EP1867003B1 - High-frequency coupler or power splitter, especially a narrow-band 3db coupler or power splitter - Google Patents

Abstract

An improved HF coupler or HF power splitter comprises four connection lines arranged on the same side of the substrate. Two coupling zones are formed on the substrate on two opposite sides; the second coupling zone is connected to the associated connection lines arranged on the side of the substrate opposing the coupling zone, by means of two via holes in an electroplated manner. The capacitors provided at the beginning and at each end of each coupling zone are respectively embodied as interdigital capacitors; and the capacitors are respectively coupled to earth.

Description

The invention relates to an RF coupler or RF power divider, in particular narrow-band RF coupler or RF power divider according to the preamble of claim 1, known from the US 2005/0017821 A1 ,

In high-frequency systems, it is often necessary to split a signal, for example with a power P, into two signals with a power of P / 2 each. Ring couplers are often used for this purpose. Such ring couplers are for example from prong Brunswig " High Frequency Technology ", Springer-Verlag, 6th edition, 2000 known, from page 192.

These ring couplers are often implemented in microstrip technology.

In addition, however, high-frequency couplers are also known in which the degree of coupling is generally set via front-end or longitudinally coupled lines. For higher coupling levels, as necessary for a power divider, these distances are often very low or even too low to be economically manufactured.

For example, from the EP 1 291 959 A1 a directional coupler has become known, for example is constructed in suspended substrate technology. In other words, a coupling path in stripline technology is provided on a substrate on one side, which are connected to two also in stripline technology formed first and second terminals on the substrate in combination. On the opposite side then a second coupling path is arranged, which lead to a third and fourth output or connection. In plan view, the two coupling paths are arranged at least partially overlapping.

According to the aforementioned prior publication EP 1 291 959 A1 can also be connected at the two opposite ends of the two coupling paths also each capacitors, the second connection point is in each case to ground.

From the same prior publication but other embodiments can be seen, in which the coupler is constructed in Koplanartechnik. In this case, the two coupling lines are each arranged with their two connection points on a common side of the substrate, wherein the coupling paths extend in the smallest possible distance parallel to each other.

Finally, but also for example from the EP 1 014 472 B1 a directional coupler has become known, which in turn is also constructed in suspended substrate technology. It is in this prior art directional coupler to a broadband directional coupler with at least two coupled in cascade coupling sections of different coupling loss, in which the coupling sections with loose coupling of frontally coupled strip conductors and the Coupling sections with fixed coupling consist of broadside coupled strip conductors.

In order to realize the corresponding coupling path with a fixed coupling vias are provided in the substrate in this embodiment. However, all leads are arranged on one side of the substrate.

With regard to the couplers known from the prior art, it can thus be stated that they are often designed in microstrip technology. Due to the relatively high attenuation of the microstrip line and their sensitivity to variations in the dielectric constant, the disadvantages of these couplers are the high space requirements and the relatively large electrical losses and the high cost of high-quality printed circuit board material.

The disadvantages of the directional coupler in suspended substrate technique are on the one hand high demands on the positioning of the substrate between the two ground surfaces (problems exist here with the correct positioning in the horizontal but also with regard to the exact consideration of the distances between the lid and bottom). These requirements for correct or optimal positioning cause high costs for mechanical processing and assembly. On the other hand, when designing a coupler, this already determines the case geometry. This is often disadvantageous in terms of reusability or achievement of sufficient flexibility with regard to the realization and implementation of a selected concept for a coupler and for use in other applications.

In addition, it is difficult from an electrical point of view in this technique to compensate for the different phase velocities of the DC and push-pull wave.

The main disadvantages of the directional coupler in coplanar technology are ultimately in the required minimum distances between the longitudinally coupled interconnects and the extent also limited coupling factor. Furthermore, the coupling factor is highly tolerance-dependent (etching tolerances and variations in the dielectric constants of the substrate material exert an adverse influence). Furthermore, a coplanar coupler is not optimal in terms of electrical losses.

As explained above, it is disadvantageous for all three types of couplers that, in particular when used for a modern telecommunications system, they do not have the requisite required properties of a high-frequency coupler, such as e.g. have sufficiently suitable coupling factor, directivity or symmetry or are not feasible or only with considerable development effort.

From the GB 2 218 853 A Further, a high-frequency coupler or power divider is known to be known, which comprises on a substrate on one side two formed coupling links. Both coupling lines are provided at the beginning and at the end with connecting conductors, which lead to staggered terminals. In addition, capacitors for coupling both coupling paths are provided and formed between the two coupling paths.

