Composite transmission line and electronic device

A composite transmission line includes a laminated insulator including insulator layers, signal transmission lines including first and second signal transmission lines and a power transmission line. The power transmission line includes a power transmission conductor pattern along the insulator layers, and an interlayer connection conductor that interlayer-connects power transmission conductor patterns. The first signal conductor pattern of the first signal transmission line, the second signal conductor pattern of the second signal transmission line, and the power transmission conductor pattern are parallel or substantially parallel to each other on the insulator layers that are mutually different from each other. The first and second signal conductor patterns interpose a first ground conductor in the laminating direction of the insulator layers. The power transmission line is in a side portion of the first signal conductor pattern.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a transmission line incorporated in an electronic device, and particularly to a composite transmission line provided with a plurality of lines, and an electronic device provided with such a composite transmission line.

2. Description of the Related Art

Conventionally, various kinds of transmission lines that transmit a high frequency signal have been devised. For example, Japanese Patent Laid-Open publication No. 2014-179297 discloses a multiple-conductor flat cable that has an analog signal line and a digital signal line. The multiple-conductor flat cable includes an analog cable portion formed such that a plurality of ground signal lines and a plurality of analog signal lines are alternately arranged side by side across a signal transmission direction and each pair of the ground signal lines and the analog signal lines are joined while being electrically insulated from each other. In addition, a digital cable portion is formed such that a plurality of digital signal lines are arranged side by side across the signal transmission direction and each pair of the digital signal lines are connected while being electrically insulated from each other. Further, the analog cable portion and the digital cable portion are arranged in parallel to each other in an unfolded state, and the analog cable portion is rolled up or folded in a direction across the signal transmission direction so as to cover the digital cable portion.

In such a conventional multiple-conductor flat cable disclosed in Japanese Patent Laid-Open publication No. 2014-179297, necessary signal lines are combined to configure a cable that individually transmits various kinds of signals.

The multiple-conductor flat cable that transmits various kinds of signals is capable of transmitting the various kinds of signals by one cable and is thus also useful as a component in an electronic device that is required to be small in size. For example, a plurality of circuit boards are incorporated in the housing of an electronic device, and the plurality of circuit boards are connected by a multiple-conductor flat cable.

In a case in which not only signal transmission but also power transmission is performed in a small transmission line incorporated in the housing of such an electronic device, in a transmission line that transmits various kinds of signals, it is important to prevent the size (thickness and width) from increasing and to also significantly reduce interference between lines.

SUMMARY OF THE INVENTION

In view of the foregoing, preferred embodiments of the present invention provide a composite transmission line that enables power transmission as well as signal transmission. In addition, preferred embodiments of the present invention also provide a composite transmission line capable of significantly reducing or preventing interference between lines effectively without making a structure complicated.

A composite transmission line according to a preferred embodiment of the present invention includes a plurality of signal transmission lines, a power transmission line, and a laminated insulator in which a plurality of insulator layers are laminated on each other, the laminated insulator including the plurality of signal transmission lines and the power transmission line, and the plurality of signal transmission lines include at least a first signal transmission line and a second signal transmission line, the first signal transmission line includes a first signal conductor pattern, the second signal transmission line includes a second signal conductor pattern, the power transmission line includes a power transmission conductor pattern defined by power transmission conductor patterns along a plurality of insulator layers of the laminated insulator, and a first interlayer connection conductor that interlayer-connects the power transmission conductor patterns, the first signal conductor pattern, the second signal conductor pattern, and the power transmission conductor pattern extend in a same or substantially same direction, the first signal conductor pattern and the second signal conductor pattern interpose a first ground conductor between the first signal conductor pattern and the second signal conductor pattern in a laminating direction of the plurality of insulator layers, and the power transmission line is in a side portion of the first signal conductor pattern.

According to the above configuration, a composite transmission line capable of being significantly reduced or prevented from increasing in size due to the installation of a power transmission line and of simultaneously performing signal transmission and power transmission is obtained. In addition, since being provided with power transmission conductor patterns along with a plurality of insulator layers, the power transmission line is able to decrease a conductor loss while being small and to significantly reduce variation in a power supply voltage due to a voltage drop.

A power transmission line according to a preferred embodiment of the present invention may preferably be located in a side portion of the first signal conductor pattern and the second signal conductor pattern. Accordingly, the number of power transmission conductor patterns and first interlayer connection conductors that define a power transmission line is able to be increased, which is able to further decrease a conductor loss.

The first signal transmission line may preferably be an unbalanced line for a high-frequency analog signal, for example, and the second signal transmission line may preferably be a differential line for a digital signal, for example.

The power transmission line may preferably be located at a position (height) closer to the first signal conductor pattern than to the second signal conductor pattern, in the laminating direction of the plurality of insulator layers. Accordingly, interference between the first signal transmission line and the second signal transmission line through the power transmission line is significantly reduced or prevented.

A number of second signal conductor patterns may preferably be larger than the number of first signal conductor patterns. Accordingly, the power transmission line is structure such that a position in which the power transmission line extends is shifted in a direction of an insulator layer on which the first signal conductor pattern that is smaller in number than the second signal conductor patterns is located, and thus a space in a width direction is able to be expanded. In other words, space efficiency is able to be achieved. In addition, since a relatively large number of conductors become difficult to be overlapped in the thickness direction, a flexible property becomes difficult to be obstructed.

