EP3734751B1

EP3734751B1 - Strip line directional coupler and coupling degree adjustment method thereof

Info

Publication number: EP3734751B1
Application number: EP18896853.1A
Authority: EP
Inventors: Xuanliang CEN; Hongliang Chen; Zhanjun LAI
Original assignee: Comba Telecom Technology Guangzhou Ltd
Current assignee: Comba Telecom Technology Guangzhou Ltd
Priority date: 2017-12-29
Filing date: 2018-07-27
Publication date: 2022-10-26
Anticipated expiration: 2038-07-27
Also published as: CA3097049A1; CN108023154A; EP3734751A4; WO2019128215A1; EP3734751A1; CA3097049C; CN108023154B

Description

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a national stage of International Disclosure No. PCT/CN2018/097592 filed on July 27, 2018 .

TECHNICAL FIELD

The present disclosure relates to the field of mobile communication technology, and more particularly, to a strip line directional coupler and a method for adjusting a coupling degree thereof.

BACKGROUND

Directional couplers are widely used in the fields of radio frequency and microwave. At present, the well-known strip line directional coupler is composed of a pair of strip-line lines with parallel coupling lines, a medium, and two upper and lower ground layers. Lines of the pair of parallel coupling lines are close to each other to generate coupling. The coupling degree is determined by the distance between the coupling lines, the relative dielectric constant of the medium, and the structure and size of the ground layer. In the specific implementations, forms of multi-layer printed circuit boards, air strip lines, and the like are usually used. However, the processing accuracy is limited, and situations of the coupling degree deviating from the reference range or poor indexes are existed in the existing strip line couplers, which reduce the performance of the device.
WO 2010/041789 A1 discloses a multi-layer directional coupler for adjusting the amount of coupling from outside without disassembly. At least one hole in which a tuning element is inserted is formed in the third dielectric layer of the directional coupler, and an entry depth of the tuning element in the hole is changed.
JP 2014 165823 A discloses a directional coupler in which a passing phase in the even mode operation and a passing phase in the odd mode operation can be matched, such that a directivity can be improved.
US 2014/292440 A1 discloses a directional coupler including a first hollow portion that is disposed in a first ground conductor and is arranged directly above a first signal conductor, and that is constructed of a discontinuous structure that has a function of delaying the phase and that is small with respect to the one-quarter wave-length of an operating frequency.
However, the processing accuracy is limited, and situations of the coupling degree deviating from the reference range or poor indexes are existed in the existing strip line couplers, which reduce the performance of the device.

