Note: Descriptions are shown in the official language in which they were submitted.
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ULTRA-COMPACT E/H HYBRID COMBINER, NOTABLY FOR A SINGLE-
REFLECTOR MFB ANTENNA
Description
[1] The invention relates to the general field of communication satellites,
and in
particular to multibeam antennas fitted to these satellites.
[2] The invention relates more specifically to antenna beamforming in the
context of
the use of MFB (or "Multiple Feed per Beam") antennas.
[3] In the context of the development of current and future communication
satellites,
such as V-HT multibeam Ka-band satellites, the targeted geographic coverage is
becoming increasingly extensive. Furthermore, since the number of users and
therefore the capacity required for these satellites is constantly increasing,
there is
an increasingly pressing need to have antennas capable of radiating several
hundred beams, typically a number of beams greater than five hundred.
[4] There is also a need to have antennas capable of covering geographical
areas with
a fine resolution (small spots), that is to say capable of forming beams with
a small
angular aperture.
[5] Such coverage that is both dense and extensive is incompatible, for
technical
reasons, with SFB (i.e. "Single Feed per Beam") passive antenna solutions with
multiple reflectors. It is however made possible by implementing single-
reflector
MFB (i.e. "Multiple Feed per Beam") antennas.
[6] The applicant has developed a single-reflector MFB antenna solution, used
at
transmission and at reception, allowing a large number of thin beams to be
produced. This solution is based on an antenna architecture consisting of sub-
arrays of 4 bipolarization elements (Tx/Rx) that make it possible to generate
rectangular beams using a slightly overdimensioned reflector, a reflector
whose
size is typically overdimensioned by 15%.
[7] By virtue of using sub-arrays with 4 bipolarization radiating elements
(Tx/Rx),
preferably four horns with a circular aperture, it is possible, using an
antenna with
a single reflector, to generate rectangular beams (Tx/Rx) in a number surf
icient to
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provide coverage of a given geographical area by way of a plurality of
rectangular
spots.
[8] Such an architecture is formed by way of an assembly of distribution
modules, each
comprising an RF chain (transmitter and receiver) and means for connecting the
RF chain to a plu rality of horns, these horns being arranged so as to be able
to be
combined to form a single beam.
[9] These distribution modules form a network consisting of intertwined meshes
to
which the horns are connected so that their apertures are arranged in a
radiating
plane.
[10] The structure and the geometry of the distribution modules are defined
such
that the horns connected to one and the same distribution module are arranged
such that the recombination of the beams from the horns connected to one and
the
same module forms a single beam, associated with a spot in the covered
geographical area.
[11] The schematic illustration in figure 1 shows, by way of example, a
partial view
of a single-reflector MFB antenna architecture intended to cover a
geographical
area divided into rectangular elementary spots (rectangular mesh of the
covered
area).
[12] The MFB antenna under consideration here is built around a network of
distribution modules 11 configured such that the horns 12 associated with one
and
the same distribution module are arranged at the vertices of a diamond, so as
to
be able to be combined to form a beam covering a given spot.
[13] Such an antenna structure advantageously makes it possible to form highly
focused antenna beams from radiating horns 12 having small-diameter apertures.
[14] As may be seen in the basic diagram in figure 2, each radiating horn of
the
antenna thus formed is connected, at transmission and at reception, to two
distribution modules corresponding to two separate beams, except for the horns
covering the periphery of the geographical area, which are connected to just
one
module. Thus, in the illustration in figure 2, the reception module R
associated with
the horn 211 is connected to the reception paths 22 and 23 corresponding to
the
beams n and m by the distribution modules 24 and 25.
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[15] Moreover, each distribution module is used to distribute the signal
corresponding to one and the same beam over four RF chains, each chain
comprising a radiating horn.
[16] As such, in a known manner, a distribution module for coupling, at
transmission,
a given beam into the RF chains served by this beam consists of a power
divider
module formed of couplers that are arranged in two stages that are connected
to
one another by connection interfaces, such as waveguides for example.
[17] In the same way, a distribution module for coupling, at reception, a
given beam
into the RF chains served by this beam consists of a power summer module
formed
of couplers that are arranged in two stages that are connected to one another
by
connection interfaces, such as waveguides for example.
[18] From a structural point of view, whether it is intended for a
transmission path or
a reception path, a distribution module is structured in two stages, as
illustrated by
the diagram in figure 3.
[19] The first coupling stage comprises a coupler 31, while the second
coupling
stage comprises two couplers 32 and 33.
[20] In the case of a distribution module situated in a beam reception path,
the
couplers 31, 32 and 33 operate as sum mers.
