Common mode filter and optical transceiver

Abstract

To provide a miniaturized optical transceiver that suppresses a suppression band width and a suppression ratio of a common mode compared to a conventional one, and enhances a degree of freedom of design of a differential transmission line.SOLUTION: A common mode filter includes: a pair of differential signal lines formed in a multilayer substrate having a dielectric layer; a ground conductor formed in a layer below the pair of differential signal lines; a resonant conductor pattern formed in the same layer as or a layer above the ground conductor, covering a partial region of the pair of differential signal lines in a plan view, and connected to the ground conductor; and a cover conductor pattern formed in a layer above the pair of differential signal lines, covering the resonant conductor pattern in a plan view, and connected to the ground conductor.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a common mode filter and an optical transceiver.

Background Art

[0002] In high-speed data communication, differential transmission systems are widely used for the purpose of increasing the data rate by suppressing the amplitude of the signal voltage and reducing radiation loss. To suppress common mode noise caused by various factors, a common mode filter may be used in the transmission line. The common mode filter is supplied to the market as an independent electronic component using a choke coil or the like, which is inserted into the differential transmission line and used.

[0003] In electronic components using differential transmission signals, attempts have been made to realize a common mode filter by a printed pattern formed in a multilayer substrate instead of using a common mode filter as an independent electronic component for the purpose of further miniaturization and high performance. Patent Document 1 describes a differential transmission line and a communication device including a band stop filter region that attenuates the common mode of differential transmission signals.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the common mode filter formed in the differential transmission line described in Patent Document 1, the common mode suppression effect is high. From the analysis result of the differential transmission line shown in FIG. 5 of the same document, it can be seen that the common mode is widely suppressed over a width of 10 GHz or more centered on a frequency of 20.5 GHz, and a suppression ratio of approximately -35 dB is achieved at the center frequency.

[0006] The fact that the bandwidth in which such a common-mode suppression effect is exhibited is wide and the suppression is high is not necessarily only an advantage as a common-mode filter. For example, the signal processing circuit in the optical communication module described in Patent Document 1 is designed to output only differential-mode signals ideally, and common-mode noise is, in most cases, smaller than the differential-mode signal. Therefore, the common-mode signal suppression ratio required for a common-mode filter is often sufficient at about 3 to 5 dB.

[0007] Also, in paragraph 0056 of Patent Document 1, it is cautioned that the planar distance from the connection pad of the signal processing circuit to the via hole connecting to the resonator of the common-mode filter should not be near an integer multiple of half the resonance wavelength. As described in the same document, this is because a loop path is formed in which the common-mode component whose transmission is suppressed returns to the signal processing circuit through the ground conductor. When this loop path length coincides with near an integer multiple of the propagation wavelength, such a loop path functions as a loop antenna, and the suppressed common-mode component is radiated as radiated noise.

[0008] This means that if the bandwidth in which the suppression effect by the common-mode filter is exhibited is wide, the geometric conditions for such a loop path to function as a loop antenna are wide, and the design freedom when designing the differential transmission line is reduced.

[0009] The present invention has been made in view of such circumstances, and its object is to use a common-mode filter realized by a printed pattern formed in a multilayer substrate in a differential transmission line, reduce the common-mode suppression bandwidth and suppression ratio compared with the conventional ones, increase the design freedom of the differential transmission line, and provide a miniaturized optical transceiver.

Means for Solving the Problem

[0010] In order to solve the above problems, the invention disclosed in the present application has various aspects, and an outline of typical ones among those aspects is as follows.

[0011] (1) A pair of differential signal lines formed in a multilayer substrate having a dielectric layer, a ground conductor formed in a layer below the pair of differential signal lines, and formed in the same layer or an upper layer as the ground conductor, in a plan view, covering a region of a part of the pair of differential signal lines, a resonance conductor pattern connected to the ground conductor, and formed in a layer above the pair of differential signal lines, in a plan view, covering the resonance conductor pattern, and a cover conductor pattern connected to the ground conductor.

[0012] (2) The common mode filter according to (1), wherein the resonance conductor pattern is composed of a plurality of patterns having different geometric shapes from each other or different relative connection positions with respect to the ground conductor.

[0013] (3) The common mode filter according to (2), wherein in any two patterns included in the plurality of patterns, a distance in a plan view between a connection position with the ground conductor in one pattern and a connection position with the ground conductor in the other pattern is shorter than 3 / 8 resonance wavelength for each of the two patterns.

[0014] (4) The common mode filter according to (2), wherein one pattern and another pattern included in the plurality of patterns are formed in different layers and at least a part of them overlaps in a plan view.

[0015] (5) The common mode filter according to (2), wherein one pattern included in the plurality of patterns is formed in a layer below the differential signal lines, and another pattern is formed in a layer above the differential signal lines.

[0016] (6)(5), the one pattern is connected to the ground conductor via a via, and the other one pattern is connected to the cover conductor pattern via a via, a common mode filter.

[0017] (7)(1), formed in the same layer as the resonance conductor pattern, having a sub-ground conductor pattern that surrounds the resonance conductor pattern and is connected to the ground conductor, the resonance conductor pattern is partitioned from the sub-ground conductor pattern with an insulating gap and is separated from the sub-ground conductor pattern within the same layer, a common mode filter.

[0018] (8)(1), formed in the same layer as the resonance conductor pattern, having a sub-ground conductor pattern that surrounds the resonance conductor pattern and is connected to the ground conductor, the resonance conductor pattern is partitioned from the sub-ground conductor pattern with an insulating gap and is connected to the sub-ground conductor pattern at at least one side of the resonance conductor pattern, a common mode filter.

[0019] (9)(1), the resonance conductor pattern is formed in the same layer as the ground conductor, partitioned from the ground conductor with an insulating gap, and is connected to the ground conductor at at least one side of the resonance conductor pattern, a common mode filter.

[0020] (10)(1), the number of connection points between the cover conductor pattern and the ground conductor is more than the number of connection points between the resonance conductor pattern and the ground conductor, a common mode filter.

[0021] (11)(1) to (10), one end of the differential signal line is connected to a surface mounting terminal formed on the surface layer of the multilayer substrate via a via, and the other end is connected to an external connection terminal formed on at least one of the surface layer and the back layer via a via, a common mode filter.