SUMMARY

In view of the above problem, the present disclosure provides a strip line directional coupler, in which openings are defined in an adjustment zone of the ground layer. By changing the shape, area and quantity of the openings, current distribution of the strip line can be changed, the coupling degree can be adjusted, which makes the coupling degree adjustment simple and effective.
Correspondingly, a method for adjusting a coupling degree is provided. By welding or etching the openings, and changing the shape and area of the openings, the current distribution of the strip line is changed, the coupling degree is adjusted, and simple and effective coupling degree adjustment can be realized.
The present disclosure provides a strip line directional coupler as defined in claim 1. Further aspects and preferred embodiments are defined in the dependent claims. Any aspects, embodiments and examples of the present disclosure which do not fall under the scope of the appended claims do not form part of the invention and are merely provided for illustrative purposes." Preferably, a plurality of the openings arranged at intervals are defined in the adjustment zone.
Further, the plurality of the openings are arranged in sequence in an extending direction of the coupling sections.
Preferably, the opening is a round hole, a square hole, an annular hole, a triangular hole, or an irregular hole.
Preferably, the first ground layer and the second ground layer are electrically connected to each other.
The opening includes an annular gap and/or a strip-shaped gap group. The annular gap has a shape of a rectangle, and a pair of opposite edges of the rectangle are set as weldable zones. The strip-shaped gap group includes two strip-shaped gaps arranged in parallel. The ground layer between the end points of the two strip-shaped gaps constitutes a removable zone.
Further, a surface of each of the first ground layer and the second ground layer is coated with a solder mask layer, and the solder mask layer is defined in the adjustment zone and is provided with opening windows.
Further, the strip line directional coupler further comprises: a first dielectric layer and a second dielectric layer disposed between every adjacent two of the first ground layer, the strip line layer, and the second ground layer, and a bonding material layer disposed between the first dielectric layer and the second dielectric layer for bonding the first dielectric layer and the second dielectric layer.
Correspondingly, the present disclosure further provides a method for adjusting a coupling degree based on the strip line directional coupler of any one of the above examples, and the method for adjusting a coupling degree being defined in the independent method claim.
Compared with the prior art, in the strip line directional coupler of the present disclosure, the first grounding layer facing the coupling sections is dug out processed to provide an adjustment zone with an opening having at least one shape; the coupling degree is adjusted by changing the shape, area, and quantity of the openings, thus the method for adjusting the coupling degree adjustment is simple and effective.
Preferably, the opening is classified into annular gaps and strip-shaped gap groups alternately arranged along the extension direction of the coupling sections; the transformation between the two types of openings is achieved by welding, which also makes the method for adjusting the coupling degree simple and effective.
The annular gap is configured to have a shape of rectangle, and a pair of opposite edges of the rectangle are respectively set as weldable zones. The strip-shaped gap group includes two strip-shaped gaps arranged in parallel, and each of the connecting lines between the end points of the two strip-shaped gaps constitutes a removable zone respectively. The weldable zone and the removable zone have regular shapes, which is convenient for welding or removing the metal layer to adjust the coupling degree, and has a beautiful appearance before and after the adjustment.
The surfaces of the first ground layer and the second ground layer each are further coated with a solder mask layer, and opening windows are defined in the removable zone and the weldable zone, which not only can effectively protect the metal layer in the non-adjustment zone from being damaged, but also can make the operation position of the cutting and welding process more accurate and easy to control.
For the adjustment zone on the ground layer of the strip line directional coupler of the present disclosure, a method for adjusting the coupling degree is provided. The method for adjusting the coupling degree is simple and effective by using two simple processes (welding and etching) to adjust the coupling degree, and the pass rate of the coupling degree index is increased. The method for adjusting the coupling degree can meet the more stringent coupling degree index under the same processing accuracy, and is especially suitable for application scenarios that use a plurality of couplers at the same time and require high consistency of the coupling degree.
These and other aspects of the present disclosure will be more apparent and easily understood in the descriptions of the embodiments below.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to illustrate the technical solutions of the embodiments of the present disclosure more clearly, the accompanying drawings used in the description of the embodiments are briefly described below. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and a person skilled in the art can obtain other drawings according to these accompanying drawings without creative effort.

FIG. 1 is an exploded view of a strip line directional coupler according to the present invention.
FIG. 2 is a cross-sectional view of a strip line directional coupler according to the present invention.
FIG. 3 is a schematic structure diagram of a first ground layer of a strip line directional coupler according to the present invention.
FIG. 4 is a schematic structure diagram of a first ground layer after the annular gaps are transformed into strip-shaped gaps according to an embodiment of the present disclosure.
FIG. 5 is a schematic structure diagram of a first ground layer after the strip-shaped gaps are transformed into annular gaps according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

