Orthomode transducer

Abstract

An orthomode transducer including a first Boifot junction and a second Boifot junction. Each of the first and second Boifot junctions includes a dual polarized port, a first lateral port, a second lateral port, the first and second lateral port being single polarized, and a third single polarized port along the propagation direction of a signal in the dual polarized port. A first power divider for coupling the first lateral port of the first Boifot junction with the first lateral port of the second Boifot junction to a third port. A second power divider for coupling the second lateral port of the first Boifot junction with the second lateral port of the second Boifot junction to a third port. A third power divider for coupling the third port of the first power divider with the third port of the second power divider to a fourth single polarization port.

Claims

1. An orthomode transducer comprising: a first Boifot junction; a second Boifot junction; each of said first and second Boifot junction comprising a dual polarized port, a first lateral port, a second lateral port, the first and second lateral port being single polarized, and a third single polarized port along the propagation direction of a signal in the dual polarized port; a first power divider for coupling the first lateral port of the first Boifot junction with the first lateral port of the second Boifot junction to a third port of the first power divider; a second power divider for coupling the second lateral port of the first Boifot junction with the second lateral port of the second Boifot junction to a third port of the second power divider; a third power divider for coupling the third port of the first power divider with the third port of the second power divider to a fourth single polarization port; a fourth power divider for coupling the third single polarized port of the first Boifot junction with the third single polarized port of the second Boifot junction to a fifth single polarized port.

2. The orthomode transducer of claim 1, in which the fourth power divider is placed between the first and the second power divider.

3. The orthomode transducer of claim 2, wherein said fourth single polarization port transmits a first linear polarization while said fifth single polarized port transmits a second linear polarization orthogonal to the first polarization.

4. The orthomode transducer of claim 1, comprising two symmetry planes.

5. The orthomode transducer of claim 1, wherein the first and second power dividers are stepped.

6. The orthomode transducer of claim 1, being adapted for one among: C-band satellite communication; X-band satellite communication; Ku-band satellite communication; Ka-band satellite communication; Q-band satellite communication; and/or V-band satellite communication.

7. The orthomode transducer of claim 1, being monobloc, i.e. made out of one single piece.

8. The orthomode transducer of claim 7, comprising a 3D printed core and conductive plated sides.

9. The orthomode transducer of claim 8, comprising a 3D printed conductive core.

10. An antenna array comprising at least one orthomode power divider according to claim 1, and one horn antenna connected to the dual polarized port of each of said Boifot junctions.

11. The antenna array of claim 10, said horn antennas being rectangular horn antennas, preferably stepped rectangular horn antennas.

12. The antenna array of claim 11, said horn antennas having dimensions of 20 mm×40 mm or 10 mm×20 mm.

13. The antenna array of claim 10, said horn antennas being circular horn antennas.

14. The antenna array of claim 10, wherein the separation between said horn antennas in one first direction is smaller than a nominal wavelength and the separation between said horn antennas in one second direction orthogonal to the first direction is smaller than two nominal wavelengths, the nominal wavelength being the wavelength for which the antenna array is designed.

15. The antenna array of claim 10, having two symmetry planes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood with the aid of the description of an embodiment given by way of example and illustrated by the figures, in which:

(2) FIG. 1 shows an exploded view of a Boifot junction, one part of the side walls being removed in the illustration in order to show the septum.

(3) FIG. 2 shows an exploded view of a Boifot junction with a ridged edge, one part of the side walls being removed in the illustration in order to show the septum.

(4) FIG. 3 shows an OMT transducer according to the prior art.

(5) FIG. 4 shows a stack of two OMT transducers according to the prior art.

(6) FIG. 5 shows a stack of two Boifot junctions used in the device of the invention.

(7) FIG. 6 shows a power divider that can be used to couple the first port of a first Boifot junction of FIGS. 1 and 2 with the first port of the second Boifot junction of these Figures (or to couple the second port of the first Boifot junction with the second port of the second Boifot).

(8) FIG. 7 shows a stack of two Boifot junctions according to FIGS. 1 and 2 coupled through two power dividers according to FIG. 6.

(9) FIG. 8 shows a stack of two Boifot junctions according to FIGS. 1 and 2 coupled through two power dividers according to FIG. 6, the output port of those power dividers being coupled through another power divider.

(10) FIG. 9 shows a complete orthomode transducer with beamforming capabilities, including a stack of two Boifot junctions according to FIGS. 1 and 2 coupled through two power dividers according to FIG. 6, the output port of those power dividers being coupled through another power divider, the orthogonal output being bended.

