WO2010079180A1

WO2010079180A1 - Impedance matching assembly, electronic circuit, and related production methods

Info

Publication number: WO2010079180A1
Application number: PCT/EP2010/050076
Authority: WO
Inventors: Arnaud Curutchet
Original assignee: Institut Polytechnique De Bordeaux
Priority date: 2009-01-07
Filing date: 2010-01-06
Publication date: 2010-07-15
Also published as: EP2386131A1; FR2940859A1

Abstract

The invention relates to an impedance matching assembly (19), including: a wave guide (5) capable of guiding waves from or to a component (12); at least one impedance transformer (2) for the wave transition between the wave guide (5) and the component (12), wherein said assembly is characterised in that: the transformer (2) comprises a plate, the wave guide (5) including a slot (11) for removably receiving the plate of the transformer (2) with an electric contact between the plate of the transformer (2) and the walls of the slot (11). The invention also relates to an electronic circuit with such an assembly, and to related production methods.

Description

Impedance matching assembly, electronic circuit and related manufacturing processes

GENERAL TECHNICAL FIELD The invention relates to an impedance matching assembly for application in the field of electronics. The invention also relates to an electronic circuit with such an assembly. Finally, the invention relates to associated manufacturing methods.

Presentation of the prior art

There are four main types of transition between a waveguide and a component, said component comprising for example a microstrip line or a coaxial cable connector: probe transitions, patch transitions, transitions using a slot at the ground plane under the microstrip driver, and finally the transitions placed in the direction of propagation of the waveguide.

Transition devices are known in the propagation direction of the waveguide. In this type of transition, the waveguide and the microstrip line are oriented so that their modes of propagation are in the same direction. More precisely, this type of transition consists of a discontinuity between, for example, a microstrip line and a corrugated waveguide which is then transformed into a metallic rectangular waveguide. With this type of structure, the adaptation is performed with an impedance transformer, which is the transition between the waveguide and the microstrip line. The impedance transformer plays a decisive role in obtaining good electrical performance.

Document US Pat. No. 5,262,739 is known, and as represented in FIGS. 1A and 1B, an impedance matching device 19 comprising a waveguide, and an impedance transformer 2 formed of a plate for effecting the transition of wave between the waveguide 5 and an electronic component 12.

The plate comprises a transition edge 3 of curved shape, said transition edge 3 comprising a leading end 15, at which the waves arrive, and a trailing end 14, from which the waves are guided to the electronic component 12.

The trailing end 14 extends into a trailing edge 26.

A slot 110 is formed in a wall of the waveguide and has internal walls 27. The plate 2, on the side of the trailing edge 26, is then positioned in the slot 110, opposite the internal walls 27 of the slot 110. In this device, the combination, the positioning and the respective dimensions of the slot 110 and trailing edge 26 allow for a transmission line 25 waves to the electronic component 12. The walls 27 of the slot 110 act as a ground plane, and no electrical contact is provided between the transformer plate 2 and the walls 27 of the slot. In addition, the impedance transformer plate 2 is permanently attached to an inner wall of the waveguide opposite the wall in which the slot 110 is made. An identical solution is described in the scientific article "A Simple mm-Wave Transition from Waveguide to Coplanar Waveguide," Dalman G. C, Microwave Journal, Horizon House Publications, Norwood, MA, US, p.109-110, 112, vol.35, no.10, October 1992. Also known from US 5,408,188 an impedance matching device comprising an impedance transformer formed of a plate permanently attached to an inner wall of a waveguide. This plate comprises a curved transition edge, a trailing end is positioned at a slot in a wall of the waveguide. The slot is made in a wall opposite to the wall on which the plate is fixed. The trailing end of the plate is not in electrical contact with the slot.

In these solutions, the plate and slot are provided to provide a given impedance, and the plate is therefore permanently fixed in the waveguide.

Moreover, in some of the solutions proposed to date, the impedance transformer is made directly in the body of the transition. In addition, the thickness of the impedance transformer, which depends on the frequency of use, is often low (for example, at 94 GHz, the optimal thickness is of the order of 200 at 400μm). For all these reasons, these solutions make the mechanical realization of said impedance transformer tricky and complicated, which can have a negative impact on the electrical performance.

