JP4684188B2 - Circuit model creation program, computer-readable recording medium storing circuit model creation program, and circuit model creation device - Google Patents

Description

The present invention relates to a cooperative analysis that combines an electromagnetic field analysis method using a time domain finite difference method and a circuit analysis method using a transient electric circuit analysis. In particular, the present invention relates to a technique for creating a circuit model to be used for cooperative analysis.

  In electromagnetic field circuit linkage analysis, analysis is performed while associating an electric field or magnetic field defined in electromagnetic field analysis with a voltage or current defined in circuit analysis. Numerical simulation that combines electromagnetic field analysis and circuit analysis has the characteristic that the characteristics of circuit elements and surrounding electromagnetic field phenomena can be analyzed in a unified manner, which is very useful for analyzing high-frequency signals propagating in a circuit. It is generally known to be useful.

  The time domain finite difference method (hereinafter referred to as “FDTD (Finite Difference Time Domain) method”), which is one method of electromagnetic field analysis as described above, divides the analysis region by a grid, and an unknown electromagnetic field at a grid point. Is to arrange. In the FDTD method, analysis is performed by a structure called a Yee lattice in which a lattice for arranging an electric field and a lattice for arranging a magnetic field are shifted by half the width of the lattice. In the FDTD method, a relational expression that works between these electric fields and adjacent magnetic fields and electric fields is derived by differentiating Maxwell's electromagnetic field equation, and the electric field and the magnetic field are expressed in units of a certain time step. It is an analysis method to obtain the entire electromagnetic field behavior by updating to. According to this analysis method, the electric field and the magnetic field can be obtained alternately by updating the electric field at a certain time step, updating the magnetic field after ½ time step, and updating the electric field after one time step. .

  Currently, a SPICE (Simulation Program with Integrated Circuit Emphasis) simulator developed by the University of California, Berkeley is known as a transient electrical circuit analysis tool. The tool provides an efficient way to simulate processes in very complex electronic devices.

Non-Patent Document 1 proposes a method combining a FDTD method and a circuit simulator such as SPICE as a method of simulating a circuit such as an integrated circuit. In the electromagnetic field circuit linkage analysis that couples the conventional FDTD method and a circuit simulator (SPICE in this case), a circuit element is incorporated in the FDTD mesh , and a current source is connected between terminals corresponding to one side of the mesh. A technique (current source method) that combines the FDTD method and circuit analysis by arranging capacitors is used.

  Non-Patent Document 2 proposes a method (black box model method) in which an active circuit is incorporated into the FDTD method by modeling with an S parameter. In this method, first, an S parameter in the frequency domain is converted into an expression in the time domain by inverse Fourier transform. And an incident wave is derived | led-out from a reflected wave, a transmitted wave, and an observation wave. Finally, the high frequency circuit is simulated by the FDTD method using the S parameter.

  When applying electromagnetic field analysis as described above to a circuit board including circuit elements, it is necessary to create a model for analyzing the circuit. Here, as an example, consider model creation by the current source method.

FIG. 9 is a diagram illustrating an example of a model based on the current source method.
With reference to FIG. 9, model creation by the current source method will be described. FIG. 9A is a diagram showing a two-dimensional electromagnetic field analysis model in which the circuit board is divided into meshes . FIG. 9B is a diagram illustrating the distance between terminals with respect to the model shown in FIG. It is a figure which shows the example which made distance 1 mesh .

As shown in FIG. 9A, in order to perform electromagnetic field analysis by the FDTD method, a model in which the circuit board is divided into meshes is created based on the design data of the circuit board. The circuit board 1 includes a ground terminal GND and terminals a, b, and c.

The current source method, as described above, to place the current source and the capacitor between the terminals corresponding to one side of the mesh, it is necessary to set the interval between the terminals in a pair as an analysis target of the terminal 1 mesh . For this reason, a conductor is produced | generated from the terminal which is paired, respectively, and the distance between terminals is 1 mesh .

FIG. 9B shows an example in which the distance between terminals is 1 mesh with respect to the model of FIG. 9A. In FIG. 9B, a thick line indicates a conductor.

In FIG. 9B, conductors are respectively generated from the ground terminal GND and the terminals a, b, and c. A current source 92 is inserted between terminals corresponding to one side of the mesh .

Here, the inserted current source is shown for the sake of convenience to indicate the current observation position of the current source method, and is open in the analysis model in the actual FDTD method. Similar processing is also required when a circuit element is handled by circuit analysis that requires a paired terminal, such as a black box model method.
A. Thomas, et al .: The use of SPICE lumped circuits as sub-grid models for FDTD analysis, IEEE Microwave Guided Wave Letters, vol. 4, pp. 141-143 (1994) Akihiro Tsujimura, Shuichi Sekine, Hiroki Shoki: High-frequency circuit analysis by FDTD method based on modeling using S-parameters, IEICE Transactions B, vol. J85-B, No.9, pp. 1526-1534 ( 2002)

However, when creating the circuit model as described above, there may be a plurality of conductor paths that connect the paired terminals. In such a case, automatic modeling by a computer is difficult.

