JP2019100772A - Estimation program, estimation device and estimation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To streamline estimation by near-field far-field transformation.
An estimation device measures position data indicating a measurement position at which a reflected wave corresponding to a radio wave emitted to an object is measured, and measurement value data indicating a measurement result of a reflected wave at the measurement position. Get 14 and. The estimation device 10 is specified with respect to the distance 15 calculated between the object 21 and the measurement position 22 using the position data 13 and an error generated according to the division method of the area including the object 21. Based on the tolerance error 16, the division size 17 of the plurality of division areas divided from the area including the object 21 is determined. The estimation device 10 uses the determined division size 17 and the measurement value data 14 to determine the reflection cross-sectional area 18 corresponding to the object 21 when the reflected wave is measured at a position farther from the object 21 than the measurement position 22. Or estimate the intensity 19 of the reflected wave.
[Selected figure] Figure 1

Description

  The present invention relates to an estimation program, an estimation device and an estimation method.

  There is a radar system which irradiates a radio wave (a radar wave) from a radar to a moving object such as an airplane or a ship and detects a reflected wave from the moving object to measure the position of the moving object. In designing a moving object or a radar system, it may be desired to measure a radar reflection cross section (RCS: Radar Cross-Section) indicating the radio wave reflection performance of the moving object. The actual RCS of the measurement object that can be the target of the radar wave irradiation is calculated by measuring the reflected waves to the radar wave at a plurality of positions around the measurement object in a laboratory such as an anechoic chamber.

  However, in the definition of RCS, it is preferable to measure the reflected wave at a position sufficiently far from the measurement object to directly determine RCS, but depending on the size of the measurement object, a position sufficiently away from the measurement object It may not be practical to measure the reflected wave at Therefore, near-field far-field transformation has been proposed in which the measurement result of the reflected wave in the vicinity of the measurement object is analyzed to estimate a desired RCS. In near-field far-field transformation, the distance between each scattering point on the measurement object on which the radar wave scatters and the measurement antenna measuring the reflected wave is approximated by the distance between the representative position on the measurement object and the measurement antenna An approximation of the Green's function is performed by

  The approximation error of the Green's function amplitude approximation reduces the estimation accuracy of RCS. Therefore, as a method of reducing the approximation error of the Green function, a target division method has been proposed in which the region of the measurement object is divided into a plurality of divided regions and the distance between the scattering point and the measurement antenna is approximated for each divided region. . A near-field far-field transformation method has been proposed in which region segmentation is performed on a three-dimensional model to estimate RCS. Also, a near-field far-field transformation method has been proposed in which region segmentation is performed on a two-dimensional model to estimate RCS.

Georg Schnattinger, Raimund AM Mauermayer and Thomas F. Eibert, "Monostatic Radar Cross Section Near-Field Far-Field Transformations by Multilevel Plane-Wave Decomposition", IEEE Transactions on Antennas and Propagation, Vol. 62, No. 8, pp. 4259 -4268, August 2014. Shuntaro Omi, Toru Uno, Takuji Arima, Takao Fujii and Yujiro Kushiyama, "Near-Field Far-Field Transformation Utilizing 2-D Plane-Wave Expansion for Monostatic RCS Extrapolation", IEEE Antennas and Wireless Propagation Letters, Vol. 15, pp. 1971-1974, March 2016. Jiming Song and Weng Cho Chew, "Error Analysis for Multipole Expansion of Vector Green's Functions", IEEE Microwave and Wireless Components Letters, Vol. 11, No. 7, pp 311-313, July 2001.

  However, in the conventional near-field to far-field conversion, it has been unclear what size (division size) should be used to divide the area of the measurement object. Therefore, there is a risk that the computational load will be excessive due to the division size being too small, and a risk that the estimation accuracy may become poor due to the division size being too large, making near-field far-field transformation inefficient. There is a problem that there is.

  In one aspect, the present invention aims to provide an estimation program, an estimation apparatus and an estimation method that can make near field far field transformation estimation efficient.

  In one aspect, an estimation program that causes a computer to perform the following processing is provided. Position data indicating the measurement position at which the reflected wave corresponding to the radio wave irradiated to the object is measured and measurement value data indicating the measurement result of the reflected wave at the measurement position are acquired. The object is determined based on the distance calculated between the object and the measurement position using the position data and the tolerance specified for the error that occurs according to the division method of the area containing the object. The division size of the plurality of divided areas divided from the area to be included is determined. Using the determined division size and measurement value data, the intensity of the reflection cross section or the reflection wave corresponding to the object when the reflection wave is measured at a position farther from the object than the measurement position is estimated.

  In one aspect, an estimation device is provided that has a storage unit and a processing unit. Also, in one aspect, a computer implemented estimation method is provided.

  In one aspect, near field far field transformation estimation is streamlined.

It is a figure explaining an estimating device of a 1st embodiment. It is a figure showing the example of the information processing system of a 2nd embodiment. It is a block diagram showing the example of hardware of RCS measuring device. It is a figure which shows the example of a model of near-field far-field transformation by the target division method. It is a block diagram which shows the function example of RCS measuring device. It is a figure which shows the example of a parameter table. It is a figure which shows the example of a measured value table. It is a figure which shows the example of a measurement position table. It is a figure which shows the example of a position matching table. It is a figure which shows the example of a polarization angle table. It is a figure which shows the example of an angle matching table. It is a figure which shows the example of a directivity table. It is a figure which shows the example of a distant RCS table. It is a flowchart which shows the example of a procedure of 1st near-field far-field transformation. It is a flowchart which shows the example of a procedure of 2nd near-field far-field transformation. It is a figure which shows the example of a ship model. It is a figure which shows the example of the difference | error table with respect to a ship model. It is a graph which shows the 1st RCS calculation example of a ship model. It is a graph which shows the 2nd RCS calculation example of a ship model. It is a graph which shows the 3rd RCS calculation example of a ship model. It is a figure which shows the example of a random plate model. It is a figure which shows the example of the difference | error table with respect to a random plate model. It is a graph which shows the 1st RCS calculation example of a random plate model. It is a graph which shows the 2nd RCS calculation example of a random plate model. It is a graph which shows the 3rd RCS calculation example of a random plate model.

Hereinafter, the present embodiment will be described with reference to the drawings.
First Embodiment
The first embodiment will be described.

FIG. 1 is a diagram for explaining an estimation apparatus according to the first embodiment.
The estimation apparatus 10 of the first embodiment analyzes the measurement result of the reflected wave in the vicinity of the object, and estimates the reflection cross section of the object by near-field far-field transformation. As the estimation device 10, an information processing device such as a client computer operated by a user or a server computer accessed by the client computer can be used.

