JP2019096240A - Electromagnetic wave analysis system for structures, electromagnetic wave analysis method for structures, and electromagnetic wave analysis program for structures - Google Patents

Abstract

To make it possible that when electromagnetic waves are made incident on a surface of a structure which is made up of a conductor, scattered electromagnetic waves irradiated from the surface of the structure are calculated with better precision.SOLUTION: An electromagnetic wave analysis system for structures according to the embodiment includes: a reflection wave calculation unit which makes electromagnetic waves, considered to be a plurality of light beams, incident on a model simulating a two- or three-dimensional structure made up of a conductor and executes a simulation for calculating reflection electromagnetic waves reflected on a surface of the structure on the basis of a law of reflection to calculate the electromagnetic waves reflected on the surface of the structure; and a radiation wave calculation unit which calculates an electromagnetic flow induced in a surface layer of the structure by electromagnetic waves reflected on the surface of the structure and calculates scattered electromagnetic waves irradiated from the surface of the structure by the electromagnetic flow in the surface layer of the structure.SELECTED DRAWING: Figure 5

Description

  Embodiments of the present invention relate to an electromagnetic wave analysis system for a structure, an electromagnetic wave analysis method for a structure, and an electromagnetic wave analysis program for a structure.

  The SBR (Shooting and Bouncing Rays) method is known as one of the propagation analysis methods of electromagnetic waves in a high frequency band (see, for example, Patent Document 1). The SBR method is also called a ray-shooting method, and is an analysis method that approximates an incident electromagnetic wave to a collection of a plurality of light rays and calculates a reflected wave of the electromagnetic wave on the object surface based on the law of reflection. In addition, in order to improve the analysis accuracy in the SBR method, a technique has also been proposed that analyzes not only reflected waves of electromagnetic waves on the object surface but also transmitted waves transmitted through the object surface (for example, see Non-Patent Document 1) .

  On the other hand, as a method of approximately analyzing scattered electromagnetic waves generated when electromagnetic waves are incident on a conductor, the Physical Optics (PO) method and the Physical Theory of Diffraction (PTD) method are known. (See, for example, Non-Patent Document 2 and Non-Patent Document 3).

  The PO method and the PTD method are analysis methods for approximately determining an electromagnetic current induced by an electromagnetic wave incident on a conductor and for determining a scattered electromagnetic wave by radiation integration. The PO method is an analysis method for obtaining scattered electromagnetic waves by approximating that the electromagnetic current induced in the conductor is uniform, and the PTD method uses the electromagnetic current induced in the conductor as the nonuniform electromagnetic current to be scattered electromagnetic waves. Is an analysis method to obtain

  Also, calculation of a radiation integral for obtaining a scattered electromagnetic wave based on an electromagnetic current induced in a conductor, which is performed in the PO method and the PTD method, is conventionally known (see, for example, Non-Patent Document 4).

Japanese Patent Laid-Open No. 2002-232348

Daisuke Hosoda, "Inside-outside electromagnetic wave propagation analysis by SBR method", Chuo University Master's thesis summary (FY2012), [Nov. 9, 2017 search], Internet <URL: http: //ir.c.chuo-u. ac.jp/repository/search/binary/p/5156/s/2558/> Antenna Engineering Handbook, Editor The Institute of Electronics, Information and Communication Engineers, Publisher: Takeo Osamu, Publishing Office Ohmsha A. Michaele, "Elimination of infinities in equivalent edge currents, part I: Fringe current components", IEEE Transactions on Antennas and Propagation, VOL. AP-34, NO.7, JULY 1986 C. Balanis, "Advanced engineering electromagnetics"

  An object of the present invention is to make it possible to calculate scattered electromagnetic waves emitted from the surface of a structure when the electromagnetic wave is incident on the surface of a structure formed of a conductor with better accuracy.

  The electromagnetic wave analysis system for a structure according to an embodiment of the present invention treats electromagnetic waves as a plurality of light beams on a model simulating a structure consisting of a two-dimensional or three-dimensional conductor, and enters the structure based on the law of reflection. A reflected wave calculation unit for calculating an electromagnetic wave reflected on the surface of the structure by executing simulation to calculate an electromagnetic wave reflected on the surface of the body, and the structure induced by the electromagnetic wave reflected on the surface of the structure And a radiation wave calculation unit for calculating the electromagnetic flow in the surface layer of and calculating the scattered electromagnetic wave emitted from the surface of the structure by the electromagnetic flow in the surface layer of the structure.

