Patent Publication Number: US-8525614-B2

Title: Coupler

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     The present application relates to and claims priority from Japanese Patent Application Nos. 2009-272227 and 2009-272231, both filed on Nov. 30, 2009, the entire disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a directional coupler (hereinafter simply referred to as a “coupler”) that picks up part of an output signal, and particularly relates to a coupler formed by a thin-film formation process which is advantageous for achieving thinner products with smaller sizes. 
     2. Description of Related Art 
     Radio communication devices are constituted by various kinds of high-frequency components such as antennas, filters, RF switches, power amplifiers, couplers, baluns, etc. In general, a coupler is used for the purpose of picking up part of an output of a power amplifier and feeding it back to an input to the power amplifier so as to maintain and control a constant output gain of the power amplifier. 
     In recent years, there has been a demand for further thinner and smaller couplers to be used in mobile communication devices such as cellular phones and portable terminals as well as wireless LAN devices. For couplers responding to that demand, a stacked coupler is known, the stacked coupler having a layer of a main line and a layer of a secondary line arranged via an insulating layer, and electromagnetic coupling is generated between the layers (see Patent Document 1). In the stacked coupler, a plurality of vias is formed to ensure electric conductivity between the layers. In the coupler disclosed in Patent Document 1, the main line and the secondary line are each wired out to the opposite sides of the insulating layer through the vias. 
     Patent document 1: Japanese Unexamined Patent Publication No. 2003-069316 
     SUMMARY 
     However, there are limits to producing thinner and smaller couplers using the conventional coupler configuration where the main line and the secondary line are each wired out to the opposite sides of the insulating layer through the vias. 
     On the other hand, if the size of the coupler is simply reduced to obtain a thinner and smaller coupler, the lines, e.g., coils, constituting the coupler are inevitably shortened, which would decrease the coupling in the coupler. Furthermore, if the number of windings of the coil is increased to increase the coupling in the coupler, unnecessary coupling would increase as well between portions of the same line existing in the same layer, resulting in a problem of degraded directivity or isolation properties. 
     Accordingly, there has been a demand for couplers that are thinner and smaller in size and still satisfy the required various properties of the couplers. 
     The invention has been made in light of the above circumstances, and an object of the invention is to provide couplers that are thinner and smaller in size and still satisfy the required various properties of the couplers. 
     In order to solve the above-mentioned problems, a coupler according to an aspect of the invention has: a first line that includes a coiled main line and is constituted by separate portions arranged in different layers; a second line that includes a coiled secondary line arranged to be opposed to the main line via an insulating layer, the second line being constituted by separate portions arranged in different layers; a plurality of vias connecting the separate portions of the first line arranged in the different layers to each other and connecting the separate portions of the second line arranged in the different layers to each other; and a plurality of terminals each connected to an end of the first and second lines, wherein the vias include an extension via connected to the main line or the secondary line and extending through the insulating layer, and wherein the extension via wires out at least one of the first line and the second line to the same side of the insulating layer as the other one of the first line and the second line. 
     In the above configuration, since the via wires out at least one of the first line and the second line to the same side of the insulating layer as the other one of the first and the second lines, the first and second lines can share wiring layers in which the respective lines are to be formed. As a result, the number of layers in the coupler is reduced and this reduction of layers allows a thinner coupler, and such a thinner coupler has a reduced size. Since there is no need to reduce the lengths of the first and second lines in the coupler according to the invention, a thinner coupler with a reduced size can be obtained without decreasing the coupling in the coupler. 
     In the above configuration, the vias may include a via connected to an inner end of the main line and a via connected to an inner end of the secondary line, and all the terminals may be arranged in the periphery of the coiled main and secondary lines. By arranging the terminals in the periphery of the main and secondary lines, a certain distance can be ensured between the terminals and the vias connected to the inner ends of the main and secondary lines, and as a result, unnecessary coupling between the vias and the terminals can be suppressed. 
     The vias may include a prismatic via having corners in its cross-section (having a rectangular cross-section) parallel to the insulating layer, and the prismatic via may be arranged such that the corners face the terminals in the cross-section parallel to the insulating layer. As a result, the sides of the vias and the sides of the terminals are not parallel to one another, and thus, unnecessary coupling between the vias and the terminals can be suppressed. 
     The vias may include a cylindrical via having a circular portion in its cross-section (having a circular cross-section) parallel to the insulating layer. Since the cylindrical via has no side to be parallel to the sides of the other vias or the terminals, unnecessary coupling between the cylindrical via and the other vias or the terminals can be suppressed. 
     The terminals may include four terminals, and the vias may be arranged such that at least one of the vias is at the center of the four terminals. Since the via arranged at the center of the four terminals has a certain distance from all the four terminals, coupling between that via and the terminals can be effectively reduced. 
     In order to solve the above-mentioned problems, according to another aspect of the invention, provided is a coupler having: a first line including a main line and a first connecting wiring; and a second line including a secondary line and a second connecting wiring, wherein the main line and the secondary line are arranged in different layers via an insulating layer such that electromagnetic coupling is generated between the main line and the secondary line, and wherein at least one of the first connecting wiring and the second connecting wiring is arranged in the same layer as the first line or the second line such that electromagnetic coupling between the first line and the second line is generated in the same layer. 
     In the above configuration, since electromagnetic coupling between the first line and the second line is generated not only in different layers but also within the same layer, increased coupling can be obtained. Accordingly, the coupling in the coupler can be increased while suppressing degradation of directivity or isolation properties. As a result, thinner couplers with reduced sizes can be achieved while maintaining various properties of the couplers. 
     In the above, at least part of the first connecting wiring and at least part of the second line may be arranged adjacently to each other in the same layer. Also, at least part of the first connecting wiring and at least part of the secondary line may be arranged adjacently to each other in the same layer. Also, at least part of the second connecting wiring and at least part of the main line may be arranged adjacently to each other in the same layer. 
     It is preferable that portions of one wiring which intersect with each other in a plan view are arranged to be orthogonal to each other at the intersection. With this configuration, unnecessary coupling, such as coupling between portions of the first line or coupling between portions of the second line, can be avoided, and thus, degradation of directivity or isolation properties can be suppressed. 