[21] The two couplers 32 and 33 in the second stage each sum the power, in
pairs,
of the signals RX1 to RX4 delivered by the reception paths of the four
transmission/reception modules served by a given beam.
[22] The coupler 31 for its part combines the summation signals delivered by
the
couplers 32 and 33 and delivers a sum signal RX.
[23] In the same way, in the case of a distribution module situated in a beam
transmission path, the couplers 31, 32 and 33 operate as power dividers.
[24] The coupler 31 receives the signal to be transmitted, corresponding to
the beam
under consideration, and divides it into two signals that are transmitted to
the
couplers 32 and 33, respectively.
[25] The two couplers 32 and 33 in the second stage in turn divide the
received
signal into two signals. Each coupler thus delivers, to each of the
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transmission/reception modules to which it is connected, a transmission signal
corresponding to the signal carried by the transmission path of the beam under
consideration.
[26] Generally speaking, from an implementation point of view, the couplers
31, 32
and 33 forming a distribution module are produced in the form of cavities and
con nected to one another by way of wavegu ides 34.
[27] Thus, as may be seen, producing a single-reflector MFB antenna such as
the
one described above requires, to produce ail of the necessary distribution
modules,
using a large number of coupling devices and of connection elements between
the
various couplers, on the one hand, and between these couplers and the RF chain
and the horns, on the other hand.
[28] it may furthermore also be seen that installing such distribution
networks results
in significant intertwining of the various elements.
[29] Therefore, if the compactness of the radiating source of a satellite
antenna and
the large number of horns that such a source may comprise are taken into
consideration, it may prove tricky to install ail of the distribution modules
necessary
to produce a single-reflector MFB satellite antenna.
[30] At the present time, one solution that is used to optimize the bulk
exhibited by
the beam distribution system is that of producing distribution modules formed
from
molds in the form of half-shells that are assembled to form a set of cavities
that are
arranged so as to implement ail of the (coupling and connection) functions
performed by the module. However, due to the intertwining of the various
distribution modules in such a structure, the molded elements that are
produced
mean that the half-shells have to adopt a tiled configuration with respect to
one
another, such that each distribution module thus produced is not physically
independent of the neighboring modules. Such mechanical interdependence
complicates the mounting or dismounting of a module, as well as the overall
assembly.
[31] Moreover, producing distribution modules in the form of molded parts
forming
a highly intertwined assembly makes it difficult to contemplate integrating
additional
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functionalities, such as deviation measurement functions, which requires an
appropriate combination of the received signais.
[32] One aim of the invention is to propose a device for making it easier and
more
economical in terms of bulk to produce distribution modules such as those
5 described above.
[33] Another aim of the invention is to propose a device for implementing
additional
functionalities, such as the formation of deviation measurement paths.
[34] To this end, one subject of the invention is a reciprocal compact E/H
hybrid
combiner-divider for coupling or splitting electromagnetic waves, comprising
at
1.0 least one primary waveguide and two secondary waveguides, the primary
waveguide and the secondary waveguides each having a parallelepipedal
structure of rectangular cross section with two ends; characterized in that
the
primary waveguide and the secondary waveguides form a one-piece structure in
which:
- the primary waveguide has a first end configured so as to form an
input/output
port and a second end defining an aperture;
- the secondary waveguides having the same configuration and substantially
identical dimensions, each secondary waveguide having two ends configured so
as to form two input/output ports, and a side aperture formed on one of the
small
faces of the waveguide;
- the secondary waveguides are arranged facing one another and facing the
primary waveguide so as to form, with one of their side faces, a common side
wall;
- the secondary waveguides are arranged facing the primary waveguide such
that
the side apertures are situated facing the aperture formed by one of the ends
of
the primary waveguide and that the common wall is aligned with the central
axis of
the aperture of the primary waveguide.
[35] According to some particular embodiments, the E/H hybrid combiner-divider
comprises one or more of the following features, taken individually or in
combination:
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- each of the secondary waveguides comprises an internat conductive element
situated in the cavity of the waveguide and in electrical contact with the
watt of the
guide, said internat conductive element being arranged inside the waveguide so
as
to optimize the matching of the impedance of the guide and the combination or
the
division of the waves traveling through the guide;
- the internat conductive element is a pin fixed in a substantially central
position on
the inner face of the upper watt of the guide;
- the internat conductive element is formed by a watt projecting into the
guide,
situated transversely in a substantially central position on the inner face of
the
1.0 upper watt of the guide, the height of said projection being
substantially less than
the height of the guide;
- the E/H hybrid combiner-divider furthermore comprises two tertiary
waveguides
situated transversely with respect to each of the secondary waveguides and
joined
thereto, each tertiary waveguide having a parallelepipedal structure of
rectangular
cross section with two ends, a first end configured so as to form an input-
output
port and a second end forming an aperture situated facing an aperture formed
in
the side watt of each secondary waveguide opposite the common watt, in a
substantially central position, said aperture being configured so as to put
each
secondary waveguide in communication with a tertiary waveguide situated
transversely with respect thereto, so as to achieve H-plane coupling, the com
biner-
divider thus having an E/H hybrid tee structure.
