JP2017174398A - Computer simulation method, and method for generating transmission line model - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce divergence between an actual measured value and simulation and correctly evaluate immunity characteristic or emission characteristic.SOLUTION: A transmission line model generation method includes the steps of: classifying a transmission line that is the object of modeling into at least an end line and an intermediate line in accordance with its installation state; and modeling each of the end line and the intermediate line individually and generating an end line model and an intermediate line model. The end line model and the intermediate line model include characteristic impedance and a delay time as parameters representing the transmission characteristic of each. A computer simulation method, with parameters of a transmission line model derived by modeling a transmission line, to which a device under test is connected, rendered variable values, evaluates the immunity characteristic or emission characteristic of the device under test while sweeping the parameters.SELECTED DRAWING: Figure 12

Description

  The present invention relates to a computer simulation method for evaluating immunity characteristics or emission characteristics, and a transmission line model generation method.

  Conventionally, when designing a structure (vehicle, railway, ship, aircraft, etc.) having a transmission line such as a conductive wire harness, or designing various electrical components mounted on it, its immunity characteristics or emissions As a means for evaluating the characteristics, in addition to the actual measurement benchmark, EMC [electro-magnetic compatibility] computer simulation is widely used.

  In addition, as an example of the related art related to the above, Patent Document 2 by the applicant of the present application, Non-Patent Document 1, and the like can be cited.

Japanese Patent Laying-Open No. 2015-75390 JP 2013-242649 A

Hiroya Tanaka et al., “BCI (Bulk Current Injection) test system simulation model”, technical research report. EMCJ, Environmental Electromagnetic Engineering, The Institute of Electronics, Information and Communication Engineers, August 31, 2012, Vol. 112, No. 201, p. 47-50

  However, in the conventional EMC computer simulation, the wire harness structure of an actual measurement benchmark with severe restrictions was directly modeled. For example, if the wire harness of EMC computer simulation is specified by the measurement benchmark so that the total length of the wire harness is 1700-2000 mm and the injection points of EMC noise are 3 places (positions 150 mm, 450 mm, 750 mm from the DUT) The same restrictions as the actual measurement benchmark were also imposed on the harness structure. Therefore, the phenomenon that can actually occur is not sufficiently covered, and it is difficult to correctly evaluate the actual immunity characteristic or emission characteristic.

  In the conventional EMC computer simulation, the wire harness model is represented by a single characteristic impedance. For this reason, there is a considerable discrepancy between the actual measurement value and the simulation value.

  In the present specification, in view of the above-mentioned problems found by the inventors of the present application, a computer simulation method capable of correctly evaluating immunity characteristics or emission characteristics is proposed. Moreover, in this specification, the production | generation method of the transmission line model which can reduce the discrepancy between an actual measurement value and a simulation value is proposed.

  The computer simulation method disclosed in the present specification uses a transmission line model parameter obtained by modeling the transmission line to which the device under test is connected as a variable value, and sweeps the parameter while immunity characteristics of the device under test are obtained. Or it is set as the structure which evaluates an emission characteristic.

  The transmission line model generation method for computer simulation disclosed in this specification classifies transmission lines to be modeled into at least two types of end lines and intermediate lines according to the installed state. And a step of individually modeling the end line and the intermediate line to generate an end line model and an intermediate line model.

  Other features, elements, steps, advantages, and characteristics of the present invention will become more apparent from the detailed description of the embodiments that follows and the accompanying drawings.

  According to the computer simulation method disclosed in the present specification, it is possible to correctly evaluate actual immunity characteristics or emission characteristics. Further, according to the transmission line model generation method disclosed in the present specification, it is possible to generate a transmission line model that can reduce the difference between the actual measurement value and the simulation value.

Schematic diagram of a wire harness network stretched around a vehicle Block diagram showing an example of electrical equipment BCI test Block diagram showing an example of vehicle BCI test Block diagram showing an example of electrical component emission test Block diagram showing an example of a simulation model The figure which shows the comparative example of malfunction voltage frequency characteristic and ultimate voltage frequency characteristic Sectional drawing which shows the laying example of a wire harness typically Frequency-gain diagram showing transmission characteristics dependence on installation position Sectional view schematically showing the single wire model Sectional view schematically showing the end line model Sectional view schematically showing the intermediate line model Measured waveform of characteristic impedance (CPAVS 0.75f) Measured waveform diagram of characteristic impedance (IV8mm ² LFV) Table showing parameter values of transmission line model Schematic diagram showing a transmission line model description example Frequency-characteristic impedance diagram showing an example of simulation reproduction Schematic diagram showing an example of changing the transmission line model description (when adding noise injection points) Schematic diagram showing an example of changing the description of the transmission line model (when changing the noise injection position) Schematic diagram showing an example of changing the description of the transmission line model (when changing the wire laying state) Flow chart showing old and new EMC evaluation methods Schematic diagram showing parameter sweep range

<Wire harness network>
FIG. 1 is a schematic diagram of a wire harness network stretched around a vehicle (= skeleton diagram of the vehicle). The vehicle X in recent years is equipped with a large number of electrical components (various lamps, various pumps, various fans, electronic suspensions, wipers, door locks, power windows, electric door mirrors, etc.). Between the ECU [electronic control unit] X2, a wire harness X3 for transmitting electric power and signals is stretched in and out. As described above, various immunity tests and emission tests are imposed on the vehicle X equipped with a large number of electrical components in order to improve safety and reliability.

  In addition, as a structure which has a wire harness net | network, a railroad, a ship, an aircraft etc. can be mentioned besides a vehicle.

<Electrical component BCI test (ISO11452-4)>
FIG. 2 is a block diagram illustrating a configuration example of the electrical component BCI test. The electrical equipment BCI test is a component test method (ISO 11452-4) for evaluating electrical interference due to narrow-band electromagnetic radiation energy for in-vehicle electronic equipment standardized by the International Organization for Standardization (ISO). Is an immunity test that complies with

  More specifically, the electrical component BCI test is a noise source unit 20 and a detection unit 30 as an actual measurement benchmark for evaluating the immunity characteristics of the circuit unit 100 to be measured (or its simulation unit). , Using the controller 40 and the injection probe 80.

  The measurement target circuit unit 100 corresponds to an actual product (actual machine) on which the device under test 10 (hereinafter referred to as a DUT [device under test] 10) is mounted. In addition to the DUT 10, a battery 50, a power source The filter part 60 and the wire harness 70 are included. The measurement target circuit unit 100 may include a pseudo load of the DUT 10.

