Millimeter wave waveguide and transmission system comprising such a waveguide

Abstract

The present description relates to a millimeter waveguide (50) comprising a first part (51) connected to a second part (52), the first part (51) comprising first waveguides (541, 542, 543) each being configured to receive a first millimeter wave, and the second part corresponding to a second waveguide, each first waveguide (541, 542, 543) comprising a first free end (551, 552, 553) and a second end joined to the second waveguide (52), each first and second waveguide being made of a dielectric material.

Description

Technical field

[0001] The present application relates to a millimeter waveguide made of a dielectric material and a millimeter wave transmission system comprising such a waveguide. Prior art

[0002] It is known to transmit millimeter waves through a dielectric plastic waveguide. For some applications, it is desirable to be able to transmit millimeter waves corresponding to the aggregation of several millimeter waves in different frequency bands, each corresponding to a signal to be transmitted.

[0003] There Figure 1is a diagram showing an example of a millimeter wave transmission system 5. The millimeter wave transmission system 5 comprises a millimeter wave transmitting device 10, a millimeter wave receiving device 30, and a waveguide 20 made of dielectric plastic material transmitting the millimeter electromagnetic waves between the transmitting device 10 and the receiving device 30.

[0004] The millimeter wave transmission device 10 comprises N transmission blocks 11 1 to 11 N , N being an integer between 2 and 8 typically, but possibly being a higher integer, N being equal to 3 for example in Figure 1. Each transmission block 11 i , i varying from 1 to N, comprises a modulation circuit 12 i receiving at least one digital signal SBT i and providing an analog signal ST i in a frequency band which may depend on the block 11 i . The transmission device 10 further comprises a combination circuit 14 receiving the analog signals ST 1 to ST N provided by the transmission blocks 11 1 to 11 N and providing a global analog signal STG in a transmission frequency band ΔB corresponding substantially to the sum of the signals ST 1 to ST N to control an antenna 15 for transmitting millimeter electromagnetic waves. The combination circuit 14 may be produced by conductive tracks of a printed circuit. The millimeter electromagnetic waves provided by the antenna 15 are guided by the waveguide 20 to the reception device 30.

[0005] The millimeter wave receiving device 30 comprises a millimeter wave receiving antenna 31 capturing the millimeter electromagnetic waves supplied by the waveguide 20 and supplying a reception signal SRG in the transmission band ΔB. The receiving device 30 further comprises a distribution circuit 32 receiving the analog reception signal SRG and supplying M analog reception signals SR 1 to SR M to M reception blocks 33 1 to 33 M , M being an integer between 1 and 8 typically, but possibly being a higher integer, M being equal to 3 for example in Figure 1 . Each reception block 33 j , j varying from 1 to M, comprises a demodulation circuit 34 j receiving the reception signal SR j and providing an SBR signal j in the final frequency band.

[0006] A disadvantage of the millimeter wave transmission system 5 of the Figure 1is that the generation of the overall analog STG signal can have significant losses. A disadvantage of the millimeter wave transmission system 5 of the Figure 1 is that good coupling between the waveguide 20 and each antenna 31 and 35 can be difficult to implement over the entire transmission frequency band ΔB which can be greater than several tens of GHz. Summary of the invention

[0007] An embodiment overcomes all or part of the disadvantages of millimeter waveguides made of a dielectric material and of millimeter wave transmission systems comprising such a known waveguide.

[0008] One embodiment provides a millimeter waveguide comprising a first portion connected to a second portion, the first portion comprising first waveguides, each configured to receive a first millimeter wave, and the second portion corresponding to a second waveguide, each first waveguide comprising a first free end and a second end joined to the second waveguide, each first and second waveguide being entirely made of a dielectric material.

[0009] According to one embodiment, the millimeter waveguide further comprises a third portion comprising third waveguides, each third waveguide comprising a first free end and a second end joined to the second waveguide.