     It is preferable that the above coupler further has a via connected to the main line or the secondary line and extending through the insulating layer, the via wiring out at least one the first line and the second line to the same side of the insulating layer as the other one of the first and second lines. In the above, the coupler of the invention may have: a first layer including at least the main line; a second layer including at least the secondary line; and a third layer including at least part of the first connecting wiring and/or the second connecting wiring. By wiring out, using the via, at least one of the first line and the second line to the same side of the insulating layer as the other one of the first and second lines, the first line and the second line can share wiring layers in which the respective lines are to be formed, and thus, the number of layers in the coupler can be reduced, which contributes to producing a thinner coupler. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an equivalent circuit diagram showing the configuration of a coupler according to an embodiment of the invention. 
         FIG. 2  is a vertical sectional view showing the configuration of a coupler according to an embodiment of the invention. 
         FIG. 3  is a horizontal sectional view of a wiring layer M 1  of a coupler  1 . 
         FIG. 4  is a horizontal sectional view of an insulating layer I 1  of the coupler  1 . 
         FIG. 5  is a horizontal sectional view of a wiring layer M 2  of the coupler  1 . 
         FIG. 6  is a horizontal sectional view of an insulating layer I 2  of the coupler  1 . 
         FIG. 7  is a horizontal sectional view of a wiring layer M 3  of the coupler  1 . 
         FIG. 8  is a horizontal sectional view of a passivation layer I 3  of the coupler  1 . 
         FIG. 9  is a plan view illustrating a wiring layout of the coupler  1 . 
         FIG. 10  is a horizontal sectional view of the insulating layer I 2 , showing a suitable arrangement of vias. 
         FIG. 11  is a horizontal sectional view of a wiring layer M 1  of a coupler  1 A. 
         FIG. 12  is a horizontal sectional view of an insulating layer I 1  of the coupler  1 A. 
         FIG. 13  is a horizontal sectional view of a wiring layer M 2  of the coupler  1 A. 
         FIG. 14  is a horizontal sectional view of an insulating layer I 2  of the coupler  1 A. 
         FIG. 15  is a horizontal sectional view of a wiring layer M 3  of the coupler  1 A. 
         FIG. 16  is a horizontal sectional view of a passivation layer I 3  of the coupler  1 A. 
         FIG. 17  is a plan view illustrating a wiring layout of the coupler  1 A. 
         FIG. 18  is a horizontal sectional view of a wiring layer M 1  of a coupler  1 B. 
         FIG. 19  is a horizontal sectional view of an insulating layer I 1  of the coupler  1 B. 
         FIG. 20  is a horizontal sectional view of a wiring layer M 2  of the coupler  16 . 
         FIG. 21  is a horizontal sectional view of an insulating layer I 2  of the coupler  1 B. 
         FIG. 22  is a horizontal sectional view of a wiring layer M 3  of the coupler  1 B. 
         FIG. 23  is a plan view illustrating a wiring layout of the coupler  1 B. 
         FIG. 24  is a horizontal sectional view of a wiring layer M 1  of a coupler  1 C. 
         FIG. 25  is a horizontal sectional view of an insulating layer I 1  of the coupler  1 C. 
         FIG. 26  is a horizontal sectional view of a wiring layer M 2  of the coupler  1 C. 
         FIG. 27  is a horizontal sectional view of an insulating layer I 2  of the coupler  1 C. 
         FIG. 28  is a horizontal sectional view of a wiring layer M 3  of the coupler  1 C. 
         FIG. 29  is a plan view illustrating a wiring layout of the coupler  1 C. 
         FIG. 30  is a horizontal sectional view of a wiring layer M 1  of a coupler  1 D. 
         FIG. 31  is a horizontal sectional view of an insulating layer I 1  of the coupler  1 D. 
         FIG. 32  is a horizontal sectional view of a wiring layer M 2  of the coupler  1 D. 
         FIG. 33  is a horizontal sectional view of an insulating layer I 2  of the coupler  1 D. 
         FIG. 34  is a horizontal sectional view of a wiring layer M 3  of the coupler  1 D. 
         FIG. 35  is a plan view illustrating a wiring layout of the coupler  10 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Embodiments of the invention will be described below with reference to the attached drawings. In the drawings, the same components are given the same reference numerals, and any repetitive description will be omitted. The positional relationship, such as top and bottom, left and right, etc., is as shown in the drawings unless otherwise specified. The dimensional ratios are not limited to those shown in the drawings. The below embodiments are just examples for describing the invention, and the invention is not limited to those embodiments. The invention can be modified in various ways without departing from the gist of the invention. 
       FIG. 1  is an equivalent circuit diagram showing the configuration of a coupler according to an embodiment of the invention. A coupler  1  has a first line L 1  and a second line L 2  which is electromagnetically coupled with the first line L 1 . In  FIG. 1 , a magnetic coupling M and capacitive couplings C 1  and C 2  are illustrated as the electromagnetic coupling between the first line L 1  and the second line L 2 . 
     In the coupler  1 , one end of the first line L 1  is connected to an input terminal T 11  and the other end of the first line L 1  is connected to an output terminal T 12 . Also, one end of the second line L 2  is connected to a coupling terminal T 21  and the other end of the second line L 2  is connected to an isolation terminal T 22 . The isolation terminal T 22  is fixed to a grounding potential G via resistance R. 
     The length of the lines L 1  and L 2  may be different according to the specification of the coupler  1 . For example, the length may be set so that the coupler  1  serves as a quarter-wavelength (λ/4) resonator circuit for signals to be transmitted. 
     Referring to  FIG. 1 , the basic operation of the coupler  1  will be described below. Signals are input to the input terminal T 11  and output from the output terminal T 12 . When a signal is input to the input terminal T 11 , a principal current IM flows through the first line L 1 . The principal current IM in the first line L 1  makes an induced current IL due to the magnetic coupling M flow through the second line L 2  in one direction, and also makes a displacement current IC due to the capacitive couplings C 1  and C 2  flow through the second line L 2  in the two opposite directions. The resulting current flowing in the second line L 2  will be the sum of the induced current IL due to the magnetic coupling M and the displacement current IC due to the capacitive couplings C 1  and C 2 , and as a result, the current having directivity corresponding to the direction of the induced current caused by the magnetic coupling will flow toward the coupling terminal T 21 . As described above, when a signal is input to the input terminal T 11  of the coupler and output from the output terminal T 12 , a signal corresponding to part of the above signal is output from the coupling terminal T 21 . 