  The DUT 10 includes an LSI [large-scale integrated circuit] 11 and a printed wiring board (PCB [printed circuit board]) on which the LSI is mounted. Of course, the LSI 11 alone can be used as the DUT 10. Note that the DUT 10 does not necessarily need to be an actual device, and generally a simulation device for testing is often used.

  In particular, when performing a mutual comparison of a plurality of LSIs (for example, a mutual comparison between a new model LSI and an old model LSI, or a mutual comparison between an in-house LSI and another company's compatible LSI), the components other than the LSI to be evaluated ( It is desirable to use a test simulation device in which the PCB size and wiring pattern, or the types and characteristics of discrete components mounted on the PCB are shared.

  The noise source unit 20 is a main body that injects a high-frequency noise signal (interference wave power) into a terminal of the DUT 10 (the power supply terminal VCC is illustrated in FIG. 2), and includes a signal generator 21, an RF amplifier 22, and a bidirectional coupler. 23, traveling wave side power sensor 24, reflected wave side power sensor 25, power meter 26, and 50Ω transmission line 28.

  A signal generator (SG [signal generator]) 21 generates a sinusoidal high-frequency noise signal. Further, the signal generator 21 may modulate the high frequency noise signal as necessary. The oscillation frequency, amplitude, and modulation of the high frequency noise signal can be controlled by the controller 40. In addition, what is necessary is just to use a pulse generator (PG [pulse generator]) when an interference wave is a pulse, and what is necessary is just to use an impulse generator (IG [impulse generator]) when an interference wave is an impulse.

  The RF [radio frequency] amplifier 22 amplifies the high frequency noise signal generated by the signal generator 21 with a predetermined gain.

  A bidirectional coupler (BDC [bi-directional coupler]) 23 separates the high-frequency noise signal amplified by the RF amplifier 22 into a traveling wave component directed to the DUT 10 and a reflected wave component returned from the DUT 10.

  The traveling wave side power sensor 24 measures the power of the traveling wave component separated by the bidirectional coupler 23. On the other hand, the reflected wave side power sensor 25 measures the power of the reflected wave component separated by the bidirectional coupler 23. It is desirable that each transmission line to the traveling wave side power sensor 24 and the reflected wave side power sensor 25 is in a pseudo cut-off state (for example, impedance: 50Ω or more, power passing characteristic: −20 dBm or less).

  The power meter 26 sends the traveling wave power measured by the traveling wave side power sensor 24 and the reflected wave power measured by the reflected wave side power sensor 25 to the controller 40. The controller 40 calculates the power actually injected into the DUT 10 by performing a difference calculation between the traveling wave power and the reflected wave power, and records the calculation result. In this way, the power injected into the DUT 10 is measured by the power meter 26 at a position far from the DUT 10. Therefore, in order to measure the power injected into the DUT 10 with high accuracy, it is desirable to reduce the cable loss during high-frequency noise signal transmission to a minimum value (for example, 1 dB or less).

  The detection unit 30 monitors the output waveform of the DUT 10 and sends the monitoring result to the controller 40. An oscilloscope or the like can be suitably used as the detection unit 30. In order to prevent the presence of the detection unit 30 from affecting the electrical component BCI test, transmission from the DUT 10 to the detection unit 30 using a high input impedance (1 MΩ) and wideband (3 GHz) differential probe. It is desirable that the line be in a pseudo-blocking state.

  The controller 40 is a main body that performs overall control of the electrical component BCI test. When performing the electrical component BCI test, the controller 40, for example, outputs a signal so as to gradually increase the amplitude (injected power) of the high frequency noise signal while fixing the oscillation frequency of the high frequency noise signal injected into the DUT 10. The generator 21 is controlled. In parallel with the amplitude control described above, the controller 40 determines the malfunction of the LSI 11 according to the monitoring result of the detection unit 30 (such as missing clock signal pulses or frequency disturbance, output voltage non-standard, or communication error). Judgment whether or not it has occurred). Then, the controller 40 acquires the calculation result (injected power to the DUT 10) of the measured value of the power meter 26 at the time of occurrence of malfunction of the LSI 11, and stores this in association with the oscillation frequency currently set. Thereafter, the controller 40 repeats the above measurement while sweeping the oscillation frequency of the high frequency noise signal, thereby obtaining a malfunction power frequency characteristic in which the oscillation frequency of the high frequency noise signal and the injected power at the time of malfunction occurrence are associated with each other. As the controller 40, a personal computer or the like that can sequentially perform the above measurement can be suitably used.

  The battery 50 is a DC power source that supplies power to the DUT 10. For example, when an in-vehicle LSI is to be evaluated, an in-vehicle battery may be used as the battery 50. However, the DC power supply to the DUT 10 is not limited to a battery, and an AC / DC converter that generates desired DC power from commercial AC power can also be used.

  The power supply filter 60 is a circuit unit for putting the transmission line from the noise source unit 20 to the battery 50 into a pseudo-blocking state, and is a power supply impedance stabilization network 61 and 62 (hereinafter, LISN [line impedance stabilization network] 61 and 62). Called). LISNs 61 and 62 both stabilize the apparent impedance of battery 50. The LISN 61 is inserted in a power supply line connecting the positive terminal (+) of the battery 50 and the power terminal (VCC) of the DUT 10, and the LISN 62 is a negative terminal (−) of the battery 50 and the GND terminal of the DUT 10. (VEE) is inserted in the GND line.

  The wire harness 70 is a conductive member of about 1.5 to 2.0 m that electrically connects the DUT 10 and the power supply filter unit 60. The wire harness 70 may be a single wire or a bundle of a plurality of wires. Note that an injection probe (injection transformer) 80 is attached to the wire harness 70 at a predetermined position, and a bulk current is injected through the 50Ω transmission line 28 of the noise source unit 20.

  In the electrical component BCI test, the total length of the wire harness 70 is determined to be 1700 mm-2000 mm. Also, the attachment position of the injection probe 80 (= distance between the DUT 10 and the injection probe 80) is also limited to only three locations of 150 mm, 450 mm, and 750 mm.

<Vehicle BCI test (ISO11451-4)>
FIG. 3 is a block diagram illustrating an example of a vehicle BCI test. The vehicle BCI test is a BCI test performed in a state where the DUT 10 and the wire harness 70 described above are mounted on the vehicle X, and conforms to ISO11451-4.

