JP2009181804A - Transmission cable with shield - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission cable with a shield restricted in the amount of electromagnetic noise in a high frequency range and having excellent signal transmission characteristic at low costs. <P>SOLUTION: In this transmission cable with the shield structured by forming an conductor wire, an insulator and a shield conductor in order, the shield conductor is structured of at least two conductive materials having a different conductivity, and the shield conductor formed from a high-conductivity material is arranged on the conductor wire side, and the shield conductor formed from a low-conductivity material is arranged on a side far from the conductor wire, and the thickness of the shield conductor formed from the low-conductivity material is set smaller than the thickness of the shield conductor formed from the high-conductivity material. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transmission line with a shield for transmitting an electrical signal containing a high-frequency component, and more particularly to a shielded cable and a multilayer printed wiring board.

  With the recent increase in processing speed of semiconductor integrated circuits, high-speed electrical signals including high-frequency components of 1 GHz or higher have been exchanged inside and between electronic devices. As a result, an unintended high-frequency electromagnetic field is generated in a transmission line portion such as a cable or a printed wiring board, and there is a concern that the device may malfunction or adversely affect human bodies or adjacent electronic devices. For this reason, the movement which regulates generation | occurrence | production of electromagnetic noise has spread also in the high frequency band of 1 GHz or more, and the technique which suppresses generation | occurrence | production of the unnecessary electromagnetic field in a transmission line part is needed.

  Conventionally, as a technique for suppressing the generation of unnecessary electromagnetic fields from transmission lines, there has been a measure to provide a shield layer around the transmission line and confine the electromagnetic field generated by the current flowing through the transmission line in or near the shield layer. Has been implemented. In general, a transmission line is composed of at least two conductors through which a forward current and a return current flow, and the shield layer is often composed of a conductor material. Hereinafter, two or more conductors constituting the above-described transmission line are simply abbreviated as conductors constituting the transmission line. There are roughly the following two types of forms when the shield layer is installed around the transmission line.

  First, in the installation form of the first shield layer, a shield layer made of a conductor different from the conductor constituting the transmission line is added outside the conductor constituting the transmission line. As a result, the electromagnetic field generated by the conducting wire constituting the transmission line is confined in the vicinity of or inside the shield layer. Further, in the second shield installation form, instead of adding a new conductor as a shield layer, a structure in which a part of the conductors constituting the transmission line covers a part or all of the other conductors. And As a result, the above-mentioned part of the conductors has a function as a shield layer, and an electromagnetic field generated by the other conductors is confined in the vicinity of or inside the part of the conductors.

  Examples of the installation form of the first shield layer described above include shielded pair cable (TwinAx), shielded quad cable, shielded twisted pair cable (FTP), shielded flat cable (FFC), rigid printed wiring board, or flexible There is a microstrip line on a printed wiring board. Similarly, examples of the second shield installation form include a coaxial cable, a strip line on a rigid printed wiring board or a flexible printed wiring board, and the like. However, the above example is merely illustrated for clarifying the classification of the installation form of the shield layer in the shielded transmission line according to the prior art, and does not limit the application range of the present invention.

  Non-Patent Document 1 describing the prior art includes “10.2 Coaxial Cable Noise and Interference” in “Design of High-Speed Signal Board (Application)”. The reason why the literature related to the coaxial cable is cited as Non-Patent Document 1 is that the analysis of the unnecessary current flowing through the shield layer is the most advanced because the structure of the coaxial cable is simple, and the scope of application of the present invention is as follows. It is not meant to be limited to coaxial cables.

  Japanese Patent Laid-Open No. 9-129041 (Patent Document 1) discloses that, in a high-frequency transmission line, the shield layer is composed of a plurality of conductors having different conductivities.

Howard Johnson “High-Speed Signal Board Design (Application)” 2007, Maruzen Co., 596-601 Japanese Patent Laid-Open No. 9-129041

However, in the conventional technology, it is possible to confine the electromagnetic field generated from the transmission line itself in the vicinity or inside of the shield layer. However, since the shield layer is composed of a conductor, the shield layer is connected to an electronic circuit. However, there is a problem in that a current that is not directly related to the purpose of signal transmission flows through the shield layer, which becomes a new source of unnecessary electromagnetic fields. For this reason, in the prior art, measures have been taken to add a noise countermeasure component such as a common mode choke at the connection between the shield layer and the electronic circuit so that no current flows in the shield layer.
In addition to this, it is difficult to say that this is a reasonable measure in view of the above causes, but a measure has been taken to increase the shielding performance of the shield layer by increasing the thickness of the shield layer.

  However, these are a method of adding a new noise countermeasure component and a method of increasing the thickness of the shield layer, and thus there is a problem that the cost of the shielded transmission line is increased.

  The method described in Patent Document 1 is a method for suppressing heat transfer from the outside of the coaxial cable to the inside of the coaxial cable. For this purpose, the shield layer is made of a high-loss material of 99% or more. However, this configuration has a problem that the amount of electromagnetic noise generated cannot be reduced in the high frequency region.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above problems and provide a shielded transmission line having a low amount of electromagnetic noise generated in a high frequency region and having good signal transmission characteristics at a low cost.

  In order to solve the above-mentioned problems in the present invention, the invention of claim 1 is characterized in that one or more conductor lines provided for electrically connecting the input side and the output side of the transmission line, and the input side of the transmission line. And one or more shield conductor wires for electrically connecting the output side and shielding the unnecessary electromagnetic field generated from the conductor wires, and holding and electrically insulating the conductor wires and the shield conductor wires from each other In a shielded transmission line constituted by an insulator for the above, the shield conductor wire is constituted by two or more kinds of conductor materials having different conductivity, and a low-loss conductor is provided on the side of the shield conductor wire close to the conductor wire The shielded transmission line is characterized in that a high-loss conductor material is disposed on the side farther from the material and the conductor wire.

  According to a second aspect of the present invention, there are provided two or more conductor wires provided to electrically connect an input side and an output side of a transmission line, and an insulator for holding the conductor wires and electrically insulating each other. And a shielded transmission line constituted by a shield conductor for shielding an unnecessary electromagnetic field generated from the conductor wire, wherein the shield conductor is constituted by two or more kinds of conductor materials having different conductivity, and the shield A low-loss conductor material is disposed on the side of the conductor close to the conductor wire, a high-loss conductor material is disposed on the side far from the conductor wire, and the thickness of the high-loss conductor material is smaller than the thickness of the low-loss material. It is a transmission line with a shield characterized by these.

  According to a third aspect of the present invention, the one or more conductor wires provided for electrically connecting the input side and the output side of the transmission line, the input side and the output side of the transmission line are electrically connected, and Shielded transmission comprising one or more shielded conductor wires for shielding unwanted electromagnetic fields generated from the conductor wires, and an insulator for holding the conductor wires and the shield conductor wires and electrically insulating them from each other In the line, the shield conductor wire is composed of two or more kinds of conductor materials having different electrical conductivities, and a low loss conductor material is provided on the side of the shield conductor wire close to the conductor wire, and a high loss is provided on the side far from the conductor wire. The shielded transmission line is characterized in that a conductor material is disposed and the thickness of the high loss conductor material is smaller than the thickness of the low loss material.

According to a fourth aspect of the present invention, there are provided two or more conductor wires provided for electrically connecting an input side and an output side of a transmission line, and an insulator for holding the conductor wires and electrically insulating each other. And a shielded transmission line constituted by a shield conductor for shielding an unnecessary electromagnetic field generated from the conductor wire, wherein the shield conductor is constituted by two or more kinds of conductor materials having different conductivity, and the shield A low loss conductor material on the side of the conductor close to the conductor wire, a high loss conductor material on the side far from the conductor wire, and the thickness of the high loss conductor material is smaller than the thickness of the low loss material; and that the thickness of the high losses conductive material, and larger than the skin depth at the lower limit value [nu _min of the frequency region to suppress the generation of unnecessary electromagnetic field from the shielded transmission line δ (ν _min) A shielded transmission line to the butterflies.

According to a fifth aspect of the present invention, the one or more conductor lines provided for electrically connecting the input side and the output side of the transmission line, the input side and the output side of the transmission line are electrically connected, and Shielded transmission comprising one or more shielded conductor wires for shielding unwanted electromagnetic fields generated from the conductor wires, and an insulator for holding the conductor wires and the shield conductor wires and electrically insulating them from each other In the line, the shield conductor wire is composed of two or more kinds of conductor materials having different electrical conductivities, and a low loss conductor material is provided on the side of the shield conductor wire close to the conductor wire, and a high loss is provided on the side far from the conductor wire. A conductive material is disposed, and the thickness of the high-loss conductor material is made smaller than the thickness of the low-loss material, and the thickness of the high-loss conductor material is reduced to an unnecessary electromagnetic field from the shielded transmission line. A shielded transmission line, characterized in that is larger than the skin depth δ (ν _min) in the lower limit value [nu _min of the frequency region to be suppressed from occurring.

  The invention of claim 6 is a shielded multi-wire cable including a shielded pair cable and a shielded twisted pair cable, wherein the shield conductor according to claim 4 is used for a shield layer.

  A seventh aspect of the present invention is a coaxial cable characterized by using the shield conductor wire according to the fifth aspect as an outer conductor.

  The invention according to claim 8 is a rigid printed board and a flexible printed board characterized in that the shield conductor according to claim 4 is used as a ground wiring of a strip line.

