated longitudinal walls 32 each comprise a plurality of grooves 33, or recesses made in the sheet 35 and defining the transverse septa 34.

[0084] The transverse septa 34 are disposed parallel to each other, even more preferably they are disposed parallel to the transverse surfaces 31 of the body 30A of the polarizer 30 (figs. 3, 3A).

[0085] The septa 35 act as inductive elements for parallel polarization and as capacitive elements for orthogonal polarization, with respect to the extension of the body 30A of the polarizer 30. We wish to point out that the signals pass through the polarizer in its length, since the polarizer 30 is disposed in the antenna 10 with the longitudinal surfaces 32 parallel to the development axis X (fig. 1). The number and shape of the transverse septa 34 have an impact on the axial ratio in the transmission and reception modes, which has to be equal to, or in any case as close as possible to, 1.

[0086] Preferably, the transverse septa 34 have a rectangular section, although it is possible to provide transverse septa having a section of a different shape, for example with beveled corners, semicircular, triangular or other.

[0087] The transverse septa 34 are at least three. More generally, the plurality of transverse septa 34 provides two end septa 34A and one or more central septa 34B, depending on the total number of transverse septa 34. In the example shown, the transverse septa 34 are nine, and have two end septa 34A and one central septum 34B (figs. 3, 3A).

[0088] The number of possible grooves 33 corresponds to that of the transverse septa 34, so that in this case there are two end grooves 33A and one central groove 33B.

[0089] The number of septa 34/grooves 33 depends on the total frequency bandwidth, in reception Rx and transmission Tx, in order to guarantee a low level of cross-polarization between them. Obviously, in the case of an even number of septa 34/grooves 33, there are two central septa/grooves 34B/33B.

[0090] According to some embodiments, the septa 34 have a length, that is, a depth, which varies progressively starting from the end septa 34A to the central septum 34B. More preferably, the lengths of the septa 34/grooves 33 vary symmetrically with respect to the central septum/groove 34B, 33B. Even more preferably, the end septa 34A have a shorter length than the others, and the central septum (or the central septa if there are two) 34B has a greater length than the others. Even more preferably, the length of the transverse septa 34 varies exponentially; however, it can vary according to different profiles, for example linearly.

[0091] It should be noted that with this shape of the polarizer 30, the linearly polarized waves that emerge from it are oriented along a diagonal of the transverse surfaces 31. It is therefore particularly preferable to provide that the polarizer 30 is connected to the transducer 20 so that the longitudinal surfaces 32, in particular the corrugated ones, are inclined with respect to the directions of the ports 22, 25, that is, the direction D1 or the direction D2, preferably by an angle equal to 45°, as shown in fig. 1.

[0092] The antenna 10 also comprises an interception member 40, shown in figs. 4A and 4B. During use, the interception member is connected to the polarizer 30.

[0093] The interception member 40, the function of which is to intercept the electromagnetic signals to be received, substantially has an elongated concave shape.

[0094] The interception member conveniently comprises a connection element 41, for example of tubular shape, suitable to connect with the polarizer 30. The interception member 40 also comprises a body 42 in the shape of a paraboloid with a circular cross-section, and which extends from the connection element 41. This connection element 41 is disposed at the smaller end of the paraboloid.

[0095] According to some embodiments, the body 42 has a first portion 42A, proximal to the connection element 41, and a second portion 42B, distal with respect to the connection element 41 (fig. 4B). The first portion 42A has a curved profile with concavity facing toward the inside of the interception member. The second portion 42B, on the other hand, has a substantially rectilinear or curved profile but with a radius of curvature smaller than the radius of curvature of the first portion 42A. Preferably, the second portion 42B extends in the continuity of the first portion 42A, so as to give the interception member its paraboloid shape.

[0096] The body 42 comprises an internal surface 43, advantageously corrugated, and an external surface 44. More precisely, the internal surface 43 comprises a plurality of circumferential fins 45 which protrude transversely from the internal surface 43. Preferably, the fins 45 are disposed orthogonally to the longitudinal axis of the body 42 of the interception member 40, which during use coincides with the development axis X of the antenna 10.

[0097] The fact of providing a corrugated internal surface 43 allows to minimize the spurious conversion modes and to optimize input matching.

[0098] Advantageously, the fins 45 are distributed over the entire length of the internal surface 43 of the body 42 and define between them some hollows with a width substantially equal to the width of the fins 45. The number of fins 45 is preferably comprised between 20 and 150, more preferably between 30 and 110, even more preferably between 40 and 80.

[0099] The fins 45, which produce a succession of teeth and hollows, have sizes that depend on the working frequency and on the manufacturing techniques. For example, the hollows can have depths between 10 and 5 mm and thicknesses comprised between 1 and 2 mm.

[0100] According to some embodiments, the diameter of the connection element 41 is comprised between 5 and 20 mm, the diameter of the aperture opposite the connection element is comprised between 75 and 110 mm, and the length of the interception member 40 is comprised between 120 and 170 mm.

