Transmission line structure

Abstract

To more effectively reduces noise generated in a transmission path.SOLUTION: A transmission line structure includes a first transmission line and a second transmission line electrically connecting two devices, a first shield covering at least a portion of the first transmission line in the direction of a current flowing through the first transmission line, a second shield covering at least a portion of the second transmission line in the direction of a current flowing through the second transmission line, and a first conductor and a second conductor electrically connecting between the first shield and the second shield.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a transmission line structure. [Background technology]

[0002] Patent Document 1 discloses a transmission line structure in an electric field communication device capable of performing electric field communication by inducing an electric field in an electric field transmission medium. The transmission line structure includes a first electrode for electric field communication used for contacting the electric field transmission medium, a second electrode for electric field communication having the same volume and shape as the first electrode, a first transmission line having one connection end connected to the first electrode, a second transmission line having the same material and length as the first transmission line and one connection end connected to the second electrode, and a receiving differential amplifier having a first input end connected to the other connection end of the first transmission line and a second input end connected to the other connection end of the second transmission line, amplifying and outputting the difference between the signals input from the first input end and the second input end, respectively. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-74606 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure has been devised in view of the above-mentioned conventional circumstances, and has an object to provide a transmission line structure that more effectively reduces noise generated in the transmission line. [Means for solving the problem]

[0005] The present disclosure provides a transmission line structure comprising: a first transmission line and a second transmission line electrically connecting two devices; a first shield covering at least a portion of the first transmission line along a direction of a current flowing through the first transmission line; a second shield covering at least a portion of the second transmission line along a direction of a current flowing through the second transmission line; and a first conductor and a second conductor electrically connecting between the first shield and the second shield. Effect of the Invention

[0006] According to the present disclosure, noise occurring in a transmission path can be reduced more effectively. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing a first example of a transmission line structure according to a first embodiment; [Diagram 2] Top view of the first transmission line structure [Diagram 3] FIG. 1 is a diagram showing an example of normal noise and common noise in a first transmission line structure; [Figure 4] FIG. 1 is a diagram showing a second example of a transmission line structure according to the first embodiment; [Diagram 5] FIG. 13 is a diagram showing an example of normal noise and common noise in a second transmission line structure. [Figure 6] FIG. 13 is a diagram showing a third example of a transmission line structure according to the first embodiment; [Figure 7] FIG. 13 is a diagram showing an example of normal noise and common noise in a third transmission line structure. [Figure 8] FIG. 13 is a diagram showing a fourth example of a transmission line structure according to the first embodiment; [Figure 9] FIG. 13 is a diagram showing an example of normal noise and common noise in a fourth transmission line structure. [Figure 10] FIG. 13 is a diagram showing a fifth example of a transmission line structure according to the second embodiment; [Figure 11] FIG. 13 is a diagram showing an example of normal noise and common noise in the fifth transmission line structure. [Figure 12] FIG. 13 is a diagram showing a sixth example of a transmission line structure according to the second embodiment; [Figure 13] FIG. 13 is a diagram showing an example of normal noise and common noise in a sixth transmission line structure. [Figure 14] FIG. 13 is a diagram showing a seventh example of a transmission line structure according to the second embodiment; [Figure 15] FIG. 13 is a diagram showing an example of normal noise and common noise in the seventh transmission line structure. [Figure 16] FIG. 1 shows an example of a conventional transmission line structure. [Figure 17] FIG. 1 is a diagram showing an example of normal noise and common noise in a conventional transmission line structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] (Background to this disclosure) Generally, in order to remove noise superimposed on a signal line or a power line, a bypass capacitor is inserted between the signal line etc. and the ground line, or an inductor (coil) is inserted in series with the signal line etc. In this way, the electric circuit can remove noise by dissipating the noise superimposed on the signal line etc. to the ground line via the bypass capacitor with low high-frequency impedance, or by blocking the propagation of noise in the signal line etc. with a coil with high high-frequency impedance.

[0009] In Patent Document 1, a second noise component equivalent to a first noise component generated between a first electrode and a first input terminal is generated between a second electrode and a second input terminal, and the first noise component is removed by the second noise component, thereby reducing the first noise component generated between the first electrode and the first input terminal.

[0010] In addition, in the past, in an environment where it is difficult to connect a signal line or a power line to the earth ground, there is a transmission line structure that includes two wirings W01, W02 that electrically connect two devices MC01, MC02, shields SH01, SH02 that suppress noise emitted from the two wirings W01, W02, and wirings W03, W04 that let the return current flowing through these shields SH01, SH02 escape to the devices MC01, MC02, as shown in FIG. 16. Here, FIG. 16 is a diagram showing an example of a conventional transmission line structure. In the transmission line structure shown in FIG. 16, the length of the wirings W01, W02 that connect the devices MC01 and MC02 is 1200 mm, and the shields SH01, SH02 are the same length. Also, the distances between both ends of the shields SH01, SH02 and the devices MC01, MC02 are equal.

