DEVICE FOR TRANSMITTING A SIGNAL TO A WAVE CONDUCTOR

Description

[0001] The present invention relates to a device for transmitting a signal to a waveguide. The present invention also relates to an associated transmission assembly. Furthermore, the present invention relates to an associated antenna system.

[0002] Various printed circuit board-to-waveguide transition models are known that allow a waveguide to be powered by a printed circuit board.

[0003] Some of these designs use a short circuit positioned appropriately relative to a plunger using a quarter-wave cavity. Other designs use additional connectors or mechanical parts to perform the transition.

[0004] However, the use of cavities, connectors or mechanical parts makes the transition cumbersome and complicates its implementation.

[0005] It is also known for transitions implementing rectangular patches to feed a waveguide.

[0006] However, such patches are not suitable for the section of all waveguides.

[0007] It is also known as a transition device for feeding a rectangular waveguide from the small side of the guide using a cavity called SIW (from the English "Substrate Integrated Waveguide" translated into French as "waveguide made in a printed circuit").

[0008] However, such a device does not allow a waveguide to be fed from its long side. Furthermore, such a device necessitates the addition of an extra transition between the SIW cavity and a microstrip line or coplanar lines, for example.

[0009] Documents EP 1 396 902 A, JP 2010 268228 A and US 2016 / 204495 A describe examples of signal transmission devices.

[0010] There is therefore a need for a device that enables the transition of a signal between a printed circuit board and a waveguide, which is compact, simple to manufacture and adaptable to all types of waveguides.

[0011] For this purpose, the invention relates to a signal transmission device according to claim 1.

[0012] According to other advantageous aspects of the invention, the device comprises one or more of the features of claims 2 to 8, taken individually or in all technically possible combinations.

[0013] The invention also relates to a signal transmission assembly according to claim 9.

[0014] According to other advantageous aspects of the invention, the assembly comprises one or more of the features of claims 10 to 11 taken individually or in all technically possible combinations.

[0015] The invention also relates to an antenna system according to claim 12.

[0016] Other features and advantages of the invention will become apparent from the following description of embodiments of the invention, given by way of example only, and with reference to the drawings which are: [ Fig 1] Figure 1 , a schematic profile view of a transmission assembly according to a first embodiment, [ Fig 2] Figure 2 , a schematic representation seen from below of the entire figure 1 , [ Fig 3] Figure 3 , a schematic exploded view representation of the entire figure 1 , And [ Fig 4] Figure 4 , a schematic exploded view representation of a transmission assembly according to a second embodiment.

[0017] A first embodiment of a transmission assembly 10 is illustrated by the figures 1 to 3 .

[0018] The assembly 10 is configured to ensure the transition of a signal between a printed circuit board 12 and a waveguide 14. The signal to be transmitted is, for example, a radio frequency signal, the frequency of the signal being in this case between 100 Megahertz (MHz) and 1000 Gigahertz (GHz).

[0019] The assembly 10 includes the waveguide 14 and a transmission device 15.

[0020] The waveguide 14 has a cross-section. The cross-section of the waveguide 14 is, for example, square, rectangular, single-ridged, double-ridged, or circular. The single-ridged cross-section is obtained for a waveguide with one rib along its entire length. The double-ridged cross-section is obtained for a waveguide with two ribs along its entire length. The figures in this application illustrate a ridged waveguide with a rib 14A.

[0021] In the case of waveguides with a square cross-section, rectangular, single ridge, double ridge, or more generally comprising several ribs along their length, the cross-section of the waveguide comprises a section length, called the "long side" and a section width called the "short side".

[0022] The transmission device 15 includes the printed circuit board 12, a first access 16 for the signal to be transmitted, a second access 18 for the signal to be transmitted and a transition element 20.

[0023] The printed circuit board 12 (PCB for "Printed Circuit Board") includes a substrate 24 and, where applicable, elements printed on the substrate 24. The substrate 24 is made of a dielectric material.

[0024] In the following description, a longitudinal direction X is defined, represented in the figures by an X-axis and corresponding to the length of the substrate 24. A first transverse direction, called the stacking direction Z, is also defined, perpendicular to the longitudinal direction X and represented in the figures by an Z-axis, corresponding to the thickness of the substrate 24. A second transverse direction Y is also defined, perpendicular to both the longitudinal direction X and the first transverse direction Z. The second transverse direction Y is represented in the figures by an Y-axis and corresponds to the width of the substrate 24.

