Communication device

Abstract

The present invention provides a communication device equipped with a common-mode noise filter and improved heat resistance. [Solution] A communication device that performs data transmission using a differential transmission method comprises: a first common-mode noise filter including a first coil, a second coil, and a third coil; a communication control circuit that transmits and receives signals through a first line connected to the first coil and a second line connected to the second coil; and at least one resistor whose first end is connected to the third coil, whose second end is connected to GND, and which is located outside the first common-mode noise filter.

Description

Technical Field

[0001] The present disclosure relates to a communication device.

Background Art

[0002] Suppression of reflection of common mode noise is required. Patent Document 1 discloses the following common node noise filter. That is, a first signal coil inserted and connected to one differential signal line is formed in a spiral shape in a multilayer dielectric layer, and a second signal coil inserted and connected to the other differential signal line is formed in the dielectric layer so as to face the first signal coil through the dielectric layer. In the dielectric layer, a control coil wound in the same direction as the first signal coil is formed so as to be sandwiched between the first and second signal coils through the dielectric layer. A built-in resistor is connected to at least one of the outer peripheral end or the inner peripheral end of the control coil. A feedback loop circuit is formed by the control coil and the built-in resistor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, since Patent Document 1 has a configuration in which a built-in resistor is provided inside the common mode noise filter, in the generation of common mode noise or an immunity test, etc., the built-in resistor may not be able to withstand the heat generated by the current flowing through the built-in resistor.

[0005] An object of the present disclosure is to provide a communication device provided with a common mode noise filter and having improved heat generation resistance.

Means for Solving the Problems

[0006] One aspect of the present disclosure provides a communication device for performing data transmission using a differential transmission method, comprising: a common-mode noise filter including a first coil, a second coil, and a third coil; a communication control circuit for transmitting and receiving signals through a line connected to the first coil and a line connected to the second coil; and a resistor whose first end is connected to the third coil, whose second end is connected to GND, and which is located outside the common-mode noise filter. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a communication device equipped with a common-mode noise filter and improved heat resistance. [Brief explanation of the drawing]

[0008] [Figure 1] A diagram showing an example of the configuration of the communication system according to Embodiment 1. [Figure 2] Figure 1 shows a graph illustrating the pass characteristics of the differential transmission path in a configuration where resistors 51A and 51B are not present in the communication device 10A shown in Figure 1. [Figure 3] Figure 1 shows a graph illustrating the pass characteristics of a differential transmission line in a configuration where resistors 51A and 51B are placed in the communication device 10A. [Figure 4] Figure 1 shows the configuration of communication system 1A, and the graph shows the current flowing through resistors 51A and 51B when the resistance values ​​of resistors 51A and 51B are 0.1Ω. [Figure 5] Figure 1 shows the current flowing through resistors 51A and 51B when the resistance values ​​of resistors 51A and 51B are 1Ω in the configuration of the communication system 1A shown in Figure 1. [Figure 6] Figure 1 shows the current flowing through resistors 51A and 51B when the resistance values ​​of resistors 51A and 51B are 50Ω in the configuration of communication system 1A shown in Figure 1. [Figure 7] Figure 1 shows the configuration of communication system 1A, and the graph shows the current flowing through resistors 51A and 51B when the resistance values ​​of resistors 51A and 51B are 100Ω. [Figure 8] Figure 1 shows the current flowing through resistors 51A and 51B when the resistance values ​​of resistors 51A and 51B are 1kΩ in the configuration of the communication system 1A shown in Figure 1. [Figure 9] Figure 1 shows the configuration of communication system 1A, and the graph shows the current flowing through resistors 51A and 51B when the resistance values ​​of resistors 51A and 51B are 10kΩ. [Figure 10] This figure shows a first modified example of the configuration of the CMNF and resistor according to Embodiment 1. [Figure 11] This figure shows a second modified example of the configuration of the CMNF and resistor according to Embodiment 1. [Figure 12] A diagram showing an example of the configuration of the communication system according to Embodiment 2. [Figure 13] Figure 12 shows a graph illustrating the pass characteristics of the differential transmission path in a configuration where resistors 51A and 51B of the communication device 10C are not present. [Figure 14] Figure 12 shows a graph illustrating the pass characteristics of a differential transmission path in a configuration where resistors 51A and 51B are placed in the communication device 10C. [Figure 15] Figure 12 shows the current flowing through resistors 51A and 51B when the resistance values ​​of resistors 51A and 51B are 0.1Ω in the configuration of communication system 1B. [Figure 16] Figure 12 shows the current flowing through resistors 51A and 51B when the resistance values ​​of resistors 51A and 51B are 1Ω in the configuration of the communication system 1B shown in Figure 12. [Figure 17] Figure 12 shows the current flowing through resistors 51A and 51B when the resistance values ​​of resistors 51A and 51B are 50Ω in the configuration of the communication system 1B shown in Figure 12. [Figure 18] Figure 12 shows the current flowing through resistors 51A and 51B when the resistance values ​​of resistors 51A and 51B are 100Ω in the configuration of communication system 1B. [Figure 19]In the configuration of the communication system 1B shown in FIG. 12, a graph showing the current values flowing through resistors 51A and 51B when the resistance values of resistors 51A and 51B are 1 kΩ [Figure 20] In the configuration of the communication system 1B shown in FIG. 12, a graph showing the current values flowing through resistors 51A and 51B when the resistance values of resistors 51A and 51B are 10 kΩ