  A ninth aspect of the present invention is a rigid printed circuit board and a flexible printed circuit board characterized in that the shield conductor line according to the fifth aspect is used as a ground wiring or a power supply wiring of a microstrip line.

  The invention of claim 10 is a flexible flat cable characterized in that the shield conductor according to claim 4 is used for a shield layer.

  The invention according to claim 11 is the coaxial cable, wherein the outer conductor is constituted by a stranded wire layer formed by twisting a plurality of conductor wires, and the outer conductor is constituted by two or more stranded wire layers, and The inner layer of the stranded wire layer is made of a low-loss conductor material, the outer layer is made of a high-loss conductor material, and the thickness of the stranded wire layer made of the high-loss conductor material is made of the low-loss conductor material. The coaxial cable is characterized by being smaller than the thickness of the stranded wire layer.

The invention according to claim 12 is the coaxial cable, wherein the outer conductor is constituted by a stranded wire layer formed by twisting a plurality of conductor wires, the outer conductor is constituted by two or more stranded wire layers, and The inner layer of the stranded wire layer is made of a low-loss conductor material, the outer layer is made of a high-loss conductor material, and the thickness of the stranded wire layer made of the high-loss conductor material is made of the low-loss conductor material. smaller than the thickness of the strand layer, and the thickness of the high loss strand layer constituted by conductive material, the skin in the lower limit [nu _min of the frequency region to suppress the generation of unnecessary electromagnetic field from the coaxial cable The coaxial cable is characterized by being larger than the depth δ (ν _min ).

  The invention according to claim 13 is a conductor wire constituting the inner conductor, a hollow conductor wire constituting the outer conductor, and an insulator for holding the inner conductor and the outer conductor and electrically insulating each other. In the semi-rigid coaxial cable, the outer conductor is composed of two or more kinds of conductor materials, the low loss conductor material is disposed on the inner surface of the outer conductor, and the high loss conductor material is disposed on the outer surface, and the high loss The semi-rigid coaxial cable is characterized in that the thickness of the conductor material is smaller than the thickness of the low-loss material.

The invention according to claim 14 is a conductor wire constituting the inner conductor, a hollow conductor wire constituting the outer conductor, and an insulator for holding the inner conductor and the outer conductor and electrically insulating each other. In the semi-rigid coaxial cable, the outer conductor is composed of two or more kinds of conductor materials, the low loss conductor material is disposed on the inner surface of the outer conductor, and the high loss conductor material is disposed on the outer surface, and the high loss The thickness of the conductor material is smaller than the thickness of the low-loss material, and the thickness of the high-loss conductor material is the skin at the lower limit value ν _min in the frequency region where it is desired to suppress the generation of unwanted electromagnetic fields from the semi-rigid coaxial cable. This is a semi-rigid coaxial cable characterized by being larger than the depth δ (ν _min ).

  The invention of claim 15 is the semi-rigid coaxial cable according to claim 14, wherein the outer conductor is formed by plating a high loss conductor material on the outer surface of a hollow conductor wire made of a low loss conductor material. This is a semi-rigid coaxial cable.

  According to the present invention, it is possible to realize a shielded transmission line that generates a small amount of electromagnetic noise in a high frequency region and has good signal transmission characteristics at a low cost.

First, the principle of the present invention will be described in detail below.
In the present invention, the high-frequency component of the unnecessary current flowing through the shield conductor is concentrated on the thin surface layer of the shield conductor surface, and the above-described high-frequency component of the unnecessary current flows concentrated on the shield conductor surface far from the transmission line. Focused on the fact that. That is, in order to attenuate the high-frequency component of the above-described unnecessary current, the present invention provides a high-frequency current layer having a thickness higher than the skin depth δ (ν) on the surface far from the transmission line of the shield conductor. A lossy conductor layer is provided. Here, the skin depth δ (ν) at the frequency ν is given by the following equation (1) using the magnetic permeability μ and the conductivity σ of the conductor material, as is well known.

  Hereinafter, the operation of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings, and repeated description thereof is omitted.

  First, FIG. 1 shows a mechanism for generating an unnecessary electromagnetic field from a transmission line having no shield layer. Generally, in order to transmit an electrical signal from the transmission side circuit 1 to the reception side circuit 3, it is necessary to connect the transmission side circuit 1 and the reception side circuit 3 via the transmission line 2. The conducting wire 21 constituting the transmission line 2 connects the signal source 11 of the transmission side circuit 1 and the load 31 of the reception side circuit 3, and as a result, the current flowing through the load 31 of the reception side circuit 3 or both ends of the load 31. The appearing voltage is detected as a received signal. At this time, the current flowing through the conducting wire 21 generates an electromagnetic field 22 according to the law of electromagnetics, and this is observed as an unnecessary electromagnetic field outside the transmission line.

  Next, FIG. 2A shows a mechanism for generating an unnecessary electromagnetic field from the shielded transmission line. In general, the shield layer of a shielded transmission line is configured so that the conductive line 21 constituting the transmission line is partially or completely covered with the shield conductor 23 so that the electromagnetic field 22 generated from the current flowing in the conductive line 21 is generated in the vicinity of the shield conductor 23. Or it plays a role of confinement.

  However, in the transmission line with a shield according to the prior art, an example of which is shown in FIG. 2B, when the shield conductor 23 is electrically connected to the transmission side circuit 1 and the reception side circuit 3, it is directly related to signal transmission. There is a problem that a new unnecessary electromagnetic field 26 is generated when the shield conductor is provided, because the unnecessary current 25 having no current can flow through the shield conductor 23.

  At this time, when the fact that the current flow path is limited to the area of the skin depth δ (ν) of the conductor surface at high frequency and the general law that the high frequency current flows through the path that minimizes the impedance is used, It can be seen that the unnecessary electromagnetic field 26 flows on the surface of the shield conductor 23 far from the transmission line. In addition, the magnitude of the unnecessary current 25 that flows is as follows: (i) the design of the transmission side circuit and the reception side circuit, (ii) the connection method between the shield conductor and the transmission side circuit and the reception side circuit, (iii) the electrical resistance of the shield layer, Therefore, in the transmission line with shield according to the prior art, it is difficult to suppress the generation of the unnecessary electromagnetic field 26 due to the unnecessary current 25 flowing on the shield.

On the other hand, in the shielded transmission line of the present invention, an example of which is shown in FIG. 2 (c), the high frequency component of the unnecessary current 25 is attenuated on the surface of the shield conductor on the side far from the conducting wire constituting the transmission line. Therefore, the generation of the unnecessary electromagnetic field 26 in the high frequency region is suppressed by providing the high-loss conductor layer 41 for the purpose. Since the purpose of the present invention is to attenuate high frequency components of the unwanted current 25, the thickness of the high-loss conductor layer 41 as the lower limit value [nu _min of the frequency region to suppress the generation of unnecessary electromagnetic field, the frequency [nu _min It is sufficient if the skin depth is greater than δ (ν _min ). Since the value of the skin depth δ (ν _min ) for a typical metal is several μm or less at ν _min = 1 GHz as is well known, the thickness of the high-loss conductor layer 41 is the same as that of a shield layer of a normal cable or printed circuit board. Thin enough compared to the thickness.

  Next, FIG. 3A shows a mechanism for generating an unnecessary electromagnetic field from a shielded transmission line of a type different from that in FIG. In the transmission line of FIG. 3 (a), the shield conductor line 24 also serves as a part of the conducting wire constituting the transmission line. Coaxial cables and strip lines of printed wiring boards can be classified as this type of shielded transmission line. In the shielded transmission line of FIG. 3A, the current output from the signal source 11 passes through the lead wire 21 and reaches the reception side circuit, and then returns to the transmission side circuit through the shield conductor line 24. At this time, if the sum of the forward currents flowing through the conducting wire 21 and the sum of the return currents flowing through the shield conductor wire 24 are equal, a radiation electromagnetic field having a size that causes a problem in normal use is present outside the shield conductor wire 24. Does not occur.

  However, in the shielded transmission line according to the prior art shown in FIG. 3B, when the shield conductor wire 24 is connected to the transmission side circuit 1 and the reception side circuit 3 in FIG. Other than the signal current, an unnecessary current 25 that is not directly related to signal transmission can flow, and thereby a new unnecessary electromagnetic field 26 may be generated. This unnecessary current 25 flows on the surface of the shield conductor 24 on the side far from the transmission line for the same reason as in FIG. 2, and the amount of the unnecessary electromagnetic field 26 generated from the unnecessary current 25 in the conventional technique. It is difficult to reduce.

On the other hand, in the shielded transmission line of the present invention, an example of which is shown in FIG. 3 (c), the high-frequency component of the unwanted current 25 is attenuated on the surface far from the conducting wire constituting the transmission line of the shield conductor. The high loss conductor layer 41 is provided to suppress the generation of the unnecessary electromagnetic field 26 in the high frequency region. Since the present invention aims to attenuate the high frequency components of the unwanted current 25, the thickness of the high-loss conductor layer 41 as the lower limit value [nu _min of the frequency region to suppress the generation of unnecessary electromagnetic field, the frequency [nu _min It is sufficient if the skin depth is greater than δ (ν _min ).

  Note that the drawings and explanations given above are merely examples of the operation of the present invention in typical cases, and do not limit the scope of application of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First embodiment]
A first embodiment of the present invention is shown in FIG. FIG. 5A is a cross-sectional view of a shielded pair cable configured as an example of the present invention. FIG. 4A is a cross-sectional view of a shielded pair cable according to the prior art which is a comparison object with FIG.