[0011] However, in such a transmission line structure, the wirings W03 and W04 each function as a pigtail, which reduces the noise suppression effect of the shields SH01 and SH02. Figure 17 shows the normal noise and common noise generated by the transmission line structure shown in Figure 16. Figure 17 is a diagram showing an example of normal noise and common noise in a conventional transmission line structure.

[0012] The noise waveforms of normal noise shown in Fig. 17 include a noise waveform NN01 when the length of the shields SH01 and SH02 is 600 mm, a noise waveform NN02 when the length of the shields SH01 and SH02 is 800 mm, a noise waveform NN03 when the length of the shields SH01 and SH02 is 1000 mm, and a noise waveform NN04 when the length of the shields SH01 and SH02 is 1190 mm. The noise waveforms of common noise shown in Fig. 17 include a noise waveform CN01 when the length of the shields SH01 and SH02 is 600 mm, a noise waveform CN02 when the length of the shields SH01 and SH02 is 800 mm, a noise waveform CN03 when the length of the shields SH01 and SH02 is 1000 mm, and a noise waveform CN04 when the length of the shields SH01 and SH02 is 1190 mm.

[0013] Hereinafter, with reference to the drawings as appropriate, an embodiment specifically disclosing a transmission line structure according to the present disclosure will be described in detail. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or duplicate explanation of substantially the same configuration may be omitted. This is to avoid the following explanation becoming unnecessarily redundant and to facilitate understanding by those skilled in the art. Note that the attached drawings and the following explanation are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0014] (Embodiment 1) The first to fourth transmission line structures shown in the first embodiment have a transmission line that connects two devices MC1 and MC2 with two wires W1 and W2 each having a length of 1200 m (=L1, see FIG. 2) to transmit power or signals. In the first to fourth transmission line structures, this transmission line is configured without being grounded. It goes without saying that the lengths of the wires W1 and W2 are merely examples and are not limited to these. Furthermore, the device MC1 is a switching power supply with a switching frequency of 100 MHz to 120 MHz, and supplies power to the device MC2. The device MC2 is driven by the power supplied from the device MC1.

[0015] <First transmission line structure> The first transmission line structure in the first embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a diagram showing an example of the first transmission line structure according to the first embodiment. Fig. 2 is a diagram showing the first transmission line structure as seen from above.

[0016] The wires W1 and W2 in the first transmission line structure are partially covered by the shields SH1 and SH2, respectively. The shields SH1 and SH2 have a length L2 along the current or signal transmission direction, and both ends along the current or signal transmission direction are connected by the wires W31 and W41, respectively.

[0017] Each of the wirings W31, W41 is a conductor and conducts a current or a signal propagating through one of the shields SH1, SH2 to the other. As a result, in the first transmission line structure, a magnetic field of an opposite phase is generated by a current flowing in the opposite directions through the two shields SH1, SH2 via the wirings W31, W41, and this cancels out the magnetic field of a positive phase generated by the wirings W1, W2, thereby reducing normal noise and common noise generated from the transmission line.

[0018] Normal noise and common noise generated in the first transmission line structure will be described with reference to Fig. 3. Fig. 3 is a diagram showing an example of normal noise and common noise in the first transmission line structure.

[0019] Noise waveforms NN11, NN12, NN13, and NN14 each show normal noise occurring in the first transmission line structure. Noise waveform NN11 shows normal noise when length L2 is 600 mm. Noise waveform NN12 shows normal noise when length L2 is 800 mm. Noise waveform NN13 shows normal noise when length L2 is 1000 mm. Noise waveform NN14 shows normal noise when length L2 is 1190 mm.

[0020] The normal noise in the first transmission line structure shifts the normal noise peak to the higher frequency side compared to the conventional example. The first transmission line structure can reduce normal noise in the vicinity of the fundamental frequencies of 100 MHz to 120 MHz of the devices MC1 and MC2, and can also reduce normal noise over a wide frequency band (30 MHz to 480 MHz).

[0021] Noise waveforms CN11, CN12, CN13, and CN14 each show common noise generated in the first transmission line structure. Noise waveform CN11 shows common noise when length L2 is 600 mm. Noise waveform CN12 shows common noise when length L2 is 800 mm. Noise waveform CN13 shows common noise when length L2 is 1000 mm. Noise waveform CN14 shows common noise when length L2 is 1190 mm.

[0022] The first transmission line structure can reduce common noise in the fundamental frequency band of 100 MHz to 330 MHz of the devices MC1 and MC2 compared to the conventional example. Moreover, the first transmission line structure can reduce common noise regardless of the length L2 of the shields SH1 and SH2.

[0023] As described above, the first transmission line structure can reduce normal noise and common noise generated from the transmission line by shortening the length of the wiring W1, W2 exposed from each of the shields SH1, SH2 (i.e., lengthening the length L2 of the shields SH1, SH2). Also, the first transmission line structure can further reduce noise in the vicinity of the fundamental frequency of 100 MHz to 120 MHz of the devices MC1, MC2 by shortening the length of the wiring W1, W2 exposed from each of the shields SH1, SH2.