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with appropriate reference to the drawings. However, a more detailed description may be omitted as necessary. For example, detailed descriptions of well-known matters and duplicate descriptions of substantially the same configurations may be omitted. This is to avoid making the following description unnecessarily redundant and to facilitate the understanding of those skilled in the art. Note that the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0010] (Embodiment 1) FIG. 1 is a diagram showing an example of the configuration of a communication system according to Embodiment 1. Note that FIG. 1 shows the configuration of an equivalent circuit of the communication system.

[0011] The communication system 1A includes a communication device 10A and a communication device 10B. The communication device 10A and the communication device 10B are connected by a transmission cable and perform data transmission and reception by a differential transmission method through the transmission cable.

[0012] The communication system 1A may be used when connecting an in-vehicle camera mounted on a vehicle and an Electronic Control Unit (ECU) with a transmission cable. Alternatively, the communication system 1A may be used in various systems that connect two or more electronic devices with a transmission cable.

[0013] The communication device 10A includes a communication control circuit 11A, lines 31A and 31B, a CMNF 20A, and resistors 51A and 51B. CMNF stands for Common Mode Noise Filter. The common mode noise filter may be interpreted as a common mode choke coil.

[0014] The communication control circuit 11A is a circuit that controls the transmission and reception of data using a differential transmission method. The communication control circuit 11A may be a semiconductor integrated circuit, such as a Large Scale Integration (LSI), Application Specific Integrated Circuit (ASIC), Field Programmable Gate Array (FPGA), etc. Although not described herein, the communication control circuit 11A may be connected to a predetermined processor and controlled by that processor.

[0015] CMNF20A includes coils 21A, 21B, and 21C. Coils 21A and 21B are wound in the same direction. Coils 21A, 21B, and 21C are configured to be magnetically coupled to each other. The physical configuration of CMNF20A may be such that coils 21A, 21B, and 21C are stacked via a dielectric layer or a magnetic layer, as disclosed in Patent Document 1.

[0016] The first end of the line 31A is connected to the communication control circuit 11A, and the second end of the line 31A is connected to the first end of the coil 21A of the CMNF 20A.

[0017] The first end of the line 31B is connected to the communication control circuit 11A, and the second end of the line 31B is connected to the first end of the coil 21B of the CMNF 20A.

[0018] The communication device 10B includes a communication control circuit 11B, lines 33A and 33B, CMNF 20B, and resistors 52A and 52B.