[0022] In (12)(11), the length obtained by adding the distance in a plan view between the via connecting the differential signal line and the surface mounting terminal and the distance in a side view between the differential signal line and the surface mounting terminal to the distance in the plan view between the connection positions of the resonance conductor pattern and the ground conductor is shorter than 3 / 8 of the resonance wavelength for the resonance conductor pattern, a common mode filter.

[0023] An optical transceiver having: the common mode filter of (13)(11); a signal processing circuit mounted on the multilayer substrate via the surface mounting terminal; a photoelectric conversion circuit mounted on the multilayer substrate and connected to the signal processing circuit; and an optical fiber connector optically connected to the photoelectric conversion circuit.

[0024] An optical transceiver having: the common mode filter of (14)(12); a signal processing circuit mounted on the multilayer substrate via the surface mounting terminal; a photoelectric conversion circuit mounted on the multilayer substrate and connected to the signal processing circuit; and an optical fiber connector optically connected to the photoelectric conversion circuit.

Brief Description of the Drawings

[0025]

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Embodiments for Carrying Out the Invention

[0026] FIG. 1 is a schematic plan view of a filter component 1 in which a common mode filter 100 according to a first embodiment of the present invention is formed, FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1, and FIG. 3 is a cross-sectional view taken along line III-III of FIG. 1.

[0027] The filter component 1 is formed in some layers of a multilayer substrate that is a dielectric multilayer printed circuit board, and metal conductor patterns such as copper and aluminum are usually formed on each layer of the multilayer substrate. In this specification, the layer exposed on the surface of the multilayer substrate is called the surface layer, and the layer exposed on the back surface is called the back surface layer. Also, the layer closest to the outermost surface layer of the filter component 1 is called the 0th layer, the layer below it is called the 1st layer, and the layer further below is called the 2nd layer, and so on. The total number of layers of the filter component 1 is at least 3 layers as disclosed in the following multiple embodiments, and in many cases, there are 5 layers or more. Therefore, the surface layer of the multilayer substrate and the 0th layer of the filter component 1 do not necessarily represent the same layer. Similarly, the back surface layer of the multilayer substrate does not necessarily represent the lowermost layer of the filter component 1. A dielectric layer 10 such as a glass epoxy material, a ceramic material, a PPE material, or a Teflon (registered trademark) material is disposed between each layer of the multilayer substrate including the filter component 1, and the connection between the conductor patterns of each layer is made by vias provided as appropriate.

[0028] As is clear from FIGS. 2 and 3, the filter component 1 according to the present embodiment is shown as having 4 layers, but it may have 5 layers or more. Also, the filter component 1 shown in FIG. 1 is shown as having a rectangular outer shape, but this is only a part necessary for the convenience of the following description cut out in a rectangular shape, and it may have a shape that spreads further outward, and its outer shape is also arbitrary. The same applies to other embodiments hereinafter.

[0029] And in the filter component 1, a pair of differential signal lines 11 and a common mode filter 100 on the transmission path of the differential signal lines 11 are formed by a conductor pattern. In FIG. 1, the area where the common mode filter is formed is indicated by a thick dashed line.

[0030] The differential signal lines 11 are formed on the first layer and are arranged in parallel in the left - right direction of FIG. 1. Also, on the fourth layer, a ground conductor 12 is formed as a solid pattern and is connected to the ground potential outside the figure. Note that the ground conductor 12 is formed in the layer below the differential signal lines 11, but it does not necessarily have to be the back layer, and further, the fifth layer, the sixth layer, ··· may exist.

[0031] In the second layer, which is the layer below the differential signal lines 11 and above the ground conductor 12, a resonance conductor pattern 13 is provided that covers a partial region of the differential signal lines 11 in a plan view, that is, in the projection of FIG. 1, and is connected to the ground conductor 12 by two vias 13V - 1, 13V - 2. In this example, the resonance conductor pattern 13 is rectangular, and the vias 13V - 1, 13V - 2 are provided on the intermediate line of the pair of differential signal lines 11 and are biased to one side of the resonance conductor pattern 13, the left side in the example of FIG. 1.

[0032] Furthermore, in the layer 0, which is the layer above the differential signal lines 11, a cover conductor pattern 14 is provided that covers the resonance conductor pattern 13 in a plan view and is connected to the ground conductor 12 by eight vias 14V - 1~14V - 8. In this example, the cover conductor pattern 14 is rectangular, and the vias 14V - 1~14V - 8 are evenly provided at the peripheral edge of the cover conductor pattern 14.

[0033] Here, in this specification, "A covers B" in a plan view is used to mean that A overlaps not only the region of B but also the outer region adjacent to B. Therefore, the resonance conductor pattern 13 overlaps not only a partial region of the differential signal line 11 but also the region adjacent thereto and sandwiched by the differential signal lines 11, and the upper and lower adjacent regions shown in FIG. 1 outside the differential signal lines 11. Further, the cover conductor pattern 14 overlaps the outer region adjacent to the four sides of the resonance conductor pattern 13. Although the cover conductor pattern 14 is described as narrower than the ground conductor 12 in this embodiment, actually the cover conductor pattern 14 may be wider than the ground conductor 12. Further, when viewed in the schematic plan view of FIG. 1, the cover conductor pattern 14 may cover not only a part but also the whole of the differential signal line 11. Also, in the cross-sectional views of FIGS. 2 and 3 in this embodiment, the cover conductor pattern 14 is shown as the surface layer, but this is not necessarily the case, and a dielectric layer may be further provided above the cover conductor pattern 14, and another layer (not shown) may be further provided. The same applies to other embodiments described hereinafter.

[0034] By changing the specific dimensions and shape of the resonance conductor pattern 13, the positions and numbers of the vias 13V-1 and 13V-2, and the material and thickness of the dielectric layer, the filter characteristics such as the resonance frequency of the common-mode filter 100 can be adjusted according to the usage conditions of the differential signal line 11. The filter characteristics can be measured by actually fabricating the filter component 1 in which the common-mode filter 100 is formed and measuring its characteristics. In addition, by using a high-frequency simulator to simulate and estimate the specification on a computer, it can be used for a specific design.

[0035] Also, in the region S that overlaps with the resonance conductor pattern 13 of the differential signal line 11, the line width is made narrow. This is because the differential signal line 11 and the resonance conductor pattern 13 are close to each other in the region S, so the characteristic impedance in the region S is different from that of the regions before and after it, and to prevent signal reflection and the like. The change in the characteristic impedance between the region S and the regions before and after it is made to be non-existent or small. Note that the narrowing of the differential signal line 11 is not necessarily essential and may be implemented as needed. In the following embodiments, for the sake of simplicity of explanation, the narrowing of the differential signal line 11 will not be mentioned, but it goes without saying that this may be implemented.