[0024] <Second transmission line structure> The second transmission line structure in the first embodiment will be described with reference to Fig. 4. Fig. 4 is a diagram showing an example of the second transmission line structure according to the first embodiment. Note that a description of the same configuration as the first transmission line structure will be omitted.

[0025] The length L1 of each of the wires W1 and W2 in the second transmission line structure is 1200 mm, and the length L2 of each of the shields SH1 and SH2 is 1190 mm.

[0026] Each of the wires W32 and W42 in the second transmission line structure electrically connects to each of the shields SH1 and SH2 at a position spaced apart from both ends of the wires W1 and W2 by a distance L31. Each of the wires W32 and W42 is a conductor and conducts a current or a signal propagating through one of the shields SH1 and SH2 to the other. As a result, each of the two shields SH1 and SH2 in the second transmission line structure and each of the two wires W32 and W42 function as a loop antenna that loops a current or a signal.

[0027] Normal noise and common noise generated in the second transmission line structure will be described with reference to Fig. 5. Fig. 5 is a diagram showing an example of normal noise and common noise in the second transmission line structure.

[0028] 5 shows normal noise and common noise when the distance L31 between both ends of the wirings W1, W2 and the wirings W32, W42 is changed to 100 mm, 200 mm, 300 mm, 400 mm, and 500 mm. The antenna length of the loop antenna formed by the shields SH1, SH2 and the wirings W32, W42 becomes shorter as the distance L31 increases.

[0029] Noise waveforms NN21, NN22, NN23, NN24, and NN25 each show normal noise occurring in the second transmission path structure. Noise waveform NN21 shows normal noise when the distance L31 is 100 mm. Noise waveform NN22 shows normal noise when the distance L31 is 200 mm. Noise waveform NN23 shows normal noise when the distance L31 is 300 mm. Noise waveform NN24 shows normal noise when the distance L31 is 400 mm. Noise waveform NN25 shows normal noise when the distance L31 is 500 mm.

[0030] In the second transmission line structure, the normal noise peak is shifted to the higher frequency side compared to the conventional example, and the normal noise near the fundamental frequency of 100 MHz to 120 MHz of each of the devices MC1 and MC2 can be reduced. In the second transmission line structure, the normal noise peak can be shifted to the higher frequency side as the distance L31 becomes smaller, that is, as the antenna length of the loop antenna becomes larger.

[0031] Noise waveforms CN21, CN22, CN23, CN24, and CN25 each show common noise occurring in the second transmission line structure. Noise waveform CN21 shows common noise when the distance L31 is 100 mm. Noise waveform CN22 shows common noise when the distance L31 is 200 mm. Noise waveform CN23 shows common noise when the distance L31 is 300 mm. Noise waveform CN24 shows common noise when the distance L31 is 400 mm. Noise waveform CN25 shows common noise when the distance L31 is 500 mm.

[0032] The second transmission line structure can reduce common noise over a wide frequency band (100 MHz to 330 MHz) compared to the conventional example. Moreover, the second transmission line structure can reduce common noise regardless of the length of the distance L31.

[0033] As described above, the second transmission line structure can increase the distance between the wiring W32 and the wiring W42 connected to the shields SH1 and SH2, that is, reduce the magnitude of the distance L31, so that the antenna length of the loop antenna covered by the shields SH1 and SH2 can be increased compared to the loop antenna formed in the transmission line in which the wiring W1 and W2 include exposed parts. As a result, the second transmission line structure can increase the reverse current flowing through each of the shields SH1 and SH2 via the wiring W32 and W42, and can reduce normal noise generated from the transmission line by canceling the positive-phase magnetic field generated by the wiring W1 and W2. In addition, when the length L2 of the shields SH1 and SH2 is fixed, the second transmission line structure can reduce noise near the fundamental frequency of 100 MHz to 120 MHz of the devices MC1 and MC2 and over a wide frequency band (100 MHz to 330 MHz) by increasing the distance between the wiring W32 and the wiring W42.

[0034] <Third transmission line structure> A third transmission line structure in the first embodiment will be described with reference to Fig. 6. Fig. 6 is a diagram showing an example of a third transmission line structure according to the first embodiment. Note that a description of the same configuration as the first transmission line structure will be omitted.

[0035] The length L1 (not shown) of each of the wires W1 and W2 in the third transmission line structure is 1200 mm, and the length L2 of each of the shields SH1 and SH2 is 1190 mm.

[0036] The shields SH1 and SH2 in the third transmission line structure are electrically connected by three wirings W31, W41, and W51, respectively. Specifically, each of the two wirings W31 and W41 connects both ends of the shields SH1 and SH2. The wiring W51 is a conductor, and is disposed between the wirings W31 and W41 in the direction in which a current or a signal flows through the wirings W1 and W2, connecting the shields SH1 and SH2. Each of the three wirings W31, W41, and W51 conducts a current or a signal propagating through one of the shields SH1 and SH2 to the other.