  The estimation device 10 includes a storage unit 11 and a processing unit 12. The storage unit 11 may be a volatile semiconductor memory such as a random access memory (RAM) or a non-volatile storage such as a hard disk drive (HDD) or a flash memory. The processing unit 12 is, for example, a processor such as a central processing unit (CPU) or a digital signal processor (DSP). However, the processing unit 12 may include an electronic circuit for a specific application such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA). The processor executes a program stored in a memory (may be the storage unit 11) such as a RAM. The program includes an estimation program. A set of multiple processors may be referred to as a "multiprocessor" or simply a "processor."

  The storage unit 11 stores position data 13 and measured value data 14. The position data 13 indicates the measurement position 22 at which the reflected wave corresponding to the radio wave emitted to the object 21 is measured. The measurement value data 14 indicates the measurement result of the reflected wave at the measurement position 22. The object 21 is an object such as an airplane or a ship whose reflection cross section is to be calculated. The measured value data 14 includes, for example, the received voltage measured when the reflected wave is received at the measurement position 22. For example, the object 21 and the measurement position 22 are provided in the same anechoic chamber, and the reflected wave is measured in the anechoic chamber. The anechoic chamber may be a relatively small room with respect to the size of the object 21, and the measurement position 22 may be closer to the object 21 than when the reflection cross section is directly calculated. The position data 13 may indicate a plurality of different measurement positions, and the measurement value data 14 may indicate a plurality of measurement results corresponding to the plurality of measurement positions.

  The processing unit 12 uses the position data 13 to calculate the distance 15 defined between the object 21 and the measurement position 22. In addition, the processing unit 12 acquires the tolerance 16 specified for the error generated according to the division method of the area including the object 21. Then, the processing unit 12 determines the division size 17 of the plurality of divided areas divided from the area including the object 21 based on the calculated distance 15 and the specified tolerance error 16.

  The division size 17 is, for example, the radius of each divided area obtained by dividing the area including the object 21. The error is, for example, an approximation process that approximates the distance between the scattering point where the radiated radio wave is scattered and the measurement position 22 by the distance between the representative position in the divided area to which the scattering point belongs and the measurement position 22. It is an error that occurs. The representative position of a certain divided area is, for example, the center position of the divided area. The above approximation error occurs, for example, in the amplitude approximation of the Green's function. The error depends on the division size 17. For example, the larger the division size 17, the larger the error, and the smaller the division size 17, the smaller the error.

  The tolerance 16 may be a value input to the estimation device 10 by the user, or may be a predetermined value set in advance. The tolerance 16 is preferably about 10%. As the distance 15 for determining the division size 17, the minimum distance between the object 21 and the measurement position 22 may be used. Further, as the distance 15 for determining the division size 17, the minimum distance among the distances between the representative position of each division area and the measurement position 22 may be used. However, in the latter case, if the division size 17 is changed, the division method of the area including the object 21 is changed, and the distance 15 is also changed. Therefore, the preferable division size 17 is determined by trial and error.

  In the determination of the division size 17, for example, correspondence information indicating the correspondence between the division size, the error, and the distance is referred to. Using this correspondence information, the division size 17 corresponding to the calculated distance 15 and the specified tolerance error 16 can be selected. The division size 17 is preferably the largest division size among the division sizes such that an error that may occur under the distance 15 is less than or equal to a tolerance of 16. The larger the division size 17 is, the lower the calculation load on the subsequent, and the smaller the division size 17 is, the higher the calculation load on the following.

  The processing unit 12 estimates the reflection cross-sectional area 18 (sometimes referred to as radar reflection cross-sectional area or RCS) using the determined division size 17 and the measurement value data 14. The reflection cross section 18 is a far reflection cross section obtained when the reflected wave is measured at a position farther from the object 21 than the measurement position 22. The processing unit 12 outputs estimated data indicating the estimated reflection cross section 18. The processing unit 12 may display visualization data obtained by visualizing the reflection cross-sectional area 18 on a display.

  Further, the processing unit 12 estimates the intensity 19 of the reflected wave obtained when the measurement is performed at a position farther from the object 21 than the measurement position 22 instead of or in combination with the reflection cross section 18. . The intensity 19 can be calculated, for example, from the reflection cross section 18 as follows.

The reflected power density (reflected wave intensity) when the receiving antenna is installed at a distance R from the center of the object 21 is: reflected power density = transmission power × transmission antenna gain × reflection cross section / (4πR ² ) ² Is calculated. The reception power of this reception antenna is calculated as: reception power = reflected power density × reception antenna gain × wavelength ² / (4π). From these two equations, reception power = transmission power × transmission antenna gain × reception antenna gain × wavelength ² × reflection cross section / ((4π) ³ × R ⁴ ) is calculated. Thus, when the reflection cross-sectional area 18 is calculated, the intensity 19 of the reflected wave at an arbitrary measurement position can be calculated. However, the above is an example of a method of estimating the intensity 19, and the intensity 19 may be estimated by another method.

  According to the estimation apparatus 10 of the first embodiment, when the reflected wave is measured at a position farther from the object 21 than the measurement position 22 from the measured value data 14 indicating the measurement result of the reflected wave at the measurement position 22 The reflection cross section 18 or the intensity 19 of the reflected wave is estimated. Thus, the analysis of the reflection performance of the object 21 can be efficiently performed. Further, the estimation accuracy can be improved by dividing the area including the object 21 into a plurality of divided areas and performing the estimation process.

  Also, from the distance 15 defined between the object 21 and the measuring position 22 and the specified tolerance 16 a preferred division size 17 is determined. As a result, the reflection performance can be estimated more efficiently than when the user sets the division size 17 based on experience and intuition. For example, there is a risk that the estimation accuracy of the reflection cross section 18 or the intensity 19 is significantly reduced due to the division size 17 being too large, or the calculation load required for the estimation of the reflection cross section 18 or the intensity 19 is too large Reduce the risk of Therefore, it is possible to efficiently calculate the reflection cross-sectional area 18 and the intensity 19 with high accuracy.

Second Embodiment
Next, a second embodiment will be described.
FIG. 2 is a diagram illustrating an example of the information processing system according to the second embodiment.

  The information processing system according to the second embodiment measures the reflected wave to the radar wave in the vicinity of the measurement object using a compact radio anechoic chamber, analyzes the measurement result, and determines the distant radar reflection cross section (far RCS) Estimate The information processing system according to the second embodiment includes an anechoic chamber 20, an object to be measured 30, an RCS measuring apparatus 100, and a measuring antenna 111.