     The above-described coupler  1  is used, for example, for an output monitor of a power amplifier (PA). In such use, the input terminal T 11  of the coupler  1  is connected to an output terminal of the power amplifier, and the coupling terminal T 21  of the coupler  1  is connected to an input terminal of the power amplifier via an AGC detection circuit. With this configuration, when a signal is output from the power amplifier and input to the input terminal T 11  of the coupler  1 , a signal corresponding to part of that signal is output from the coupling terminal T 21  of the coupler  1  and input to the power amplifier as a feedback signal through the AGC detection circuit. Thus, the power amplifier can maintain and control a constant output gain. 
     Next, the wiring configuration of the above-described coupler according to an embodiment of the invention will be described.  FIG. 2  is a vertical sectional view of the coupler  1 , schematically illustrating the wiring configuration of the coupler  1 . As shown in  FIG. 2 , a wiring layer M 1  is formed on an insulating substrate  100  which is formed of, for example, alumina, via an insulating layer  101  formed of, for example, a silicon nitride film. Also, a wiring layer M 2  is formed on the wiring layer M 1  via an insulating layer I 1 , a wiring layer M 3  is formed on the wiring layer M 2  via an insulating layer I 2 , and a passivation layer I 3  is formed on the wiring layer M 3 . The insulating layers I 1  and I 2  have vias formed therein so as to have the necessary connections between the wiring layers M 1 , M 2  and M 3 . In the peripheral portion of the coupler, the stacked wiring layers M 1 , M 2  and M 3  form terminals T 11 , T 12 , T 21  and  122 . The passivation layer I 3  is formed such that the terminals T 11 , T 12 , T 21  and T 22  are exposed, and a plating film  102  is formed on the surface of the terminals T 11 , T 12 , T 21  and T 22 . 
     For the insulating layers I 1  and I 2  and the passivation layer I 3 , for example, inorganic insulators such as silicon nitride, aluminum oxide and silicon dioxide may be used, and organic insulators such as polyimide and epoxy resin may be used as well. Also, for the wiring layers M 1 , M 2  and M 3 , for example, Cu, Ag, Pd, Ag—Pd, Ni, Au, etc., may be used. The wiring layers M 1 -M 3  may be formed, for example, by sputtering, deposition, printing, or photolithography. For the plating film  102 , for example, Ni/Au plating or Ni/Sn plating may be used. As described above, the coupler  1  is constituted by a thin-film multilayer configuration formed on the insulating substrate  100 . 
     Embodiment 1 
     Next, one example of the respective patterns of the wiring layers M 1 , M 2  and M 3  in a coupler of Embodiment 1 will be described in detail. In the below embodiment, coils are used for the main line and the secondary line which constitute the lines L 1  and L 2  respectively. 
       FIGS. 3-8  are horizontal sectional views schematically illustrating the respective layers M 1 -M 3  and I 1 -I 3  of the coupler  1 . As illustrated in  FIGS. 3-8 , the input terminal T 11 , the output terminal T 12 , the coupling terminal T 21 , and the isolation terminal T 22  are formed in all the wiring layers M 1 -M 3 , and the portions of the terminals T 11 , T 12 , T 21  and T 22  formed in one layer are electrically connected to the corresponding portions in a different layer. The following is a detailed explanation of the configuration of each layer. 
     Referring to  FIG. 3 , in the wiring layer M 1  formed on the insulating substrate  100  (via the insulating film  101 ), the coiled first line L 1  is formed. In the wiring layer M 1 , the outer end of the coiled first line L 1  is connected to the output terminal T 12  and the inner end of the first line L 1  is connected to a via P 11  (extension via). The via P 11  extends from the wiring layer M 1  to the wiring layer M 3  through the insulating layers I 1  and I 2 . The via P 11  is formed in a prism shape, having corners in its cross-section parallel to the substrate (such cross-section being parallel to the insulating layers as well). In the first line L 1  in the wiring layer M 1 , the portion that is opposed to the second line L 2  in the wiring layer M 2 , which will be explained later, serves as a main line L 11 . The main line indicates a portion of the first line L 1 , the portion creating electromagnetic coupling with the second line formed in a different layer. 
     Referring next to  FIG. 4 , in the insulating layer I 1  formed on the wiring layer M 1 , through holes Hill, HT 12 , HT 21  and H 122  are formed at portions corresponding to the respective terminals T 11 , T 12 , T 21  and T 22 . Also formed in the insulating layer I 1  is a through hole HP 11 , which is formed at a portion corresponding to the via P 11 . Herein, a through hole refers to an opening (hole) formed in an insulating layer, and a via refers to a conductor formed by putting metal into such a through hole. 
     Referring next to  FIG. 5 , in the wiring layer M 2  formed on the insulating layer I 1 , the coiled second line L 2  is formed. In the wiring layer M 2 , the outer end of the coiled second line L 2  is connected to the isolation terminal T 22 , and the inner end of the second line L 2  is connected to a via P 21 . The via P 21  extends from the wiring layer M 2  to the wiring layer M 3  through the insulating layer I 2 . A portion of the second line L 2  in the wiring layer M 2  is opposed to the first line L 1  in the wiring layer M 1 , and the opposed portion serves as a secondary line L 21 . The secondary line indicates a portion of the second line L 2 , the portion creating electromagnetic coupling with the first line L 1  formed in a different layer. Also, connecting wirings L 12  and L 22  are formed around (in the periphery of) the secondary line L 21 . The connecting wiring L 12  is a portion of the first line L 1 , and one end thereof is connected to the input terminal T 11  and the other end is connected to a via P 12 . The via P 12  extends through the insulating layer I 2  to the wiring layer M 3 . The connecting wiring L 22  is a portion of the second line L 2 , and one end thereof is connected to the coupling terminal T 21  and the other end is connected to a via P 22 . The via P 22  extends through the insulating layer I 2  to the wiring layer M 3 . The vias P 12 , P 21  and P 22  are, for example, cylindrical vias having a circular shape in a cross-section parallel to the substrate (such cross-section being parallel to the insulating layers as well). 
     Referring next to  FIG. 6 , in the insulating layer I 2  formed on the wiring layer M 2 , the through holes HT 11 , HT 12 , HT 21  and HT 22  are formed at portions corresponding to the respective terminals T 11 , T 12 , T 21  and T 22 . Through holes HP 11 , HP 12 , HP 21  and HP 22  are also formed in the insulating layer I 2  at portions corresponding to the vias P 11 , P 12 , P 21  and P 22 . 
