EP0928041A1 - Transition between a waveguide and a coplanar line - Google Patents

Abstract

The invention relates to a transition between a coplanar line and a guide. of waves, for microwave device. The coplanar line includes a line (1) and a ground plane (2) arranged on one face of a substrate (3); transition is defined by a patch (3) arranged on the face of the substrate opposite the line (1), so as to be electro-magnetically coupled to the line, through the substrate. A waveguide (6) is placed around the patch, so that the patch radiates into the waveguide.

The invention allows easy manufacture and simple assembly of the transition.

Description

The subject of the present invention is a transition between a waveguide and a coplanar line.

The invention relates to the field of microwave or microwave circuits. More specifically, it concerns the transitions between various types of conductors microwave or microwave, namely the transitions between the coplanar lines and waveguides. A passive microwave component is called "transition" allowing to pass from a signal propagation medium to another.

Various types of transitions have already been proposed. An article by W. Grabherr, B. Huder and W. Menzel, Microstrip to waveguide transition compatible with MM-wave integrated circuits, IEEE Short papers 1994, describes a transition between a micro-ribbon line and a waveguide. This transition is based on the principle of a formed antenna a slot in the ground plane of the micro-ribbon line, which emits in the guide wave. Energy is coupled from the microstrip line through the slit in the plane mass, to a radiant element or "patch" located in the waveguide on a substrate additional. This technique does not apply directly to coplanar links; in addition, it requires two substrates, and an assembly of the substrate carrying the patch in the waveguide.

Another known solution is that of crest waveguides. waveguides). These waveguides, to allow coupling with a line coplanar or a micro-ribbon line, have a mechanical crest allowing a contact with the coplanar line, or with a suspended micro-ribbon circuit. An example of crested waveguide is given in the French patent application filed at applicant's name on 01.10.96 under number 9611941, under the title "Transition between a crest waveguide and a planar circuit ".

This type of transition has the disadvantage of requiring complex machining waveguide to form the ridge; it also involves a complicated assembly of the liaison. The solution presented in the aforementioned patent application overcomes the latter disadvantage; it does not overcome the machining constraint of the crest of the waveguide.

Transitions with localized constants have also been proposed, presenting a dimension smaller than the guided wavelength. Such transitions are usually formed by a probe entering the waveguide, perpendicular to the direction of extension of this waveguide and connected to a planar circuit. The probe may consist of the core of a coaxial circuit or of the end of a metal line etched on a substrate whose other end is locally demetallized. The disadvantage of this type of transition is that it requires a 90 ° change of direction of the microwave signal. and that the size of the transition is important. These transitions are difficult to implement and do not do not have a wide adaptation band. Finally, these transitions are of a montage delicate, and always include a lid with a hollow or the like allowing looping of the circuit.

Various examples of such transitions consisting of probes are described in a article by Yi-Chi Shi and others, Waveguide to microstrip transition for millimeter-wave applications, IEEE MTT-S Digest, 1988, pages 473-475.

Finally, US-A-5,043,683 describes a transition between a microstrip line and a waveguide intended to receive orthogonal polarizations. In this document, he it is suggested that the ground plane of two microstrip lines stop at the wall of the waveguide, while the ends of two microstrip lines cross the wall of the waveguide and are capacitively coupled at the end by a series spacing on the adjacent sides of a square patch in the waveguide. In practice, the wall of the waveguide has a thickness of a quarter wavelength, so as to be transparent to the signals passing through it, and the refined ends of the micro-ribbon lines are close but distinct from the edges of the square patch. This solution notably involves closing the waveguide with an active cover as a short circuit. This document proposes a solution for a transition between two micro-ribbon lines and a circularly polarized waveguide, but does not offer no suggestion for a coplanar line or a classic waveguide. In this transition, the short circuit which closes the end of the waveguide acts as a plane of mass of the patch.

The invention proposes a transition between a coplanar line and a waveguide, which is simple to implement, and which in particular does not involve machining complex of mechanical parts and can be assembled easily. The invention makes possible the use of a single substrate, and thus provides a costly solution reduced.

More specifically, the invention proposes a transition between at least one line coplanar and a waveguide, the coplanar line comprising a line and a plane of mass arranged on one face of a substrate, characterized in that it comprises a patch arranged on the face of the substrate opposite the line, so as to be electro-magnetically coupled to the line, and in that is the patch is surrounded by the waveguide.