  In the shielded pair cable according to the prior art shown in FIG. 4A, reference numeral 101 denotes a surrounding medium, 102 denotes a shield conductor, 103 denotes a dielectric, and 106 and 107 denote signal conductors for performing originally intended signal transmission.

  FIG. 4 (b) illustrates the current distribution inside the conductor at a frequency in the vicinity of a direct current for a shielded pair cable according to the prior art. The signal current 123 flows substantially uniformly in the cross sections of the signal conductors 106 and 107 in accordance with the general rule that “DC current flows through a path that minimizes electrical resistance”. The current 121 is a current induced in the shield conductor when the signal current 123 flows, and the current 122 is an unnecessary current mainly generated in the transmission-side electronic circuit or in the connection portion between the transmission-side electronic circuit and the shield conductor. Represents. The current 121 induced by the signal current of the shield layer has a non-uniform distribution in the angular direction corresponding to the spatial distribution of the odd-mode electric field of the pair cable, but has a large skin depth at frequencies near DC. Therefore, it can penetrate deeply into the shield conductor from the inner surface of the shield conductor in the radial direction. The unnecessary current 122 also penetrates deeply into the conductor at a frequency near DC. For this reason, at the frequency near DC, the above-described induced current 121 and unnecessary current 122 flow through the shield conductor in a spatially overlapping manner.

FIG. 4C illustrates the current distribution inside the conductor at high frequency for the shielded pair cable of the prior art. The signal current 143 is concentrated on the opposing surfaces of the signal conductors 106 and 107 due to the skin effect and the proximity effect. In addition, the current in the shield conductor is concentrated in a region having a thickness of about the skin depth δ (ν _min ) on the surface of the shield conductor due to the skin effect of Equation (1). The current 141 induced inside the shield conductor by the signal current has an uneven spatial distribution in the angular direction corresponding to the odd-mode electric field of the pair cable, and shields the electric field created by the charge distribution on the signal conductor. Concentrate on the inner surface of the shield conductor. On the other hand, the unnecessary current 142 is concentrated on the outer surface of the shield conductor according to the general rule that “the high-frequency current flows through a path that minimizes the impedance”.

  FIG. 5A is a cross-sectional view of a shielded pair cable configured as an embodiment of the present invention, in which 104 represents a high-loss conductor layer and 105 represents a low-loss conductor layer. In the present embodiment, the high loss conductor layer 104 is provided in the portion where the high frequency component of the unnecessary current has conventionally flowed, so that the high frequency component of the unnecessary current is effectively attenuated, and the unnecessary electromagnetic field from the shield layer is reduced. Occurrence can be suppressed.

  In FIG. 5A, examples of the material of the low-loss conductor layer 105 include metals having high conductivity such as copper, silver, aluminum, and gold, which are usually used as signal conductors and shield conductors, alloys thereof, A metal having a layered structure may be used. Further, as the material of the high loss conductor layer 104, a material having a lower conductivity than that of the low loss conductor layer 105 can be used. For example, tin, nickel, chromium, iron, bismuth, titanium, carbon, etc. Metals, metalloids, conductive polymers, semiconductor materials with high electrical conductivity, solder alloys, stainless steel, carbon steel, ferrite, and those obtained by layering these materials may also be used.

  As a means for forming a layered structure composed of the high-loss conductor layer 104 and the low-loss conductor layer 105, a high-loss conductor material may be plated on the surface of a single cylindrical conductor made of a low-loss conductor, A stranded wire layer composed of a plurality of cylindrical conductors made of a high-loss conductor material may be formed on the surface of a single cylindrical conductor, or a surface of a single cylindrical conductor made of a low-loss conductor. A metal foil made of a lossy conductor may be wound, or a stranded wire made of a plurality of cylindrical conductors made of a high-loss conductor outside the stranded wire layer made of a plurality of cylindrical conductors made of a low-loss conductor. A layer may be formed, a high-loss conductor may be plated outside a stranded wire layer made of a plurality of cylindrical conductors made of a low-loss conductor, or a plurality of cylindrical conductors made of a low-loss conductor A high-loss conductor on the outside of the stranded wire layer made of Metal foil that may be wound.

  Further, the signal conductors 106 and 107 may be constituted by a single conductor cylinder or conductor cylinder, or may be constituted by a stranded wire structure composed of a plurality of conductor cylinders or conductor cylinders in order to have flexibility. good. In FIG. 5 (a), the number of signal conductors is two. However, since the main point of the present invention is the structure of the shield conductor, the number of signal conductors may be two or more. Furthermore, the structure in the longitudinal direction corresponding to the cross-sectional view of FIG. 5A may be uniform, or may be a so-called twisted pair structure in which the arrangement of signal conductors is twisted.

Hereinafter, the function of the shielded pair cable according to the present embodiment will be described in detail for a frequency close to a direct current and a high frequency region. FIG. 5B illustrates the current distribution inside the conductor at a frequency near the direct current of the shielded pair cable of the present invention. Since the current 121 induced by the signal current and the unnecessary current 122 flow through the shield conductor, both are affected when the high loss conductor layer 104 is provided. However, since both currents penetrate deeply into the shield conductor at frequencies near DC, if the cross-sectional area of the high-loss conductor layer is α _H and that of the low-loss conductor layer is α _L The change in DC resistance due to the provision of the lossy conductor layer 104 is approximately (α _H + α _L ) / α _L times. Here, when the frequency at which the unwanted electromagnetic field is to be suppressed is in a sufficiently high frequency range, the corresponding skin thickness is small, so by appropriately setting the shield conductor thickness (α _H + α _L ) / α _L Can be made sufficiently close to 1 in view of the purpose of each application. Therefore, at frequencies near DC, the influence on the current 121 and unnecessary current 122 induced by the signal current due to the provision of the high loss conductor layer 104 can be sufficiently reduced.

On the other hand, FIG. 5C illustrates the current distribution inside the conductor at the high frequency, that is, the lower limit value ν _min of the frequency region where it is desired to suppress the generation of unwanted electromagnetic fields, in the shielded pair cable of the present invention. . At high frequencies, the current 141 induced with the signal current concentrates on the inner surface of the shield conductor. Therefore, if the thickness of the high loss conductor layer 104 is smaller than the thickness of the low loss conductor layer 105, the high loss conductor layer 104 There is no influence on the induced current 141 due to the provision of.

At high frequencies, the unnecessary current flows through the current path 144 on the outer surface of the shield conductor. However, since the current path 144 is formed by the high-loss conductor layer 104, the unnecessary current is rapidly attenuated in the transmission direction. In fact, it can hardly flow. When the electrical resistivity of the high loss conductor layer 104 is ρ _H and the electrical resistivity of the low loss conductor layer 105 is ρ _L , the attenuation rate of the high frequency component of the unnecessary current when the high loss conductor layer 104 is provided is high loss. It is approximately ρ _H / ρ _L times when there is no conductor layer. If a combination of materials such that ρ _H / ρ _L >> 1 is used, the current flowing through the portion (current path 144) provided with the high loss conductor layer is sufficiently small after propagating a sufficient distance. With the structure of the invention, it is possible to selectively remove high-frequency components of unnecessary current that cause unnecessary electromagnetic fields. Note that the above shows only one embodiment of the present invention, and does not limit the effective range of the present invention.

[Second Embodiment]
A cross-sectional view of the second embodiment of the present invention is shown in FIG. FIG. 7A is a cross-sectional view of a coaxial cable configured as an example of the present invention. FIG. 6A is a cross-sectional view of a conventional coaxial cable compared with FIG. 7A.

  In FIG. 6A showing a coaxial cable according to the prior art, 201 is a surrounding medium, 202 is an outer conductor, 203 is a dielectric, and 206 is an inner conductor. In a coaxial cable, a signal current flows through an inner conductor and an outer conductor, and at the same time, the outer conductor also serves as a shield conductor.

  FIG. 6B illustrates the current distribution inside the conductor at a frequency in the vicinity of the direct current of the coaxial cable of the prior art. The signal current 223 flows substantially uniformly in the cross section of the inner conductor 206 in accordance with the general rule that “DC current flows through a path that minimizes electrical resistance”. The current 221 is a signal current that flows through the outer conductor, and is a return current for the forward current that flows through the inner conductor.

  The current 222 represents an unnecessary current mainly generated in the transmission-side electronic circuit or in the connection portion between the transmission-side electronic circuit and the external conductor. The signal current 221 flowing through the outer conductor flows substantially uniformly inside the outer conductor in accordance with the general rule that “DC current flows through a path that minimizes electrical resistance”. The unnecessary current 222 also penetrates deeply into the outer conductor at a frequency near DC. For this reason, at the frequency near the direct current, the signal current 221 and the unnecessary current 222 flow through the outer conductor in a spatially overlapping manner. The signal current 221 and the unnecessary current 222 may be called a normal mode current and a common mode current of the coaxial cable, respectively.

FIG. 6C illustrates the current distribution inside the conductor at a high frequency for the coaxial cable of the prior art. The signal current 243 of the inner conductor is concentrated on the surface of the inner conductor 206 due to the skin effect. The current inside the outer conductor is also concentrated in a region having a thickness of about the skin depth δ (ν _min ) on the surface of the outer conductor due to the skin effect. Since the signal current 241 flowing through the outer conductor is electrically coupled to the signal current 243 of the inner conductor, it is concentrated on the inner surface of the outer conductor. On the other hand, the unnecessary current 242 is concentrated on the outer surface of the outer conductor according to the general rule that “the high-frequency current flows through a path that minimizes the impedance”.