As shown in FIG. 2, FR 2 754 10 8 discloses a transition device between a waveguide 29, having a peak 30 forming an impedance transformer, and the microstrip line 31, said transition being carried out via a transformer of FIG. impedance with sinusoidal profile, machined directly in the waveguide 29.

A disadvantage of this solution is that the manufacture of the impedance transformer directly in the waveguide imposes a complex machining.

Another disadvantage is that this solution is expensive to manufacture.

Another disadvantage of this solution is that you can not easily change the impedance transformer and therefore you can not easily change the associated impedance.

Presentation of the invention

The invention proposes to overcome at least one of the aforementioned drawbacks.

For this purpose, an impedance matching assembly is provided according to the invention, comprising: a waveguide capable of guiding waves from or to a component; at least one impedance transformer for effecting the wave transition between the waveguide and the component, said assembly being characterized in that - the transformer comprises a plate, the waveguide comprising a slot adapted to receive the plate of the transformer removably.

The invention is advantageously completed by the following characteristics, taken alone or in any of their technically possible combination: the assembly comprises a plurality of impedance transformers, each plate of an impedance transformer comprising a transition edge following an impedance matching profile, different from the profile of a plate from another transformer, so that for a given frequency of use, one can adapt the transition impedance by inserting in the slot a plate corresponding to the desired impedance;

- It comprises means for adjusting the positioning of the impedance transformer plate in the slot, having pads integral with the transformer plate and cooperating with a wall of the waveguide and / or a control plate;

it comprises means for improving an electrical contact between the impedance transformer and the waveguide, and / or between the impedance transformer and the component;

it comprises means for reinforcing the reception of the impedance transformer plate in the slot, comprising an adhesive point, a weld, or a mechanical strength.

The invention also relates to an electronic circuit, comprising a component, said electronic circuit being characterized in that it further comprises an impedance matching assembly according to one of the preceding claims, connected to the component.

Finally, the invention proposes associated manufacturing methods, namely a method for producing an impedance matching assembly and a method for producing a corresponding circuit.

An advantage of the invention is to propose a transition between a waveguide and a component using an impedance transformer whose mechanical realization is simpler than the solutions of the prior art, and therefore efficient.

Another advantage of the invention is to propose an impedance transformer that can be easily interchangeable.

Yet another advantage of the invention is to provide a transition whose impedance can be easily changed to be adapted to the frequency of use and / or optimized to meet the desired specifications. Yet another advantage of the invention is to propose a solution that can be adapted to all types of waveguides and to all frequencies of use. Yet another advantage of the invention is to propose a solution that can make the transition between a waveguide and components of different technology. Finally, another advantage of the invention is to propose a solution that reduces manufacturing costs.

Presentation of figures

Other features and advantages of the invention will become apparent from the description which follows, which is purely illustrative and nonlimiting, and should be read with reference to the accompanying drawings in which:

- Figures 1, already commented, are representations of a solution of the prior art;

- Figure 2, already commented, is a representation of another solution of the prior art;

FIG. 3 is a diagrammatic sectional view of an impedance matching assembly according to the invention;

FIG. 4 is a side view of an impedance transformer optimized for 94GHz operation; FIG. 5 is a representation of an edge profile of an impedance transformer optimized for 94GHz operation;

- Figure 6 is a schematic sectional view of an impedance matching assembly according to the invention connected to a coaxial cable connector;

FIG. 7 is a diagrammatic top and side view of a portion of a WR10 waveguide with circular flanges;

FIG. 8 is a schematic top and side view of the step of a method according to the invention of digging in the waveguide of FIG. 6 a slot for receiving an impedance transformer and an opening. to receive a component; FIG. 9 is a schematic top and side view in the step of a method according to the invention of pre-positioning a component and an impedance transformer; - Figure 10 is a schematic top and side view of the waveguide in the step of a method according to the invention, wherein a component and an impedance transformer have been inserted into their respective housings;

- Figure 11 is a schematic top and side view of an embodiment of the invention wherein the waveguide guides the waves to and from a component.