[0036] The results of calculating the filter characteristics of the common mode filter 100 according to the configuration of the above first embodiment by a high-frequency simulator are shown in FIG. 4. FIG. 4 shows the frequency characteristics of the common mode filter 100 created under three different design conditions, and the characteristic impedance of the differential signal line 11 is about 100 ohms in each case. Each design condition is as follows in the following table:

Table 1

[0037] As can be read from FIG. 4, under design condition 1, the suppression width where the suppression ratio of the common mode is -3 dB or less is approximately 1.7 GHz, and the peak suppression ratio at the center frequency is -16 dB. Under design condition 2, the suppression width is approximately 4.1 GHz, and the peak suppression ratio is -24 dB. Under design condition 3, the suppression width is approximately 0.8 GHz, and the peak suppression ratio is -10.4 dB.

[0038] As described above, in the common mode filter 100 according to the present embodiment, compared with what has already been shown as the prior art, the suppression bandwidth has been narrowed and the suppression ratio has been suppressed, which increases the design freedom of the differential transmission line and clearly contributes to the miniaturization of the device using the common mode filter 100. Also, by setting different design conditions, the suppression bandwidth, suppression ratio, and center frequency of the common mode filter 100 can be adjusted to some extent, and it can be seen that it is possible to design the common mode filter 100 according to various usage conditions of the differential signal line 11.

[0039] Also, in the present embodiment, the number of connection points between the cover conductor pattern 14 and the ground conductor 12 is eight, namely vias 14V-1 to 14V-8, while the number of connection points between the resonance conductor pattern 13 and the ground conductor 12 is two, namely vias 13V-1 and 13V-2, and the number of connection points between the cover conductor pattern 14 and the ground conductor 12 is larger. This is because the resonance conductor pattern 13 is mainly intended to function as the common mode filter 100 by creating electrical vibrations inside the resonance conductor pattern 13, whereas the cover conductor pattern 14 is mainly intended to maintain as uniform a ground potential as possible with the ground conductor 12. In that sense, it is normal for the cover conductor pattern 14 and the ground conductor 12 to be connected by more than two vias, and it is also acceptable if there are more than the eight shown in the figure. With such a structure, the desired characteristics of the common mode filter 100 can be obtained.

[0040] FIG. 5 is a schematic plan view of the filter component 1 in which the common mode filter 200 according to the second embodiment of the present invention is formed, FIG. 6 is a cross-sectional view taken along line VI-VI of FIG. 5, and FIG. 7 is a cross-sectional view taken along line VII-VII of FIG. 5. In the description of the illustrated common mode filter 200, the same reference numerals are given to the configurations common to the previous embodiment, and the overlapping descriptions are incorporated by reference to the previous explanations.

[0041] Also in the second embodiment, similar to the previous embodiment, the filter component 1 has four layers. The differential signal line 11 is provided in the first layer, the ground conductor 12 is provided in the fourth layer, the rectangular resonance conductor pattern 13 is provided in the second layer which is the layer below the differential signal line 11 and above the ground conductor 12, and the rectangular cover conductor pattern 14 is provided in the zeroeth layer. In a plan view, it is also the same that the resonance conductor pattern 13 covers a part of the region of the differential signal line 11 and the cover conductor pattern 14 covers the resonance conductor pattern 13. Also, the resonance conductor pattern 13 is connected to the ground conductor 12 by the via 13V-1, and the cover conductor pattern 14 is connected to the ground conductor 12 by eight vias 13V-1 to 14V-8. Similar to the previous embodiment, setting the number of vias connecting the cover conductor pattern 14 and the ground conductor 12 to eight is just an example and is not limited thereto. Generally, since the ground potential of the cover conductor pattern 14 becomes more stable when more vias are used, the number of vias connecting the cover conductor pattern 14 and the ground conductor 12 may be selected to be a sufficient number for the ground potential of the cover conductor pattern 14 to be stable, and that number may be smaller than 8 or larger than 8. The same applies to the embodiments described hereinafter.

[0042] The common mode filter 200 further has a secondary ground conductor pattern 15 that surrounds the resonance conductor pattern 13 and is connected to the ground conductor 12 in the second layer that is the same layer as the resonance conductor pattern 13 in a plan view. The resonance conductor pattern 13 and the secondary ground conductor pattern 15 are partitioned with an insulating gap 16 therebetween and are separated from each other within the second layer which is the same layer.

[0043] Since the secondary ground conductor pattern 15 is also electrically connected to the vias 14V-1 to 14V-8, it is kept at the same potential (i.e., the ground potential) as the ground conductor 12 through such vias 14V-1 to 14V-8. Further, vias 15V-1 to 15V-4 are provided so that the number of connection points with the ground conductor 12 increases. In the illustrated example, the number of additional vias 15V-1 to 15V-4 is four, but the number and arrangement of the additional vias are arbitrary.

[0044] Even with the common mode filter 200 having such a structure, the characteristics of the desired common mode filter 200 can be obtained as in the previous embodiment.

[0045] FIG. 8 is a schematic plan view of a filter component 1 in which a common mode filter 300 according to a third embodiment of the present invention is formed, FIG. 9 is a cross-sectional view taken along line IX-IX of FIG. 8, and FIG. 10 is a cross-sectional view taken along line X-X of FIG. 8. In the description of the illustrated common mode filter 300, components common to the previous embodiment are denoted by the same reference numerals, and redundant descriptions thereof are incorporated by reference to the previous description.

[0046] In the third embodiment, the filter component 1 has five layers. A differential signal line 11 is provided in the first layer, a ground conductor 12 is provided in the fifth layer, and a first resonant conductor pattern 13-1 and a second resonant conductor pattern 13-2 that constitute a resonant conductor pattern 13 are provided in the third layer and the second layer, respectively, which are layers below the differential signal line 11 and above the ground conductor 12. Further, a rectangular cover conductor pattern 14 is provided in the 0th layer. In plan view, the first resonant conductor pattern 13-1 and the second resonant conductor pattern 13-2 each cover a partial region of the differential signal line 11, and the cover conductor pattern 14 covers the resonant conductor pattern 13, that is, covers both the first resonant conductor pattern 13-1 and the second resonant conductor pattern 13-2. The cover conductor pattern 14 is connected to the ground conductor by eight vias 13V-1 to 14V-8 as in the previous embodiment. Further, in the third layer, which is the same layer as the first resonant conductor pattern 13-1, a sub-ground conductor pattern 15 that surrounds the first resonant conductor pattern 13-1 in plan view and is connected to the ground conductor 12 is provided. The first resonant conductor pattern 13-1 and the sub-ground conductor pattern 15 are partitioned by an insulating gap 16 and are separated from each other within the third layer, which is the same layer. Furthermore, the sub-ground conductor pattern 15 is not only electrically connected to the vias 14V-1 to 14V-8 but also connected to the ground conductor 12 by additional vias 15V-1 to 15V-4.