  The electromagnetic wave analysis method of the structure according to the embodiment of the present invention is based on the law of reflection, considering electromagnetic waves as a plurality of light rays and entering the model simulating a structure formed of a two-dimensional or three-dimensional conductor. Calculating an electromagnetic wave reflected on the surface of the structure by performing simulation to calculate an electromagnetic wave reflected on the surface of the structure; and of the structure induced by the electromagnetic wave reflected on the surface of the structure Calculating an electromagnetic flow in the surface layer, and calculating a scattered electromagnetic wave emitted from the surface of the structure by the electromagnetic flow in the surface layer of the structure.

  Further, the electromagnetic wave analysis program of a structure according to the embodiment of the present invention causes a computer to consider electromagnetic waves as a plurality of light beams and enter the model simulating a structure consisting of a two-dimensional or three-dimensional conductor, and the law of reflection. Calculating an electromagnetic wave reflected on the surface of the structure by performing a simulation to calculate an electromagnetic wave reflected on the surface of the structure based on the step of calculating electromagnetic waves reflected on the surface of the structure; The steps of calculating the electromagnetic flow in the surface layer of the structure and calculating the scattered electromagnetic wave emitted from the surface of the structure by the electromagnetic flow in the surface layer of the structure are performed.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram of the electromagnetic wave analysis system of the structure which concerns on the 1st Embodiment of this invention. The figure which shows the analysis model used as the object of the electromagnetic wave analysis simulation performed by the electromagnetic wave analysis system shown in FIG. 1, and the 1st example of incident electromagnetic waves. The figure which shows the analysis model used as the object of the electromagnetic wave analysis simulation performed by the electromagnetic wave analysis system shown in FIG. 1, and the 2nd example of incident electromagnetic waves. The figure which shows the analysis model used as the object of electromagnetic wave analysis simulation performed by the electromagnetic wave analysis system shown in FIG. 1, and the 3rd example of incident electromagnetic waves. The flowchart which shows the flow of a scattered electromagnetic wave analysis of the structure by the electromagnetic wave analysis system shown in FIG. The figure which shows the example of a shape of the analysis model used as the object of electromagnetic wave analysis by the electromagnetic wave analysis system of the structure which concerns on the 2nd Embodiment of this invention. The figure explaining the mechanism which a calculation error produces in electromagnetic wave analysis which made the analysis model which has a shape shown in FIG. 6 object.

  An electromagnetic wave analysis system for a structure, an electromagnetic wave analysis method for a structure, and an electromagnetic wave analysis program for a structure according to an embodiment of the present invention will be described with reference to the attached drawings.

First Embodiment
(Structure and function of electromagnetic wave analysis system of structure)
FIG. 1 is a configuration diagram of an electromagnetic wave analysis system of a structure according to a first embodiment of the present invention.

  The electromagnetic wave analysis system 1 of a structure is a system that analyzes a scattered electromagnetic wave emitted from the surface of a structure when the electromagnetic wave is incident on a structure formed of a two-dimensional or three-dimensional conductor. Examples of the conductor include materials containing carbon as well as metals, such as carbon fiber reinforced plastic (CFRP). In addition, a structure in which a paint containing a radio wave absorber is applied to the surface of a conductor or a structure in which a sheet-like wave absorber is attached to the surface of a conductor may be an analysis target. As the radio wave absorber, various materials are known, such as a mixture of metal such as iron, nickel or ferrite or a powder of carbon with a resin, a woven fabric of conductive fibers, and the like.

  The scattered electromagnetic waves emitted from the surface of the structure can be calculated by electromagnetic wave analysis simulation using an analysis model simulating a two-dimensional or three-dimensional structure. Examples of structures to be analyzed for scattered electromagnetic waves include structures constituting an aircraft or a car. Specific examples of the structure constituting the aircraft include an intake duct of the aircraft, a casing to which the access panel is to be attached, a casing for accommodating the legs, a control seat and the like.

  The electromagnetic wave analysis system 1 causes the arithmetic device 2 of the computer 5 to be read by causing the arithmetic device 2 of the computer 5 which is an electronic circuit provided with the arithmetic device 2, the input device 3 and the display 4 to read the electromagnetic wave analysis program of the structure. , The modeling unit 6, the reflected wave calculation unit 7, and the radiation wave calculation unit 8. An electromagnetic wave analysis program of a structure that causes the arithmetic unit 2 of the computer 5 to function as the modeling unit 6, the reflected wave calculation unit 7, and the radiation wave calculation unit 8 is stored in an information recording medium and provided to the user as a program product. You can also.

  The modeling unit 6 has a function of creating an analysis model that simulates a two-dimensional or three-dimensional structure. The graphic information necessary to create an analysis model can be input from the input device 3 to the modeling unit 6.