In a power transmission line according to a preferred embodiment of the present invention, a second ground conductor may preferably be located on a side opposite to the first ground conductor, with respect to the first signal conductor pattern. Accordingly, a better shielding effect of the surface on the side on which the second ground conductor is located is achieved, and higher isolation between the second signal transmission line and the power transmission line, and the first signal transmission line is achieved.

The second ground conductor and the first ground conductor may preferably be connected to each other through a second interlayer connection conductor, at a position closer to the power transmission line than to the first signal conductor pattern. Accordingly, while the shielding effect is further improved, the isolation between the first signal transmission line and the power transmission line is able to be improved.

The second ground conductor and the first ground conductor may preferably be connected to each other through a third interlayer connection conductor, at a position on the opposite side of the power transmission line, with respect to the first signal conductor pattern. Accordingly, the isolation between the outside and the second signal conductor pattern, and the first signal conductor pattern is improved.

The power transmission line may preferably be electrically connected to at least the second ground conductor. Accordingly, at least the second ground conductor defines and functions as a power transmission line, and a conductor loss of the power transmission line is reduced and heat dissipation is increased. In addition, the power transmission line defines and functions as a ground conductor of the first signal transmission line, and the shielding property of the first signal transmission line is increased.

A third ground conductor may preferably be located on a side opposite to the first ground conductor, with respect to the second signal conductor pattern, and the power transmission line may preferably be electrically connected to the third ground conductor. Accordingly, the second ground conductor and the third ground conductor define and function as a power transmission line, and a conductor loss of the power transmission line is reduced and heat dissipation is increased. In addition, the power transmission line defines and functions as a ground conductor of the first signal transmission line and the second signal transmission line, and the shielding property of the first signal transmission line and the second signal transmission line is increased.

In a power transmission line according to a preferred embodiment of the present invention, a power transmission ground conductor that is electrically separated from the first ground conductor may preferably be further provided. Accordingly, higher isolation between the power transmission line and the signal transmission line is achieved.

In a power transmission line according to a preferred embodiment of the present invention, a third ground conductor may preferably be located on a side opposite to the first ground conductor, with respect to the second signal conductor pattern. Accordingly, a better shielding effect of the surface on the side on which the third ground conductor is located is achieved, and higher isolation between the first signal transmission line and the power transmission line is achieved.

The third ground conductor and the first ground conductor may preferably be connected to each other through a fourth interlayer connection conductor. Accordingly, the isolation between the outside, the power transmission line, and the first signal conductor pattern, and the second signal conductor pattern is improved.

The fourth interlayer connection conductor may preferably be located on both sides across the second signal conductor pattern in the width direction of the interlayer connection conductor. Accordingly, the isolation between the outside, the power transmission line, and the first signal conductor pattern, and the second signal conductor pattern is further improved.

The power transmission line may preferably be disposed over the plurality of insulator layers of the laminated insulator from an insulator layer including the second ground conductor to an insulator layer including the third ground conductor. Accordingly, the space from the insulator layer including the second ground conductor to the insulator layer including the third ground conductor is used effectively and thus a conductor loss of the power transmission line is reduced.

In a power transmission line according to a preferred embodiment of the present invention, an external connection terminal that is electrically connected to the first signal transmission line and the second signal transmission line may preferably be located near or adjacent to the second signal transmission line of the laminated insulator. Accordingly, the total length of a connection path between the external connection terminal and the first and second transmission lines becomes short, and an unwanted parasitic component is significantly reduced or prevented. In addition, since it becomes easy to make a space to locate wiring smaller, it becomes easy to miniaturize the size of the entire composite transmission line.

In a power transmission line according to a preferred embodiment of the present invention, the laminated insulator may preferably have flexibility. Accordingly, the composite transmission line is able to be located along a limited space in an electronic device.

In a power transmission line according to a preferred embodiment of the present invention, a bent portion that bends in a direction perpendicular or substantially perpendicular to the laminating direction of the plurality of insulator layers may preferably be provided, and, in a plan view of the plurality of insulator layers, the power transmission line may preferably be located closer to an inner peripheral side than to the first signal conductor pattern and the second signal conductor pattern. Accordingly, since the curvature radius of the first signal conductor pattern and the second signal conductor pattern in the bent portion is kept large and distance is able to be separated, the interference between the first signal conductor patterns or between the second signal conductor patterns in the bent portion is reduced. In addition, since, in the bent portion, the power transmission line is located between the first signal conductor patterns, the first signal conductor patterns are shielded by the power transmission line and thus the interference between the first signal conductor patterns is also significantly reduced or prevented even by such shielding action. Similarly, the interference between the second signal conductor patterns is significantly reduced or prevented.

In a power transmission line according to a preferred embodiment of the present invention, the power transmission line may preferably be located in the side portion located on both sides of the plurality of signal transmission lines. Accordingly, in the vertical section of the laminated insulator, at least the power transmission line has a symmetrical shape, which significantly reduces or prevents the laminated insulator from being warped or twisted.

An electronic device according to a preferred embodiment of the present invention includes the composite transmission line according to any one of the above-described preferred embodiments of the present invention, a first high-frequency circuit, and a second high-frequency circuit, and the first high-frequency circuit and the second high-frequency circuit are connected to each other by the composite transmission line. Accordingly, a smaller electronic device is provided.