<Electrical component emission test (CISPR25)>
FIG. 4 is a block diagram illustrating an example of an electrical component emission test. The electrical component emission test in this figure is an actual measurement benchmark for evaluating the emission characteristics of electrical components. The standard CISPR25 “Limit of interference wave for vehicle-mounted receiver protection” created by the International Special Committee on Radio Interference (CISPR) Value and measurement method ”. The electrical component emission test is divided into two types: radiated emission measurement and conducted emission measurement. In the radiated emission measurement, the intensity of noise radiated from the wire harness 70 is measured by the antenna 90. On the other hand, in the conductive emission measurement, the intensity of noise transmitted through the wire harness 70 is measured using the terminal 91 of the power supply filter 60 (not used in the immunity test). Thus, the electrical component emission test is different in configuration and purpose from the previous electrical component BCI test (FIG. 2) and vehicle BCI test (FIG. 3) in that the intensity of noise is measured. However, even in the electrical component emission test, the total length of the wire harness 70 is limited, and there is no difference from the electrical component BCI test (FIG. 2).

<Simulation model>
FIG. 5 is a block diagram illustrating an example of a simulation model. The simulation model A of this configuration example is a model of the entire actual measurement benchmark (electrical component BCI test of FIG. 2). The battery / LISN model A1, the DUT model A2, the BCI injection probe model A3, and the wire harness Model A4 is combined.

  The battery / LISN model A1 is a model of the battery 50 and the power supply filter 60. If not only the battery 50 and the power supply filter 60 but also a control system is connected, a control system model may be added in parallel with the battery / LISN model A1.

  The DUT model A2 is a model of the DUT 10. The DUT model A2 includes an LSI model that models the LSI 11, a PCB model that models a PCB, and an immunity behavior model that represents these immunity behaviors.

  The BCI injection probe model A3 is a model of the injection probe 80.

  The wire harness model A4 is obtained by modeling the wire harness 70. In the wire harness model A4, as parameters for representing the transmission characteristics, according to the parameter L corresponding to the total length of the wire harness 70 and the distance between the DUT 10 and the injection probe 80 (= may be read as a noise injection position) Parameter Lx is included (details will be described later).

  When the wire harness structure of the electrical component BCI test is modeled as it is, the above-described parameters L and Lx are limited in the overall length of the wire harness 70 (1700 to 2000 mm) and the position limit of the injection probe 80 (from DUT 10 to 150 mm, 450 mm). , A position of 750 mm), the value is limited.

<Immunity characteristics evaluation method>
FIG. 6 is a diagram illustrating a comparative example of the malfunction voltage frequency characteristic (solid line) and the ultimate voltage frequency characteristic (broken line).

  The malfunction voltage frequency characteristic is the terminal voltage V_LSI appearing between predetermined points of the LSI 11 indicating the magnitude of the limit high-frequency noise signal that causes the LSI 11 to malfunction. Note that the malfunction voltage frequency characteristic is derived from a malfunction power frequency characteristic obtained by a DPI [direct power injection] test (= the magnitude of the high frequency noise signal at which the DUT 10 malfunctions is represented by the power injected into the DUT 10). Can be sought. On the other hand, the ultimate voltage frequency characteristic is a frequency characteristic of the ultimate voltage V_arr that appears between predetermined points of the LSI 11 in the electrical component BCI test (or a computer simulation that simulates this).

  The immunity characteristic of the LSI 11 can be evaluated by comparing the malfunction voltage frequency characteristic and the ultimate voltage frequency characteristic. For example, in FIG. 6, it can be determined that the LSI 11 may malfunction at an oscillation frequency where the broken line exceeds the solid line. Further, if the same comparison as described above is performed for each terminal of the LSI 11, it is possible to identify a terminal that may cause a malfunction, and thus it is possible to quickly improve the circuit design.

  In this figure, the evaluation method of the immunity characteristic has been described by giving a comparative example of the malfunction voltage frequency characteristic and the ultimate voltage frequency characteristic. For example, the malfunction current frequency characteristic (= high-frequency noise at the limit of causing the LSI 11 to malfunction) Comparison between the magnitude of the signal and the terminal current I_LSI flowing in a predetermined portion of the LSI 11) and the ultimate current frequency characteristic (= the frequency characteristic of the ultimate current I_arr flowing after reaching the predetermined portion of the LSI 11 in the electrical component BCI test) It is also possible to evaluate the immunity characteristics of the LSI 11 by performing the above.

<Wire harness model>
Next, a review of the wire harness simulation model used in the electrical component BCI test (FIG. 2) and electrical component emission test (FIG. 4) is proposed. In particular, this proposal relates to the modeling of common mode impedance in wire harnesses. More specifically, in the following, it is possible to form a wire laying method when bundling a plurality of wires to form a wire harness and to perform high-speed processing corresponding to an actual wire harness structure. A transmission line model is proposed.

  FIG. 7 is a cross-sectional view schematically showing an example of laying a wire harness. In the example of this figure, the wire harness wh is a bundle of five wires w1 to w5. The wires w1 to w5 are laid horizontally so that the respective coating films are in contact with each other. All the wires w1 to w5 are laid away from the ground plane (for example, a copper plate on the table) by a predetermined distance (for example, 50 mm). This laying state is referred to as “parallel laying” in this specification. When the number of wires laid increases, the number of adjacent wires is increased in the horizontal direction.

  In the example shown in the figure, hatched wires w1 and w5 correspond to end lines, and white wires w2 to w4 correspond to intermediate lines. An end line refers to a wire in which no other wire is adjacent to at least one side among a plurality of wires laid in parallel. On the other hand, the intermediate line indicates a state in which other wires are adjacent to both sides thereof. Note that the number of wires laid in parallel may be any number.

  Further, the transmission characteristics of the wire harness are determined by the presence of a GND (ground plane or the like) facing the wire harness. About the relative position of a wire harness and GND, the nearest position is adjacent and the farthest position is infinity. Hereinafter, the transmission characteristic difference between the end line and the intermediate line (= transmission characteristic dependency on the installation position) will be described in detail.

  FIG. 8 is a frequency-gain diagram showing that the transmission characteristics of the wires w1 to w5 have the laying position dependency. In addition, the actual measurement result of this figure shows that the first ends of the five wires w1 to w5 laid in parallel are short-circuited with each other and each second end is a 250Ω termination structure, while the measurement target This wire was obtained in an actual measurement environment in which the terminal resistance was replaced with a series 200Ω resistor. As a matter of course, wires w1 to w5 having substantially the same impedance in terms of DC are used.