[0047] In the common mode filter 300 according to this embodiment, the resonance conductor pattern 13 is composed of a first resonance conductor pattern 13-1 and a second resonance conductor pattern 13-2. The first resonance conductor pattern 13-1 formed on the third layer is rectangular and is connected to the ground conductor 12 by a via 13V-1. Further, the second resonance conductor pattern 13-2, which is the layer above it, is U-shaped in plan view and is connected to the first resonance conductor pattern 13-1 by vias 13V-3 and 13V-4.

[0048] Here, the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2 have different geometric shapes, and it is considered that their resonance frequencies and filter characteristics for the common mode are also different from each other. Therefore, by configuring the resonance conductor pattern 13 with a plurality of patterns having different geometric shapes from each other, the common mode filter characteristics can be designed more flexibly than in the case of being configured with a single pattern. For example, a common mode filter 300 that functions for a plurality of resonance frequencies can be designed.

[0049] Also, in this embodiment, in plan view, a part of the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2 overlap each other. In this way, by forming one pattern included in the plurality of patterns constituting the resonance conductor pattern 13, for example, the first resonance conductor pattern 13-1, and another pattern, for example, the second resonance conductor pattern 13-2, in different layers and arranging them so that at least a part of them overlaps in plan view, the area occupied by the common mode filter 300 in plan view can be reduced, and its miniaturization can be achieved.

[0050] Even with the common mode filter 300 having such a structure, the characteristics of the desired common mode filter 300 can be obtained as in the previous embodiment.

[0051] FIG. 11 is a schematic plan view of a filter component 1 in which a common mode filter 400 according to a fourth embodiment of the present invention is formed, FIG. 12 is a cross-sectional view taken along line XII-XII of FIG. 11, and FIG. 13 is a cross-sectional view taken along line XIII-XIII of FIG. 11. In the description of the illustrated common mode filter 400, the same reference numerals are given to the configurations common to the previous embodiments, and the overlapping descriptions are incorporated by reference to the previous descriptions.

[0052] In the fourth embodiment, the filter component 1 has four layers. A differential signal line 11 is provided in the first layer, a ground conductor 12 is provided in the third layer, and a first resonance conductor pattern 13-1 and a second resonance conductor pattern 13-2 that constitute a resonance conductor pattern 13 are provided in the second layer, which is the layer below the differential signal line 11 and above the ground conductor 12. A rectangular cover conductor pattern 14 is provided in the 0th layer. In a plan view, the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2 each cover a partial region of the differential signal line 11, and the cover conductor pattern 14 covers the resonance conductor pattern 13, that is, it covers both the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2. Similar to the previous embodiment, the cover conductor pattern 14 is connected to the ground conductor 12 by eight vias 13V-1 to 14V-8. Also, in the second layer, which is the same layer as the resonance conductor pattern 13, a sub-ground conductor pattern 15 that surrounds the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2 in a plan view and is connected to the ground conductor 12 is provided. The first resonance conductor pattern 13-1, the second resonance conductor pattern 13-2, and the sub-ground conductor pattern 15 are partitioned by an insulating gap 16 and are separated from each other within the second layer, which is the same layer. Further, the sub-ground conductor pattern 15 is not only electrically connected to the vias 14V-1 to 14V-8 but also connected to the ground conductor 12 by additional vias 15V-1 to 15V-4.

[0053] Here, the first resonant conductor pattern 13-1 and the second resonant conductor pattern 13-2 differ in their geometric shapes, relative connection positions to the ground conductor 12, or both. In the example shown in FIG. 11, the dimensions of the first resonant conductor pattern 13-1 are smaller than those of the second resonant conductor pattern 13-2. Alternatively, the first resonant conductor pattern 13-1 and the second resonant conductor pattern 13-2 may have the same geometric shape, and the relative connection positions to the ground conductor 12, that is, the positions of the vias 13V-1 and 13V-5 within the pattern, may be made different. By doing so, the filter characteristics of the first resonant conductor pattern 13-1 and the second resonant conductor pattern 13-2 can be made different from each other.

[0054] With the common-mode filter 400 having such a structure, the common-mode filter characteristics can be designed more flexibly in the same manner as in the previous embodiment, and the number of layers of the laminated substrate 1 can be reduced compared to the common-mode filter 300 according to the previous embodiment.

[0055] Note that the distance L1 between the centers of the vias 13V-1 and 13V-5 shown in FIG. 12 is preferably as short as possible, and it is more preferable that they are close to each other. In other words, it can be said that the distance in plan view between the connection position of the first resonant conductor pattern 13-1 and the ground conductor 12 and the connection position of the second resonant conductor pattern 13-2 and the ground conductor 12 is preferably short. This is to prevent the common mode removed from the differential signal line 11 from resonating between the first resonant conductor pattern 13-1 and the second resonant conductor pattern 13-2 and becoming noise.

[0056] More specifically, L1 is made shorter than 3 / 8 of the resonant wavelength for each of the first resonant conductor pattern 13-1 and the second resonant conductor pattern 13-2. This is because resonance occurs and the radiation noise increases when L1 approaches the half wavelength and integer multiples of the resonant wavelength, and it is safe in terms of design when L1 is shorter than 3 / 8 of the resonant wavelength.

[0057] In the common mode filter 400 shown in the fourth embodiment, the resonant conductor pattern 13 was composed of two patterns, but the same applies when the resonant conductor pattern 13 is composed of three or more patterns. Therefore, in any two patterns included in the plurality of patterns included in the resonant conductor pattern 13, the distance in a plan view between the connection position with the ground conductor 12 in one pattern and the connection position with the ground conductor 12 in the other pattern is designed to be shorter than 3 / 8 of the resonant wavelength for each of the two patterns. Note that the resonant wavelength is the length obtained from the effective dielectric constant and the resonant frequency.

