WO2014057469A2

WO2014057469A2 - Rectangular waveguides for applications using terahertz signals

Info

Publication number: WO2014057469A2
Application number: PCT/IB2013/059309
Authority: WO
Inventors: Alessandro Macor; Emile De Rijk; Mathieu BILLOD
Original assignee: Ecole Polytechnique Federale De Lausanne (Epfl)
Priority date: 2012-10-11
Filing date: 2013-10-11
Publication date: 2014-04-17
Also published as: WO2014057469A3

Abstract

A waveguide for transmitting signals at terahertz (THz) frequencies, wherein said waveguide comprises at least a matrix and an insert piece having a waveguide channel, wherein said piece is inserted in said matrix.

Description

RECTANGULAR WAVEGUIDES FOR APPLICATIONS USING TERAHERTZ SIGNALS

REFERENCE TO RELATED APPLICATION The present application claims priority to Swiss patent application N°0T924/12 filed in the name of ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE (EPFL), the content of which is incorporated by reference in its entirety in the present application.

FIELD OF THE INVENTION AND PRIOR ART

Rectangular waveguides are commonly used to transmit electromagnetic signals at terahertz (THz) frequencies, corresponding to wavelengths in the millimetre range (MMW) and down to the sub-miiiimetre (sub-M MW) level. To achieve optimal signal transmission, the inner cross section of the waveguide normally scales with the wavelength λ of the signal as approximately λ/2 by λ/4.

The most commonly applied manufacturing techniques for rectangular waveguides are not suited for terahertz applications with waveguide cross sections in the sub-mm range, as the required precision of a few μιη on the dimensions and shape of the waveguide cannot easily be met.

The terahertz region from 0.1 to 3 THz in the electromagnetic spectrum is a frontier- area for research in physics, chemistry, biology, material science and medicine. This signal frequency region is known to provide a wealth of opportunities for high-precision probing and effective signal transmission in various application domains. For reference, a frequency of 0.1 THz corresponds to a wavelength of approximately 3 mm, while a frequency of 3 THz corresponds to a wavelength of approximately 0,1 mm.

THz radiation surpasses the frequency range of traditional electronics, but is situated below the range of optica.] and infrared generators. Regardless of the scope of its application, a functional THz system requires three main elements: a source generating the THz signal of interest, a signal transmission line and a final detection probe or receiver. Until recently there was a quasi-absence on the market of quality terahertz sources. A wide range of new products is now gradually filling this gap. The availability of sources has led to a recent blossoming of scientific research and applications with terahertz signals in many areas, as the awareness of the opportunities THz signals can offer increases.

At present, the widespread implementation of applications over the full THz frequency range is still hampered by a scarcity in efficient commercially available THz signal transmission components. Signal transmission for THz frequencies can only be achieved with specific wave-guide components: not with cables like for electronics, nor with optical fibres as for photonics and lasers.

Rectangular waveguides are commonly used to transmit electromagnetic signals with wavelengths in the millimetre range and down to the sub-millimetre level. In most cases they are used for short distances in the vicinity of the source, the detection probe or the receiver, and/or as a transition towards alternative waveguide geometries such as circular corrugated waveguides. To achieve optimal signal transmission, the inner dimensions of the rectangular waveguide normally scale with the wavelength of the signal of interest. As a general rule, rectangular waveguide cross sections usually measure approximately λ/2 by λ/4, where λ is the wavelength of the signal. Moreover, to allow easy connections, the rectangular waveguides need to be equipped with precision interface flanges, such as, but not. limited to, the UG 387 type. The objective to achieve efficient signal transmission imposes tight tolerances on the shape and dimensions of the waveguide profile. The required precisions on the four sides of the cross section amount to a few μιτι. Similar requirements apply to the corners, which have to be sharp. The most commonly used manufacturing techniques for rectangular waveguides, e.g. electroforming (EF) and electric discharge machining (EDM), have limited precision in scooping rectangular channels with sufficient precision and sharp corners They are therefore not optimally suited for producing rectangular apertures for THz signal transmission components.

