Analytic method and design method of multi-conductor transmission line system

Abstract

The invention provides an analysis method and a design method of a multi-conductor transmission line system. One or more of the plurality of conductor lines are provided with a branch portion branching from the parallel section. One or a plurality of branch parts are provided at one or a plurality of changing positions of the characteristic impedance of the plurality of conductor lines. It is assumed that each of the plurality of conductor lines is routed in such a manner that one or more change positions of the characteristic impedance are set as one or more turning points, and that the plurality of conductor lines are routed between the first end circuit network and the second end circuit network. The design value of the specific constituent element is changed so that the characteristic impedance of the specific constituent element among the plurality of constituent elements of the multi-conductor transmission line system changes.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority from Japanese Patent Application No. 2024-030142, filed on February 29, 2024, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to analytical methods and design methods for multi-conductor transmission line systems. Background Art

[0004] Examples of multi-conductor transmission line systems include automotive wiring harnesses and patterned wiring on circuit boards. Specifically, a multi-conductor transmission line system consists of a ground plane and multiple conductor lines. In multi-conductor transmission line systems, noise can become pronounced due to resonance. Japanese Patent Application Publication No. 2019-55686 discloses technology for suppressing the pronounced noise in automotive wiring harnesses.

[0005] The application of the technology in the above-mentioned document is limited to an in-vehicle wiring harness in which a plurality of wires are bundled together. Therefore, the technology in the above-mentioned document cannot be applied to a multi-conductor transmission line system having branched wires. Summary of the Invention

[0006] According to one aspect of the present disclosure, a method for analyzing a multi-conductor transmission line system is provided. The analysis method includes a technique for providing a multi-conductor transmission line system. The multi-conductor transmission line system includes a ground plane and a plurality of conductor lines. The multi-conductor transmission line system includes a parallel section. In the parallel section, the plurality of conductor lines are arranged in parallel. The plurality of conductor lines each include an end load. One or more of the plurality of conductor lines include one or more branches branching from the parallel section. The plurality of conductor lines include one or more locations where characteristic impedance changes. The one or more locations where characteristic impedance changes include one or more branches. A noise propagation model is assumed. The noise propagation model includes a uniform line group, a first end circuit network, and a second end circuit network. It is assumed that a noise signal input into the multi-conductor transmission line system propagates through the uniform line group while undergoing multiple reflections between the first end circuit network and the second end circuit network. An assumption is made regarding the wiring of the plurality of conductor lines in the noise propagation model. Assume that multiple conductor lines are wired in such a manner that one or more locations where the characteristic impedance changes serve as one or more turning points, and that the lines reciprocate between a first terminal circuit network and a second terminal circuit network. The one or more turning points each have a turning-back terminal element. A uniform line group is formed by multiple uniform lines. The multiple conductor lines each have multiple uniform lines extending between the first terminal circuit network and the second terminal circuit network. The uniform line group has a first group end corresponding to the first terminal circuit network and a second group end corresponding to the second terminal circuit network. The first terminal circuit network is formed by one or more end loads connected to the first group end and one or more turning-back terminal elements connected to the first group end. The second terminal circuit network is formed by one or more end loads connected to the second group end and one or more turning-back terminal elements connected to the second group end. The noise characteristics of a multi-conductor transmission line system are analyzed using a noise propagation model.

[0007] According to another aspect of the present disclosure, a design method for a multi-conductor transmission line system is provided. The design method includes the step of analyzing the noise characteristics of the multi-conductor transmission line system using a noise propagation model to analyze the eigenvalues ​​of multiple components of the multi-conductor transmission line system. Based on the results of the eigenvalue analysis, a specific component is extracted from the multiple components. The specific component has an eigenvalue greater than the eigenvalues ​​of other components at a problematic frequency. The design value of the specific component is changed to change the characteristic impedance of the specific component.

[0008] According to another aspect of the present disclosure, a method for designing a multi-conductor transmission line system is provided. The method includes the step of analyzing the noise characteristics of the multi-conductor transmission line system using a noise propagation model to calculate the peak frequency of noise in one or more of the multiple components of the multi-conductor transmission line system. Multiple uniform lines each have a height from a ground plane. If the peak frequency is a problematic frequency, one or more of the heights are changed.

[0009] The above-mentioned method for analyzing a multi-conductor transmission line system has the effect of enabling easy analysis of noise characteristics of a multi-conductor transmission line system having branches. The above-mentioned method for designing a multi-conductor transmission line system has the effect of facilitating efficient design of the multi-conductor transmission line system.

[0010] Noise suppression in multi-conductor transmission line systems requires analyzing noise characteristics. However, a method for easily analyzing the noise characteristics of branched multi-conductor transmission line systems is generally unavailable. Consequently, designing a multi-conductor transmission line system that suppresses significant noise is difficult. The above method can alleviate this difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a diagram schematically showing the structure of an example of a multi-conductor transmission line system.

[0012] Figure 2 yes Figure 1 Circuit diagram of the noise propagation model of noise signal propagation in a multi-conductor transmission line system.

[0013] Figure 3 This is a diagram schematically showing another configuration example of a multi-conductor transmission line system.

[0014] Figure 4 yes Figure 3 Circuit diagram of the noise propagation model of noise signal propagation in a multi-conductor transmission line system.

[0015] Figure 5 This is a diagram schematically showing still another configuration example of a multi-conductor transmission line system.

[0016] Figure 6 yes Figure 5 Circuit diagram of the noise propagation model of noise signal propagation in a multi-conductor transmission line system. DETAILED DESCRIPTION

[0017] The phrase "at least one of A and B" described in this specification should be understood to mean "only A", "only B", or "both A and B".

[0018] Figure 1 and Figure 2 An analysis method of a multi-conductor transmission line system according to one embodiment will be described.

[0019] <Structure of a multi-conductor transmission line system>

[0020] Reference Figure 1 The structure of the multi-conductor transmission line system in this embodiment will be described. The multi-conductor transmission line system is the subject of noise characteristic analysis.

[0021] Figure 1 The multi-conductor transmission line system 10 shown is constructed with a ground plane 11 and two conductor lines. The two conductor lines include a first conductor line 12 and a second conductor line 13 laid on the ground plane 11. The conductor and covering dielectric material and cross-sectional shape of the first conductor line 12 are the same as those of the second conductor line 13. The multi-conductor transmission line system 10 has a parallel section 14. In the parallel section 14, the first conductor line 12 and the second conductor line 13 are arranged adjacent to each other in parallel. The first conductor line 12 and the second conductor line 13 branch off from each other at both ends of the parallel section 14. In the following description, the first end of the parallel section 14 is referred to as a first branch portion 20, and the second end of the parallel section 14 is referred to as a second branch portion 21. The portion of the first conductor line 12 and the second conductor line 13 that branches off from the parallel section 14 and is laid out independently by the first conductor line 12 or the portion that is laid out independently by the second conductor line 13 is referred to as a single-line section.

[0022] The first end of the first conductor line 12 is grounded to the ground plane 11 via the first end load 15. The second end of the first conductor line 12 is grounded to the ground plane 11 via the third end load 17. The first end of the second conductor line 13 is grounded to the ground plane 11 via the second end load 16. The second end of the second conductor line 13 is grounded to the ground plane 11 via the fourth end load 18. Most of the first conductor line 12 and the second conductor line 13 are laid at a first height H1 from the ground plane 11. That is, most of the first conductor line 12 and the second conductor line 13 are at a certain height from the ground plane 11. The exceptional portion of the height in the first conductor line 12 and the second conductor line 13 is the portion between the second branch portion 21 in the second conductor line 13 and the fourth end load 18. The exceptional portion of the height of the second conductor line 13 is laid at a second height H2 (>H1) from the ground plane 11. For the convenience of illustration, Figure 1The length of the line extending in the direction perpendicular to the ground plane 11 among the lines representing the first conductor line 12 and the second conductor line 13 is not the physical length of the conductor lines of the first conductor line 12 and the second conductor line 13, but represents the height from the ground plane 11.