[0058] Also, regarding the width of the insulation gap 16 in the extending direction of the differential signal line 11 shown in FIG. 12, it is preferably as small as possible. This is because the distance from the differential signal line 11 to the ground conductor 12 at the position of the insulation gap 16 is longer than the distance to the sub-ground conductor pattern 15 or the resonant conductor pattern 13 in other parts, and the characteristic impedance of the differential signal line 11 at this part is different, so there is a risk of signal loss due to reflection or the like on the path. If the width of the insulation gap 16 is made sufficiently small, for example, when the operating frequency of the differential signal is 10 to 30 GHz, if the width of the insulation gap 16 is about 500 μm or less, the influence of the variation in the characteristic impedance of the differential signal line 11 is almost negligible and can be ignored.

[0059] FIG. 14 is a schematic plan view of the filter configuration part 1 in which the common mode filter 500 according to the fifth embodiment of the present invention is formed, FIG. 15 is a cross-sectional view taken along line XV-XV in FIG. 14, and FIG. 16 is a cross-sectional view taken along line XVI-XVI in FIG. 14. In the description of the illustrated common mode filter 500, the same reference numerals are given to the configurations common to the previous embodiments, and the overlapping descriptions are incorporated by reference to the previous descriptions.

[0060] Also in the fifth embodiment, similar to the previous embodiments, the filter component 1 has four layers. The differential signal line 11 is provided in the first layer, the ground conductor 12 is provided in the third layer, and the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2 that form the resonance conductor pattern 13 are provided in the second layer, which is the layer below the differential signal line 11 and above the ground conductor 12. Further, a rectangular cover conductor pattern 14 is provided in the 0th layer. In a plan view, the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2 each cover a partial region of the differential signal line 11, and the cover conductor pattern 14 covers the resonance conductor pattern 13, that is, it covers both the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2. The cover conductor pattern 14 is connected to the ground conductor 12 by eight vias 13V-1 to 14V-8. Also, in the second layer where the resonance conductor pattern 13 is located, in a plan view, there is a sub-ground conductor pattern 15 that surrounds the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2 and is connected to the ground conductor 12. Further, the sub-ground conductor pattern 15 is not only electrically connected to the vias 14V-1 to 14V-8 but also connected to the ground conductor 12 by additional vias 15V-1 to 15V-4.

[0061] The first resonance conductor pattern 13-1, the second resonance conductor pattern 13-2, and the sub-ground conductor pattern 15 are partitioned with an insulating gap 16 therebetween. However, the connection to the ground conductor 12 is made by connecting to the sub-ground conductor pattern 15 at one side of the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2, and there is no direct connection to the ground conductor 12 using vias as in the previous embodiments. In the example shown in FIG. 14, the first resonance conductor pattern 13-1 is connected to the sub-ground conductor pattern 15 by the connection portion 13C-1 on the left side in the figure, and the second resonance conductor pattern 13-2 is connected to the sub-ground conductor pattern 15 by the connection portion 13C-2 on the right side in the figure.

[0062] Here, the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2 also have different geometric shapes from each other, or the relative connection positions with respect to the ground conductor 12, that is, the arrangements of the connection portions 13C-1 and 13C-2 with respect to the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2 are different, so that their filter characteristics are different from each other. In the example shown here, only one connection portion 13C-1 and 13C-2 is provided for each of the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2, but a plurality of them may be provided, or their connection widths may be different. When a plurality of them are provided, they may be arranged on different sides. The specific design of the connection portions 13C-1 and 13C-2 is made so that desired filter characteristics can be obtained through simulation or experiments using a high-frequency simulator. That is, the resonance conductor pattern 13 is connected to the sub-ground conductor pattern 15 at least on one side thereof.

[0063] Also, the distance L2 in the plan view between the connection portions 13C-1 and 13C-2 shown in FIG. 14 is desirably made shorter than 3 / 8 of the resonance wavelength for each of the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2. The reason is as described in the previous embodiment. Also, even when L2 exceeds 3 / 8 of the resonance wavelength, it is desirable to design so that it does not become a length near 1 / 2 of the resonance wavelength and its integral multiples.

[0064] With the common-mode filter 500 having such a structure, similar to the previous embodiment, the common-mode filter characteristics can be designed more flexibly, and the number of vias can be reduced compared to the common-mode filter 400 according to the previous embodiment.

[0065] FIG. 17 is a schematic plan view of a filter component 1 in which a common mode filter 600 according to the sixth embodiment of the present invention is formed, FIG. 18 is a cross-sectional view taken along line XVIII-XVIII of FIG. 17, and FIG. 19 is a cross-sectional view taken along line XIX-XIX of FIG. 17. In the description of the illustrated common mode filter 600, components common to the previous embodiments are denoted by the same reference numerals, and the overlapping descriptions are incorporated by reference to the previous descriptions.

[0066] In the sixth embodiment, the filter component 1 has five layers. A differential signal line 11 is formed in the second layer, a ground conductor 12 is formed in the fourth layer, and a first resonance conductor pattern 13-1 that constitutes a resonance conductor pattern 13 is formed in the third layer. A second resonance conductor pattern 13-2 is provided in the first layer, and a rectangular cover conductor pattern 14 is provided in the 0th layer. In a plan view, the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2 each cover a part of the region of the differential signal line 11, and the cover conductor pattern 14 covers the resonance conductor pattern 13, that is, it covers both the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2. The cover conductor pattern 14 is connected to the ground conductor 12 by eight vias 13V-1 to 14V-8. Also, in the third layer of the same layer as the first resonance conductor pattern 13-1, in a plan view, there is a sub-ground conductor pattern 15 that surrounds the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2 and is connected to the ground conductor 12. That is, the sub-ground conductor pattern 15 does not overlap the resonance conductor pattern 13 in a plan view. Furthermore, the sub-ground conductor pattern 15 is not only electrically connected to the vias 14V-1 to 14V-8 but also connected to the ground conductor 12 by additional vias 15V-1 to 15V-4.

[0067] As is clear from the figure, in the present embodiment, the first resonant conductor pattern 13-1 is formed in the layer below the differential signal line 11, and the second resonant conductor pattern 13-2 is formed in the layer below the differential signal line 11. Then, the first resonant conductor pattern 13-1 is connected to the lower ground conductor 12 by the via 13V-1, and the second resonant conductor pattern 13-2 is connected to the upper cover conductor pattern 14 by the via 13V-6, thereby being indirectly connected to the ground conductor 12.