  The anechoic chamber 20 is a shield space designed to block electromagnetic waves from the outside and prevent electromagnetic waves generated inside from being reflected by walls. The anechoic chamber 20 may be referred to as an anechoic chamber. The object to be measured 30 is placed inside the anechoic chamber 20. The measurement object 30 is a scatterer that reflects a radar wave, and is an object to measure a distant RCS such as an airplane or a ship. A relatively large object is assumed as the measurement object 30. The RCS measurement apparatus 100 is an information processing apparatus that acquires the measurement result of the reflected wave measured in the vicinity of the measurement object 30, and estimates the far RCS by near-field far-field transformation. The measurement antenna 111 is connected to the RCS measurement apparatus 100.

  In the second embodiment, a monostatic radar in which a transmitting antenna for transmitting a radar wave and a receiving antenna for receiving a reflected wave are arranged at the same position is used. The measurement antenna 111 may use a single antenna as a transmission antenna and a reception antenna, or may separately have a transmission antenna and a reception antenna arranged sufficiently close to each other.

  While changing the position of the measurement antenna 111 with respect to the measurement object 30, the radar wave is transmitted to measure the reflected wave, and the measurement results of the reflected wave at a plurality of measurement positions are obtained. Preferably, the measurement antenna 111 is disposed at a position separated by a predetermined distance from the center of the measurement object 30, and the measurement positions are changed so that a plurality of measurement positions form a circle. In order to realize this, the measurement antenna 111 may be moved so as to go around the measurement object 30 every time the reflected wave is measured, or the measurement object 30 is placed on a rotation table and the measurement object 30 is rotated. You may

  When the measurement object 30 is large, it is difficult to sufficiently separate the measurement antenna 111 from the measurement object 30 in the anechoic chamber 20, and it is difficult to directly measure the far RCS. For this reason, the RCS measuring apparatus 100 estimates the far RCS by near-field far-field transformation from the measurement result of the reflected wave in the vicinity of the measurement object 30. Note that the information processing apparatus that collects the measurement results of the reflected wave from the measurement antenna 111 and the information processing apparatus that estimates the distant RCS may be different information processing apparatuses, and the RCS measurement apparatus is disposed outside the radio anechoic chamber 20. It may be done.

FIG. 3 is a block diagram showing an example of hardware of the RCS measurement apparatus.
The RCS measurement apparatus 100 includes a CPU 101, a RAM 102, an HDD 103, an image signal processing unit 104, an input signal processing unit 105, a medium reader 106, and communication interfaces 107 and 108. The above units are connected to the bus.

  The CPU 101 is a processor including an arithmetic circuit that executes program instructions. The CPU 101 loads at least a part of a program or data stored in the HDD 103 into the RAM 102 and executes the program. The CPU 101 may include a plurality of processor cores, the RCS measurement apparatus 100 may include a plurality of processors, and the following processing may be performed in parallel using a plurality of processors or processor cores. Also, a set of multiple processors may be referred to as a "multiprocessor" or simply a "processor."

  The RAM 102 is a volatile semiconductor memory that temporarily stores programs executed by the CPU 101 and data used by the CPU 101 for computations. The RCS measurement apparatus 100 may include a memory of a type other than the RAM, or may include a plurality of memories.

  The HDD 103 is a non-volatile storage device that stores software programs such as an operating system (OS) and application software, and data. The RCS measurement apparatus 100 may include another type of storage device such as a flash memory or a solid state drive (SSD), and may include a plurality of non-volatile storage devices.

  The image signal processing unit 104 outputs an image to the display 112 connected to the RCS measurement apparatus 100 according to an instruction from the CPU 101. As the display 112, any type of display such as a cathode ray tube (CRT) display, a liquid crystal display (LCD), or an organic electro-luminescence (OEL) display can be used.

  The input signal processing unit 105 acquires an input signal from the input device 113 connected to the RCS measurement apparatus 100, and outputs the input signal to the CPU 101. As the input device 113, a mouse, a touch panel, a pointing device such as a touch pad or a track ball, a keyboard, a remote controller, a button switch, or the like can be used. In addition, a plurality of types of input devices may be connected to the RCS measurement apparatus 100.

  The media reader 106 is a reading device that reads programs and data recorded on the recording medium 114. As the recording medium 114, for example, a magnetic disk, an optical disk, a magneto-optical disk (MO: Magneto-Optical disk), a semiconductor memory or the like can be used. The magnetic disk includes a flexible disk (FD: Flexible Disk) and an HDD. The optical disc includes a CD (Compact Disc) and a DVD (Digital Versatile Disc).

  The medium reader 106 copies, for example, a program or data read from the recording medium 114 to another recording medium such as the RAM 102 or the HDD 103. The read program is executed by the CPU 101, for example. The recording medium 114 may be a portable recording medium, and may be used for distribution of programs and data. Also, the recording medium 114 and the HDD 103 may be referred to as computer readable recording medium.

  The communication interface 107 is connected to the measurement antenna 111. The communication interface 107 causes the measurement antenna 111 to transmit a radar wave in accordance with an instruction from the CPU 101. Further, the communication interface 107 acquires the reception voltage of the reflected wave from the measurement antenna 111. The measurement antenna 111 has a predetermined directivity.

  The communication interface 108 is an interface that is connected to the network 115 and that communicates with other information processing apparatuses via the network 115. The communication interface 108 may be a wired communication interface connected to a wired communication device such as a switch via a cable or may be a wireless communication interface connected to a base station via a wireless link.

Next, the near-field far-field transformation will be described.
FIG. 4 is a diagram showing a model example of near-field far-field transformation by the target division method.
The RCS measurement apparatus 100 logically divides the measurement object 30 into a plurality of divided areas. As will be described later, when the measurement object 30 is divided into a plurality of divided regions, the amplitude approximation error of the Green function becomes smaller and the conversion error of the near-field far-field conversion becomes smaller than when not divided.

  In the second embodiment, in order to simplify the description, the height of the measurement object 30 is ignored and two-dimensional near-field far-field transformation is adopted. In addition, it is assumed that the measurement object 30 has a long and thin shape, and a plurality of divided areas are one-dimensionally aligned on a straight line. FIG. 4 shows the measurement object 30 viewed from directly above. The xy plane formed by the x and y axes corresponds to the horizontal plane, and the z axis corresponds to the direction perpendicular to the horizontal plane.

  The two-dimensional near-field far-field transformation is also described, for example, in the above-mentioned Non-Patent Document 2. In the second embodiment, an example of two-dimensional near-field far-field transformation will be described. However, three-dimensional near-field far-field transformation can also be employed. The three-dimensional near-field far-field transformation is described in, for example, Non-Patent Document 1 above. Further, in the second embodiment, although an example of a long and thin measurement object in which a plurality of divided areas are arranged on a straight line is used, a large measurement object having a width in which a plurality of divided areas are arranged planarly It is also possible to apply the near-field far-field transformation of the second embodiment. In that case, the rectangular region in which the measurement object is accommodated may be divided in the x-axis direction and the y-axis direction, and the following calculation may be performed only for the division region in which the measurement object exists.