[0010] According to one embodiment, the first and second waveguides each comprise a tube delimiting an internal volume filled with a gas, a mixture of gases, a fluid or a solid whose dielectric constant is lower than that of the dielectric material.

[0011] According to one embodiment, the dimensions of the straight sections of the first waveguides are different.

[0012] According to one embodiment, the cross section of the tube of at least one of the first waveguides is rectangular and the cross section of the tube of the second waveguide is circular.

[0013] According to one embodiment, the first and second waveguides are each made of a plastic material, in particular polytetrafluoroethylene, polypropylene or polystyrene.

[0014] An embodiment also provides a system for transmitting first millimeter waves comprising a millimeter waveguide as defined above, a millimeter wave transmitting device and a millimeter wave receiving device, the millimeter wave transmitting device comprising, for each first waveguide, an antenna configured for transmitting millimeter waves and coupled with said first waveguide.

[0015] According to one embodiment, each first millimeter wave has a frequency band between 30 GHz and 300 GHz.

[0016] According to one embodiment, the frequency bands of the first millimeter waves are distinct. Brief description of the drawings

[0017] These and other features and advantages will be set forth in detail in the following description of particular embodiments given without limitation in relation to the attached figures, among which: there Figure 1 , described above, is a diagram showing an example of a millimeter wave transmission system; Figure 2 is a diagram showing one embodiment of a millimeter wave transmission system; Figure 3 is a diagram showing another embodiment of a millimeter wave transmission system; Figure 4 is a partial, schematic, cross-sectional view of an embodiment of a branch of a waveguide of the millimeter wave transmission system of the Figure 2 ; there Figure 5 is a partial, schematic perspective view of an embodiment of the waveguide of the millimeter wave transmission system of the Figure 2 ; there Figure 6 is a partial, schematic perspective view of another embodiment of the waveguide of the millimeter wave transmission system of the Figure 2 ; there Figure 7 and the figure 8 are respectively a top view and a side view, partial and schematic, of an embodiment of assembly between the waveguide and a transmission device of the millimeter wave transmission system of the Figure 2 ; there figure 9 and the Figure 10 are respectively a top view and a side view, partial and schematic, of another embodiment of assembly between the waveguide and the transmission device of the millimeter wave transmission system of the Figure 2 ; there Figure 11 is a block diagram of an embodiment of a transmitting block of the millimeter wave transmission system of the Figure 2 ; there Figure 12is a block diagram of another embodiment of the transmission block of the millimeter wave transmission system of the Figure 2 ; and the Figure 13 is a partial, schematic perspective view of the internal volume of an embodiment of the waveguide of the millimeter wave transmission system of the Figure 2 integrating a filtering function. Description of the embodiments

[0018] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0019] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed. In particular, the millimeter wave transmission and reception circuits are well known to those skilled in the art and are not described in detail.

[0020] Unless otherwise specified, when two elements are connected together, this means directly connected without intermediate elements other than conductors, and when two elements are connected (in English "coupled") together, this means that these two elements can be connected or be connected by means of one or more other elements.

[0021] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made unless otherwise specified to the orientation of the figures.

[0022] Unless otherwise specified, the expressions "about", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%. In the remainder of the description, a millimeter wave is an electromagnetic wave whose wavelength can vary between 1 mm and 10 mm, which corresponds to a frequency that can vary between 30 GHz and 300 GHz.

[0023] There Figure 2is a diagram showing one embodiment of a millimeter wave transmission system 40. The millimeter wave transmission system 40 comprises all of the elements of the millimeter wave transmission system 5 shown in Figure 1 with the difference that the combination circuit 14, the antenna 15, the antenna 31, and the distribution circuit 32 are not present, that the transmission device 10 comprises an antenna 42 i for each transmission block 11 i , i varying from 1 to N, that the reception device 30 comprises an antenna 44 j for each reception block 33 j , j varying from 1 to M, and that the waveguide 20 is replaced by a waveguide 50. Each transmission block 11 i , i varying from 1 to N, and the corresponding antenna 42 i then forms a transmission circuit 45 i of millimeter waves in a transmission frequency band ΔB i .