From the EP 1 014 472 B1 is also a directional coupler as to be known. In contrast to the generic state of the art, this directional coupler is formed on a substrate so that the one coupling path on one side of the substrate and the coupled therewith second coupling path is formed on the opposite side of the substrate. In this case, a through connection through the substrate is provided in each case on one side of the coupling path in order to produce an electrical-galvanic connection of a connecting line to an opposite coupling surface.

From the US 4,376,921 Furthermore, a microwave coupler is known to be known, which also has four ports and two coupling links, between the two coupling links - which are kept relatively short - from the beginning to the end capacitors are provided for coupling between the coupling links.

A disadvantage of all types of couplers mentioned above is that, in particular when used for a modern telecommunications system, they do not have the requisite required properties of a high-frequency coupler, for example with sufficient coupling factor, sufficient directivity or symmetry or can not be realized or only with considerable development effort. A generic coupler or power divider is from the US 2005/0017821 A1 known. On the substrate, two first connecting lines are provided, which lead to a beginning and to an end of a first coupling path. Furthermore, a second, coupled to the first coupling path coupling path is provided, leading to the beginning and the end of two further connection lines.

The aforementioned two coupling paths are formed on the substrate on two opposite sides, wherein the entire arrangement rests with the lower coupling path on a lower substrate.

From the US 2004/0113717 A1 a further coupler is known to be known, for example, includes grounded interdigital capacitors, which serve to improve the electrical property.

It is therefore an object of the present invention, starting from the generic state of the art, to provide an improved coupler or power divider, in particular to provide a narrow-band, preferably 3dB coupler which is optimized in terms of cost, size, losses and manufacturing tolerances over conventional solutions.

The object is achieved according to the features specified in claim 1. Advantageous embodiments of the invention are specified in the subclaims.

The RF coupler or power divider according to the invention has a number of positive advantages that offset conventional solutions. The high-frequency coupler according to the invention has a narrowband design.

The coupler according to the invention or power divider has at the respective opposite end or connection areas to the respective coupling path capacitors, as in principle also from the EP 1 291 959 A1 are known. In deviation, however, are not discrete Reactants or capacitors used, but so-called interdigital capacitors. Although reveals the US 2004/0113717 A1 a coupler with grounded interdigital capacitors, but here a second substrate is provided without vias.

By the solution according to the invention, a power divider or coupler is realized with very little space, the electrical parameters are relatively freely adjustable or preselected within wide limits. Above all, it has low electrical losses. In addition, the power divider or coupler according to the invention is also characterized by its high directivity. Above all, the fact that the coupler or power divider according to the invention - which is usually installed in a housing - also in the region of the lower coupling path a distance from the housing, i. has a housing wall, in this case no fixed dielectric is provided immediately adjacent, can be realized and achieve a lower ε, which has a positive impact on the electrical properties of the coupler or power divider reflected. As a result, the coupler or power divider according to the invention has further advantages over the generic state of the art.

The coupler or power divider according to the invention is also comparatively robust with respect to housing tolerances. This is especially evident in the choice of different cover distances. This robustness to housing tolerances also opens the possibility to reuse individual designs in other applications. In addition, the coupler according to the invention is also comparatively robust to etching tolerances as well as to fluctuations in the Dielectric constant of the substrate material. Furthermore, basically no further wiring or concentrated components are necessary, although they could basically be used if necessary. Finally, all leads are provided on the same side of the substrate side, which is to be regarded as advantageous.

Figur 1:

eine schematische Draufsicht auf ein erstes Ausführungsbeispiel eines erfindungsgemäßen Kopplers;

Figur 2:

eine rückseitige Ansicht des in Figur 1 wiedergegebenen erfindungsgemäßen Kopplers;

Figur 3:

einen Schnitt längs Figur 1;

Figur 4:

eine zu Figur 1 entsprechende Darstellung bezüglich eines gegenüber Figur 1 leicht abgewandelten Ausführungsbeispieles;

Figur 5:

eine rückwärtige Ansicht auf das Ausführungsbeispiel gemäß Figur 4.

