JPH06283907A - Microstrip line - Google Patents

Abstract

PURPOSE:To reduce the transmission loss and to improve the transmission efficiency of a microstrip line by concentrating the current density distribution of the microstrip line at a high part of high conductivity. CONSTITUTION:An alumina ceramic substrate 1 contains a ground layer on one of both sides, and a strip line 6 is formed on the other side of the substrate 1 by laminating an electroless plating layer 5 on an Ag thick film conductor layer 4. In such a constitution of a microstrip line, the high dielectric constant members 7 are placed on the substrate 1 and at the positions adjacent to both sides of the line 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microstrip line, and in particular, in a microstrip line composed of a ground layer and a strip line sandwiching a dielectric substrate, high dielectric members are arranged on both sides of the strip line. The present invention relates to a technique for reducing transmission loss.

[0002]

2. Description of the Related Art For example, a microstrip line is used as a microwave transmission line used in a microwave integrated circuit. A microstrip line forms a transmission line by forming a ground layer made of a flat conductor layer on one surface of a dielectric substrate such as alumina ceramic and forming a strip conductor line on the other surface. .
The characteristics of this microstrip line are equivalent to those of a coaxial cable developed in a plane, and the characteristic impedance is the width and thickness of the strip line, the dielectric constant of the dielectric substrate,
Determined by thickness.

When a microwave propagates in a conductor line,
Due to the skin effect, the current does not flow so much in the center of the conductor and is concentrated near the surface of the conductor. The higher the frequency is, the stronger the tendency becomes. When the frequency is in the GHz order, the depth of the skin becomes several microns, and almost the surface of the conductor line flows. In particular, the current density becomes high at the edge portion of the conductor line.

Conventionally, the strip line is formed on the dielectric substrate by A
A structure in which an electroless Cu plating layer is laminated on a thick film conductor formed of g paste or the like is used. According to this structure, since the structural defects on the surface of the thick film conductor having low conductivity can be compensated by the Cu plating layer and the conductivity of the strip line skin portion can be increased, when the current is concentrated on the conductor surface by the skin effect. Also, the transmission loss can be relatively reduced.

[0005]

However, a certain amount of current still flows in the portion of the Ag thick film conductor layer having many defects at the interface with the Cu plating layer, which causes a transmission loss, thereby increasing the transmission efficiency of the microstrip line. There was a limit to raising it.

Therefore, an object of the present invention is to further reduce the transmission loss of the microstrip line by further concentrating the current density distribution of the microwave on the Cu plating layer having few structural defects and high conductivity. .

[0007]

In order to solve the above problems, in the present invention, a strip-shaped conductor line is formed on the other surface of a dielectric substrate having a conductor layer as a ground layer on one surface. To form a microstrip line, and in which the skin portion of the conductor line has a relatively high conductivity, the microstrip line is adjacent to the conductor line and is in contact with the surface of the conductor line on the dielectric substrate. A dielectric member having a higher dielectric constant than the surrounding dielectric constant is arranged.

Further, the conductor line can be formed, for example, by laminating an electroless Cu plating layer on an Ag thick film conductor.

Further, it is advantageous that the dielectric constant of the dielectric member is higher than that of the dielectric substrate.

[0010]

With such a configuration, by disposing the dielectric member adjacent to both sides of the conductor line and having a higher dielectric constant than the surrounding dielectric constant of air or the like in contact with the conductor line,
The current density distribution of microwaves flowing through the conductor line is further concentrated on the dielectric adjacent portions on both sides of the line. Therefore, the proportion of the current flowing at the interface between the Ag thick film conductor having many structural defects and the Cu plating layer is reduced, and a large amount of current flows on the surface of the Cu plating layer having high conductivity, so that the transmission loss is reduced and the microwave The transmission efficiency of the transmission circuit is improved.