[0037] As a result, in the third transmission line structure, a current flows in the transmission line formed by the two shields SH1, SH2 and the two wires W31, W51 connecting between these shields SH1 and SH2, in a direction opposite to that of the current flowing through the wires W1, W2. In the third transmission line structure, a magnetic field of opposite phase is generated by the reverse current, which cancels out the positive phase magnetic field generated by the wires W1, W2, thereby reducing normal noise and common noise generated from the transmission line.

[0038] Normal noise and common noise occurring in the third transmission line structure will be described with reference to Fig. 7. Fig. 7 is a diagram showing an example of normal noise and common noise in the third transmission line structure.

[0039] FIG. 7 shows normal noise and common noise when the distance L51 between the center position of the shields SH1, SH2 in the direction of current or signal flow and the connection position of the wiring W51 is changed to 0 (zero) mm, 200 mm, 300 mm, 400 mm, and 500 mm.

[0040] Noise waveforms NN31, NN32, NN33, NN34, and NN35 each show normal noise occurring in the third transmission path structure. Noise waveform NN31 shows normal noise when the distance L51 is 0 (zero) mm. Noise waveform NN32 shows normal noise when the distance L51 is 200 mm. Noise waveform NN33 shows normal noise when the distance L51 is 300 mm. Noise waveform NN34 shows normal noise when the distance L51 is 400 mm. Noise waveform NN35 shows normal noise when the distance L51 is 500 mm.

[0041] In the third transmission line structure, the normal noise peak shifts to the high frequency side when the distance L51 is 0 (zero) mm to 400 mm, and the normal noise near the fundamental frequency of 100 MHz to 120 MHz of each of the devices MC1 and MC2 can be reduced, compared to the conventional example. In the third transmission line structure, the normal noise can be reduced over a wide frequency band (100 MHz to 480 MHz) compared to the conventional example. In addition, in the third transmission line structure, the normal noise peak shifts to the low frequency side as the distance L51 increases.

[0042] Noise waveforms CN31, CN32, CN33, CN34, and CN35 each show common noise generated in the third transmission line structure. Noise waveform CN31 shows common noise when the distance L51 is 0 (zero) mm. Noise waveform CN32 shows common noise when the distance L51 is 200 mm. Noise waveform CN33 shows common noise when the distance L51 is 300 mm. Noise waveform CN34 shows common noise when the distance L51 is 400 mm. Noise waveform CN35 shows common noise when the distance L51 is 500 mm.

[0043] Compared to the conventional example, the third transmission line structure can reduce common noise over a wide frequency band (100 MHz to 330 MHz), particularly in the vicinity of the fundamental frequency of 100 MHz to 120 MHz.

[0044] As described above, compared to the second transmission line structure, the third transmission line structure increases the number of wirings connecting between the shield SH1 and the shield SH2, thereby making it possible to reduce the loop length of each loop antenna formed by each of the wirings W31, W41, and W51, and therefore it is possible to more effectively reduce normal noise peaks over a wide frequency band (100 MHz to 330 MHz) and further reduce the number of peaks that occur.

[0045] Furthermore, in the third transmission path structure, when the length L2 of the shields SH1, SH2 and the connection position between the wiring W31 and wiring W41 connecting the shields SH1 and SH2 are fixed, by further connecting the intermediate position between the shields SH1 and SH2 (i.e., the intermediate position between the wiring W31 and wiring W41) with wiring W51, the loop length of the loop antenna formed by the shields SH1, SH2 and the wiring W31, W51 and the loop antenna formed by the shields SH1, SH2 and the wiring W41, W51 become the same, thereby suppressing the formation of a loop antenna with a large loop length and more effectively reducing noise generated in each loop antenna.

[0046] <The fourth transmission line structure> A fourth transmission line structure in the first embodiment will be described with reference to Fig. 8. Fig. 8 is a diagram showing an example of a fourth transmission line structure according to the first embodiment. Note that a description of the same configuration as the first transmission line structure will be omitted.

[0047] The length L1 (not shown) of each of the wires W1 and W2 in the fourth transmission line structure is 1200 mm, and the length L2 of each of the shields SH1 and SH2 is 1190 mm.

[0048] The shields SH1 and SH2 in the fourth transmission line structure are electrically connected by four wirings W31, W41, W52, and W53, respectively. Specifically, each of the two wirings W31 and W41 connects both ends of the shield SH1 and the shield SH2. The wirings W52 and W53 are conductors, and are disposed between the wirings W31 and W41 in the direction in which a current or a signal flows through the wirings W1 and W2, connecting the shield SH1 and the shield SH2. Each of the four wirings W31, W41, W52, and W53 conducts a current or a signal propagating through one of the shields SH1 and SH2 to the other.

[0049] Normal noise and common noise generated in the fourth transmission line structure will be described with reference to Fig. 9. Fig. 9 is a diagram showing an example of normal noise and common noise in the fourth transmission line structure.