Further advantages, features and details of the invention will become apparent hereinafter from the embodiments illustrated with reference to drawings. Show in detail:

FIG. 1:

a schematic plan view of a first embodiment of a coupler according to the invention;

FIG. 2:

a back view of the in FIG. 1 reproduced inventive coupler;

FIG. 3:

a section along FIG. 1 ;

FIG. 4:

one too FIG. 1 corresponding representation with respect to one opposite FIG. 1 slightly modified embodiment;

FIG. 5:

a rear view of the embodiment according to FIG. 4 ,

In FIG. 1 the plan view of a first embodiment of a coupler according to the invention or power divider 1 is shown, which is constructed on a substrate 3 in the form of a printed circuit board.

On the substrate 3 are on the in FIG. 1 Visible top surface 3a of the substrate four surface regions 5 visible, which are electrically-electrically isolated from recesses 7 from each other. This surface area 5 is a ground area 5.

In the recesses 7, a first coupling path 9 is formed in stripline technique, which extends in a first direction or longitudinal direction on the substrate 3.

At the beginning 11a and at the end 11b of this coupling path 9, a first and second connection line 13a and 13b is provided transversely, which lead to connections 15a and 15b on the one substrate edge 3 '.

The non-conductive recessed area 7 is in plan view in the embodiment according to FIG. 1 H-shaped. In the immediate extension of the connecting line 13a and 13b but separated from these, two more connecting lines 17a and 17b are seen, leading to the opposite substrate edge 3 "and there form connections 19a and 19b.

At the ends of the connection lines 17a, 17b which are opposite to the connections 19a and 19b, these are provided adjacent to the first coupling path 9 with plated-through holes 21, which extend through bores 21 'through the substrate 3.

As in particular from the bottom view FIG. 2 can be seen, a second coupling path 25 is provided on the reproduced there underside 3b, which runs parallel to the first coupling path 9 and in plan view itself preferably with this completely or at least partially overlapped. The length and / or width of both coupling paths is at least approximately the same in the embodiment shown.

As seen from the bottom view 3b of the substrate 3 according to FIG. 2 can be seen, at the beginning 27a and at the end 27b of the second coupling path 25 corresponding to the second coupling path two electrically connected and formed in stripline technology line extensions 25 'provided in the middle of the holes 21' of the feedthrough 21 ends. As a result, the second connection lines 17a and 17b are electrically-galvanically connected to the second coupling path 25 via the aforementioned two plated-through holes.

The length of the coupling lines corresponds to approximately λ / 4. The four supply or connecting lines 13a, 13b and 17a, 17b are implemented in coplanar conductor technology and connect the coupler 1 with further in the present embodiment, not shown in detail high-frequency modules.

To improve the electrical properties, a total of twelve capacitors C are also provided in the illustrated embodiment, which in each case in the input and output area, ie at the beginning 11a and at the end 12b of the first coupling path 9 or at the beginning 11'a and at the end of the 12th 'b the second coupling path 25 are located. There, therefore, the capacitors C-9a and C-9b are arranged at one end and the corresponding capacitors C-9c and C-9d at the other end of the first coupling path 9. Corresponding capacitors are also provided at the beginning and end of the second coupling path 25, namely the capacitors C-25a and C-25b and at the opposite end of the coupling path 25, the capacitors C-25c and C-25d. These capacitors are not constructed using discrete components but in the form of interdigital capacitors.

Out FIGS. 1 and 2 However, it is also apparent that in the illustrated embodiment, preferably in the middle region, ie halfway along the respective coupling path 9 or 25 is still provided in each case a further capacitor pair C, which in the embodiment shown as C-9e and C-9f as well C-25e and C-25f.

In the case of the capacitors, in each case one capacitor surface or half is conductively connected to the respective coupling path 9 or 25 and the respective electrically-galvanically separated capacitor surface or half interacting therewith has the associated ground surface.

This is also on the bottom according to FIG. 2 the substrate 3 is provided with a circumferentially closed ground surface 31, in the central region of a non-conductive recess 36 is provided within which the longitudinal direction of the second coupling path 2 thereof is galvanically separated.

The dimensioning of the interdigital capacitors can be carried out in such a way that specific coupling properties are set or preselected. However, the aforementioned ground planes are necessary in order to ensure defined mass ratios on the one hand and to form a ground potential for the interdigital capacitors on the other hand. The actual coupling takes place through the formed on the two sides of the substrate 3 lines 9 and 25 (suspended substrate).

As is apparent from the cross-sectional view according to FIG. 3 shows, a recess 37 is formed in a housing 29 below the coupling region, ie a distance 37 to a corresponding housing wall 29 is provided. The extent of the depression, that is the degree of the distance between the substrate and the housing or the housing wall 29 and the distance between the substrate and the associated lid 41 can be freely selected within certain limits.