[0024] According to one embodiment, the waveguide 50 comprises a first part also called the collection part 51, a second part 52, and a third part also called the distribution part 53. The central waveguide 52 connects the collection part 51 to the distribution part 53.

[0025] The collection part 51 comprises N branches 54 1 to 54 N (three branches 54 1 , 54 2 , and 54 3 being represented as an example in Figure 2 ). Each branch 54 2 , i varying from 1 to N, corresponds to a first waveguide. The second part 52 corresponds to a second waveguide and called central waveguide thereafter. Each branch 54 i , i varying from 1 to N, comprises a free end 55 i and is connected, on the side opposite the free end 55 i , to the central waveguide 52. The distribution part 53 comprises M branches 56 1 to 56 M (three branches 56 1 , 56 2 , and 56 3 being represented in Figure 2). Depending on the application envisaged, the number M may be equal to N or different from N. Each branch 56 j , j varying from 1 to M, corresponds to a third waveguide which comprises a free end 57 j and which is connected, on the side opposite the free end 57 j , to the central waveguide 52.

[0026] According to one embodiment, the waveguide 50 is entirely made of a dielectric material. In particular, the waveguide 50 does not comprise any electrically conductive elements, in particular metallic elements. This advantageously makes it possible to produce a flexible waveguide 50, in particular one exhibiting elastic deformations.

[0027] Each antenna 42 i , i varying from 1 to N, is arranged in proximity, preferably in contact with the axial end 55 2 of the branch 54 i . Each antenna 42 i is for example adapted to emit millimeter waves which propagate in the corresponding branch 54 i. Each antenna 42 i is adapted to emit a millimeter wave in the transmission frequency band ΔB i . By coupling between the antenna 42 i and the corresponding branch 54 i, the millimeter wave in the transmission frequency band ΔB i propagates in the branch 54 i to the central waveguide 52. The millimeter waves add up at the junction between each branch 54 i and the central waveguide 52 to form a millimeter wave in the transmission frequency band ΔB. Each antenna 44 j , j varying from 1 to M, is arranged nearby, preferably in contact with the axial end 57 j of the branch 56 j .Each 44 j antenna is for example adapted to capture millimeter waves which propagate in the corresponding 56 j branch.

[0028] For the 40 system of the Figure 2 , the aggregation of millimeter waves in the transmission frequency bands ΔB i is carried out by the waveguide 50 while for the system 5 of the Figure 2 , this aggregation is carried out on the signals ST i by the combination circuit 14 of the transmission device 10. The aggregation of the millimeter waves in the transmission frequency bands ΔB i can, advantageously, be carried out with fewer losses, in particular insertion losses, by the waveguide 50 than when it is carried out by the combination circuit 14. Similarly, for the system 40 of the Figure 2 , the distribution of millimeter waves in the transmission frequency bands ΔB i is carried out by the waveguide 50 while for the system 5 of the Figure 2, this distribution is carried out on the signals ST i by the distribution circuit 32 of the reception device 30. The distribution of the millimeter waves in the transmission frequency bands ΔB i can, advantageously, be carried out with fewer losses, in particular insertion losses, by the waveguide 50 than when it is carried out by the distribution circuit 32.