(11) FIG. 10 shows another embodiment of a complete orthomode transducer with beamforming capabilities, including a stack of two Boifot junctions coupled through two power dividers that are twisted, the output port of those power dividers being coupled through another power divider, both outputs being bended.

(12) FIGS. 11 and 12 are two different views of an arrangement of two orthomode transducers (each with two Boifot junctions), the orthogonal outputs of each transducer being combined through a power divider.

(13) FIG. 13 shows an antenna array using such four orthomode transducer with beamforming capabilities, being connected with each other by means of a series of power dividers, bends and waveguide twists.

DETAILED DESCRIPTION OF POSSIBLE EMBODIMENTS OF THE INVENTION

(14) FIG. 5 shows a stack of two Boifot junctions 10 that could be used in an orthomode transducer of the invention. Those Boifot junctions could be conventional and correspond to the above described junctions of FIG. 1 or 2 for example.

(15) Each Boifot junction (FIGS. 1 and 2) 10 presents two symmetry planes: one horizontal symmetry plane (horizontal on the Figure, and parallel to the septum 5 or ridged wedge 6), and one vertical symmetry plane (vertical on the figure, and perpendicular to the septum).

(16) Any of the illustrated Boifot junction 10 has four ports. The port 1 propagates two orthogonal polarizations (TE10-Vpol, TE01-Hpol). We will call this port the input port, although the junction is reversible and could be used in both directions, either in a receiver or in a receiver. The port 1 could have a waveguide with a rectangular section, or any other section that propagate purely degenerate modes. Symmetric geometries that propagate two modes in the desired frequency band are preferred because they are broadband.

(17) A septum 5 acts as polarization filter and splits the TE01 mode into two halves towards the output ports 3 and 4 (lateral ports), while the TE10 mode gets choked towards the output port 2 (through port). The three ports 2,3,4 propagate only one polarization. The output through port 2 is placed along the propagation direction, with its broader side horizontally aligned on the figure, and in opposition to the dual polarized port 1. The two lateral ports 3,4 have their broader sides vertically aligned and are placed perpendicular to the propagation direction.

(18) The septum 5 is preferably ridged. Ridged septums are known as such, but usually only used for very high frequencies, well above the KU/Ka frequency bands. As will be described, they are preferably made (as the rest of the component) by 3D printing, such as stereolithography, or selective laser sintering or selective laser melting which makes them easier to manufacture.

(19) The septum is optional and orthomode transducers comprising other type of polarization filters could be considered.

(20) The section of the output ports 2, 3 and 4 is preferably rectangular; other sections, preferably with two symmetry planes, are preferably used.

(21) FIG. 6 shows a power divider 8 used to couple the first lateral port 3 of the first Boifot junction of the FIG. 5 with the first lateral port 3 of the second Boifot junction of FIG. 5. A second, identical power divider 8 is used to couple the second lateral port 4 of the first Boifot junction of FIG. 5 with the second lateral port 4 of the second Boifot junction. The power divider 8 are preferably stepped because of their broader bandwidth and compactness. This power divider can be either of symmetric power distribution or of asymmetric power distribution, depending on the further required beam. Each power divider 8 has two inputs 81 for receiving the signal from the lateral outputs 3 or 4 of the Boifot junction, and one output 80 that combines the two input signals. Again, this component is reversible and the designation of “power divider” instead of “power coupler”, and “input” instead” of “output” is only used in order to distinguish those elements in this text, without any implications as to the sense of transmission of the signal.

(22) FIG. 7 shows an assembly comprising the two stacked Boifot junctions of FIG. 5 with their lateral ports 3 respectively 4 connected through the power dividers 8. As can be seen, the two lateral ports 3 of the upper and lower Boifot junctions are connected through one first power divider while the two other lateral ports 4 of the upper and lower Boifot junctions are connected through another power divider.

(23) FIG. 8 shows a complete orthomode transducer with beamforming capabilities based on the assembly of FIG. 7. It has two symmetry planes, one horizontal and one vertical. The symmetry planes concern only the empty path for the wave signal inside the component; the external sides do not need to be symmetrical.

(24) In the component of FIG. 8, the two outputs 80 of the power dividers 8 are coupled through another power divider 9 with one output 6. The coupling between the lateral ports 3 and 4 happens only in this power divider 9, after a combination with the equivalent ports of another Boifot junction. Moreover, the through outputs 2 of both Boifot junctions are coupled with a fourth power divider 7 between the two power dividers 8. This power divider couples the vertical polarized signals at the two through outputs of the two Boifot junctions.