[0101] As can be seen from fig. 1, the orthomode transducer 20 (more precisely, its waveguide body 21), the polarizer 30 and the interception member 40 are reciprocally connected with their longitudinal axes aligned, so as to define the development axis X of the antenna 10.

[0102] According to some embodiments, the antenna 10 also comprises a first waveguide transition 50, shown in detail in fig. 5A. This first waveguide transition 50 serves to reciprocally connect the polarizer 30 and the waveguide body 21 of the orthomode transducer 20.

[0103] Advantageously, the first waveguide transition 50 comprises a plurality of sections 51, 52, 53 with an external shape that varies progressively between the shape of the section of the polarizer and the shape of the section of the waveguide body 21. In this specific case, since the polarizer 30 has a square section and the waveguide body 21 of the orthomode transducer 20 has a circular section, the sections 50A have a shape that varies progressively from square to circular.

[0104] More precisely, in the example shown, the first waveguide transition 50 comprises a first section 51, a second section 52 and a third section 53.

[0105] The first section 51 is located adjacent to the polarizer 30. The first section 51 has a square external shape with beveled corners 51A. The first section 51 therefore has rectilinear segments 51B at its sides with a length greater than half the length of the sides of the square section of the polarizer 30.

[0106] The second section 52 is located adjacent to the first section 51. It substantially follows the shape of the first section 51, that is, it has a substantially square shape with beveled corners 52A. The rectilinear segments 52B at the sides of the square of the second section 52 have a shorter length than the rectilinear segments 51B of the first section 51, preferably smaller than half the length of the sides of the section of the polarizer 30.

[0107] The third section 53, located adjacent both to the second section 52 and also to the second end 21B of the waveguide body 21 of the orthomode transducer 20, has a substantially circular shape, corresponding to a square shape with beveled corners 53A and rectilinear segments 53B of reduced length, for example smaller than one tenth of the length of the side of the square section of the polarizer 30.

[0108] It should be noted that in the example shown, the polarizer 30 and the waveguide body 21 of the orthomode transducer 20 have a lateral size (that is, the length of the side of the square section for the polarizer 30, and the diameter of the circular section for the waveguide body 21) substantially equal to each other. Therefore, the sections 51, 52, 53 of the waveguide transition 50 all have the same lateral size.

[0109] In the event the lateral sizes of the polarizer 30 and of the waveguide body 21 were different, it would be preferable to provide that the sections 51, 52, 53 have different lateral sizes and disposed in such a way as to vary progressively from the lateral size of the polarizer to the lateral size of the waveguide body 21.

[0110] With a waveguide transition 50 as described above, it is possible to minimize the sizes, and in the meantime optimize the input matching of the signal.

[0111] According to some embodiments, the antenna 10 comprises a second waveguide transition 60 located between the polarizer 30 and the connection element 41 of the interception member 40 (fig. 5B). Since the connection element 41 has a circular section, the second waveguide transition is completely analogous to the first waveguide transition, and will therefore not be described. The same components have the same numbering as the first waveguide transition 50, to which 10 has been added.

[0112] The functioning of the antenna 10 as described above is described below.

[0113] In a signal reception mode, the signal is first intercepted by the interception member 40 and is directed along the body 42 toward the connection element 41. We wish to point out that the received signal has circular polarization.

[0114] After passing through the second waveguide transition 60, the signal passes through the polarizer 30, in which it is converted into two signals with linear polarizations perpendicular to each other.

[0115] The two signals with linear polarization then pass through the first waveguide transition 50 and reach the waveguide body 21 of the orthomode transducer 20.

[0116] Since it is a received signal, therefore with a frequency comprised between 27.5 and 30 GHz, the signal passes through the dichroic separator and arrives at the first port 22, where it is then made to pass into the electronic circuit.

[0117] In transmission mode, the signal originates from the same electronic circuit and is fed into the orthomode transducer 20 through its second port 25.

[0118] The signal, consisting of two signals with linear polarizations perpendicular to each other, passes through the junction body 23 and passes through the two junctions 24 to arrive at the waveguide body 21. From here, since it is a signal with a frequency comprised in the interval 17.8-20.2 GHz, it is totally blocked and reflected by the dichroic separator 28. This causes the signal to be fully oriented toward the polarizer 30, where it is then converted into a signal with circular polarization.

[0119] The signal then arrives at the interception member 40, from where it is then sent to the outside.

[0120] It is clear that modifications and/or additions of parts may be made to the orthomode transducer and to the antenna as described heretofore, without departing from the field and scope of the present invention as defined by the claims.

[0121] It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of orthomode transducer and/or antenna, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby. In the following claims, the sole purpose of the references in brackets is to facilitate reading: they must not be considered as restrictive factors with regard to the field of protection claimed in the specific claims.