  For example, when the transmission characteristic of the wire w1 (solid line) and the transmission characteristic of the wire w2 (small broken line) are compared, there is a difference in the respective transmission characteristics in the frequency band of 40 MHz to 100 MHz, particularly 6 dB at 61 MHz. A difference of (about 4 times) can be confirmed (see thick arrows in the figure). This difference indicates that when the wire harness wh receives interference noise, the interference energy does not propagate uniformly to the wires w1 and w2.

  On the other hand, there is no significant difference in the frequency band between the transmission characteristic of the wire w1 (solid line) and the transmission characteristic of the wire w5 (two-dot chain line). In addition, there is no significant difference in the frequency band between the transmission characteristic of the wire w2 (small broken line), the transmission characteristic of the wire w3 (large broken line), and the transmission characteristic of the wire w4 (one-dot chain line). .

  From the above measurement results, the inventor of the present application pays attention to the fact that the characteristic impedance of the wires w1 to w5 laid in parallel shows a tendency corresponding to each laying state (adjacent state), and at least ends the wires w1 to w5. It came to the knowledge that it can classify | categorize into two types, a partial line group (w1 and w5) and an intermediate line group (w2-w4).

  In order to simplify the conventional wire harness model, the interaction between adjacent wires is ignored, and the wire harness model is uniformly expressed as having a single characteristic impedance. Therefore, in the conventional wire harness model, since the same electric current and voltage generate | occur | produce in all the wires w1-w5 with equal termination conditions, the difference according to each laying state could not be expressed. In addition, since there is no reflection at the lumped constant, it was not possible to express a standing wave depending on the total length of the wire harness wh.

  On the other hand, by classifying the wire harness wh into at least two types of end line groups (w1 and w5) and intermediate line groups (w2 to w4), conventional wire harness models and lumped constants having a single characteristic impedance It becomes possible to reproduce transmission characteristics that could not be expressed.

<Model classification>
9A to 9C are cross-sectional views schematically showing the wire harness, and the hatched wires in each figure are a single wire model (FIG. 9A), an end wire model (FIG. 9B), and Each is modeled as an intermediate line model (FIG. 9C). Also, the bottom side of each figure corresponds to a ground plane.

  The single wire model (FIG. 9A) is a model of a wire (that is, a single wire) in which no other wire exists on both sides thereof. As described above, the single wire model (FIG. 9A) does not correspond to the case where a plurality of wires are laid in parallel, but here, as a basic unit of the transmission line model, an end line model (FIG. 9B) and an intermediate line model. (FIG. 9C) and it demonstrates. The single line model (FIG. 9A) can also be understood as a special example of the end line model (FIG. 9B).

The white arrow in each figure has shown the typical electric force line. As can be seen by comparing each figure, since the electric field distribution differs depending on the laying state of the wires, three types of characteristic impedances (single line model, end line model, intermediate line model) are mixed. In each figure, two types of characteristic impedances Z0 are shown for each model, taking two types of wires (CPAVS0.75f and IV8mm ² LFV) as an example.

For the single wire model (FIG. 9A), Z0 = 300Ω for CPAVS 0.75f and Z0 = 207Ω for IV8 mm ² LFV. For the end line model (FIG. 9B), Z0 = 520Ω for CPAVS 0.75f and Z0 = 364Ω for IV8 mm ² LFV. In the intermediate line model (FIG. 9C), Z0 = 2600Ω for CPAVS0.75f and Z0 = 2400Ω for IV8mm ² LFV.

  Thus, it can be seen that the numerical value of the characteristic impedance Z0 differs by about one digit in the single line model (FIG. 9A), the end line model (FIG. 9B), and the intermediate line model (FIG. 9C).

  FIG. 10 is a measured waveform diagram obtained when deriving the characteristic impedance of CPAVS 0.75f. In addition, about the laying state of the wire harnesses wh11-wh15 used for actual measurement of characteristic impedance, as shown with the legend, wh11 (solid line) is a single line, wh12 (small broken line) is two parallel laying, wh13 (large broken line) ) Is five parallel lays, wh14 (one-dot chain line) is two parallel lays (however, the distance between wires is 100 mm), and wh15 (two-dot chain line) is three lays in parallel (however, the distance between wires is 50 mm).

  As a characteristic impedance measurement method, TDR [time domain reflectometry] is used, the measuring instrument is agilent 8510C (with built-in IFFT [inverse fast fourier transform]), the measurement band is 45 MHz to 18.045 GHz, the number of measurement points is 401, the measurement range Was set to -1 ns to 15 ns. In measuring the characteristic impedance, both ends of each wire were short-circuited, and the characteristic impedance was obtained as the common mode impedance of the wire harness straight portion.

  The actual measurement result of the wire harness wh11 (solid line) was Z0 = 300Ω. The wire harness wh11 can be understood as a single wire itself. Accordingly, the characteristic impedance of the single wire model may be set to “300Ω” (see FIG. 9A).

  The actual measurement result of the wire harness wh12 (small broken line) was Z0 = 260Ω. The wire harness wh12 can be understood as two end lines laid in parallel. Therefore, the characteristic impedance of the end line model may be set to “520Ω (= 260Ω × 2)” (see FIG. 9B).

  The actual measurement result of the wire harness wh13 (large broken line) was Z0 = 200Ω. The wire harness wh13 can be understood as a structure in which two end lines and three intermediate lines are laid in parallel. Therefore, when the characteristic impedance of the intermediate line model is R, the following equation (1) is established.

  1/200 = 2/520 + 3 / R (1)

  By solving the equation (1), the characteristic impedance of the intermediate line model can be obtained as “2600Ω” (see FIG. 9C).

  The actual measurement result of the wire harness wh14 (one-dot chain line) was Z0 = 150Ω, and the actual measurement result of the wire harness wh15 (two-dot chain line) was Z0 = 120Ω. From comparison of these actual measurement results and the actual measurement results (Z0 = 300Ω) of the wire harness wh11 (solid line), when the inter-wire distance is 100 mm or more, the parallel-laid wires exhibit transmission characteristics equivalent to those of a single wire. confirmed.

  Moreover, in any measurement of the wire harnesses wh11 to wh15, a delay time of 4.72 ns / 770 mm was confirmed. From this, the unit delay time per unit length (1 m) can be obtained as “6.13 ns / m”.

FIG. 11 is a measured waveform diagram obtained when deriving the characteristic impedance of IV8 mm ² LFV. In addition, about the laying state of the wire harnesses wh21-wh24 used for actual measurement of characteristic impedance, as shown with the legend, wh21 (solid line) is a single line, wh22 (small broken line) is two parallel laying, wh23 (large broken line) ) Is five parallel laying, and wh24 (one-dot chain line) is two parallel laying (however, the distance between wires is 100 mm). The characteristic impedance measurement method, measuring instrument, measurement band, number of measurement points, and measurement range are the same as those in FIG.