[0050] 9 shows normal noise and common noise when the distance L52 between the wires W52 and W53 is changed to 0 (zero) mm, 200 mm, 300 mm, 400 mm, and 500 mm. The wires W52 and W53 are disposed at equal intervals from the center positions of the shields SH1 and SH2 in the direction in which the current or signal flows. When the distance L52 is 0 (zero) mm, the fourth transmission line structure is the same as the third transmission line structure.

[0051] Noise waveforms NN41, NN42, NN43, NN44, and NN45 each show normal noise occurring in the fourth transmission path structure. Noise waveform NN41 shows normal noise when distance L52 is 0 (zero) mm. Noise waveform NN42 shows normal noise when distance L52 is 200 mm. Noise waveform NN43 shows normal noise when distance L52 is 300 mm. Noise waveform NN44 shows normal noise when distance L52 is 400 mm. Noise waveform NN45 shows normal noise when distance L52 is 500 mm.

[0052] In the fourth transmission line structure, the normal noise peak shifts to the higher frequency side when the distance L52 is 0 (zero) mm to 300 mm, compared to the conventional example. Moreover, in the fourth transmission line structure, the normal noise peak is reduced and the magnitude of the normal noise can be reduced over a wide frequency band (100 MHz to 480 MHz) regardless of the distance L52, compared to the conventional example.

[0053] Noise waveforms CN41, CN42, CN43, CN44, and CN45 each show common noise occurring in the fourth transmission line structure. Noise waveform CN41 shows common noise when distance L52 is 0 (zero) mm. Noise waveform CN42 shows common noise when distance L52 is 200 mm. Noise waveform CN43 shows common noise when distance L52 is 300 mm. Noise waveform CN44 shows common noise when distance L52 is 400 mm. Noise waveform CN45 shows common noise when distance L52 is 500 mm.

[0054] Compared to the conventional example, the fourth transmission line structure can reduce common noise over a wide frequency band (100 MHz to 330 MHz), particularly in the vicinity of the fundamental frequency of 100 MHz to 120 MHz.

[0055] As described above, compared to the third transmission line structure, the fourth transmission line structure increases the number of wirings connecting between the shield SH1 and the shield SH2, thereby making it possible to reduce the loop length of each loop antenna formed by each of the wirings W31, W41, W52, and W53, and therefore more effectively reduce normal noise peaks over a wide frequency band (100 MHz to 330 MHz) and further reduce the number of peaks that occur.

[0056] In addition, in the fourth transmission path structure, as the distance L52 approaches 500 mm, the loop lengths of each loop antenna formed by the four wirings W31, W41, W52, and W53 become more equal. In other words, the formation of a loop antenna with a large loop length can be suppressed, and the noise generated in each loop antenna can be more effectively reduced.

[0057] (Embodiment 2) The transmission line structure according to the first embodiment is an example in which the transmission line is not grounded. The transmission line structure according to the second embodiment is an example in which the transmission line is grounded to earth ground GND. In the following description, earth ground GND is not limited to the earth (ground) and may be read as a reference ground plane provided in a device (inside a machine).

[0058] <Fifth Transmission Line Structure> A fifth transmission line structure in the second embodiment will be described with reference to Fig. 10. Fig. 10 is a diagram showing an example of a fifth transmission line structure according to the second embodiment. Note that a description of the same configuration as the first transmission line structure will be omitted.

[0059] The length L1 (not shown) of each of the wires W1 and W2 in the fifth transmission line structure is 1200 mm.

[0060] In the fifth transmission line structure, both ends of the shields SH1 and SH2 along the direction in which a current or a signal flows are electrically connected by two wirings W31 and W41, respectively. Each of the two wirings W31 and W41 conducts a current or a signal propagating through one of the shields SH1 and SH2 to the other. Each of the wirings W31 and W41 is connected to the earth ground GND by each of the wirings W61 and W71, respectively. Each of the wirings W61 and W71 conducts a current or a signal propagating through the wirings W31 and W41 to the earth ground GND.

[0061] Normal noise and common noise occurring in the fifth transmission line structure will be described with reference to Fig. 11. Fig. 11 is a diagram showing an example of normal noise and common noise in the fifth transmission line structure.

[0062] FIG. 11 shows normal noise and common noise when the length L2 (see FIG. 2) of the shields SH1, SH2 is changed to 600 mm, 800 mm, 1170 mm, and 1190 mm.

[0063] Noise waveforms NN51, NN52, NN53, NN54, and NN55 each show normal noise occurring in the fifth transmission line structure. Noise waveform NN51 shows normal noise when length L2 is 600 mm. Noise waveform NN52 shows normal noise when length L2 is 800 mm. Noise waveform NN53 shows normal noise when length L2 is 1000 mm. Noise waveform NN54 shows normal noise when length L2 is 1170 mm. Noise waveform NN55 shows normal noise when length L2 is 1190 mm.

[0064] In the fifth transmission line structure, the normal noise peak shifts to the higher frequency side and the peak value can be further reduced compared to the conventional example. Moreover, in the fifth transmission line structure, the normal noise can be reduced in magnitude over a wide frequency band (100 MHz to 480 MHz) regardless of the length L2 compared to the conventional example.