  Since the measurement object 30 has a long thin shape, it has a length in the longitudinal direction as a representative dimension D. The longitudinal direction of the measurement object 30 is along the x-axis, and the center of the measurement object 30 is the origin of the xy plane. Here, the measurement target 30 is logically divided into divided regions 31 to 36, with the division number M = 6. The divided areas 31 to 36 are arranged on the x axis.

The measurement object 30 is divided by the division size a. The divided areas 31 to 36 are circles of radius a. For the p-th divided area among the divided areas 31 to 36, the central position r _p is defined as a representative position representing the divided area. The center position r _p is the center of the circle.

On the other hand, the position of the measurement antenna 111 in the xy plane is the antenna position r. The antenna position r forms an angle φ _a with the x axis in the xy plane. The radar wave that has reached the p-th divided region from the measurement antenna 111 is scattered at the scattering point r ^* . However, as described later, it considers the center position r _p and the scattering point r ^*, is to approximate the distance between the antenna position r and the scattering point r ^* in distance between the antenna position r and the center position r _p.

The radar wave that has reached the scattering point r ^* is scattered in various directions to form a reflected wave. The scattering angle β _q is an angle that the q-th reflection direction makes with the x axis in the xy plane. Radar waves scattered in various directions affect the received voltage measured at antenna position r.

The near-field far-field transformation is mathematically defined using the above model.
By approximating the distance between the antenna position r and the scattering point r ^{* by} the distance between the antenna position r and the center position r _p , the amplitude approximation of the Green's function is performed as shown in Formula (1). In equation (1), k is the wave number and k = 2π / λ (λ is the wavelength). The transformation integral equation of equation (2) is generated by using equation (1) and plane wave expansion. In equation (2), U _R (r) is the received voltage measured at antenna position r, C is a constant calculated from k etc., W _R (β) is the directivity of the receiving antenna, W _T (β) is It is the directivity of the transmitting antenna. S (β) is a distant RCS, which is an unknown variable to be obtained by near-field far-field transformation.

T _N is a transfer function and is defined as equation (3). In equation (3), H _n ⁽²⁾ is the second Hankel function. N is a truncation parameter of series expansion, and can be determined from the division size a, for example, as in equation (4). In equation (4), α is a constant set in consideration of accuracy. If the diameter 2a of the split region is sufficiently small relative to the wavelength λ, the second term has a large influence on the truncation parameter N. However, in near-field far-field transformation, the diameter 2a is not sufficiently small relative to the wavelength λ, so the influence of the second term is small and the first term becomes dominant. Therefore, it can be regarded as N = 2 ka.

Equation (2) involves summing the values for various scattering angles β weighted by the transfer function T _N. In calculating the far RCS, the scattering angle β may not be a continuous value but a discrete value. The integration step of the scattering angle β is determined as, for example, 2π / 4N. Equation (2) also includes summing the values for the plurality of divided areas. From equation (2), one linear equation including a plurality of unknown variables S (β) with respect to β ₁ , β ₂ , β ₃ ,... Is generated for one antenna position r. Simultaneous linear equations are generated for a plurality of antenna positions. By solving this simultaneous linear equation, it is possible to derive the far RCS for each scattering angle β.

As described above, the distance between the antenna position r and the scattering point r ^* is approximated by the distance between the antenna position r and the center position r _p by the amplitude approximation of the Green function. As the division size a is smaller, the scattering point r ^* and the center position r _p are closer, so the amplitude approximation error of the Green function is smaller. This reduces the conversion error of the near-field far-field conversion. On the other hand, the smaller the division size a, the larger the division area, and the larger the size of the equation (2), the larger the amount of calculation. If the division size a is set based on the user's experience and intuition, there is a possibility that the near-field far-field transformation becomes inefficient. Therefore, the RCS measurement apparatus 100 automatically determines an appropriate division size a.

The relationship between the tolerance error x of the amplitude approximation of the Green function and the division size a will be described.
If both sides of equation (1) are divided by the left side of equation (1), equation (5) is obtained. Formula (6) is derived from the condition that the maximum value on the right side of Formula (5) is suppressed to 1 + x or less. Here, the scattering point r ^* at which the distance from the antenna position r is the largest among the circles of the radius a is a point on the circumference on the opposite side of the antenna position r with respect to the central position r _p . Therefore, the maximum value of the distance between the antenna position r and the scattering point r ^* is a value obtained by adding the division size a to the distance between the antenna position r and the center position r _p , and the left side of equation (6) is given by equation (7) Transformed into Formula (8) is derived from Formula (6) and Formula (7). Equation (9) is derived by modifying Equation (8). Equation (9) shows the relationship between the division size a, the tolerance error x of the amplitude approximation of the Green function, and the distance between the center position r _{p of the} division area closest to the antenna position r and the antenna position r .

  If the division size a satisfies Expression (9), the amplitude approximation error of the Green function can be suppressed to the tolerance error x or less. However, the smaller the division size a, the larger the amount of calculation of the near-field / far-field transformation. Therefore, it is preferable to make the division size a as large as possible within the range satisfying the equation (9). As described later, the preferred tolerance x of the Green function's amplitude approximation is x = 0.1 (10%). If x = 0.1 is set, equation (10) is used.

Since the division area changes when the division size a is changed, the central position r _p of each division area also changes. That is, the central position r _p of equation (9) depends on the division size a. As will be described later, in the second embodiment, two kinds of algorithms of the first method and the second method are illustrated as a method of determining the division size a which satisfies the equation (9).

Next, the function of the RCS measurement apparatus 100 will be described.
FIG. 5 is a block diagram showing an example of the function of the RCS measurement apparatus.
The RCS measurement apparatus 100 includes a measurement data storage unit 121, a near-field far-field conversion unit 122, an area division unit 123, an RCS data storage unit 124, and an RCS display unit 125. The measurement data storage unit 121 and the RCS data storage unit 124 are mounted using, for example, the RAM 102 or the HDD 103. The near-field / far-field transformation unit 122, the area division unit 123, and the RCS display unit 125 are implemented using, for example, a program executed by the CPU 101.

  The measurement data storage unit 121 stores measurement data indicating the measurement result of the reflected wave using the measurement antenna 111. The measurement data includes data of the received voltage acquired from the measurement antenna 111. In addition, the measurement data includes measurement conditions such as the antenna position and antenna angle (polarization angle) of the measurement antenna 111, the directivity of the measurement antenna 111, shape data of the measurement object 30, and the frequency of the radar wave used. included.