  The reflected wave calculation unit 7 has a function of calculating an electromagnetic wave reflected on the surface of the structure by electromagnetic wave analysis simulation by the SBR method for an analysis model of the structure created by the modeling unit 6. More specifically, the reflected wave calculation unit 7 regards the electromagnetic wave as a collection of a plurality of light rays and sequentially makes the light rays incident on an analysis model simulating a two-dimensional or three-dimensional structure, and a structure based on the law of reflection. It has the function of performing a simulation that calculates the electromagnetic waves reflected on the surface of the body. The intensity and phase of the electric field and magnetic field reflected on the surface of the structure can be determined by the electromagnetic wave analysis simulation of the SBR method.

  FIG. 2 is a diagram showing an analysis model to be subjected to an electromagnetic wave analysis simulation performed by the electromagnetic wave analysis system 1 shown in FIG. 1 and a first example of incident electromagnetic waves, and FIG. 3 is a diagram showing the electromagnetic wave analysis system 1 shown in FIG. FIG. 4 is a diagram showing an analysis model as a target of electromagnetic wave analysis simulation to be executed and a second example of an incident electromagnetic wave; FIG. 4 is an analysis model as a target of electromagnetic wave analysis simulation performed by the electromagnetic wave analysis system 1 shown in FIG. It is a figure which shows the 3rd example of incident electromagnetic waves.

  Not only the shape of the analysis model 20 but also the characteristics including the intensity, the incident position and the direction of the incident electromagnetic wave to be incident on the analysis model 20 can be arbitrarily determined in the reflected wave calculation unit 7. For example, an analysis having a desired shape as a bundle of a plurality of light beams L, which is an electromagnetic wave traveling radially in a 360 degree direction or a specific angle range from a certain incident point (SP: shooting point) designated as illustrated in FIG. It can be incident on the model 20. Alternatively, as illustrated in FIG. 3, an electromagnetic wave traveling in one direction as a uniform plane wave having a width may be made to enter an analysis model 20 having a desired shape. When plane waves are made to be incident, a plurality of plane waves may be made to be incident on an analysis model 20 having a desired shape at different angles as illustrated in FIG. 4. That is, the plane wave may be made to enter in the direction of 360 degrees or in a plurality of angular directions in a specific range.

  The analysis model 20 may be defined as an area surrounded by a three-dimensional closed surface simulating the surface of the structure, or as an area surrounded by a two-dimensional closed line simulating the surface of the structure It may be defined. When the analysis model 20 is a three-dimensional model, the analysis model 20 is represented by coordinate data representing a three-dimensional space position. When the analysis model 20 is a two-dimensional model, a two-dimensional position is The analysis model 20 is expressed by the coordinate data that represents it.

  The input of the electromagnetic wave analysis by the SBR method is not only the shape of the analysis model 20 described above and the characteristics of the incident electromagnetic wave, but also the reflectance for the electromagnetic wave of the analysis model 20. When the structure is a conductor, the electromagnetic wave does not pass through the surface of the structure, so that the reflectance can be set to 1. On the other hand, when the structure in which the conductor is covered with the radio wave absorber is the analysis target, the reflectance can be set to a value smaller than 1 according to the characteristics of the radio wave absorber.

  The calculation of the electromagnetic wave analysis by the SBR method is performed based on the distance from the incident point SP corresponding to the position of the incident electromagnetic wave to the surface of the analysis model 20 and the angle between the surface of the analysis model 20 and each light ray L representing the incident electromagnetic wave. The position of the reflection point of each ray L reflected on the surface of the model 20, the reflection direction of each ray L, and the intensity and phase of the ray L reflected at each reflection point are calculated. Then, the intensity and phase of the electromagnetic wave at each position on the surface of the analysis model 20 are obtained by adding all the light rays L passing through the unit area surrounding each position on the surface of the analysis model 20 to be calculated for the electromagnetic wave. Can.

  For example, in the case where an electromagnetic wave is incident as a spherical wave radially from a certain incident point SP designated as illustrated in FIG. 2, the incident direction of the light beam L is changed by a step angle Δθ1 By adding all the rays L passing through the unit area including each position, the intensity and the phase of the reflected wave reflected by the surface of the analysis model 20 can be calculated.

  Similarly, in the case of entering a plane wave as illustrated in FIG. 3, all the points passing through the unit area including each position on the surface of the analysis model 20 are changed by changing the incident point SP of the light beam L by the step width ΔD1. The intensity and phase of the reflected wave reflected on the surface of the analysis model 20 can be calculated by adding the light rays L of

  In addition, in the case of entering a plurality of plane waves as illustrated in FIG. 4, the incident point SP of the light beam L is changed by the dividing width ΔD2 and the incident direction of the light beam L is changed by the dividing angle Δθ2 to unit area By adding all the electromagnetic waves that pass through, it is possible to calculate the intensity and phase of the electromagnetic waves at each position to be calculated.