[0068] Such a configuration is also possible when the resonant conductor pattern 13 is composed of three or more patterns. That is, one pattern included in such a plurality of patterns is formed in the layer below the differential signal line 11, another pattern is formed in the layer above the differential signal line 11, and further, the one pattern is connected to the ground conductor 12 via a via, and the other pattern is connected to the cover conductor pattern 14 via a via.

[0069] Also, here, the first resonant conductor pattern 13-1 and the second resonant conductor pattern 13-2 are different in geometric shape from each other, or the relative connection positions with respect to the ground conductor 12, that is, the relative arrangements of the vias 13V-1 and 13V-6 with respect to the first resonant conductor pattern 13-1 and the second resonant conductor pattern 13-2 are different, so that their filter characteristics are different from each other.

[0070] Then, the distance L3 in the plan view between vias 13V-1 and 13V-6 shown in FIG. 18 is desirably made shorter than 3 / 8 of the resonance wavelength for each of the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2. The reason is as described in the previous embodiment. Further, the distance L4 in the plan view between the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2 is also preferably as small as possible. This is for the same reason as described regarding the width of the insulation gap 16 in the extending direction of the differential signal line 11 in the fourth embodiment, to reduce the influence of the change in the characteristic impedance of the differential signal line 11 in the section of L4. For example, when the operating frequency of the differential signal is 10 to 30 GHz, if L4 is about 500 μm or less, the influence of the variation in the characteristic impedance of the differential signal line 11 is almost negligible and can be ignored.

[0071] With the common mode filter 600 having such a structure, the common mode filter characteristics can also be designed more flexibly as in the previous embodiment.

[0072] FIG. 20 is a schematic plan view of the filter component 1 in which the common mode filter 700 according to the seventh embodiment of the present invention is formed, FIG. 21 is a cross-sectional view taken along line XXI-XXI of FIG. 20, and FIG. 22 is a cross-sectional view taken along line XXII-XXII of FIG. 20. In the description of the illustrated common mode filter 700, the same reference numerals are given to the configurations common to the previous embodiments, and the overlapping descriptions are incorporated by reference to the previous descriptions.

[0073] In the seventh embodiment, the filter component 1 has three layers. The differential signal line 11 is provided in the first layer, the ground conductor 12 is provided in the second layer, and the rectangular cover conductor pattern 14 is provided in the zero layer. The cover conductor pattern 14 is connected to the ground conductor 12 by eight vias 13V-1 to 14V-8.

[0074] The resonance conductor pattern 13 is provided on the second layer of the same layer as the ground conductor 12. That is, as shown in FIG. 20, the resonance conductor pattern 13 is partitioned from the ground conductor 12 with an insulating gap 16, and at least one side thereof, here the left side, is connected to the ground conductor 12.

[0075] In the resonance conductor pattern 13 shown here, the left side thereof is in a shape where it is continuously connected without being completely partitioned from the ground conductor 12. However, as in the first resonance conductor patterns 13-1 and 13-2 shown in FIG. 14 in the fifth embodiment, a connection portion may be provided at a part of the insulating gap 16 so as to be connected to the ground conductor 12. Also, the number and arrangement of the connection portions are arbitrary, and the resonance conductor pattern 13 is designed so as to exhibit desired filter characteristics.

[0076] Even with the common mode filter 700 having such a structure, the characteristics of the desired common mode filter 300 can be obtained, and the structure of the common mode filter 700 can be made simple.

[0077] FIG. 23 is a schematic plan view of a filter component 1 in which a common mode filter 800 according to the eighth embodiment of the present invention is formed, and FIG. 24 is a cross-sectional view taken along line XXIV-XXIV in FIG. 23. In the description of the illustrated common mode filter 800, the same reference numerals are given to the configurations common to the previous embodiments, and the overlapping descriptions thereof are incorporated by reference to the previous descriptions.

[0078] In the present embodiment, inside the region of the common mode filter 800, a filter region 17 that functions as a filter for suppressing the common mode of the differential signal line 11 is provided in particular. The filter region 17 corresponds to the region where the common mode filters 100 to 700 according to the previous first to seventh embodiments are formed, and the configuration of such a filter region 17 may be any of the previous first to seventh embodiments. Here, since the configuration of the common mode filter 400 according to the fourth embodiment is used, the following description will be along the same configuration.

[0079] In the eighth embodiment, similar to the fourth embodiment, the filter component 1 has four layers. The differential signal line 11 is provided in the first layer, the ground conductor 12 is provided in the third layer, the resonance conductor pattern 13 including the first resonance conductor pattern 13-1 and the second resonance conductor pattern 13-2 is provided in the second layer, and the sub-ground conductor pattern 15 surrounding the resonance conductor pattern 13 is provided. The rectangular cover conductor pattern 14 is provided in the 0th layer. Since the connection structure between the cover conductor pattern 14, the resonance conductor pattern 13, the sub-ground conductor pattern 15, and the ground conductor 12 is the same as that in the fourth embodiment, the description thereof is omitted here.

[0080] Here, since the differential signal line 11 is provided not in the surface layer or the back layer but in the inner layer of the multilayer substrate, when the side on which the signal processing circuit of the multilayer substrate is mounted is defined as the front side and the opposite side as the back side, in order to connect to the signal processing circuit, it is necessary to connect to the connection pad provided in the surface layer of the multilayer substrate. Also, in order to connect to an external device, it is necessary to connect to the connection pad provided in at least one of the surface layer and the back layer of the multilayer substrate, that is, the surface layer and the back layer. Therefore, one end of the differential signal line 11, the right end of the differential signal line 11 in FIG. 23, is connected to the surface mounting terminal 18 via the via 18V. Also, the other end of the differential signal line 11, the left end of the differential signal line 11 in FIG. 23, is connected to the external connection terminal 19 via the via 19V. In this embodiment, the external connection terminal 19 is illustrated as being provided in the surface layer of the multilayer substrate, but this is an example, and a part or all of it may be provided in the back layer of the multilayer substrate.

[0081] Also, a ground terminal 20 is provided near the surface mounting terminal 18 and is connected to the sub-ground conductor pattern 15 via the via 20V. This via 20V may penetrate the sub-ground conductor pattern 15 and be directly connected to the ground conductor 12.