[0019] Since the communication control circuit 11B is the same as the communication control circuit 11A, its explanation will be omitted.

[0020] CMNF20B includes coils 22A, 22B, and 22C. Coils 22A, 22B, and 22C are configured to be magnetically coupled to each other. The physical configuration of CMNF20B may be such that each coil 22A, 22B, and 22C is stacked via a dielectric layer or a magnetic layer, as disclosed in Patent Document 1.

[0021] The first end of line 32A is connected to the communication control circuit 11B, and the second end of line 32A is connected to the first end of coil 22A of CMNF20B.

[0022] The first end of the line 32B is connected to the communication control circuit 11B, and the second end of the line 32B is connected to the first end of the coil 22B of the CMNF 20B.

[0023] Communication device 10A and communication device 10B are connected by transmission lines 33A and 33B, which constitute a transmission cable.

[0024] The first end of track 33A is connected to the second end of coil 21A of CMNF20A, and the second end of track 33A is connected to the second end of coil 22A of CMNF20B.

[0025] The first end of track 33B is connected to the second end of coil 21B of CMNF20A, and the second end of track 33B is connected to the second end of coil 22B of CMNF20B.

[0026] The line 31A, coil 21A of CMNF20A, line 33A, coil 22A of CMNF20B, and line 32A may be referred to as the first transmission line. The line 31B, coil 21B of CMNF20A, line 33B, coil 22B of CMNF20B, and line 32B may be referred to as the second transmission line. The first and second transmission lines together may be referred to as a differential transmission line.

[0027] Communication control circuits 11A and 11B transmit and receive data using a differential transmission method with a first transmission path and a second transmission path. CMNF20A and CMNF20B may be common-mode noise filters for the Mipi C-PHY. Therefore, a maximum communication speed of approximately 6 Gbps may be achieved between communication control circuits 11A and 11B.

[0028] When data is transmitted from communication control circuit 11A to communication control circuit 11B, communication control circuit 11A may be referred to as the transmitting unit and communication control circuit 11B as the receiving unit. When data is transmitted from communication control circuit 11B to communication control circuit 11A, communication control circuit 11B may be referred to as the transmitting unit and communication control circuit 11A as the receiving unit.

[0029] By providing CMNF20A and CMNF20B, the emission of common-mode noise from lines 33A and 33B can be suppressed. However, reflection of common-mode noise may occur in lines 31A and 31B between CMNF20A and the communication control circuit 11A, or in lines 32A and 32B between CMNF20B and the communication control circuit 11B, and as a result, at least one of lines 31A, 31B, 32A, and 32B may emit common-mode noise. Since the emission of common-mode noise adversely affects the operation of nearby electronic circuits, etc., suppression is required. Furthermore, emission tests are performed to test whether such emission of common-mode noise is suppressed. In this embodiment, a communication device that can suppress the emission of common-mode noise by suppressing the occurrence of reflection of common-mode noise will be described. A detailed explanation follows below.

[0030] As described above, CMNF20A includes coil 21C in addition to coils 21A and 21B. Furthermore, the first end of coil 21C is connected to the first end of resistor 51A. The second end of resistor 51A is connected to GND. The second end of coil 21C is connected to the first end of resistor 51B. The second end of resistor 51B is connected to GND. Resistors 51A and 51B are located outside CMNF20A, not inside it. The resistance values ​​of resistor 51A and resistor 51B may be equal. However, the resistance values ​​of resistor 51A and resistor 51B may be different. The resistance value of one of resistors 51A or 51B may be 0Ω.

[0031] As described above, CMNF20B includes coil 22C in addition to coils 22A and 22B. Furthermore, the first end of coil 22C is connected to the first end of resistor 52A. The second end of resistor 52A is connected to GND. The second end of coil 22C is connected to the first end of resistor 52B. The second end of resistor 52B is connected to GND. Resistors 52A and 52B are located outside CMNF20B, not inside it. The resistance values ​​of resistor 52A and resistor 52B may be equal. However, the resistance values ​​of resistor 52A and resistor 52B may be different. The resistance value of one of resistors 52A or 52B may be 0Ω.