Notwithstanding the embodiment shown, the capacitors provided preferably in the middle in the coupling paths may also be provided, starting from the center, between the capacitors provided at the beginning and at the end of the respective coupling path. If appropriate, additional capacitors may also be provided between the capacitors provided at the beginning and at the end region of the respective coupling path, that is, more than in the exemplary embodiments shown.

Based on the total coupling length from the initial region 11a to 12b and from the initial region 11'a to the end region 12'b, the input and output capacitors C-9a, C-9b and C-9c, C-9d and on the opposite Side the capacitors C-25a, C-25b or C-25c, C-25d are also more offset to the center. For example, the distance from the beginning and end regions may well be up to 30% of the total length of the coupling path, but preferably less, in particular less as 25%, 20%, 15% and 10% of the total length of the coupling path. It should be noted that the positioning of the capacitors at the beginning and at the end of the coupler have the greatest effect.

The embodiment according to FIGS. 4 and 5 corresponds largely to that after the FIGS. 1 to 3 ,

The only difference is that, for example, in the plan view of the substrate comparable to the embodiment according to FIG. 1 the lying on one side of the substrate coupling path 9 is not provided with two leading to the same edge boundary 3 'of the substrate connection lines, but the in FIG. 4 right lying connection line 15b, which is electrically-galvanically connected to the coupling path 9, leads to the opposite side 3 "of the substrate to the connection 17b formed there FIG. 4 top right connection line 17 b provided with a through-connection 21, so that the in FIG. 4 top right terminal 19b with the in FIG. 4 bottom left terminal 19a is electrically-galvanically connected.

It therefore follows from the exemplary embodiments explained that the ground areas have recesses 7 on both sides of the substrate in the area of the connection lines as well as the coupling sections 9 and 25. The distance between the coupler paths 9 and 25 and the ground planes is preferably 1.5 to 4 times the width of the line. Likewise, the distance of the connection lines to the adjacent ground planes is approximately 1.5 to 4 times the width of these connecting lines.

As also mentioned, the coplanar coupling lines 9 and 25 are suitably arranged to achieve the desired coupling. In plan view of the substrate, ie perpendicular to the substrate plane, therefore, both coupling lines 9, 25 should either lie one above the other or have a lateral offset, which is preferably smaller than the width of the coupling line. Thus, the coupling lines are not adjacent to each other in plan view, but overlap. Preferably, the lateral offset is greater than half the width of the coupling conductor track 9 or 25, so that cover both lines at preferably the same width to fifty percent. In other words, the coverage should preferably be more than 0%, in particular more than 10%, more than 20%, more than 30% and preferably more than 50%, in particular based on the width of the coupling tracks 9 and 25.

From the described structure of the coupler or power divider results that the four connection lines 13a, 13b and 17a, 17b are formed in coplanar technology. Likewise, it follows from the description of the embodiments of the invention that the two coupling paths 9 and 25 are formed in suspended substrate technology.

Claims (15)

1. HF-coupler or HF-power splitter, with the following features:

   - a substrate (3),

   - provided on the substrate (3) are two first connection lines (13a, 13b), which lead to a beginning (11a) and an end (11b) of a first coupling zone (9),

   - a second coupling zone (25) is provided, coupled to the first coupling zone (9), to the beginning (27a) and end (27b) of which two further connection lines (17a, 17b) lead,

   - the four connection lines (13a, 13b; 17a, 17b) lead from the individual coupling zone in each case to connections (15a, 15b; 19a, 19b) located offset to one another,

   - the four connection lines (13a, 13b; 17a, 17b) are arranged on the same side (3a) of the substrate (3),

   - the two coupling zones (9; 25) are formed on the substrate on two opposing sides (3a, 3b),

   - the two connection lines (13a, 13b) are electrically-galvanically connected to the first coupling zone (9) and are arranged on the same side (3a) of the substrate (3) as the first coupling zone (9),

   - the second coupling zone (25) is electrically-galvanically connected at its beginning and end (27a, 27b) in each case by means of at least one electroplated via hole (21) to the further connection lines (17a, 17b) belonging to it, which lie on the side (3a) of the substrate (3) opposite the second coupling zone (25),

   characterised by the following further features:

   - below the coupling area of the second coupling zone (25), an indentation is provided in a housing wall (29) and