     Referring next to  FIG. 7 , in the wiring layer M 3  formed on the insulating layer I 2 , connecting wirings L 13  and L 23  are formed. The connecting wiring L 13  is a portion of the first line L 1 , and one end thereof is connected to the via P 11  and the other end is connected to the via P 12 . The connecting wiring L 23  is a portion of the second line L 2 , and one end thereof is connected to the via P 21  and the other end is connected to the via P 22 . 
     Referring next to  FIG. 8 , the passivation layer I 3  is formed on the wiring layer M 3 . The passivation layer I 3  is formed at portions excluding four corners where the terminals T 11 , T 12 , T 21  and T 22  are formed. 
       FIG. 9  is a plan view showing the wiring layout of the coupler  1 . As shown in  FIG. 9 , the coupler  1  has: the first line L 1  including the main line L 11  and the connecting wirings L 12  and L 13  (first connecting wiring); and the second line L 2  including the secondary line L 21  and the connecting wirings L 22  and L 23  (second connecting wiring). As can be seen from  FIGS. 3 and 5 , the main line L 11  and the secondary line L 12  are arranged in different layers so that they overlap in a plan view, and accordingly, electromagnetic coupling is created between the different layers through the insulating layer I 1 . 
     In this embodiment, the via P 11  connected to the main line L 11  is formed to extend through the insulating layer I 1 . By forming the via P 11  to wire out the first line L 1  to the wiring layer M 2  where the second line L 2  is formed, the first line L 1  and the second line L 2  can share wiring layers in which the respective lines are to be formed. Consequently, the number of layers in the coupler can be reduced, and this reduction of layers allows a thinner coupler, resulting in a coupler with a reduced size. In this embodiment, since a thinner and smaller coupler can be achieved without reducing the length of the first line L 1  or the second line L 2 , such a coupler does not cause disadvantages such as decrease of coupling. In addition, since there is no need to reduce the thickness of the interlayer insulating layers, coupling between portions of the first line and coupling between portions of the second line can be suppressed and degradation of isolation properties can be suppressed as well. 
     In this embodiment, as shown in  FIG. 9 , the connecting wiring L 12  of the first line L 1  is located in the same layer as, and adjacently and parallel to, the secondary line L 21  of the second line L 2 . This is to ensure that electromagnetic coupling between the first line L 1  and the second line L 2  is generated in the same layer. In order to increase electromagnetic coupling, two wirings should be located, at least, adjacently, and preferably parallel, to each other. With this configuration, the coupling in the coupler can be increased without increasing the number of windings of the first line L 1  or the second line L 2 , and thus, the coupling in the coupler can be increased while suppressing degradation of directivity or isolation properties. As a result, thinner couplers with reduced sizes can be achieved while maintaining various properties of the couplers. 
     Also, in this embodiment, when portions of the same wiring intersect with each other in a plan view, the portions are arranged to be orthogonal to each other at the intersection. In other words, the intersecting portions of the first line, and the intersecting portions of the second line, are arranged to be orthogonal to each other. For example, in  FIG. 9 , at the intersection of the connecting wiring L 13  and the main line  11 , and at the intersection of the connecting wiring L 23  and the secondary line L 21 , the two wirings are arranged to be orthogonal to each other. Electromagnetic coupling between the wirings through which the same current flows is normally unnecessary, and by avoiding such unnecessary coupling, degradation of directivity or isolation properties can be suppressed. 
     In this embodiment, the first line L 1  is wired out, using the via P 11 , to the wiring layer M 2  where the second line L 2  is formed, and the first line L 1  and the second line L 2  can consequently share the wiring layers in which the respective lines are to be formed. Accordingly, the number of vias extending through the insulating layer is twice the number of vias in the conventional configurations where each line is wired out to the opposite sides, and thus, coupling between the vias and coupling between the vias and terminals should desirably be reduced to suppress degradation of isolation properties. A suitable shape and arrangement of the vias for reducing coupling between the vias and between the vias and the terminals will be described below. 
       FIG. 10  is a horizontal sectional view of the insulating layer I 2 , showing a suitable arrangement of the vias. The arrangement and shapes of the vias correspond to the arrangement and shapes of the through holes formed in the insulating layer I 2 , so the arrangement and shapes of the vias will be described referring to  FIG. 10 . 
     The four terminals T 11 , T 12 , T 21  and T 22  are formed in the four corners of the substrate. The four terminals extend in the stacking direction of the respective layers on the substrate, and this direction is the same as the extending direction of the via P 11  and the via P 21 . A prismatic via having corners in its cross-section parallel to the substrate surface is used for the via P 11 , and in this embodiment, the cross-sectional shape is a rectangle. Also, the via P 11  is arranged such that the corners of the via P 11  in a cross-section parallel to the insulating layers face the respective terminals. The corners of the via P 11  preferably face the corners of the respective terminals T 11 , T 12 , T 21  and T 22 . With this arrangement, the sides of the via are not positioned parallel to the sides of the terminals, and thus, unnecessary electromagnetic coupling between the via and the terminals can be suppressed, which results in improved isolation properties. Prismatic vias arranged in the above manner are suitable for vias through which a large current flows. Normally, a large principal current flows through the first line of the coupler, and thus, in order to reduce electromagnetic coupling between the via and the terminals, a prismatic via is used in this embodiment for the via P 11  that connects portions of the first line L 1 . Note, however, that the arrangement and shape are not limited to the above. 
     In this embodiment, the via P 11 , which is the longest via, has a larger cross-sectional area than the other vias P 12 , P 21  and P 22 . When forming the via P 11 , a long through hole HP 11  extending through the two insulating layers I 1  and I 2  needs to be formed by lithography and etching. Since the aspect ratio of the through hole has limits, a longer through hole should preferably have a larger width, and when the width of the through hole HP 11  is increased, the cross-sectional area of the via P 11  is increased as well. By configuring the long via P 11  to have a larger cross-sectional area than the other vias P 12 , P 21  and P 22 , the connection reliability of the via P 11  can be improved. 
     Furthermore, in this embodiment, the widest via P 11  (having the largest cross-sectional area) is arranged at the center of the four terminals T 11 , T 12 , T 21  and T 22 . Since the four terminals T 11 , T 12 , T 21  and T 22  in this embodiment are arranged at the four corners of the rectangle, the center thereof means the intersection of a virtual diagonal line connecting the terminals T 11  and T 22  and another virtual diagonal line connecting the terminals T 12  and T 21  (see the dotted lines in  FIG. 10 ). By positioning the widest via P 11  at the center of the four terminals, the via P 11  can have a certain distance from all the terminals, and accordingly, unnecessary electromagnetic coupling between the terminals and the via can effectively be reduced, resulting in improved isolation properties. 