[0065] Noise waveforms CN51, CN52, CN53, CN54, and CN55 each show common noise generated in the fifth transmission line structure. Noise waveform CN51 shows common noise when length L2 is 600 mm. Noise waveform CN52 shows common noise when length L2 is 800 mm. Noise waveform CN53 shows common noise when length L2 is 1000 mm. Noise waveform CN54 shows common noise when length L2 is 1170 mm. Noise waveform CN55 shows common noise when length L2 is 1190 mm.

[0066] Compared with the conventional example, the fifth transmission line structure can more stably reduce common noise in the vicinity of the fundamental frequency of 100 MHz to 120 MHz of the devices MC1 and MC2.

[0067] As described above, the fifth transmission line structure can reduce normal noise and common noise generated from the transmission line by shortening the length of the wiring W1, W2 exposed from each of the shields SH1, SH2 (i.e., lengthening the length L2 of the shields SH1, SH2). Also, the fifth transmission line structure can further reduce noise in the vicinity of the fundamental frequency of 100 MHz to 120 MHz of the devices MC1, MC2 by shortening the length of the wiring W1, W2 exposed from each of the shields SH1, SH2.

[0068] <Sixth Transmission Line Structure> A sixth transmission line structure in the second embodiment will be described with reference to Fig. 12. Fig. 12 is a diagram showing an example of a sixth transmission line structure according to the second embodiment. Note that a description of the same configuration as the first and fifth transmission line structures will be omitted.

[0069] The length L1 (not shown) of each of the wires W1 and W2 in the sixth transmission line structure is 1200 mm.

[0070] In the sixth transmission line structure, both ends of the shields SH1 and SH2 along the direction in which a current or a signal flows are electrically connected by two wirings W31 and W41, respectively. Each of the two wirings W31 and W41 conducts a current or a signal propagating through one of the shields SH1 and SH2 to the other. The wiring W31 is connected to the earth ground GND by a wiring W61. The wiring W61 conducts a current or a signal propagating through the wiring W31 to the earth ground GND.

[0071] Normal noise and common noise occurring in the sixth transmission line structure will be described with reference to Fig. 13. Fig. 13 is a diagram showing an example of normal noise and common noise in the sixth transmission line structure.

[0072] FIG. 13 shows normal noise and common noise when the length L2 (see FIG. 2) of the shields SH1, SH2 is changed to 600 mm, 800 mm, 1170 mm, and 1190 mm.

[0073] Noise waveforms NN61, NN62, NN63, NN64, and NN65 each show normal noise occurring in the sixth transmission line structure. Noise waveform NN61 shows normal noise when length L2 is 600 mm. Noise waveform NN62 shows normal noise when length L2 is 800 mm. Noise waveform NN63 shows normal noise when length L2 is 1000 mm. Noise waveform NN64 shows normal noise when length L2 is 1170 mm. Noise waveform NN65 shows normal noise when length L2 is 1190 mm.

[0074] The normal noise in the sixth transmission line structure has a peak shifted to the higher frequency side compared to the conventional example. Compared to the conventional example, the sixth transmission line structure can reduce normal noise over a wide frequency band (100 MHz to 480 MHz), particularly in the vicinity of a fundamental frequency of 100 MHz to 120 MHz.

[0075] Noise waveforms CN61, CN62, CN63, CN64, and CN65 each show common noise generated in the sixth transmission line structure. Noise waveform CN61 shows common noise when length L2 is 600 mm. Noise waveform CN62 shows common noise when length L2 is 800 mm. Noise waveform CN63 shows common noise when length L2 is 1000 mm. Noise waveform CN64 shows common noise when length L2 is 1170 mm. Noise waveform CN65 shows common noise when length L2 is 1190 mm.

[0076] Compared with the conventional example, the sixth transmission line structure can more stably reduce common noise in the vicinity of the fundamental frequency of 100 MHz to 120 MHz of the devices MC1 and MC2.

[0077] As described above, in the sixth transmission line structure, by connecting the transmission line to the earth ground GND via the wiring W61, common noise can be reduced more stably compared to the conventional example, even when the length L1 of the shields SH1, SH2 is short.

[0078] <Seventh Transmission Line Structure> The seventh transmission line structure in the second embodiment will be described with reference to Fig. 14. Fig. 14 is a diagram showing an example of the seventh transmission line structure according to the second embodiment. Note that a description of the same configuration as the sixth transmission line structure will be omitted.

[0079] The length L1 (not shown) of each of the wires W1 and W2 in the seventh transmission line structure is 1200 mm.

[0080] The wiring W41 in the seventh transmission line structure is connected to the earth ground GND by a wiring W71. The wiring W71 conducts a current or a signal propagating through the wiring W41 to the earth ground GND.

[0081] Normal noise and common noise occurring in the seventh transmission line structure will be described with reference to Fig. 15. Fig. 15 is a diagram showing an example of normal noise and common noise in the seventh transmission line structure.