According to various preferred embodiments of the present invention, a composite transmission line that is capable of transmitting various kinds of signals and also transmitting power while being small is obtained.

In addition, according to various preferred embodiments of the present invention, a composite transmission line in which the interference between lines is significantly reduced or prevented effectively while the structure is not made complicated is able to be obtained.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a plurality of preferred embodiments of the present invention will be described with reference to the attached drawings and several specific examples. In the drawings, components and elements assigned with the same reference numerals or symbols will represent identical components and elements. In preferred embodiments after the second preferred embodiment, a description of matters common to the first preferred embodiment will be omitted, and different matters are mainly described. In particular, the same operational effects by the same configuration will not be described one by one for each preferred embodiment.

First Preferred Embodiment

FIG. 1is a perspective view of a composite transmission line1according to a first preferred embodiment of the present invention.FIG. 2Ais a front view of the composite transmission line1andFIG. 2Bis a view illustrating a state in which the composite transmission line1is formed.

The composite transmission line1preferably is a composite transmission line in which two signal transmission lines and one power transmission line are provided in a laminated insulator10. The composite transmission line (hereinafter simply referred to as “transmission line”)1includes a first signal transmission line, a second signal transmission line, and a power transmission line (power supply line).

The transmission line1is long in an X direction and performs signal transmission and power transmission (supply of a power supply voltage) in the X direction. The Y direction illustrated inFIG. 1is a width direction of the transmission line1, and the Z direction is a thickness direction of the transmission line1.

The transmission line1may preferably be provided with external connection terminals110and210in order to be used as a cable. The external connection terminal110is defined by connectors111,112, and113, and the external connection terminal210is defined by connectors211,212, and213. First signal transmission line connectors111and211are connectors connected to the opposite ends of the first signal transmission line. Second signal transmission line connectors112and212are connectors connected to the opposite ends of the second signal transmission line. Power transmission line connectors113and213are connectors connected to the opposite ends of the power transmission line.

Since each insulator layer of the laminated insulator10of the transmission line1is preferably made of a thermoplastic resin base material such as a liquid crystal polymer and has flexibility, a large portion of the transmission line1has flexibility. The transmission line1is incorporated in an electronic device while keeping the shape of a straight line as illustrated inFIG. 2Aor is incorporated in an electronic device preferably by being nipped with a tool and formed into a predetermined shape by being heated locally as illustrated inFIG. 2B. Since the transmission line1, if being formed in this way, will keep the predetermined shape, the transmission line1is able to be easily incorporated into an electronic device while keeping the desired shape, and thus workability is increased.

FIG. 3is an exploded perspective view of the transmission line1.FIG. 4is a cross-sectional view taken along a line A-A illustrated inFIG. 1. InFIG. 3, a protective insulating film9on the surface of the transmission line1is omitted.

The transmission line1is provided with the laminated insulator10in which insulator layers11,12,13,14, and15are laminated on each other, a plurality of conductor patterns extending along the insulator layers11,12,13,14, and15inside the laminated insulator10, and a plurality of interlayer connection conductors extending in the laminated insulator10.

A first ground conductor21is provided on the upper surface of the insulator layer13, a second ground conductor22is provided on the upper surface of the insulator layer15, and a third ground conductor23is provided on the upper surface of the insulator layer11.

A first signal conductor pattern31is provided on the upper surface of the insulator layer14, and second signal conductor patterns32A and32B are provided on the upper surface of the insulator layer12. The first signal conductor pattern31is located between the first ground conductor21and the second ground conductor22. In addition, the second signal conductor patterns32A and32B are located between the first ground conductor21and the third ground conductor23. In other words, the first signal conductor pattern31and the second signal conductor patterns32A and32B may preferably interpose the first ground conductor21between the first signal conductor pattern31and the second signal conductor patterns32A and32B in the laminating direction (the Z direction) of the insulator layer.

Conductor patterns61A and61B are located on the upper surface of the insulator layer14, and interlayer connection conductors71A and71B that connect the first ground conductor21and the conductor patterns61A and61B are located in the insulator layer13. In addition, interlayer connection conductors72A and72B that connect the second ground conductor22and the conductor patterns61A and61B are located in the insulator layer14. Therefore, the second ground conductor22and the first ground conductor21are interlayer-connected to each other by the interlayer connection conductors71A,71B,72A, and72B and the conductor patterns61A and61B. The interlayer connection conductor71B and72B corresponds to the “second interlayer connection conductor”, and the interlayer connection conductor71A and72A corresponds to the “third interlayer connection conductor”.

Conductor patterns62A and62B are located on the upper surface of the insulator layer12, and interlayer connection conductors73A and73B that connect the third ground conductor23and the conductor patterns62A and62B are located in the insulator layer11. In addition, interlayer connection conductors74A and74B that connect the first ground conductor21and the conductor patterns62A and62B are located in the insulator layer12. Therefore, the third ground conductor23and the first ground conductor21are interlayer-connected to each other by the interlayer connection conductors73A,73B,74A, and74B and the conductor patterns62A and62B. The interlayer connection conductor73A,73B,74A and74B corresponds to the “fourth interlayer connection conductor”.

Power transmission conductor patterns41,42, and43that extend along the first signal conductor pattern31and the second signal conductor patterns32A and32B are respectively provided on the upper surface of the insulator layers12,13, and14. An interlayer connection conductor51that interlayer-connects the power transmission conductor patterns41and42is provided in the insulator layer12, and an interlayer connection conductor52that interlayer-connects the power transmission conductor patterns42and43is provided in the insulator layer13. The interlayer connection conductor51and52corresponds to the “first interlayer connection conductor”.