[0029] According to one application, the signals ST i , i varying from 1 to N, correspond to different signals. The transmission frequency bands ΔB i can then be distinct and the transmission frequency band ΔB can correspond to the sum of the transmission frequency bands ΔB i . The width of the transmission frequency band ΔB is then greater than the width of each transmission frequency band ΔB i . According to one embodiment, the width of each transmission frequency band ΔB i can be less than 10 GHz. For example, the transmitting device 10 can provide signals ST 1 , ST 2 , ST 3 , and ST 4 , the signal ST 1 being in the frequency band ΔB 1 from 122 GHz to 131 GHz, the signal ST 2 being in the frequency band ΔB 2 from 131 GHz to 140 GHz, the signal ST 3 being in the frequency band ΔB 3 from 140 GHz to 149 GHz, and the signal ST 4 being in the frequency band ΔB 4 from 149 GHz to 157 GHz.The width of each frequency band ΔB 1 , ΔB 2 , ΔB 3 , and ΔB 4 is equal to 9 GHz. The millimeter waves transported in the central waveguide 52 are then in the frequency band ΔB from 122 GHz to 157 GHz. The width of the frequency band ΔB is equal to 35 GHz. The efficiency of the coupling between a millimeter waveguide and an antenna depends in particular on the width of the frequency band of the millimeter waves to be transmitted to the waveguide. Therefore, the coupling between each antenna 42 i and the branch 54 i for the system 40 of the . Figure 2 , which is to be carried out on the frequency band ΔB i , can, advantageously, be more efficient than the coupling between the antenna 15 and the waveguide 20 for the system 5 of the Figure 2 which is to be carried out on the wider ΔB frequency band.

[0030] According to one application, the signals ST i are identical. The transmission frequency bands ΔB i can then be substantially identical and the transmission frequency band ΔB can be substantially equal to the transmission frequency band ΔB i . Such an application makes it possible to generate a high-power millimeter wave transported by the central waveguide 52 from reduced-power millimeter waves emitted by each antenna 42 i , i varying from 1 to N.

[0031] According to one embodiment, the propagation mode of the electromagnetic waves in the waveguide 50 is different from the transverse electromagnetic mode, also called TEM mode.

[0032] There Figure 3is a diagram showing one embodiment of a millimeter wave transmission system 60. The millimeter wave transmission system 60 comprises all of the elements of the millimeter wave transmission system 40 shown in Figure 2 with the difference that the reception device 30 comprises a single reception block 33 1 , and that the waveguide 50 does not comprise the distribution part 53, the central guide 52 comprising an end 58 located opposite the antenna 44 1 of the reception block 33 1 . This embodiment can in particular be implemented in the case where the transmission frequency bands ΔB i are substantially identical and the transmission frequency band ΔB.

[0033] There Figure 4 is a cross-sectional view of an embodiment of the branch 54 1 of the waveguide 50 of the millimeter wave transmission system 40 of the Figure 2. The branch 54 1 comprises a tube 62 made of a dielectric plastic material delimiting an internal volume 64. The internal volume 64 can be filled with a gas or a gaseous mixture, for example air, or with a liquid or solid dielectric material whose dielectric constant can be lower than that of the dielectric material making up the tube 62. Preferably, the internal volume 64 is filled with air. According to one embodiment, the tube 62 is surrounded by a sheath, not shown in Figure 4 , made of a dielectric material whose dielectric constant is lower than that of the dielectric material making up the tube 62. According to another embodiment, the branch 54 1 comprises a solid rod of the dielectric plastic material.

[0034] According to one embodiment, the tube 62 or the solid rod has a substantially rectangular or circular cross-section, other cross-sectional shapes nevertheless being conceivable (for example, an elliptical cross-section). Preferably, the tube 62 or the solid rod has a substantially rectangular cross-section which promotes the propagation of millimeter waves in the TE10 mode. In the embodiment illustrated in Figure 4 , the tube 62 or the rod has a substantially rectangular cross-section having a width L and a height H. According to one embodiment, the width L is between 0.5 mm and 10 mm. According to one embodiment, the height H is between 0.25 mm and 5 mm. According to one embodiment, the thickness E of the wall of the tube 62 is between 0.5 mm and 10 mm.