  Therefore, when the reflected wave of the electromagnetic wave on the surface of the structure is calculated by the SBR method using the analysis model 20, integral calculation is performed with the contour of the analysis model 20 as a range. That is, if the analysis model 20 is a two-dimensional plane model, a two-dimensional electromagnetic wave along the periphery of the analysis model 20 can be calculated by line integration with the closed contour of the analysis model 20 as the integration range. On the other hand, if the analysis model 20 is a three-dimensional three-dimensional model, it is possible to calculate a three-dimensional electromagnetic wave along the periphery of the analysis model 20 by the area component with the closed contour surface of the analysis model 20 as the integration range.

  The radiation wave calculation unit 8 calculates the electromagnetic flow in the surface layer of the structure induced by the electromagnetic wave reflected on the surface of the structure, calculated by SBR analysis by the reflected wave calculation unit 7, in the surface layer of the structure It has a function to calculate the scattered electromagnetic waves emitted from the surface of the structure by the electromagnetic current. The scattered electromagnetic waves obtained as calculation results can also be represented by the intensity and phase of the electromagnetic waves at each position in the region to be analyzed.

  As an analysis method to calculate the electromagnetic current induced on the surface of the structure based on the electromagnetic wave irradiated to the surface of the structure and further calculate the scattered electromagnetic wave emitted by the electromagnetic current induced on the surface of the structure , PO method and PTD method are known.

The PO method is an analysis method for obtaining scattered electromagnetic waves by approximating that the electromagnetic current induced on the surface of the structure is uniform. The uniform electromagnetic current in the PO method is called PO current ^IPO . As shown in FIG. 2 to FIG. 4, in the PO method, the position viewed from the incident position of the electromagnetic wave and the position to be a shadow are specified on the surface S of the analysis model 20. Then, assuming that each position of the surface S seen from the incident position of the electromagnetic wave is the irradiation position Si of the electromagnetic wave, an approximation is made that uniform PO current I ^PO is induced in an infinitely wide plane in contact with the surface S at each irradiation position Si. It will be. In this case, the intensity of the PO current ^{I PO} is defined by the equation (1) using the unit normal vector n_Vector surface S of the incident magnetic field Hi and the analytical model 20 of the respective irradiation positions Si when there is no analytical model 20 be able to.
I ^PO = 2n_Vector × Hi (1)

On the other hand, at the non-irradiation position Ss which is a shadow when viewed from the incident position of the electromagnetic wave in the surface S of the analysis model 20, it is assumed that the induced magnetic current M ^PO is zero as shown in the equation (2) .
M ^PO = 0 (2)

Therefore, each reflection point of the electromagnetic wave determined by the SBR method corresponds to the irradiation position Si of the electromagnetic wave in the PO method, and the PO current I ^PO can be determined based on the intensity of the electromagnetic wave reflected at the reflection point of the analysis model 20 it can. That is, the non-irradiation position Ss which is a shadow on the surface S of the analysis model 20 and the irradiation position Si of the electromagnetic wave can be distinguished by the SBR method, and the analysis result of the electromagnetic wave in the SBR method can be input in the PO method.

Once the PO current I ^PO induced on the surface S of the analytical model 20 is determined, the scattered electromagnetic wave emitted from the surface S of the analytical model 20 can be calculated by the radiation integral of the PO current I ^{PO according} to the equivalent principle. That is, the electric and magnetic fields can be calculated from the induced current and magnetic current. Note that the radiation integral for calculating the scattered electromagnetic wave from the conductor-induced electromagnetic current is described, for example, on pages 282 to 287 of C. Balanis, "Advanced engineering electromagnetics", which is Non-Patent Document 4 mentioned above. It can carry out by calculation shown by Formula (6-107), Formula (6-108), Formula (6-110), and Formula (6-111).

On the other hand, the PTD method is an analysis method in which an object to which an electromagnetic current is induced is regarded as a flat plate having an edge (edge) to obtain an uneven electromagnetic current, and a scattered electromagnetic wave is determined in consideration of the uneven electromagnetic current. . Thus, when employing the PO method, the electromagnetic current at the surface of the structure is calculated as a uniform PO current I ^PO whereas when employing the PTD method, the electromagnetic current at the surface of the structure is employed. The flow is calculated as non-uniform electromagnetic flow.