(25) The component of FIG. 8 is preferably monolithic (monobloc), i.e., made of one single part. In one preferred embodiment, this part is made by 3d printing a core, for example using a stereo lithography process or selective laser sintering process or selective laser melting process. The core is preferably non-conductive and could be made of a plastic, such as polyamide or a conductive metal such as aluminium. This core can then be plated with a conductive layer, such as Copper or Silver. This 3D printing process of one monolithic part reduces the perturbations caused by junctions between parts, and reduces the bulk and weight of the component.

(26) FIG. 9 shows the orthomode transducer with beamforming capabilities of FIG. 8, but in which the fifth port 70 at the output of the fourth power divider 7 that connects the two through ports 2 is bended, in the upward direction. This bend facilitates the access to the fifth port polarization perpendicular to the Boifot junctions. That path could be also bended in the downward direction without affecting the performance. The access to the fifth port 70 could also be achieved by bending or twisting the power dividers 8, or by splitting this port 70 in two branches (not shown).

(27) FIG. 10 shows another embodiment of a complete orthomode transducer with beamforming capabilities, similar to the transducer of FIG. 9, but in which each of the power dividers 8 comprises twisted legs 81 between the lateral ports 3,4 and the dividing portion 82. The twist angle is preferably between 30° and 120°, preferably between 30° and 60°, for example 45°.

(28) In the arrangement of FIG. 10, the input ports 1 of two adjacent Boifot junctions are staggered, thus allowing a further reduction in the distance between the two adjacent junctions in both directions. This arrangement can be used either with a separation between the two Boifot junctions, and between adjacent radiating elements, smaller, equal or larger than one nominal wavelength.

(29) A plurality of orthomode transducer with beamforming capabilities as shown on FIG. 8, 9 or 10 could be coupled into one single component. FIGS. 11 and 12 show two different views of an arrangement of two orthomode transducers (each with two Boifot junctions), the bended orthogonal ports 70 at the output of each fourth power divider being combined through an additional power divider 15. As in FIGS. 8 to 10, it is also possible to combine the outputs of the two power dividers 8 of each transducers with a third power divider 9 (not shown), and then to combine the outputs of those two third power dividers 9 with an additional power divider (not shown).

(30) Moreover, as shown on FIG. 11, radiating elements (antennas 11) could be coupled to the input ports 1 of each Boifot junction. In this embodiment, the antenna array comprises 8 antennas 11 coupled through four orthomode transducers with beamforming capabilities as previously described. The horizontally polarized outputs 7 of the stacked orthomode transducer with beamforming capabilities are mutually coupled through an additional waveguide twists, bends and power dividers 13. The vertically horizontally polarized outputs 7 of the stacked orthomode transducer with beamforming capabilities are mutually coupled through an additional waveguide twists, bends and power dividers 14.

(31) The antennas 11 are preferably rectangular horn antennas. In a preferred embodiment, they are stepped horn antennas. Waveguide steps of increasing cross-section are used to improve the reflection coefficient of the orthogonally polarized signals radiated by the antenna. Other antenna profiles such as linear, smooth or spline profiles can be used, being the stepped profile preferred for its shorter axial dimension.

(32) In the case of an array designed for transmission in the Ku-band, the dimensions of the horn antennas are preferably 20 mm×40 mm (around 1λ×2λ at 14.5 GHz).

(33) This antenna could be arranged in an array free of grating lobes for the most relevant angles (<80°).

(34) The separation between two antennas horns in one first direction is preferably smaller than the nominal wavelength and the separation between two antennas horns in one second direction orthogonal to the first direction is smaller than two nominal wavelengths.

(35) The nominal wavelength is the wavelength for or minimal wavelength for which the array is designed and which can be transmitted with minimal attenuation.

(36) Interestingly, this arrangement of FIG. 10 still has a horizontal and a vertical symmetry plane.

(37) Arrays of antennas with different number of antennas and of orthomode power dividers could be used.

(38) The array of antenna could be built as an integral component. Alternatively, it could be assembled from different parts; for example, the antennas 11 could be mounted to the port 1 of the orthomode power dividers.

(39) The antenna array of the invention consists of only antennas, pairs of Boifot junctions forming a new component called orthomode transducer with beamforming capabilities, power dividers and twisted waveguides.

(40) The bandwidth of the component is determined by the waveguide width, which determines the propagation of the fundamental mode and the higher-order modes. In one embodiment, this width is between 15 and 19.05 mm, for example 16.5 mm and the cutoff frequency of the fundamental (TE10) and the first higher-order (TE20) mode is 9.08 GHz and 18.15 GHz, respectively.

(41) Although the proposed orthomode transducer with beamforming capabilities has been described in a Ku-band Satcom array, it could also be used in other applications.