阅读说明：本技术 一种目标远场散射最小试验距离判定方法 (method for judging minimum test distance of far-field scattering of target ) 是由 方重华 奚秀娟 于 2019-08-27 设计创作，主要内容包括：一种目标远场散射最小试验距离判定方法,包括如下步骤：步骤1:确定目标及其工况,包含最高频率,极化状态,入射角度；步骤2:基于(1)中的工况,利用仿真手段对目标进行给定角域范围内进行一维距离成像；步骤3:对(2)中所获取的多幅一维距离像进行强散射源最大距离对比,找出最大的强散射源间距；步骤4:将步骤3中最大的强散射源间距代入最小试验距离判定公式,即可获取给定条件下的最小试验距离；本发明通过一维距离像而不是传统的公式来进行判定,更有效和实用；大大降低试验距离要求；成本相对较低；环节简化；该发明可用于多类目标,为其开展远场散射试验时甄选最小的试验距离提供指导。(A method for judging the minimum experimental distance of far-field scattering of a target comprises the following steps: step 1, determining a target and working conditions thereof, including highest frequency, polarization state and incident angle; based on the working condition in the step (1), performing one-dimensional distance imaging on the target in a given angular domain range by using a simulation means; step 3, comparing the maximum distances of the strong scattering sources of the multiple one-dimensional range images obtained in the step 2 to find out the maximum distance between the strong scattering sources; step 4, substituting the maximum strong scattering source distance in the step 3 into a minimum test distance judgment formula to obtain the minimum test distance under the given condition; the invention judges by a one-dimensional distance image instead of the traditional formula, and is more effective and practical; the requirement on test distance is greatly reduced; the cost is relatively low; the link is simplified; the method can be used for various targets and provides guidance for selecting the minimum test distance when the far-field scattering test is carried out.)

1. A method for judging the minimum experimental distance of far-field scattering of a target is characterized by comprising the following steps: the method comprises the following steps:

Step 1, determining a target and working conditions thereof, including highest frequency, polarization state and incident angle;

Based on the working condition in the step (1), performing one-dimensional distance imaging on the target in a given angular domain range by using a simulation means;

step 3, comparing the maximum distances of the strong scattering sources of the multiple one-dimensional range images obtained in the step 2 to find out the maximum distance between the strong scattering sources;

Step 4, substituting the maximum strong scattering source distance in the step 3 into a minimum test distance judgment formula, 2D²In/λ, D is the target maximum size, in this caseIn the method, D is the maximum strong scattering source distance obtained in the step 3, and lambda is the test wavelength, so that the minimum test distance under the given condition can be obtained.

2. the method of claim 1, wherein: the simulation means in the step 2 is specifically that the electromagnetic wave irradiation and receiving simulation of the target adopts OpenGL to perform graphic processing; firstly, completing the appearance modeling and mesh subdivision of a target to form a subdivision geometric model which can be called into graphic electromagnetic calculation, and displaying a target three-dimensional model on a screen through OpenGL; electromagnetic waves are made to irradiate to object along vertical screen direction, and in computer, by means of von's illumination model of computer graphics, 3 kinds of light beams with different colors are simultaneously irradiated to object model to render the object in color, and the color components (R, G, B) of pixel points are used to determine the normal vector (n) of irradiated part_x、n_y、n_z) Then, according to the depth information of each position of the target point in the calculation area, converting the physical optical integral of electromagnetic calculation into pixel summation through graphic electromagnetic calculation to obtain a target RCS; and then, a frequency stepping pulse compression method is adopted, a group of pulse strings with carrier frequencies changing according to fixed stepping frequency are transmitted to irradiate the target, and the received target echo RCS under different frequency irradiation is subjected to fast Fourier inverse transformation matched filtering to obtain a one-dimensional range profile of the target.

3. The method of claim 1, wherein: the specific method for finding out the maximum strong scattering source distance in the step 3 is as follows: and measuring the maximum horizontal distance of the parallel dotted lines in the one-dimensional distance image by using a ruler, and then converting the maximum horizontal distance into an actual distance according to a coordinate axis, wherein the actual distance is the maximum strong scattering source distance.

Technical Field

The invention relates to the field of electromagnetic scattering, in particular to a method for judging the minimum test distance of far-field scattering of a target.