[0082] FIG. 15 shows normal noise and common noise when the length L2 (see FIG. 2) of the shields SH1, SH2 is changed to 600 mm, 800 mm, 1170 mm, and 1190 mm.

[0083] Noise waveforms NN71, NN72, NN73, NN74, and NN75 each show normal noise occurring in the seventh transmission line structure. Noise waveform NN71 shows normal noise when length L2 is 600 mm. Noise waveform NN72 shows normal noise when length L2 is 800 mm. Noise waveform NN73 shows normal noise when length L2 is 1000 mm. Noise waveform NN74 shows normal noise when length L2 is 1170 mm. Noise waveform NN75 shows normal noise when length L2 is 1190 mm.

[0084] In the seventh transmission line structure, the normal noise peak shifts to the higher frequency side as in the sixth transmission line structure, compared to the conventional example. Compared to the conventional example, the seventh transmission line structure can reduce normal noise over a wide frequency band (100 MHz to 480 MHz), particularly in the vicinity of the fundamental frequency of 100 MHz to 120 MHz.

[0085] Noise waveforms CN71, CN72, CN73, CN74, and CN75 each show common noise generated in the seventh transmission line structure. Noise waveform CN71 shows common noise when length L2 is 600 mm. Noise waveform CN72 shows common noise when length L2 is 800 mm. Noise waveform CN73 shows common noise when length L2 is 1000 mm. Noise waveform CN74 shows common noise when length L2 is 1170 mm. Noise waveform CN75 shows common noise when length L2 is 1190 mm.

[0086] Compared with the conventional example, the seventh transmission line structure can more stably reduce common noise in the vicinity of the fundamental frequency of 100 MHz to 120 MHz of the devices MC1 and MC2.

[0087] As described above, in the seventh transmission line structure, like the sixth transmission line structure, by connecting the transmission line to earth ground GND via wiring W61, common noise can be reduced more stably than in the conventional example even when the length L1 of the shields SH1, SH2 is short.

[0088] (Additional Note) The above description of each embodiment discloses the following techniques.

[0089] (Technology 1) a first transmission line (wiring W1) and a second transmission line (wiring W2) electrically connecting the two devices MC1 and MC2; a first shield (shield SH1) that covers at least a portion of the first transmission line (wiring W1) along the direction of a current flowing through the first transmission line (wiring W1); a second shield (shield SH2) that covers at least a portion of the second transmission line (wiring W2) along the direction of a current flowing through the second transmission line (wiring W2); a first conductor (wirings W31, W32) and a second conductor (wirings W41, W42) that electrically connect the first shield (shield SH1) and the second shield (shield SH2); Transmission line structure. With this configuration, the transmission line structures according to the first and second embodiments can reduce the path length (i.e., the loop length of the loop antenna) of the current flowing between the device MC1 and the device MC2 through the wirings W1 and W2 by the multiple wirings W31 and W41 that electrically connect the shields SH1 and SH2, which generates a positive-phase magnetic field in the shields SH1 and SH2 due to the current flowing through each of the wirings W1 and W2, thereby reducing noise generated from the transmission line. In addition, the transmission line structure can reduce noise generated from the transmission line by canceling the positive-phase magnetic field generated by the wirings W1 and W2 by causing currents in opposite directions to flow through the two shields SH1 and SH2 through the wirings W31 and W41. The transmission line structures according to the first and second embodiments are particularly effective in reducing noise near the fundamental frequency of the devices MC1 and MC2.

[0090] (Technology 2) the first conductor (wirings W31 and W32) connects one end of the first shield (shield SH1) and one end of the second shield (shield SH2); the second conductor (wirings W41 and W42) connects the other end of the first shield (shield SH1) and the other end of the second shield (shield SH2); The transmission line structure described in (Technology 1). With this configuration, in the transmission line structures of embodiments 1 and 2, currents flow in opposite directions through the wiring W31, W41 over the entire length of the two shields SH1, SH2, generating an opposite-phase magnetic field over the entire length of the shields SH1, SH2, which cancels out the positive-phase magnetic field generated by the wiring W1, W2 over the entire length of the shields SH1, SH2, thereby reducing noise generated from the transmission line.

[0091] (Technology 3) the first conductor (wirings W31 and W32) connects the first shield (shield SH1) and the second shield (shield SH2) at a predetermined distance (distance L31) from one end of the first shield (shield SH1) and the second shield (shield SH2); the second conductor (wirings W41, W42) connects the first shield (shield SH1) and the second shield (shield SH2) at the predetermined distance (distance L31) from the other end of the first shield (shield SH1) and the other end of the second shield (shield SH2); The transmission line structure according to (Technology 1) or (Technology 2). With this configuration, in the transmission line structure of embodiment 1, a current flows in the opposite direction through the wirings W32, W42 over the section of the entire length of the shields SH1, SH2 that is connected by the wirings W32 and W42, generating a magnetic field of opposite phase over the section connected by the wirings W32 and W42, and canceling out the positive phase magnetic field generated by the wirings W1, W2 over the entire length of the shields SH1, SH2, thereby reducing the noise generated from the transmission line.