[0035] The dielectric constant of the dielectric material forming the tube 62 or the rod of the branch 54 1 is for example between 1 and 4, preferably between 2 and 4. The loss angle or delta tangent of the dielectric material forming the tube 62 or the rod of the branch 54 1 is for example less than 10 -3 < to ensure minimal signal losses in the branch 54 1 . This material may be a dielectric plastic material such as for example polytetrafluoroethylene, polypropylene or polystyrene. For example, for a material with a dielectric constant equal to 2 and for a frequency between 30 GHz and 300 GHz, the wavelength of the electromagnetic waves propagating in the branch 54 1 is between 7 mm and 0.7 mm. For example, waves at a frequency of around 60 GHz can be used, for which, for a material with a dielectric constant of 2, the wavelength is 3.5 mm.

[0036] Each branch 54 2 to 54 N may have the same characteristics as those previously described for branch 54 1 . Each branch 56 1 to 56 M may have the same characteristics as those previously described for branch 54 1 . The central waveguide 52 may have the same characteristics as those previously described for branch 54 1 .

[0037] According to one embodiment, the dimensions of the straight sections of the branches 54 1 to 54 N are different. In particular, the dimensions of the straight section of the branch 54 i are adapted to the frequency band ΔB i of the millimeter waves transported by the branch 54 i . According to another embodiment, the dimensions of the straight sections of the branches 54 1 to 54 N are identical. According to one embodiment, the dimensions of the straight sections of the branches 56 i to 56 M are different. In particular, the dimensions of the straight sections of the branch 56 j are adapted to the frequency band of the millimeter waves to be processed by the reception block 33 j associated with the branch 56 j . According to another embodiment, the dimensions of the straight sections of the branches 56 i to 56 M are identical.

[0038] According to one embodiment, the shape (for example circular shape, rectangular shape, etc.) of the cross section of the central waveguide 52 is different from the shape of the cross section of the branches 54 1 to 54 N .

[0039] There Figure 5 is a partial and schematic perspective view of an embodiment of the waveguide 50 whose collection part 51 comprises two branches 54 1 and 54 2 , the number of branches 54 i however being able to be greater than 2, each having a rectangular cross-section and whose central waveguide 52 has a circular cross-section.

[0040] This can be advantageous insofar as the waveguide 52 can have a length greater than the length of each branch 54 1 and 54 2 and the manufacture on an industrial scale of a waveguide having a circular cross-section is simpler than the manufacture of a waveguide having a rectangular cross-section. Each branch 54 1 , 54 2 having a rectangular cross-section which receives a millimeter wave provided by the associated antenna 42 1 , 42 2 makes it possible to reduce losses during the capture by the branch 54 1 , 54 2 of the millimeter wave emitted by the associated antenna 42 1 , 42 2.

[0041] This can further allow the transmission on the central waveguide 52 of circular section of a first millimeter wave coming from the branch 54 1 and of a second millimeter wave coming from the branch 54 2 , the first and second millimeter waves being polarized orthogonally, the frequency bands ΔB 1 and ΔB 2 possibly being identical. This advantageously makes it possible to double the data transmission rate on the frequency band ΔB 1 .

[0042] The 50 waveguide can be a single piece or obtained by assembling several pieces.

[0043] There Figure 6is a partial and schematic perspective view of an embodiment of the waveguide 50 whose collection part 51 comprises two branches 54 1 and 54 2 , the number of branches 54 i however being able to be greater than 2, and which corresponds to a separate part of the central waveguide 52. The manufacturing methods of the central waveguide 52 and of the collection part 51 can then be different. For example, the central waveguide 52 can be manufactured by extrusion and the collection part 51 can be manufactured by molding.

[0044] There Figure 7 and the figure 8 are respectively a top view and a side view, partial and schematic, illustrating the connection between the waveguide 50 and the transmission device 10 according to one embodiment. The figure 9 and the Figure 10 are figures analogous respectively to the Figure 7 and to the figure 8illustrating the connection between the waveguide 50 and the transmitting device 10 according to another embodiment.