[0032] Next, we will explain the operation of CMNF20A with resistors 51A and 51B. Note that the operation of CMNF20B with resistors 52A and 52B is the same as that of CMNF20A with resistors 51A and 51B, so we will omit the explanation.

[0033] In differential mode, coils 21A and 21B of CMNF20A have opposite polarities, so their potentials cancel each other out, and the average potential of coils 21A and 21B becomes zero.

[0034] In common mode, both coils 21A and 21B of CMNF20A have the same polarity, so the average potential of coils 21A and 21B is not zero. Therefore, the electromagnetic field corresponding to this is applied to coil 21C, generating an induced electromotive force in coil 21C. This induced electromotive force causes common mode noise to be generated as a current in coil 21C. The current generated in coil 21C is dissipated as heat in resistors 51A and 51B connected to the outside of CMNF20A. As a result, the common mode noise is absorbed and reduced, thus suppressing the reflection of common mode noise that conventionally occurred between CMNF20A and the communication control circuit 11A.

[0035] In addition, in this embodiment, since resistors 51A and 51B are located outside the CMNF20A, even if heat generation increases compared to the case where the resistors are located inside the CMNF20A, it is less likely to affect the CMNF20A. In other words, with the configuration shown in Figure 1, it is possible to realize communication devices 10A and 10B equipped with a common-mode noise filter with improved heat resistance.

[0036] <Verification of transmission characteristics> Next, referring to Figures 2 and 3, we will explain how the configurations of communication devices 10A and 10B shown in Figure 1 have little effect on the pass characteristics of the differential transmission line.

[0037] Figure 2 is a graph showing the pass characteristics of the differential transmission path in a configuration where resistors 51A and 51B are not placed in the communication device 10A as shown in Figure 1. Figure 3 is a graph showing the pass characteristics of the differential transmission path in a configuration where resistors 51A and 51B are placed in the communication device 10A as shown in Figure 1. In the graphs shown in Figures 2 and 3, the horizontal axis represents frequency, and the vertical axis represents the strength of the pass characteristics of Sdd21. Figure 3 is also a graph when the resistance values ​​of resistors 51A and 51B are 50Ω.

[0038] Comparing Figure 2 and Figure 3, there is almost no change in the transmission characteristics when resistors 51A and 51B are not present compared to when they are present. In other words, it can be seen that the presence of resistors 51A and 51B has almost no effect on the transmission characteristics.

[0039] <Verification of resistance values> Next, referring to Figures 4 to 9, the relationship between the resistance values ​​of resistors 51A and 51B and the effect of suppressing common-mode noise will be explained.

[0040] Figure 4 is a graph showing the current flowing through resistors 51A and 51B when their resistance values ​​are 0.1Ω in the configuration of communication system 1A shown in Figure 1. Figure 5 is a graph showing the current flowing through resistors 51A and 51B when their resistance values ​​are 1Ω in the configuration of communication system 1A shown in Figure 1. Figure 6 is a graph showing the current flowing through resistors 51A and 51B when their resistance values ​​are 50Ω in the configuration of communication system 1A shown in Figure 1. Figure 7 is a graph showing the current flowing through resistors 51A and 51B when their resistance values ​​are 100Ω in the configuration of communication system 1A shown in Figure 1. Figure 8 is a graph showing the current flowing through resistors 51A and 51B when their resistance values ​​are 1kΩ in the configuration of communication system 1A shown in Figure 1. Figure 9 is a graph showing the current flowing through resistors 51A and 51B when the resistance values ​​of resistors 51A and 51B are 10kΩ in the configuration of communication system 1A shown in Figure 1. In the graphs shown in Figures 4 to 9, the horizontal axis represents frequency and the vertical axis represents current value (amperes).