The present invention was made in order to solve the foregoing problems, the object, the circuit model creation program that uniquely create a circuit model necessary for electromagnetic field analysis from the circuit board design data Is to provide.

  According to one aspect of the present invention, there is provided a model creation program for causing a computer having an arithmetic processing unit to execute a model generating process used when performing electromagnetic circuit cooperation analysis on a circuit board. However, the step of dividing the circuit board into meshes, and the arithmetic processing unit generates a conductor surface corresponding to a predetermined terminal that becomes a reference potential when the circuit analysis is performed, and then the conductor surface is perpendicular to the circuit board. Assuming that the positions are shifted by the mesh, the step of specifying the position on the conductor surface corresponding to the predetermined terminal and the arithmetic processing unit are required for the predetermined circuit analysis between the conductor surface and the terminal to be analyzed. Specifying a position where the circuit element is arranged.

  Preferably, in the step of specifying the position on the conductor surface, the arithmetic processing unit generates a conductor surface including a terminal corresponding to the terminal on the circuit board.

  Preferably, in the step of specifying the position on the conductor surface, the arithmetic processing unit generates a conductor surface from which a mesh including a terminal corresponding to a terminal other than the predetermined terminal on the circuit board is deleted.

  Preferably, the step of dividing the circuit board into meshes includes a step in which the arithmetic processing unit calculates mesh coordinates from the mesh-divided circuit board, and the arithmetic processing unit includes a plurality of spatial coordinates on each vertex of the mesh and a plurality of points on the circuit board. Calculating the mesh coordinates of the terminal from the space coordinates of the terminal.

  When the other situation of this invention is followed, the computer-readable recording medium which stored the above-mentioned model creation program is provided.

  According to still another aspect of the present invention, there is provided a model creation device for executing a model creation process used when performing electromagnetic circuit cooperation analysis on a circuit board, wherein data representing a three-dimensional shape of the circuit board is obtained. A storage device for storing and an arithmetic processing device for executing model creation processing are provided. The arithmetic processing device corresponds to a means for dividing a circuit board into meshes and a predetermined terminal that becomes a reference potential when performing circuit analysis. A conductor surface to be generated, the conductor surface is arranged by shifting by 1 mesh in the direction perpendicular to the circuit board, a means for specifying a position on the conductor surface corresponding to a predetermined terminal, the conductor surface and the terminal to be analyzed And a means for specifying a position where a circuit element required for a predetermined circuit analysis is arranged.

According to the present invention, a circuit model necessary for electromagnetic field analysis can be uniquely created from design data. Thereby, the circuit model creation time can be shortened. Therefore, electromagnetic field circuit linkage analysis can be performed efficiently.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  As will be apparent from the following description, the model creation program for executing the model creation method of the present invention uniquely creates a model necessary for electromagnetic field analysis of a circuit board from design data. Thereby, the model creation time can be shortened.

  Note that the “circuit board” in the present embodiment refers to an integrated circuit, a resistor, a capacitor on a printed board in which circuit wiring is configured with a conductor such as copper foil on a board impregnated with an insulating resin. The electronic parts such as are mounted. These electronic components are called “circuit elements”, and the terminals of the circuit elements are called “circuit terminals”.

  In the following description, a model used when performing electromagnetic field analysis is referred to as an “electromagnetic field analysis model”, and a model used when performing circuit analysis is referred to as a “circuit model”. Furthermore, the “electromagnetic field analysis model” and the “circuit model” are collectively referred to as a “model”.

(1. System configuration of the present invention)
FIG. 1 is a conceptual diagram showing an example of a computer 100 that executes an electromagnetic field circuit link analysis program using the model creation method of the present invention.

  In FIG. 1, a computer 100 for executing a program for cooperative analysis includes an optical disk drive 108 for reading information on an optical disk such as a CD-ROM (Compact Disc Read-Only Memory) 118 and a flexible disk (Flexible Disk). (Hereinafter referred to as “FD”) 116, a computer main body 102 having an FD drive 106 for reading and writing information, a display 104 as a display device connected to the computer main body 102, and also connected to the computer main body 102. A keyboard 110 and a mouse 112 are provided as input devices.

