JP3158031B2 - Microstrip line coupling structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a coupling structure between microstrip lines in a high-frequency circuit board.

[0002]

2. Description of the Related Art Conventionally, a microstrip line has been known as a line for transmitting a signal in a high-frequency circuit board. In addition, a technique for connecting the microstrip lines is important in designing a circuit board.

A conventional method for connecting microstrip lines will be described with reference to FIGS. 5 and 6, a ground layer (also referred to as a ground conductor layer or a ground layer) 21 made of a conductor layer and a first strip conductor path formed on one surface of the ground layer 21 via a dielectric layer 22. 23, a first microstrip line 24 is formed. On the other hand, on a surface opposite to the ground layer 21, a second strip conductor path 26 formed through a dielectric layer 25 formed on the other surface of the ground layer 21 is formed.
A second microstrip line 27 is formed.

Then, the first microstrip line 2
As a method for connecting the second microstrip line 27 to the second microstrip line 27, according to FIG. 5, a hole 28 is formed in the ground layer 21. The strip conductor 23 and the second strip conductor 26 are electrically connected.

On the other hand, as another connection method, according to FIG. 6, both the first strip conductor path 23 and the second strip conductor path 26 have open end portions 30, 31 and are grounded. Slots in layer 21
The first strip conductor path 23 and the second strip conductor path 26 are arranged so as to overlap with each other in a plane with a length of 波長 wavelength of the signal wavelength so as to sandwich the slot 32. Are connected by electromagnetic coupling through the slot 32. At this time, slot 32 is 1
It has a length of 1/2 wavelength and is formed to be perpendicular to the conductor paths 23 and 26 on a plane.

[0006]

However, according to the method shown in FIG. 5, although the DC current is transmitted without loss, the frequency of the signal is increased as is clear from the frequency characteristic diagram of the transmission coefficient shown in FIG. Accordingly, there is a problem that the loss increases remarkably.

In addition, the method using electromagnetic coupling as shown in FIG. 6 has a problem that the loss is small in a high frequency region, but is significantly large in a low frequency region, as is apparent from FIG.

[0008]

The inventor of the present invention has studied the above problems, and as a result, the microstrip lines have been electromagnetically coupled with each other, and at the same time, the conductors have been connected between the strip conductor paths at specific locations. The present invention has been made based on the finding that good characteristics without loss can be obtained from the low frequency to the high frequency region by the connection.

That is, the coupling structure of the microstrip line according to the present invention includes a ground layer formed of a conductor layer and a first layer formed on one surface of the ground layer via the first dielectric layer.
And a second conductor on the other surface of the ground layer.
A second strip conductor path formed with a dielectric layer interposed therebetween, and the first and second strip conductor paths are arranged so as to overlap with each other by a half of a signal wavelength in a plan view. A first hole formed of a long hole having a length equal to a half wavelength of the signal wavelength is formed in a center portion of the overlapping portion of the conductor paths in the ground layer, and a first strip conductor path is formed. And a second strip conductor path is electrically connected by a conductor wire passing through the first dielectric layer, the first hole, and the second dielectric layer.

Another connection structure of the present invention includes a ground layer made of a conductor layer, a first strip conductor path formed on one surface of the ground layer via a first dielectric layer, A second strip conductor path formed on the other surface of the ground layer via a second dielectric layer, wherein the first and second strip conductor paths have a signal wavelength of 1 And a first hole made of a long hole having a half wavelength of the signal wavelength is formed at the center of the overlapping portion of the conductor path in the ground layer. Forming a second hole in a portion located at an end of the first strip conductor path, and connecting the end of the first strip conductor and the second strip conductor to the first dielectric layer; Electrically through the conductor hole passing through the second hole and through the second dielectric layer. Characterized in that the connection was.

[0011]

According to the coupling structure of the present invention, a low-frequency signal can be transmitted like a direct current through a conductor line connected between signal conductor paths. A high-frequency signal can be transmitted by electromagnetic coupling between the microstrip line and the slot in the ground layer. At this time, according to the structure of the present invention, when the conductor line drawn from the tip of the signal conductor path is placed so as not to adversely affect the transmission of the high frequency signal, the signal is transmitted in both the low frequency and high frequency regions. Can be transmitted.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The coupling structure of the present invention is shown in FIGS.
It is explained based on.