In order to enable those skilled in the art to better understand the solutions of the present disclosure, the technical solutions in the embodiments of the present disclosure are clearly and completely described below with references to drawings in the embodiments of the present disclosure. Obviously, the embodiments described are only a part of the embodiments of the present disclosure, and not all of the embodiments.
Referring to FIG. 1, a strip line directional coupler 100 is provided according to the present invention, which includes a first ground layer 1, a first dielectric layer 2, a strip line layer 3, a bonding material layer 4, a second dielectric layer 5, and a second ground layer 6 stacked successively.
In combination with FIG. 2, the first dielectric layer 2 and the second dielectric layer 5 are stacked with each other and are bonded to each other through the bonding material, so as to form a multilayer circuit board.
The strip line layer 3 is disposed on a side of the first dielectric layer 2 close to the second dielectric layer 5. The strip line layer 3 includes a first line 31 and a second line 32 that are coupled to each other. The two lines are provided with coupling sections 30 extending parallel to each other, so that when a signal is input from one line and output at its through end, part of the signal can be simultaneously coupled to the other line and output by the other line.
The first ground layer 1 and the second ground layer 6 are both copper coating layers. They are disposed on the first dielectric layer 2 and the second dielectric layer 5, respectively, and are located on sides of the two dielectric layers away from each other, respectively. Preferably, the projections of the first grounding layer 1 and the second grounding layer 6 onto the strip line layer 3 each cover the strip line layer 3, and the first grounding layer 1 and the second grounding layer 6 are configured to play adjusting and shielding roles to the signal of the strip line layer 3. Preferably, the first ground layer 1 and the second ground layer 6 are electrically connected to each other.
An adjustment zone 10 for adjusting the coupling degree of the strip line directional coupler is provided at a position of the first ground layer 1 facing or close to the coupling sections 30. A plurality of openings are defined in the adjustment zone 10 by etching the metal layer of the first ground layer 1 (processing of digging the copper). Preferably, a plurality of the openings arranged at intervals are defined in the adjustment zone 10, and the plurality of openings are arranged in sequence in the extending direction of the coupling sections 30.
In other embodiments, an adjustment zone for adjusting the coupling degree of the strip line directional coupler may be further provided at a position of the second ground layer 6 facing or close to the coupling sections 30. A plurality of openings are defined in the adjustment zone 10 by etching the metal layer of the second ground layer 6 (processing of digging the copper).
Preferably, the opening is classified into an annular gap 11 and a strip gap 12. The annular gap 11 is provided with two weldable zones 110. The quantity of the strip-shaped gaps 12 is an even number, two adjacent strip-shaped gaps 12 form a strip-shaped gap group, and each of the strip-shaped gaps groups is provided with two removable zones 120.
Referring to FIG. 3, in the present invention, the annular gap 11 is configured into a shape of a rectangle, and the two weldable zones 110 are two opposite edges of the rectangle, respectively. The strip-shaped gap group has a shape of two strip-shaped gaps 12 arranged in parallel, and the two removable zones 120 are the lines connecting the end points of the two strip-shaped gaps 12.
In other embodiments, there may be a plurality of annular gaps 11 and a plurality of strip-shaped gap groups, and they are arranged alternately in the extending direction of the coupling sections 30, respectively.
As an embodiment, a solder mask layer (not shown) is further coated on a surface of each of the first ground layer 1 and the second ground layer 6, and the solder mask layer is a liquid photoimagable solder mask (green oil). The solder mask layer locates at the adjustment zone 10 and is provided with opening windows (not shown). Preferably, the opening windows are defined at the removable zone 120 and the weldable zone 110, which can make the operation position of the cutting and welding process more accurate.
Correspondingly, the present disclosure provides a method for adjusting a coupling degree based on the strip line directional coupler 100, which includes the following steps:

testing a coupling degree of the directional coupler to obtain a test value;
comparing the test value with a predetermined reference range of coupling degree; and
when the test value is not within the reference range, adjusting the coupling degree to make the test value within the reference range by changing at least one of shapes, quantity, and area sizes of the openings.