The first signal conductor pattern31, the second signal conductor patterns32A and32B, and the power transmission conductor patterns41,42, and43are parallel or substantially parallel to each other on the plurality of insulator layers of the laminated insulator10that are mutually different from each other.

A power transmission line40is located, in the present preferred embodiment, in a side portion of the first signal conductor pattern31and the second signal conductor patterns32A and32B.

The first signal conductor pattern31, the first ground conductor21, and the second ground conductor22define the first signal transmission line. In addition, the second signal conductor patterns32A and32B, the first ground conductor21, and the third ground conductor23define the second signal transmission line. The power transmission conductor patterns41,42, and43and the interlayer connection conductors51and52define the power transmission line40. The first ground conductor21, the second ground conductor22, and the third ground conductor23also define and function as a power transmission ground conductor.

The first signal transmission line is an unbalanced line that transmits a high-frequency analog signal, for example, and the second signal transmission line is a differential (balanced) line that transmits a digital signal, for example. The power transmission line40is a power supply line that supplies a power supply voltage, for example.

According to the present preferred embodiment, a composite transmission line capable of being significantly reduced or prevented from increasing in size due to the installation of a power transmission line and of simultaneously performing signal transmission and power transmission is obtained. In addition, since being provided with power transmission conductor patterns along with a plurality of insulator layers, the power transmission line is able to decrease a conductor loss though being small and to significantly reduce variation in a power supply voltage due to a voltage drop.

Moreover, according to the present preferred embodiment, since the second signal transmission line defined by the second signal conductor patterns32A and32B is a differential (balanced) line, the distance between the second signal conductor patterns32A and32B and the first ground conductor21and the distance between the second signal conductor patterns32A and32B and the third ground conductor23hardly affect the characteristic impedance of the line. In contrast, the first signal transmission line defined by the first signal conductor pattern31, the first ground conductor21, and the second ground conductor22is an unbalanced transmission line, and, in order to set a predetermined characteristic impedance (50 Ohm, for example), the distance between the first ground conductor21and the second ground conductor22is not able to be significantly reduced. By arranging the power transmission line40in the side portion of this first signal transmission line, the power transmission line40is able to be within a limited thickness range. In other words, an increase in thickness is significantly reduced or prevented.

In addition, in the present preferred embodiment, since the second ground conductor22is located on the side opposite to the first ground conductor21with respect to the first signal conductor pattern31, in other words, since the first signal conductor pattern has a stripline structure, a higher shield effect of the first signal transmission line is achieved, and higher isolation between the first signal transmission line and the second signal transmission line is achieved.

Moreover, since the second ground conductor22and the first ground conductor21are interlayer-connected to each other by the interlayer connection conductors71A,71B,72A, and72B and the conductor patterns61A and61B, the first signal transmission line is shielded by such interlayer connection portions and the first and second ground conductors.

Further, since the interlayer connection conductors71B,72B,73B, and74B are located between the first signal conductor pattern31and the power transmission line40, a portion between the first signal conductor pattern31and the second signal conductor pattern32, and the power transmission line40is electromagnetically shielded and the unwanted coupling in the portion is significantly reduced or prevented effectively. Accordingly, the unwanted coupling between the first signal transmission line and the power transmission line40and the indirect unwanted coupling between the first signal transmission line and the second signal transmission line through the power transmission line40are significantly reduced or prevented effectively.

In addition, since being interlayer-connected by the interlayer connection conductors73A,73B,74A, and74B and the conductor patterns62A and62B, the second signal transmission line is shielded by such interlayer connection portions and the first and third ground conductors. Accordingly, the isolation between the first signal transmission line and the second signal transmission line and the isolation between the first and second signal transmission lines and the power transmission line located in the side portion are improved.

As illustrated inFIG. 3, a first end of the first signal conductor pattern31is connected to a first signal transmission line connector connection electrode181through the interlayer connection conductor and the conductor pattern, and a second end of the first signal conductor pattern31is connected to a first signal transmission line connector connection electrode281through the interlayer connection conductor and the conductor pattern.

The first ends of the second signal conductor patterns32A and32B are respectively connected to second signal transmission line connector connection electrodes182A and182B through the interlayer connection conductor and the conductor pattern, and the second ends of the second signal conductor patterns32A and32B are respectively connected to second signal transmission line connector connection electrodes282A and282B through the interlayer connection conductor and the conductor pattern.

It is to be noted that, while a conductor pattern31C electrically connected to the first signal transmission line is preferably located on the same layer (insulator layer)12as the second signal conductor patterns32A and32B, a ground conductor pattern24is located between the conductor pattern31C and the second signal conductor patterns32A and32B. Since the first signal conductor pattern (conductor pattern31C) and the second signal conductor patterns32A and32B are shielded by the ground conductor pattern24, the isolation between the first signal transmission line and the second signal transmission line is maintained.

The first end of each of the power transmission conductor patterns41,42, and43is connected to a power transmission line connector connection electrode183through the interlayer connection conductor and the conductor pattern, and a second end of each of the power transmission conductor patterns41,42, and43is connected to a power transmission line connector connection electrode283through the interlayer connection conductor and the conductor pattern. Both the first end and the second end are connected to the power transmission line connector connection electrodes183and283through a plurality of interlayer connection conductors51A and51B. This structure reduces a conductor loss.