DETAILED DESCRIPTION OF THE INVENTION

The invention described in the present application concerns a manufacturing technique for waveguide profiles, such as but not limited to, rectangular waveguide profiles or waveguide profile based devices such as filters, or packaging for active devices. The invention is compatible with the precision: requirements for terahertz applications.

The present invention is based on a new approach in which the precise rectangular shape or profile of the waveguide is formed from the boundary of one or several extruded or machined msert(s).

The insert is then introduced into a channel previously created inside an outer matrix eventually comprising the connection flanges or machined to form then the connection flanges.

The method of the present invention allows reaching high precision on the inner dimensions and shape of the waveguide in a cost-effective way, such precision not being necessary on the channel of the matrix or even the shape of the matrix and being compensated by the method used to combine the matrix and the insert.

The present invention will be better understood from the following description of several embodiments which are defined in the claims and from the appended drawings which show: Figures 1A to 1C illustrate perspective and front views of an embodiment of the invention; Figures 2A to 2C illustrate perspective and front views of another embodiment of the invention;

Figures 3A to 3C illustrate perspective and front views of another embodiment of the invention;

Figures 4A to 4C illustrate perspective and front views of another embodiment of the invention and Figures 5A to 5C illustrate perspective and front views of another embodiment of the invention.

Figures 6A to 6C illustrate perspective and front views of another embodiment of the invention.

Figures 7 A to 7C illustrate perspective and front views of another embodiment of the invention.

Figures 8A to 8C illustrate perspective and front views of another embodiment of the invention comprising the UG 387 type flanges,

Figures 9A to 9C illustrate perspective and front views of another embodiment of the invention comprising the UG 387 type flanges. Figures 10A to 10F illustrate perspective and front views of another embodiment of the invention comprising the UG 387 type flanges.

Figures 11A to 11C illustrate perspective and front views of another embodiment of the invention.

Figure 12 illustrates an example of the inner cross section sizes of a waveguide with respect to the wavelength λ. The present invention accordingly defines a product and a manufacturing technique for waveguide profiles that is compatible with the precision requirements for terahertz applications. Specifically, the present invention is based on a new approach using an assembly of at least, but not limited to, two components: an insert piece and an outer matrix.

In one of the preferred embodiment, the precise rectangular profile of the waveguide is located at the boundary of the insert piece, which can be formed with, the necessary precision with usual techniques of the art.

The insert piece is then inserted into a hollow channel inside the outer matrix.

Accordingly, in one embodiment the invention concerns a waveguide manufacturing method for waveguides used to transmit signals in the MMW, sub-MMW ranges at terahertz (THz} frequencies, wherein the method comprises at least the following steps; -) providing an insert piece with a waveguide profile;

-) providing a matrix with a channel;

-) introducing said insert piece in said channel to form the waveguide. in an embodiment the waveguide profile may be rectangular. In a variant, the profile is not rectangular. in an embodiment one side of the waveguide profile may be formed at least in part by the channel, for example by a side of the channel.

In an embodiment the insert piece comprises more than one part. In this case, the waveguide is preferably formed by the insert parts. Alternatively, the waveguide profile may be formed in part by a side of the channel even when the insert piece is made of more than one single part.

In an embodiment the introduction is made by interference fitting, whereby the insert is conditioned at a much lower temperature than the outer object structure (for example the matrix) prior to the insertion step and the parts are then allowed to stabilise at similar temperatures such the insert piece will remain blocked tightly inside the channel. In one embodiment, the insert piece is fixed in the matrix channel by external means. The external means may comprise at least a screw. In one embodiment, connection flanges are machined from the matrix. in another embodiment, the matrix is inserted in at least one connection flange.

In one embodiment, the invention concerns a waveguide for transmitting signals at terahertz (THz) frequencies, wherein said waveguide comprises at least a matrix and an insert piece having a waveguide profile, said piece being inserted in said matrix.

In an embodiment the matrix comprises a channel for the insertion of the insert piece. in an embodiment the insert piece is made of one single part, in a. variant, the insert piece is made of more than one part.