  The actual measurement result of the wire harness wh21 (solid line) was Z0 = 207Ω. The wire harness wh21 can be understood as a single wire itself. Therefore, the characteristic impedance of the single wire model may be set to “207Ω” (see FIG. 9A).

  The actual measurement result of the wire harness wh22 (small broken line) was Z0 = 182Ω. The wire harness wh22 can be understood as two end lines laid in parallel. Accordingly, the characteristic impedance of the end line model may be set to “364Ω (= 182Ω × 2)” (see FIG. 9B).

  The actual measurement result of the wire harness wh23 (large broken line) was Z0 = 149Ω. The wire harness wh23 can be understood as a structure in which two end lines and three intermediate lines are laid in parallel. Therefore, when the characteristic impedance of the intermediate line model is R, the following equation (2) is established.

  1/149 = 2/364 + 3 / R (2)

  By solving the equation (2), the characteristic impedance of the intermediate line model can be obtained as “2400Ω” (see FIG. 9C).

  The actual measurement result of the wire harness wh24 (one-dot chain line) was Z0 = 145Ω. From the comparison between the actual measurement result and the actual measurement result (Z0 = 207Ω) of the wire harness wh21 (solid line), it is confirmed that there is interference between the wires laid in parallel even if the distance between the wires is 100 mm or more. It was.

  Moreover, in any measurement of the wire harnesses wh21 to wh24, a delay time of 5.36 ns / 880 mm was confirmed. From this, the unit delay time per unit length (1 m) can be obtained as “6.09 ns / m”.

<Transmission line model>
Based on the above measurement results, a wire transmission line model (for example, SPICE model) is proposed. FIG. 12 is a table showing the parameter values of the transmission line model. The type of wire (CPAVS0.75f / IV8mm ² LFV), model classification (single line model / end line model / intermediate line model), characteristic impedance, and unit Delay time is shown.

The wire type (= transmission line type) is exemplified by CPAVS0.75f as the low-voltage transmission line (signal line) and IV8mm ² LFV as the high-voltage transmission line (power line). The wire may be modeled.

  In the single-line model of CPAVS 0.75f, the characteristic impedance is set to Z0 = 300 [Ω], and the unit delay time is set to TD = 6.13 [ns / m]. The end line model of CPAVS 0.75f has a characteristic impedance set to Z0 = 520 [Ω] and a unit delay time set to TD = 6.13 [ns / m]. In the intermediate line model of CPAVS 0.75f, the characteristic impedance is set to Z0 = 2600 [Ω], and the unit delay time is set to TD = 6.13 [ns / m].

On the other hand, in the single line model of IV8 mm ² LFV, the characteristic impedance is set to Z0 = 207 [Ω], and the unit delay time is set to TD = 6.09 [ns / m]. In the end line model of IV8 mm ² LFV, the characteristic impedance is set to Z0 = 364 [Ω], and the unit delay time is set to TD = 6.09 [ns / m]. In the IV8 mm ² LFV intermediate line model, the characteristic impedance is set to Z0 = 2400 [Ω], and the unit delay time is set to TD = 6.09 [ns / m].

  Thus, the characteristic impedance of each model is set to a different value according to the model classification of the wire (single line model, end line model, intermediate line model). In particular, when attention is paid to the end line model and the intermediate line model, the characteristic impedance of the end line model is set to a value lower by about one digit than the characteristic impedance of the intermediate line model. On the other hand, the unit delay time of each model is set to the same value regardless of the wire model classification. The characteristic impedance and unit delay time are individually set for each wire type.

FIG. 13 is a schematic diagram illustrating a description example of a transmission line model. In the example of this figure, the wire harness wh is obtained by laying five wires w1 to w5 in parallel, and the total length thereof is L [m]. As for the wire type, it is assumed that the wires w1 and w2 are CPAVS 0.75f, and the wires w3 to w5 are IV8mm ² LFV.

  On the other hand, when paying attention to the laying state of the wires w1 to w5, the wires w1 and w5 are classified as end lines, and the wires w2 to w4 are classified as intermediate lines. Therefore, the wire harness wh can be appropriately expressed by combining the end line model and the intermediate line model.

  As for the description format of the transmission line model, the wire number (name), the first port connection destination of the inner conductor c1, the first port connection destination of the outer conductor c2, the second port connection destination of the inner conductor c1, and the outer conductor c2. Each parameter is described in the order of the second port connection destination, characteristic impedance Z0, and delay time TD (= unit delay time × full length).

  For example, when the description “w1 ND1 GPLANE ND2 GPLANE Z0 = 300 TD = 6 × L” in the upper first line in the balloon is read, “the wire w1 is connected to the node ND1 at the first port connection destination of the internal conductor c1. Yes, the first port connection destination of the external conductor c2 is the ground plane, the second port connection destination of the internal conductor c1 is the node ND2, the second port connection destination of the external conductor c2 is the ground plane, and the characteristic impedance Z0 Is 300 [Ω] and the delay time TD is 6 × L [ns].

  In the upper part of the balloon, a conventional transmission line model in which the wires w1 to w5 are expressed by a single characteristic impedance (Z0 = 300 [Ω]) is described. On the other hand, a new transmission line model in which the wires w1 to w5 are represented by different characteristic impedances according to the respective laying states is described in the lower part of the balloon.

More specifically, the wire w1 is modeled as an end line model (Z0 = 520 [Ω], TD = 6.13 × L [ns]) of CPAVS 0.75f. The wire w2 is modeled as an intermediate line model (Z0 = 2600 [Ω], TD = 6.13 × L [ns]) of CPAVS 0.75f. The wires w3 and w4 are both modeled as an IV8 mm ² LFV intermediate line model (Z0 = 2400 [Ω], TD = 6.09 × L [ns]). The wire w5 is modeled as an IV8mm ² LFV end line model (Z0 = 364 [Ω], TD = 6.09 × L [ns]).

  As described above, the new transmission line model proposed in this section includes a step of classifying the wire to be modeled into two types (or three types including a single line) of an end line and an intermediate line according to the laying state; Two types of end line and intermediate line (or three types including a single line) are individually modeled to generate two types of end line model and intermediate line model (or three types including a single line model); , Is generated through.

  With such a transmission line model, unlike the conventional transmission line model, it is possible to faithfully reproduce the difference in transmission characteristics according to the laying state of the wire (see FIG. 8). Can be reduced.