The first signal transmission line connectors111and211illustrated inFIG. 1are respectively connected to (mounted on) the first signal transmission line connector connection electrodes181and281. The second signal transmission line connector112illustrated inFIG. 1is connected to (mounted on) the second signal transmission line connector connection electrodes182A and182B, and the second signal transmission line connector212is connected to (mounted on) the second signal transmission line connector connection electrodes282A and282B.

The power transmission line connectors113and213illustrated inFIG. 1are respectively connected to (mounted on) the power transmission line connector connection electrodes183and283.

A high-speed digital line is often defined by a differential line, and a large number of signal lines such as an MIPI (registered trademark) (Mobile Industry Processor Interface) or a USB (Universal Serial Bus) are often used. According to the present preferred embodiment, since the external connection terminals (connectors111,112,211, and212) that are electrically connected to the first signal transmission line and the second signal transmission line are located near or adjacent to the second signal transmission line of the laminated insulator10, the total length of a connection path between the external connection terminals and the first and second transmission lines becomes short, and an unwanted parasitic component is significantly reduced or prevented. In addition, since it becomes easy to make a space to provide wiring smaller, it becomes easy to miniaturize the size of the entire composite transmission line1.

It is to be noted that the insulator layers11to15each are an insulator sheet portion of a one-side copper-clad insulator sheet of which the one side is attached with copper foil, for example. This insulator sheet is a sheet made of a liquid crystal polymer (LCP), for example. Since the dielectric constant of a liquid crystal polymer is low, even if the signal conductor pattern and the ground conductor pattern are adjacent to each other, the capacitance component of a line is able to be significantly reduced or prevented. In addition, since the dielectric loss tangent is low, a transmission loss is able to be significantly reduced or prevented. Further, since the temperature dependence of the dielectric loss tangent is low, the characteristic change due to an environmental change is significantly reduced or prevented. Moreover, the various conductor patterns have been obtained preferably by patterning the copper foil attached on the insulator sheet. The laminated insulator10is formed preferably by laminating a plurality of insulator sheets and bonding the plurality of insulator sheets with heat and pressure.

Second Preferred Embodiment

According to a second preferred embodiment of the present invention, a description is given of several transmission lines that are partially different in structure from the transmission line1described in the first preferred embodiment.

FIG. 5is a cross-sectional view of the transmission line2A,FIG. 6is a cross-sectional view of the transmission line2B, andFIG. 7is a cross-sectional view of the transmission line2C. The external shape of all transmission lines is the same or substantially the same as the external shape illustrated inFIG. 1.

In the transmission line2A illustrated inFIG. 5, the conductor pattern61B is located on the upper surface of the insulator layer14, and the interlayer connection conductor71B that connects the first ground conductor21and the conductor pattern61B is located in the insulator layer13. In addition, the interlayer connection conductor72B that connects the second ground conductor22and the conductor pattern61B is located in the insulator layer14. Therefore, the second ground conductor22and the first ground conductor21are interlayer-connected to each other by the interlayer connection conductors71B and72B and the conductor pattern61B. Then, such an interlayer connection portion is located at a position close to the power transmission line40.

In this way, since the interlayer connection portion that connects the first ground conductor21and the second ground conductor22of the first signal transmission line is located close to the power transmission line40, a portion between the first signal conductor pattern31and the power transmission line40is electromagnetically shielded, and the unwanted coupling in the portion is significantly reduced or prevented effectively. Accordingly, the unwanted coupling between the first signal transmission line and the power transmission line40and the indirect unwanted coupling between the first signal transmission line and the second signal transmission line through the power transmission line40are significantly reduced or prevented effectively.

In the transmission line2B illustrated inFIG. 6, the conductor pattern62B is located on the upper surface of the insulator layer12, and the interlayer connection conductor73B that connects the third ground conductor23and the conductor pattern62B is located in the insulator layer11. In addition, the interlayer connection conductor74B that connects the first ground conductor21and the conductor pattern62B is located in the insulator layer12. Therefore, the third ground conductor23and the first ground conductor21are interlayer-connected to each other by the interlayer connection conductors73B and74B and the conductor pattern62B. Then, such an interlayer connection portion is located at a position close to the power transmission line40.

In this way, since the interlayer connection portion that connects the first ground conductor21and the third ground conductor23of the second signal transmission line is located close to the power transmission line40, a portion between the second signal conductor patterns32A and32B and the power transmission line40is electromagnetically shielded, and the unwanted coupling in the portion is significantly reduced or prevented effectively. Accordingly, the unwanted coupling between the second signal transmission line and the power transmission line40and the indirect unwanted coupling between the first signal transmission line and the second signal transmission line through the power transmission line40are significantly reduced or prevented effectively.

The transmission line2C illustrated inFIG. 7is a transmission line provided with a structure in which the transmission line2A and the transmission line2B are combined. In this transmission line2C, the interlayer connection portion of the first ground conductor21and the second ground conductor22and the interlayer connection portion of the first ground conductor21and the third ground conductor23are located at a position close to the power transmission line40. Accordingly, the indirect unwanted coupling between the first signal transmission line and the second signal transmission line through the power transmission line40is significantly reduced or prevented effectively.