FIG. 3 is a diagrammatic sectional view of an impedance matching assembly 19 according to the invention.

The assembly 19 mainly comprises a waveguide 5 capable of guiding waves, from or to a component 12 and at least one impedance transformer 2 for effecting the transition of the waves between the waveguide 5 and the component 12.

It is clear that the transition according to the invention can be carried out both from the waveguide to the component 12 and from the component 12 to the waveguide, as will be shown in FIG. 11. The impedance transformer 2 is positioned in a slot 11 formed in a wall 6 of the waveguide. The waveguide 5, by the presence of the slot 11, is able to receive the transformer 2 removably. The impedance transformer 2 is positioned in the slot 11 of the waveguide 5 so that, on the one hand, an end 14, referred to in this case of leakage, has a transition edge 3 on the side of the component 12, which is flush with it. the component 12 and secondly that another end15, called in this case of attack, its edge 3 on the side of the waveguide comes flush an inner face of the wall 6 of the waveguide 5.

As shown in FIG. 3, the waves to be transmitted from the waveguide to the component 12 arrive at the leading end of the transition edge 3 and are guided towards the leakage end 14 connected to the component 12, to be transmitted. As can also be seen in FIG. 3, the impedance transformer 2 plate is positioned in the slot 11 so that the leading end 15 is located at the internal walls of the slot 11. The end 14 leak is not located in this slot 11.

A side view of an exemplary impedance transformer 2 is shown in FIG. 4. The impedance transformer 2 comprises a plate whose shape is for example a parallelepiped but whose transition edge 3 follows a particular profile, such as the profile 1 of Figure 2, substantially sinusoidal. The profile 1 represents the shape of the transition edge 3 of the impedance transformer 2. The impedance transformer 2 plate geometry is purely illustrative, and different geometries can be used to realize the impedance transformer. These geometries are determined using electromagnetic simulation tools for a given operating frequency range and in order to obtain the best electrical performance.

The impedance matching assembly 19 of FIG. 3 furthermore comprises means 28 for adjusting the positioning of the impedance transformer plate 2 in the slot 11. The means 28 comprise, for example, holes 4 made in FIG. impedance transformer plate 2, in which one comes to insert pads 7 cooperating with the outer face of the wall 6 of the waveguide. The means 28 may also include a control plate, or any other mechanical assembly known to those skilled in the art.

As noted above, the waveguide 5 is adapted to receive the impedance transformer 2 removably. An advantage of the invention is to be able to have a plurality of impedance transformers 2, and thus to be able to optimize the impedance of the transition for a given frequency range of use, by inserting in the slot 11 a plate to synthesize the desired impedance. It suffices to manufacture the transition edge 3 of each impedance transformer plate 2 according to a matching profile 1 impedance, different from the profile of a plate of another transformer. The impedance matching is thus very flexibly achieved by the invention.

The impedance matching assembly 19 may advantageously comprise means 27 for improving an electrical contact between the impedance transformer 2 and the waveguide 5, and / or between the impedance transformer 2, and the component 12.

The electrical contact between the impedance transformer 2 and the component 12 at the end 14 of the transition edge 3 on the component side 12 of the impedance transformer 2 can be optimized by depositing silver glue, conductive glue, or solder.

Silver glue or solder may also be deposited at the portions of the impedance transformer 2 and the waveguide 5 which are in contact (eg at the slot 11 through which the transformer is inserted impedance 2 in the waveguide 5) to improve the electrical performance of the transition.

It should be noted that these means 27 do not call into question the removable nature of the impedance transformer 2 in the slot 11. Indeed, it is clear that a weld or a point of glue can easily be removed.

Furthermore, the impedance matching assembly 19 may include means 26 for reinforcing the reception of the impedance transformer 2 plate in the slot 11. Several solutions can be envisaged, for example the deposition of a point glue, or solder or mechanical strength. It should be noted that these means 26 do not call into question the removable nature of the transformer 2 impedance in the slot 11. Indeed, it is clear that a weld or a spot of glue can easily be removed. The impedance matching assembly 19 is advantageously used for forming an electronic circuit, as can be seen in FIGS. 3 and 6. Thus, the component 12 of FIG. 3 comprises in particular any planar circuit constituted by a support of a conductor, whether in microstrip technology (ground plane under the substrate), in coplanar technology (ground planes on both sides of the central conductor), in coplanar technology with ground plane or in technology suspended microstrip, and / or any type of electronic component, for example an electronic chip.