[0092] (Technology 4) a third conductor (wirings W51, W52) that electrically connects between the first shield (shield SH1) and the second shield (shield SH2) at a position different from the first conductor (wiring W31) and the second conductor (wiring W41); The transmission line structure according to any one of (Technology 1) to (Technology 3). With this configuration, the transmission line structure according to the first embodiment can reduce the path length (open loop) of the current flowing between the devices MC1 and MC2 using three wires, thereby reducing noise generated from the transmission line.

[0093] (Technology 5) the third conductor (wiring W51) connects a midpoint of the overall length of the first shield (shield SH1) and a midpoint of the overall length of the second shield (shield SH2); The transmission line structure described in (Technology 4). With this configuration, the transmission line structure according to embodiment 1 can reduce noise more stably by further connecting the intermediate position between the shields SH1 and SH2 (i.e., the intermediate position between the wiring W31 and the wiring W41) with the wiring W51.

[0094] (Technology 6) a fourth conductor (wiring W53) that electrically connects between the first shield (shield SH1) and the second shield (shield SH2) at a position different from the first conductor (wiring W31), the second conductor (wiring W41), and the third conductor (wiring W52), The transmission line structure according to (Technology 4) or (Technology 5). With this configuration, the transmission line structure of embodiment 1 can reduce the current path length (open loop) by increasing the number of wirings connecting between the shield SH1 and the shield SH2, thereby reducing the noise generated from the transmission line.

[0095] (Technology 7) the first conductor (wiring W31), the second conductor (wiring W41), the third conductor (wiring W52) and the fourth conductor (wiring W53) connect the first shield (shield SH1) and the second shield (shield SH2) at equal distances from each other; The transmission line structure described in (Technology 6). With this configuration, the transmission line structure of embodiment 1 can increase the number of wirings connecting between the shield SH1 and the shield SH2, making the current path lengths (open loops) uniform and more stably reducing noise generated from the transmission line.

[0096] (Technology 8) Either the first conductor (wiring W31) or the second conductor (wiring W41) is connected to the earth ground GND. The transmission line structure according to any one of (Technology 1) to (Technology 7). With this configuration, the transmission line structure according to the second embodiment can further reduce noise generated from the transmission line by propagating the current through the wiring W31 or the wiring W41 and dissipating it to the ground GND.

[0097] (Technology 9) The first conductor (wiring W31) and the second conductor (wiring W41) are connected to the earth ground. The transmission line structure according to any one of (Technology 1) to (Technology 7). With this configuration, the transmission line structure according to the second embodiment can further reduce noise generated from the transmission line by propagating the current through the wiring W31 and the wiring W41 and dissipating it to the ground GND.

[0098] Although various embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications, corrections, substitutions, additions, deletions, and equivalents within the scope of the claims, and it is understood that these also belong to the technical scope of the present disclosure. In addition, the components in the various embodiments described above may be arbitrarily combined within the scope of the invention. [Industrial Applicability]

[0099] The present disclosure is useful as a transmission line structure that more effectively reduces noise generated in a transmission line. [Explanation of symbols]

[0100] GND Earth ground MC01,MC1,MC02,MC2 equipment SH01, SH1, SH02, SH2 Shield W01, W1, W02, W2, W03, W04, W31, W32, W41, W42, W51, W52, W53, W61, W71 Wiring

Claims

1. a first transmission line and a second transmission line electrically connecting two devices; a first shield that covers at least a portion of the first transmission line along a direction of a current flowing through the first transmission line; a second shield that covers at least a portion of the second transmission line along a direction of a current flowing through the second transmission line; a first conductor and a second conductor electrically connecting between the first shield and the second shield; Transmission line structure.

2. the first conductor connects one end of the first shield and one end of the second shield; the second conductor connects the other end of the first shield to the other end of the second shield; The transmission line structure according to claim 1 .

3. the first conductor connects the first shield and the second shield at a predetermined distance from one end of the first shield and the second shield, the second conductor connects the first shield and the second shield at the predetermined distance from the other ends of the first shield and the second shield; The transmission line structure according to claim 1 .

4. a third conductor electrically connecting the first shield and the second shield at a position different from the first conductor and the second conductor; The transmission line structure according to claim 1 .

5. the third conductor connects a midpoint of the first shield to a midpoint of the second shield; The transmission line structure according to claim 4.

6. a fourth conductor electrically connecting between the first shield and the second shield at a position different from the first conductor, the second conductor, and the third conductor; The transmission line structure according to claim 4.

7. the first conductor, the second conductor, the third conductor and the fourth conductor connect the first shield and the second shield at equal distances from each other; The transmission line structure according to claim 6.

8. One of the first conductor and the second conductor is connected to earth ground. The transmission line structure according to claim 1 .

9. the first conductor and the second conductor are connected to earth ground; The transmission line structure according to claim 1 .

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