Third Preferred Embodiment

According to a third preferred embodiment of the present invention, a description is given of several transmission lines that are partially different in the structure of the power transmission line from the transmission line1described in the first and second preferred embodiments.FIG. 8is a cross-sectional view of the transmission line3A, andFIG. 9is a cross-sectional view of the transmission line3B. The third preferred embodiment is different in the position of the power transmission line40in particular from the first and second preferred embodiments.

In the transmission line3A illustrated inFIG. 8, the power transmission conductor patterns41,42, and43are respectively provided on the upper surfaces of the insulator layers13,14, and15. The interlayer connection conductor51that interlayer-connects the power transmission conductor patterns41and42is provided in the insulator layer13, and the interlayer connection conductor52that interlayer-connects the power transmission conductor patterns42and43is provided in the insulator layer14. Other basic configurations are the same as the basic configuration of the transmission lines described in the first and second preferred embodiment.

In this way, the power transmission line40is located in the side portion of the first signal transmission line defined by the first signal conductor pattern31, the first ground conductor21, and the second ground conductor22. In addition, the power transmission line40is located at a position (height) closer to the first signal conductor pattern31than to the second signal conductor patterns32A and32B, in the laminating direction of the insulator layers. In particular, in an example illustrated inFIG. 8, the side portion of the first signal transmission line is covered with the power transmission line40. Accordingly, the interference between the first signal transmission line and the second signal transmission line through the power transmission line40is significantly reduced or prevented. The distance between the power transmission line40and the second signal conductor patterns32A and32B is relatively larger as compared with the distance between the power transmission line40and the first signal conductor pattern31. Therefore, even though a conductor such as the interlayer connection conductors73B and74B and the conductor pattern62B is not provided, the power transmission line40and the second signal conductor patterns32A and32B are able to be significantly reduced or prevented from interfering.

The transmission line3B illustrated inFIG. 9also includes the power transmission line40in the same layer (the same height) as the first signal transmission line. According to the structure, an area in the plane direction in which the second signal conductor pattern is able to be disposed is expanded. In the transmission line3B, other second signal conductor patterns33A and33B in addition to the second signal conductor patterns32A and32B are also provided. The second signal transmission line by the second signal conductor patterns33A and33B is a differential (balanced) line and transmits a digital signal, for example.

It is to be noted that the transmission line3B illustrated inFIG. 9as well as the example ofFIG. 8may also include the interlayer connection conductors71B and72B and the conductor pattern61B may be provided between the first signal conductor pattern31and the power transmission line40. With this configuration, it is possible to significantly reduce or prevent the interference between the power transmission line40and the first signal conductor pattern31. In addition, the indirect unwanted coupling between the first signal transmission line and the second signal transmission line through the power transmission line40is significantly reduced or prevented effectively.

According to the present preferred embodiment, by displacing the power transmission line40in the direction of an insulator layer on which the first signal conductor pattern31that is smaller in number than the second signal conductor patterns32A,32B,33A, and33B is located, it is possible to expand a space in a width direction. In other words, space efficiency is able to be achieved. In addition, since a relatively large number of conductors become difficult to be overlapped in the thickness direction, the flexible property of the transmission lines becomes difficult to be obstructed. It is to be noted, in particular, a portion of the power transmission line40may preferably be located in the same layer as the first signal conductor pattern31.

Fourth Preferred Embodiment

According to a fourth preferred embodiment of the present invention, a description is given of a transmission line4that is partially different in structure from the transmission line3B described in the third preferred embodiment.

FIG. 10is a cross-sectional view of the transmission line4. Unlike the transmission line3B illustrated inFIG. 9, the interlayer connection conductors71B and72B and the conductor pattern61B are provided between the first signal conductor pattern31and the power transmission line40. In addition, the conductor patterns42and43and the interlayer connection conductor52define the power transmission line40. Further, the first ground conductor21is extended to between the power transmission line40and the second signal conductor pattern33B. Other configurations are the same as the configuration of the transmission line3B.

According to the present preferred embodiment, since the first ground conductor21covers the upper portion of the power transmission line40, sufficient isolation between the first signal conductor pattern31and the second signal conductor patterns32and33is ensured, and the isolation between the power transmission line40and the second signal conductor pattern33is further improved.

Fifth Preferred Embodiment

According to a fifth preferred embodiment of the present invention, a description is given of a transmission line that is different in the structure of the power transmission line from the transmission line1described in the first preferred embodiment.

FIG. 11is a cross-sectional view of a transmission line1E according to the fifth preferred embodiment of the present invention. The transmission line1E is different in the structure of the power transmission line40from the transmission line1illustrated inFIG. 4in the first preferred embodiment.

In the transmission line1E according to the present preferred embodiment, the power transmission line40is defined by the power transmission conductor patterns41,42,43,44, and45and the interlayer connection conductors51,52,53, and54. This power transmission line40may preferably be disposed over the insulator layers of the laminated insulator from the insulator layer on which the second ground conductor22is located to the insulator layer on which the third ground conductor23is located. In addition, according to the present preferred embodiment, the width of the interlayer connection conductors51to54of the power transmission line40is larger than the width of the interlayer connection conductors71A,71B,72A,72B,73A, and73B that connect the first ground conductor21, the second ground conductor22, and the third ground conductor23. Other configurations are the same as the configuration of the transmission line1described in the first preferred embodiment. The interlayer connection conductor51,52,53and54corresponds to the “first interlayer connection conductor”.