[0023] exist Figure 1 In the case of the multi-conductor transmission line system 10, a first end load 15 is located at the first end of the first conductor line 12. A noise source 19 is connected to the first end of the first conductor line 12. Noise source 19 represents, for example, a noise source included in the first end load 15. Another example of noise source 19 is an example in which the noise generated in the first conductor line 12 due to the introduction of external noise is represented as an equivalent end noise source.

[0024] Examples of the multi-conductor transmission line system 10 provided include wiring harnesses and busbar modules. The wiring harnesses and busbar modules are mounted on transportation equipment such as vehicles and aircraft. In this case, the ground plane 11 is the conductor body of the transportation equipment. The first conductor line 12 and the second conductor line 13 are wires and busbars. As another example of the multi-conductor transmission line system 10, a wiring pattern of a circuit substrate can be cited. In this case, the ground plane 11 is the GND plane of the circuit substrate. The first conductor line 12 and the second conductor line 13 are the pattern wiring of the circuit substrate.

[0025] Noise Propagation Model for Multi-Conductor Transmission Line Systems

[0026] The analysis method of this embodiment is to use Figure 2 The noise propagation model of Figure 1 The noise characteristics of the multi-conductor transmission line system 10 are analyzed. Figure 2 The noise propagation model is to Figure 1 The multi-conductor transmission line system 10 is replaced by a model of a multi-conductor transmission line system in which a plurality of lines are arranged in parallel without branches. Figure 2 The propagation of noise is modeled in a multi-conductor transmission line system.

[0027] Figure 2 Express Figure 1 The multi-conductor transmission line system 10 is replaced by a replacement circuit. Figure 2 The replacement circuit is used in the noise propagation model. Figure 2 The replacement circuit is composed of a first terminal circuit network 31, a second terminal circuit network 32, and a uniform line group 30. The uniform line group 30 is connected between the first terminal circuit network 31 and the second terminal circuit network 32. Figure 2 The replacement circuit is realized by Figure 1 The multi-conductor transmission line system 10 is produced by performing substitutions as follows.

[0028] Assume that the first conductor line 12 and the second conductor line 13 are wired in the following manner, i.e., they go back and forth between the first terminal circuit network 31 and the second terminal circuit network 32. One or more turning points of the first conductor line 12 or the second conductor line 13 in the first terminal circuit network 31 or the second terminal circuit network 32 are positions where the characteristic impedance of the first conductor line 12 or the second conductor line 13 changes. That is, at the position where the characteristic impedance changes, the characteristic impedance of the first conductor line 12 or the second conductor line 13 changes. The position where the characteristic impedance changes includes a branch portion branching from the parallel section 14, i.e., a first branch portion 20 and a second branch portion 21. In Figure 1 In the case of the multi-conductor transmission line system 10, the position where the characteristic impedance of the first conductor line 12 and the second conductor line 13 changes is provided with a first branch portion 20 and a second branch portion 21. The position where the cross-sectional shape of the conductors of the first conductor line 12 and the second conductor line 13 changes and the position where the height from the ground plane 11 changes are the positions where the characteristic impedance of the first conductor line 12 and the second conductor line 13 changes. Between the first end circuit network 31 and the second end circuit network 32, a plurality of uniform lines 33 to 39 are arranged in parallel. As described above, in the direction Figure 2 When the replacement circuit shown is performed, the first conductor line 12 and the second conductor line 13 are folded back at the location where the characteristic impedance changes. The characteristic impedance of each uniform line 33-39 is uniform throughout its entire length. Specifically, the uniform lines 33-39 are arranged in parallel between the first terminal circuit network 31 and the second terminal circuit network 32. The uniform lines 33-39 constitute a uniform line group 30. The uniform line group 30 has a first group end corresponding to the first terminal circuit network 31 and a second group end corresponding to the second terminal circuit network 32.

[0029] exist Figure 2In this case, the first terminal circuit network 31 includes the noise source 19. Therefore, the first conductor line 12 further bends at an intermediate position in the single-line section between the first terminal load 15 and the first branch 20. In the following description, this bend position is referred to as a bend point 22. The line length of the section in the first conductor line 12 between the noise source 19 and the first terminal load 15 on one side and the bend point 22 on the other side is set to be sufficiently shorter than the line length of the section between the first branch 20 and the bend point 22. Here, the first terminal load 15 and the noise source 19 are treated as a set. In this noise propagation model, the first terminal circuit network 31 is composed of the first terminal load 15, the third terminal load 17, the fourth terminal load 18, the first branch 20, and the noise source 19. The first terminal load 15, the third terminal load 17, and the fourth terminal load 18 are connected to the first group end of the uniform line group 30. The first branch 20 and noise source 19 are return terminal elements connected to the first end of the uniform line group 30. Specifically, the first terminal circuit network 31 consists of the first end load 15, the third end load 17, and the fourth end load 18 connected to the first end of the uniform line group 30, as well as the first branch 20 and noise source 19, which serve as return terminal elements and are also connected to the first end of the uniform line group 30. The second terminal circuit network 32 consists of the return point 22, the second end load 16, and the second branch 21. The first branch 20, the second branch 21, and the return point 22 are shown as short-circuit lines connecting the ends of two uniform lines 33 to 39. The second end load 16 is connected to the second end of the uniform line group 30. The second branch 21 and the return point 22 are return terminal elements connected to the second end of the uniform line group 30. That is, the second terminal circuit network 32 is composed of the second terminal load 16 connected to the second end of the uniform line group 30 , and the two branches 21 and the turning point 22 , which are the return terminal elements connected to the second end of the uniform line group 30 .

[0030] exist Figure 2 In the case of , the uniform line group 30 is composed of seven uniform lines 33 to 39 arranged in parallel. The uniform line 33 corresponds to the portion between the second branch portion 21 and the fourth end load 18 in the second conductor line 13. Figure 1In the figure, the portions corresponding to uniform lines 33 to 39 are numbered 33 to 39. Uniform line 34 corresponds to the portion of the first conductor line 12 between the second branch 21 and the third end load 17. Uniform line 35 corresponds to the portion of the second conductor line 13 between the first branch 20 and the second branch 21. Uniform line 36 corresponds to the portion of the first conductor line 12 between the first branch 20 and the second branch 21. Uniform line 37 corresponds to the portion of the second conductor line 13 between the second end load 16 and the first branch 20. Uniform line 38 corresponds to the portion of the first conductor line 12 between the turning point 22 and the first branch 20. Uniform line 39 corresponds to the portion of the first conductor line 12 between the first end load 15 and the noise source 19 on one side and the turning point 22 on the other side. Uniform lines 35 and 36 of uniform lines 33 to 39 correspond to the parallel section 14. The other uniform lines 33 to 34 and 37 to 39 correspond to single-line sections.

[0031] In this embodiment, when analyzing the noise characteristics, Figure 1 The multi-conductor transmission line system 10 shown is replaced by Figure 2 The multi-conductor transmission line system shown. Figure 1 The multi-conductor transmission line system 10 shown has conductor lines branching off from one another. Figure 2 The multi-conductor transmission line system shown does not have any branching between conductor lines. The noise characteristics are analyzed using the noise propagation model in the multi-conductor transmission line system after the replacement. Figure 2 The following analysis of noise characteristics in a multi-conductor transmission line system is presented. Figure 2 A multi-conductor transmission line system is composed of multiple transmission lines and does not branch into the multiple transmission lines. The analysis of noise characteristics in a multi-conductor transmission line system without branches is described in detail in the referenced document Clayton R. Paul, "Analysis of Multiconductor Transmission Lines," 2nd Edition, Wiley. Here, an overview of the analysis of noise characteristics in a multi-conductor transmission line system without branches is summarized for explanation. Furthermore, various calculations for the noise analysis are performed, for example, by a control device. For example, the control device includes a processing circuit and a memory storing a program that causes the processing circuit to execute operations related to the various calculations.