  FIG. 7A is a cross-sectional view of a coaxial cable configured as an embodiment of the present invention, in which 204 represents a high-loss conductor layer and 205 represents a low-loss conductor layer. In the present embodiment, the high loss conductor layer 204 is provided in the portion where the high frequency component of the unnecessary current has conventionally flowed, thereby effectively attenuating the high frequency component of the unnecessary current and reducing the unnecessary electromagnetic field from the external conductor. Occurrence can be suppressed.

  In FIG. 7A, the material of the low-loss conductor layer 205 is, for example, a metal having a high conductivity such as copper, silver, aluminum, or gold, which is usually used as a signal conductor or an external conductor, an alloy thereof, A metal having a layered structure may be used. Further, as the material of the high loss conductor layer 204, a material having a lower conductivity than that of the low loss conductor layer 205 can be used. For example, tin, nickel, chromium, iron, bismuth, titanium, carbon, etc. Metals, metalloids, conductive polymers, semiconductor materials with high electrical conductivity, solder alloys, stainless steel, carbon steel, ferrite, and those obtained by layering these materials may also be used.

  As a means for forming a layered structure composed of the high-loss conductor layer 204 and the low-loss conductor layer 205, a high-loss conductor material may be plated on the surface of a single cylindrical conductor made of a low-loss conductor. A stranded wire layer composed of a plurality of cylindrical conductors made of a high-loss conductor material may be formed on the surface of a single cylindrical conductor, or a surface of a single cylindrical conductor made of a low-loss conductor. A metal foil made of a lossy conductor may be wound, or a stranded wire made of a plurality of cylindrical conductors made of a high-loss conductor outside the stranded wire layer made of a plurality of cylindrical conductors made of a low-loss conductor. A layer may be formed, a high-loss conductor may be plated outside a stranded wire layer made of a plurality of cylindrical conductors made of a low-loss conductor, or a plurality of cylindrical conductors made of a low-loss conductor A high-loss conductor on the outside of the stranded wire layer made of Metal foil that may be wound.

  Further, the internal conductor 206 may be constituted by a single conductor column or conductor cylinder, or may be constituted by a stranded wire structure composed of a plurality of conductor columns or conductor cylinders in order to have flexibility. In FIG. 7 (a), the number of signal conductors is one. However, since the main point of the present invention is the structure of the outer conductor, the number of the inner conductors serving as the forward conductors of the signal current is one or more. good.

  Furthermore, the structure in the longitudinal direction corresponding to the cross-sectional view of FIG. 7A may be uniform, or may be a so-called twisted pair structure in which the arrangement of signal conductors is twisted.

  Hereinafter, the function of the coaxial cable of the present embodiment will be described in detail by dividing it into a frequency close to DC and a high frequency region.

FIG. 7B illustrates the current distribution inside the conductor at a frequency near the direct current of the coaxial cable of the present invention. Since the signal current 221 and the unnecessary current 222 flow in the external conductor, both are affected when the high-loss conductor layer 204 is provided. However, since both currents penetrate deeply into the outer conductor at frequencies near DC, if the cross-sectional areas of the high loss conductor layer and the low loss conductor layer are α _H and α _L , the high loss conductor layer The change in DC resistance due to the provision of 204 is approximately (α _H + α _L ) / α _L times. Here, if the frequency at which the unwanted electromagnetic field is to be suppressed is in a sufficiently high frequency region, the corresponding skin thickness is small, so by appropriately setting the thickness of the outer conductor (α _H + α _L ) / It is possible to make α _L a value close to 1 sufficiently for the purpose of each application. Therefore, the influence on the signal current 221 and the unnecessary current 222 due to the provision of the high-loss conductor layer 204 can be sufficiently reduced at frequencies near DC.

On the other hand, FIG. 7C illustrates the current distribution inside the conductor at the lower limit value ν _min of the high frequency, that is, the frequency region where it is desired to suppress the generation of unwanted electromagnetic fields, in the coaxial cable of the present invention.

  At high frequencies, the signal current 241 flowing through the outer conductor is concentrated on the inner surface of the outer conductor. Therefore, if the thickness of the high loss conductor layer 204 is smaller than the thickness of the low loss conductor layer 205, the high loss conductor layer 204 is provided. Therefore, there is no influence on the signal current 241. At high frequencies, unnecessary currents must flow through the current path 244 on the outer surface of the outer conductor. However, since the current path 244 is formed by the high-loss conductor layer 204, the unnecessary current is rapidly attenuated in the transmission direction. In fact, it can hardly flow.

When the electrical resistivity of the high-loss conductor layer 204 and the low-loss conductor layer 205 is ρ _H and ρ _L , the high-frequency component attenuation rate of the unnecessary current when the high-loss conductor layer 204 is provided is not that of the high-loss conductor layer. Ρ _H / ρ _L times that of the case. If a combination of materials such that ρ _H / ρ _L >> 1 is used, the unnecessary current flowing through the current path 244 on the outer surface of the outer conductor is sufficiently small after propagating a sufficient distance. Depending on the structure, it is possible to selectively remove high-frequency components of unnecessary current that cause unnecessary electromagnetic fields. Note that the above shows only one embodiment of the present invention, and does not limit the effective range of the present invention.

[Third embodiment]
A sectional view of the third embodiment of the present invention is shown in FIG. FIG. 9A is a cross-sectional view of a differential strip line formed on a printed wiring board as an example of the present invention. FIG. 8A is a cross-sectional view of a printed wiring board according to the prior art, compared with FIG. 9A.

  8A showing a printed wiring board according to the prior art, 301 is a surrounding medium, 302 is a resist, 303 is a ground conductor, 306 is a dielectric, 311 and 312 are signal conductors, and 313 is a surrounding signal conductor. It is a wiring pattern other than. In the differential strip line on the printed circuit board, the ground conductor arranged in the vicinity of the signal conductors 311 and 312 prevents the unnecessary electromagnetic field from leaking downward, and generates an electromagnetic field having a sign opposite to that of the signal conductor. Thus, it functions as a shield layer for weakening unnecessary electromagnetic fields.

  FIG. 8B illustrates the current distribution inside the conductor at a frequency in the vicinity of a direct current for a printed wiring board according to the prior art. The signal current 323 flows substantially uniformly through the cross sections of the signal conductors 311 and 312 in accordance with the general rule that “DC current flows through a path that minimizes electrical resistance”. The current 321 is a current induced in the ground conductor by the signal current 323 flowing through the signal conductors 311 and 312 of the differential strip line. The current 322 is mainly inside the transmission-side electronic circuit or the electronic circuit. It represents an unnecessary current generated at the connection portion of the printed wiring board. The induced current 321 in the ground conductor has a non-uniform distribution in the lateral direction depending on the phase relationship in the pair of signal currents 323 corresponding to the electric field distribution of the differential strip line, but at frequencies near DC. Since the skin depth is large, it can penetrate deeply into the ground conductor in the depth direction. Further, the unnecessary current 322 also penetrates deeply into the ground conductor at a frequency near DC. For this reason, at the frequency near DC, the above-described induced current 321 and unnecessary current 322 flow in the ground conductor in a spatially overlapping manner.

FIG. 8C illustrates the current distribution inside the conductor at a high frequency of the printed circuit board according to the prior art. The signal current 343 is concentrated on the lower surfaces of the signal conductors 311 and 312, particularly the corner portion, by the skin effect and the proximity effect. In addition, two types of currents flowing through the ground conductor are also concentrated in a region having a thickness of about the skin depth δ (ν _min ) on the surface of the ground conductor due to the skin effect. Of the two types of current, the current 341 induced by the signal current has a non-uniform spatial distribution in the lateral direction according to the electric field distribution of the differential strip line, and shields the electric field created by the charge distribution on the signal conductor. Thus, the ground conductor 303 is concentrated on the surface near the signal conductors 311 and 312. On the other hand, the unnecessary current 342 is concentrated on the surface of the ground conductor 303 far from the signal conductors 311 and 312 in accordance with the general rule that “the high-frequency current flows through a path that minimizes the impedance”.

  FIG. 9A is a cross-sectional view of a differential strip line on a printed wiring board configured as an embodiment of the present invention, where 304 indicates a high-loss conductor layer and 305 indicates a low-loss conductor layer. In this embodiment, the high loss conductor layer 304 is provided in the portion where the high-frequency component of the unnecessary current has been flowing, so that the high-frequency component of the unnecessary current is effectively attenuated and the unnecessary electromagnetic field from the ground conductor is reduced. Occurrence can be suppressed.

  In FIG. 9A, as a material of the low-loss conductor layer 305, for example, in addition to copper that is usually used as a conductor material, a metal having a high conductivity such as silver, aluminum, and gold, an alloy thereof, A metal layered structure may be used. Further, as the material of the high loss conductor layer 304, a material having a lower conductivity than that of the low loss conductor layer 305 can be used. For example, tin, nickel, chromium, iron, bismuth, titanium, carbon, etc. Metals, metalloids, conductive polymers, semiconductor materials with high electrical conductivity, solder alloys, stainless steel, carbon steel, ferrite, and those obtained by layering these materials may also be used. As a material of the dielectric 306, a material used for a normal rigid printed wiring board or a flexible printed wiring board can be used as it is. Examples include glass epoxy resin, Teflon (registered trademark), alumina, sapphire, polyimide, liquid crystal polymer, and the like. Further, the resist 302 may be omitted.