     Furthermore, in this embodiment, the via P 21 , which is a cylindrical via having a circular shape in its cross-section parallel to the substrate surface, is arranged in the center portion adjacent to the via P 11 . The circular cross-section of the via P 21  results in the via P 21  having no side parallel to the side of the via P 11 , which can suppress electromagnetic coupling between the via P 11  and the via P 21 . In addition, the cylindrical via P 21  does not have any side parallel to any of the sides of the four surrounding terminals T 11 , T 12 , T 21  and T 22 , and thus, electromagnetic coupling between the via and the terminals can be suppressed, resulting in improved isolation properties. 
     Still furthermore, in this embodiment, the other two vias P 12  and P 22  are arranged such that, when seen in the plan view of  FIG. 10 , the via P 12  is placed between the lower two terminals T 11  and T 12  while the via P 22  is placed between the upper two terminal T 21  and T 22 . Accordingly, the space between the vias and the space between the vias and the terminals can be well balanced, and unnecessary electromagnetic coupling can thus be reduced. In addition, by using a cylindrical via for both of the vias P 12  and P 22 , the vias P 12  and P 22  do not have any side parallel to any of the sides of the other vias P 11  and P 21  or the sides of the terminals T 11 , 112 , T 21  and T 22 , and thus, unnecessary electromagnetic coupling can be suppressed, resulting in improved isolation properties. 
     Embodiment 1A 
     Next, the respective patterns of the wiring layers M 1 , M 2  and M 3  in a coupler according to Embodiment 1A will be described in detail.  FIGS. 11-16  are horizontal sectional views schematically illustrating the respective layers M 1 -M 3  and I 1 -I 3  of a coupler  1 A. As illustrated in  FIGS. 11-16 , the input terminal T 11 , the output terminal T 12 , the coupling terminal T 21 , and the isolation terminal T 22  are formed in all the wiring layers M 1 -M 3 , and the portions of the terminals T 11 , T 12 , T 21  and T 22  formed in one layer are electrically connected to the corresponding portions in a different layer. The following is a detailed explanation of the configuration of each layer. 
     Referring to  FIG. 11 , in the wiring layer M 1  formed on the insulating substrate  100  (via the insulating film  101 ), the coiled first line L 1  is formed. In the wiring layer M 1 , the outer end of the coiled first line L 1  is connected to the output terminal T 12 , and the inner end of the first line L 1  is connected to the via P 11 . The via P 11  extends from the wiring layer M 1  to the wiring layer M 3  through the insulating layers I 1  and I 2 . In the first line L 1  in the wiring layer M 1 , the portion that is opposed to the second line L 2  in the wiring layer M 2 , which will be explained later, serves as the main line L 11 . The main line indicates a portion of the first line L 1 , the portion creating electromagnetic coupling with the second line formed in a different layer. 
     Referring next to  FIG. 12 , in the insulating layer I 1  formed on the wiring layer M 1 , the through holes HT 11 , HT 12 , HT 21  and HT 22  are formed at portions corresponding to the respective terminals T 11 , T 12 , T 21  and T 22 . Also formed in the insulating layer I 1  is the through hole HP 11 , which is formed at a portion corresponding to the via P 11 . Herein, a through hole refers to an opening (hole) formed in an insulating layer, and a via refers to a conductor formed by putting metal into such a through hole. 
     Referring next to  FIG. 13 , in the wiring layer M 2  formed on the insulating layer I 1 , the coiled second line L 2  is formed. In the wiring layer M 2 , the outer end of the coiled second line L 2  is connected to the isolation terminal T 22 , and the inner end of the second line L 2  is connected to the via P 21 . The via P 21  extends from the wiring layer M 2  to the wiring layer M 3  through the insulating layer I 2 . A portion of the second line L 2  in the wiring layer M 2  is opposed to the first line L 1  in the wiring layer M 1 , and the opposed portion serves as the secondary line L 21 . The secondary line indicates a portion of the second line L 2 , the portion creating electromagnetic coupling with the first line L 1  formed in a different layer. Also, the connecting wirings L 12  and L 22  are formed around the secondary line L 21 . The connecting wiring L 12  is a portion of the first line L 1 , and one end thereof is connected to the input terminal T 11  and the other end is connected to the via P 12 . The via P 12  extends through the insulating layer I 2  to the wiring layer M 3 . The connecting wiring L 22  is a portion of the second line L 2 , and one end thereof is connected to the coupling terminal T 21  and the other end is connected to the via P 22 . The via P 22  extends through the insulating layer I 2  to the wiring layer M 3 . 
     Referring next to  FIG. 14 , in the insulating layer I 2  formed on the wiring layer M 2 , the through holes HT 11 , HT 12 , HT 21  and HT 22  are formed at portions corresponding to the respective terminals T 11 , T 12 , T 21  and T 22 . The through holes HP 11 , HP 12 , HP 21  and HP 22  are also formed in the insulating layer I 2  at portions corresponding to the vias P 11 , P 12 , P 21  and P 22 . 
     Referring next to  FIG. 15 , in the wiring layer M 3  formed on the insulating layer I 2 , the connecting wirings L 13  and L 23  are formed. The connecting wiring L 13  is a portion of the first line L 1 , and one end thereof is connected to the via P 11  and the other end is connected to the via P 12 . The connecting wiring L 23  is a portion of the second line L 2 , and one end thereof is connected to the via P 21  and the other end is connected to the via P 22 . 
     Referring next to  FIG. 16 , the passivation layer I 3  is formed on the wiring layer M 3 . The passivation layer I 3  is formed at portions excluding four corners where the terminals T 11 , T 12 , T 21  and T 22  are formed. 
       FIG. 17  is a plan view showing the wiring layout of the coupler  1 A. As shown in  FIG. 17 , the coupler  1 A has: the first line L 1  including the main line L 11  and the connecting wirings L 12  and L 13  (first connecting wiring); and the second line L 2  including the secondary line L 21  and the connecting wirings L 22  and L 23  (second connecting wiring). As can be seen from  FIGS. 11 and 13 , the main line L 11  and the secondary line L 12  are arranged in different layers so that electromagnetic coupling is generated between the different layers through the insulating layer I 1 . 