[0032] When analyzing noise characteristics, it is first necessary to determine the unit length impedance, propagation constant, and voltage mode conversion coefficient of each uniform line 33-39. These values ​​can be calculated based on the unit length inductance and unit length capacitance of each uniform line 33-39. The unit length inductance and unit length capacitance of each uniform line 33-39 can be calculated through electromagnetic field simulation based on the cross-sectional shape of the conductors of the uniform lines 33-39.

[0033] In this embodiment, the cross-sectional shapes of the conductors of uniform lines 33-39 are identical. Uniform lines 33-34 and 37-39 are not parallel sections, but single-line sections. If the heights from ground plane 11 are the same, the inductance per unit length of uniform lines 33-34 and 37-39 are the same. Similarly, the capacitance per unit length is the same. Uniform line 33 is laid at a second height H2 from ground plane 11. Uniform lines 34 and 37-39 are laid at a first height H1 from ground plane 11. Therefore, the impedance per unit length, propagation constant, and voltage-mode conversion coefficient of uniform lines 34 and 37-39, which have the same height from ground plane 11, other than uniform line 33, are identical. In the following description, the impedance per unit length of uniform lines 34 and 37-39 is referred to as "Z1," the propagation constant as "γ1," and the voltage-mode conversion coefficient as "Tv1." The unit-length impedance of uniform line 33 is represented by "Z3," the propagation constant by "γ3," and the voltage-mode conversion coefficient by "Tv3." Within a single-line section, the noise propagation mode is considered to be single. Therefore, formally, the values ​​of Tv1 and Tv3 are each "1."

[0034] On the other hand, uniform lines 35 and 36 form a parallel section 14. The unit length impedance, propagation constant, and voltage-mode conversion coefficient of the parallel section 14 are calculated based on the capacitive coupling and mutual inductance between the conductors of uniform lines 35 and 36. Specifically, the unit length impedance, propagation constant, and voltage-mode conversion coefficient of the parallel section 14 are calculated by modeling it as a multi-conductor transmission line system. The unit length impedance, propagation constant, and voltage-mode conversion coefficient of the parallel section 14 are expressed as a quadratic matrix. In the following description, the unit length impedance matrix of the parallel section 14 is referred to as "Z2," the propagation constant matrix is ​​referred to as "γ2," and the voltage-mode conversion coefficient matrix is ​​referred to as "Tv2." The unit length impedance, propagation constant, and voltage-mode conversion coefficient of the parallel section composed of N parallel uniform lines are expressed as an N-th order matrix.

[0035] In this embodiment, the conductor resistance of each uniform line 33-39 and the dielectric loss of the wire coating are sufficiently small. Therefore, these values ​​are ignored in the calculation of the above parameters. If more accurate calculations are required, or if the resistance and dielectric loss are too large to be ignored, the above parameters can be calculated while also taking into account the conductor resistance and dielectric loss of the wire coating.

[0036] In reality, the values ​​of the unit length impedance, propagation constant, and voltage-mode conversion coefficient exhibit frequency characteristics. However, in practice, ignoring the frequency characteristics is generally sufficient. In this embodiment, the frequency characteristics are considered only for the calculation of the unit length impedance. Specifically, the unit length impedance is calculated as a value obtained by applying frequency correction to the unit length impedance value at low frequencies. This frequency correction accounts for the skin effect.

[0037] When analyzing noise characteristics, the first terminal circuit network 31 and the second terminal circuit network 32 need to be expressed as a mode reflection coefficient matrix. The mode reflection coefficient matrix is ​​expressed as follows.

[0038] First, the first terminal circuit network 31 is represented by the admittance matrices Y1 and Y2 as shown in equations (1) and (2). The diagonal elements of the admittance matrix Y1 are configured with the admittances 1 / Za, 1 / Zc, and 1 / Zd of the first terminal load 15, the third terminal load 17, and the fourth terminal load 18 contained in the first terminal circuit network 31. The load element that connects the uniform lines 33 to 39 in the first terminal circuit network 31 is a connecting load element. The admittance 1 / st of the connecting load element is configured as a diagonal element in the admittance matrix Y1. The sign-reversed value (-1 / st) of the admittance of the connecting load element is configured as a non-diagonal element in the admittance matrix Y1. The portion surrounded by the dotted line in the equation corresponds to the above-mentioned connecting load element. The first terminal circuit network 31 has a connecting load element between the uniform lines 33 to 39. The connected load elements between uniform lines 33 to 39 in the first terminal circuit network 31 include a short circuit between uniform lines 35 and 37, and a short circuit between uniform lines 36 and 38 in the first branch portion 20. The inductance of these short circuits is effectively zero. However, if the inductance is zero, the admittance, which corresponds to the reciprocal of the inductance, becomes infinite. Therefore, the inductance of these short circuits is set to a value st that is sufficiently smaller than the inductances Za to Zd of the first to fourth terminal loads 15 to 18. Therefore, the reciprocal of st is included in the admittance matrix Y1.

[0039]

Formula 1

[0040]

[0041] On the other hand, the second terminal circuit network 32 includes a second terminal load 16 as a load element connected to the ends of the uniform lines 33 to 39. The second terminal circuit network 32 also includes load elements connected between the uniform lines 33 to 39. The load elements connected between the uniform lines 33 to 39 in the second terminal circuit network 32 include a short-circuit between uniform lines 38 and 39 at the turning point 22, a short-circuit between uniform lines 33 and 35 at the second branch 21, and a short-circuit between uniform lines 34 and 36. As in the case of equation (1), the admittance matrix Y2 of the second terminal circuit network 32 is calculated as shown in equation (2) by using the inductance value st of the short-circuit.

[0042]

Formula 2

[0043]

[0044] Next, as shown in equation (3), a unit length impedance matrix Z of the entire uniform line group 30 is generated. The unit length impedances of the uniform lines 33 to 39 constituting the uniform line group 30 are arranged in the diagonal elements of the unit length impedance matrix Z.

[0045]

Formula 3

[0046]

[0047] As shown in equation (4), a voltage-mode conversion coefficient matrix Tv is generated for the entire uniform line group 30. The voltage-mode conversion coefficients of the uniform lines 33 to 39 constituting the uniform line group 30 are arranged in the diagonal elements of the voltage-mode conversion coefficient matrix Tv.

[0048]

Formula 4

[0049]

[0050] Furthermore, as shown in equation (5), a propagation coefficient matrix γ is generated for the entire uniform line group 30. The propagation coefficients of the uniform lines 33 to 39 constituting the uniform line group 30 are arranged in the diagonal elements of the propagation coefficient matrix γ.

[0051]

Formula 5

[0052]

[0053] As shown in equation (6), a line length matrix d is generated for the entire uniform line group 30. The line lengths d1 to d7 of the uniform lines 33 to 39 constituting the uniform line group 30 are arranged in the diagonal elements of the line length matrix d.

[0054]

Formula 6

[0055]

[0056] By using the above equations, the characteristic admittance matrix Y0 of the entire uniform line group 30 can be derived as shown in equation (7).

[0057]

Formula 7

[0058] Y0=Z -1 ·Tv·γ·Tv -1 (7)

[0059] The admittance matrix of the first terminal circuit network 31 is set to Y1, and the noise source 19 is set to the current source J. The actual input voltage wave Ass from the first terminal circuit network 31 at this time is calculated as the value shown in equation (8). On the other hand, when the noise source 19 is defined as a voltage source, the actual input voltage wave Ass is calculated by converting the noise source 19 into a current source using the Norton equivalent circuit.

[0060]

Formula 8

[0061] Ass=(Y0+Y1) -1 [0 … 0 J] T (8)

[0062] The actual input voltage wave Ass can be converted into the mode incident voltage wave vector Amss as shown in equation (9).

[0063]

Formula 9

[0064] Amss=Tv -1 ·ass (9)

[0065] The actual voltage reflection coefficient matrix S1 of the first terminal circuit network 31 is expressed in the form shown in equation (10).