[0082] Furthermore, a surface mounting region 21 may be provided in a part of the cover conductor pattern 14. These surface mounting terminals 18, ground terminals 20, and surface mounting regions 21 constitute so-called connection pads that are connected to the signal processing circuit when the signal processing circuit is mounted on the multilayer substrate. The geometric arrangement of the surface mounting terminals 18, ground terminals 20, and surface mounting regions 21 in a plan view is determined according to the connection terminal positions of the signal processing circuit to be mounted. The surface mounting terminals 18 are connected to the differential input / output terminals of the signal processing circuit, and the ground terminals 20 and surface mounting regions 21 are connected to the ground terminals of the signal processing circuit, respectively.

[0083] Also, the external connection terminal 19 is a connection pad for connection to an external device, for example, by wire bonding or a connector. Usually, the external connection terminal 19 is provided at an end of the multilayer substrate. Also, the length of the differential signal line 11 connecting the external connection terminal 19 and the filter region 17 may be designed arbitrarily.

[0084] Then, taking the distances in a plan view between the via 18V, which is the connection part between the surface mounting terminal 18 and the differential signal line 11, and the vias 13V-1 and 13V-2, which are the connection parts between the resonance conductor pattern 13 and the ground conductor 12, as L5 and L6, and the distance in a side view between the surface mounting terminal 18 and the differential signal line 11 as L7, it is desirable that the lengths of L5+L7 and L6+L7 are both shorter than 3 / 8 of the resonance wavelength of the resonance conductor pattern 13 or avoid lengths near an integer multiple of 1 / 2 of the resonance wavelength.

[0085] This is to prevent the common mode removed from the differential signal line 11 from becoming resonance noise and being emitted from the substrate due to the electromagnetic wave reflected by the resonance conductor pattern 13 in the transmission line between the resonance conductor pattern 13 and the signal processing circuit. Such a situation applies to each pattern when the resonance conductor pattern 13 consists of a plurality of patterns as shown in the present embodiment. Also, regarding the design such that the distance L5 - L6 between via 13V - 1 and via 13V - 2 is shorter than 3 / 8 of the resonance wavelength for each of the first resonance conductor pattern 13 - 1 and the second resonance conductor pattern 13 - 2, it is as already described in the fourth embodiment.

[0086] FIG. 25 is an external view of an optical transceiver 900 according to the ninth embodiment of the present invention, and FIG. 26 is a schematic diagram showing the internal structure of the optical transceiver 900. The optical transceiver 900 shown in FIG. 25 is an optical conversion adapter that converts an optical signal input and output using an optical fiber in optical communication and an electrical differential signal processed in an electronic device with each other. An optical fiber adapter 22 into which an optical fiber plug to which an optical fiber cable is connected at one end is inserted, and a part of a multilayer substrate 3 electrically connected to an electronic device at the other end is visible. The optical fiber adapter 22, the multilayer substrate 3, and other components of the optical transceiver 900 are integrally housed in a case 2.

[0087] Generally, in an optical transceiver 900 as shown here, the case 2 is made of metal, and signal pads, GND pads, pads for various controls and power supplies are arranged on the surface of the multilayer substrate 3 extending and exposed from one end thereof. By inserting this optical transceiver 900 into a connector provided in various devices such as a router or a network switch, electrical signals can be input and output. These optical transceivers 900 are known, for example, in form factors such as QSFP, OSFP, etc.

[0088] FIG. 26 schematically shows the internal configuration of Case 2. An optical connector 24 is attached to one end of the optical fiber 23, and this optical connector 24 is attached to the optical fiber adapter 22, enabling the exchange of optical input / output signals with an optical fiber plug (not shown). In this example, the optical connector 24 is provided with a total of four optical fibers 23, two for input and two for output.

[0089] The other end of the optical fiber 23 forms an optical fiber block 25, which enables accurate and stable adhesion and fixation to the optical circuit board 26. The optical transceiver 900 includes a light source package 27. The light source package 27 may be one in which a laser element is mounted, such as within a commonly used CAN package. The optical fiber 28 is for optical output. One end thereof is connected to the light source package 27, and the other end also forms an optical fiber block 29, which enables accurate and stable adhesion and fixation to the optical circuit board 26. The lead pins of the light source package 27 are electrically connected to the connection pads of the multilayer substrate 3, enabling control of the supply current to the generated laser element and temperature control.

[0090] The optical circuit board 26 converts optical input / output signals and electrical signals. As a specific example of its configuration, on the optical circuit board 26, optical waveguides, electrical lines, etc. are precisely patterned. When outputting light, the light output from the light source package 27 and introduced into the optical circuit board 26 is guided through the optical waveguide to the patterned Mach-Zehnder modulator for optical modulation. The modulated light is output from the optical fiber adapter 22 as an optical output signal through the optical fiber block 25. When inputting light, an optical waveguide and a photodiode are patterned on the optical circuit board 26. The light input through the optical fiber block 25 is guided through the optical waveguide to the photodiode, converting the received optical signal into an electrical signal.

[0091] Pads are provided on the optical circuit board 26, and signals are electrically connected to the differential signal lines 11 and the ground conductor on the multilayer substrate 3 via wires. In addition to signals, various controls, power supplies, etc. are also electrically connected to the pads on the multilayer substrate 3 using wires. However, for simplicity of illustration, the illustration is omitted in FIG. 26.

[0092] Also, various digital electrical elements (not shown) may be mounted on the multilayer substrate 3, which are responsible for various functions such as shaping and amplifying the electrical signals to be transmitted or received. These various digital electrical elements may generally be those referred to as CDR, MUX, DEMUX, DSP, etc.

[0093] In addition, a signal processing circuit 30 is mounted on the multilayer substrate 3, which extracts the electrical signals input and output to and from the optical circuit board 26 as differential signals, and performs signal conversion, shaping, etc. for sending them in. The right side portion of the signal processing circuit 30 on the multilayer substrate 3 in FIG. 26 is the common mode filter 800 in the previous eighth embodiment, and the differential signal lines 11, the ground conductor, and the cover conductor pattern formed in the internal layers below the first layer of the multilayer substrate 3 are connected to the signal processing circuit 30 by the surface mounting terminals, ground terminals, surface mounting regions, etc. that have already been described.