  As a means for forming a layered structure composed of the high-loss conductor layer 304 and the low-loss conductor layer 305, a high-loss conductor material may be plated on the surface of the low-loss conductor. FIG. 9A shows an example of a differential strip line. However, since the main point of the present invention is the structure of the ground conductor, the signal wiring may be a line other than the differential strip line. The arrangement may be more complicated such as a so-called GSSG arrangement, and the line structure may be a coplanar line other than a strip line. FIG. 9A shows an example of a two-layer printed wiring board composed of a single signal layer and a single ground layer. However, in the multilayer printed wiring board, the signal wiring of the ground wiring layer adjacent to the signal wiring layer is also shown. It is obvious that the effect of the present invention can be obtained by providing a high-loss conductor layer on the surface far from the layer.

  Hereinafter, the function of the printed wiring board of the present embodiment will be described in detail by dividing it into a frequency close to DC and a high frequency region.

FIG. 9B illustrates the current distribution inside the conductor at a frequency near the direct current of the printed wiring board of the present invention. Since a current 321 and an unnecessary current 322 induced along with a signal current flow through the ground conductor, both are affected when the high-loss conductor layer 304 is provided. However, since both currents penetrate deeply into the ground conductor at frequencies near DC, if the cross-sectional area of the high-loss conductor layer is α _H and the cross-sectional area α _L of the low-loss conductor layer is high loss The change in DC resistance due to the provision of the conductor layer 304 is approximately (α _H + α _L ) / α _L times. Here, if the frequency at which the unwanted electromagnetic field is to be suppressed is in a sufficiently high frequency region, the corresponding skin thickness is small, so by appropriately setting the ground conductor thickness (α _H + α _L ) / α _L Can be made sufficiently close to 1 for the purpose of each application. Therefore, the influence on the current 321 and unnecessary current 322 induced by the signal current due to the provision of the high-loss conductor layer 304 can be sufficiently reduced at frequencies near DC.

On the other hand, FIG. 9C illustrates the current distribution inside the conductor at the high frequency, that is, the lower limit value ν _min of the frequency region where it is desired to suppress the generation of unwanted electromagnetic fields, in the printed wiring board of the present invention. At high frequencies, the current 341 induced by the signal current concentrates on the surface of the ground conductor on the side close to the signal conductor, so the thickness of the high loss conductor layer 304 is larger than the thickness of the low loss conductor layer 305. If it is smaller, there is no influence on the induced current 341 due to the provision of the high-loss conductor layer 304. At high frequency, the unnecessary current flows through the surface (current path 344) far from the signal conductor of the ground conductor. However, since the current path 344 is formed by the high-loss conductor layer 304, the unnecessary current is It decays rapidly in the direction of transmission and can hardly flow in practice. Assuming that the electrical resistivity of the high loss conductor layer 304 and the low loss conductor layer 305 is ρ _H and ρ _L , the attenuation factor of the high-frequency component of the unnecessary current when the high loss conductor layer 304 is provided does not have the high loss conductor layer. Ρ _H / ρ _L times that of the case. If a combination of materials such that ρ _H / ρ _L >> 1 is used, the current flowing through the portion (current path 344) provided with the high loss conductor layer is sufficiently small after propagating a sufficient distance. With the structure of the invention, it is possible to selectively remove high-frequency components of unnecessary current that cause unnecessary electromagnetic fields. Note that the above shows only one embodiment of the present invention, and does not limit the effective range of the present invention.

[Fourth embodiment]
A cross-sectional view of the fourth embodiment of the present invention is shown in FIG. FIG. 11A is a sectional view of a differential microstrip line formed on a printed wiring board as an example of the present invention. FIG. 10A is a cross-sectional view of a printed wiring board according to the prior art, compared with FIG.

  In FIG. 10A showing the prior art, 301 is a surrounding medium, 302 is a resist, 303 is a ground conductor, 306 is a dielectric, 311 and 312 are signal conductors, and 313 is a wiring other than the surrounding signal conductors. It is a pattern. In the differential microstrip line on the printed circuit board, the ground conductors arranged close to the top and bottom of the signal conductors 311 and 312 prevent leakage of unnecessary electromagnetic fields, and further generate an electromagnetic field having a sign opposite to that of the signal conductors. Thus, it functions as a shield layer for weakening unnecessary electromagnetic fields.

  FIG. 11A is a cross-sectional view of a differential strip line on a printed wiring board configured as an embodiment of the present invention, where 304 indicates a high-loss conductor layer and 305 indicates a low-loss conductor layer. In this embodiment, the high loss conductor layer 304 is provided in the portion where the high-frequency component of the unnecessary current has been flowing, so that the high-frequency component of the unnecessary current is effectively attenuated and the unnecessary electromagnetic field from the shield layer is reduced. Occurrence can be suppressed. The example of the constituent material of FIG. 11A, the example of the constituent means of the layered structure, the structural modification example, and the like are the same as those of the third embodiment. Since the present embodiment is similar to the third embodiment, detailed description of functions and the like will be omitted.

[Fifth embodiment]
A cross-sectional view of the fifth embodiment of the present invention is shown in FIG. FIG. 13A is a cross-sectional view of a strip line formed on a printed wiring board as an example of the present invention. FIG. 12A is a cross-sectional view of a printed wiring board according to the prior art, compared with FIG.

  In FIG. 12A showing a printed wiring board according to the prior art, 401 is a surrounding medium, 402 is a resist, 403 is a ground conductor, 406 is a dielectric, 411 is a signal conductor, 413 is a signal conductor other than the surrounding signal conductor. It is a wiring pattern. In the strip line on the printed circuit board, the ground conductor disposed in the vicinity of the signal conductor 411 flows a return current corresponding to the forward current flowing through the signal conductor, and prevents leakage of unnecessary electromagnetic fields downward. Furthermore, it has a function as a shield layer for generating an electromagnetic field having a sign opposite to that of the signal conductor to weaken the unnecessary electromagnetic field.

  FIG. 12B illustrates the current distribution inside the conductor at a frequency near the direct current for a printed wiring board according to the prior art. The signal current 423 flows substantially uniformly in the cross section of the signal conductor 411 according to the general rule that “DC current flows through a path that minimizes electrical resistance”. A current 421 is a return current flowing through the ground conductor, and a current 422 represents an unnecessary current mainly generated in the transmission-side electronic circuit or in a connection portion between the electronic circuit and the printed wiring board. Although the return current 421 flowing through the ground conductor has a non-uniform distribution in the lateral direction, the skin depth is large at frequencies near DC, so that it penetrates deeply into the ground conductor in the depth direction. The unnecessary current 422 also penetrates deeply into the ground conductor at a frequency near DC. For this reason, at frequencies near DC, the return current 421 and the unnecessary current 422 flow in the ground conductor in a spatially overlapping manner.

FIG. 12C illustrates the current distribution inside the conductor at a high frequency of the printed circuit board according to the prior art. The signal current 443 is concentrated on the lower surface of the signal conductor 411, particularly the corner portion due to the skin effect. In addition, two types of currents flowing through the ground conductor are also concentrated in a region having a thickness of about the skin depth δ (ν _min ) on the surface of the ground conductor due to the skin effect. Of the two types of currents, the return current 441 is concentrated on the surface of the ground conductor 403 closer to the signal conductor 411 so as to shield the electric field created by the charge distribution on the signal conductor. On the other hand, the unnecessary current 442 is concentrated on the surface of the ground conductor 403 far from the signal conductor 411 according to the general rule that “the high-frequency current flows through a path that minimizes the impedance”.

  FIG. 13A is a cross-sectional view of a strip line on a printed wiring board configured as an embodiment of the present invention, where 404 indicates a high-loss conductor layer and 405 indicates a low-loss conductor layer. In this embodiment, the high-loss conductor layer 404 is provided in the portion where the high-frequency component of the unnecessary current has conventionally flowed, thereby effectively attenuating the high-frequency component of the unnecessary current and reducing the unnecessary electromagnetic field from the ground conductor. Occurrence can be suppressed.

  In FIG. 13 (a), as a material of the low-loss conductor layer 405, for example, in addition to copper that is usually used as a conductor material, a metal having a high conductivity such as silver, aluminum, and gold, an alloy thereof, A metal layered structure may be used. Further, as the material of the high loss conductor layer 404, a material having a lower conductivity than that of the low loss conductor layer 405 can be used. For example, tin, nickel, chromium, iron, bismuth, titanium, carbon, etc. Metals, metalloids, conductive polymers, semiconductor materials with high electrical conductivity, solder alloys, stainless steel, carbon steel, ferrite, and those obtained by layering these materials may also be used. As a material of the dielectric 406, a material used for a normal rigid printed wiring board or a flexible printed wiring board can be used as it is. Examples include glass epoxy resin, Teflon (registered trademark), alumina, sapphire, polyimide, liquid crystal polymer, and the like. Further, the resist 402 may be omitted.

  As a means for forming a layered structure including the high-loss conductor layer 404 and the low-loss conductor layer 405, a high-loss conductor material may be plated on the surface of the low-loss conductor. FIG. 13A shows an example of a strip line. However, since the main point of the present invention is the structure of the ground conductor, the signal wiring may be a line other than the strip line.