[0041] As shown in Figures 4 to 8, in the case where the resistance values ​​of resistors 51A and 51B are 0.1Ω to 1kΩ, when common-mode noise of 100MHz or higher occurs, an induced electromotive force is generated in coil 21C, and current flows through resistors 51A and 51B. In other words, it can be seen that the reflection of common-mode noise is suppressed because the common-mode noise is dissipated as heat by resistors 51A and 51B.

[0042] It can be seen that even relatively small resistance values, such as 0.1Ω, for resistors 51A and 51B connected to coil 21C of CMNF20A are sufficient to suppress the reflection of common-mode noise.

[0043] As shown in Figure 9, when the resistance values ​​of resistors 51A and 51B are 10kΩ, it can be seen that almost no current flows through resistors 51A and 51B.

[0044] In other words, in the configuration of the communication device 10A shown in Figure 1, the resistance values ​​of resistors 51A and 51B may be greater than 0Ω and less than or equal to 1kΩ. However, the resistance values ​​of resistors 51A and 51B are not limited to this range. The same applies to resistors 52A and 52B of the communication device 10B.

[0045] <Variation> Figure 10 shows a first modified example of the configuration of the CMNF and resistor according to Embodiment 1. Figure 10 also shows the equivalent circuit configuration of the CMNF and resistor.

[0046] As shown in Figure 10, the CMNF20C includes coils 21A, 21B, and 21C, as well as coil 21D. Coils 21A and 21B are wound in the same direction. Coils 21A, 21B, 21C, and 21D are configured to be magnetically coupled to one another.

[0047] As in Figure 1, resistors 51A and 51B are connected to coil 21C. Resistors 51A and 51B are located outside CMNF20C.

[0048] The first end of coil 21D is connected to the first end of resistor 53A. The second end of resistor 51A is connected to GND. The second end of coil 21D is connected to the first end of resistor 53B. The second end of resistor 53B is connected to GND. Resistors 53A and 53B are located outside the CMNF20C, not inside it.

[0049] In this configuration, in common mode, an electromagnetic field is applied to coils 21C and 21D, generating induced electromotive forces in coils 21C and 21D. The current generated in coils 21C and 21D by these induced electromotive forces is dissipated as heat in resistors 51A, 51B, 53A, and 53B, which are connected to the outside of CMNF20C. As a result, as in the case of Figure 1 described above, the reflection of common-mode noise can be suppressed.

[0050] Figure 11 shows a second modified example of the configuration of the CMNF and resistor according to Embodiment 1. Figure 11 also shows the equivalent circuit configuration of the CMNF and resistor.

[0051] As shown in Figure 11, the first end of the coil 21C of the CMNF20A shown in Figure 1 may be connected to GND via resistor 51A and also via capacitor 59A. The second end of the coil 21C of the CMNF20A may be connected to GND via resistor 51B and also via capacitor 59B.

[0052] In this configuration, the current generated in coil 21C by the induced electromotive force is consumed by resistors 51A and 51B, and capacitors 59A and 59B. As a result, as in the case of Figure 1 described above, reflection of common-mode noise can be suppressed.

[0053] (Embodiment 2) Figure 12 shows an example of the configuration of the communication system 1B according to Embodiment 2. Note that Figure 12 also shows the equivalent circuit configuration of the communication system 1B.

[0054] The communication system 1B according to Embodiment 2 differs from the communication system 1A according to Embodiment 1 shown in Figure 1 in that it further includes reflective CMNF60A and CMNF60B. In Embodiment 2, components already described in Embodiment 1 are given common reference numerals and their descriptions may be omitted.

[0055] The communication device 10C includes a reflective CMNF 60A located between the communication control circuit 11A and the CMNF 20A. That is, if the part closer to the communication control circuit 11A with respect to the CMNF 20A is considered the "pre-stage" and the part further away from the communication control circuit 11A is considered the "post-stage," then the reflective CMNF 60A is positioned before the CMNF 20A. The communication device 10C further includes lines 34A and 34B.