In an embodiment said waveguide profile is rectangular and one side of said waveguide profile is formed at least partly by the channel of the matrix and/or by another part of the insert. For example, a surface of the channel may form one side of the profile.

In one embodiment the matrix may comprise a channel for the insertion of the insert piece.

In one embodiment the insert piece may be made of one single part or more than one part in an embodiment additional channels are present in the matrix and/or the insert piece and/or formed by the insertion of the insert piece in the matrix. in an embodiment the matrix is made of and insert or insert parts may be made of a metal or a metal plated material. in an embodiment the matrix and/or the insert or insert parts may have a simple shape and/or a complex shape. in an embodiment the outer shape of the insert or insert parts may be identical with the inner shape of the channel of the matrix.

In an embodiment the outer shape of the insert or insert parts may be different from the inner shape of the channel of the matrix.

In one embodiment, the waveguide comprises connection flanges.

In one embodiment, the flanges may be machined from the matrix. In one embodiment the waveguide profile may have a complex shape for creating special effects, such as signal filters or resonant structures or packaging of active devices.

The basic procedure is illustrated in Figure 1, with possible different embodiments based on the same technique depicted in Figures 2A-2C, 3A-3C, 4A-4C, 5A-5C, 6A-6C, 7 A- 7C, 8A-8C, 9A-9C, 10A-10F, 11A-11C.

The feature that the rectangular waveguide profile is located at the boundary of a flat surface of the insert piece, facilitates the use of standard production techniques, e.g. extrusion or conventional machining. This provides ample opportunities to reach a high precision on the waveguide inner cross section including sharp corners, which are crucial for efficient THz wave-guiding. For the production of the hollow channel in the outer matrix, conventional methods, e.g. EF, EDM or extrusion or machining, can be applied. In particular, there are no tight precision requirements on the corners of the hollow channel as opposed to the waveguide profile.

For the insertion of the insert piece into the hollow channel, one can use, for example, an interference fitting technique, whereby the insert is conditioned at a much lower temperature than the outer object structure prior to the insertion procedure. This allows for an easy manipulation. Once the two assembled components have stabilised at similar temperatures, the insert will remain blocked tightly inside the channel. Of course, other equivalent techniques may be used to assemble the insert with the matrix and some examples will be described in the present application.

The assembly can then undergo further finishing, such as the machining of end- surfaces, flanges or other elements of the desired outer shape.

Alternatively, the insert piece can be inserted in the hollow channel and fixed in place with screws or any other equivalent means. Figures 1A to 1C illustrates the principle of the invention in a first embodiment.

Figure 1A illustrates an outer matrix 1 in a perspective view with a hollow channel. 2 formed according to the techniques disclosed herein,

In front of the matrix 1, in a position ready to be inserted in the channel 2, the insert 3 is illustrated with its waveguide profile 4 which has, for example the shape of a groove 4 along the longitudinal axis of the insert,

Figure IB illustrates the same elements as figure 1A, in perspective view, where the insert 3 has been inserted into the hollow channel 2 of the matrix 1.

Figure 1C illustrates the same configuration as figure IB, in a front view. More precisely, Figures 1A to 1C illustrate a waveguide manufacturing procedure according to the present invention, showing the insert piece 3 and the outer matrix 1

The insert piece 3 comprises a precisely scooped waveguide channel 4, and also has a precise upper surface 5 and rounded edges 6.

The outer matrix 1 has a hollow channel 2 with a precise fiat surface on the top 7, while the other surfaces and the corners have relaxed precision remands, Figures IB and 1C illustrate the assembled waveguide following an assembly method based on interference fitting or any other equivalent method for assembling both parts.

Figures 2A to 2C illustrate another embodiment of the invention with the same elements as the one illustrated in figures 1 A to 1C but with a different shape.

More precisely, the assembly comprises a rectangular shaped outer matrix 10 and a rounded insert piece 13 with the waveguide profile 14, The matrix 10 comprises a hollow channel 11 with a flat side 12, the shape of the channel allowing an insertion and fitting of the insert piece 13 as illustrated in figures 2B and 2C.