The PTD method is an analysis method that improves the PO method, and is an analysis method that obtains an analysis result by adding a current resulting from the presence of an edge to the PO current I ^PO in the PO method. The non-uniform current induced at the edge portion is called FW (Fringe Wave) current ^If . The FW current I ^f may be calculated, for example, using the equations (24) and (25) of A. Michaeli, “Elimination of infinities in equivalent edge currents, part I: Fringe current components” described in Non-Patent Document 3 described above. Can. When the PTD method, the PO current ^{I PO,} by performing the radiation integral by adding a FW current ^{I f,} scattered electromagnetic wave is calculated.

  Furthermore, in the PTD method, an analysis method capable of calculating a longitudinal wave (creeping wave) propagating along the surface of an object has also been proposed. For this reason, if analysis by the PTD method is adopted, it is possible to obtain analysis results of scattered electromagnetic waves with high accuracy. On the contrary, if PO method is adopted, analytical calculation can be simplified.

  Thus, the analysis processing of the scattered electromagnetic wave in the PO method or the PTD method is also an integral calculation for obtaining the scattered electromagnetic wave emitted by the electromagnetic wave incident on the surface of the analysis model 20. That is, if the analysis model 20 is a two-dimensional plane model, calculate a two-dimensional scattered electromagnetic wave emitted from the surface of the analysis model 20 by line integration with the closed contour of the analysis model 20 as the integration range. Can. On the other hand, if the analysis model 20 is a three-dimensional three-dimensional model, calculate a three-dimensional scattered electromagnetic wave emitted from the surface of the analysis model 20 by an area fraction with the closed contour surface of the analysis model 20 as the integration range. Can.

  The analysis result in the radiation wave calculation unit 8 can be displayed on the display 4. The analysis result displayed on the display 4 may be map image data representing the distribution of the scattered electromagnetic waves, or may be image data represented as a numerical value. Alternatively, the distribution of the electromagnetic wave obtained by combining the reflected wave and the scattered electromagnetic wave on the surface of the structure may be displayed on the display 4.

(Method of electromagnetic wave analysis of structure)
Next, an electromagnetic wave analysis method of a structure by the electromagnetic wave analysis system 1 will be described.

  FIG. 5 is a flow chart showing a flow of scattered electromagnetic wave analysis of a structure by the electromagnetic wave analysis system 1 shown in FIG.

  First, in step S1, the electromagnetic waves reflected on the surface of the structure are calculated by the SBR method. That is, for example, an electromagnetic wave is sequentially incident as a plurality of light beams L on an analysis model 20 simulating a structure as illustrated in FIGS. 2 to 4 to obtain the intensity and phase of a reflected wave on the surface of the analysis model 20 Analysis is performed in the reflected wave calculation unit 7. The distribution of the intensity and phase of the reflected wave on the surface of the analysis model 20 obtained as the SBR analysis result is given from the reflected wave calculation unit 7 to the radiation wave calculation unit 8.

Next, in step S2, a scattered electromagnetic wave emitted from the surface of the structure is calculated by the PO method or PTD method using the electromagnetic wave reflected by the surface of the structure as input data. For that purpose, an electromagnetic flow in the surface layer of the analysis model 20 induced by the electromagnetic wave reflected on the surface of the analysis model 20 is determined in the radiation wave calculation unit 8. In the case of the PO method, PO current I ^PO can be obtained as a uniform flow. On the other hand, if PTD method, electromagnetic current obtained by adding the FW current ^{I f} the PO current ^{I PO} as a non-uniform flow is obtained.

  Subsequently, the scattered electromagnetic waves emitted from the surface of the analysis model 20 by the electromagnetic flow in the surface layer of the analysis model 20 are determined in the radiation wave calculation unit 8. Thereby, the scattered electromagnetic waves radiated from the surface of the structure can be calculated as an analysis result.

  Next, in step S3, generation and display of an analysis result image are performed in the radiation wave calculation unit 8. For example, in the case of displaying the intensity distribution or phase distribution of the scattered electromagnetic wave emitted from the surface of the structure as a two-dimensional map, two-dimensional map image data is generated and output to the display 4. Alternatively, a two-dimensional map representing the intensity and phase of the electromagnetic wave obtained by adding the scattered electromagnetic wave emitted from the surface of the structure and the electromagnetic wave reflected by the surface of the structure may be generated and displayed.

  Next, in step S4, the evaluation of the structure based on the analysis result including the scattered electromagnetic wave from the structure surface is performed. If the scattered electromagnetic wave is known, it is possible to grasp whether the electromagnetic wave is likely to be reflected or not easily reflected on the surface of the structure.