[36] Another subject of the invention is a beam distribution network for a
multiple
feed per beam (MFB) antenna, characterized in that it comprises a first group
and
a second group of hybrid combiner-dividers as defined above, each combiner-
divider of the first group acting as a combiner being connected, via its
secondary
ports, to the reception paths of four radiating sources and to a beam
reception path
via its primary port; each combiner-divider of the second group acting as a
combiner being connected, via its secondary ports, to the transmission paths
of
four radiating sources and to a beam transmission path via its primary port.
[37] According to one particular embodiment, the beam distribution network for
a
multiple feed per beam (MFB) antenna comprises the following features:
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- the combiner-dividers of the first group are combiner-dividers as defined
above
whose ancillary output ports are connected to a deviation measurement device.
[38] Another subject of the invention is an (MFB) beamforming array antenna,
characterized in that it comprises a plurality of radiating sources combined
into
groups of four radiating sources, the reception paths and the transmission
paths of
the radiating sources belonging to one and the same group being connected,
respectively, to the secondary ports of a combiner-divider whose primary port
is
connected to the reception path of a beam and to the secondary ports of a
combiner-divider whose primary port is connected to the transmission path of
the
same beam.
[39] The present invention that is proposed advantageously largely solves the
problem of intertwining of BFNs in the single-reflector solution.
[40] The E/H hybrid component according to the invention makes it possible to
combine 4 radiating elements in a small footprint limited, in the xy plane, to
the
access guide.
[41] It advantageously integrates, within one and the same structure, an E-
plane
divider for forming a sum path and two H-plane dividers for forming difference
paths.
[42] It also has the property of making it possible to adapt the power sharing
between the input port shared by the various paths and the output ports.
[43] It also offers the capability, within the network and for any spot, to
implement a
deviation measurement function (by using the sum and difference paths) in
addition
to the TLC (beamforming) functions by combining two magic tees, coupled to an
E-plane divider, into just one and the same 1:6 (one input and six outputs)
com panent.
[44] The features and advantages of the invention will be better appreciated
by
virtue of the following description, which description draws on the appended
figures,
in which:
[45] [fig 1] shows an illustration of one example of combining four radiating
sources
in a diamond-shaped arrangement so as to form a beam;
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[46] [fig. 2] shows an overview of the interconnection of the radiating
elements
forming the radiating source of an MFB antenna with a reflector by way of
distribution module modules;
[47] [fig. 3] shows a schematic illustration of a distribution module
according to the
prior art;
[48] [fig. 4] shows an illustration showing an overall perspective view of the
distribution module according to the invention, in a basic form;
[49] [fig. 5] shows an illustration showing a partial view from below of the
distribution
module according to the invention illustrated by figure 4, along a plane
passing
through the open end of the primary waveguide;
[50] [fig. 6] shows an illustration showing a partial view from above of the
distribution
module according to the invention illustrated by figure 4;
[51] [fig. 7] shows an illustration showing an overall perspective view of the
distribution module according to the invention, in a second embodiment taken
as
an example;
[52] [fig. 8] shows an illustration showing a partial perspective and
transparent view
of the distribution module according to the invention in the embodiment of
figure 7;
[53] [fig. 9] shows an illustration showing a transparent view from above of
the
distribution module according to the invention, in the embodiment of figure 7;
[54] [fig. 10] shows an illustration showing a partial perspective and
transparent view
of the distribution module according to the invention in a third embodiment
allowing
the creation of deviation measurement signais;
[55] [fig. 11] shows an illustration showing a transparent view from above of
the
distribution module according to the invention illustrated by figure 10;
[56] [fig. 12] shows an illustration showing a side view, in partial cross
section, of
the distribution module according to the invention in the embodiment
illustrated by
figure 108.
[57] It should be noted that, in the appended figures, the same functional or
structural element preferably bears the same reference symbol.
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[58] The remainder of the text presents the technical features of the
invention with
reference ta figures 4 and 5, which show the device in its basic version; and
then
with reference firstly ta figures 6 ta 9 and secondly ta figures 10 ta 12,
which show
the device in two particular embodiments.