  The near-field to far-field conversion unit 122 analyzes the measurement data stored in the measurement data storage unit 121, performs near-field to far-field conversion based on Expressions (1) to (4), and it is difficult to measure directly. Estimate RCS. Specifically, the near-field to far-field transformation unit 122 defines unknown variables indicating the far RCS of each scattering angle β, generates simultaneous linear equations including the unknown variables, and solves the simultaneous linear equations. Calculate the estimated value of RCS.

  When the near-field / far-field transformation unit 122 performs near-field / far-field transformation, the area division unit 123 determines a division size a for logically dividing the measurement object 30. Specifically, the region division unit 123 determines a preferable division size a according to Expression (9) from the shape of the measurement object 30, the antenna position r of the measurement antenna 111, and the specified tolerance error x. The tolerance error x may be explicitly specified by the user of the RCS measurement apparatus 100, or a preferable value such as x = 0.1 may be set as a default value.

The RCS data storage unit 124 stores RCS data indicating the estimated value of the distant RCS of each scattering angle β calculated by the near-field / far-field conversion unit 122.
The RCS display unit 125 outputs the RCS data stored in the RCS data storage unit 124. For example, the RCS display unit 125 visualizes the RCS data to generate a graph indicating the relationship between the scattering angle β and the far RCS, and causes the display 112 to display the generated graph. Also, for example, the RCS display unit 125 causes the display 112 to display a list indicating the relationship between the scattering angle β and the far RCS. The RCS measurement apparatus 100 may output the processed data obtained by processing RCS data or RCS data to another output device such as a printer or may write the processed data to an external storage device. Also, the RCS measurement apparatus 100 may transmit RCS data or processing data to another information processing apparatus via the network 115.

FIG. 6 is a diagram showing an example of the parameter table.
The parameter table 131 is stored in the measurement data storage unit 121. The parameter table 131 stores pairs of parameter names and values for each parameter. Parameters include frequency and representative dimensions. The frequency is the frequency of the radar wave transmitted by the measurement antenna 111. The wavelength λ can be calculated from the frequency. The representative dimension is an example of shape data representing the shape of the measurement object 30, and is a length representative of the measurement object 30. Since the measurement object 30 of the second embodiment has a long and thin shape, the representative dimension is the length in the longitudinal direction.

FIG. 7 is a diagram showing an example of the measurement value table.
The measurement value table 132 is stored in the measurement data storage unit 121. The measurement value table 132 includes items of measurement number, received voltage real part, and received voltage imaginary part. The measurement number identifies the measurement of the received voltage. One received voltage is represented by a complex number including a real part and an imaginary part. The reception voltage recorded in the measurement value table 132 is normalized by the transmission voltage.

Here, as an example, the measurement antenna 111 makes one turn around the measurement target 30 while shifting the angle φ _a at 0.5 degree intervals. Therefore, the antenna positions r exist in 360 degrees3600.5 = 720. Also, for one antenna position r, the measurement antenna 111 measures the reception voltage of the reception polarization of x, y, z. Thus, three received voltages are measured for one antenna position r. Therefore, in the measurement value table 132, 720 ways × 3 directions = 2160 received voltages are recorded.

  The measurement numbers 1 to 720 indicate the reception voltage of the reception polarization x measured at 720 antenna positions r. The measurement numbers 721 to 1440 indicate the reception voltage of the reception polarization y measured at 720 antenna positions r. Measurement numbers 1441 to 2160 indicate the received voltage of the received polarization z measured at 720 antenna positions r.

FIG. 8 is a diagram showing an example of the measurement position table.
The measurement position table 133 is stored in the measurement data storage unit 121. The measurement position table 133 includes items of position number, x coordinate, y coordinate, and z coordinate. The position coordinates identify the antenna position r of the measurement antenna 111. One antenna position r is represented by three-dimensional coordinates including x-coordinates, y-coordinates and z-coordinates. However, in the second embodiment, since the two-dimensional near-field far-field transformation is adopted, the z-coordinate may be fixed to zero. As described above, in the case where the angles φ _a are at 0.5 degree intervals, 720 coordinates are recorded in the measurement position table 133.

FIG. 9 is a diagram showing an example of the position correspondence table.
The position correspondence table 134 is stored in the measurement data storage unit 121. The position correspondence table 134 indicates the correspondence between the measurement numbers of the measurement value table 132 and the position numbers of the measurement position table 133. When a certain measurement number is associated with a certain position number, the received voltage of the measurement value table 132 indicated by the measurement number indicates that the measurement is performed at the coordinates of the measurement position table 133 indicated by the position number. The position correspondence table 134 includes the same number of records as the measurement value table 132. When the reception voltage of the reception polarization of x, y, z is measured at one antenna position, the same position numbers are associated with the three measurement numbers.

  For example, position numbers 1 to 720 are associated with measurement numbers 1 to 720, respectively. Further, position numbers 1 to 720 are associated with measurement numbers 721 to 1440. In addition, position numbers 1 to 720 are associated with measurement numbers 1441 to 2160.

FIG. 10 is a diagram showing an example of a polarization angle table.
The polarization angle table 135 is stored in the measurement data storage unit 121. The polarization angle table 135 enumerates polarization angles (antenna angles). The polarization angle table 135 includes polarization angle numbers, x-axis angles, y-axis angles and z-axis angles. The polarization angle number identifies a three-dimensional polarization angle. The angle of each of the x-axis, y-axis and z-axis is expressed in radians. The measurement antenna 111 can set the polarization angle of the transmitting antenna and the polarization angle of the receiving antenna separately. For example, 723 polarization angles are recorded in the polarization angle table 135.

FIG. 11 is a diagram showing an example of the angle correspondence table.
The angle correspondence table 136 is stored in the measurement data storage unit 121. The angle correspondence table 136 includes items of measurement number, transmission polarization angle and reception polarization angle. The angle correspondence table 136 has one polarization angle number of the polarization angle of the transmitting antenna and one polarization angle of the receiving antenna from the polarization angle table 135 for one measurement number of the measurement value table 132. Correspond to one wave angle number. When a certain measurement number is associated with a certain polarization angle number, the received voltage of the measurement value table 132 indicated by the measurement number is measured by the polarization angle of the polarization angle table 135 indicated by the polarization angle number. Show that. The angle correspondence table 136 includes the same number of records as the measurement value table 132.