The component 12 may also comprise a coaxial cable connector, as can be seen in FIG. 6, which shows the impedance transition assembly 19 comprising the waveguide 5, the impedance transformer 2 inserted in the slot 11, and a body of the transition 8 between the waveguide 5 and the component 12, in this case a coaxial cable connector.

Manufacturing methods of the invention will now be described. FIG. 7 is a schematic top and side view of a portion of a WR10 type circular waveguide 60 mm long with walls 1 mm thick (scale 2 to 1). , comprising at least one wall 6. The manufacturing processes will be described on this waveguide 5 in a purely illustrative manner. Indeed, an advantage of the invention is that it can be adapted to all types of waveguides and therefore to all frequency ranges. In addition to the waveguides WR10, there may be mentioned by way of example but in a nonlimiting manner the guides WR12, WR15, WR19, WR22, WR28 and WR42, with rectangular or circular flanges.

In one step of the method, the impedance transformer plate 2 is manufactured as shown in FIG. 4. This impedance transformer 2 is optimized for operation at 94 GHz. In this exemplary embodiment, the impedance transformer 2 was made of a 300 μm thick brass sheet. It is possible to realize the impedance transformer 2 in different materials such as brass, aluminum, gold or any other metal or alloy. The realization of the impedance transformer can be done with a control machine digital type LPKF (printed circuit recorder), or by laser cutting, or by cutting by water jets, or by cutting by milling machine, or by cutting by digital milling machine, or by molding or by any other known technique of l skilled person. Whatever the technique used to make the impedance transformer 2, an advantage of the invention is to be able to perform these operations not in the body of the waveguide but on a sheet of metal or alloy external to the assembly, which greatly facilitates the realization, and reduces manufacturing costs. The transition edge 3 of the impedance transformer plate 2 is produced by following the impedance matching profile 1 of FIG. 5. In this exemplary embodiment, the profile 1 of the edge 3 of the impedance transformer 2 has a cosine profile, the dimensions of which are: 10 mm long 1.12 mm high - 300μm wide

In Figure 8 there is shown a step of the method of forming a slot 11 in the wall 6 of the waveguide, the slot 11 being adapted to receive the plate of the transformer 2 removably. A slot 11 of thickness e (corresponding to the thickness of the impedance transformer 2) and of length L 2 (corresponding for example to the length of the impedance transformer 2, but other lengths being possible) is made to allow inserting the impedance transformer 2 into said slot 11 of the waveguide. In addition, an opening 10 of length L1 and depth P is provided on the waveguide, in order to insert a component 12. The length L1 is determined as a function of the component 12 that is to be inserted, and of the game needed for editing. In this embodiment, it is a planar circuit composed of a microstrip line 13 at the input of a chip 17, which will be represented in FIG. 9. It may equally well be a chip 17 only, without intermediate microstrip line. In this embodiment, the depth P of the opening 10 is such that two side walls of the waveguide at the opening 10 are completely machined. FIG. 9 shows the extension of the microstrip line 13 and the chip 17 in the opening 10 of the waveguide 5. This postponement can be done by gluing or welding.

FIG. 9 also illustrates the prepositioning of the impedance transformer 2 above the slot 11 of the waveguide 5. The impedance transformer 2 is such that its edge 3 cut according to the profile 1 is ready to be inserted first in the slot 11, in the direction of the arrow indicated in the figure.

FIG. 10 illustrates the implementation of the impedance transformer 2 in the slot 11 made in the waveguide 5. As previously stated, there are various means 28 for adjusting the positioning of the impedance transformer plate 2 in the slot 11. In this embodiment, pads 7 are inserted into the holes 4 of the impedance transformer plate 2, in order to position the impedance transformer 2 in the slot 11. In this embodiment, the Microstrip line 13 is at the input of chip 17, and the two elements are connected by a bonding type connection 16. Gilding gold can also be deposited to improve electrical performance. Moreover, the end 14 of the edge 3 of the impedance transformer 2 intended to be brought into contact with the component 12 (here the microstrip line 13) may have a small protrusion (of the order of 50 μm for an application at 94 GHz ) so as to optimize the bearing surface on the microstrip line 13 while improving the electromagnetic performance of the transformer, and therefore their electrical contact. Several forms of growth can be used.