[0056] The reflective CMNF60A includes coils 61A and 61B. Coils 61A and 61B are wound in the same direction and configured to be magnetically coupled to each other.

[0057] The first end of the line 34A is connected to the communication control circuit 11A, and the second end of the line 34A is connected to the first end of the coil 61A of the reflective CMNF 60A.

[0058] The first end of the line 34B is connected to the communication control circuit 11A, and the second end of the line 34B is connected to the first end of the coil 61B of the reflective CMNF 60A.

[0059] The first end of track 31A is connected to the second end of coil 61A of reflective CMNF60A, and the second end of track 31A is connected to the first end of coil 21A of CMNF20A.

[0060] The first end of track 31B is connected to the second end of coil 61B of reflective CMNF60A, and the second end of track 31B is connected to the first end of coil 21B of CMNF20A.

[0061] The communication device 10D includes a reflective CMNF 60B located between the communication control circuit 11B and the CMNF 20B. That is, if the part of the CMNF 20B closer to the communication control circuit 11B is considered the "preceding stage" and the part further away from the communication control circuit 11B is considered the "postceding stage," then the reflective CMNF 60B is positioned in front of the CMNF 20B. The communication device 10D further includes lines 35A and 35B.

[0062] The reflective CMNF60B includes coils 62A and 62B. Coils 62A and 62B are wound in the same direction and configured to be magnetically coupled to each other.

[0063] The first end of the line 35A is connected to the communication control circuit 11B, and the second end of the line 35A is connected to the first end of the coil 62A of the reflective CMNF 60B.

[0064] The first end of the line 35B is connected to the communication control circuit 11B, and the second end of the line 35B is connected to the first end of the coil 62B of the reflective CMNF 60B.

[0065] The first end of track 32A is connected to the second end of coil 62A of the reflective CMNF60B, and the second end of track 32A is connected to the first end of coil 22A of CMNF20B.

[0066] The first end of track 32B is connected to the second end of coil 62B of reflective CMNF60B, and the second end of track 32B is connected to the first end of coil 22B of CMNF20B.

[0067] Line 34A, coil 61A for reflective CMNF60A, line 31A, coil 21A for CMNF20A, line 33A, coil 22A for CMNF20B, line 32A, coil 62A for reflective CMNF60B, and line 35A may be referred to as the first transmission line. Line 34B, coil 61B for reflective CMNF60A, line 31B, coil 21B for CMNF20A, line 33B, coil 22B for CMNF20B, line 32B, coil 62B for reflective CMNF60B, and line 35B may be referred to as the second transmission line. The first and second transmission lines may be collectively referred to as a differential transmission line.

[0068] By providing the reflective CMNF60A, common-mode noise directed toward the communication control circuit 11A in lines 31A and 31B is reflected by the reflective CMNF60A and returned to the CMNF20A. The reflected common-mode noise is dissipated as heat in resistors 51A and 52A connected to the coil 21C of the CMNF60A, as described in Embodiment 1. Therefore, the configuration of the communication device 10C equipped with the reflective CMNF60A shown in Figure 12 can suppress the radiation of common-mode noise more effectively than the configuration of the communication device 10A shown in Figure 1. The same applies to the communication device 10B equipped with the reflective CMNF60B.

[0069] <Verification of transmission characteristics> Next, referring to Figures 13 and 14, we will explain how the configurations of communication devices 10C and 10D shown in Figure 12 have little effect on the transmission characteristics of the differential transmission line.

[0070] Figure 13 is a graph showing the pass-through characteristics of the differential transmission path in a configuration where resistors 51A and 51B are not present in the communication device 10C as shown in Figure 12. Figure 14 is a graph showing the pass-through characteristics of the differential transmission path in a configuration where resistors 51A and 51B are present in the communication device 10C as shown in Figure 12. In the graphs shown in Figures 13 and 14, the horizontal axis represents frequency, and the vertical axis represents the strength of the pass-through characteristics. Figure 14 is also a graph showing the case where the resistance values ​​of resistors 51A and 51B are 50Ω.