In one embodiment, the waveguide has a circular section, square or rectangular.

In one embodiment, the patch is square or circular.

Advantageously. the transition includes a second line on the same side of the substrate as said line, which extends perpendicular to said line.

In this case, it is preferable that the patch has a square shape, than the so-called line extends substantially opposite one side of the patch, and the second line extends substantially opposite an adjacent side of the patch.

Preferably, the substrate is made of a gas and water tight material, such as ceramic, sapphire or quartz.

The invention also relates to a substrate having on one of its faces at minus a coplanar line with a line and a ground plane, and on its other face a patch electro-magnetically coupled with the line.

Advantageously, the patch is square or circular.

In one embodiment, the substrate comprises a second line on the same face of the substrate as the said line, and which extends perpendicular to the said line.

In this case, the patch preferably has a square shape, the so-called line extends substantially opposite one side of the patch, and the second line extends substantially opposite an adjacent side of the patch.

Advantageously, the substrate is made of a gas and water tight material, such as ceramic, sapphire or quartz.

• la transmission du signal depuis la ligne vers un patch situé du coté du substrat opposé à la ligne, par couplage capacitif à travers le substrat;
• le couplage du signal depuis le patch par rayonnement dans le dit guide d'ondes.

The subject of the invention is finally a method of transmitting a microwave signal to a waveguide from a coplanar line comprising a line and a ground plane arranged on one face of a substrate, comprising

• transmitting the signal from the line to a patch located on the side of the substrate opposite the line, by capacitive coupling through the substrate;
• the coupling of the signal from the patch by radiation in the said waveguide.

• figure 1, une vue schématique de dessus d'une transition selon l'invention entre une ligne coplanaire et un guide d'onde;
• figure 2, une vue schématique en coupe de la transition de la figure 1;
• figure 3, une vue schématique d'un autre mode de réalisation d'une transition selon l'invention.

Other characteristics and advantages of the invention will appear on reading the following description of an embodiment of the invention, given by way of example and with reference to the figures which show:

• Figure 1, a schematic top view of a transition according to the invention between a coplanar line and a waveguide;
• Figure 2, a schematic sectional view of the transition of Figure 1;
• Figure 3, a schematic view of another embodiment of a transition according to the invention.

Figure 1 shows a schematic top view of a transition along the invention, between a coplanar line and a waveguide. We see in the figure the line 1 surrounded by its ground plane 2. In the vicinity of its end, the coplanar line 1 is electromagnetically coupled through the substrate 3 to a patch 5 arranged in wave guide 6; in the example of FIG. 1, the waveguide 6 presents a rectangular section. but this is in no way necessary for the implementation of the invention. The waveguide could also have a circular or square section. In the example in the figure, the patch is square; it could also be circular.

Figure 2 shows a sectional view of the transition from Figure 1, in the plane II-II of Figure 1; we recognize in Figure 2 the walls 7 and 8 of the waveguide 6; the ends of the walls of the waveguide are adjacent or fixed to the substrate 3, by conventional fixing means. On the underside of the substrate 3 facing the guide wave 6 is provided the patch; on the opposite side to the waveguide 6, we recognize the ground plane 2 and the coplanar line 1.

The operation of the device of Figures 1 and 2 is as follows. The signal microwave transmitted on the coplanar line is electromagnetically coupled to the patch 5, through substrate 3. Patch 5 acts as an antenna, and radiates the signal in the waveguide; the patch's ground plan is made up of the ground plan of the coplanar line.

In the example of Figures 1 and 2, the coplanar line extends opposite one side of the patch. on the opposite side of the substrate, over about a quarter of the dimension of the patch in a longitudinal direction of the line; this is a value that turns out suitable, especially for the assembly of FIG. 3. It is however clear that the capacitive coupling between the patch and the coplanar line does not require this relative position of these two elements, and the line may not extend above the patch, or still cross it completely; the choice of the exact relative position of the patch and the line can be determined in each application by the skilled person, depending constraints encountered, for example with the help of known simulation software in itself.

In the transition of the invention, the ground plane of the patch is formed of the plane of mass of the coplanar line. The invention thus ensures great simplicity of fabrication and assembly of the link; it also ensures electromagnetic confinement of the wave; in particular, it does not involve manufacturing a mechanical part short-circuit to achieve closure of the waveguide 6 and to bring a maximum electric field on a probe.