According to the present preferred embodiment, the space from the insulator layer on which the second ground conductor22is located to the insulator layer on which the third ground conductor23is located is used effectively and thus a conductor loss of the power transmission line is reduced. Moreover, according to the present preferred embodiment, since the width of the interlayer connection conductor of the power transmission line40is large, the conductor loss of the power transmission line is further reduced.

Sixth Preferred Embodiment

According to a sixth preferred embodiment of the present invention, a description is given of a transmission line that is different in the structure of the power transmission line from the transmission line1described in the first preferred embodiment.

FIG. 12is a cross-sectional view of a transmission line1F according to the sixth preferred embodiment of the present invention. The transmission line1F is different in the structure of the power transmission line40from the transmission line1illustrated inFIG. 4in the first preferred embodiment.

InFIG. 12, the power transmission line40is defined by the power transmission conductor patterns41,42, and43and the interlayer connection conductors51and52. In addition, the power transmission line40further includes a power transmission ground conductor49that is electrically separated from the first ground conductor21(thus also electrically separated from the second ground conductor22and the third ground conductor23).

In this way, higher isolation between the ground of the power transmission line and the ground of the signal transmission line is achieved by providing a ground conductor dedicated for power transmission, that is, a ground conductor for power supply. In addition, since the power supply line that is defined by the power transmission line40and the power transmission ground conductor49is a balanced line of which the polarity is reversed, even if this power supply line is combined with the first signal conductor pattern31or the second signal conductor pattern32, a signal that is superimposed on the power supply line by electromagnetic coupling is offset by the power transmission line40and the power transmission ground conductor49. Therefore, the power supply line is less likely to be adversely affected by the electromagnetic coupling.

Seventh Preferred Embodiment

According to a seventh preferred embodiment of the present invention, a description is given of an example that is different in the structure of the power transmission line from the preferred embodiments that have been described.

FIG. 13Ais a cross-sectional view of a transmission line7A according to the seventh preferred embodiment of the present invention. The power transmission line40is defined by the power transmission conductor patterns42and43and the interlayer connection conductors53and54. In addition, the power transmission line40is electrically connected to the second ground conductor22. In this example, the first ground conductor21or the third ground conductor23is able to be used as a counter electrode of the power transmission line40. For example, the first ground conductor21or the third ground conductor23is used as a ground conductor of the power supply line, and the power transmission line40and the second ground conductor22are used as a power supply line. In other words, power is transmitted by the power transmission line40, the second ground conductor22, and the first ground conductor21. Alternatively, the power is transmitted by the power transmission line40, the second ground conductor22, and the third ground conductor23.

In this transmission line7A, the second ground conductor22defines and functions as a portion of the power transmission line. Therefore, the conductor loss of the power transmission line is reduced. In addition, heat dissipation is also increased. Further, the power transmission line40defines and functions as a ground conductor of the first signal transmission line defined by the first signal conductor pattern31, the first ground conductor21, and the second ground conductor22. Accordingly, the shielding property of the first signal transmission line is increased.

FIG. 13Bis a cross-sectional view of another transmission line7B according to the seventh preferred embodiment of the present invention. The power transmission line40is defined by the power transmission conductor patterns41,42, and43and the interlayer connection conductors51,52,53, and54. In addition, the power transmission line40is electrically connected to the second ground conductor22and the third ground conductor23individually. In this example, the first ground conductor21is able to be used as a counter electrode of the power transmission line40. For example, the first ground conductor21is used as a ground conductor of the power supply line, and the power transmission line40, the second ground conductor22, and the third ground conductor23are used as a power supply line.

In this transmission line7B, the second ground conductor22and the third ground conductor23define and function as a portion of the power transmission line. Therefore, the conductor loss of the power transmission line is reduced. In addition, heat dissipation is also increased. Further, the power transmission line40defines and functions as a ground conductor of the first signal transmission line defined by the first signal conductor pattern31, the first ground conductor21, and the second ground conductor22. Similarly, the power transmission line40defines and functions as a ground conductor of the second signal transmission line defined by the second signal conductor pattern32, the first ground conductor21, and the third ground conductor23. Accordingly, the shielding property of the first signal transmission line and the second signal transmission line is increased.

Eighth Preferred Embodiment

According to an eighth preferred embodiment of the present invention, a description is given of an example of a transmission line that includes a bent portion.

FIG. 14is a plan view of a transmission line18according to the eighth preferred embodiment of the present invention. However, inFIG. 14, the first signal conductor pattern and the second signal conductor pattern are schematically illustrated as a single linear pattern.

A cross-sectional structure of the first signal conductor pattern31and the second signal conductor pattern32and the power transmission line40of the power transmission line18is preferably the same as the cross-sectional structure that has been described mainly in the first preferred embodiment. The transmission line18may preferably include a bent portion BP that bends in a direction (plane direction) perpendicular or substantially perpendicular to the laminating direction of the plurality of insulator layers, and, in a plan view of the plurality of insulator layers, the power transmission line40may preferably be located closer to the inner peripheral side than to the first signal conductor pattern31and the second signal conductor pattern32.