Background

The conventional target far-field scattering test distance is generally expressed by a far-field condition formula (2D)²λ, D is the target maximum size, λ is the test wavelength) are givenit is generally considered that under the condition of the distance, an accurate far-field scattering result of the target can be directly obtained. For large targets (such as ship targets and airplane targets), the far-field distance given by the far-field condition formula is often not satisfied in practical tests due to the large size. For example, for an aircraft with a length of 20m, under a typical frequency condition of 10GHz, the corresponding far-field distance is about 27km, which exceeds the effective test distance of the domestic existing test field. Therefore, it is very important to be able to directly obtain far-field scattering results of the target at a relatively close distance (far less than the far-field conditional formula condition).

For the problems, a near-far field conversion-based test method is developed at home and abroad, and a near-field scattering result of a target can be obtained at a short distance and converted to obtain a far-field result. However, this type of method requires the use of near-far field switching, adding an intermediate link and not directly obtaining far field results. In addition, the testing method based on near-far field conversion requires a special testing system, which tends to increase the testing cost. On the other hand, domestic and foreign researches find that the scattering result directly obtained by some targets (such as flat plates) at a distance far smaller than the far-field condition formula condition has small difference with the accurate far-field scattering result. Although the relevant research does not give the criterion of 'how close' distance, the relevant research still gives us a heuristic to invent a judgment method: for a large target, determining a 'minimum test distance' far smaller than a far-field distance, and comparing a scattering result obtained under the distance condition with an accurate far-field scattering result to meet a given precision requirement, thereby providing a brand new idea for the far-field scattering test of the large target.

Disclosure of Invention

The invention aims to solve the problems that: for a large target, a 'minimum test distance' far smaller than the far-field distance is determined, and the scattering result obtained under the condition of the distance is compared with an accurate far-field scattering result (referring to a statistical method of the total RCS value in the HJB 180), so that the engineering precision requirement can be met (the distance is usually within 3 dB).

The technical scheme adopted by the invention is as follows: a method for judging the minimum experimental distance of far-field scattering of a target is characterized by comprising the following steps: the method comprises the following steps:

step 1, determining a target and working conditions thereof, including highest frequency, polarization state and incident angle;

Based on the working condition in the step (1), performing one-dimensional distance imaging on the target in a given angular domain range by using a simulation means;

Step 3, comparing the maximum distances of the strong scattering sources of the multiple one-dimensional range images obtained in the step 2 to find out the maximum distance between the strong scattering sources;

Step 4, substituting the maximum strong scattering source distance in the step 3 into a minimum test distance judgment formula, 2D²In the lambda, D is the maximum size of the target, in the method, D is the maximum strong scattering source distance obtained in the step 3, and lambda is the test wavelength, so that the minimum test distance under the given condition can be obtained.

Further, the simulation means is specifically that the electromagnetic wave irradiation and receiving simulation of the target is to adopt OpenGL to perform graphic processing; firstly, completing the appearance modeling and mesh subdivision of a target to form a subdivision geometric model which can be called into graphic electromagnetic calculation, and displaying a target three-dimensional model on a screen through OpenGL; electromagnetic waves are made to irradiate to object along vertical screen direction, and in computer, by means of von's illumination model of computer graphics, 3 kinds of light beams with different colors are simultaneously irradiated to object model to render the object in color, and the color components (R, G, B) of pixel points are used to determine the normal vector (n) of irradiated part_x、n_y、n_z) Then, according to the depth information of each position of the target point in the calculation area, converting the physical optical integral of electromagnetic calculation into pixel summation through graphic electromagnetic calculation to obtain a target RCS; and then, a frequency stepping pulse compression method is adopted, a group of pulse strings with carrier frequencies changing according to fixed stepping frequency are transmitted to irradiate the target, and the received target echo RCS under different frequency irradiation is subjected to fast Fourier inverse transformation matched filtering to obtain a one-dimensional range profile of the target.

Further, the specific method for finding the maximum strong scattering source distance in step 3 is as follows: and measuring the maximum horizontal distance of the parallel dotted lines in the one-dimensional distance image by using a ruler, and then converting the maximum horizontal distance into an actual distance according to a coordinate axis, wherein the actual distance is the maximum strong scattering source distance.

the invention has the advantages and characteristics that:

(1) The method can be used for various targets and provides guidance for selecting the minimum test distance when the far-field scattering test is carried out.

(2) The judgment is carried out by a one-dimensional distance image instead of a traditional formula, and the method is more effective and practical.

(3) Greatly reduces the requirement of test distance, and can directly carry out far-field scattering test on the target under the condition of far less than the far-field distance.