FIG. 2 is a block diagram showing the configuration of the computer 100.
As shown in FIG. 2, in addition to the optical disk drive 108 and the FD drive 106, the computer main body 102 constituting the computer 100 includes a CPU (Central Processing Unit) 120 connected to the bus 105 and a ROM (Read Only). A memory 122 including a memory (RAM) and a random access memory (RAM), a direct access memory device such as a hard disk 124, and a communication interface 128 for exchanging data with the outside are included. An optical disk such as a CD-ROM 118 is loaded in the optical disk drive 108. An FD 116 is attached to the FD drive 106.

  In the hard disk 124, parameters representing physical properties such as the shape of the substrate, the dielectric constant of the substrate, the shape of the circuit element to be analyzed, signal terminal information, analysis conditions, etc. are stored for the circuit substrate to be analyzed. For each circuit element to be analyzed, a terminal paired with netlist information, S parameter information, and analysis target corresponding to an analysis method (current source method, voltage source method, black box method, etc.) An analysis target model 135 storing a pair of terminal names, a program 136 for executing FDTD, which is one of methods for performing electromagnetic analysis in the time domain, a program 137 for executing circuit analysis, and the like are stored. Here, for example, the design data 134 and the analysis target model 135 may be supplied from an external database via the communication interface 128. Each program may be supplied by a recording medium such as the FD 116 or the CD-ROM 118, or may be supplied by another computer via a communication line. The execution of FDTD or circuit analysis may be executed by an external computer via the communication interface 128 and the result may be stored in the hard disk 124.

  In addition, in a storage area of the storage device, for example, the hard disk 124, an electric field value storage area for temporarily storing electric field values and magnetic field values as analysis results during the electromagnetic field analysis, and updating those values in the next step. 138 and a magnetic field value storage area 139 are provided.

  Here, the program 136 for executing FDTD and the program 137 for executing circuit analysis are collectively referred to as an electromagnetic circuit cooperation analysis program.

  Therefore, in the following description, it is assumed that time domain electromagnetic field analysis and circuit analysis are executed in cooperation within one computer device. However, the electromagnetic field analysis and the circuit analysis may be executed by separate computer devices, and data may be exchanged between the separate computer devices via the communication interface 128 to perform the cooperative analysis.

  The CPU 120 functioning as an arithmetic processing unit uses the memory 122 as a working memory to execute processing corresponding to the above-described program 136 for executing FDTD and the program 137 for executing circuit analysis.

  The CD-ROM 118 may be another medium, such as a DVD-ROM (Digital Versatile Disc) or a memory card, as long as it can record information such as a program installed in the computer main body. In this case, the computer main body 102 is provided with a drive device that can read these media.

  The program 136 for executing FDTD and the program 137 for executing circuit analysis are software executed by the CPU 120 as described above. In general, such software is stored and distributed in a recording medium such as the CD-ROM 118 or the FD 116, read from the recording medium by the optical disk drive 108 or the FD drive 106, and temporarily stored in the hard disk 124. Alternatively, when the computer 100 is connected to the network, it is temporarily copied from the server on the network to the hard disk 124. Then, the data is further read from the hard disk 124 to the RAM in the memory 122 and executed by the CPU 120. In the case of network connection, the program may be directly loaded into the RAM and executed without being stored in the hard disk 124.

FIG. 3 is a functional block diagram showing a functional configuration of the CPU 120.
The functional configuration of the CPU 120 will be described with reference to FIG.

  The CPU 120 includes a model creation unit 30 that creates a model, and an electromagnetic field circuit cooperation analysis execution unit 32 that executes electromagnetic field analysis in accordance with an electromagnetic field circuit cooperation program.

  The model creation unit 30 obtains the three-dimensional shape of the part to be analyzed from the design data 134, the terminal name information, the mesh size given as the analysis condition, and the information by analysis method and the terminal name from the analysis target model 135. get. And based on these, the electromagnetic field analysis model in FDTD used by electromagnetic field analysis is created.

  The electromagnetic field circuit cooperation analysis execution unit 32 includes the electromagnetic field analysis model in the FDTD created by the model creation unit 30, the netlist and behavior model required for circuit analysis from the analysis target model 135, medium information and power supply information in the analysis region Get etc. Based on these, the total electromagnetic field component in the analysis region is calculated.

  Note that the computer hardware itself and its operating principle shown in FIGS. 1 and 2 are general. Therefore, an essential part for realizing the functions of the present invention is software stored in a recording medium such as the FD 116, the CD-ROM 118, and the hard disk 124.

  As a general tendency, various program modules are prepared as a part of a computer operating system, and an application program is called to advance the processing by calling these modules in a predetermined arrangement when necessary. . In such a case, the software itself does not include such a module, and the electromagnetic field circuit linkage analysis is possible only when the computer cooperates with the operating system. However, as long as a general platform is used, it is not necessary to distribute software including such modules, and the software itself not including these modules and the recording medium storing the software (and the software distributes on the network). Data signal) can be considered to constitute the embodiment.