  FIG. 13A shows an example of a two-layer printed wiring board composed of a single signal layer and a single ground layer. However, in the multilayer printed wiring board, the signal wiring of the ground wiring layer adjacent to the signal wiring layer is also shown. It is obvious that the effect of the present invention can be obtained by providing a high-loss conductor layer on the surface far from the layer. Further, the effect described in the present invention can also be obtained by providing a high-loss conductor layer on the surface of the power supply layer adjacent to the signal wiring layer far from the signal wiring layer instead of the ground layer.

Hereinafter, the function of the printed wiring board of the present embodiment will be described in detail by dividing it into a frequency close to DC and a high frequency region. FIG. 13B illustrates the current distribution inside the conductor at a frequency near the direct current of the printed wiring board of the present invention. Since the return current 421 and the unnecessary current 422 flow through the ground conductor, the provision of the high-loss conductor layer 404 affects both. However, since both currents penetrate deeply into the ground conductor at frequencies near DC, if the cross-sectional areas of the high loss conductor layer and the low loss conductor layer are α _H and α _L , the high loss conductor layer The change in DC resistance due to the provision of 404 is approximately (α _H + α _L ) / α _L times. Here, if the frequency at which the unwanted electromagnetic field is to be suppressed is in a sufficiently high frequency region, the corresponding skin thickness is small, so by appropriately setting the ground conductor thickness (α _H + α _L ) / α _L Can be made sufficiently close to 1 for the purpose of each application. Therefore, the influence on the return current 421 and the unnecessary current 422 due to the provision of the high-loss conductor layer 404 can be sufficiently reduced at frequencies near DC.

On the other hand, FIG. 13C illustrates the current distribution inside the conductor at the high frequency, that is, the lower limit value ν _min of the frequency region where it is desired to suppress the generation of unwanted electromagnetic fields, in the printed wiring board of the present invention. At high frequencies, the return current 441 concentrates on the surface of the ground conductor on the side closer to the signal conductor. Therefore, if the thickness of the high loss conductor layer 404 is smaller than the thickness of the low loss conductor layer 405, the high loss conductor layer There is no influence on the return current 341 due to the provision of 404. At high frequency, the unnecessary current flows only on the surface 444 of the ground conductor far from the signal conductor. However, since the current path 444 is formed by the high-loss conductor layer 404, the unnecessary current is rapidly transmitted in the transmission direction. In actuality, it can hardly flow.

If the electrical resistivity of the high-loss conductor layer 404 and the low-loss conductor layer 405 is ρ _H and ρ _L , the high-frequency component attenuation rate of the unnecessary current when the high-loss conductor layer 404 is provided is not the high-loss conductor layer. Ρ _H / ρ _L times that of the case. If a combination of materials such that ρ _H / ρ _L >> 1 is used, the current flowing through the portion 444 provided with the high-loss conductor layer is sufficiently small after propagating a sufficient distance. Therefore, it is possible to selectively remove the high-frequency component of the unnecessary current that causes the unnecessary electromagnetic field. Note that the above shows only one embodiment of the present invention, and does not limit the effective range of the present invention.

[Sixth embodiment]
A sectional view of the sixth embodiment of the present invention is shown in FIG. FIG. 15A is a cross-sectional view of a microstrip line formed on a printed wiring board as an example of the present invention. FIG. 14A is a cross-sectional view of a printed wiring board according to the prior art, compared with FIG.

  In FIG. 14A showing the prior art, 401 is a surrounding medium, 402 is a resist, 403 is a ground conductor, 406 is a dielectric, 411 is a signal conductor, and 413 is a wiring pattern other than the surrounding signal conductor. is there. In the microstrip line on the printed wiring board, the ground conductor 403 disposed close to the top and bottom of the signal conductor 411 prevents leakage of unnecessary electromagnetic fields, and further generates an electromagnetic field having a sign opposite to that of the signal conductors. It functions as a shield layer to weaken the electromagnetic field.

  FIG. 15A is a cross-sectional view of a strip line on a printed wiring board configured as an embodiment of the present invention, where 404 indicates a high-loss conductor layer and 405 indicates a low-loss conductor layer. In this embodiment, the high-loss conductor layer 404 is provided in the portion where the high-frequency component of the unnecessary current has conventionally flowed, so that the high-frequency component of the unnecessary current is effectively attenuated, and the unnecessary electromagnetic field from the shield layer is reduced. Occurrence can be suppressed. The example of the constituent material in FIG. 15A, the example of the constituent means of the layered structure, the structural modification, and the like are the same as in the case of the fifth embodiment. Since the present embodiment is similar to the fifth embodiment, detailed description of functions and the like will be omitted.

[Seventh embodiment]
A sectional view of the seventh embodiment of the present invention is shown in FIG. FIG. 17A is a cross-sectional view of a shielded flexible flat cable configured as an example of the present invention. FIG. 16 (a) is a cross-sectional view of a shielded flexible flat cable according to the prior art, compared with FIG. 17 (a).

  In FIG. 16A showing the prior art, 501 is a surrounding medium, 503 is a shield conductor, 503 is a dielectric, 511 is a signal conductor, and 513 is a wiring pattern other than the surrounding signal conductor. In the shielded flexible flat cable, the shield conductors 502 arranged close to the top and bottom of the signal conductor 511 function as a shield layer for preventing leakage of unnecessary electromagnetic fields.

  FIG. 17A is a cross-sectional view of a shielded flexible flat cable configured as an embodiment of the present invention, in which 504 represents a high-loss conductor layer and 505 represents a low-loss conductor layer. In the present embodiment, the high loss conductor layer 504 is provided in the portion where the high-frequency component of the unnecessary current has conventionally flowed, so that the high-frequency component of the unnecessary current is effectively attenuated, and the unnecessary electromagnetic field from the shield layer is reduced. Occurrence can be suppressed. The example of the constituent material in FIG. 17A, the example of the constituent means of the layered structure, the structural modification example, and the like are the same as in the case of the fifth embodiment. Since the present embodiment is similar to the third to sixth embodiments described above, detailed description of functions and the like will be omitted.

According to the first to seventh embodiments described above, it is possible to effectively attenuate and remove unnecessary high-frequency current flowing through the shield conductor in various shielded transmission lines through which electric signals including high-frequency components flow. . Further, it is possible to reduce the generation amount of the high-frequency unnecessary electromagnetic field generated from the transmission line portion by a low-cost means without significantly affecting the transmission characteristics.

The basis for the optimum condition will be described in detail below. As a typical example of a transmission line with a shield, FIG. 19 shows an example in which the spatial distribution of current inside an outer conductor serving as a shield conductor is calculated for the coaxial cable shown in FIG. In the calculation, the conductivity of the outer conductor is 5.8 × 10 ⁶ [S / m], the dielectric constant of the dielectric is 2.1, the inner radius of the outer conductor is A = 0.0655 mm, and the outer radius is B = 0.0735 mm. Since it is already clear from the above description that the method of the present invention is effective for a very general transmission line, the value of the micro coaxial cable was used as an extreme case in selecting the parameters.

  FIG. 19A shows the current distribution inside the outer conductor (shield conductor) when the frequency is 50 Hz. In this case, since the frequency is low and the skin depth is large, the signal current and the unnecessary current are not spatially separated inside the shield conductor.

  On the other hand, FIG. 19B shows a current distribution inside the outer conductor (shield conductor) when the frequency is 10 GHz. In this case, since the frequency is large, the signal current and the unnecessary current are clearly separated spatially even for a transmission line having an extremely thin outer conductor (shield conductor) such as a micro coaxial cable. In FIG. 19B, the signal current is concentrated on the side closer to the internal conductor (signal conductor), and the unnecessary current is concentrated on the side far from the internal conductor (signal conductor). The skin depth in the case of 10 GHz is about 0.7 μm. In addition, what was written here as the signal current and unnecessary current of the outer conductor may be called a normal mode current and a common mode current of the coaxial cable in common usage.

  In the configuration of the present invention, the thickness of the high loss material can take a wide range of values, but the thickness of the high loss material suppresses unnecessary electromagnetic fields in order to efficiently attenuate unnecessary current on the shield conductor. It is necessary to make it larger than the skin depth at the lowest frequency where the effect is desired. Also, if the thickness of the high-loss material is larger than the thickness of the low-loss material, signal transmission characteristics such as electrical resistance at low frequencies will be affected, so the thickness of the high-loss material should be smaller than the thickness of the low-loss material. It is.

  In addition, in the high-frequency transmission line, there is an example of Patent Document 1 described above in which the shield layer is configured by a plurality of conductors having different conductivities. However, since the problem to be solved is different from the present invention, the parameters used are The area is different. In Patent Document 1, according to the description of the patent specification, 99% or more of the shield layer needs to be composed of a high-loss material in order to obtain the desired effect. Since it is related to the case of 50% or less, the target parameter area is different from Patent Document 1.

  When the shielded transmission line of the present invention is used in a device or system in which an electrical signal containing a high-frequency component flows, the amount of unnecessary electromagnetic fields generated can be reduced as compared with the case where a conventional shielded transmission line is used. Examples of application systems include printed wiring boards and inter-board connection cables used in information equipment such as computers, mobile phones, and PDAs, and printed wiring boards and boards used in video equipment such as televisions and video cameras. Connection cables, printed wiring boards and inter-board connection cables used in automobiles, airplanes and in-vehicle equipment, metal transceiver cables used for communication between housings and buildings, printed wiring boards and boards used in medical equipment There are connection cables between cables and I / O cables to sensors that output weak electrical signals.