  For example, polarization angle numbers 4 to 723 are associated with the measurement numbers 1 to 720 as transmission polarization angles. Further, polarization angle numbers 4 to 723 are associated with the measurement numbers 721 to 1440 as transmission polarization angles. Further, polarization angle numbers 4 to 723 are associated with the measurement numbers 1441 to 2160 as transmission polarization angles. Further, the polarization angle number 1 is associated with the measurement numbers 1 to 720 as the reception polarization angle. The polarization angle number 2 is associated with the measurement numbers 721 to 1440 as the reception polarization angle. Further, the polarization angle number 3 is associated with the measurement numbers 1441 to 2160 as the reception polarization angle.

FIG. 12 is a diagram showing an example of the directivity table.
The directivity table 137 is stored in the measurement data storage unit 121. Here, it is assumed that the transmitting antenna and the receiving antenna are the same and the case of a small dipole antenna is assumed, and the directivity table 137 is applied to both the directivity of the transmitting antenna and the directivity of the receiving antenna. The directivity table 137 includes the items of θ angle, φ angle, θ directivity real part, θ directivity imaginary part, φ directivity real part, and φ directivity imaginary part. The θ angle is an angle between a certain direction and the z axis. The φ angle is the angle between a certain direction and the x axis. The directivity of the θ component is represented by a complex number including a real part and an imaginary part. The directivity of the φ component is represented by a complex number including a real part and an imaginary part.

  However, since a small dipole antenna along the z axis is assumed here, the φ directivity real part and the φ directivity imaginary part are fixed to zero. In addition, since the directivity data is not affected even if the φ angle changes, φ angles other than 0 are omitted. When another type of antenna is used, φ directivity real part and φ directivity imaginary part other than 0 may be registered in directivity table 137. Also, multiple φ angles may be registered for one θ angle. For example, the θ angle changes at intervals of 2 degrees from 1, 3, 5,..., 179 and the angle φ changes at intervals of 2 degrees from 0, 2, 4,.

The directivity recorded in the directivity table 137 is expressed in the local coordinate system of the measurement antenna 111. The values recorded in the directivity table 137 can be converted into values in the global coordinate system using the polarization angle table 135 and the angle correspondence table 136. Conversion from local coordinates to global coordinates using the polarization angle table 135 is performed in the order of z-axis (γ), y-axis (β), x-axis (α). The directivity of the global coordinate system after conversion is substituted into W _R (β) and W _T (β) of Expression (2).

FIG. 13 is a diagram showing an example of a far RCS table.
The far RCS table 138 is stored in the RCS data storage unit 124. Distant RCS table 138 includes entries for β angle and RCS. The β angle indicates the scattering angle estimated for the far RCS. The RCS of the far RCS table 138 is an estimate of the far RCS calculated according to Equation (2), and its unit is dBsm.

Next, the processing procedure of the RCS measurement apparatus 100 will be described. As described above, the first method and the second method can be considered as a method of determining the division size a so as to satisfy Expression (9).
FIG. 14 is a flow chart showing an example of the procedure of the first near-field far-field transformation.

  (S10) The area dividing unit 123 specifies the allowable error x of the amplitude approximation of the Green function. For example, the area division unit 123 receives an input of the allowable error x from the user. Also, for example, the region division unit 123 sets the allowable error x to x = 0.1 (10%).

(S11) The area dividing unit 123 calculates the minimum distance min | r−r ^* | between the measurement antenna 111 and the measurement object 30. This minimum distance is the minimum value of the distance between the antenna position r and the scattering point r ^* . The minimum distance is the minimum value across all antenna positions r while the antenna position r changes. The minimum distance may be calculated by the area dividing unit 123 receiving an input from the user, or may be calculated using the shape data of the measurement object 30 by the area dividing unit 123.

(S12) the area dividing unit 123, the minimum value min of the distance between the antenna position r and the center position _{r p} | as an approximation, the minimum distance min in step _{S11 | | r-r p r} -r * | to adopt. min | r−r ^* | is a value slightly smaller than the original min | r−r _p |. On the other hand, min | r−r ^* | does not depend on the division size a. By replacing min | r−r _p | on the right side of Expression (9) with min | r−r ^* |, Expression (11) for obtaining the division size a ^* (temporary division size) is obtained. The area division unit 123 substitutes the tolerance x in step S10 and the minimum distance min | r−r ^* | in step S11 into the right side of equation (11) to calculate the division size a ^* . The division size a ^* calculated here is the maximum value satisfying expression (11), and is a value obtained by replacing the inequality sign of expression (11) with an equal sign.

(S13) The area dividing unit 123 determines the number of divisions M = D / 2a ^* . If D / 2a ^* is not an integer, the decimal part is rounded up to make the division number M an integer.
(S14) The area division unit 123 determines the division size a = D / 2M. Thus, a division size a is determined so as to equally divide the representative dimension D by M.

(S15) Near-field far-field converter 122, determines a truncation parameter N of the transfer function _{T N} and N = 2ka according to Equation (4).
(S16) The near-field far-field converter 122 logically divides the measurement object 30 into divided areas of radius a, and calculates the center position r _p of each divided area using shape data such as representative dimension D. . The near-field / far-field transformation unit 122 uses the measurement data stored in the measurement data storage unit 121 and the equation (2) to generate a simultaneous equation including S (β) indicating the far RCS of each scattering angle β as an unknown variable. Generate The near-field / far-field transformation unit 122 solves the generated simultaneous equations, calculates an estimated value of the far RCS at each scattering angle β to generate RCS data, and stores the RCS data in the RCS data storage unit 124. The RCS data stored in the RCS data storage unit 124 is visualized by, for example, the RCS display unit 125 and displayed on the display 112.

According to the first method described above, by approximating min | r−r _p | with min | r−r ^* |, it is possible to eliminate the dependency on the division size a. Therefore, the amount of calculation for determining the appropriate division size a is reduced. Further, since the approximate value min | r−r ^* | is smaller than the original min | r−r _p |, the division size a is slightly smaller than the allowable error x. Therefore, in the near-field to far-field transformation by the first method, the accuracy is slightly higher than the accuracy assumed from the tolerance x, and the calculation amount is slightly larger than the calculation complexity estimated from the tolerance x.

FIG. 15 is a flowchart showing a procedure example of second near-field far-field transformation.
(S20) The area dividing unit 123 specifies the allowable error x of the amplitude approximation of the Green function. For example, the area division unit 123 receives an input of the allowable error x from the user. Also, for example, the region division unit 123 sets the allowable error x to x = 0.1 (10%).

(S21) The area division unit 123 initializes the division number M to M = 1.
(S22) The area division unit 123 updates the division number M to M + 1.
(S23) The area division unit 123 calculates a division size a = D / 2M.