  In addition, the transmission line model proposed in this section includes a characteristic impedance Z0 and a delay time TD as parameters representing the transmission characteristics. In this respect, there is no difference from the conventional transmission line model (see FIG. Compare upper and lower tiers in 13 balloons). Therefore, there is no significant influence on the preparation time or execution time of EMC computer simulation.

  The transmission line model expression method is roughly divided into a case where loss is taken into account (= with loss) and a case where loss is ignored (= without loss). In the former case, there are various ways of expressing the loss. The total length of the wire harness used in the electrical component BCI test (FIG. 2) and the electrical component emission test (FIG. 4) is about 2 m, and the total length is about 10 m even when mounted on the vehicle. is there. In view of this, it can be said that it is desirable to appropriately use a transmission line model with loss and a transmission line model without loss as needed. Note that the characteristic impedance and unit delay time described above are both numerical examples without loss.

  FIG. 14 is a frequency-characteristic impedance diagram showing an example of reproduction confirmation by transmission line simulation. In addition, the solid line in this figure has shown the simulation value (when a loss is taken into consideration), and the broken line has shown the measured value. From this figure, it can be seen that the behavior of the solid line and the behavior of the broken line agree with each other with high accuracy. For example, in a transmission line model that takes into account the power changed to heat and the power lost due to radiation as losses, the radiation amount can be calculated.

<Application to body testing>
In the previous electrical component BCI test (FIG. 2), one structure is fixed from a wide variety of wire harness structures (there are various types of vehicles) in order to ensure its practical implementation, and Noise injection points were limited to three discrete points.

  However, wire harnesses laid on actual vehicles have various lengths ranging from 100 mm to 2000 mm, and the number of wires is also varied from 1 to 60. Therefore, in the electrical equipment BCI test, it cannot be denied that there are a lot of unpredictable phenomena and many oversights.

  In contrast, in this section, parameters of the transmission line model (for example, characteristic impedance, delay time, and number of installed cables) that model the wire harness are variable values, and these parameters are swept within a predetermined range. A computer simulation method for evaluating the immunity characteristics or emission characteristics of a DUT is proposed.

  First, the following describes how the description of the transmission line model changes, giving some specific examples of parameter changes.

  FIG. 15 is a schematic diagram showing how to change the description content of the transmission line model when adding noise injection points from one place to two places.

  As shown in the upper part of the figure, at one place of the wire W (full length: L) laid between the signal node SIG1 and the signal node SIG2 (in the example of the figure, the wire W is divided into two equal parts). When the noise injection point INJ1 is attached, the portion laid between the signal node SIG1 and the noise injection point INJ1 is understood as a divided wire W1 (length: L / 2), and the noise injection point INJ1 By understanding the portion laid between the signal node SIG2 and the split wire W2 (length: L / 2), for example, the transmission line model can be described as follows.

W1 SIG1 GPLANE INJ1 GPLANE Z0 = 300 TD = 6
W2 INJ1 GPLANE SIG2 GPLANE Z0 = 300 TD = 6

  On the other hand, as shown in the lower part of the figure, when the noise injection points INJ1 and INJ2 are attached to two places of the wire W (the point where the wire W is equally divided into three in the example of the figure), the signal node The part laid between SIG1 and the noise injection point INJ1 is understood as a split wire W3 (length: L / 3), and the part laid between the noise injection point INJ1 and the noise injection point INJ2 is the split wire. By understanding as W4 (length: L / 3) and understanding the part laid between the noise injection point INJ2 and the signal node SIG2 as the divided wire W5 (length: L / 3), for example, A transmission line model can be described as follows.

W3 SIG1 GPLANE INJ1 GPLANE Z0 = 300 TD = 4
W4 INJ1 GPLANE INJ2 GPLANE Z0 = 300 TD = 4
W5 INJ2 GPLANE SIG2 GPLANE Z0 = 300 TD = 4

  As described above, when the number of noise injection points is increased, the number of wire divisions increases, and accordingly, the number of description lines of the transmission line model may be increased as appropriate. In addition, when adding noise injection points, the length of the divided wires changes, and accordingly, the delay time TD of the transmission line model may be rewritten as appropriate.

  FIG. 16 is a schematic diagram showing how the description content of the transmission line model should be changed when the noise injection position is changed.

  In the upper part of this figure, similarly to the upper part of FIG. 15, the noise injection point INJ1 is attached to a point that bisects the wire W (full length: L) laid between the signal node SIG1 and the signal node SIG2. . Therefore, the transmission line model can be described as follows.

W1 SIG1 GPLANE INJ1 GPLANE Z0 = 300 TD = 6
W2 INJ1 GPLANE SIG2 GPLANE Z0 = 300 TD = 6

  On the other hand, in the lower part of the figure, the noise injection point INJ1 is not a point that bisects the wire W, but one point that divides the wire W into three parts (in the example of this figure, the length of the divided wire W1 is L / 3, and the length of the split wire W2 is 2L / 3). Therefore, the transmission line model can be described as follows.

W1 SIG1 GPLANE INJ1 GPLANE Z0 = 300 TD = 4
W2 INJ1 GPLANE SIG2 GPLANE Z0 = 300 TD = 8

  As described above, when the noise injection position is changed, the length of the split wire changes, and accordingly, the delay time TD of the transmission line model may be appropriately rewritten in accordance with this. Further, although not shown again, it goes without saying that a change in the overall length of the wire can also be handled by rewriting the delay time TD.

  FIG. 17 is a schematic diagram showing how the description content of the transmission line model should be changed when the wire laying state is changed.