[0066]

Formula 10

[0067] S1=(Y0+Y1) -1 ·(Y0-Y1) (10)

[0068] If the actual voltage reflection coefficient matrix S1 is transformed into a mode space, equation (11) is obtained. Equation (11) represents the mode reflection coefficient matrix Sm1 of the first terminal circuit network 31. Similarly, the mode reflection coefficient matrix Sm2 of the second terminal circuit network 32 can also be obtained.

[0069]

Formula 11

[0070] Sm1=Tv -1 ·S1·Tv (11)

[0071] Figure 2express Figure 1 The replacement circuit of the multi-conductor transmission line system 10 is described. The propagation of noise in the replacement circuit is explained by the propagation of the mode voltage wave in the uniform line group 30 and the mode reflection in the first terminal circuit network 31 and the second terminal circuit network 32. In this case, the noise input to the replacement circuit from the noise source 19 becomes the mode incident voltage wave vector Amss of equation (9). The input noise circulates once in the multi-conductor transmission line system 10 by sequentially: (a) propagating through the uniform line group 30; (b) reflecting in the second terminal circuit network 32; (c) propagating through the uniform line group 30; and (d) reflecting in the first terminal circuit network 31. The attenuation and phase delay of the noise in the noise propagation of (a) and (c) are calculated as the vector AT shown in equation (12).

[0072]

Formula 12

[0073] AT=e -γd (12)

[0074] On the other hand, as described above, the reflection of noise in the first terminal circuit network 31 and the second terminal circuit network 32 is represented by the mode reflection coefficient matrices Sm1 and Sm2, respectively, as shown in Equation (10). Therefore, the propagation of noise that has completed one cycle in the multi-conductor transmission line system 10 is represented as the single-cycle propagation Smc shown in Equation (13).

[0075]

Formula 13

[0076] Smc=(Sm1·e -γd ·Sm2·e -γd ) (13)

[0077] In the multi-conductor transmission line system 10, this single-cycle propagation Smc is repeated infinitely. That is, the accumulation of multiple reflection propagations results in the final propagation. Therefore, the propagation of noise in the multi-conductor transmission line system 10 can be expressed as the sum of a geometric infinite series matrix using the single-cycle propagation Smc of Equation (13) as the common ratio matrix. Typically, since reflections in the first and second terminal circuit networks 31 and 32 are accompanied by attenuation, this geometric infinite series matrix does not diverge.

[0078] Therefore, the mode voltage wave vector Am1 of the noise incident from the first terminal circuit network 31 to the uniform line group 30 is expressed as in equation (14).

[0079]

Formula 14

[0080] Am1=(I-Sm1·e -γd ·Sm2·e -γd ) -1·Amss (14)

[0081] The modal multi-reflection infinite series matrix Sms of the multi-conductor transmission line system 10 is calculated as shown in Equation (15). The sum of the modal multi-reflection infinite series matrix Sms is the vectorization of the infinite geometric series of a scalar. Therefore, the method for deriving the sum of the modal multi-reflection infinite series matrix Sms is the same as the method for deriving a scalar.

[0082]

Formula 15

[0083] Sms=(I-Sm1·e -γd ·Sm2·e -γd ) -1 (15)

[0084] The modal multi-reflection infinite series matrix Sms in equation (15) contains information related to all noise propagation to the components of the multi-conductor transmission line system 10. The modal multi-reflection infinite series matrix Sms in equation (15) represents the multiple reflections of noise input to the multi-conductor transmission line system 10. Therefore, by using this modal multi-reflection infinite series matrix Sms, the noise characteristics of the multi-conductor transmission line system 10 can be analyzed.

[0085] <Functions and Effects of Implementation Methods>

[0086] The operation and effects of the analysis method of the multi-conductor transmission line system 10 according to this embodiment will be described.

[0087] The multi-conductor transmission line system 10, which is the subject of analysis in this embodiment, has multiple conductor lines (12, 13) with branches. The presence of branches makes analyzing noise characteristics difficult. Therefore, the analysis method of this embodiment analyzes the noise characteristics of the multi-conductor transmission line system 10 using a noise propagation model as a propagation model. The noise propagation model assumes that a noise signal input to the multi-conductor transmission line system 10 propagates through a uniform line group 30 while undergoing multiple reflections between a first end circuit network 31 and a second end circuit network 32. In the noise propagation model, it is assumed that the conductor lines (12, 13) of the multi-conductor transmission line system 10 are wired so as to reciprocate between the first end circuit network 31 and the second end circuit network 32, with the characteristic impedance change point as a turning point. The characteristic impedance change point includes branch portions (20, 21) where the conductor lines (12, 13) branch from the parallel section 14. The uniform line group 30 in the noise propagation model is composed of uniform lines 33 to 39 spanning between the first terminal circuit network 31 and the second terminal circuit network 32. The first terminal circuit network 31 and the second terminal circuit network 32 in the noise propagation model are composed of the first to fourth terminal loads 15 to 18 connected to the ends of the conductor lines (12, 13) and the return terminal elements connected to the ends of the uniform lines 33 to 39. In other words, Figure 2 The noise propagation model is to Figure 1 The multi-conductor transmission line system 10 is replaced with a hypothetical multi-conductor transmission line system consisting of multiple uniform lines 33 to 39 without branches. Multiple uniform lines 33 to 39 are arranged in parallel and spanned between the first terminal circuit network 31 and the second terminal circuit network 32. The noise characteristics of this hypothetical multi-conductor transmission line system can be analyzed using existing analytical methods.

[0088] The above-described analysis method of the multi-conductor transmission line system 10 according to the present embodiment has the following effects.

[0089] (1) The analysis method of this embodiment virtually replaces a branched multiconductor transmission line system 10 with a non-branched multiconductor transmission line system. The noise characteristics of the replaced multiconductor transmission line system are analyzed. This allows for simplified analysis of the noise characteristics of the branched multiconductor transmission line system 10.

[0090] (2) The analysis method of this embodiment divides the first conductor line 12 and the second conductor line 13 into multiple sections based on their characteristic impedances. These sections correspond to the uniform lines 33 to 39. The analysis method can independently determine the noise characteristics of each of these sections, thus enabling detailed noise characteristic analysis.

[0091] (Design Method of Multi-Conductor Transmission Line System Using the Analytical Method of the Above-mentioned Embodiment)

[0092] The noise characteristics of the multi-conductor transmission line system 10 are analyzed using the modal multi-reflection infinite series matrix Sms of Equation (15). The analysis results are reflected in the design of the multi-conductor transmission line system 10. Therefore, the multi-conductor transmission line system 10 can be effectively designed to suppress the saliency of noise. Examples 1 to 4 of the design method for the multi-conductor transmission line system 10 are described below.

[0093] <Example 1>

[0094] The line lengths d1 to d7 of the uniform lines 33 to 39 are set so that the line length matrix d = [390, 390, [740, 740], 470, 470, 1], where all units are mm (millimeter). This multi-conductor transmission line system 10 is prototyped. For the uniform line 39, Figure 2 In the replacement circuit shown, noise source 19 is included in first terminal circuit network 31 for ease of calculation. Therefore, line length d7 of uniform line 39 is set sufficiently short compared to the lengths of the other uniform lines 33-38, for example, to 1 mm. In this prototype, the load resistance of the first to fourth terminal loads 15-18 is all set to 50Ω.

[0095] A noise signal was input to the noise source 19 of the prototype of the multi-conductor transmission line system 10. The noise signal was set so that the terminal voltage of the first conductor line 12 connected to the first terminal load 15 became 1V in the entire frequency band. The current in the second branch portion 21 of the second conductor line 13 in the state where the noise signal was input was actually measured. A measuring antenna was set near the prototype. The electric field strength at the setting point of the measuring antenna was actually measured using this measuring antenna. Based on the actual measurement results of the current, it was confirmed that there was a resonance peak of the current at 537 Hz. It was also confirmed that there was a resonance peak at 537 Hz in the electromagnetic waves radiated from the multi-conductor transmission line system 10 of the prototype. On the other hand, the electromagnetic waves of 537 Hz may have an adverse effect on the operation of the device equipped with the multi-conductor transmission line system 10. Therefore, it is necessary to change the design of the multi-conductor transmission line system 10 so that the frequency of the resonance peak of the current is shifted from 537 Hz.