(2. Electromagnetic circuit linkage analysis method)
Hereinafter, an electromagnetic field circuit cooperation analysis method according to the present invention will be described.

(2.1 Cooperative analysis method between electromagnetic field analysis and circuit analysis)
First, the FDTD method, which is one of the methods for performing electromagnetic field analysis, will be described, and then the current source method will be described as an example of the analysis method used for cooperative analysis.

The FDTD method is a numerical calculation method by differentiating Maxwell's electromagnetic field equation. First, an analysis region is divided by a lattice, and an electric field is arranged at the center of each side of the lattice, and a magnetic field is arranged at the center of each surface. Then, when Maxwell's equations are differentiated, the electric and magnetic fields are arranged at positions that are spatially shifted by half a mesh and temporally by a half time step. Here, the following equations (1) and (2) are obtained by deriving from the Maxwell equation based on electromagnetics the unknown electric field to be obtained, the known electric field adjacent to the unknown magnetic field and the known electric field one time step before and the known magnetic field. It becomes like this.

In the formula, bold indicates that the variable is a vector.
Equation (1) is an electric field E (vector) of n time steps, and equation (2) is a relational equation of magnetic field H (vector) of (n + 1/2) time steps. However, Δt, μ, ε, and σ are time step, magnetic permeability, dielectric constant, and conductivity, respectively.

  By updating the unknown electric field and unknown magnetic field in units of a certain time step Δt based on these, the electromagnetic field behavior of the entire analysis region can be obtained in the time domain.

  As described above, in the FDTD method, the time domain electromagnetic field response to be analyzed can be analyzed by sequentially calculating the unknown electric field and the unknown magnetic field in the analysis region by the explicit method.

  Next, the current source method, which is one of the methods for directly combining the FDTD method and the circuit analysis, used for electromagnetic field circuit linkage analysis will be described.

FIG. 4 is a schematic diagram of cooperative analysis by the current source method. 4A is a diagram illustrating an FDTD mesh including circuit elements to be subjected to circuit analysis, and FIG. 4B is a diagram illustrating a schematic processing flow of the current source method. (C) is a figure which shows the equivalent circuit of the current source method corresponding to the mesh of FIG. 4 (A).

The current source method will be described with reference to FIG. In FIG. 4A, the electric field is assigned in the direction of the arrow along the side of the lattice mesh indicated by the solid line, and the magnetic field is assigned in the direction of the arrow along the side of the lattice mesh indicated by the dotted line. Δx, Δy, Δz indicate the length of each side of the FDTD mesh , and the solid grid mesh and the dotted grid mesh are shifted from each other by 1 / 2Δx, 1 / 2Δy, 1 / 2Δz. Here, it is assumed that a circuit element to be subjected to operation analysis by circuit analysis is arranged on a side ab where an electric field is present.

With reference to FIG. 4B, the flow of processing of the current source method will be described. First, the magnetic field of the mesh is calculated by the FDTD method (step S400).

And if the law of an ampere is applied to the mesh containing a circuit element and it expand | deploys about z component, the following formula | equation (3) will be obtained.

However, JL is the density of the conductive current flowing through the element.
Here, assuming that ε (ΔxΔy) / Δz in the first term on the left side of Equation (3) is equivalent to the capacitance C0 of the parallel plate capacitor, and the right side is the total current I flowing through the mesh , Equation (3) is It can be rewritten as equation (4).

Where VL is the voltage across the circuit element, and IL is the total current flowing through the circuit element.
The total current I flowing through the mesh can be obtained by circular integration of the magnetic field around the element along the surface 40 using Ampere's law. However, since the magnetic field is constant, I can be considered as a constant current source. . Therefore, equation (4) can be considered as an equivalent circuit including a current source 42, a capacitor 44, and a network 46 as shown in FIG.

Returning to FIG. 4B again, by calculating the current I from the magnetic field H obtained by FDTD and passing it to the circuit analysis as the current source value I (step S402), VL and IL can be obtained by the circuit analysis. . Then, VL is obtained by circuit analysis, and VL is passed to the FDTD method in order to calculate the electric field on the mesh side of the circuit element (step S404). In step S406, the electric field E is calculated.

  As described above, the circuit analysis and the FDTD method are directly coupled. Thereby, the coupling with the electromagnetic field can be analyzed considering only the input / output terminals of the circuit.

  Although the current source method formulated based on Ampere's law is shown here as a cooperative analysis method, the voltage source method, which is a method based on Faraday's law, may be used as the cooperative analysis method. An active element may be modeled using S parameters prepared in advance, and a black box model method incorporated into the FDTD method may be used.