[0045] On the figures 7 to 10 , the collection part 51 of the waveguide 50 comprises two branches 54 1 and 54 2 , the number of branches 54 i however being able to be greater than 2. On the figures 7 to 10 , the transmission device 10 comprises, for example, a printed circuit 70 and at least one microprocessor 72 mounted on the printed circuit 70. The antennas 42 1 and 42 2 are formed by conductive tracks 74 of the printed circuit 70, the antennas 42 1 and 42 2 being represented by dotted lines in figure 9 .

[0046] On the Figures 7 and 8, the waveguide 50 is mounted according to a so-called edge coupling. The antennas 42 1 and 42 2 are formed along an edge 76 of the printed circuit 70 and the branches 54 1 and 54 2 of the waveguide 50 are arranged along the edge 76 so that the axis of each branch 54 1 , 54 2 at the end 55 1 , 55 2 is substantially parallel to the plane of the printed circuit 70. Each antenna 42 1 , 42 2 may be in contact with the end 55 1 , 55 2 of the corresponding branch 54 1 , 54 2.

[0047] On the figures 9 and 10 , the waveguide 50 is mounted according to a so-called vertical coupling. The branches 54 1 and 54 2 of the waveguide 50 are arranged so that the axis of each branch 54 1 , 54 2 at the end 55 1 , 55 2 is substantially perpendicular to the plane of the printed circuit 70. Each antenna 42 1 , 42 2 can be covered by the corresponding branch 54 1 , 54 2.

[0048] There Figure 11is a block diagram of an embodiment of a transmission block 11 i , i varying from 1 to N, in which the transmission block 11 i receives a single digital signal SBT i , and performs modulation to provide the SMT signal in the transmission frequency band ΔB i .

[0049] Block 11 i of emission includes: a digital / analog converter 80 (DAC) receiving the signal SBT i and providing an analog signal in a basic frequency band; an adjustable gain amplifier 81 (VGA) receiving the analog signal provided by the digital / analog converter 80 and providing an amplified analog signal; a filter 82 receiving the amplified analog signal provided by the adjustable gain amplifier 81 and providing a filtered signal; a mixer 83 receiving the filtered signal provided by the filter 82 and further receiving an oscillating signal LO i and providing a signal in the transmission frequency band ΔB i corresponding to the filtered signal provided by the filter 82 mixed with the oscillating signal LO i; an amplifier 84 (IFA) receiving the signal provided by the mixer 83 and providing the signal ST i which corresponds to the signal provided by the mixer 83 which is amplified.

[0050] There Figure 12is a block diagram of another embodiment of a transmission block 11 i , i varying from 1 to N. In this embodiment, the transmission block 11 i receives several digital signals SBT i and performs a first modulation to provide an analog signal STI i in an intermediate frequency band. The transmission block 11 i then provides an analog signal STGI i equal to the sum of the analog signals STI i and then performs a second modulation from the signal STG i to provide the signal ST i in the transmission frequency band ΔB i .

[0051] According to one embodiment, the transmission block 11 i comprises: for each digital signal SBT i received, a sub-block 85 i which includes all of the elements described previously in relation to the Figure 11and which provides the analog signal STI i in an intermediate frequency band; a combination circuit 86 receiving the signals STI i provided by the sub-blocks 85 i and providing the global signal STG i corresponding substantially to the sum of the signals ST i; a mixer 87 receiving the global signal STG i and further receiving an oscillating signal LO2 i and providing a signal in the transmission frequency band ΔB i , corresponding to the global signal STG i mixed by the oscillating signal LO2 i; and an amplifier 88 (PA) receiving the signal provided by the mixer 87 and providing the signal ST i which corresponds to the signal provided by the mixer 87 which is amplified.