[0071] Comparing Figure 13 and Figure 14, there is almost no change in the pass-through characteristics when resistors 51A and 51B are not present compared to when they are present. In other words, it can be seen that the presence of resistors 51A and 51B has almost no effect on the pass-through characteristics.

[0072] <Verification of resistance values> Next, referring to Figures 15 to 20, the relationship between the resistance values ​​of resistors 51A and 51B and the effect of suppressing common-mode noise will be explained.

[0073] Figure 15 is a graph showing the current flowing through resistors 51A and 51B when their resistance values ​​are 0.1Ω in the configuration of communication system 1B shown in Figure 12. Figure 16 is a graph showing the current flowing through resistors 51A and 51B when their resistance values ​​are 1Ω in the configuration of communication system 1B shown in Figure 12. Figure 17 is a graph showing the current flowing through resistors 51A and 51B when their resistance values ​​are 50Ω in the configuration of communication system 1B shown in Figure 12. Figure 18 is a graph showing the current flowing through resistors 51A and 51B when their resistance values ​​are 100Ω in the configuration of communication system 1B shown in Figure 12. Figure 19 is a graph showing the current flowing through resistors 51A and 51B when their resistance values ​​are 1 kΩ in the configuration of communication system 1B shown in Figure 12. Figure 20 is a graph showing the current flowing through resistors 51A and 51B when their resistance values ​​are 10 kΩ in the configuration of communication system 1B shown in Figure 12. In the graphs shown in Figures 15 to 20, the horizontal axis represents frequency and the vertical axis represents current value (amperes).

[0074] As shown in Figures 15 to 19, in the case where the resistance values ​​of resistors 51A and 51B are 0.1Ω to 1kΩ, when common-mode noise of 100MHz or higher occurs, an induced electromotive force is generated in coil 21C, and current flows through resistors 51A and 51B. In other words, it can be seen that the reflection of common-mode noise is suppressed because the common-mode noise is dissipated as heat by resistors 51A and 51B.

[0075] Furthermore, compared to the graphs in Figures 4 to 8, the graphs in Figures 15 to 19 show that more current flows through resistors 51A and 51B. From this, it can be seen that by including the reflective CMNF60A as shown in Figure 12, more common-mode noise reflection can be suppressed compared to the configuration without the reflective CMNF60A as shown in Figure 1.

[0076] It can be seen that even relatively small resistance values, such as 0.1Ω, for resistors 51A and 51B connected to coil 21C of CMNF20A are sufficient to suppress the reflection of common-mode noise.

[0077] As shown in Figure 20, when the resistance values ​​of resistors 51A and 51B are 10kΩ, it can be seen that almost no current flows through resistors 51A and 51B.

[0078] In other words, in the configuration of the communication device 10C shown in Figure 12, the resistance values ​​of resistors 51A and 51B may be greater than 0Ω and less than or equal to 1kΩ. However, the resistance values ​​of resistors 51A and 51B are not limited to this range. The same applies to resistors 52A and 52B of the communication device 10D.

[0079] <Variation> The communication system 1B is not limited to the configuration shown in Figure 12, and may be configured in any of the following (A1) to (A2). As mentioned above, with respect to CMNF20A, the side closer to the communication control circuit 11A is referred to as the "front stage," and the side further away from the communication control circuit 11A is referred to as the "back stage." With respect to CMNF20B, the side closer to the communication control circuit 11B is referred to as the "front stage," and the side further away from the communication control circuit 11B is referred to as the "back stage."

[0080] (A1) In the communication device 10C, the reflective CMNF60A may be placed after the CMNF20A. (A2) In the communication device 10D, the reflective CMNF60B may be placed after the CMNF20B.

[0081] (Summary of this disclosure) The following technologies are disclosed in accordance with the above description in this disclosure.