Specifically, when the test value is higher than the reference range, the coupling degree is reduced by covering a first ground layer on a corresponding opening through a first post-treatment process; when the test value is lower than the reference range, the coupling degree is increased by removing a corresponding first ground layer through a second post-treatment process to form a new opening.
The first post-treatment process is a welding process, and the second post-treatment process is an etching process.
Referring to FIG. 3 to FIG. 5, preferably, when the gap is classified into an annular gap 11 and a strip-shaped gap group, the method includes: if the test value is higher than the reference range, transforming the annular gap 11 into a strip-shaped gap 12' to reduce the coupling degree; if the test value is lower than the reference range, transforming the strip-shaped gap group into an annular gap 11' to increase the coupling degree.
Referring to FIGS. 3 and 4, where FIG. 4 is a schematic diagram of the first ground layer 1' and the adjustment zone 10' after the annular gap 11 is transformed into a strip-shaped gap 12'. The specific adjustment method is: welding the metal layer in the weldable zone 110 to short-circuit the metal layer in the weldable zone 110. Preferably, the welding method may include: applying molten solder in the welding zone 110 through an electric soldering iron, short-circuiting the two edges of the annular gap 11 with the metal layer of the adjustment zone 10' through the solder, and further transforming the annular gap 11 into a strip-shaped gap 12'. By changing the shape of the gap, the local current distribution is changed, and the coupling degree is thus changed.
Referring to FIGS. 3 and 5, where FIG. 5 is a schematic diagram of the first ground layer 1" and the adjustment zone 10" after the strip-shaped gap group is transformed into an annular gap 11'. The specific adjustment method is: etching or cutting the metal layer in the removable zone 120 to disconnect the metal layer in the removable zone 120. Preferably, the cutting method may include: digging out the metal layer in the removable zone 120 through a knife, so that the metal layer connecting the end points of the two strip-shaped gaps 12 in the strip-shaped gap group is disconnected, and the strip-shaped gap group is further transformed into an annular gap 11'. By changing the shape of the gap, the local current distribution is changed, and therefore the coupling degree is changed.
It should be noted that, the ranges and positions of the weldable zone 110 and the removable zone 120 as shown in figure according to the embodiment are preferred implementations conducive to operation. However, the illustrated figures are not intended to limit the precise ranges of the two. That is, their ranges can be appropriately enlarged or reduced based on the frame selections, and their positions can also be appropriately moved based on the frame selections.
The etching process may include, but is not limited to, processes such as physical engraving, cutting, laser engraving, chemical etching, electrochemical etching, or the like.
In other embodiments, the opening may also be a round hole, a square hole, an annular hole, a triangular hole, a special-shaped hole, an "H" shaped hole, a square hole with a cross shape inside, or other shaped holes, or any combination thereof. An opening is within the scope of the present application as long as it is defined in the adjustment zone of the ground layer and the current distribution of the strip line can be changed by operating the opening to change its shape and area.
Compared with the prior art, the strip line directional coupler and the method for adjusting the coupling degree thereof according to the present disclosure have the following advantages:

(1) The first ground layer facing the coupling sections is processed by digging out to provide an adjustment zone with openings having various shapes such that the coupling degree is adjusted by changing the shape and area of the opening, which makes the adjusting of the coupling degree simple and effective.
(2) The opening is classified into annular gaps and strip-shaped gap groups alternately arranged in the extension direction of the coupling sections in which the transformation between the two types of gaps can be made by welding and etching, which also makes the adjusting of the coupling degree simple and effective.
(3) The annular gap has a shape of a rectangle, and a pair of opposite edges of the rectangle are respectively set as weldable zones. The strip-shaped gap group includes two strip-shaped gaps arranged in parallel, and each of the connecting lines between the end points of the two strip-shaped gaps forms a removable zone respectively. The weldable zone and the removable zone have regular shapes, which is convenient for welding or removing the metal layer to adjust the coupling degree, and has an aesthetic appearance before and after the adjustment.
(4) The surfaces of the first ground layer and the second ground layer each are further coated with a solder mask layer, and opening windows are defined in the removable zone and the weldable zone, which not only can effectively protect the metal layer in the non-adjustment zone from being damaged, but also can make the operation position of the cutting and welding process more accurate and easy to control.
(5) For the adjustment zone on the ground layer of the strip line directional coupler of the present disclosure, a method for adjusting the coupling degree is provided. Two simple processes (welding and etching) are used to adjust the coupling degree. The method for adjusting of the coupling degree is simple and effective, and the pass rate of the coupling degree index is increased, which can meet the more strict coupling degree index under the same processing accuracy, and is especially suitable for application scenarios that use a plurality of couplers at the same time and that require high consistency of the coupling degree.

Some embodiments provided by the present disclosure are described in detail above, for those of ordinary skill in the art, according to the concept of the embodiments of the present disclosure.