FIG. 1 is a schematic layout diagram of the coupling structure of the present invention. According to FIG. 1, a ground layer 1 made of a conductor layer is formed on the entire surface, and a first strip conductor path 3 is formed on one surface of the ground layer 1 via a first dielectric layer 2,
These form a first microstrip line 4. In this microstrip line, the electromagnetic coupling between the ground layer 1 and the strip conductor path 3 causes
A signal is transmitted.

On the other hand, the second surface of the ground layer 1
A second strip conductor path 6 is formed with the dielectric layer 5 interposed therebetween, thereby forming a second microstrip line 7.

Then, the first microstrip line 4
According to FIG. 1, the first strip conductor path 3 and the second strip conductor path 6 both have open ends 8 and 9 as a coupling structure between the first strip conductor path 3 and the second microstrip line 7. These are arranged so as to overlap in plan view. This overlap is arranged so as to overlap by a half wavelength of the transmission signal.

The ground layer 1 has a first hole 10 formed of a long hole (slot) having a long end. The first hole 10 is provided in the first strip conductor path 3.
And the second strip conductor 6 is formed at an intermediate position in the overlapping portion. Therefore, when the first strip conductor 3 and the second strip conductor 6 are arranged so as to overlap each other by a half wavelength of the transmission signal, the first strip conductor 3 and the second strip conductor The length of the strip conductor path 6 to the open ends 8 and 9 is 1 of the signal wavelength.
/ 4 wavelength. Further, the width of the elongated hole is substantially the same as the width of the strip conductor paths 3 and 6, and the length is desirably set to a half wavelength of the signal wavelength.

The first strip conductor path 3 and the second strip conductor path 6 are formed of a conductor wire penetrating through the first dielectric layer 2, the inside of the hole 10, and the second dielectric layer 5. 11
Connected by The conductor wire 11 is not electrically connected to the ground layer 1.

According to the structure of FIG. 1, for example, when the signal input from the strip conductor path 3 has a low frequency,
Via the conductor wire 11 connected between the strip conductors 3, 6, it is transmitted like a direct current and transmitted to the strip conductor 6. In the case of a high-frequency signal, a signal is transmitted to the strip conductor path 6 by electromagnetic coupling between the strip conductor paths 3 and 6 sandwiching the hole 10.

Next, FIG. 2 is a schematic view of another coupling structure of the present invention. According to FIG. 2, the first hole 10 and the second hole 12 are formed in the ground layer 1 as described with reference to FIG. 1. The end 7 of the strip conductor path 3
And the strip conductor path 6 comprises: a first dielectric layer 2;
Conductor wire 1 penetrating through hole 12 and second dielectric layer 5
1 connected. The shape of the hole 12 may be any shape as long as the conductor wire 11 is at a level that is not electrically connected to the ground layer 1.

According to the structure of FIG. 2, for example, when the signal input from the strip conductor 3 is of a low frequency, the strip conductor is connected via the conductor wire 11 connected between the strip conductors 3 and 6. 6 is transmitted. In the case of a high-frequency signal, a signal is transmitted to the strip conductor path 6 by electromagnetic coupling between the strip conductor paths 3 and 6 sandwiching the hole 10.

In the coupling structure shown in FIGS. 1 and 2 described above, the shape of the first hole 10 is not limited to the above-described shape. There is no problem even if the shape is other than the above range.

In the above coupling structure, the dielectric layer is not particularly limited, but is formed of a known material such as an alumina-based, aluminum nitride-based, or glass-ceramic-based sintered body.

Further, the strip conductor path and the ground layer
Both are formed by a known multilayer technology, for example, by forming by metallizing a dielectric layer,
Alternatively, it can also be formed by applying a metallized paste to the molded body of the dielectric layer and firing it simultaneously. The conductor layer can be formed of a conductor such as W, Mo, Ag, Cu, or Au. However, from the viewpoint of signal transmission characteristics up to a high-frequency region, Cu, Ag, Au, or the like having excellent electric conductivity is preferably used. used.

The conductor wire 11 can be formed by forming a through hole by the same metallization method as the above-mentioned conductor layer and filling the metallization, or can be formed by burying a metal wire.