[0096] Here, the modal multi-reflection infinite series matrix Sms of equation (15) represents the steady state of the response of the multi-conductor transmission line system 10 to the incident noise signal. Therefore, the eigenvalue of the modal multi-reflection infinite series matrix Sms represents the natural vibration frequency of the multi-conductor transmission line system 10. Therefore, the modal multi-reflection infinite series matrix Sms that reflects the design value of the multi-conductor transmission line system 10 of the prototype as described above and the noise signal is used. In this way, the eigenvalue analysis of the multi-conductor transmission line system 10 of the prototype can be performed. The result of the eigenvalue analysis is obtained as the eigenvector E for each frequency. The eigenvector E at a specific frequency is obtained in the form shown in equation (16). The suffix "T" in equation (16) represents the transpose of the vector. That is, the suffix "T" means that the vector in the equation is not a transverse vector, but actually a longitudinal vector. The eigenvector E has all the elements e1 to e6 corresponding to the eigenvalues ​​of the uniform lines 33 to 38, respectively. In fact, the eigenvector E also includes an element corresponding to the eigenvalue of the uniform line 39. However, in equation (16), the intrinsic value of the uniform line 39 is omitted.

[0097]

Formula 16

[0098] E=(e1 e2 e3 e4 e5 e6) T (16)

[0099] Here, the maximum value among the elements e1 to e6 of the eigenvector E at a specific frequency is called the maximum eigenvalue. The frequency at which the maximum eigenvalue becomes a peak, that is, becomes extremely large, is called the peak frequency of the maximum eigenvalue. According to the results of the eigenvalue analysis, it was confirmed that there is a peak frequency of the maximum eigenvalue at 558 Hz. 558 Hz is close to 537 Hz. 537 Hz is the problematic current resonance peak frequency. Here, there is a slight error in the results of the eigenvalue analysis using the mode multiple reflection infinite series matrix Sms. This error is accompanied by the replacement of the circuit from the first conductor line 12 and the second conductor line 13 to the uniform line group 30. Due to the existence of this error, the peak frequency of the maximum eigenvalue is not completely consistent with the current resonance peak frequency. However, it is considered that the peak frequency of the maximum eigenvalue of 558 Hz is likely related to the peak frequency of 537 Hz of the current and electromagnetic wave.

[0100] The results of eigenvalue analysis confirmed that, among the elements e1 to e6 of the eigenvector E at 558 Hz, elements e1, e4, and e6 are larger than the other elements e2, e3, and e5. Therefore, it is believed that changing the characteristic impedance of uniform lines 33, 36, and 38 corresponding to elements e1, e4, and e6, respectively, is effective in shifting the peak frequency of 537 Hz. Therefore, this time, a process was performed to change the line lengths d1 to d4 of the four uniform lines 33 to 36. The four uniform lines 33 to 36 include two of the uniform lines 33, 36, and 38: uniform lines 33 and 36. The line lengths d1 to d4 were changed so that the post-change line length matrix d became [510, 510, [620, 620], 470, 470, 1] (all units are in mm). That is, the first four values, 510, 510, 620, and 620, have been changed from 390, 390, 740, and 740, respectively.

[0101] The changes in line lengths d1-d4 are reflected in the modal multi-reflection infinite series matrix Sms. Eigenvalue analysis using the reflected modal multi-reflection infinite series matrix Sms shows that the peak frequency of the maximum eigenvalue shifts from 558 Hz. Using a multi-conductor transmission line system 10 with modified line lengths d1-d4, actual current and electromagnetic intensity measurements were conducted in a prototype multi-conductor transmission line system 10. The results confirm that the actual current and electromagnetic wave resonance peaks also shifted from 537 Hz.

[0102] Summarizing the above, in Example 1, the design of the multi-conductor transmission line system 10 was performed using the following steps 1 to 3. Step 1 used the analysis method of this embodiment to analyze the eigenvalues ​​of the uniform lines 33 to 38, among the multiple components of the multi-conductor transmission line system 10. Step 2, based on the results of the eigenvalue analysis, extracted the uniform lines 33 to 38 with the highest eigenvalues ​​at problematic frequencies. Step 3 modified the design values ​​of some of the extracted uniform lines, in Example 1, the uniform lines 33 and 36, to change the characteristic impedance of the uniform lines 33 and 36. Specifically, in Example 1, the line lengths of the uniform lines 33 and 36 were modified. The characteristic impedances of the uniform lines 33 to 38 were also modified by changing the cross-sectional shape of the conductors of the uniform lines 33 to 38 or by changing the height of the uniform lines 33 to 38 from the ground plane 11. Therefore, the third step may be performed by changing the cross-sectional shape of the conductor of the extracted uniform line or by changing the height of the extracted uniform line from the ground plane 11 .

[0103] On the other hand, the multi-conductor transmission line system 10 can also be designed by changing the load resistance of the first end load 15 to the fourth end load 18 as follows. In this case, the first step is to calculate the eigenvalue of each of the first end load 15 to the fourth end load 18 at each frequency by using the eigenvalue analysis method of this embodiment. The second step is to extract the end load with a relatively large eigenvalue at the problematic frequency from among the first end load 15 to the fourth end load 18. The end load extracted from the first end load 15 to the fourth end load 18 is the specific end load. The third step is to change the load resistance of the specific end load to change its characteristic impedance.

[0104] <Example 2>

[0105] In the prototype of the multi-conductor transmission line system 10 in Example 2, the line lengths d1 to d7 of the uniform lines 33 to 39 were set to be identical to the pre-modification line length matrix d in Example 1. Specifically, the line length matrix d = [390, 390, [740, 740], 470, 470, 1] (all units are in mm). The first to fourth end loads 15 to 18 of the prototype of Example 2 all had a load resistance of 50Ω. Furthermore, in the prototype of the multi-conductor transmission line system 10 in Example 2, all uniform lines 33 to 39 were laid at a constant first height H1 from the ground plane 11.

[0106] The following noise signal was input from the noise source 19 to the prototype of the multi-conductor transmission line system 10 of the second embodiment. Specifically, the noise signal was set so that the voltage at the end of the first conductor line 12, which is connected to the first end load 15, would be 1V over the entire frequency band. The voltage value V3 of the third end load 17 and the voltage value V4 of the fourth end load 18, with the noise signal input, were actually measured. The actual measurement results of the voltage values ​​V3 and V4 confirmed that there were multiple frequencies of the resonant peak of the voltage. The multiple frequencies confirmed included 413 Hz. This 413 Hz adversely affects the operation of the device connected to the second conductor line 13 as the fourth end load 18. In other words, 413 Hz is an example of a problematic frequency. Therefore, the design of the multi-conductor transmission line system 10 needs to be modified so that the frequency of the resonant peak of the voltage is shifted from 413 Hz.

[0107] On the other hand, the results of the eigenvalue analysis of this prototype confirmed that the peak frequency of the eigenvalue with the largest absolute value and the peak frequency of the eigenvalue with the second largest absolute value appear to roughly overlap at the frequency of the voltage resonant peak. The first, fifth, and sixth elements e1, e5, and e6 of the eigenvector corresponding to the eigenvalue with the largest absolute value at 413 Hz exhibit values ​​greater than those of the other elements e2 to e4 of this eigenvector. The first, second, and fourth elements e1, e2, and e4 of the eigenvector corresponding to the eigenvalue with the second largest absolute value at 413 Hz exhibit values ​​greater than those of the other elements e3, e5, and e6 of this eigenvector.