According to the present preferred embodiment, since the curvature radius of the first signal conductor pattern31and the second signal conductor pattern32in the bent portion BP is kept large and distance is able to be separated, the interference between the first signal conductor patterns31or between the second signal conductor patterns32in the bent portion BP is reduced. The symbol of a capacitor inFIG. 14indicates a parasitic capacitance generated between the first signal conductor patterns31, and a parasitic capacitance generated between the second signal conductor patterns32. Such a parasitic capacitance is the cause of distortion of a transmission signal. In the present preferred embodiment, the transmission signal is also significantly reduced or prevented from being distorted due to the parasitic capacitance in the bent portion BP.

In addition, since, in the bent portion BP, the power transmission line40is located between the first signal conductor patterns31, the first signal conductor patterns31are shielded by the power transmission line40, and the interference between the first signal conductor patterns31is also significantly reduced or prevented by the shielding action. Similarly, the interference between the second signal conductor patterns is significantly reduced or prevented.

Ninth Preferred Embodiment

According to a ninth preferred embodiment of the present invention, a description is given of an example of a transmission line provided with a plurality of power transmission lines.

FIG. 15is a cross-sectional view of a transmission line19according to the ninth preferred embodiment of the present invention. In the example illustrated inFIG. 15, two power transmission lines40A and40B are provided. The power transmission line40A is defined by the power transmission conductor patterns41A,42A, and43A and the interlayer connection conductors51A and52A. In addition, the power transmission line40B is defined by the power transmission conductor patterns41B,42B, and43B and the interlayer connection conductors51B and52B. The first signal conductor pattern31and the first ground conductor21define the first signal transmission line of a microstrip line type. Moreover, the second signal conductor patterns32A and32B and the first ground conductor21define the second signal transmission line of a differential line.

The power transmission lines40A and40B may preferably be respectively located in side portions located on the opposite sides of the first signal conductor pattern31and the second signal conductor pattern32.

According to the present preferred embodiment, in the vertical section of the laminated insulator, at least the power transmission line has a symmetrical shape, which significantly reduces or prevents the laminated insulator from being warped or twisted.

Tenth Preferred Embodiment

FIG. 16Ais a plan view of the inside of a housing of a mobile electronic device5illustrating the mounting state of a transmission line1according to a tenth preferred embodiment of the present invention, andFIG. 16Bis a schematic cross-sectional view illustrating the mounting state of the transmission line1in the housing of the mobile electronic device5.

The mobile electronic device5is provided with a thin housing90. In the housing90, circuit boards91and92, a battery pack93, and the like are provided. A plurality of electronic components are mounted on the surfaces of the circuit boards91and92.

In the housing90, an antenna portion80is defined by a radiating element81and an antenna matching circuit82. The antenna matching circuit82on the circuit board91is connected to the radiating element81through a connection pin83. An RFIC is mounted on the circuit board92and an antenna signal in the 2 GHz band (high-frequency analog signal), for example, is transmitted from the circuit board92to the circuit board91. In addition, a digital signal such as an MIPI (registered trademark) and a USB is transmitted between the circuit board91and the circuit board92. Moreover, electric power supplied from the battery pack93and the like is transmitted between the circuit board91and the circuit board92. As described above, one transmission line1transmits two kinds of signals and also transmits power.

The circuit boards91and92and the battery pack93are located in the housing90so that, in a plan view of the housing90, the battery pack93may be located between the circuit boards91and92. Since the housing90is as thin as possible, the space between the battery pack93and the housing in the thickness direction of the housing90is extremely narrow. Therefore, it is difficult to provide a plurality of cables, such as ordinary coaxial cables, between the battery pack93and the housing90.

The transmission line1according to the present preferred embodiment is structured such that the thickness direction of the transmission line1coincides with the thickness direction of the housing90and thus the transmission line1is able to be passed between the battery pack93and the housing90. Thus, the circuit boards91and92spaced from each other with the battery pack93disposed in the middle are able to be connected to each other by the transmission line1.

Further, even in a case in which a position in which the transmission line1is connected to the circuit boards91and92and a surface of the transmission line1on which the battery pack93is installed are different in the thickness direction of the housing90and thus the transmission line1needs to be curved to be connected, the structure according to the present preferred embodiment is applicable.

Other Preferred Embodiments

In the preferred embodiments of the present invention described above, while an example in which a via filled up with a conductor in a hole in the insulator layer is used as the interlayer connection conductor has been described, the interlayer connection conductor may be defined by a through hole obtained by providing a conductive film on the inner surface of the hole in addition to the via filled up with a conductor in the hole formed in the insulator layer.

Although, in the example illustrated inFIG. 1, the protective insulating film9is located on the surface of the laminated insulator10on which each connector of the laminated insulator10is placed, the protective insulating film9is not essential.

In addition, neither the second ground conductor22nor the third ground conductor23is essential. Moreover, the interlayer connection conductors that connect such ground conductors are not essential, either.

The number of first and second transmission lines is not limited to the combination of “two lines and one line” or “four lines and one line”. For example, a combination of five lines and two lines may be preferable. Even in such a case, by displacing the power transmission line40in the direction of an insulator layer on which the first signal conductor pattern that is small in number is provided, the above described operational effects and advantages are able to be obtained.

Finally, the foregoing preferred embodiments are illustrative in all points and should not be construed to limit the present invention. It is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. For example, configurations illustrated in different preferred embodiments are able to be partially replaced and combined with each other. The scope of the present invention is defined not by the foregoing preferred embodiment but by the following claims. Further, the scope of the present invention is intended to include all modifications within the scopes of the claims and within the meanings and scopes of equivalents.