(2.2 Model creation method of the present invention)
Here, an outline of the model creation method of the present invention will be described.

In circuit analysis, as a combination of a pair of terminals into which a circuit element is inserted, a combination of a circuit signal terminal and a ground terminal and a combination of a circuit signal terminal and a power supply terminal are given in advance in design data. Many. Further, when inserting a circuit in electromagnetic field analysis, the space between terminals after dividing the circuit board into meshes needs to be 1 mesh . For this reason, when the distance between terminals is 2 mesh or more, it is assumed that a conductor is generated from these terminals, the distance between terminals is set to 1 mesh , and a circuit element is inserted. However, there are a plurality of paths in which conductors are generated and terminals are connected in this way, and modeling is difficult.

Therefore, in the model creation method according to the present invention, in the electromagnetic field analysis model, a conductor surface corresponding to a reference potential terminal such as a ground terminal or a power supply terminal is generated and arranged by shifting by 1 mesh in a direction perpendicular to the circuit board. Create a model as As a result, the distance between the other terminal combined with the terminal of the reference potential on the circuit board and the conductor surface is 1 mesh , and the path connecting them is uniquely determined. A circuit element corresponding to the analysis method is inserted between the conductor surface corresponding to the reference potential terminal and the other terminal combined with the reference potential terminal to perform circuit analysis. For example, if the analysis method is the current source method, no element is inserted and only the current observation point is set. In the FDTD method, these connections are opened to perform electromagnetic field analysis.

  Hereinafter, a reference potential terminal such as a ground terminal or a power supply terminal is referred to as a “reference terminal”. Further, a terminal that is combined with a reference terminal and into which a circuit element is inserted at the time of circuit analysis is referred to as a “counter terminal”.

Here, the model creation method according to the present invention will be described using a specific example.
FIG. 5 is a diagram showing an example in which a conductor surface is generated for the two-dimensional electromagnetic field analysis model shown in FIG.

  In FIG. 5, the ground terminal GND is a reference terminal, and the terminals a, b, and c are counter terminals with respect to the ground terminal GND.

As shown in FIG. 5, in the circuit board 1 divided into meshes , the ground terminal GND and the terminals a, b, and c are separated by 2 meshes or more. Therefore, the conductor surface 3 corresponding to the ground terminal GND is generated and arranged so as to be shifted by 1 mesh in the vertical direction with respect to the circuit board 1. In FIG. 5, the conductor surface 3 is disposed on the circuit board 1, but may be disposed below. The conductor surface 3 includes terminals 50a, 50b, 50c, and 50d corresponding to the terminals on the circuit board 1. For example, the terminal 50a corresponds to the terminal a.

  Further, in order to determine the position corresponding to the ground terminal GND on the conductor surface 3, the ground terminal GND and the terminal 50d are connected by the conductor 52, and according to the analysis method between the terminal on the conductor surface and the terminal on the circuit board. Insert circuit elements. FIG. 5 shows an example in which circuit analysis is performed by the current source method by inserting the current sources 51a, 51b, and 51c.

  If the conductor surface is generated as shown in FIG. 5, it can be considered that the ground terminal GND, which is the reference terminal, and the terminals 50a, 50b, 50c, and 50d have the same potential. Therefore, performing circuit analysis by inserting a circuit element between a terminal on the conductor surface and a terminal on the circuit board corresponding to the terminal inserts a circuit element between the reference terminal and its counter terminal. This is equivalent to performing circuit analysis.

Further, since the distance between the conductor surface and the counter terminal is 1 mesh , the position where the circuit element is arranged can be uniquely determined.

Furthermore, another specific example is shown and demonstrated.
FIG. 6 is a diagram showing an example different from FIG. 5 in which conductor surfaces are generated for the two-dimensional electromagnetic field analysis model shown in FIG.

As shown in FIG. 6, first, the conductor surface 5 corresponding to the ground terminal GND is generated. The conductor surface 5 includes terminals 60a, 60b, 60c, and 60d corresponding to the terminals on the circuit board 1. And the conductor mesh which terminals other than the terminal 60d corresponding to a reference | standard terminal on the conductor surface 5 contact | connects from the conductor surface 5 is deleted. The conductor surface 7 generated in this way is arranged so as to be shifted by 1 mesh in the vertical direction with respect to the circuit board 1. Furthermore, in order to determine the position corresponding to the terminal on the circuit board on the conductor surface 7, the terminal on the circuit board and the terminal on the conductor surface corresponding to the terminal are connected by the conductors 62a, 62b, 62c, and 62d. Then, circuit elements corresponding to the analysis method are inserted between the terminals 60 a, 60 b, 60 c and the conductor surface 7. FIG. 6 shows an example in which circuit analysis is performed by a current source method with the current sources 61a, 61b, and 61c being inserted.