[0108] As a countermeasure, we consider changing the second-largest eigenvalue at 413 Hz. Based on the results of the eigenvalue analysis described above, it is believed that changing the characteristic impedance of uniform lines 33, 34, and 36 is effective. This is because uniform lines 33, 34, and 36 correspond to the first, second, and fourth elements e1, e2, and e4. Specifically, uniform lines 33, 34, and 36 are specific components of the multi-conductor transmission line system 10 that have eigenvalues ​​greater than those of the other components. As in Example 1, the line lengths d1 to d4 of uniform lines 33 to 36 are changed so that the changed line length matrix d becomes [510, 510, [620, 620], 470, 470, 1] (all units in mm). In other words, the initial four values, 510, 510, 620, and 620, are changed.

[0109] An eigenvalue analysis was performed using a modal multi-reflection infinite series matrix Sms that reflects the changes in line lengths d1 to d4. The results of the eigenvalue analysis showed that the resonant peak frequency of the voltage deviated from the maximum eigenvalue peak frequency of 558 Hz. In the multi-conductor transmission line system 10 with the line lengths d1 to d4 varied, voltage values ​​V3 and V4 were actually measured, similar to the prototype. The results confirmed that the resonant peak voltage of the fourth end load 18 also deviated from the peak frequency of the current and electromagnetic waves, 537 Hz.

[0110] Instead of changing the line length, the resonant peak frequency can be altered by changing the height of each uniform line 33-39 from the ground plane 11. In this case, the design of the multi-conductor transmission line system 10 is performed through the following fourth and fifth steps. The fourth step calculates the peak frequency of the noise of the components of the multi-conductor transmission line system 10 using the analytical method of the above-described embodiment. In the fifth step, if the calculated peak frequency is a problematic frequency, the height of one or more of the uniform lines 33-39 from the ground plane 11 is altered.

[0111] <Example 3>

[0112] By using the modal multi-reflection infinite series matrix Sms of equation (15), it is possible to calculate the voltage values ​​of each of the first end load 15 to the fourth end load 18 when noise is input. By using the calculation results of the voltage values ​​of the first end load 15 to the fourth end load 18, the multi-conductor transmission line system 10 can be designed in a manner that reduces specific frequency components of the noise voltage in any of the first end loads 15 to the fourth end load 18.

[0113] The mode voltage wave vector Am1 of the noise incident on the uniform line group 30 from the first terminal circuit network 31 is calculated using equation (15). The noise that has been incident on the uniform line group 30 from the first terminal circuit network 31 propagates through the uniform line group 30 and then enters the second terminal circuit network 32. As described above, the attenuation and phase delay of the noise accompanying the propagation of the noise in the uniform line group 30 are represented by the vector AT in equation (12). The noise that has been incident on the second terminal circuit network 32 after being emitted from the first terminal circuit network 31, propagating through the uniform line group 30, and then entering the second terminal circuit network 32 has a mode voltage wave vector Bm2. The mode voltage wave vector Bm2 is calculated using equation (17).

[0114]

Formula 17

[0115] Bm2=e -γd ·Am1 (17)

[0116] After entering the second terminal circuit network 32 from the uniform line group 30, the noise is reflected by the second terminal circuit network 32 and then re-enters the uniform line group 30, thereby having a mode voltage wave vector Am2. The mode voltage wave vector Am2 is expressed as shown in Equation (18) using the mode reflection coefficient matrix Sm2 in the second terminal circuit network 32.

[0117]

Formula 18

[0118] Am2=Sm2·Bm2 (18

[0119] Furthermore, the noise that propagates through the uniform line group 30 and then re-enters the first terminal circuit network 31 has a mode voltage wave vector Bm1. Mode voltage wave vector Bm1 is expressed as in equation (19) using the vector AT in equation (12). The vector AT in equation (12) represents the attenuation and phase delay of the noise as it propagates through the uniform line group 30.

[0120]

Formula 19

[0121] Bm1=e -γd ·Am2 (19)

[0122] Based on the above, all the incident voltage waves and reflected voltage waves of the first terminal circuit network 31 and the second terminal circuit network 32 are calculated. Based on this, the mode voltage vectors Vm1 and Vm2 of the first terminal circuit network 31 and the second terminal circuit network 32 are calculated. The mode voltage vector Vm1 of the first terminal circuit network 31 is expressed as the sum of the mode voltage wave vector Am1 and the mode voltage wave vector Bm1 (Vm1 = Am1 + Bm1). The mode voltage vector Vm2 of the second terminal circuit network 32 is expressed as the sum of the mode voltage wave vector Am2 and the mode voltage wave vector Bm2 (Vm2 = Am2 + Bm2). The voltage values ​​of each of the first terminal load 15 to the fourth terminal load 18 can be calculated by multiplying the mode voltage vectors Vm1 and Vm2 by the mode conversion matrix Pv. In Example 3, the design of the multi-conductor transmission line system 10 is carried out by using the calculation results of these voltage values.

[0123] This embodiment 3 compares and studies two design schemes 1 and 2 as the design schemes of the multi-conductor transmission line system 10. The difference between the design scheme 1 and the design scheme 2 is only that Figure 2 The height of the single-line section corresponding to the uniform line 33 from the ground plane 11 is H1. The single-line section corresponding to the uniform line 33 is included in the second conductor line 13. That is, the height of the single-line section corresponding to the uniform line 33 in Design 1 from the ground plane 11 is the first height H1. The height of the single-line section corresponding to the uniform line 33 in Design 2 from the ground plane 11 is the second height H2. In the multi-conductor transmission line system 10 to be designed, it was confirmed that 500 MHz noise adversely affects the operation of the device connected to the second conductor line 13 as the fourth end load 18. Therefore, the process of determining the superiority of Design 1 and Design 2 based on the magnitude of the 500 MHz noise generated in the fourth end load 18 will be described here.

[0124] In the comparative study, the voltage value of the fourth end load 18 was first calculated for each of the multi-conductor transmission line systems 10 of Designs 1 and 2, when the same noise signal was incident on Designs 1 and 2, using the aforementioned analytical method. The results confirmed that there is a band in which the frequency characteristics of the noise generated by the fourth end load 18 differ significantly between Designs 1 and 2. At the problematic frequency of 500 MHz, the noise level in Design 1 was smaller than that in Design 2. Therefore, Design 1 was adopted.

[0125] <Example 4>

[0126] In Example 4, three prototypes of a multi-conductor transmission line system 10, namely, prototypes 1 to 3, were prepared. Prototypes 1 to 3 differed from each other only in the height of the first conductor line 12 and the second conductor line 13 laid on the ground plane 11 from the ground plane 11. That is, in the multi-conductor transmission line system 10 of prototype 1, the first conductor line 12 and the second conductor line 13 were laid at a first height H1 from the ground plane 11. In the multi-conductor transmission line system 10 of prototype 2, the first conductor line 12 and the second conductor line 13 were laid at a second height H2 (>H1) from the ground plane 11. In the multi-conductor transmission line system 10 of prototype 3, the first conductor line 12 and the second conductor line 13 were laid in close contact with the ground plane 11.

[0127] In Example 4, the noise voltage of the fourth end load 18 for each of Prototypes 1 to 3 was calculated using the analytical method of Example 3. Furthermore, the noise voltage of the fourth end load 18 was actually measured for each of Prototypes 1 to 3. The measured noise voltage was compared with the noise voltage calculated using the analytical method. For Prototype 1, the calculated results were largely consistent with the measured results, except for a portion of the frequency band. In contrast, for Prototypes 2 and 3, the calculated results deviated significantly from the measured results in more than half of the frequency band.

[0128] This is believed to be due to the following reasons. When the conductor line is laid at a position that is somewhat away from the ground plane 11, the connection between the conductor of the conductor line and the ground plane 11 becomes weaker. In addition, the radiation from the conductor line becomes larger. Therefore, it is believed that if the height of the conductor line from the ground plane 11 is too high, the analysis results of the noise characteristics using the analysis method of the above embodiment will be difficult to match the actual measurement results. On the other hand, when the conductor line is laid closely to the ground plane 11, the distance between the conductor of the conductor line and the ground plane 11 is determined by the thickness of the covering dielectric of the conductor line. The noise characteristics in this case can change significantly due to deformation of the covering dielectric. Therefore, it is believed that the analysis results are likely to deviate from the actual measurement results.