[59] Figures 1 ta 3, already commented upon in the preamble of the
description, are
not the subject of specific developments.
[60] As illustrated in figures 4 ta 7, the device according ta the invention,
a hybrid
combiner-divider, comprises a primary waveguide 41 and two secondary
waveguides 42 and 43.
[61] The primary waveguide 41 has two ends: a first end configured sa as ta
form
an input-output port 48, a primary input-output port, allowing the device ta
be
connected ta a signal distribution network, a beam distribution network for a
multiple feed antenna such as the one described above and illustrated by
figure 2
for example, and a second end forming an aperture 61, located at the other end
of
the guide 41.
[62] The two secondary waveguides 42 and 43 each have two opposing ends that
are configured sa as ta form two input-output ports, the ports 44 and 45 for
the
waveguide 42 and the ports 46 and 47 for the waveguide 43, respectively.
[63] Each of the guides 42 and 43 also has an aperture 62 or 63, arranged on
one
of its small side faces, as illustrated more specifically in the schematic
view from
below in figure 5. These apertures make it possible ta put the cavity of the
primary
guide 41 in communication with the cavity of the secondary guide 42 or 43
under
consideration.
[64] It should be noted here that the expression "small side face" refers ta
the fact
that the secondary guides 42 and 43 are parallelepipedal guides with a
rectangular
cross section and that, as such, each guide has four side faces:
- two rectangular side faces ("large faces") whose length is equal ta the
length of
the guide and whose width is equal ta the large side of the rectangle defining
the
cross section of the guide;
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- two rectangular side faces ("small faces") whose length is equal ta the
length of
the guide and whose width is equal ta the small side of the rectangle defining
the
cross section of the guide.
[65] From a structural point of view, the device according ta the invention
takes the
5
form of a one-piece element having three guides that are joined ta one another
41,
42 and 43.
[66] In this structure, the two secondary guides 42 and 43 are arranged
against one
another and joined ta one another by one of their large faces, such that the
two
faces in contact form a common partition 51 separating the internai cavities
of the
10 two guides from one another.
[67] Moreover, the two secondary guides are arranged facing one another such
that
the apertures 62 and 63 are situated side by side in one and the same plane,
such
that they form two contiguous apertures having a common edge formed by the
edge of the partition 51.
[68] According ta the invention, the primary guide 41 is arranged facing the
block
formed by the two secondary guides 42 and 43, such that the aperture 61 formed
by its open end is positioned facing the double aperture formed by the two
contiguous openings 62 and 63 of the secondary guides 42 and 43. The two
cavities of the guides 42 and 43 thereby open into the cavity of the guide 41.
[69] Moreover, from a structural point of view, the wall of the primary guide
41 is
joined, at the apertures 62 and 63, ta the two secondary guides 42 and 43. The
device according ta the invention thereby has a one-piece structure with a
primary
input-output port 48 and four secondary input-output ports 44-45 and 46-47.
[70] From a dimensional point of view, the respective dimensions of the
primary
waveguide 41 and of the secondary waveguides 42 and 43, the widths and heights
primarily defining the cross sections of the guides, and the dimensions of the
apertures 61, 62 and 63, are defined such that the primary waveguide 41 forms
an
E-plane coupler with each secondary waveguide, the sum of the waves traveling
through each secondary guide being equal ta the wave traveling through the
primary waveguide 41. The com mon partition 51 that separates the two cavities
61
and 62 here advantageously acts as a divider-com biner.
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[71] From a functional point of view, when it is integrated into a
transmission chain,
the device according to the invention, a reciprocal device, advantageously
acts as
a hybrid device that distributes, in two integrated stages, an incident wave
entering
via the primary port 48 onto the four secondary ports. It thus advantageously
behaves like an integrated divider (power splitter) with one input and four
outputs.
[72] Conversely, when it is integrated into a reception chain, the device
according
to the invention also advantageously acts as a hybrid device that recombines,
in
two integrated stages, four incident waves entering via each of the secondary
input-output ports 44-45 and 46-47 into a single wave delivered by the primary
input-output port 48.
[73] Figures 8 and 9 illustrate a second embodiment, which is a structural
variant of
the basic version of the device according to the invention described above.
[74] It is also known that, in an E-plane coupler formed by a first waveguide
having
one end forming an aperture opening onto the side wall of a second waveguide
and forming an E-plane divider, the wave transmitted by the first waveguide to
the
second waveguide is divided into two waves optimally in that the impedance
matching of the second waveguide is good. However, in general, a conductive
element of height h is for this purpose situated inside the second guide in a
central
position with respect to the length L of the guide, this conductive element
being
connected, via one of its ends, to the wall of the guide.