   - in the longitudinal direction of the two coupling zones (9, 25), inter-digital capacitors (C) are provided which in each case are coupled between a coupling zone and earth.
2. Coupler or power splitter, in particular an HF-coupler or HF-power splitter or coupler according to Claim 1, characterised in that, at least with regard to one coupling zone (9, 25), at least one further inter-digital capacitor (C-9e, C-9f; C-25e, C-25f) is provided in each case between the beginning and end areas (11a, 11b; 18a, 18b) respectively.
3. Coupler or power splitter according to Claim 2, characterised in that further capacitors (C-9e, C-9f; C-25e, C-25f) are arranged in the middle area of the individual coupling zone (9, 25).
4. Coupler or power splitter according to any one of Claims 1 to 3, characterised in that the one coupling zone (9) with the connection lines (13a, 13b) belonging to it is arranged in plan view in such a way that the connection lines (13a, 13b), related to the coupling zone (9), lead to the same substrate edge (3') and preferably in plan view form at least approximately a U-shaped conductor path.
5. Coupler or power splitter according to any one of Claims 1 to 4, characterised in that also the connection line (17a, 17b) connected electrically-galvanically by the electroplated via hole (21) to the second coupling zone (25) is arranged in plan view in such a way that the connection lines (17a, 17b) related to the coupling zone (25) lead to the same substrate edge (3") and preferably in plan view form approximately a U-shaped conductor path.
6. Coupler or power splitter according to Claim 4 or 5, characterised in that the connection line (13a, 13b) connected to the one coupling zone (9) leads to the one substrate edge (3'), while by contrast the connection line (17a, 17b) connected electrically-galvanically to the second coupling zone (25) leads to the opposite substrate edge (3").
7. Coupler or power splitter according to any one of Claims 1 to 3, characterised in that the one coupling zone (9) with the connection lines (13a, 13b) belonging to it is arranged in such a way in plan view that the one connection line (13a), related to the coupling zone (9) leads with at least one component in a direction away from the coupling zone (9), preferably to a substrate edge (3'), while by contrast the second connection line (13b) with a component pointing in an opposite direction leads away from the coupling zone (9), preferably to the opposite substrate edge (3").
8. Coupler or power splitter according to Claim 6 or 7, characterised in that the two connection lines (13a, 13b) connected to the coupling zone (9) at the beginning (11a) and the end (11b) with the opposed component lead preferably in the opposed direction from the coupling zone (9), so that, preferably, in the plan view a conductor path is formed which is at least approximately Z-shaped.
9. Coupler or power splitter according to any one of Claims 6 to 8, characterised in that also the connection lines (17a, 17b), electrically-galvanically connected to the opposite coupling zone (25) by the electroplated via hole (21) lead away at the beginning (27a) and at the end (27b) of this coupling zone (25), with opposed components and preferably in the opposed direction from the coupling zone (25), so that, preferably, in plan view a conductor path is formed which is at least approximately Z-shaped.
10. Coupler or power splitter according to any one of Claims 1 to 9, characterised in that, in the area of the coupling zone (9, 25) and/or in the area of the connection lines (13a, 13b; 17a, 17b), the earthing surfaces (5, 31) formed on the upperside or underside of the substrate (3) have cut-outs (7), in which the connection lines (13a, 13b; 17a, 17b) and the coupling zones (9, 25) are arranged.
11. Coupler or power splitter according to Claim 10, characterised in that the distance interval between the coupling zones (9, 25) and/or the connection lines (13a, 13b; 17a, 17b) and the earthing surfaces (5, 31) corresponds to between 1.5 to 4 times the width of the coupling zone (9, 25) and the width of the connection lines (13a, 13b; 17a, 17b).
12. Coupler or power splitter according to any one of Claims 1 to 11, characterised in that the coupling zones (9, 25) in plan view perpendicular to the surface of the substrate (3) overlap and the overlap area related to the width of the two coupling zones (9, 25) amounts to at least 10%, preferably more than 40%, or, in particular, more than 70%.
13. Coupler or power splitter according to any one of Claims 1 to 12, characterised in that the four connection lines (13a, 13b; 17a, 17b) are designed in coplanar technology.
14. Coupler or power splitter according to any one of Claims 1 to 13, characterised in that the two coupling zones (9; 25) are designed in suspended-substrate technology.
15. Coupler or power splitter according to any one of Claims 1 to 14, characterised in that the distance interval (37) or the indentation (37) beneath the coupling area of the second coupling zone (25) is formed in a housing (29).

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