     As can be seen from dotted line A in  FIGS. 13 and 17 , the connecting wiring L 12  of the first line L 1  is located in the same layer as, and adjacently and parallel to, the secondary line L 21  of the second line L 2 , and as a result, electromagnetic coupling between the first line L 1  and the second line L 2  in the same layer is ensured. In order to increase electromagnetic coupling, two wirings should be located, at least, adjacently, and preferably parallel, to each other. With this configuration, the coupling in the coupler can be increased without increasing the number of windings of the first line L 1  or the second line L 2 , and thus, the coupling in the coupler can be increased while suppressing degradation of directivity or isolation properties. As a result, thinner couplers with reduced sizes can be achieved while maintaining various properties of the couplers. 
     Also, as can be seen from dotted line B in  FIG. 17 , a part of the connecting wiring L 13  of the first line L 1  is located in the same layer as, and adjacently and parallel to, a part of the connecting wiring L 23  of the second line L 2 , and as a result, electromagnetic coupling between the first line L 1  and the second line L 2  in the same layer is ensured. With this configuration, the coupling in the coupler can further be increased. 
     Also, in this embodiment, when portions of the same wiring intersect with each other in a plan view, the portions are arranged to be orthogonal to each other at the intersection. In other words, the intersecting portions of the first line and the intersecting portions of the second line are arranged to be orthogonal to each other. For example, in  FIG. 17 , at the (two) intersections of the connecting wiring L 13  and the main line  11 , and at the intersection of the connecting wiring L 23  and the secondary line L 21 , the two wirings are arranged to be orthogonal to each other. Electromagnetic coupling between the wirings through which the same current flows is normally unnecessary, and by avoiding such unnecessary coupling, degradation of directivity or isolation properties can be suppressed. 
     Also, in this embodiment, the via P 11  connected to the main line L 11  is formed to extend through the insulating layer I 1 . By forming the via P 11  to wire out the first line L 1  to the wiring layer M 2  where the second line L 2  is formed, the first line L 1  and the second line L 2  can share wiring layers in which the respective lines are to be formed. Consequently, the number of layers in the coupler can be reduced and this reduction contributes to a thinner coupler. 
     Embodiment 1B 
     Next, the configuration of a coupler according to Embodiment 1B will be described.  FIGS. 18-22  are horizontal sectional views schematically illustrating the respective layers M 1 -M 3  and I 1 -I 2  of a coupler  1 B. The pattern of the passivation layer I 3  of Embodiment 1B is the same as that of Embodiment 1A. Also, as with Embodiment 1, the terminals T 11 ,T 12 ,T 21  and T 22  are formed in all the wiring layers M 1 -M 3 . 
     Referring to  FIG. 18 , in the wiring layer M 1  formed on the insulating substrate  100  (via the insulating film  101 ), the coiled first line L 1  is formed. In Embodiment 1B, the first line L 1  formed in the wiring layer M 1  has a different number of windings from that of Embodiment 1A, and the position of the inner end also differs from Embodiment 1A. Accordingly, the via P 11  of Embodiment 1A, which is connected to the inner end of the first line L 1 , is arranged in an area close to the isolation terminal T 22  (see  FIG. 11 ); whereas, the via P 11  of Embodiment 1B, which is connected to the inner end of the first line L 1 , is arranged at the center portion of the four terminals T 11 , T 12 , T 21  and T 22 . Other than the above, the wiring layer M 1  has the same configuration as Embodiment 1. 
     Referring next to  FIG. 19 , in the insulating layer I 1  formed on the wiring layer M 1 , the through holes HT 11 , HT 12 , HT 21  and HT 22  are formed at portions corresponding to the respective terminals T 11 , T 12 , T 21  and T 22 . Also formed in the insulating layer I 1  is the through hole HP 11 , which is formed at a portion corresponding to the via P 11 . 
     Referring next to  FIG. 20 , in the wiring layer M 2  formed on the insulating layer I 1 , the coiled second line L 2  is formed. In Embodiment 1B, the second line L 2  formed in the wiring layer M 2  has a different number of windings from that of Embodiment 1A, and the position of the inner end also differs from Embodiment 1A, Accordingly, the via P 21  of Embodiment 1A, which is connected to the inner end of the second line L 2 , is arranged in an area close to the isolation terminal T 22  (see  FIG. 13 ); whereas, the via P 21  of Embodiment 1B is arranged at the center portion of the four terminals T 11 , T 12 , T 21  and  122 . Also, the connecting wirings L 12  and L 22  are formed around the secondary line L 21 , and to what the connecting wirings L 12  and L 22  are each connected is the same as in Embodiment 1A. 
     Referring next to  FIG. 21 , in the insulating layer I 2  formed on the wiring layer M 2 , the through holes HT 11 , HT 12 , HT 21  and H 122  are formed at portions corresponding to the respective terminals T 11 , T 12 , T 21  and T 22 . Also, the through holes HP 11 , HP 12 , HP 21  and HP 22  are formed in the insulating layer I 2  at portions corresponding to the vias P 11 , P 12 , P 21  and P 22 . 
     Referring next to  FIG. 22 , in the wiring layer M 3  formed on the insulating layer I 2 , the connecting wirings L 13  and L 23  are formed. Since the positions of the vias P 11  and P 21  are different from Embodiment 1A, the positions of the connecting wirings L 13  and L 23  are also different from Embodiment 1A; however, to what the respective wirings L 13  and L 23  are connected is the same as in Embodiment 1A. 
       FIG. 23  is a plan view showing the wiring layout of the coupler  1 B. As shown in  FIG. 23 , the coupler  1 B has: the first line L 1  including the main line L 11  and the connecting wirings L 12  and L 13  (first connecting wiring); and the second line L 2  including the secondary line L 21  and the connecting wirings L 22  and L 23  (second connecting wiring). As with Embodiment 1A, the main line L 11  and the secondary line L 21  are arranged in different layers so that electromagnetic coupling is generated between the different layers through the insulating layer I 1 . 
     As can be seen from dotted line D in  FIGS. 20 and 23 , the connecting wiring L 12  of the first line L 1  is located in the same layer as, and adjacently and parallel to, the secondary line L 21  of the second line L 2 , and as a result, electromagnetic coupling between the first line L 1  and the second line L 2  in the same layer is ensured. The effect of this configuration is as described in Embodiment 1A. 