[0129] Based on the results of this analysis and actual measurements, the inventors of this application have reached the following conclusion: Specifically, the height of the conductor lines of the multi-conductor transmission line system 10 from the ground plane 11 is preferably set to satisfy the following conditions 1 and 2. Condition 1: The height of the conductor lines from the ground plane 11 is at least twice the thickness of the dielectric covering the conductor lines. Condition 2: The height of the conductor lines from the ground plane 11 is sufficiently small relative to the wavelength of the highest-frequency noise signal among the noise signals being analyzed. These conditions 1 and 2 define the effective application range of the analysis method of the above-described embodiment.

[0130] (Other embodiments)

[0131] The analytical method of the above embodiment and the design method of each embodiment can also be applied to Figure 1 Multi-conductor transmission line systems with different structures. A multi-conductor transmission line system may be composed of multiple conductor lines and have multiple conductor line branches. For example, the analysis method of the above-described embodiment and the design methods of the above-described examples can also be applied to multi-conductor transmission line systems composed of three or more conductor lines, or multi-conductor transmission line systems with multiple parallel sections. The following describes configuration examples 1 and 2 of multi-conductor transmission line systems to which the analysis method of the above-described embodiment can be applied.

[0132] <Structure Example 1>

[0133] Figure 3The multi-conductor transmission line system 100 of Structural Example 1 shown in FIG. 1 includes a ground plane 101 and three conductor lines. The three conductor lines include a first conductor line 102, a second conductor line 103, and a third conductor line 104. In this multi-conductor transmission line system 100, the second conductor line 103 and the third conductor line 104 are laid parallel to each other, in close contact with each other throughout their entire length. Furthermore, a three-wire parallel section 105 is provided in the multi-conductor transmission line system 100, where the first to third conductor lines 102, 104 are parallel. The three-wire parallel section 105 is terminated at its ends by a first branch 120 and a second branch 121. The first branch 120 branches into a single-wire section and a two-wire parallel section 106. The single-wire section includes the first conductor line 102. In the two-wire parallel section 106, the second conductor line 103 and the third conductor line 104 are parallel. The second branch portion 121 branches into a single-line section and a two-line parallel section 107. The single-line section includes a first conductor line 102. In the two-line parallel section 107, the second conductor line 103 and the third conductor line 104 are parallel. Both ends of the first conductor line 102 are grounded to the ground plane 11 via corresponding end loads 108 and 111, respectively. Both ends of the second conductor line 103 are grounded to the ground plane 11 via corresponding end loads 109 and 112, respectively. Both ends of the third conductor line 104 are grounded to the ground plane 11 via corresponding end loads 110 and 113, respectively. Figure 3 In the case of the multi-conductor transmission line system 100 , the noise source 19 is connected to the end of the first conductor line 102 connected to the end load 108 .

[0134] The cross-sectional shape of the conductor of the first conductor line 102 changes in the single-line section between the first branch portion 120 and the end load 108. Figure 3 In FIG. 1 , the difference in the cross-sectional shape of the conductor of the first conductive line 102 is represented by the difference in thickness of the line representing the first conductive line 102. In the following description, the position where the cross-sectional shape of the conductor of the first conductive line 102 changes is described as a change point 114.

[0135] Figure 4 Indicates that when the analytical method of the above embodiment is applied, Figure 3 FIG2 is a circuit diagram of a replacement circuit after the multi-conductor transmission line system 100. As in the above embodiment, the position where the characteristic impedance changes includes a first branch portion 120 and a second branch portion 121 branching from the three-line parallel section 105. Figure 4The replacement circuit is created by virtually wiring the first conductor line 102 to the third conductor line 104 as follows. That is, the first conductor line 102 to the third conductor line 104 are virtually wired in such a way that the position where the characteristic impedance changes is used as a turning point and the circuits go back and forth between the first terminal circuit network 131 and the second terminal circuit network 132. Figure 3 In the case of the multi-conductor transmission line system 100, the characteristic impedance change position includes the first branch portion 120 and the second branch portion 121, and in addition, there is a change point 114 of the cross-sectional shape of the conductor of the first conductor line 102. The uniform line group 230 is composed of 10 uniform lines 133 to 142 each having a uniform characteristic impedance throughout the entire length. Figure 3 In FIG. 1 , the portions corresponding to the uniform lines 133 to 142 are indicated by corresponding numbers 133 to 142. Figure 3 The multi-conductor transmission line system 100 is hypothetically replaced by Figure 4 As a result, the mode multiple reflection infinite series matrix Sms of equation (15) can be applied to the multi-conductor transmission line system 100. Therefore, Figure 3 The noise characteristics of the multi-conductor transmission line system 100 of the illustrated configuration example 1 can also be efficiently analyzed by using the analysis method of the above-described embodiment.

[0136] <Structure Example 2>

[0137] Figure 5 The multi-conductor transmission line system 200 of the second structural example is shown. The multi-conductor transmission line system 200 includes a ground plane 201 and three conductor lines. The three conductor lines include a first conductor line 202, a second conductor line 203, and a third conductor line 204. Figure 5In the multi-conductor transmission line system 200, two parallel sections are provided: a first parallel section 205 and a second parallel section 206. In the first parallel section 205, the first conductor line 202 and the second conductor line 203 are arranged in parallel in close contact. In the second parallel section 206, the first conductor line 202 and the third conductor line 204 are arranged in parallel in close contact. The first parallel section 205 is terminated by a first branching portion 220 and a second branching portion 221. The first conductor line 202 and the second conductor line 203 branch off at the first branching portion 220 and the second branching portion 221, respectively. The second parallel section 206 is terminated by a third branching portion 222 and a fourth branching portion 223. The first conductor line 202 and the third conductor line 204 branch off at the third branching portion 222 and the fourth branching portion 223, respectively. Among the first to third conductor lines 202 to 204, only the first conductor line 202 is laid so as to pass through both the first parallel section 205 and the second parallel section 206. The second conductor line 203 is laid so as to pass through the first parallel section 205. The third conductor line 204 is laid so as to pass through the second parallel section 206. Both ends of the first conductor line 202 are grounded to the ground plane 11 via corresponding end loads 207 and 210, respectively. Both ends of the second conductor line 203 are grounded to the ground plane 11 via corresponding end loads 208 and 211, respectively. Both ends of the third conductor line 204 are grounded to the ground plane 11 via corresponding end loads 209 and 212, respectively. Figure 5 In the case of the multi-conductor transmission line system 200 , the noise source 19 is connected to the end of the first conductor line 202 connected to the end load 207 .

[0138] Figure 6 Indicates that when the analytical method of the above embodiment is applied, Figure 5 A circuit diagram of a replacement circuit following the multi-conductor transmission line system 200 is shown. Figure 5 In the case of the multi-conductor transmission line system 200, the first through third conductor lines 202, 204 have a first parallel section 205 and a second parallel section 206. Specifically, in the first parallel section 205, the first conductor line 202 and the second conductor line 203 run in parallel. In the second parallel section 206, the first conductor line 202 and the third conductor line 204 run in parallel. The first parallel section 205 has a first branch 220 and a second branch 221. The second parallel section 206 has a third branch 222 and a fourth branch 223. The first through third conductor lines 202, 204 each have a characteristic impedance change position at the first through fourth branch 220, 223. Figure 6 The replacement circuit is made by virtually wiring the first conductor line 202 to the third conductor line 204 as follows. Figure 6 In the diagram, the first to third conductor lines 202 to 204 are virtually wired so as to reciprocate between the first end circuit network 231 and the second end circuit network 232 with the first to fourth branch portions 220 to 223 as turning points. Figure 6 The uniform line group 230 is composed of 11 uniform lines 233 to 243. Figure 5 In FIG. 1 , the portions corresponding to the uniform lines 233 to 243 are indicated with corresponding numbers 233 to 243. Figure 5 The multi-conductor transmission line system 200 is hypothetically replaced by Figure 6 The permutation circuit of the mode multi-reflection infinite series matrix Sms of formula (15) can be applied to Figure 5 The multi-conductor transmission line system 200. Therefore, Figure 5 The noise characteristics of the multi-conductor transmission line system 200 of the second configuration example can also be efficiently analyzed by using the analysis method of the above-described embodiment.