[0052] For certain applications, it may be desirable to filter the signal ST i , i varying from 1 to N, and / or to filter the signal SR j , j varying from 1 to M. According to one embodiment, this is achieved by adding, for each transmission block 11 i , a filter receiving the signal ST i and providing a filtered signal to the antenna 42 i and / or by adding, for each reception block 33 j , a filter receiving the signal SR j from the antenna 44 j and providing a filtered signal to the reception block 33 j .

[0053] According to another embodiment, this filtering function is performed directly by the waveguide 50. According to one embodiment, the filtering function can be implemented on each branch 54 i , on the central waveguide 52, and / or on each branch 56 j . According to one embodiment, the filtering function is implemented by providing the branch 54 i , the central waveguide 52, and / or the branch 56 j with a cross section that varies along the branch 54 i , the central waveguide 52, and / or the branch 56 j .

[0054] There Figure 13is a perspective, partial and schematic view of the internal volume 64 of the branch 54 1 illustrating the performance of a filtering function by the branch 54 1 . By way of example, the cross-section of the branch 54 1 comprises abrupt variations, for example one or more constriction zones 90 in which the cross-section of the branch 54 1 is reduced, one or more expansion zones 92 in which the cross-section of the branch 54 1 is increased, and / or one or more obstacles 94 on the path of the millimeter waves.

[0055] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art. The system 40 of the Figure 2can be used in full duplex mode, the transmitting device 10 then further comprising a millimeter wave receiving device, for example analogous to the receiving device 30, and the receiving device 30 further comprising a millimeter wave transmitting device, for example analogous to the receiving device 10, so that millimeter waves can be transported by the waveguide 50 in both directions.

[0056] Finally, the practical implementation of the embodiments and variants described is within the reach of the person skilled in the art from the functional indications given above.

Claims

1. Millimeter waveguide (50) comprising a first part (51) connected to a second part (52), the first part (51) comprising first waveguides (54 1 , 54 2 , 54 3 ), each being configured to receive a first millimeter wave, and the second part corresponding to a second waveguide, each first waveguide (54 1 , 54 2 , 54 3 ) comprising a first free end (55 1 , 55 2 , 55 3 ) and a second end joined to the second waveguide (52), each first and second waveguide being entirely made of a dielectric material.

2. A millimeter waveguide according to claim 1, further comprising a third portion (53) comprising third waveguides (56 1 , 56 2 , 56 3 ), every third waveguide (56 1 , 56 2 , 56 3) comprising a first free end (57 1 , 57 2 , 57 3 ) and a second end joined with the second waveguide (52).

3. Millimeter waveguide according to claim 1 or 2, wherein the first and second waveguides each comprise a tube (62) delimiting an internal volume (64) filled with a gas, a mixture of gases, a fluid or a solid whose dielectric constant is lower than that of the dielectric material.

4. Millimeter waveguide according to claim 3, wherein the dimensions of the cross sections of the first waveguides (54 1 , 54 2 , 54 3 ) are different.

5. Millimeter waveguide according to claim 3 or 4, wherein the cross section of the tube (62) of at least one of the first waveguides (54 1 , 54 2 , 54 3) is rectangular and in which the cross-section of the tube (62) of the second waveguide (52) is circular.

6. Millimeter waveguide according to any one of claims 1 to 5, in which the first and second waveguides are each made of a plastic material, in particular polytetrafluoroethylene, polypropylene or polystyrene.

7. System (40; 60) for transmitting first millimeter waves comprising a millimeter waveguide (50) according to any one of claims 1 to 6, a millimeter wave transmission device (10) and a millimeter wave reception device (30), the millimeter wave transmission device (10) comprising, for each first waveguide (54 1 , 54 2 , 54 3 ), an antenna (42 1 , 42 2 , 42 3 ) configured for millimeter wave emission and coupled with said first waveguide.

8. The system of claim 7, wherein each first millimeter wave has a frequency band between 30 GHz and 300 GHz.

9. System according to claim 8, wherein the frequency bands of the first millimeter waves are distinct.

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