[0025] The substrate 24 comprises two faces 24A, 24B opposite each other along the stacking direction Z. The face of the substrate 24 furthest from the waveguide 14 along the stacking direction Z is called the upper face 24A. The face of the substrate 24 closest to the waveguide 14 along the stacking direction Z is called the lower face 24B.

[0026] In the case of a signal transmission from the printed circuit board 12 to the waveguide 14, the first access 16 forms the input for the signal to be transmitted and the second access 18 forms the output for the signal to be transmitted.

[0027] In the case of a signal transmission from the waveguide 14 to the printed circuit board 12, the first access 16 forms the output for the signal to be transmitted and the second access 18 forms the input for the signal to be transmitted.

[0028] The transition element 20 is configured to ensure the transition of the signal to be transmitted between the printed circuit board 12 and the waveguide 14, i.e. either from the printed circuit board 12 to the waveguide 14, or from the waveguide 14 to the printed circuit board 12 (reciprocal transition).

[0029] The transition element 20 includes a conductive ribbon 29, an upper ground plane 30, a lower ground plane 32 and means 34 for delimiting a cavity between the upper ground plane 30 and the lower ground plane 32.

[0030] Conductive tape 29 is a narrow conductive tape.

[0031] The conductive ribbon 29 forms the first access 16 of the transmission device 15.

[0032] In the example illustrated by the figures 1 to 3 , the conductive ribbon 29 is connected to the upper ground plane 30. In particular, the conductive ribbon 29 protrudes from the upper ground plane 30.

[0033] The upper ground plane 30 is made on the substrate 24 of the printed circuit board 12, that is to say that the upper ground plane 30 is an integral part of the printed circuit board 12.

[0034] In the embodiment illustrated by the figures 1 to 3 , the upper ground plane 30 is made on the upper face 24A of the substrate 24.

[0035] The upper ground plane 30 is, for example, a metal plate.

[0036] The lower ground plane 32 is intended to be in direct contact with the waveguide 14, in particular with an end section of the waveguide 14.

[0037] The lower ground plane 32 is located below the upper ground plane 30 in the stacking direction Z.

[0038] The lower ground plane 32 is, for example, a metal plate.

[0039] In the example illustrated by the figures 1 to 3The lower ground plane 32 is made on the substrate 24 of the printed circuit board 12. More precisely, in the example illustrated on the figures 1 to 3 , the lower ground plane 32 is made on the lower face 24B of the substrate 24.

[0040] In the example illustrated by the figures 1 to 3 The conductive ribbon 29 and the lower ground plane 32 are therefore separated by the substrate 24. Thus, the conductive ribbon 29, the lower ground plane 32, and the substrate 24 form a microstrip line. The term "microstrip line" refers to a microwave transmission line formed of two conductors: a narrow ribbon, separated from a ground plane by a dielectric substrate.

[0041] The lower ground plane 32 includes a slot 42 forming the second access 18 of the transmission device 15.

[0042] Slot 42 is, for example, rectangular in shape. In this case, slot 42 has, for example, a length along the second transverse direction Y approximately equal to λ 2 , λ being the wavelength of the signal to be emitted or received.

[0043] Alternatively, slot 42 has other shapes, for example, in the shape of a "bow tie" or a "bone".

[0044] Preferably, the slot 42 is positioned on the lower ground plane 32 along the longitudinal direction X and the second transverse direction Y so as to be entirely contained within the aperture of the waveguide 14 and not parallel to the small cross-section (short side) of the waveguide 14 for a rectangular waveguide (with or without a ridge). The performance of the transition will vary depending on the position of the slot 42.

[0045] Advantageously, the slot 42 is positioned on the lower ground plane 32 along the longitudinal direction X and the second transverse direction Y so as to be at the center of the cavity delimited by the delimiting means 34. Thus, the slot 42 is located at a maximum of the magnetic field. Advantageously, when the cross-section of the waveguide 14 is such that the waveguide 14 comprises a long side and a short side (ridged, square, or rectangular cross-section, in particular), the slot 42 is positioned on the lower ground plane 32 so as to be substantially parallel to the long side of the waveguide 14.

[0046] Alternatively, the slot 42 is inclined relative to the long side of the waveguide 14.