(4) the cost is relatively low-a special near-far field conversion-based test system is not needed, and the traditional far-field scattering test method and the test system can be directly utilized.

(5) The link is simplified, the far field scattering result of the target is directly obtained, near-far field transformation is not needed, and the engineering requirements are met.

drawings

FIG. 1 is a simplified, general schematic diagram of a large target according to a preferred embodiment of the present invention;

FIG. 2 is a schematic diagram of a one-dimensional range profile of a large target and its correlation with a structure, the maximum strong scattering source spacing;

FIG. 3HJB statistics comparison of total RCS values at different distances (pitch angle 90 degrees);

Detailed Description

The invention is further illustrated with reference to the accompanying drawings:

A method for judging the minimum experimental distance of far-field scattering of a target is characterized by comprising the following steps: the method comprises the following steps:

Step 1, determining a target and working conditions thereof, including highest frequency, polarization state and incident angle;

Based on the working condition in the step (1), performing one-dimensional distance imaging on the target in a given angular domain range by using a simulation means; the simulation means is that the electromagnetic wave irradiation and receiving simulation of the target adopts OpenGL to perform graphic processing; firstly, the shape modeling and the mesh subdivision of the target are completed to form the subdivision which can be transferred to the graph electromagnetic calculationa geometric model, which displays the target three-dimensional model on a screen through OpenGL; electromagnetic waves are made to irradiate to object along vertical screen direction, and in computer, by means of von's illumination model of computer graphics, 3 kinds of light beams with different colors are simultaneously irradiated to object model to render the object in color, and the color components (R, G, B) of pixel points are used to determine the normal vector (n) of irradiated part_x、n_y、n_z) Then, according to the depth information of each position of the target point in the calculation area, converting the physical optical integral of electromagnetic calculation into pixel summation through graphic electromagnetic calculation to obtain a target RCS; and then, a frequency stepping pulse compression method is adopted, a group of pulse strings with carrier frequencies changing according to fixed stepping frequency are transmitted to irradiate the target, and the received target echo RCS under different frequency irradiation is subjected to fast Fourier inverse transformation matched filtering to obtain a one-dimensional range profile of the target.

step 3, comparing the maximum distances of the strong scattering sources of the multiple one-dimensional range images obtained in the step 2 to find out the maximum distance between the strong scattering sources; the specific method comprises the following steps: and measuring the maximum horizontal distance of the parallel dotted lines in the one-dimensional distance image by using a ruler, and then converting the maximum horizontal distance into an actual distance according to a coordinate axis, wherein the actual distance is the maximum strong scattering source distance.

Step 4, substituting the maximum strong scattering source distance in the step 3 into a minimum test distance judgment formula, 2D²In the lambda, D is the maximum size of the target, in the method, D is the maximum strong scattering source distance obtained in the step 3, and lambda is the test wavelength, so that the minimum test distance under the given condition can be obtained.

Specific calculation examples:

(1) For a simplified large target as shown in fig. 1 (assuming an overall length of about 30m), the incident wave is assumed to have the following 3 frequencies (200MHz, 300MHz, and 400MHz, corresponding far-field distances of 1.2km (200MHz), 1.8km (300MHz), and 2.4km (400MHz), respectively), the polarization state is vertical polarization, the incident angle is 90 degrees in pitch, and the azimuth is 0 degrees (incident along the bow of the ship).

(2) Acquiring a one-dimensional distance image under the given working condition in the step (1) by using a simulation means, wherein the one-dimensional distance image is shown in fig. 2;

(3) as can be seen from FIG. 2, the maximum strong scattering source spacing is 11 m; .

(4) the minimum test distance under given conditions can be obtained by substituting the minimum test distance into a minimum test distance determination formula, wherein the minimum test distances are 161m (200MHz), 242m (300MHz) and 323m (400MHz) respectively.

(5) To verify the validity of this minimum trial distance determination, a simulation calculation of the scattering properties under different distance conditions was performed, as shown in fig. 3. Wherein, 2000m belongs to far-field distance for the 3 frequency points, so that the result at the distance can represent an accurate far-field scattering result. Under the total RCS value statistical method of the HJB180, the difference between the scattering result under the minimum test distance corresponding to the three frequency points and the corresponding accurate far-field scattering result is less than 3dB, so that the effectiveness of the method is verified.

The foregoing shows and describes the general principles and features of the present invention, together with the advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only for the purpose of illustrating the structural relationship and principles of the present invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.