     In Embodiment 1B as well, as with Embodiment 1A, when portions of the same wiring intersect with each other in a plan view, the portions are arranged to be orthogonal to each other at the intersection. For example, in  FIG. 23 , at the intersection of the connecting wiring L 13  and the main line  11 , and at the intersection of the connecting wiring L 23  and the secondary line L 21 , the two wirings are arranged to be orthogonal to each other. The effect of this configuration is as described in Embodiment 1A. 
     Furthermore, in Embodiment 1B as well, as with Embodiment 1A, the via P 11  connected to the main line L 11  is formed to extend through the insulating layer I 1 . The effect thereof is as described in Embodiment 1A. 
     Embodiment 1C 
     Next, the configuration of a coupler according to Embodiment 1C will be described.  FIGS. 24-28  are horizontal sectional views schematically illustrating the respective layers M 1 -M 3  and I 1 -I 2  of a coupler  1 C. The pattern of the passivation layer I 3  of Embodiment 1C is the same as that of Embodiment 1A. Also, as with Embodiment 1, the terminals T 11 ,T 12 ,T 21  and T 22  are formed in all the wiring layers M 1 -M 3 . 
     Referring to  FIG. 24 , in the wiring layer M 1  formed on the insulating substrate  100  (via the insulating film  101 ), the coiled first line L 1  is formed. In Embodiment 1C, the first line L 1  formed in the wiring layer M 1  has a different number of windings from that of Embodiment 1A, and the position of the inner end also differs from Embodiment 1A. Accordingly, the via P 11  of Embodiment 1A, which is connected to the inner end of the first line L 1 , is arranged in an area close to the isolation terminal T 22  (see  FIG. 11 ); whereas, the via P 11  of Embodiment 1C, which is connected to the inner end of the first line L 1 , is arranged in an area close to the input terminal T 11 . Other than the above, the wiring layer M 1  has the same configuration as Embodiment 1. 
     Referring next to  FIG. 25 , in the insulating layer I 1  formed on the wiring layer M 1 , the through holes HT 11 , HT 12 , HT 21  and HT 22  are formed at portions corresponding to the respective terminals T 11 , T 12 , T 21  and T 22 . Also formed in the insulating layer I 1  is the through hole HP 11 , which is formed at a portion corresponding to the via P 11 . 
     Referring next to  FIG. 26 , in the wiring layer M 2  formed on the insulating layer I 1 , the coiled second line L 2  is formed. In Embodiment 1C, the second line L 2  formed in the wiring layer M 2  has a different arrangement and a different number of windings from those of Embodiment 1A, and the position of the inner end also differs from Embodiment 1A. Accordingly, the via P 21  of Embodiment 1A, which is connected to the inner end of the second line L 2 , is arranged in an area close to the isolation terminal T 22  (see  FIG. 13 ); whereas, the via P 21  of Embodiment 1C is arranged in an area close to the coupling terminal T 21 . Also, the connecting wirings L 12  and L 22  are formed around the secondary line L 21 . The connecting wirings L 12  and L 22  in the wiring layer M 2  of Embodiment 1A are arranged at portions above and below the secondary line L 21 , respectively, in the plan view shown in  FIG. 13 ; whereas, the connecting wirings L 12  and L 22  of Embodiment 1C are arranged at the right side of the secondary line L 21  in the plan view of  FIG. 26 . In order to create a space for arranging the connecting wirings L 12  and L 22  in the above manner, the second line L 2  of Embodiment 1C is located closer to the center, compared to Embodiment 1A. Note that to what the connecting wirings L 12  and L 22  are each connected is the same as in Embodiment 1A. 
     Referring next to  FIG. 27 , in the insulating layer I 2  formed on the wiring layer M 2 , the through holes HT 11 , HT 12 , HT 21  and HT 22  are formed at portions corresponding to the respective terminals T 11 , T 12 , T 21  and T 22 . Also, the through holes HP 11 , HP 12 , HP 21  and HP 22  are formed in the insulating layer I 2  at portions corresponding to the vias P 11 , P 12 , P 21 , and P 22 . 
     Referring next to  FIG. 28 , in the wiring layer M 3  formed on the insulating layer I 2 , the connecting wirings L 13  and L 23  are formed. The connecting wirings L 13  and L 23  are arranged to be adjacent and parallel to each other, so as to achieve electromagnetic coupling between them. Since the positions of the vias P 11 , P 12 , P 21  and P 22  are different from Embodiment 1A, the positions of the connecting wirings L 13  and L 23  of Embodiment 1C are also different from Embodiment 1A; however, to what the wirings L 13  and L 23  are each connected is the same as in Embodiment 1A. 
       FIG. 29  is a plan view showing the wiring layout of the coupler  1 C. As shown in  FIG. 29 , the coupler  1 C has: the first line L 1  including the main line L 11  and the connecting wirings L 12  and L 13  (first connecting wiring); and the second line L 2  including the secondary line L 21  and the connecting wirings L 22  and L 23  (second connecting wiring). As with Embodiment 1A, the main line L 11  and the secondary line L 21  are arranged in different layers, so that electromagnetic coupling is generated between different layers through the insulating layer I 1 . 
     As can be seen from dotted line E in  FIGS. 28 and 29 , the connecting wiring L 13  of the first line L 1  is located in the same layer as, and adjacently and parallel to, the connecting wiring L 23  of the second line L 2 , and as a result, electromagnetic coupling between the first line L 1  and the second line L 2  in the same layer is ensured. The effect of the above configuration is as described in Embodiment 1A. 
     In Embodiment 1C as well, as with Embodiment 1A, when portions of the same wiring intersect with each other in a plan view, the portions are arranged to be orthogonal to each other at the intersection. For example, in  FIG. 29 , at the intersection of the connecting wiring L 13  and the main line  11 , and at the intersection of the connecting wiring L 23  and the secondary line L 21 , the two wirings are arranged to be orthogonal to each other. The effect of this configuration is as described in Embodiment 1A. 
     Furthermore, in Embodiment 1C as well, as with Embodiment 1A, the via P 11  connected to the main line L 11  is formed to extend through the insulating layer I 1 . The effect thereof is as described in Embodiment 1A. 
     Embodiment 1D 
     Next, the configuration of a coupler according to Embodiment 1D will be described.  FIGS. 30-34  are horizontal sectional views schematically illustrating the respective layers M 1 -M 3  and I 1 -I 2  of a coupler  1 D. The pattern of the passivation layer I 3  of Embodiment 1D is the same as that of Embodiment 1A. Also, as with Embodiment 1, the terminals T 11 ,T 12 ,T 21  and T 22  are formed in all the wiring layers M 1 -M 3 . 