In the upper part of the figure, as in FIG. 13, five wires w1 to w5 (full length: L) are laid in parallel between the node ND1 and the node ND2. In addition, about a wire classification, the wires w1 and w2 are CPAVS0.75f, and the wires w3-w5 are IV8mm < ² > LFV. Further, the wires w1 and w5 are classified as end lines, and the wires w2 to w4 are classified as intermediate lines. Therefore, the transmission line model can be described as follows.

w1 ND1 GPLANE ND2 GPLANE Z0 = 520 TD = 6.13xL
w2 ND1 GPLANE ND2 GPLANE Z0 = 2600 TD = 6.13xL
w3 ND1 GPLANE ND2 GPLANE Z0 = 2400 TD = 6.09xL
w4 ND1 GPLANE ND2 GPLANE Z0 = 2400 TD = 6.09xL
w5 ND1 GPLANE ND2 GPLANE Z0 = 364 TD = 6.09xL

On the other hand, in the lower part of the figure, the wire w3 is changed from IV8 mm ² LFV to CPAVS 0.75f. The wire w5 is changed from the end line to the intermediate line. Further, a wire w6 (CPAVS 0.75f) is additionally provided as a new end line. At this time, the description content of the transmission line model may be changed as follows.

w1 ND1 GPLANE ND2 GPLANE Z0 = 520 TD = 6.13xL
w2 ND1 GPLANE ND2 GPLANE Z0 = 2600 TD = 6.13xL
w3 ND1 GPLANE ND2 GPLANE Z0 = 2600 TD = 6.13xL
w4 ND1 GPLANE ND2 GPLANE Z0 = 2400 TD = 6.09xL
w5 ND1 GPLANE ND2 GPLANE Z0 = 2400 TD = 6.09xL
w6 ND1 GPLANE ND2 GPLANE Z0 = 520 TD = 6.13xL

The change part of the above-mentioned description content is demonstrated. First, for the wire w3, the characteristic impedance Z0 of the wire w3 is changed from “2400” to “2600” in accordance with the change of the wire type (IV8 mm ² LFV → CPAVS0.75f), and the delay time TD of the wire w3 is changed. “6.09 × L” is changed to “6.13 × L”. For the wire w5, the characteristic impedance Z0 of the wire w5 is changed from “364” to “2400” in accordance with the change of the model classification (end line → intermediate line). Further, with the addition of the wire w6, one description line of the wire w6 is added. The description content of the wire w6 is the same as the description content of the wire w1.

  As described above, by appropriately changing the parameters of the transmission line model (for example, characteristic impedance, delay time, and the number of installed cables), it becomes possible to easily represent various electrical equipment actual measurement environment structures, It becomes possible to reproduce the wire harness structure laid on the cable. Therefore, phenomena that can actually occur can be sufficiently covered by computer simulation without being restricted by the constraints of the actual measurement benchmark.

  FIG. 18 is a flowchart showing a comparison between old and new EMC evaluation methods. In addition, the work flow of a general EMC evaluation method is shown in the left frame of the figure. On the other hand, the right frame of the figure shows the work flow of the new EMC evaluation method proposed in this section.

  As shown in the left frame of this figure, in a general EMC evaluation method, first, in step S11, a wire harness structure for each vehicle is described. In this wire harness structure, a wire harness network actually stretched around a vehicle is analyzed at a three-dimensional level, and the contents of the structure are described in detail based on the analysis result.

  Next, in step S12, an electromagnetic field simulation is performed using the above-described wire harness structure, and in a subsequent step S13, a transmission line circuit model fixed for each vehicle is generated. However, as a matter of course, there is a restriction that only one transmission line circuit model can be generated per electromagnetic field simulation in step S12.

  Thereafter, in step S14, EMC evaluation (= immunity characteristic or emission characteristic evaluation) of the electrical component is performed by computer simulation using the transmission line circuit model. However, as described above, only one transmission line circuit model can be generated for each electromagnetic field simulation. Therefore, when it is desired to perform EMC evaluation of electrical components using a plurality of types of transmission line circuit models, the electromagnetic field simulation of step S12 is performed while changing the conditions for the type of transmission line circuit model (= number of fixed shapes). Need to repeat.

  However, at least several tens of hours are required to perform one electromagnetic field simulation, and when the simulation accuracy is increased, the required time may reach several hundred hours. Therefore, for example, many of the condition changes (addition of noise injection point, change of noise injection position, change of total wire length, and change of wire laying state) illustrated in FIGS. If an attempt is made to generate various types of transmission line circuit models, hundreds to thousands of hours are required, which is not a realistic method.

  As described above, the EMC evaluation flow in the left frame of this figure is based on the premise that the vehicle is specified first, so that its versatility is not high. Therefore, it is unsuitable for EMC evaluation of electrical components mounted on unspecified vehicles and computer simulation assuming changes in the wire harness structure that occur during actual traveling of the vehicle.

On the other hand, as shown in the right frame of this figure, in the new EMC evaluation method proposed in this section, first, in step S21, the characteristic impedance of the wire harness is measured. This characteristic impedance measurement may be performed for each wire type (for example, CPAVS 0.75f and IV8 mm ² LFV). Since the specific content of this step has already been described with reference to FIGS. 10 and 11, a duplicate description is omitted. The characteristic impedance of the wire harness may be acquired by unit length electromagnetic field simulation.

  Next, in step S22, model classification (an end line, an intermediate line, and a single line) is performed for a plurality of wires forming the wire harness. This model classification may be performed for each wire type as in the previous characteristic impedance measurement. Since the specific content of this step has already been described with reference to FIGS. 9A to 9C and FIG. 12, redundant description will be omitted.

  Thereafter, in step S23, a variable transmission line circuit model is generated by appropriately combining a plurality of subdivided transmission line models and various elements (DUT model, LISN model, battery model, etc.) connected thereto. Is done. In other words, the transmission line circuit model generated in this step includes parameters related to the noise injection position and the laying state of the wire (and thus the wire harness structure itself). By setting these values as variable values, A wide variety of test conditions can be reproduced.

  Based on this, in the subsequent step S24, EMC evaluation of electrical components is performed by appropriately sweeping various parameters (for example, characteristic impedance, delay time, and number of installed lines) by computer simulation using the above transmission line circuit model. Is done. That is, in this step, it is possible to reproduce various test conditions (= wire harness structure) by changing various parameters without repeating the electromagnetic field simulation (see step S12) requiring a long time many times. . Therefore, the worst-case screening can be performed very efficiently in a short time.

  Thus, the old and new EMC evaluation methods differ greatly in whether the test condition changing operation is rate-limited by the electromagnetic field simulation. In other words, with the new EMC evaluation method proposed in this section, the test conditions can be continuously set independently of the electromagnetic field simulation by parameterizing various vehicle structures without forcing them into one. Can be changed. Therefore, since the degree of freedom in setting test conditions can be increased, it is possible to evaluate the immunity characteristic or emission characteristic of the electrical component more correctly than before.

<Parameter sweep range>
FIG. 19 is a schematic diagram showing a sweep range of various parameters (characteristic impedance, wire total length, noise injection position, and number of wires) in step S24.

  The characteristic impedance Z0 is swept so as to reproduce the laying state variation or type change of the wire. In addition to changes in the model classification (end line model, intermediate line model, and single line model) described earlier, wire position deviation (running vibration, secular change, temperature change, or It is possible to include state variations that may affect the characteristic impedance of the wire, such as a change in the relative distance between the wire and the ground plane due to a change in humidity, etc.), a change in the vehicle type (body structure), a change in the body material, and the like.