  In addition, when the shielded transmission line of the present invention is used, the common mode current generated in the transmission-side electronic circuit or the connection part between the electronic circuit and the transmission line can be selectively attenuated, so that the transmission characteristics can be improved. Can be used. For this purpose, in particular, it can be used for a power feeding cable to a wireless antenna or an input / output cable to a sensor that outputs a weak electric signal.

It is explanatory drawing about the unnecessary electromagnetic field generation mechanism from the transmission line which does not have a shield layer. FIG. 2A is an explanatory diagram of an unnecessary electromagnetic field generation mechanism from a shielded transmission line according to the prior art, and FIG. 2B is a cross-sectional view of the shielded transmission line according to the prior art. c) is an example of a cross-sectional view of the shielded transmission line of the present invention. FIG. 3A is an explanatory diagram of an unnecessary electromagnetic field generation mechanism from another shielded transmission line according to the prior art, and FIG. 3B is a cross-sectional view of another shielded transmission line according to the prior art. FIG. 3C is an example of a cross-sectional view of another shielded transmission line of the present invention. FIG. 4A is a cross-sectional view of a shielded pair cable according to the prior art, and FIG. 4B illustrates a current distribution inside the conductor at a frequency near the direct current of the shielded pair cable according to the prior art. FIG. 4C illustrates a current distribution inside the conductor at a high frequency of a shielded pair cable according to the prior art. FIG. 5A is a cross-sectional view of a shielded pair cable according to the first embodiment of the present invention, and FIG. 5B is a frequency around a direct current of the shielded pair cable according to the first embodiment of the present invention. FIG. 5C illustrates the current distribution inside the conductor at high frequency (ν _min ) of the shielded pair cable according to the first embodiment of the present invention. . 6A is a cross-sectional view of a conventional coaxial cable, and FIG. 6B illustrates a current distribution inside the conductor at a frequency near the direct current of the coaxial cable according to the prior art. c) illustrates the current distribution inside the conductor at the high frequency of the coaxial cable according to the prior art. FIG. 7A is a cross-sectional view of the coaxial cable according to the second embodiment of the present invention, and FIG. 7B is a diagram showing the inside of the conductor at a frequency near the direct current of the coaxial cable according to the second embodiment of the present invention. FIG. 7C shows the current distribution inside the conductor at the high frequency (ν _min ) of the coaxial cable according to the second embodiment of the present invention. FIG. 8A is a cross-sectional view of a printed circuit board according to the prior art, and FIG. 8B illustrates a current distribution inside the conductor at a frequency near the direct current of the printed circuit board according to the prior art. FIG. 8C illustrates the current distribution inside the conductor at high frequency of the printed circuit board according to the prior art. FIG. 9A is a cross-sectional view of a printed wiring board according to the third embodiment of the present invention, and FIG. 9B is a conductor at a frequency near the direct current of the printed wiring board according to the third embodiment of the present invention. FIG. 9C illustrates the current distribution inside the conductor at a high frequency of the printed wiring board according to the third embodiment of the present invention. 10A is a cross-sectional view of a printed wiring board according to the prior art, and FIG. 10B illustrates a current distribution inside the conductor at a frequency near the direct current of the printed wiring board according to the prior art. 10 (c) shows the current distribution inside the conductor at a high frequency of the printed wiring board according to the prior art. FIG. 11A is a cross-sectional view of a printed wiring board according to the fourth embodiment of the present invention, and FIG. 11B is a conductor at a frequency near the direct current of the printed wiring board according to the fourth embodiment of the present invention. FIG. 11C illustrates the current distribution inside the conductor at a high frequency of the printed wiring board according to the fourth embodiment of the present invention. 12A is a cross-sectional view of a printed circuit board according to the prior art, and FIG. 12B illustrates a current distribution inside the conductor at a frequency near the direct current of the printed circuit board according to the prior art. 12 (c) illustrates the current distribution inside the conductor at a high frequency of the printed circuit board according to the prior art. FIG. 13A is a cross-sectional view of a printed wiring board according to the fifth embodiment of the present invention, and FIG. 13B is a conductor at a frequency near the direct current of the printed wiring board according to the fifth embodiment of the present invention. FIG. 13C illustrates the current distribution inside the conductor at a high frequency of the printed wiring board according to the fifth embodiment of the present invention. FIG. 14A is a cross-sectional view of a printed wiring board according to the prior art, and FIG. 14B illustrates a current distribution inside the conductor at a frequency near the direct current of the printed wiring board according to the prior art. 14 (c) shows the current distribution inside the conductor at a high frequency of the printed circuit board according to the prior art. FIG. 15A is a cross-sectional view of a printed wiring board according to the sixth embodiment of the present invention, and FIG. 15B is a conductor at a frequency near the direct current of the printed wiring board according to the sixth embodiment of the present invention. FIG. 15C illustrates the current distribution inside the conductor at a high frequency of the printed wiring board according to the sixth embodiment of the present invention. 16A is a cross-sectional view of a printed wiring board according to the prior art, and FIG. 16B illustrates a current distribution inside the conductor at a frequency near the direct current of the printed wiring board according to the prior art. 16 (c) illustrates the current distribution inside the conductor at a high frequency of the printed circuit board according to the prior art. FIG. 17A is a cross-sectional view of a printed wiring board according to the seventh embodiment of the present invention, and FIG. 17B is a conductor at a frequency near the direct current of the printed wiring board according to the seventh embodiment of the present invention. FIG. 17C illustrates the current distribution inside the conductor at a high frequency of the printed wiring board according to the seventh embodiment of the present invention. As a calculation model for calculating the spatial distribution of unnecessary current on the shield conductor, a coaxial cable according to the prior art is illustrated. FIG. 19A illustrates the spatial distribution of the signal current and unnecessary current on the shield conductor when a 50 Hz electrical signal is passed, and FIG. 19B shows the shield when a 1 GHz electrical signal is passed. The spatial distribution of the signal current and the unnecessary current on the conductor is illustrated.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission side circuit 11 Signal source 12 Ground of transmission side circuit 13 Phase difference between forward path current and return current in transmission side circuit 14 Ground voltage of signal source 2 Transmission line 21 Conductor constituting transmission line 22 From conductor constituting transmission line Unwanted electromagnetic field 23 Shield conductor 24 Shield conductor wire 25 Unnecessary current 26 flowing through the shield conductor Unnecessary electromagnetic field 27 generated from the shield conductor 27 Ground voltage 28 of the shield conductor to the ground of the transmission side circuit 28 Ground voltage 29 Part of the conductors that make up the transmission line (return conductor)
3 Reception side circuit 31 Signal load 32 Reception side circuit ground 33 Signal load ground voltage 40 Potential difference between transmission side circuit ground and reception side circuit ground 41 High-loss conductor layer 42 Low-loss conductor layer 101 Surrounding medium 102 Shield conductor 103 Dielectric 104 High loss conductor layer (part of shield conductor)
105 Low loss conductor layer (part of shield conductor)
106 Signal conductor (conductor constituting the transmission line)
107 Signal conductor (conductor constituting the transmission line)
121 Current on shield conductor induced by signal current (frequency near DC)
122 Unnecessary current on shield conductor (frequency near DC)
123 Signal current (frequency near DC)
124 High Loss Region 141 due to Providing High Loss Conductor Layer 141 Current on Shield Conductor Induced by Signal Current (Lower Frequency ν _{min in} Frequency Domain Where It _Is Wanted to Suppress Generation of Unwanted Electromagnetic Field)
142 Unnecessary current on the shield conductor (lower frequency limit ν _{min in the} frequency region where generation of unnecessary electromagnetic field is to be suppressed)
143 Signal current (lower frequency limit ν _{min in the} frequency region where generation of unwanted electromagnetic fields is to be suppressed)
144 Current path on the outer surface of the shield conductor (lower frequency limit ν _{min in the} frequency region where generation of unwanted electromagnetic fields is to be suppressed)
201 Surrounding medium 202 Shield conductor (= external conductor)
203 Dielectric 204 High loss conductor layer (a part of shield conductor (= outer conductor))
205 Low loss conductor layer (a part of shield conductor (= outer conductor))
206 Inner conductor (Conductor constituting the transmission line)
221 Signal current flowing through outer conductor (frequency near DC)
222 Unnecessary current flowing through the outer conductor (frequency near DC)
223 Signal current (frequency near DC)
224 High loss region 241 due to provision of high loss conductor layer 241 Signal current flowing through outer conductor (lower limit frequency ν _{min of} frequency region where generation of unnecessary electromagnetic field is to be suppressed)
242 Unnecessary current flowing in the outer conductor (lower frequency limit ν _{min in the} frequency region where generation of unnecessary electromagnetic field is to be suppressed)
243 Signal current (lower frequency limit ν _{min in the} frequency region where generation of unnecessary electromagnetic field is to be suppressed)
244 High loss region 301 by providing high loss conductor layer Surrounding medium 302 Resist 303 Ground conductor 304 High loss conductor layer (a part of shield conductor (= ground conductor))
305 Low loss conductor layer (a part of shield conductor (= ground conductor))
306 Dielectric 311 Signal conductor (conductor constituting transmission line)
312 Signal conductor (conductor constituting the transmission line)
313 Wiring pattern 321 around signal conductor other than signal conductor Current on ground conductor induced by signal current (frequency near DC)
322 Unwanted current on ground conductor (frequency near DC)
323 Signal current (frequency near DC)
324 High Loss Region 341 Due to Providing High Loss Conductor Layer Current on Ground Conductor Induced by Signal Current (Lower Limit Frequency ν _{Min in} Frequency Domain Where Suppressing Generation of Unnecessary Electromagnetic Field)
342 Unnecessary current on the ground conductor (lower frequency limit ν _{min in the} frequency region where generation of unnecessary electromagnetic fields is to be suppressed)
343 Signal current (lower frequency limit ν _{min in the} frequency region where generation of unnecessary electromagnetic field is desired to be suppressed)
344 High loss region 401 by providing high loss conductor layer 401 Surrounding medium 402 Resist 403 Ground conductor 404 High loss conductor layer (a part of shield conductor (= ground conductor))
405 Low loss conductor layer (a part of shield conductor (= ground conductor))
406 Dielectric 411 Signal conductor (conductor constituting transmission line)
413 Surrounding wiring pattern 421 other than signal conductor Return current (frequency near DC) on ground conductor
422 Unnecessary current on ground conductor (frequency near DC)
423 Signal current (frequency near DC)
424 High loss region 441 due to provision of high loss conductor layer 441 Return current on ground conductor (lower frequency limit ν _{min in} frequency region where generation of unnecessary electromagnetic field is to be suppressed)
442 Unnecessary current on the ground conductor (lower frequency limit ν _{min in the} frequency region where generation of unnecessary electromagnetic field is to be suppressed)
443 Signal current (lower frequency limit ν _{min in the} frequency region where generation of unnecessary electromagnetic field is to be suppressed)
444 High loss region 501 by providing high loss conductor layer 501 Surrounding medium 502 Shield conductor 503 Dielectric 504 High loss conductor layer (part of shield conductor)
505 Low loss conductor layer (part of shield conductor)
511 Signal conductor (conductor constituting the transmission line)
513 Surrounding wiring pattern 521 other than signal conductor Return current (frequency near DC) on shield conductor
522 Unwanted current on shield conductor (frequency near DC)
523 Signal current (frequency near DC)
524 High loss region 541 due to provision of high loss conductor layer Return current on shield conductor (lower limit frequency ν _{min of} frequency region where generation of unnecessary electromagnetic field is to be suppressed)
542 Unnecessary current on the shield conductor (lower frequency limit ν _{min in the} frequency region where generation of unnecessary electromagnetic field is to be suppressed)
543 Signal current (lower frequency limit ν _{min in the} frequency region where generation of unnecessary electromagnetic field is to be suppressed)
544 High loss area by providing high loss conductor layer