Next, the transmission characteristics of the above coupling structure were examined. Using a glass ceramic substrate having a dielectric constant of 3.67 as a dielectric layer, circuits as shown in FIGS. 1 and 2 were formed by Cu metallization. The strip conductor has a line width of 1.85 mm and a first hole (slot).
The long side is 7.83 mm, the short side is 1.55 mm, and the overlapping length of the strip conductor paths 3 and 6 is 7.92 mm.
The slot was formed at an intermediate position between the overlapping portions. In addition,
The conductor wire diameter was 0.6 mm.

A signal is input to each substrate from the strip conductor path 3, the strength of the signal output from the strip conductor path 6 is measured, and the ratio of the output signal strength to the input signal strength (transmission coefficient); The relationship with the signal frequency up to 28 GHz was examined. The results are shown in FIG. 3 and FIG.
The circuits of FIGS. 7 and 8, which are conventional examples, were formed, and the transmission characteristics were similarly evaluated.

According to the results shown in FIGS. 7 and 8, in the conventional example, the loss is increased at either the low frequency or the high frequency. On the other hand, in FIGS. The transmission loss was small from high to high frequencies. In particular, FIG. 4 shows good transmission characteristics with small transmission loss.

[0028]

As described in detail above, according to the coupling structure of the microstrip line of the present invention, coupling with low transmission loss from low frequency to high frequency is possible. Thereby, the reliability of the circuit and the degree of freedom in circuit design can be increased.

[Brief description of the drawings]

FIG. 1 is a schematic layout view showing one embodiment of a coupling structure of a microstrip line according to the present invention, wherein (a) is a plan view,
(B) is a sectional view.

FIG. 2 is a schematic layout view showing another embodiment of the coupling structure of the microstrip line according to the present invention, wherein (a) is a plan view,
(B) is a sectional view.

FIG. 3 is a diagram illustrating a relationship between a transmission coefficient and a transmission frequency in the coupling structure of the microstrip line in FIG. 1;

FIG. 4 is a diagram illustrating a relationship between a transmission coefficient and a transmission frequency in the coupling structure of the microstrip line in FIG. 2;

5A and 5B are schematic layout diagrams of a conventional coupling structure of a microstrip line, where FIG. 5A is a plan view and FIG. 5B is a cross-sectional view.

6A and 6B are schematic layout views of another coupling structure of a conventional microstrip line, where FIG. 6A is a plan view and FIG. 6B is a cross-sectional view.

FIG. 7 is a diagram showing a relationship between a transmission coefficient and a transmission frequency in the coupling structure of the microstrip line of FIG. 5;

8 is a diagram illustrating a relationship between a transmission coefficient and a transmission frequency in the coupling structure of the microstrip line in FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ground layer 2 1st dielectric layer 3 1st strip conductor path 4 1st microstrip line 5 2nd dielectric layer 6 2nd strip conductor path 7 2nd microstrip line 8, 9 Open end DESCRIPTION OF SYMBOLS 10 1st hole 11 Conductor wire 12 2nd hole

Claims (2)

(57) [Claims] A ground layer formed of a conductor layer; and a first layer formed on one surface of the ground layer via a first dielectric layer.
And a second conductor on the other surface of the ground layer.
Dielectric layer and a second strip conductor paths formed through the front Symbol first and second strip conductor so as to overlap one half of the length of the signal wavelength as seen in a plan view A first hole formed of a long hole having a length equal to a half wavelength of a signal wavelength is formed in a center portion of an overlapping portion of the conductor path in the ground layer, and a first strip conductor is formed. A microstrip line, wherein the path and the second strip conductor path are electrically connected by a conductor line passing through the first dielectric layer, the first hole and through the second dielectric layer. Connection structure. 2. A ground layer comprising a conductor layer, and a first layer formed on one surface of the ground layer via a first dielectric layer.
And a second conductor on the other surface of the ground layer.
A second strip conductor path formed with a dielectric layer interposed therebetween, and the first and second strip conductor paths are arranged so as to overlap with each other by a half of a signal wavelength in a plan view. And forming a first hole formed of a long hole having a length of １ ／ wavelength of the signal wavelength at a center portion of the overlapping portion of the conductor paths in the ground layer, and forming an end of the first strip conductor path. Forming a second hole in the portion located in the portion,
The fact that the end portion of the first strip conductor and the second strip conductor are electrically connected by a conductor wire passing through the first dielectric layer, the second hole, and the second dielectric layer. Characteristic coupling structure of microstrip line.