[0047] Advantageously, when the waveguide 14 is a waveguide having at least one rib along its length (ridge waveguide), the waveguide 14 is arranged with respect to the lower ground plane 32 so that the slot 42 is substantially equidistant, along the longitudinal direction X, from the rib, on the one hand, and from the top of the waveguide 14, on the other hand.

[0048] The delimitation means 34 are configured to delimit a cavity between the upper ground plane 30 and the lower ground plane 32.

[0049] In the embodiment illustrated by the figures 1 to 3 The cavity is a so-called SIW cavity (from the English "Substrate Integrated Waveguide" translated into French as "wave guide made in a printed circuit") because the lower ground plane 32 and the upper ground plane 30 are made on the substrate 24 of the printed circuit 12. The SIW cavity is an integral part of the transition element 20.

[0050] In the first embodiment, the delimitation means 34 are inserted into the substrate 24.

[0051] The delimitation means 34 are, for example, vias. A via is a metallized hole allowing an electrical connection to be established between two conductive layers.

[0052] Alternatively, delimitation means 34 are metallic trenches.

[0053] Advantageously, the cavity is of length λ along the longitudinal direction X, λ being the wavelength of the signal to be emitted or received. More generally, the cavity is of length k . λ 2 along the longitudinal direction X, with k an integer greater than or equal to two.

[0054] The person skilled in the art will understand that the length of the cavity is chosen so that the cavity is a resonant cavity, that is to say a hollow space in which the signal to be emitted or received enters into resonance.

[0055] The operation of assembly 10 according to the first embodiment will now be described.

[0056] Initially, for a transition from the printed circuit board 12 to the waveguide 14, the signal to be transmitted is captured by the transmission device 15 via the conductive ribbon 29 connected to the upper ground plane 30.

[0057] The signal is then coupled (or injected) into the cavity formed between the upper ground plane 30 and the lower ground plane 32, and delimited by the delimiting means 34.

[0058] The signal then exits the transmission device 15 via the slot 42 inscribed in the lower ground plane 32 and arrives in the waveguide 14.

[0059] Conversely, for a transition from the waveguide 14 to the printed circuit board 12, the signal to be transmitted is captured by the transmission device 15 via the slot 42 of the lower ground plane 32.

[0060] The signal is then coupled in the cavity formed between the upper ground plane 30 and the lower ground plane 32, and delimited by the delimiting means 34.

[0061] The signal then exits the transmission device 15 via the conductive ribbon 29 connected to the upper ground plane 30.

[0062] Thus, the transmission device 15 according to the first embodiment makes it possible to ensure the transition of a signal between a printed circuit 12 and a waveguide 14. In particular, the transition element 20 allows a direct transition between the waveguide 14 and the printed circuit 12 at 90°, that is to say that the transition is positioned in the plane of the cross section at the end of the waveguide 14.

[0063] In particular, in this embodiment, the transition element 20 is fully integrated into the substrate 24 of the printed circuit board 12, and no other parts (connectors, quarter-wave cavity) are used to perform the signal transition. The transmission device 15 is therefore compact and simple to manufacture. It can thus be easily mounted on the back of an antenna or, more generally, a waveguide.

[0064] The presence of the SIW cavity allows for the confinement of fields and thus prevents stray radiation outside the cavity. It also provides shielding against fields coming from outside.

[0065] Such a device 15 generates low losses, the possible losses coming in particular from the substrate 24 of the printed circuit 12 or from the printed metallic patterns (in particular, in the microstrip line and the ground planes 30 and 32).

[0066] Such a transmission device 15 is adaptable to all types of waveguides regardless of the geometry of their cross-section, whether the waveguide is radiating or not. In the specific case of the ridge waveguide, such a device 15 notably allows the waveguide to be fed from its long side.

[0067] The configuration in which the slot 42 is parallel to the long side of the waveguide and to the center of the cavity makes it possible to induce a potential difference between the edges of the slot 42, and thus maximize the energy transfer between the SIW cavity and the waveguide.

[0068] Such a transmission assembly 10 is, for example, intended to be integrated into an antenna system, such as an active scanning antenna, or into a radar system. For example, an antenna system may be formed of several transmission assemblies 10, the waveguides 14 of said assemblies 10 being arranged in parallel. In this case, the waveguides 14 are radiating.

[0069] According to a second embodiment as shown in the figure 4 , the elements identical to set 10 according to the first embodiment described opposite the figures 1 to 3 are not repeated. Only the differences are highlighted.