[75] The embodiment in figures 8 and 9 incorporates this consideration and
integrates, into each of the secondary guides 42 and 43, a transversely
oriented
conductive partition whose height h is determined so as to achieve this
impedance
matching and thus to promote the division of the wave transmitted by the
primary
guide or, conversely, the phase recombination of the waves received via the
secondary input-output ports.
[76] It should be noted here that the conductive partitions 52 or 53 situated
respectively in the secondary waveguides 42 and 43 have a height h
substantially
less than the height of the guides. They do not have a function of closing off
the
cross section of the guide in which each of them is situated. They may
moreover
be replaced with conductive elements having various shapes that project into
the
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guide under consideration and are configured sa as ta ensure good impedance
matching.
[77] Figures 10 ta 12 for their part illustrate a second embodiment of the
device
according ta the invention, which incorporates the structural and dimensional
features of the basic form illustrated by figures 4 ta 8.
[78] However, in this more elaborate embodiment, the device according ta the
invention additionally integrates a structure for forming, at reception,
"difference"
paths that may be used in the context of deviation measurements.
[79] This additional structure consists, as illustrated in particular in
figure 10, of two
complementary tertiary waveguides 81 and 82 that are rectangular and whose
dimensions are matched ta the frequency band of the electromagnetic waves
intended ta travel therethrough.
[80] The guides 81 and 82 are situated transversely on each side of the device
according ta the invention at the secondary guides 42 and 43. In one preferred
embodiment, these tertiary guides are situated in a central position, as
illustrated
by figures 8 to 10.
[81] Each guide has a first end configured sa as ta form an output port 83 or
84, and
a second end via which it is joined ta the secondary guide with which it is
associated, which forms an aperture 91 or 92.
[82] As illustrated by the sectional side view in figure 12, a cross section
passing
through the plane of the side face of the secondary guide 42, this aperture 91
(or
92 for the guide 82) is situated facing a similar aperture formed in the large
face of
the corresponding secondary waveguide 42 or 43 opposite the common face
forming the partition 51.
[83] Each tertiary waveguide 91 or 92 is also dimensioned (length, cross
section) sa
as ta form, with the secondary waveguide 42 or 43 ta which it is attached, an
H-
plane coupler that makes it possible, at reception, ta calculate the
difference
between the waves received via each of the input-output ports, 44-45 or 46-47
respectively, of the secondary waveguide ta which it is joined.
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[84] This additional structure advantageously makes it possible, at reception,
without altering the essential nature of the compactness of the device
according to
the invention, to form both a path, called sum path, for which the signais
transmitted
to the device via the secondary input-output ports 44-47 are combined in
phase,
the resulting signal being delivered via the primary input-output port 48, and
two
paths, called difference paths, for which the signais transmitted to the
device via
the secondary input-output ports 44-45, on the one hand, and 46-47, on the
other
hand, are combined in pairs in phase-to-phase opposition, the difference
signais
being respectively delivered via the input-output ports 83 and 84.
[85] This thereby achieves a device constituting a compact structure forming a
double magic tee (or hybrid tee), which structure, as is known, achieves dual
E-
plane and H-plane coupling.
[86] In this last embodiment, the device according to the invention may thus
advantageously perform two separate functions:
- a primary function of a hybrid combiner-divider with a primary input-output
port
and four secondary input-output ports, the compact combiner-divider thus
formed
being able to be integrated into a beam distribution network for an MFB
antenna;
- a secondary function for forming what are called "difference" paths that are
able
to be used in the context of implementing a functionality called "RF Sensing"
(deviation measurement), which makes it possible, in a known manner, to
measure
the pointing offset of the beam under consideration with respect to the axis
of the
antenna along which this beam travels.
[87] By virtue of the one-piece structure of the device according to the
invention, this
second functionality may be implemented without adding hardware dedicated
specifically thereto.
[88] Generally speaking, the device according to the invention may be produced
using various known methods, which are not presented here, in particular using
methods for producing waveguides and hybrid couplers. It may in particular be
produced by molding or machining in the form of two half-shells and assembling
the half-shells thus produced.
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[89] It should moreover be noted that, as illustrated by the various views
presented
in the appended figures, the primary waveguide may be formed by a simple
straight guide or else by a "twisted" guide, without this changing the
operating
principle of the device, the configuration of the primary guide being
essentially
linked to the arrangement of the various elements forming the distribution
network in which it is integrated.
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