  Similar to the description of FIG. 5, if the conductor surface is generated in this way, it can be considered that the conductor surface has the same potential as the ground terminal GND, and the terminal on the conductor surface has the same potential as the corresponding terminal on the circuit board. Therefore, inserting a circuit element between the terminal on the conductor surface 5 and the conductor surface to perform circuit analysis means inserting a circuit element between the reference terminal and its counter terminal to perform circuit analysis. Is equivalent.

Further, since the distance between the conductor surface and the terminal on the conductor surface corresponding to the counter terminal (terminals 60a, 60b, 60c in FIG. 6) is 1 mesh , the position where the circuit element is arranged can be uniquely determined.

  The model creation method shown in FIG. 5 is effective when the number of reference terminals is two or less because the conductor surface corresponding to the reference terminal may be arranged above or below the circuit board. However, when there are three or more reference terminals, the conductor surface cannot be arranged.

On the other hand, the model creation method shown in FIG. 6 generates a conductor surface from which the conductor mesh with which a terminal on a conductor surface other than the terminal corresponding to the reference terminal is in contact is deleted as in the case where the conductor surface 7 is generated from the conductor surface 5. Therefore, the present invention can also be applied to a case where there are three or more reference terminals that need to generate a conductor surface.

(3. Implementation on computer 100)
The electromagnetic field circuit linkage analysis according to the above invention can be implemented as computer software by the following procedure.

The procedure is summarized below.
FIG. 7 is a flowchart specifically showing the flow of the cooperative analysis process shown in FIG.

  With reference to FIG. 7, the flow of the cooperative analysis process will be described. Steps S7100 to S7120 are processes according to the program 136 for executing FDTD, and steps S7200 to S7212 are processes according to the program 137 for executing circuit analysis.

  4B corresponds to steps S7100 to S7102, step S402 corresponds to steps S7104 to S7106, step S404 corresponds to steps S7200 to S7212, and step S406 corresponds to steps S7108 to S7120.

The flow of the electromagnetic field analysis process will be described.
First, the CPU 120 reads data necessary for analysis from the design data 134 and the analysis target model 135 stored in the hard disk 124 (step S7100). The data read here includes, for example, the size of the lattice mesh , the time step of FDTD analysis, the time step of circuit analysis, the analysis time, the electric field in the analysis region, the initial value of the magnetic field, the current of the circuit element, the initial value of the voltage, These are the dielectric, conductor coordinate values, circuit element netlist, and maximum analysis time Tmax arranged in the analysis region.

Further, the CPU 120 sets the analysis time t to zero, secures a storage area corresponding to the analysis area size and mesh size of the analysis condition in the memory 122, and analyzes the analysis area mesh coefficient based on the arranged conductor and dielectric information. Term calculation is performed (step S7101). The electric field and magnetic field values are set based on predetermined electric field and magnetic field initial values. At this time, a circuit model is created by the method described in (2.2). Details will be described later.

Subsequently, the CPU 120 calculates and updates the total magnetic field H of the analysis region mesh (step S7102). The magnetic field has been updated in step S7102 based on, CPU 120 is a mesh including a circuit element (hereinafter referred to as circuit mesh) into a current value I by the following formula ampere magnetic field H in the vicinity of (5) (step S7104).

  Here, the CPU 120 uses the current value I as a current source value to be added to the netlist for circuit analysis.

  The CPU 120 gives the current source value of step S7104 to the circuit analysis (step S7106). The process flow of the circuit analysis that has received the current source value will be described later.

  In step S7108, the CPU 120 advances the current analysis time t by half of the FDTD time step, and calculates and updates the total electric field E in the analysis region (step S7110).

  Next, the CPU 120 receives a voltage calculated by circuit analysis (step S7112). If it has not been calculated yet, the process is suspended until it is calculated.

In step S7114, the CPU 120 converts the voltage value received from the circuit analysis into an electric field value of the circuit mesh by the following equation (6).

Δy is the length of the FDTD mesh in the Y direction. Although the circuit elements are arranged in the Y direction here, they can be arranged in any direction.

  Then, the CPU 120 sets the voltage value obtained in step S7114 as the electric field value at the place where the circuit element in the electromagnetic field analysis region is inserted (step S7116).

  In step S7118, CPU 120 advances the current analysis time t by half of the time step of FDTD. Further, the electric field in the analysis area at the analysis time t is stored in the electric field value storage area 138 in the hard disk 124, and the magnetic field information is stored in the magnetic field value storage area 139 in the hard disk 124.