  Therefore, as a specific example, it is possible to evaluate the stealth of a structure that constitutes an aircraft based on the intensity of the scattered electromagnetic wave. For example, it is possible to set a threshold value corresponding to a stealth design request, and to determine that the structure satisfies the required stealth property if the intensity of the scattered electromagnetic wave is below the threshold value or below the threshold value.

  The determination of stealth may be performed by the user visually observing the analysis image data displayed on the display 4 or may be automated. When the evaluation of stealth property is to be automated, the radiation wave calculation unit 8 can be provided with a function of performing threshold processing on the intensity of the scattered electromagnetic wave, and the display 4 can display the evaluation result of the stealth property.

(effect)
The electromagnetic wave analysis system 1 of the structure as described above and the electromagnetic wave analysis method of the structure use the electromagnetic wave irradiated on the surface of the structure obtained by the electromagnetic wave analysis by the SBR method as the input of the electromagnetic wave analysis by the PO method or the PTD method. Thus, the scattered electromagnetic wave emitted from the structure is determined.

  For this reason, according to the electromagnetic wave analysis system 1 of the structure and the electromagnetic wave analysis method of the structure, the scattered electromagnetic wave from the structure can be obtained with high accuracy by a simple process. That is, since the reflection of the electromagnetic wave on the surface of the structure is calculated by the SBR method, the advantage of the SBR method can be used while the calculation can be dramatically simplified as compared with the case of obtaining the exact solution of the reflected wave from the structure. The scattered electromagnetic waves emitted from the surface of the structure can be determined with sufficient accuracy.

  In particular, if the scattered electromagnetic wave emitted from the structure is determined by the PTD method, the scattered electromagnetic wave considering diffraction at the edge of the structure can be determined.

Second Embodiment
(Electromagnetic wave analysis system and electromagnetic wave analysis method of structure)
FIG. 6 is a view showing an example of the shape of an analysis model to be an object of electromagnetic wave analysis by the electromagnetic wave analysis system of a structure according to the second embodiment of the present invention.

  In the electromagnetic wave analysis system 1 of the structure in the second embodiment, the integration range is determined so that the calculation error is reduced when the structure to be analyzed of the scattered electromagnetic wave has a cavity that is open at at least one location. The point is different from the electromagnetic wave analysis system 1 of the structure in the first embodiment. The other configuration and function of the electromagnetic wave analysis system 1 of the structure in the second embodiment are not substantially different from the electromagnetic wave analysis system 1 of the structure in the first embodiment, so a structure having a cavity is simulated. Only the analysis model 20 is illustrated, and illustration and description of the same configuration or the corresponding configuration are omitted.

  When the structure has at least one open cavity such as a blind hole, a recess, a groove or a through hole, the analysis model 20 simulating the structure is also opened at at least one place as shown in FIG. The cavity 21 is simulated. When the analysis model 20 has a cavity 21, the electromagnetic wave reflected on the surface of the structure is calculated by the SBR method calculation including the integration along the contour 22 including the cavity 21 of the analysis model 20 while the cavity 21 is opened. It is an error to calculate the electromagnetic current induced in the surface layer of the structure and the scattered electromagnetic waves emitted from the surface of the structure by calculation by the PO method or PTD method including integration along the contour 23 obtained by closing the portion 21A. May lead to a reduction in

  In particular, as illustrated in FIG. 6, the electromagnetic wave incident on the analysis model 20 is, as in the case of a through hole whose one end is closed and the other end is open, as well as a through hole whose both ends are open, When the simulation is performed under the condition of reflection more than times, the integration range in the SBR analysis is a line or a plane along the contour 22 of the analysis model 20, while the integration range in the PO analysis or the PTD analysis is the cavity of the analysis model 20. By making lines or faces along the contour 23 obtained by closing the open portions 21A of 21, the effect of reducing the error in the analysis result becomes remarkable.

  FIG. 7 is a view for explaining a mechanism in which a calculation error occurs in electromagnetic wave analysis for an analysis model having the shape shown in FIG.

  When the light beam L in SBR analysis is made to enter into the cavity 21 of the analysis model 20 as shown in FIGS. 6 and 7, the light beam L reflected by the surface in the cavity 21 is again reflected by another surface in the cavity 21. There is. That is, depending on the shape of the analysis model 20, the light ray L is multi-reflected to the analysis model 20.

  6 and 7 show an example in which the light ray L is reflected at three reflection points R1, R2 and R3 in the cavity 21. FIG. The reflection points R 1, R 2, R 3 of the light ray L are calculated by SBR analysis in which a line or plane along the contour 22 including the cavity 21 of the analysis model 20 is an integral range.