Claims (15)

One or more conductor lines provided to electrically connect the input side and output side of the transmission line, and unnecessary electromagnetic waves generated from the conductor line while electrically connecting the input side and output side of the transmission line In a shielded transmission line constituted by one or more shield conductor lines for shielding a field, and an insulator for holding the conductor lines and the shield conductor lines and electrically insulating each other,
The shield conductor wire is composed of two or more kinds of conductor materials having different conductivity, and a low loss conductor material is provided on the side of the shield conductor wire close to the conductor wire, and a high loss conductor material is provided on the side far from the conductor wire. A shielded transmission line characterized by being arranged. Two or more conductor wires provided to electrically connect the input side and output side of the transmission line, an insulator for holding the conductor wires and electrically insulating each other, and generated from the conductor wires In a shielded transmission line constituted by a shield conductor for shielding unnecessary electromagnetic fields to be
The shield conductor is composed of two or more kinds of conductor materials having different electrical conductivity, and a low loss conductor material is disposed on the side of the shield conductor close to the conductor line, and a high loss conductor material is disposed on the side far from the conductor line. And the thickness of the said high loss conductor material was made smaller than the thickness of the said low loss material, The transmission line with a shield characterized by the above-mentioned. One or more conductor lines provided to electrically connect the input side and output side of the transmission line, and unnecessary electromagnetic waves generated from the conductor line while electrically connecting the input side and output side of the transmission line In a shielded transmission line constituted by one or more shield conductor lines for shielding a field, and an insulator for holding the conductor lines and the shield conductor lines and electrically insulating each other,
The shield conductor wire is composed of two or more kinds of conductor materials having different conductivity, and a low loss conductor material is provided on the side of the shield conductor wire close to the conductor wire, and a high loss conductor material is provided on the side far from the conductor wire. A shielded transmission line, wherein the transmission line is arranged and the thickness of the high loss conductor material is smaller than the thickness of the low loss material. Two or more conductor wires provided to electrically connect the input side and output side of the transmission line, an insulator for holding the conductor wires and electrically insulating each other, and generated from the conductor wires In a shielded transmission line constituted by a shield conductor for shielding unnecessary electromagnetic fields to be
The shield conductor is composed of two or more kinds of conductor materials having different electrical conductivity, and a low loss conductor material is disposed on the side of the shield conductor close to the conductor line, and a high loss conductor material is disposed on the side far from the conductor line. And the thickness of the high-loss conductor material is smaller than the thickness of the low-loss material, and the thickness of the high-loss conductor material is a frequency region in which generation of unnecessary electromagnetic fields from the shielded transmission line is suppressed. A shielded transmission line characterized by being larger than the skin depth δ (ν _min ) at the lower limit value ν _min of. One or more conductor lines provided to electrically connect the input side and output side of the transmission line, and unnecessary electromagnetic waves generated from the conductor line while electrically connecting the input side and output side of the transmission line In a shielded transmission line constituted by one or more shield conductor lines for shielding a field, and an insulator for holding the conductor lines and the shield conductor lines and electrically insulating each other,
The shield conductor wire is composed of two or more kinds of conductor materials having different conductivity, and a low loss conductor material is provided on the side of the shield conductor wire close to the conductor wire, and a high loss conductor material is provided on the side far from the conductor wire. And to reduce the thickness of the high-loss conductor material smaller than the thickness of the low-loss material and suppress the generation of unnecessary electromagnetic fields from the shielded transmission line by reducing the thickness of the high-loss conductor material. A shielded transmission line characterized by being larger than the skin depth δ (ν _min ) at the lower limit value ν _min of the frequency domain.   A shielded multi-wire cable including a shielded pair cable and a shielded twisted pair cable, wherein the shield conductor according to claim 4 is used for a shield layer.   A coaxial cable using the shielded conductor wire according to claim 5 as an outer conductor.   A rigid printed circuit board and a flexible printed circuit board, wherein the shield conductor according to claim 4 is used as a ground wiring of a strip line.   A rigid printed circuit board and a flexible printed circuit board, wherein the shield conductor wire according to claim 5 is used as a ground wiring or a power wiring of a microstrip line.   A flexible flat cable, wherein the shield conductor according to claim 4 is used for a shield layer.   In the coaxial cable, wherein the outer conductor is constituted by a stranded wire layer formed by twisting a plurality of conductor wires, the outer conductor is constituted by two or more stranded wire layers, and inside the stranded wire layer The layer is made of a low-loss conductor material, the outer layer is made of a high-loss conductor material, and the thickness of the stranded wire layer made of the high-loss conductor material is more than the thickness of the stranded wire layer made of the low-loss conductor material. The coaxial cable is characterized by being made smaller. In the coaxial cable, wherein the outer conductor is constituted by a stranded wire layer formed by twisting a plurality of conductor wires, the outer conductor is constituted by two or more stranded wire layers, and inside the stranded wire layer. The layer is made of a low-loss conductor material, the outer layer is made of a high-loss conductor material, and the thickness of the stranded wire layer made of the high-loss conductor material is more than the thickness of the stranded wire layer made of the low-loss conductor material. And the thickness of the stranded wire layer composed of the high-loss conductor material, the skin depth δ (ν _min ) at the lower limit value ν _min of the frequency region where it is desired to suppress the generation of unwanted electromagnetic fields from the coaxial cable Coaxial cable characterized by being larger than.   In a semi-rigid coaxial cable composed of one conductor wire constituting the inner conductor, one hollow conductor wire constituting the outer conductor, and an insulator for holding and electrically insulating the inner conductor and the outer conductor, The outer conductor is composed of two or more kinds of conductor materials, a low-loss conductor material is disposed on the inner surface of the outer conductor, a high-loss conductor material is disposed on the outer surface, and the thickness of the high-loss conductor material is reduced. A semi-rigid coaxial cable characterized by being smaller than the thickness of the lossy material. In a semi-rigid coaxial cable composed of one conductor wire constituting the inner conductor, one hollow conductor wire constituting the outer conductor, and an insulator for holding and electrically insulating the inner conductor and the outer conductor,
The outer conductor is composed of two or more kinds of conductor materials, a low-loss conductor material is disposed on the inner surface of the outer conductor, a high-loss conductor material is disposed on the outer surface, and the thickness of the high-loss conductor material is reduced. The skin depth δ (ν _min ) at the lower limit value ν _min of the frequency region where the thickness of the lossy material is smaller and the thickness of the high loss conductor material is desired to suppress the generation of unwanted electromagnetic fields from the semi-rigid coaxial cable A semi-rigid coaxial cable that is larger than   The semi-rigid coaxial cable according to claim 14, wherein the outer conductor is formed by plating a high-loss conductor material on an outer surface of a hollow conductor wire made of a low-loss conductor material.

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