The outer shape of the piece 3 or 13 may be identical with the inner shape of the hollow channel (for example 2, 11} or they may be corresponding or they may also be different but allowing a stable insertion and positioning of the piece in said channel. As illustrated in these two embodiments, this shape is square or circular, but any other shape may be envisaged as illustrated in other embodiments of the present invention described herein. Also the outer shape of the matrix 1, 10 is not limited to a circular or square one as illustrated and other shapes are possible within the scope of the present invention as long as a stable positioning of the piece in the matrix is ensured, In order to ensure such stable positioning of the piece in the hollow channel, at least three contact zones or points should preferably be provided. This is specifically the case if the shapes are different Figures 3A to 3C illustrate further embodiments of the present invention and of the waveguide manufacturing technique using the principles exposed above, but showing examples of an assembly with complex shapes for both the outer matrix 20 with its hollow channel 22 and the insert piece 21 with it guide profile 23. As in the previous embodiment, one side of the waveguide 23 is formed by a surface 24 of the channel 22.

Figures 4A to 4G illustrate further embodiments of the device and of the waveguide manufacturing technique according to the invention, showing the example of an assembly of a matrix 30 and an insert piece 31 with its waveguide profile 33 with other complex shapes and additional channels 35-38 adapted to potential needs, such as reducing the friction between the insert 31 and the channel 32 of the outer matrix 30, or creating additional channels 35 to 38 for cooling or other purposes. These created channels 35-38 may have any shape and be formed in the insert 31 or created by a shape difference between the outer shape of the insert piece 31 and the inner shape of the channel 32, the matrix 30 of both of them, the aim being to form such channels 35-38 by the insertion of the insert 31 in the hollow channel of the matrix 30. This difference of shapes and the formation of additional channels is applicable to all embodiments of the present invention. Figures 5A to 5C illustrate another embodiment of the present invention and of the waveguide manufacturing technique, showing an example of an assembly with complex shapes as illustrated previously (see figures 3A to 3C, 4A to 4C) but with the use of an insert piece made in two parts. More specifically, this embodiment comprises a matrix 40 and an insert piece in two parts 41, 42 which are i ntroduced in the channel 43 of the matrix 40. in the embodiment illustrated, the waveguide profile 44 is formed by the assembly of the two parts 41-42 but, as in the previous embodiments, one side of the channel may be formed by one side of the channel 43,

Figures 6A to 6C illustrate schematically a further embodiment of the present invention. In this embodiment, means are illustrated to maintain the insert piece in the matrix in a stable way without using an interference fitting as mentioned previously. Specifically, this embodiment illustrates a matrix 50 with a channel 51 for the insertion of an insert piece made of two parts 48 and 49. The insert piece comprises in particular a waveguide profile 45 as discussed previously. The matrix 50 further comprises a gap or slit 47 that allows a deformation of the matrix under when the screw 46 is tightened up (see its position in figures 6B and 6C). Typically, the matrix will comprise a hole on one side of the gap and a thread on the other side to be able to tighten the screw 46. This way of doing may replace the interference fitting discussed above or may be combined with such technique to improve the mounting procedure. This allows to reduce the precision needed in the channel 51, for example by having a high precision on the bottom side on which part 49 will rest and a lower precision on the upper side of channel 51 which will be moved by the compression effect of the screw 46.

Figures 7 A to 7C illustrate a variant using screws 52, 53 [53 referencing a different type of screw that may be used) that apply their force directly on the insert piece 56/57. The matrix 54 in such embodiment is preferable made in one part and does not comprise a gap/slit 47 as in the previous embodiment. Here, as in previous embodiments, the matrix 54 comprises a channel 55 for the insertion of the piece 56-57, which comprises a waveguide profile 59. The insert piece 56-57 may be formed in one piece or more and the screws 52/53 will apply pressure when they are tighten up on the insert piece.

The fixing means 46-47, 52-53 illustrated here may be used in all embodiments described herein.