[0070] In the second embodiment, the conductive ribbon 29 forming the first access 16 of the transmission device 15 is connected to the lower ground plane 32. In particular, the conductive ribbon 29 protrudes from the lower ground plane 32.

[0071] Furthermore, in this second embodiment, the conductive ribbon 29 and the upper ground plane 30 are separated by the substrate 24. Thus, the conductive ribbon 29, the upper ground plane 30 and the substrate 24 form a microstrip line.

[0072] Apart from these differences, the operation of assembly 10 according to the second embodiment is identical to that of the first embodiment.

[0073] The transmission device 15 according to the second embodiment has the same advantages as that of the first embodiment.

[0074] Such a device 15 is an alternative arrangement for the components of the transition element 20. Indeed, in the first embodiment, the conductive ribbon 29 is integrated onto the printed circuit board 12 on the side opposite the waveguide 14, whereas in the second embodiment, the conductive ribbon 29 is integrated onto the printed circuit board 12 on the side of the waveguide 14. The choice between the two configurations depends on environmental and design constraints. For example, if the components of the printed circuit board 12 must be surface-mounted on the side of the waveguide 14, the second embodiment is more suitable.

[0075] A person skilled in the art will understand that the embodiments described above are likely to be combined with each other when such a combination is compatible.

Claims

1. A device (15) for transmitting a signal between a waveguide (14) and a printed circuit board (12), the device (15) comprising: a. a first access means (16) for the signal to be transmitted, b. a second access means (18) for the signal to be transmitted, c. a conductor track (29) forming the first access means (16), d. a printed circuit board (12) comprising a substrate (24), and e. a transition element (20) comprising: i. an upper ground plane (30) formed on the substrate (24) of the printed circuit board (12), ii. a lower ground plane (32) for direct contact with the waveguide (14), the lower ground plane (32) comprising a slot (42) forming the second access means (18) of the transmission device (15), iii. means (34) for delimiting a cavity between the upper ground plane (30) and the lower ground plane (32), either the upper ground plane (30) or the lower ground plane (32) being connected to the conductor track (29), characterized in that the cavity is of length k. λ 2 along the length of the substrate (24), with k an integer greater than or equal to two, λ being the wavelength of the signal to be transmitted, so that the cavity is a resonant cavity.

2. The device (15) according to claim 1, wherein the cavity is an SIW cavity.

3. The device (15) according to any one of claims 1 to 2, wherein the cavity is of length λ along the length of the substrate (24), λ being the wavelength of the signal to be transmitted.

4. The device (15) according to any one of claims 1 to 3, wherein the conductor track (29) protrudes from the upper ground plane (30).

5. The device (15) according to any one of claims 1 to 4, wherein the conductor track (29) protrudes from the lower ground plane (32).

6. The device (15) according to any one of claims 1 to 5, wherein the lower ground plane (32) is provided on the substrate (24) of the printed circuit board (12).

7. The device (15) according to any one of claims 1 to 6, wherein the delimiting means (34) are perforations.

8. The device (15) according to any one of claims 1 to 7, wherein the slot (42) in the lower ground plane (32) is arranged to be in the centre of the cavity delimited by the delimiting means (34).

9. A signal transmission assembly (10) comprising: a. a waveguide (14), and b. a device (15) for transmitting a signal between the waveguide (14) and a printed circuit board (12), the transmission device (15) comprising the printed circuit board (12) and being according to any one of claims 1 to 8.

10. The assembly (10) according to claim 9, wherein the waveguide (14) is a waveguide having at least one rib along its length, the waveguide (14) being arranged with respect to the lower ground plane (32) so that the slot (42) is substantially equidistant from the rib, on the one hand, and from the top of the waveguide (14), on the other.

11. The assembly (10) according to claim 9 or 10, wherein when the cross-section of the waveguide (14) is such that the waveguide (14) comprises a cross-sectional length, referred to as the long side, and a cross-sectional width, referred to as the short side, the slot (42) is positioned on the lower ground plane (32) so as to be substantially parallel to the long side of the waveguide (14).

12. An antenna system comprising at least one transmission assembly (10) according to any one of claims 9 to 11, advantageously several transmission assemblies (10) according to any one of claims 6 to 8, the waveguides (14) of said assemblies (10) being arranged in parallel.