On the other hand, in the PO method and PTD method, assuming that a line or plane along the contour 22 including the cavity 21 is an integral range, the light beam L reflected at the reflection points R1, R2 and R3 also induces the PO current I ^PO etc. Become. That is, when the light ray L is reflected twice or more at a plurality of reflection points R 1, R 2 and R 3, the light ray L reflected at each reflection point R 1, R 2 and R 3 is a part of incident electromagnetic waves in PO method and PTD method. Become.

  However, since the PO method and the PTD method are analysis methods that approximate the induced electromagnetic current, an error occurs between the PO method and the actually generated electromagnetic current. In particular, as shown in FIG. 7, at the second and subsequent reflection points R2 and R3, an error specific to multiple reflection occurs in the electromagnetic flow, as in the case where the pseudo-transmission wave L 'which does not actually exist is generated.

  That is, since the light ray L reflected at the first reflection point R1 is reflected again at the next reflection point R2, the light ray L going from the first reflection point R1 to the next reflection point R2 is actually blocked. However, in the PO method and the PTD method, calculation of the scattered electromagnetic wave is performed on the assumption that the ray L is not sufficiently blocked at the reflection point R2 and the pseudo transmitted wave L 'transmitted through the reflection point R2 is present. Similarly, also at the reflection point R3, calculation of the scattered electromagnetic wave is performed on the assumption that the light ray L is not sufficiently blocked and the pseudo-transmission wave L 'transmitted through the reflection point R3 is present. This is calculated by the SBR method, not by the PO method or PTD method based on the light beam L reflected at the reflection points R1 and R2 immediately before the second and subsequent reflection points R2 and R3. It is for.

  Therefore, when multiple reflection of the light beam L occurs in the cavity 21, the radiation integral in the PO method and the PTD method as illustrated in FIG. 6 so that an error due to the pseudo transmitted wave L 'does not occur in the scattered electromagnetic wave. The integration range can be a line or a surface along the contour 23 obtained by closing the open portions 21A of the cavity 21. That is, when the scattered electromagnetic wave analysis by the PO method or PTD method is performed on the analysis model 20 having both the cavity 21 and the convex surface 24, the integration range is set to the surface of the analysis model 20 in the convex surface 24 other than the cavity 21. On the other hand, in the cavity 21 forming the through hole or the concave surface, it is preferable to use a line or a surface that closes the opening portion 21A.

  Then, since the electromagnetic current induced in the PO method or PTD method is calculated in the integration line or the integration plane that blocks the opening portion 21A, the electromagnetic current due to the pseudo-transmission wave L 'resulting from the multiple reflection of the light beam L is calculated. Can be avoided. That is, the error of the scattered electromagnetic wave due to the generation of the pseudo transmission wave L 'can be reduced.

  In the second embodiment described above, in the scattered electromagnetic wave analysis combining SBR method and PO method or PTD method, when the structure and the analysis model 20 have the cavity 21, the range of integration by the PO method or PTD method is The cavity 21 of the analysis model 20 is closed and set to a line or surface along the contour 23 obtained.

(effect)
Therefore, according to the second embodiment, in the scattered electromagnetic wave analysis combining SBR method and PO method or PTD method, even when a structure having a cavity such as an intake duct of an aircraft is targeted, Calculation errors can be reduced.

  Specifically, in the case where the incident electromagnetic wave is multi-reflected in the cavity of the structure having a complicated shape, it can be avoided that the pseudo transmitted wave in the cavity of the structure is calculated. That is, in analysis calculation combining the SBR method and the PO method or the PTD method, it is possible to simulate that the electromagnetic waves that are multi-reflected are shielded by the structure. As a result, highly accurate electromagnetic wave analysis can be performed in consideration of the influence of the reflected wave being blocked by the structure.

  On the other hand, in the calculation of the SBR method, the calculation accuracy of the reflected wave on the surface of the structure can be maintained. Moreover, the advantage of the SBR method of high calculation speed can be maintained.

(Other embodiments)
Although the specific embodiments have been described above, the described embodiments are merely examples and do not limit the scope of the invention. The novel methods and apparatus described herein may be embodied in various other ways. Also, various omissions, substitutions and changes in the form of the methods and apparatus described herein may be made without departing from the spirit of the invention. The appended claims and their equivalents are intended to cover such different forms and modifications as fall within the scope and spirit of the invention.