[0082] <Technology 1> A communication device (10A) for performing data transmission by differential transmission according to one aspect of the present disclosure comprises: a first common-mode noise filter (20A) including a first coil (21A), a second coil (21B), and a third coil (21C); a communication control circuit (11A) for sending and receiving signals through a first line (31A) connected to the first coil and a second line (31B) connected to the second coil; and at least one resistor (51A, 51B) whose first end is connected to the third coil and whose second end is connected to GND, and which is located outside the first common-mode noise filter. As a result, the induced electromotive force generates common-mode noise as a current in the third coil. The current generated in the third coil is dissipated as heat in the resistor. Consequently, the common-mode noise is absorbed and reduced. In addition, since the resistor is located outside the first common-mode noise filter, the heat generated by the resistor is less likely to affect the first common-mode noise filter. Therefore, a communication device with improved heat resistance and a common-mode noise filter can be realized.

[0083] <Technology 2> In the communication device described in Technical 1, the at least one resistor includes a first resistor (51A) connected to the first end of the third coil and a second resistor (52B) connected to the second end of the third coil. This allows for effective absorption and reduction of common-mode noise.

[0084] <Technology 3> In the communication device described in Technical 2, the resistance value of the first resistor and the resistance value of the second resistor are equal. This allows for effective absorption and reduction of common-mode noise.

[0085] <Technology 4> In the communication device described in Technical 3, the resistance value of the first resistor is greater than 0Ω and less than or equal to 1kΩ. This allows for effective absorption and reduction of common-mode noise signals.

[0086] <Technology 5> A communication device according to any one of Technology 1 to Technology 4 further comprises a second common-mode noise filter (60A) which is located in a preceding stage closer to the communication control circuit (11A) than the first common-mode noise filter, or in a subsequent stage further away from the communication control circuit (11A) than the first common-mode noise filter, and which includes at least two coils (61A, 61B). As a result, common-mode noise is reflected by the second common-mode noise filter and returned to the first common-mode noise filter. The reflected common-mode noise is then dissipated as heat by the resistor connected to the third coil of the first common-mode noise filter. Therefore, common-mode noise can be further absorbed and reduced.

[0087] While embodiments have been described above with reference to the attached drawings, this disclosure is not limited to such examples. It is clear to those skilled in the art that various modifications, alterations, substitutions, additions, deletions, and equivalents can be conceived within the scope of the claims, and these are also understood to fall within the technical scope of this disclosure. Furthermore, the components of the embodiments described above can be combined in any way without departing from the spirit of the invention. [Industrial applicability]

[0088] The technology disclosed herein is useful for suppressing common-mode noise. [Explanation of symbols]

[0089] 1A, 1B Communication System 10A,10B,10C,10D Communication device 11A, 11B Communication Control Circuit 20A, 20B, 20C CMNF 21A, 21B, 21C, 21D, 22A, 22B, 22C, 61A, 61B, 62A, 62B coils 31A,31B,32A,32B,33A,33B,34A,34B,35A,35B track 51A,51B,52A,52B,53A,53B Resistor 59A, 59B Capacitors 60A,60B Reflective CMNF

Claims

1. A communication device that performs data transmission using a differential transmission method, A first common-mode noise filter including a first coil, a second coil, and a third coil, A communication control circuit that transmits and receives signals through a first line connected to the first coil and a second line connected to the second coil, The device comprises at least one resistor, the first end of which is connected to the third coil, the second end of which is connected to GND, and which is located outside the first common-mode noise filter. Communication device.

2. The at least one resistor includes a first resistor connected to the first end of the third coil and a second resistor connected to the second end of the third coil. The communication device according to claim 1.

3. The resistance value of the first resistor and the resistance value of the second resistor are equal. The communication device according to claim 2.

4. The resistance value of the first resistor is greater than 0 Ω and less than or equal to 1 kΩ. The communication device according to claim 3.

5. The system further comprises a second common-mode noise filter, which is positioned either before the first common-mode noise filter (closer to the communication control circuit) or after the first common-mode noise filter (further from the communication control circuit), and includes at least two coils. A communication device according to any one of claims 1 to 4.

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