The coupling between the coplanar line and the patch depends on the permittivity relative dielectric of the substrate; the bandwidth of the transition depends in this measurement of the nature of the substrate chosen. This is not a limiting factor in the measurement where the range of existing substrate makes it possible to find for the different values possible bandwidth a suitable value of the permittivity.

The invention of Figures 1 and 2 thus allows a simple and effective coupling of a coplanar line in a waveguide; this coupling is easy to manufacture, and easy assembly. It does not require any mechanical parts. The transition is sealed or waterproof if the substrate does not allow the passage of gases or water, which is in particular the case for a ceramic, quartz or sapphire substrate.

Figure 3 shows a schematic view of another embodiment of a transition according to the invention. The embodiment of the invention makes it possible to couple in a waveguide two orthogonal polarizations, thanks to two lines distinct perpendicular coplanar. The device of Figure 3 is identical to that in FIG. 1, except that it has a second coplanar line 10, perpendicular to line 2, and which electromagnetically couples to patch 5 on one side of it adjacent to the side on which line 2 is coupled. in addition, the waveguide of Figure 3 has a square section; he could also present a circular section.

The operation of the device of Figure 3 is as follows; lines 1, 10 carry signals which radiate in the waveguide with polarizations orthogonal in planes containing respectively the plane of each of the lines. This ensures coupling in the waveguide of orthogonal polarizations. We can provide right or left circular polarization in a waveguide sending on each of the lines 90 ° phase shifted signals.

The solution of Figure 3 avoids complex mechanical devices, and allows direct coupling on two orthogonal polarizations in the waveguide.

Of course, the present invention is not limited to the examples and methods of realization described and represented, but it is susceptible of numerous variants accessible to those skilled in the art. Thus, the invention applies to all types of guides waves, and not only those shown in Figures 1, 2 and 3; so we can do vary the section of the waveguide and the shape and size of the patch depending on the constraints specific to each application of the invention, and in particular the frequency wanted. It is also clear that the transition of the invention can be used to move from a propagation medium other than a coplanar line to a guide waves, via a coplanar line; we can thus pass classically from one line micro-ribbon to a coplanar line, then use the transition according to the invention to go through a waveguide. Another material can be used for the substrate, for example example an organic substrate; in this case the transition is not necessarily hermetic.

Claims (12)

Transition between at least one coplanar line and a waveguide, the line coplanar comprising a line (1) and a ground plane (2) arranged on one face of a substrate (3), characterized in that it comprises a patch (3) disposed on the face of the substrate opposite the line (1), so as to be electromagnetically coupled to the line, and in that the patch is surrounded by the waveguide (6). Transition according to claim 1, characterized in that the waveguide has a circular, square or rectangular section. Transition according to claim 1 or 2, characterized in that the patch is square or circular. Transition according to one of claims 1 to 3, characterized in that it comprises a second line (10) on the same face of the substrate as said line, which extends perpendicular to said line (1). Transition according to claim 4, characterized in that the patch has a square shape, in that said line (1) extends substantially opposite one side of the patch, and in that the second line (10) extends substantially opposite one side adjacent to the patch. Transition according to one of Claims 1 to 4, characterized in that the substrate is made of a gas and water tight material, such as ceramic, sapphire or quartz. A substrate (3) having on one of its faces at least one coplanar line with a line (1) and a ground plane (2), and on its other face a coupled patch electro-magnetically with the line. Substrate according to claim 7, characterized in that the patch is square or circular. Substrate according to claim 7 or 8, characterized in that it comprises a second line (10) on the same face of the substrate as said line, and which extends perpendicular to said line (1). Substrate according to claim 9, characterized in that the patch has a square shape, in that said line (1) extends substantially opposite one side of the patch, and in that the second line (10) extends substantially opposite one side adjacent to the patch. Substrate according to one of Claims 7 to 10, characterized in that the substrate is made of a gas and water tight material, such as ceramic, sapphire or quartz. Method for transmitting a microwave signal to a waveguide from a coplanar line comprising a line (1) and a ground plane (2) arranged on one face of a substrate (3), comprising transmitting the signal from the line (1) to a patch (5) located on the side of the substrate opposite the line, by capacitive coupling through the substrate; the coupling of the signal from the patch by radiation in the said waveguide.

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