  In step S7120, CPU 120 compares current analysis time t with maximum analysis time Tmax. If analysis time t is smaller than maximum analysis time Tmax (No in step S120), the process returns to step S7102. Otherwise (Yes in step S7120), the storage area of the memory 122 used for analysis is released, and the calculation is terminated.

Next, the flow of circuit analysis processing will be described.
First, the CPU 120 sets the analysis time to zero. Then, a storage area is secured in the memory 122 based on a predetermined net list, and a circuit matrix in which a current source and a capacitor are added by a current source method based on element connection information is generated (step S7200).

  In step S7202, CPU 120 receives the current source value from the electromagnetic field analysis. The process is suspended until the current source value is received.

  Next, the CPU 120 updates the current source value to the current source value received in step S7202 (step S7204), and performs circuit analysis from the analysis time Δt (n−1 / 2) to Δt (n + 1/2). The voltage is obtained (step S7206).

  Furthermore, CPU 120 gives the voltage value at time Δt (n + 1/2) to the electromagnetic field analysis (step S7208). However, when the object of circuit analysis is mutual inductance, a voltage difference value is given. In addition, the CPU 120 stores the current and voltage values at time Δt (n + 1/2) in the hard disk 124.

  In step S7210, CPU 120 advances current analysis time t by a circuit analysis time step, and stores the voltage or voltage difference between analysis time t and circuit element terminals in hard disk 124.

  Then, CPU 120 compares current analysis time t with maximum analysis time Tmax (step S7212). If analysis time t is smaller than maximum analysis time Tmax (No in step S7212), the process returns to step S7202. If not (Yes in step S7212), the storage area of the memory 122 used for analysis is released and the calculation is terminated.

  As described above, in the present invention, the electromagnetic field circuit linkage analysis using the model creation method described in (2.2) is performed.

  In the above description, the analysis process has been described as being completed on the condition that the maximum analysis time has been exceeded. However, as an analysis process termination condition, other conditions such as an electric field and a magnetic field are in a steady state. It is also possible to use whether or not a condition that a predetermined time has elapsed since the time is satisfied.

  Further, as described above, the electromagnetic field analysis and the circuit analysis are performed by the CPU 120 according to the program 136 for executing the FDTD and the program 137 for executing the circuit analysis, but are executed by a plurality of CPUs connected via the communication interface 128. The result may be exchanged via the computer 100. The electromagnetic field analysis and the circuit analysis may be analyzed using a single CPU, but the analysis area may be divided into a plurality of areas and analyzed using a plurality of CPUs.

Next, the circuit model creation process performed in step S7200 will be described.
FIG. 8 is a flowchart showing the flow of model creation processing.

A model creation method will be described with reference to FIG.
First, in step S800, the CPU 120 reads data necessary for analysis from the design data 134 and the analysis target model 135, and performs various settings. Specifically, the mesh size used for electromagnetic field analysis from the design data 134, or the position where the shape coordinates indicating the area where the circuit element to be analyzed exists and the circuit terminal exist in the CAD data coordinate system. Read the terminal coordinates indicating. Also, analysis type information (current source method, voltage source method, black box method, etc.) of the analysis target circuit is acquired from the analysis target model 135, and settings are made according to each analysis method.

  Next, in step S802, the CPU 120 divides the shape of the circuit board into meshes using the mesh size given as the analysis condition. When dividing into meshes, since the mesh size is finite, the centers of all terminals may not necessarily exist at the mesh vertices. In such a case, as an example of determining the terminal mesh coordinates, the mesh vertex coordinates closest to the terminal coordinates may be used as the terminal mesh coordinates.

In step S804, CPU 120 selects a terminal for generating a conductor surface. Here, based on the design data 134, a terminal used as a reference terminal may be selected, or a reference terminal that is separated from the counter terminal by 2 meshes or more by mesh division in step S802 may be selected. By generating a conductor surface corresponding to the reference terminal, the conductor surface can be handled as a reference potential surface.

Subsequently, in step S806, the CPU 120 generates the conductor surface as described in (2.2) above, and the terminal selected in step S804 is assumed to be shifted by one mesh in the direction perpendicular to the circuit board. The conductor is extended by one mesh in the direction perpendicular to the circuit board from the conductor surface. Thereby, the selected terminal and the conductor surface are connected. Depending on the number of selected terminals, what kind of conductor surface is generated may be set in advance. Further, the reference terminal corresponding to the generated conductor surface is connected by a conductor. When a conductor surface such as the conductor surface 7 shown in FIG. 6 is generated, it is assumed that the conductor is extended by one mesh in the vertical direction from the terminal on the circuit board to the side where the conductor surface is disposed.