  Note that the sweep range of the characteristic impedance Z0 may be set to (300−α) Ω ≦ Z0 ≦ (300 + β) Ω so as to include a value (for example, 300Ω) on which restrictions equivalent to those of the actual measurement benchmark are included. Further, the sweep range of the wire total length L and the noise injection position Lx may be set so as to include values imposed with the same constraints as the actual measurement benchmark. For example, the sweep range of the total length L of the wire may be set to 100 mm ≦ L ≦ 2000 mm in consideration of the laying length of the wire considered in an actual machine while including 1500 mm to 1700 mm. For example, the sweep range of the noise injection position Lx may be set to 0 mm ≦ Lx ≦ Lmm so as to include 150 mm, 450 mm, and 750 mm.

  As described above, if the sweep range of the characteristic impedance Z0, the total length L of the wire, and the noise injection position Lx is set, the verification of the simulation result (= verification of the simulation result and the actual measurement result) is performed using the previous actual measurement benchmark. Can be done.

  When sweeping the wire total length L and the noise injection position Lx, the delay time TD is swept so as to reproduce this.

  Further, the sweep range of the number N of wires may be set to 1 ≦ N ≦ 60 in consideration of an actual wire harness.

  In the above, an example in which the sweep range of various parameters is set based on an actual measurement benchmark has been described. However, the setting method is not limited to this, and for example, a structure description of a transmission line circuit in an actual machine (FIG. 18). The sweep range of various parameters may be set so as to include the value obtained in step S11).

  According to such a setting, it is possible to perform a computer simulation that faithfully reflects various conditions that can occur in an actual vehicle. Therefore, for example, in the conventional EMC evaluation method (the left frame in FIG. 18), an event that has been overlooked no matter how long it takes (for example, unintended immunity characteristics and emission characteristics caused by the positional deviation of the wire due to running vibration) It is possible to evaluate without even overlooking this.

<Other variations>
The various technical features disclosed in the present specification can be variously modified within the scope of the technical creation in addition to the above-described embodiment. That is, the above-described embodiment is to be considered in all respects as illustrative and not restrictive, and the technical scope of the present invention is indicated not by the description of the above-described embodiment but by the scope of the claims. It should be understood that all modifications that fall within the meaning and range equivalent to the terms of the claims are included.

  The invention disclosed in the present specification is used for, for example, EMC computer simulation for evaluating immunity characteristics or emission characteristics of a structure (vehicle, railway, ship, aircraft, etc.) having a conductive wire harness. Is possible.

10 Device under test (DUT)
11 LSI
DESCRIPTION OF SYMBOLS 20 Noise source part 21 Signal generator 22 RF amplifier 23 Bidirectional coupler 24 Traveling wave side power sensor 25 Reflected wave side power sensor 26 Power meter 28 50 ohm transmission line 30 Detection part (Oscillator etc.)
40 Controller (PC etc.)
50 Battery 60 Power supply filter 61, 62 Power supply impedance stabilization network (LISN)
70 Wire harness 80 Injection probe 90 Antenna 91 Terminal 100 Circuit unit to be measured A Simulation model A1 Battery / LISN model A2 DUT model A3 BCI injection probe model A4 Wire harness model (transmission line model)
wh, wh11-wh15, wh21-wh24 Wire harness w1-w6, W wire W1-W5 Split wire SIG1, SIG2 Signal node INJ1, INJ2 Noise injection point c1 Internal conductor c2 External conductor X Vehicle X1 Battery X2 ECU
X3 wire harness

Claims (18)

Classifying the transmission line to be modeled into at least two types of end lines and intermediate lines according to the installed state;
Modeling the end line and the intermediate line individually to generate an end line model and an intermediate line model;
It is characterized by having
Transmission line model generation method for computer simulation.   The transmission line model generation method according to claim 1, wherein the end line model and the intermediate line model include characteristic impedance and delay time as parameters representing respective transmission characteristics.   The transmission line model generation method according to claim 2, wherein the end line model and the intermediate line model have different characteristic impedances.   4. The transmission line model generation method according to claim 3, wherein the characteristic impedance of the end line model is set to a value lower than the characteristic impedance of the intermediate line model.   The transmission line model generation method according to any one of claims 2 to 4, wherein the delay time is set according to a laying length of the transmission line.   6. The transmission line model generation method according to claim 5, wherein the unit delay time per unit length is set to the same value for both the end line model and the intermediate line model.   The transmission line model generation method according to any one of claims 2 to 6, wherein the characteristic impedance and the delay time are individually set for each type of the transmission line.   The transmission according to any one of claims 1 to 7, wherein the transmission line is further classified into single wires according to the laying state, and a single wire model obtained by modeling the single transmission wire is generated separately. Line model generation method.   Using the transmission line model generated by the transmission line model generation method according to any one of claims 1 to 8, the immunity characteristic or emission characteristic of a structure having a transmission line is evaluated. Computer simulation method.   The computer simulation method according to claim 9, wherein the transmission line forms a wire harness laid on a vehicle, a railway, a ship, or an aircraft.   A computer simulation method characterized in that a parameter of a transmission line model obtained by modeling a transmission line to which a device under test is connected is a variable value, and the immunity characteristic or emission characteristic of the device under test is evaluated while sweeping the parameter. .   The sweep range of the parameter includes a value imposed with a constraint equivalent to that of an actual measurement benchmark or a value obtained from a structure description of a transmission line circuit in an actual machine. Computer simulation method.   The computer simulation method according to claim 12, wherein the transmission line model includes a characteristic impedance and a delay time as parameters representing the transmission characteristic.   The computer simulation method according to claim 13, wherein the delay time is swept so as to reproduce a change in the overall length of the transmission line or a change in position of a noise injection point.   The computer simulation method according to claim 13 or 14, wherein the characteristic impedance is swept so as to reproduce a laying state variation or a type change of the transmission line.   The transmission line model is classified into at least an end line model and an intermediate line model according to the laying state of the transmission line, and each characteristic impedance is set to a different value. The computer simulation method according to any one of claims 13 to 15.   17. The immunity characteristic or the emission characteristic of the device under test is evaluated while setting the number of laid transmission lines as a variable value and sweeping the number of laid lines. 17. Computer simulation method.   The computer simulation method according to claim 11, wherein the transmission line forms a wire harness laid on a vehicle, a railroad, a ship, or an aircraft.

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