[0139] The control device that performs various calculations for noise analysis is not limited to a CPU and a ROM that executes software processing. In other words, the control device may be configured as any one of the following (a), (b), and (c).

[0140] (a) The control device includes one or more processors that execute various processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to execute the processes. The memory, or computer-readable medium, includes so-called accessible media that can be accessed by a general-purpose or special-purpose computer.

[0141] (b) The control device includes one or more dedicated hardware circuits that perform various processes. Examples of dedicated hardware circuits include application-specific integrated circuits, such as ASICs or FPGAs. ASIC stands for "Application Specific Integrated Circuit," and FPGA stands for "Field Programmable Gate Array."

[0142] (c) The control device includes a processor that executes part of various processes according to a computer program, and a dedicated hardware circuit that executes the remaining processes among the various processes.

Claims

1. A method for analyzing a multi-conductor transmission line system, wherein: The analysis method has the following steps, namely: The multi-conductor transmission line system includes a ground plane and a plurality of conductor lines, wherein the multi-conductor transmission line system has a parallel section, wherein the plurality of conductor lines are arranged in parallel in the parallel section, wherein the plurality of conductor lines each have an end load, wherein one or more of the plurality of conductor lines have one or more branch portions branching from the parallel section, and wherein the plurality of conductor lines have one or more locations where characteristic impedance changes, wherein the one or more locations where characteristic impedance changes include one or more branch portions. a step of assuming a noise propagation model, assuming that the noise propagation model includes a uniform line group, a first end circuit network, and a second end circuit network, and that a noise signal input to the multi-conductor transmission line system propagates through the uniform line group while undergoing multiple reflections between the first end circuit network and the second end circuit network; The step of assuming the routing of the plurality of conductor lines in the noise propagation model, assuming that the plurality of conductor lines are respectively routed in such a manner that: one or more of the change positions of the characteristic impedance are used as one or more turning points, and the plurality of conductor lines reciprocate between the first end circuit network and the second end circuit network, and one or more of the turning points each have a turning end element; The step of forming the uniform line group, wherein the uniform line group is formed of a plurality of uniform lines, wherein each of the plurality of conductor lines comprises a plurality of uniform lines spanned between the first terminal circuit network and the second terminal circuit network, and the uniform line group comprises a first group end corresponding to the first terminal circuit network and a second group end corresponding to the second terminal circuit network; a step of forming the first terminal circuit network by one or more terminal loads connected to the first group of terminals and one or more return terminal elements connected to the first group of terminals; a step of forming the second terminal circuit network by one or more terminal loads connected to the second group end and one or more return terminal elements connected to the second group end; as well as The step of analyzing the noise characteristics of the multi-conductor transmission line system by using the noise propagation model.

2. The method for analyzing a multi-conductor transmission line system according to claim 1, wherein: The ground plane is the conductive body of the delivery device.

3. The method for analyzing a multi-conductor transmission line system according to claim 1, wherein: The conductor lines are electric wires or bus bars.

4. A method for designing a multi-conductor transmission line system, wherein: The design method comprises the following steps, namely: The multi-conductor transmission line system includes a ground plane and a plurality of conductor lines, wherein the multi-conductor transmission line system has a parallel section, wherein the plurality of conductor lines are arranged in parallel in the parallel section, wherein the plurality of conductor lines each have an end load, wherein one or more of the plurality of conductor lines have one or more branch portions branching from the parallel section, and wherein the plurality of conductor lines have one or more locations where characteristic impedance changes, wherein the one or more locations where characteristic impedance changes include one or more branch portions. a step of assuming a noise propagation model, assuming that the noise propagation model includes a uniform line group, a first end circuit network, and a second end circuit network, and that a noise signal input to the multi-conductor transmission line system propagates through the uniform line group while undergoing multiple reflections between the first end circuit network and the second end circuit network; The step of assuming the routing of the plurality of conductor lines in the noise propagation model, assuming that the plurality of conductor lines are respectively routed in such a manner that: one or more of the change positions of the characteristic impedance are used as one or more turning points, and the plurality of conductor lines reciprocate between the first end circuit network and the second end circuit network, and one or more of the turning points each have a turning end element; The step of forming the uniform line group, wherein the uniform line group is formed of a plurality of uniform lines, wherein each of the plurality of conductor lines comprises a plurality of uniform lines spanned between the first terminal circuit network and the second terminal circuit network, and the uniform line group comprises a first group end corresponding to the first terminal circuit network and a second group end corresponding to the second terminal circuit network; a step of forming the first terminal circuit network by one or more terminal loads connected to the first group of terminals and one or more return terminal elements connected to the first group of terminals; a step of forming the second terminal circuit network by one or more terminal loads connected to the second group end and one or more return terminal elements connected to the second group end; The step of analyzing the noise characteristics of the multi-conductor transmission line system by using the noise propagation model, thereby analyzing the inherent values ​​of a plurality of components of the multi-conductor transmission line system; a step of extracting a specific component, based on the analysis result of the inherent value, extracting the specific component from the plurality of components, the specific component having an inherent value greater than the inherent values ​​of the other components at a frequency that causes a problem; as well as The step of changing the design value of the specific component so as to change the characteristic impedance of the specific component.

5. A method for designing a multi-conductor transmission line system, wherein: The design method comprises the following steps, namely: The multi-conductor transmission line system includes a ground plane and a plurality of conductor lines, wherein the multi-conductor transmission line system has a parallel section, wherein the plurality of conductor lines are arranged in parallel in the parallel section, wherein the plurality of conductor lines each have an end load, wherein one or more of the plurality of conductor lines have one or more branch portions branching from the parallel section, and wherein the plurality of conductor lines have one or more locations where characteristic impedance changes, wherein the one or more locations where characteristic impedance changes include one or more branch portions. a step of assuming a noise propagation model, assuming that the noise propagation model includes a uniform line group, a first end circuit network, and a second end circuit network, and that a noise signal input to the multi-conductor transmission line system propagates through the uniform line group while undergoing multiple reflections between the first end circuit network and the second end circuit network; The step of assuming the routing of the plurality of conductor lines in the noise propagation model, assuming that the plurality of conductor lines are respectively routed in such a manner that: one or more of the change positions of the characteristic impedance are used as one or more turning points, and the plurality of conductor lines reciprocate between the first end circuit network and the second end circuit network, and one or more of the turning points each have a turning end element; The step of forming the uniform line group, wherein the uniform line group is formed of a plurality of uniform lines, wherein each of the plurality of conductor lines comprises a plurality of uniform lines spanned between the first terminal circuit network and the second terminal circuit network, and the uniform line group comprises a first group end corresponding to the first terminal circuit network and a second group end corresponding to the second terminal circuit network; a step of forming the first terminal circuit network by one or more terminal loads connected to the first group of terminals and one or more return terminal elements connected to the first group of terminals; a step of forming the second terminal circuit network by one or more terminal loads connected to the second group end and one or more return terminal elements connected to the second group end; a step of calculating a peak frequency by analyzing noise characteristics of the multi-conductor transmission line system using the noise propagation model, thereby calculating a peak frequency of noise in one or more components of the multi-conductor transmission line system, wherein each of the plurality of uniform lines has a height from the ground plane; as well as The step of changing one or more of the heights when the peak frequency is a problematic frequency.

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