(S24) The area dividing unit 123 logically divides the measurement target 30 into divided areas of radius a, and calculates the central position r _p of each divided area using shape data such as representative dimensions D.
(S25) The area dividing unit 123 comprehensively calculates the distance between each antenna position r of the measurement antenna 111 and the central position r _p of each divided area, and calculates the minimum distance min | r−r _p |. The minimum distance is the minimum value across all antenna positions r while the antenna position r changes.

(S26) The area dividing unit 123 substitutes the tolerance error x and min | r−r _p | of step S25 into the right side of Formula (9), and substitutes the division size a into the left side of Formula (9). Then, the area division unit 123 determines whether the condition of Expression (9) is satisfied under the current number of divisions M. If the condition of Formula (9) is satisfied, the process proceeds to step S27. If the condition of Formula (9) is not satisfied, the process proceeds to step S22.

(S27) The area division unit 123 determines the division size a and the division number M.
(S28) Near-field far-field converter 122, determines a truncation parameter N of the transfer function _{T N} and N = 2ka according to Equation (4).

(S29) The near-field far-field converter 122 logically divides the measurement object 30 into divided areas of radius a, and calculates the center position r _p of each divided area using shape data such as representative dimension D. . The near-field / far-field transformation unit 122 uses the measurement data stored in the measurement data storage unit 121 and the equation (2) to generate a simultaneous equation including S (β) indicating the far RCS of each scattering angle β as an unknown variable. Generate The near-field / far-field transformation unit 122 solves the generated simultaneous equations, calculates an estimated value of the far RCS at each scattering angle β to generate RCS data, and stores the RCS data in the RCS data storage unit 124. The RCS data stored in the RCS data storage unit 124 is visualized by, for example, the RCS display unit 125 and displayed on the display 112.

  According to the above-described second method, it is possible to obtain the largest division size a in the range in which the amplitude approximation error of the Green function can be suppressed to the allowable error x or less. Therefore, the near-field far-field transformation by the second method can reduce the amount of calculation compared to the near-field far-field transformation by the first method.

Next, a simulation example of the near-field far-field transformation of the second embodiment will be described. Below, two examples of simulation of a ship model and a random flat plate model are illustrated.
FIG. 16 is a diagram showing an example of a ship model.

  In this simulation example, the measurement object 41 is a long and thin ship, and the representative dimension D is 700 m. The center of the measurement object 41 is the origin of the xy plane, and the measurement object 41 is disposed on the x axis. The measurement antenna 111 is disposed on the circumference of a circle 42 with a radius of 700 m centered on the origin. The frequency f of the radar wave is f = 10 MHz, transmission is vertical polarization by the small dipole (electric field is in the z direction), and reception is three-direction polarization of x, y, z by the small dipole. The transmission of the radar wave and the reception of the reflected wave are performed at the same position.

FIG. 17 is a diagram showing an example of an error table for a ship model.
The error table 141 shows the simulation result of the ship model of FIG. The error table 141 includes items of the number of divisions, NRMSE (Normalized Root Mean Square Error), amplitude approximation error of the first method, and amplitude approximation error of the second method.

NRMSE is a transformation error of the near-field far-field transformation defined by equation (12). In equation (12), σ _ref (β _q ) is the correct far RCS (reference value) at the scattering angle β _q , and σ _tr (β _q ) is the far RCS at the scattering angle β _q calculated by near-field far-field transformation Is an estimated value of The amplitude approximation error of the first method is calculated from Expression (9) using the division size a determined by the first method and min | r−r ^* | (the approximate value of min | r−r _p |) It is the value of x. The amplitude approximation error of the second method is the value of x calculated from equation (9) using the division size a determined by the second method and min | r−r _p |. In the error table 141, the unit of the amplitude approximation error of the first method and the amplitude approximation error of the second method is%.

  According to the first method, the minimum division number M is M = 16 in the range in which the amplitude approximation error of the Green function is 10% or less. According to the second method, the minimum number M of divisions in the range in which the amplitude approximation error of the Green function is 10% or less is M = 15. NRMSE indicating the conversion error of the near-field far-field conversion decreases as the division number M increases. However, NRMSE converges with the increase of the division number M, and the decrease amount of NRMSE by increasing the division number M decreases. According to this simulation example, the conversion errors of the near-field far-field conversion sufficiently converge at the division numbers M = 15 and M = 16. Therefore, when the tolerance error x of the Green function's amplitude approximation is set to 10%, the estimation accuracy of the far RCS can be balanced with the calculation amount of the near field far field conversion, and the high precision far RCS can be efficiently performed. It can be calculated.

FIG. 18 is a graph showing a first RCS calculation example of the ship model.
Graph 50a shows the far RCS for each scattering angle β. Curve 51 shows the correct far RCS (reference value). A curve 52 represents an estimated value of far RCS when near-field far-field transformation is performed without dividing the measurement object 41 into a plurality of divided regions. The far RCS indicated by the curve 52 has a large error relative to the far RCS indicated by the curve 51.

FIG. 19 is a graph showing a second RCS calculation example of the ship model.
Graph 50b shows the far RCS for each scattering angle β, similar to graph 50a. Curve 51 shows the correct far RCS (reference value). A curve 53 shows an estimated value of far RCS when near-field far-field transformation is performed by dividing the measurement object 41 into a plurality of divided regions with a division number M = 15. The far RCS indicated by the curve 53 is sufficiently close to the far RCS indicated by the curve 51, and the conversion error of the near-field far-field conversion is suppressed sufficiently small.

FIG. 20 is a graph showing a third RCS calculation example of the ship model.
The graph 50c shows the far RCS with respect to each scattering angle β, similarly to the graphs 50a and 50b. Curve 51 shows the correct far RCS (reference value). A curve 54 shows an estimated value of far RCS when near-field far-field transformation is performed by dividing the measurement object 41 into a plurality of divided regions with a division number M = 16. The far RCS shown by the curve 54 is sufficiently close to the far RCS shown by the curve 51, and the conversion error of the near-field far-field conversion is suppressed sufficiently small.

FIG. 21 is a diagram showing an example of a random plate model.
The random flat plate model is a model in which a plurality of small flat plates are randomly rotated and arranged. In this simulation example, a plurality of flat plates as the measurement object 61 are arranged at intervals on the y axis. The distance from the plate at one end to the plate at the other end is a representative dimension D = 1 m. The center of the measurement object 61 is the origin of the xy plane. The measurement antenna 111 is disposed on the circumference of a circle 62 with a radius of 1 m centered on the origin. The frequency f of the radar wave is 3 GHz, transmission is horizontal polarization (small electric field in the xy direction) by a small dipole, and reception is three-direction polarization of x, y, z by a small dipole. The transmission of the radar wave and the reception of the reflected wave are performed at the same position.