  Finally, in step S808, the CPU 120 connects the terminals by inserting circuit elements according to the analysis type between the terminals.

  A circuit model is created by the above operation. In the present embodiment, modeling by the current source method is dealt with, but the circuit analysis method that requires another pair of terminals such as a black box method can be handled similarly. Further, the flow of the cooperative processing of electromagnetic field analysis and circuit analysis by the current source method is as described in (2.1).

As described above, according to the present invention, a circuit model necessary for electromagnetic field analysis can be uniquely created from design data. Thereby, the circuit model creation time can be shortened. Therefore, electromagnetic field circuit linkage analysis can be performed efficiently.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a conceptual diagram which shows an example of the computer 100 which performs the electromagnetic field circuit cooperation analysis program using the model creation method of this invention. It is a figure which shows the structure of the computer 100 in a block diagram format. 3 is a functional block diagram showing a functional configuration of a CPU 120. FIG. It is a schematic diagram of the cooperative analysis by the current source method. It is a figure which shows the example which produced | generated the conductor surface with respect to the two-dimensional electromagnetic field analysis model shown to FIG. 9 (A). It is a figure which shows the example different from FIG. 5 which produced | generated the conductor surface with respect to the two-dimensional electromagnetic field analysis model shown to FIG. 9 (A). FIG. 5 is a flowchart specifically illustrating a flow of a cooperative analysis process illustrated in FIG. It is the flowchart which showed the flow of the model creation process. It is a figure which shows the example of the model by a current source method.

  DESCRIPTION OF SYMBOLS 1 Circuit board, 3, 7 Conductor surface, 30 Model preparation part, 32 Electromagnetic field circuit cooperation analysis execution part, 42, 92 Current source, 44 Capacitor, 46 Circuit network, 100 Computer, 102 Computer main body, 104 Display, 106 FD drive , 108 optical disk drive, 110 keyboard, 112 mouse, 116 FD, 118 CD-ROM, 120 CPU, 122 memory, 124 hard disk, 128 communication interface, 134 design data, 135 analysis target model, 136 program for executing FDTD, 137 circuit Program for executing analysis, 138 electric field value storage area, 139 magnetic field value storage area.

Claims (6)

A circuit model creation program for causing a computer having an arithmetic processing unit to execute a creation process of a circuit model used when performing electromagnetic circuit cooperation analysis on a circuit board,
The arithmetic processing unit mesh-dividing the circuit board;
The arithmetic processing unit generates a conductor surface corresponding to a predetermined terminal that becomes a reference potential when performing circuit analysis, and then arranges the conductor surface so as to be shifted by 1 mesh in a direction perpendicular to the circuit board. Identifying a position on the conductor surface corresponding to the predetermined terminal;
The arithmetic processing unit specifies a position where a circuit element required for a predetermined circuit analysis is arranged according to an analysis method between the conductor surface and a terminal to be analyzed combined with the predetermined terminal. And performing steps,
A circuit model creation program in which a distance between terminals for arranging the circuit elements is 1 mesh. The circuit model creation program according to claim 1, wherein in the step of specifying a position on the conductor surface, the arithmetic processing unit generates a conductor surface including a terminal corresponding to a terminal on the circuit board. The step of specifying a position on the conductor surface generates a conductor surface in which the arithmetic processing unit corresponds to a terminal other than the predetermined terminal on the circuit board and from which the mesh including the terminal is deleted. The circuit model creation program according to claim 1. Dividing the circuit board into meshes,
The arithmetic processing unit calculates mesh coordinates from the mesh-divided circuit board; and
2. The circuit model creation according to claim 1, wherein the arithmetic processing unit includes a step of calculating the mesh coordinates of the terminals from the spatial coordinates of each vertex of the mesh and the spatial coordinates of a plurality of terminals on the circuit board. program. A computer-readable recording medium storing the circuit model creation program according to claim 1. A circuit model creation apparatus for executing a circuit model creation process used when performing electromagnetic circuit cooperation analysis on a circuit board,
A storage device for storing data representing a three-dimensional shape of the circuit board;
An arithmetic processing unit for executing the circuit model creation process,
The arithmetic processing unit includes:
Means for dividing the circuit board into meshes;
A conductor surface corresponding to a predetermined terminal that becomes a reference potential when performing circuit analysis is generated, and the conductor surface is arranged by shifting by 1 mesh in the direction perpendicular to the circuit board, and corresponds to the predetermined terminal. Means for identifying a position on the conductor surface;
Means for specifying a position where a circuit element required for a predetermined circuit analysis is arranged according to an analysis method between the conductor surface and a terminal to be analyzed combined with the predetermined terminal. ,
The circuit model creation device, wherein a distance between terminals for arranging the circuit elements is 1 mesh.

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