DESCRIPTION OF SYMBOLS 1 electromagnetic wave analysis system 2 arithmetic unit 3 input device 4 display 5 computer 6 modeling unit 7 reflected wave calculation unit 8 radiation wave calculation unit 20 analysis model 21 cavity 21A opening part 22, 23 outline 24 convex L light L 'pseudo transmitted wave n_Vector Unit normal vector R1, R2, R3 Reflection point S Surface of analysis model Si Irradiation position of electromagnetic wave Ss Non-irradiation position of electromagnetic wave

Claims (11)

Carrying out a simulation in which electromagnetic waves are regarded as a plurality of light beams and incident on a model simulating a structure consisting of a two-dimensional or three-dimensional conductor, and electromagnetic waves reflected on the surface of the structure are calculated based on the law of reflection. A reflected wave calculation unit that calculates an electromagnetic wave reflected on the surface of the structure by
Calculate the electromagnetic flow in the surface layer of the structure induced by the electromagnetic wave reflected on the surface of the structure, and calculate the scattered electromagnetic wave emitted from the surface of the structure by the electromagnetic flow in the surface layer of the structure An electromagnetic wave analysis system for a structure having a radiation wave calculation unit.   The reflection wave calculation unit calculates the structure including a integral along a contour including the cavity of the model for a model simulating a two-dimensional or three-dimensional structure having a cavity having at least one opening. The electromagnetic wave in the surface layer of the structure and the structure by calculation including the integration along the contour obtained by closing the opening portion of the cavity while calculating the electromagnetic wave reflected on the surface of An electromagnetic wave analysis system for a structure according to claim 1, wherein the electromagnetic wave analysis system for a structure according to claim 1, wherein the electromagnetic wave analysis system is configured to calculate a scattered electromagnetic wave emitted from the surface of.   The electromagnetic wave analysis system of a structure according to claim 1 or 2, wherein the radiation wave calculation unit is configured to calculate an electromagnetic flow in a surface layer of the structure as a uniform electromagnetic flow.   The electromagnetic wave analysis system of a structure according to claim 1 or 2, wherein the radiation wave calculation unit is configured to calculate an electromagnetic flow in a surface layer of the structure as an uneven electromagnetic flow.   The electromagnetic wave analysis system for a structure according to claim 2, wherein the reflected wave calculation unit is configured to execute the simulation under a condition in which the electromagnetic wave incident on the model is reflected twice or more inside the cavity.   The reflected wave calculation unit is configured to calculate an electromagnetic wave reflected on the surface of a structure that constitutes an aircraft or a car, while the radiation wave calculation unit corresponds to that of the structure that constitutes the aircraft or the car An electromagnetic wave analysis system for a structure according to any of the preceding claims, configured to calculate scattered electromagnetic waves emitted by electromagnetic flow in the surface layer.   The reflected wave calculation unit is configured to calculate an electromagnetic wave reflected on the surface of the casing to which the intake duct or access panel of the aircraft is to be attached, while the radiation wave calculation unit includes the intake duct or the casing An electromagnetic wave analysis system for a structure according to any of the preceding claims, which is arranged to calculate the scattered electromagnetic waves emitted by the electromagnetic current in the surface layer of the.   The electromagnetic wave analysis method of a structure which calculates the scattered electromagnetic waves radiated | emitted from the surface of the said structure by the electromagnetic wave analysis system of the structure of any one of Claims 1 thru | or 7. Carrying out a simulation in which electromagnetic waves are regarded as a plurality of light beams and incident on a model simulating a structure consisting of a two-dimensional or three-dimensional conductor, and electromagnetic waves reflected on the surface of the structure are calculated based on the law of reflection. Calculating the electromagnetic wave reflected on the surface of the structure by
Calculate the electromagnetic flow in the surface layer of the structure induced by the electromagnetic wave reflected on the surface of the structure, and calculate the scattered electromagnetic wave emitted from the surface of the structure by the electromagnetic flow in the surface layer of the structure An electromagnetic wave analysis method of a structure having a step.   The electromagnetic wave analysis method of a structure according to claim 8 or 9, wherein the stealth property of the structure constituting the aircraft is evaluated based on the scattered electromagnetic wave emitted from the surface of the structure. On the computer
Carrying out a simulation in which electromagnetic waves are regarded as a plurality of light beams and incident on a model simulating a structure consisting of a two-dimensional or three-dimensional conductor, and electromagnetic waves reflected on the surface of the structure are calculated based on the law of reflection. Calculating an electromagnetic wave reflected on the surface of the structure by calculating the electromagnetic flow in the surface layer of the structure induced by the electromagnetic wave reflected on the surface of the structure, and calculating the electromagnetic wave in the surface layer of the structure Calculating the scattered electromagnetic wave emitted from the surface of the structure by the flow;
Program of electromagnetic wave analysis of the structure to execute.

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