[0094] Also, the right side portion of the common mode filter 800 serves as an electrical connector that protrudes from the case 2 of the optical transceiver 900, and the external connection terminals 19 formed on at least one of the surface layer and the back layer of the multilayer substrate 3 (the surface layer in the illustrated example) serve as differential signal pads for connection to external devices. Further, the cover conductor pattern 14 extends in a comb-like shape to the right side edge of the multilayer substrate 3 in FIG. 26 and serves as a GND pad. The cover conductor pattern 14 covers the differential signal lines 11 passing through the inner layer of the multilayer substrate 3 in a plan view. Four pairs of differential signal lines 11 are shown here, which correspond to two pairs for electrical signal input and two pairs for output. Generally, common mode filters are often provided for two pairs of outputs, but they may be provided for two pairs of inputs depending on the purpose. And these differential signal lines 11 are covered by a common cover conductor pattern 14. That is, the cover conductor pattern 14 may not only cover a part of one pair of differential signal lines 11, but may also cover a plurality of pairs of differential signal lines 11, or may cover a part of the differential signal lines 11 where the common mode filter 800 is not provided. In this embodiment, the cover conductor pattern 14 is shown in the surface layer for ease of explanation, but actually, a further pattern layer may be formed on the cover conductor pattern 14 without any problem.

[0095] And, as already described, since the common mode filter 800 has a filter region provided at a position close to the signal processing circuit 30 in the optical transceiver 900, it suppresses the common mode noise included in the input or output signal passing through the differential signal lines 11, contributing to the stability of the communication quality.

[0096] In the ninth embodiment described above, an example is shown in which the common mode filter 800 is provided between the signal processing circuit 30 in the optical transceiver 900 and the pads for electrical connection to various devices such as routers and network switches. However, the common mode filters 100 to 800 according to the embodiments disclosed in this specification are not limited to such usage examples and can be suitably used in differential signal lines connecting between driver elements, amplifier elements, and digital electrical elements, and other arbitrary differential signal lines.

Description of Symbols

[0097] 1 Filter component, 2 Case, 3 Multilayer substrate, 10 Dielectric layer, 11 Differential signal line, 12 Ground conductor, 13 Resonant conductor pattern, 13-1 First resonant conductor pattern, 13-2 Second resonant conductor pattern, 13V-1 to 13V-6 Via, 13C-1, 13C-2 Connection part, 14 Cover conductor pattern, 14V-1 to 14V-8 Via, 15 Sub-ground conductor pattern, 15V-1 to 15V-4 Via, 16 Insulation gap, 17 Filter region, 18 Surface mounting terminal, 18V Via, 19 External connection terminal, 19V Via, 20 Ground terminal, 20V Via, 21 Surface mounting region, 22 Optical fiber adapter, 23 Optical fiber, 24 Optical connector, 25 Optical fiber block, 26 Optical circuit board, 27 Light source package, 28 Optical fiber, 29 Optical fiber block, 30 Signal processing circuit, 100 to 800 Common mode filter, 900 Optical transceiver.

Claims

1. A pair of differential signal lines formed in a multilayer substrate having a dielectric layer, A ground conductor formed in a layer below the pair of differential signal lines, A resonance conductor pattern formed in the same layer or an upper layer as the ground conductor, covering a region of a part of the pair of differential signal lines in a plan view, and connected to the ground conductor, A cover conductor pattern formed in a layer above the pair of differential signal lines, covering the resonance conductor pattern in a plan view, and connected to the ground conductor, A common mode filter having the above.

2. The common mode filter according to claim 1, wherein the resonance conductor pattern is composed of a plurality of patterns having different geometric shapes from each other or different relative connection positions with respect to the ground conductor.

3. In any two patterns included in the plurality of patterns, the distance in a plan view between the connection position with the ground conductor in one pattern and the connection position with the ground conductor in the other pattern is shorter than 3 / 8 of the resonance wavelength for each of the two patterns. The common mode filter according to claim 2.

4. One pattern and another pattern included in the plurality of patterns are formed in different layers, and at least a part of them overlaps in a plan view. The common mode filter according to claim 2.

5. One pattern included in the plurality of patterns is formed in a layer below the differential signal lines, and another pattern is formed in a layer above the differential signal lines. The common mode filter according to claim 2.

6. The common mode filter according to claim 5, wherein the one pattern is connected to the ground conductor via a via, and the other pattern is connected to the cover conductor pattern via a via.

7. Having a secondary ground conductor pattern formed in the same layer as the resonance conductor pattern, surrounding the resonance conductor, and connected to the ground conductor, The resonance conductor pattern is partitioned from the secondary ground conductor pattern with an insulating gap and separated from the secondary ground conductor pattern within the same layer. The common mode filter according to claim 1.

8. A common-mode filter according to claim 1, having a sub-ground conductor pattern formed in the same layer as the resonance conductor pattern, surrounding the resonance conductor pattern, and connected to the ground conductor, wherein the resonance conductor pattern is partitioned from the sub-ground conductor pattern with an insulating gap and is connected to the sub-ground conductor pattern at least at one side of the resonance conductor pattern.

9. The common-mode filter according to claim 1, wherein the resonance conductor pattern is formed in the same layer as the ground conductor, partitioned from the ground conductor with an insulating gap, and is connected to the ground conductor at least at one side of the resonance conductor pattern.

10. The common-mode filter according to claim 1, wherein the number of connection points between the cover conductor pattern and the ground conductor is larger than the number of connection points between the resonance conductor pattern and the ground conductor.

11. One end of the differential signal line is connected to a surface-mounting terminal formed on the surface layer of the multilayer substrate via a via, and the other end is connected to an external connection terminal formed on at least one of the surface layer and the back surface layer via a via. The common-mode filter according to any one of claims 1 to 10.

12. The length obtained by adding the distance in a plan view between the via connecting the differential signal line and the surface-mounting terminal and the connection position between the resonance conductor pattern and the ground conductor and the distance in a side view between the differential signal line and the surface-mounting terminal is shorter than 3 / 8 of the resonance wavelength of the resonance conductor pattern. The common-mode filter according to claim 11.

13. The common-mode filter according to claim 11, a signal processing circuit mounted on the multilayer substrate via the surface-mounting terminal, a photoelectric conversion circuit mounted on the multilayer substrate and connected to the signal processing circuit, and an optical fiber connector optically connected to the photoelectric conversion circuit. A transceiver having the above components.

14. The common-mode filter according to claim 12, a signal processing circuit mounted on the multilayer substrate via the surface-mounting terminal, a photoelectric conversion circuit mounted on the multilayer substrate and connected to the signal processing circuit, and an optical fiber connector optically connected to the photoelectric conversion circuit. A transceiver having the above components.

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