The embodiments of figures 6A-6C and 7A-7C are interesting in that they allow a less strict dimensioning and tolerances of the channel 51/55. indeed, in these embodiments, it is necessary to use tight tolerances only on one reference side of the channels (typically the lower side in the drawings, that is the side opposed to the side where the screws are mounted) against which the insert 48/49 or 56/57 will be pushed when the screws 46 and 53/53 will be tightened.

Figures 8A to 8C illustrate a further embodiment with an assembly using UG 387 type flanges 60. Here the insert piece is made from two parts 62 which may be symmetrical as illustrated or have other shape, for example as described herein in previous embodiments and inserted in the channel 63. in this embodiment, typically, the flanges 60 and the central part 64 may be formed from a matrix as described in previous embodiments. For example, the initial matrix may be as in figure 1 (matrix 1) and this matrix is then machined to form the result of figures 8A-8C. This can be done for example via electroforming or any suitable technique, During machining, the holes 61 of the flanges are also machined to form connectable flanges. Other matrixes disclosed herein with illustrated embodiments may of course be used in. accordance with this principle and be machined to obtain the result of figures 8A to 8C. Preferably, in this configuration, once the insert 62-62 has been positioned in the matrix/flanges 60, it provides the reference point to place the holes 61.

Alternatively, the flanges may be machined independently and then the matrix (for example matrix 1, 10, 20, 30 etc) is inserted in the flange 60, This implies that each flange comprises a hole suitable to receive the matrix to be inserted. The hole of the flange may have a shape identical to the outer shape of the matrix, or a corresponding shape or a different shape but allowing a stable positioning of the matrix in the flange,

Of course, any insert disclosed in the present application or equivalent ones may be used in this embodiment.

Figures 9A to 9C illustrate a further embodiment with an assembly using UG 387 type flanges 65. Here the insert piece is made from two parts 67-68 forming the waveguide profile when assembled and inserted in the channel 69 (see figure 9C for example). As discussed in reference to figures 8A to 8C, the flanges 65 may be machined from the matrix disclosed in previous figures (matrix 1, 10, 20, 30 etc), or the said matrix may be inserted in flanges 65 similarly to the description above of figures 8A to 8C.

Figures IDA to IOC illustrate a further embodiment with an assembly using UG 387 type flanges 70. . This embodiment is similar to the one of figures 8 A to SC. Here the insert piece is made from two parts 72-73 forming the waveguide profile when assembled and inserted in the channel 75 (see figure IOC for example). In this embodiment, one illustrates a particular shape of the waveguide profile 76 that could be achieved along the propagation path for example creating signal filters or resonant structures. This principle is of course applicable to all the embodiments of waveguides described herein and the particular shapes used may by present on each side (parts 72-73] of the waveguide or only on one side (part 72 or 73). The use of two parts 72-73 (at least) according to the principle of the present invention is therefore particularly advantageous to form such particular shapes in the waveguide.

Figures 10D to 10F illustrate a further embodiment of the invention. Basically, this embodiment corresponds to the one of figures 10A to IOC described above and this description applies correspondingly here. This embodiment of figures iOD-lOF in addition shows a fixation of the insert parts 72-73 by means of screws 53, as defined in the figures 7A to 7C and reference is made to their description provided herein. By tightening the screws 53, the two insert parts 72-73 form the waveguide profile in accordinace with the principle of the present invention as exposed herein. Preferably, the channel 75 comprises a additional free space 75' to facilitate the compression of the insert parts 72-73.

Figures 11A to 11C illustrate a further embodiment of an insert piece 78 where the waveguide 79 is placed on the side of the piece 78. Here the insert piece is made of two parts 78-81 and is inserted in the channel 80 of the matrix 77. Of course such an asymetricai construction is applicable to all embodiments detailed herein to any shape of insert

Figure 12 illustrates the preferred inner cross section of the waveguide that normally scales with the wavelength λ of the signal as approximately λ/2 by λ/4 to achieve optimal signal transmission.