Claims

A strip line directional coupler (100), comprising:
a first ground layer (1), a strip line layer (3), and a second ground layer (6) stacked successively;

wherein the strip line layer (3) has a first line (31) and a second line (32), and the first line (31) and the second line (32) are provided with coupling sections (30) close to each other; and

wherein the first ground layer (1) and/or the second ground layer (6) is provided with an adjustment zone (10) at a position facing or close to the coupling sections (30), and an opening for adjusting a coupling degree is defined on the first ground layer (1) and/or the second ground layer (6) in the adjustment zone (10);

wherein the opening comprises an annular gap (11) and/or a strip-shaped gap group; characterized in that

the annular gap (11) has a shape of a rectangle, and a pair of opposite edges of the rectangle are set as weldable zones (110); and

the strip-shaped gap group (12) comprises two strip-shaped gaps (12) arranged in parallel, and connecting lines between end points of the two strip-shaped gaps constitute removable zones (120).
The strip line directional coupler (100) according to claim 1, wherein, a plurality of the openings arranged at intervals are defined in the adjustment zone (10).
The strip line directional coupler (100) according to claim 2, wherein, the plurality of the openings are arranged in sequence in an extending direction of the coupling sections (30).
The strip line directional coupler (100) according to claim 1, wherein, the opening is a round hole, a square hole, an annular hole, a triangular hole, or an irregular hole.
The strip line directional coupler (100) according to claim 1, wherein, the first ground layer (1) and the second ground layer (6) are electrically connected to each other.
The strip line directional coupler (100) according to claim 1, wherein, a surface of each of the first ground layer (1) and the second ground layer (6) is coated with a solder mask layer, and the solder mask layer is in the adjustment zone (10) and provided with opening windows, and the opening windows are defined at the removable zone (120) and the weldable zone (110).
The strip line directional coupler (100) according to any one of claims 1 to 6, wherein the strip line directional coupler (100) further comprises: a first dielectric layer (2) and a second dielectric layer (5) disposed between every adjacent two of the first ground layer (1), the strip line layer (3), and the second ground layer (6), and a bonding material layer disposed between the first dielectric layer (2) and the second dielectric layer (6) for bonding the first dielectric layer (2) and the second dielectric layer(6).
A method for adjusting a coupling degree, based on the strip line directional coupler according to any one of claims 1 to 7,
wherein the method for adjusting the coupling degree comprises following steps:

testing a coupling degree of the directional coupler to obtain a test value;

comparing the test value with a predetermined reference range of the coupling degree; and

when the test value is not within the reference range, adjusting the coupling degree to make the test value within the reference range by changing at least one of a shape, a quantity, and an area size of the openings;

wherein, when the test value is higher than the reference range, the coupling degree is reduced by covering a first ground layer on a corresponding opening through a first post-treatment process; and when the test value is lower than the reference range, the coupling degree is increased by removing a corresponding first ground layer through a second post-treatment process to form a new opening;

wherein the first post-treatment process is a welding process, and the second post-treatment process is an etching process.
The method for adjusting a coupling degree according to claim 8, wherein, the openings are classified into an annular gap (11) and a strip-shaped gap group;
the annular gap (11) is configured to have a shape of rectangle, and a pair of opposite edges of the rectangle are respectively set as weldable zones (110);

the strip-shaped gap group comprises two strip-shaped gaps (12) arranged in parallel, and each of connecting lines between end points of the two strip-shaped gaps (12) constitutes a removable zone (120) respectively.
The method for adjusting a coupling degree according to claim 9, wherein the method comprises: if the test value is higher than the reference range, transforming the annular gap (11) into a strip-shaped gap group to reduce the coupling degree; if the test value is lower than the reference range, transforming the strip-shaped gap group into an annular gap (11) to increase the coupling degree.
The method for adjusting a coupling degree according to claim 10, wherein the transforming the annular gap (11) into a strip-shaped gap comprises: welding a metal layer in the weldable zone (110) to short-circuit the metal layer in the weldable zone (110); and
wherein the transforming the strip-shaped gap group into an annular gap (11) comprises: etching or cutting a metal layer in the removable zone (120) to disconnect the metal layer in the removable zone (120).