Claims

1. Orthomode transducer (20) for an antenna (10), comprising:

a waveguide body (21), extended along a longitudinal axis, between a first end (21A) and a second end (21B), said second end (21B) being suitable to be connected to other components of the antenna (10),

a first port (22) connected to said first end (21A) of the waveguide body (21) and suitable to be connected to an electronic circuit,

a junction body (23) equipped with a first end (23A), facing the first end (21A) of the waveguide body (21), and a second end (23B), facing the second end (21B) of the waveguide body (21),

at least one junction (24) connected both to said junction body (23), and also to said waveguide body (21) in correspondence with a junction zone (21C),

a second port (25) connected to the first end (23B) of the junction body (23), and suitable to be connected to an electronic circuit,

characterized in that it comprises a separator (28) disposed inside the waveguide body (21) and configured to separate frequencies.


 
2. Orthomode transducer (20) as in claim 1, characterized in that the separator (28) comprises a reflection member suitable to selectively reflect a predetermined frequency band.
 
3. Orthomode transducer (20) as in claim 1 or 2, characterized in that the separator (28) comprises a plurality of septa (28A) that pass through the waveguide body (21) in a cross-section of said waveguide body (21).
 
4. Orthomode transducer (20) as in claim 3, characterized in that the separator (28) comprises a central septum (28B) located in a central position with respect to the waveguide body (21) and having a greater extension, measured longitudinally to said waveguide body (21), than the other septa (28A).
 
5. Orthomode transducer (20) as in any claim hereinbefore, characterized in that the first port (22) and the second port (25) each comprise an end surface (22A, 25A) disposed parallel to each other, wherein the end surface (22A) of the first port (22) has an extension axis oriented in a first direction (D1), and the end surface (25A) of the second port (25) has an extension axis oriented in a second direction (D2) orthogonal to said first direction (D1).
 
6. Orthomode transducer (20) as in any claim hereinbefore, characterized in that it comprises two junctions (24) which connect the junction body (23) with the waveguide body (21), said two junctions (24) being symmetrical to each other with respect to a symmetry plane which comprises the longitudinal axis of said waveguide body (21).
 
7. Orthomode transducer (20) as in claim 6, characterized in that the junctions (24) connect to the waveguide body (21) in correspondence with two junction zones (21C), and that said two junction zones (21C) are disposed symmetrically to each other with respect to the longitudinal axis of said waveguide body (21).
 
8. Antenna (10) for satellites, comprising an orthomode transducer (20) equipped with a first port (22) and a second port (25) which are suitable to be connected to an electronic circuit, a polarizer (30) connected to said orthomode transducer (20) and an interception member (40) connected to said polarizer (30), characterized in that the polarizer (30) comprises a square section body with four longitudinal surfaces (32), at least two of which are corrugated, said polarizer (30) being connected to the orthomode transducer (20) so that said corrugated longitudinal surfaces (32) are inclined with respect to the direction of the ports (22, 25) by an angle equal to 45°.
 
9. Antenna (10) as in claim 8, characterized in that the corrugated longitudinal surface (32) comprises a plurality of transverse septa (34) parallel to each other, which extend inside the body (30A) of the polarizer (30), of which two end septa (34A) and at least one central septum (34B), said septa (34) having a progressively variable depth going from one of said end septa (34A) to said central septum (34B).
 
10. Antenna (10) as either claim 8 or 9, characterized in that the transverse septa (34) have a rectangular section.
 
11. Antenna (10) as in any claim from 8 to 10, characterized in that the interception member (40) has a paraboloid-shaped body (42) comprising a corrugated internal surface (43).
 
12. Antenna (10) as in claim 11, characterized in that the internal corrugated surface (43) comprises a plurality of circumferential fins (45) which protrude transversely from said internal surface (43) and which are disposed orthogonally to the longitudinal axis of the body (42) of the interception member (40).
 
13. Antenna (10) as in any claim from 8 to 12, characterized in that the orthomode transducer (20) comprises a waveguide body (21), extended along a longitudinal axis, between a first end (21A) and a second end (21B), said second end (21B) being suitable to be connected to other components of the antenna (10), the first port (22) being connected to said first end (21A) of the waveguide body (21),
a junction body (23) equipped with a first end (23A), facing the first end (21A) of the waveguide body (21), and a second end (23B), facing the second end (21B) of the waveguide body (21),
at least one junction (24) connected both to said junction body (23) and also to said waveguide body (21) in correspondence with a junction zone (21C),
the second port (25) being connected to the first end (23B) of the junction body (23), and in that the polarizer (30) is connected to the second end (21B) of the waveguide body (21).
 
14. Antenna (10) as in claim 13, characterized in that the orthomode transducer (20) comprises a separator (28) disposed inside the waveguide body (21) and configured to separate frequencies.
 
15. Antenna (10) as in claim 13, characterized in that the separator (28) comprises a reflection member suitable to selectively reflect a predetermined frequency band.
 




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Cited references

REFERENCES CITED IN THE DESCRIPTION



This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description