The number of parts to form the insert piece is not limited to two but more than two may be used. In any case, one or several parts may be used in all embodiments described herein to form the insert piece and allow an easy forming of the channel with tight tolerances and high precision. Although the embodiments of figures 5A-5C, 6A-6C, 7A-7C are illustrated with complex shapes, a complex shape is applicable to all other embodiments described herein, or to any shape of insert piece and matrix with the same principles described above being applicable to embodiments where the insert piece is made of one or more parts.

Also, the use of two parts (or multiple parts] may also be combined with additional channels (as the channels 35-38 of figures 4A-4C).

The use of two (or more) parts construction is not limited to the insert piece but could also be used for the matrix of any embodiment described herein.

The parts of the device (matrix, insert] may be made in any suitable material for the desired purpose. They may be in metal, or synthetic (plastic) materials and plated. Any material that may be plated is suitable.

The embodiments given herein are for illustrative purposes and should not be construed in a limiting manner. Many variants are possible within the scope of the present invention,, for example by using equivalent means. The flanges mentioned in the present application are UG 387 type flanges but it is envisaged that other flanges may be used and the invention is not limited to this specific type of flanges.

Also, the different embodiments and variants may be combined together as wished with features of some embodiments being used in other embodiments.

Claims

1. A waveguide manufacturing method for waveguides used to transmit signals in the MMW, sub-MMW ranges at terahertz (THz) frequencies, wherein the method comprises at least the following steps:

-) providing an insert piece with a waveguide profile;

-) providing a matrix with a channel;

~) introducing said insert piece in said channel to form the waveguide.

2, The method as defined in claim 1, wherein the waveguide profile is rectangular.

3, The method as defined in one of the preceding claims wherein the waveguide profile is formed at least partly by the channel.

4, The method as defined in one of claim 1. or 2, wherein the insert piece comprises more than one part and the waveguide profile is formed by the insert parts.

5. The method as defined in one of the preceding claims, wherein the introduction is made by interference fitting, whereby the insert is conditioned at a much lower temperature than the outer object structure prior to the insertion step and the parts are then allowed to stabilise at similar temperatures such the insert will remain blocked tightly inside the channel.

6. The method as defined in one of claims 1 to 4, wherein the insert piece is fixed in the matrix channel by external means.

7. The method as defined in claim 6, wherein the external means comprise at least a screw.

8. The method as defined in one of the preceding claims wherein connection flanges are machined from the matrix.

9. The method as defined in one of claims 1 to 7, wherein the matrix is inserted in at least one connection flange.

10. A waveguide for transmitting signals at terahertz (THz) frequencies, wherein said waveguide comprises at. least a matrix and an insert piece having a waveguide profile, wherein said piece is inserted in said matrix.

11. The waveguide as defined in claim 10, wherein the matrix comprises a channel for the insertion of the insert piece.

12. The waveguide as defined in one of claims 10 or 11, wherein the insert piece is made of one single part or more than one part.

13. The waveguide as defined in one of claims 10 to 12 , wherein said waveguide profile is rectangular and one side of said waveguide profile is formed at least partly by the channel of the matrix or by a another part of the insert.

14. The waveguide as defined in one of claims 10 to 13, wherein additional channels are present in the matrix and/or the insert piece and/or formed by the insertion of the insert piece in the matrix.

15. The waveguide as defined in one of claims 10 to 14, wherein the matrix and the insert or the insert parts are made of metal or metal plated material,

16. The waveguide as defined in one of claims 10 to 15, wherein the matrix and/or the insert or insert parts have a simple shape and/or a complex shape.

17. The waveguide as defined in one of claims 10 to 16, wherein the outer shape of the i nsert or insert parts is identical to the inner shape of the channel of the matrix or is different from the inner shape of the channel of the matrix.

18. The waveguide as defined in one of claims 10 to 17, wherein it comprises connection flanges.

19. The waveguide as defined in claim 18, wherein the flanges are machined from the matrix, 20, The waveguide as defined in one of claims 10 to 19, wherein the waveguide profile has a complex shape for creating special effects, such as signal filters, resonant structures or packaging of active devices.