Further, by using a dielectric member having a dielectric constant larger than that of the dielectric substrate as the dielectric member arranged adjacent to the conductor line, the current density distribution is further reduced to the Cu plating layer. It is possible to concentrate, and the transmission loss can be significantly reduced.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a schematic structure of a microstrip line according to an embodiment of the present invention. In the structure shown in the figure, an electroless Cu plating layer 3 is laminated on one surface of an alumina ceramic substrate 1 on a thick film conductor layer 2 formed of Ag paste or the like as a ground layer. Further, a flat plate-like strip line 6 in which an electroless plating layer 5 is laminated on a thick film conductor layer 4 formed of Ag paste or the like is also formed on the other surface. High-dielectric members 7 having a small dielectric loss (tan δ) such as glass are arranged adjacent to and parallel to both sides of the strip line 6.

The high dielectric member 7 is formed, for example, after the Ag thick film conductor 4 is printed on the alumina ceramic substrate 1, and then the electroless plating layer 5 is formed on the Ag thick film conductor 4.

In the microstrip line having the above structure, when a microwave current flows through the strip line 6, most of the current is concentrated on the edge portion of the electroless Cu plating layer 5 due to the skin effect. Some are Ag
The thick film conductor layer 4 flows to the structural defect portion at the interface with the electroless Cu plating layer 5.

In the present invention, the electromagnetic field distribution is attracted to the high dielectric member 7 adjacent to the edge portion, and the current flowing in the defective portion of the Ag thick film conductor layer 4 in the prior art is more conductive than the defective portion. A large amount will flow into the high electroless Cu plating layer 5. Therefore, the transmission loss is further reduced.

FIG. 2 is a graph 8 showing the relationship between the cross section of the strip line 6 having the above structure and the current density distribution of the microwave current flowing through the cross section. As understood from this graph 8, the current density distribution sharply increases at the edge portion of the electroless Cu plating layer 5 adjacent to the high dielectric member 7.

In this embodiment, as a strip line, an electroless Cu plating layer is formed on a thick film conductor formed of Ag paste to compensate for a structural defect having a low conductivity on the surface of the thick film conductor and to improve the skin portion. Although the conductive material is shown, it is obvious that the surface portion may be made to have a high conductivity by other means.

Further, in this embodiment, glass is used as the high dielectric member, but other members may be used as long as the dielectric member has a large dielectric constant.

[0019]

As described above, according to the present invention, for example, in a microstrip line in which the skin portion of the strip line has a high conductivity, by arranging high dielectric members adjacent to both sides of the strip line, the current density can be increased. Since the distribution can be concentrated on the skin portion having high conductivity, the microwave transmission loss can be significantly reduced.

Therefore, the signal transmission efficiency in the microwave circuit can be greatly improved, and the circuit can be improved in performance.

[Brief description of drawings]

FIG. 1 is a sectional perspective view showing a schematic structure of a microstrip line according to an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a cross section of the microstrip line of FIG. 1 near a strip line and a current density distribution of microwaves flowing in the strip line.

[Explanation of symbols]

 1 Alumina ceramic substrate 2, 4 Ag thick film conductor layer 3, 5 Electroless Cu plating layer 6 Strip line 7 High dielectric member 8 Current density graph

Claims (4)

[Claims] 1. A microstrip line in which a strip-shaped conductor line is formed on the other surface of a dielectric substrate having a conductor layer as a ground layer on one surface, the dielectric strip being adjacent to the conductor line. A microstrip line, wherein a dielectric member having a dielectric constant higher than that of the periphery of the conductor line is arranged on a body substrate. 2. The microstrip line according to claim 1, wherein the conductor line has a higher conductivity in a skin portion than an inner conductivity. 3. The microstrip line according to claim 1, wherein the conductor line is formed by forming an electroless Cu plating layer on an Ag thick film conductor. . 4. The micro according to claim 1, wherein the dielectric member adjacent to the conductor line has a dielectric constant higher than that of the dielectric substrate. Strip line.