The assembly of FIG. 10 thus forms a circuit in which the waves are transmitted from the waveguide 5 to the component 12 or from the component 12, via the impedance transformer 2.

In FIG. 11, a second impedance transformer 2 has been positioned in a second slot 11 at the output of a second microstrip line 13, said second microstrip line 13 itself being positioned at the output of the chip 17. FIG. 11 also illustrates the transfer of the waveguide 5 onto the main body of a housing 20. It is also possible to position a cover that makes it possible to protect the component 12 on the one hand from the outside environment, and other hand electromagnetic disturbances. The mechanical strength of the waveguide 5 on the body of the housing 20 is made for example by two collars 18. The assembly may also include fasteners provided to accommodate a radiator for cooling the component 12. The above developments s' advantageously apply to a commercially available waveguide, but any waveguide, for example made in two pieces (or more), is also conceivable in the invention. The device according to the invention is intended for all applications of electronics using waveguides for transporting electrical signals, and this at all frequencies of use.

Claims

claims

An impedance matching assembly (19) comprising: a wave guide (5) adapted to guide waves from or to a component (12); at least one impedance transformer (2) for effecting the wave transition between the waveguide (5) and the component (12), said transformer having a plate, said assembly being characterized in that the waveguide (5) comprises a slot (11) removably receiving the transformer plate (2), with electrical contact between the transformer plate (2) and the walls of the slot (11).

2. An assembly according to claim 1, comprising a plurality of impedance transformers (2), each plate of an impedance transformer (2) comprising a transition edge (3) according to a profile (1) of adaptation of impedance, different from the profile of a plate of another transformer, so that for a given frequency of use, one can adapt the transition impedance by inserting in the slot (11) a plate corresponding to the desired impedance.

3. An assembly according to any one of the preceding claims, comprising means (28) for adjusting the positioning of the impedance transformer plate (2) in the slot (11), comprising studs (7) integral with the plate. of the transformer (2) and cooperating with a wall (6) of the waveguide and / or an adjustment plate.

4. An assembly according to any one of the preceding claims, comprising means (27) for improving an electrical contact between the impedance transformer (2) and the waveguide (5), and / or between the impedance transformer (2) and the component (12).

5. An assembly according to any one of the preceding claims, comprising means (26) for reinforcing the reception of the impedance transformer plate (2) in the slot (11), comprising an adhesive point, a weld, or mechanical strength.

6. An electronic circuit, comprising a component (12), said electronic circuit being characterized in that it further comprises an impedance matching assembly according to one of the preceding claims, connected to the component (12).

The circuit of claim 6, wherein the component (12) comprises a planar circuit or a coaxial cable connector.

A method of making an impedance matching assembly (19) comprising the steps of: providing a waveguide (5) capable of guiding waves from or to an electronic component (12) said method being characterized in that it comprises the steps of:

providing at least one impedance transformer (2) for effecting the wave transition between the waveguide (5) and the component (12), the transformer having a plate;

forming a transition edge (3) on an edge of the transformer plate according to an impedance matching profile (1);

- Form a slot (11) in the waveguide (5), the slot (11) being adapted to receive the plate of the transformer (2) removably. - Position an impedance transformer (2) in the slot (11), creating an electrical contact between the impedance transformer (2) and walls of the slot (11).

The method of claim 8, wherein forming the transition edge comprises a step

- machining with a numerically controlled machine of the LPKF type (printed circuit board), and / or - laser cutting, and / or

- cutting by jets of water, and / or

- Milling cutter, possibly digital, and / or

- a molding.

10. A method of producing a circuit, characterized in that it comprises the steps of:

- providing an assembly made by a method according to one of claims 8 to 9;

forming an opening (10) in the waveguide; and - positioning a component (12) in the opening (10).