FIG. 22 is a diagram showing an example of an error table for a random plate model.
The error table 142 shows the simulation result of the random plate model of FIG. Similar to the error table 141, the error table 142 includes the items of the division number, NRMSE, amplitude approximation error of the first method, and amplitude approximation error of the second method.

  According to the first method, the minimum division number M is M = 16 in the range in which the amplitude approximation error of the Green function is 10% or less. According to the second method, the minimum number M of divisions in the range in which the amplitude approximation error of the Green function is 10% or less is M = 15. According to this simulation example, the conversion errors of the near-field far-field conversion sufficiently converge at the division numbers M = 15 and M = 16. Therefore, when the tolerance error x of the Green function's amplitude approximation is set to 10%, the estimation accuracy of the far RCS can be balanced with the calculation amount of the near field far field conversion, and the high precision far RCS can be efficiently performed. It can be calculated. Note that the amplitude approximation error of the error table 141 and the amplitude approximation error of the error table 142 are the same because the ratio of the representative dimension D and the moving radius of the measurement antenna 111 is 1: 1. If the ratio of the representative dimension D to the moving radius of the measurement antenna 111 changes, the amplitude approximation error also changes to the error tables 141 and 142.

FIG. 23 is a graph showing a first RCS calculation example of the random plate model.
Graph 70a shows the far RCS for each scattering angle β. Curve 71 shows the correct far RCS (reference value). A curve 72 shows an estimated value of far RCS when near-field far-field transformation is performed without dividing the measurement object 61 into a plurality of divided regions. The far RCS indicated by the curve 72 has a large error relative to the far RCS indicated by the curve 71.

FIG. 24 is a graph showing a second RCS calculation example of the random plate model.
Graph 70b shows the far RCS for each scattering angle β, as does graph 70a. Curve 71 shows the correct far RCS (reference value). A curve 73 represents an estimated value of far RCS when near-field far-field transformation is performed by dividing the measurement object 61 into a plurality of divided regions with a division number M = 15. The far RCS indicated by the curve 73 is sufficiently close to the far RCS indicated by the curve 71, and the conversion error of the near-field far-field conversion is sufficiently suppressed.

FIG. 25 is a graph showing a third RCS calculation example of the random plate model.
The graph 70c shows the far RCS for each scattering angle β, similarly to the graphs 70a and 70b. Curve 71 shows the correct far RCS (reference value). A curve 74 shows an estimated value of far RCS when near-field far-field transformation is performed by dividing the measurement object 61 into a plurality of divided regions with a division number M = 16. The far RCS shown by the curve 74 is sufficiently close to the far RCS shown by the curve 71, and the conversion error of the near-field far-field conversion is suppressed sufficiently small.

  According to the information processing system of the second embodiment, it is possible to estimate the far RCS by near-field far-field transformation from the measurement result of the reflected wave in the vicinity of the measurement object. Therefore, the remote RCS can be determined by using a compact anechoic chamber, and the RCS of a large scatterer can be efficiently determined. Further, by performing near-field far-field conversion by dividing the measurement object logically into a plurality of divided regions, it is possible to reduce the amplitude approximation error of the Green function and reduce the conversion error of the near-field far-field conversion it can.

  Also, if a tolerance for the Greene function amplitude approximation is specified, the largest possible division size (small number of divisions) is automatically determined within the range where the amplitude approximation error is less than the allowable error. Therefore, compared with the case where the division size is set depending on the user's experience and intuition, the risk of the near-field far-field transformation accuracy becoming extremely low and the risk that the amount of calculation becomes excessively large are reduced. It is possible to perform conversion efficiently. Also, by setting the tolerance of the Green function's amplitude approximation to 10%, it is possible to calculate the far RCS with high accuracy in a short time.

DESCRIPTION OF SYMBOLS 10 Estimator 11 Storage part 12 Processing part 13 Position data 14 Measured value data 15 Distance 16 Tolerance error 17 Division size 18 Reflection cross section 19 Intensity 21 Object 22 Measurement position

Claims (7)

On the computer
Acquiring position data indicating a measurement position at which a reflected wave corresponding to the radio wave irradiated to the object is measured, and measurement value data indicating a measurement result of the reflected wave at the measurement position;
Based on the distance calculated between the object and the measurement position using the position data and a tolerance specified for an error occurring according to the division method of the region including the object Determining the division size of a plurality of division areas divided from the area including the object;
The reflection cross-sectional area or the reflection wave corresponding to the object when the reflection wave is measured at a position farther from the object than the measurement position using the determined division size and the measurement value data Estimate the strength,
An estimation program that causes the process to run. In the determination of the division size, the division size corresponding to the calculated distance and the designated tolerance is selected using correspondence information indicating the relationship between the error, the distance, and the division size.
The estimation program according to claim 1. Use the minimum distance between the object and the measurement position as the calculated distance,
The estimation program according to claim 1. As the calculated distance, the minimum distance of the distances between the measurement position and the representative point of each of the plurality of divided areas is used,
In the determination of the division size, different minimum distances corresponding to different division sizes are calculated, and among the different division sizes, a division size that satisfies a predetermined relationship between the calculated minimum distance and the designated tolerance. select,
The estimation program according to claim 1. The error is an approximation process for approximating a distance between an arbitrary point in the divided area and the measurement position for each of the plurality of divided areas by a distance between a representative point in the divided area and the measurement position. Is an error that occurs according to
The estimation program according to claim 1. A storage unit storing position data indicating a measurement position at which a reflected wave corresponding to a radio wave irradiated to an object is measured, and measurement value data indicating a measurement result of the reflected wave at the measurement position;
Based on the distance calculated between the object and the measurement position using the position data and a tolerance specified for an error occurring according to the division method of the region including the object The division size of a plurality of division areas divided from the area including the object is determined, and using the determined division size and the measurement value data, at a position farther from the object than the measurement position A processing unit that estimates a reflection cross-sectional area corresponding to the object when measuring the reflected wave or an intensity of the reflected wave;
An estimation device having A computer implemented estimation method,
Acquiring position data indicating a measurement position at which a reflected wave corresponding to the radio wave irradiated to the object is measured, and measurement value data indicating a measurement result of the reflected wave at the measurement position;
Based on the distance calculated between the object and the measurement position using the position data and a tolerance specified for an error occurring according to the division method of the region including the object Determining the division size of a plurality of division areas divided from the area including the object;
The reflection cross-sectional area or the reflection wave corresponding to the object when the reflection wave is measured at a position farther from the object than the measurement position using the determined division size and the measurement value data Estimate the strength,
Estimation method.

Images