     Referring to  FIG. 30 , in the wiring layer M 1  formed on the insulating substrate  100  (via the insulating film  101 ), the coiled first line L 1  is formed. In Embodiment 1D, the first line L 1  formed in the wiring layer M 1  has a different number of windings from that of Embodiment 1A, and the position of the inner end also differs from Embodiment 1A. In Embodiment 1D, as with Embodiment 1B, the via P 11  connected to the inner end of the first line L 1  is arranged at the center portion of the four terminals T 11 , T 12 , T 21  and T 22 . Also, in Embodiment 1D, unlike Embodiment 1A, the connecting wiring L 22 , which constitutes a portion of the second line L 2 , is formed in the wiring layer M 1 , outside the first line L 1 . One end of the connecting wiring L 22  is connected to the coupling terminal T 21  and the other end is connected to the via P 22 . The via P 22  extends through the insulating layers I 1  and I 2  to the wiring layer M 3 . Other than the above, the configuration of the wiring layer M 1  is the same as Embodiment 1. 
     Referring next to  FIG. 31 , in the insulating layer I 1  formed on the wiring layer M 1 , the through holes HT 11 , HT 12 , HT 21  and HT 22  are formed at portions corresponding to the respective terminals T 11 , T 12 , T 21  and T 22 . Also formed in the insulating layer I 1  are the through holes HP 11  and HP 22 , which are formed at portions corresponding to the vias P 11  and P 22 . 
     Referring next to  FIG. 32 , in the wiring layer M 2  formed on the insulating layer I 1 , the coiled second line L 2  is formed. In Embodiment 1D, the second line L 2  formed in the wiring layer M 2  has a different number of windings from that of Embodiment 1A, and the position of the inner end also differs from Embodiment 1A. Accordingly, in Embodiment 1D, as with Embodiment 1B, the via P 21  connected to the inner end of the second line L 2  is arranged at the center portion of the four terminals T 11 , T 12 , T 21  and T 22 . Also, as with Embodiment 1A, the connecting wiring L 12  is arranged around the secondary line L 21 ; however, unlike Embodiment 1A, the connecting wiring L 22  is not formed in the wiring layer M 2 . 
     Referring next to  FIG. 33 , in the insulating layer I 2  formed on the wiring layer M 2 , the through holes HT 11 , HT 12 , HT 21  and HT 22  are formed at portions corresponding to the respective terminals T 11 , T 12 , T 21  and T 22 . Also, the through holes HP 11 , HP 12 , HP 21  and HP 22  are formed in the insulating layer I 2  at portions corresponding to the vias P 11 , P 12 , P 21  and P 22 . 
     Referring next to  FIG. 34 , in the wiring layer M 3  formed on the insulating layer I 2 , the connecting wirings L 13  and L 23  are formed. The arrangement of the connecting wirings L 13  and L 23  in Embodiment 1D is different from Embodiment 1A, but the same as Embodiment 1B. 
       FIG. 35  is a plan view showing the wiring layout of the coupler  1 D. As shown in  FIG. 35 , the coupler  1 D has: the first line L 1  including the main line L 11  and the connecting wirings L 12  and L 13  (first connecting wiring); and the second line L 2  including the secondary line L 21  and the connecting wirings L 22  and L 23  (second connecting wiring). As with Embodiment 1A, the main line L 11  and the secondary line L 21  are arranged in different layers so that electromagnetic coupling is generated between the different layers through the insulating layer I 1 . 
     As can be seen from dotted line F in  FIG. 35 , the connecting wiring L 12  of the first line L 1  is located in the same layer as, and adjacently and parallel to, the secondary line L 21  of the second line L 2 , and as a result, electromagnetic coupling between the first line L 1  and the second line L 2  in the same layer is ensured. Also, as can be seen from dotted line G in  FIG. 35 , the connecting wiring L 22  of the second line L 2  is located in the same layer as, and adjacently and parallel to, the main line L 11  of the first line L 1 , and as a result, electromagnetic coupling between the first line L 1  and the second line L 2  in the same layer is ensured. The effect of the above configuration is as described in Embodiment 1A. 
     In Embodiment 1D as well, as with Embodiment 1A, when portions of the same wiring intersect with each other in a plan view, the portions are arranged to be orthogonal to each other at the intersection. For example, in  FIG. 35 , at the intersection of the connecting wiring L 13  and the main line  11 , and at the intersection of the connecting wiring L 23  and the secondary line L 21 , the two wirings are arranged to be orthogonal to each other. The effect of this configuration is as described in Embodiment 1A. 
     Furthermore, in Embodiment 1D as well, as with Embodiment 1A, the via P 11  connected to the main line L 11  is formed to extend through the insulating layer I 1 . The effect thereof is as described in Embodiment 1A. 
     As mentioned before, the invention is not limited to the respective embodiments above, and can be modified in various ways without changing the gist of the invention. For example, the second line may be wired out to the first line using the via, instead of wiring out the first line to the second line. Also, there is no limitation on the order of the wiring layers stacked on the substrate, and for example, the secondary line may be arranged closer to the substrate than the main line. Also, the positions of the terminals T 11 , T 12 , T 21  and T 22  may be changed arbitrarily, and depending on such change of the positions of the terminals, the wiring layout may also be changed. Also, various types of coil arrangements may be employed without departing from the gist of the invention. 
     Since the invention can provide a coupler that is thinner and smaller in size and still satisfies the required various properties of couplers, the invention can be utilized, in particular, in radio communication devices, apparatuses, modules and systems that require thinner and smaller sizes, as well as equipment provided with such devices, etc., and can also widely be used in the manufacturing thereof. 
     According to an aspect of the invention, at least one of the first line and the second line is wired out through the via to the same side of the insulating layer as the other one of the first and second lines, and the first and second lines can thus share wiring layers in which the respective lines are to be formed. As a result, the number of layers in the coupler can be reduced, and this reduction of layers allows a thinner coupler. Accordingly, thinner and smaller couplers can be achieved while maintaining the various properties of the couplers. 
     Also, according to another aspect of the invention, electromagnetic coupling between the first and second lines is generated not only in different layers but also within the same layer, and thus, the coupling in the coupler can be increased. Accordingly, thinner and smaller couplers can be achieved while maintaining the required various properties of the couplers.