Quantitative analysis method for surface wave electromagnetic scattering characteristics based on two-port transmission model

Abstract

The present application belongs to the technical field of stealth design of aircraft shape and structure, and discloses a surface wave electromagnetic scattering characteristic quantitative analysis method based on a two-port transmission model. The surface wave electromagnetic scattering characteristic quantitative analysis method based on the two-port surface wave transmission model has an electromagnetic discontinuous structure. By loading the electromagnetic discontinuous structure, the scattering parameters of the port network are monitored, and by changing the structural parameters of the electromagnetic discontinuous structure, the influence of the structural parameters of the electromagnetic discontinuous structure on the surface wave scattering characteristic is quantitatively studied. The surface wave electromagnetic scattering characteristic quantitative analysis method can separate the spatial electromagnetic scattering component when the spatial electromagnetic wave is directly irradiated, and can analyze the electromagnetic scattering characteristic of the surface wave in the discontinuous electromagnetic structure alone, thereby laying a foundation for studying the surface wave electromagnetic scattering characteristic of the electromagnetic discontinuous structure such as a curved surface, a gap and a step, and providing guidance for the stealth design of the aircraft shape and structure.

Description

Technical Field

[0001] This invention belongs to the field of stealth design technology for aircraft shape and structure, and specifically relates to a quantitative analysis method for surface wave electromagnetic scattering characteristics based on a two-port transmission model. Background Technology

[0002] In aircraft design, methods such as shape optimization and coating with radar-absorbing materials can significantly reduce the scattered field. Once important scattering sources such as specular scattering are suppressed, electromagnetic scattering caused by electromagnetic discontinuities becomes a significant contributor to scattering. Therefore, for aircraft design, it is necessary to further suppress the detrimental effects of electromagnetic discontinuities on overall stealth performance.

[0003] Current research on the electromagnetic scattering characteristics of electromagnetic discontinuities such as gaps and steps mainly focuses on the influence of key electrical dimensional parameters of electromagnetic discontinuities on scattering characteristics under electromagnetic wave irradiation in a space plane. These findings are of great significance for understanding the electromagnetic scattering characteristics of electromagnetic discontinuities under electromagnetic wave irradiation in a space plane. However, because the azimuth information of the incident wave is included, the scattering results include specular scattering and surface wave scattering under direct electromagnetic wave irradiation. Independent studies on surface wave scattering mainly focus on the absorption and attenuation characteristics of surface waves by materials, with few separate studies on the electromagnetic scattering characteristics of surface waves caused by electromagnetic discontinuities. Furthermore, aircraft surfaces are always composed of continuous curved surfaces. When viewed along a fixed direction, these continuous curved surfaces become concave or convex surfaces with continuously changing radii of curvature. Additionally, at structures such as variable sweep angles of aircraft or air intake lips, two intersecting quasi-planes form upward or downward dihedral angles. The electromagnetic scattering characteristics of surface waves from these electromagnetic discontinuities also urgently need to be studied.

[0004] Because stealth aircraft are coated with radar-absorbing materials, in order to control the overall weight of the stealth aircraft, on the one hand, the coating material must be thin and light, forming a waveguide structure that can effectively transmit surface waves. The waveguide structure can at least guarantee the transmission of the TM fundamental mode. On the other hand, when the surface of the stealth aircraft is irradiated by plane electromagnetic waves with a large swivel angle of incidence, there are longitudinal or transverse electric field components along the tangential direction of the metal surface. This excites surface waves to be stably transmitted along the dielectric layer of the aircraft's metal wall. Energy is effectively conducted from the irradiated area to the shadow area. When encountering electromagnetic discontinuities, a large number of spatial scattered waves are excited. The electromagnetic scattering characteristics of surface waves urgently need to be studied.

[0005] How to separate the surface wave scattering component from the electromagnetic discontinuity structure directly illuminated by space waves, and quantitatively study the influence of the key dimensional parameters of the discontinuity structure on surface wave scattering, so as to provide guidance for the stealth design of aircraft shape, has important engineering significance.

[0006] Currently, there is an urgent need to develop a quantitative analysis method for the electromagnetic scattering characteristics of surface waves based on a two-port transmission model. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a quantitative analysis method for the electromagnetic scattering characteristics of surface waves based on a two-port transmission model, so as to make up for the shortcomings of existing independent studies on the electromagnetic scattering characteristics of surface waves.

[0008] The present invention provides a quantitative analysis method for surface wave electromagnetic scattering characteristics based on a two-port transmission model. This method utilizes a two-port surface wave transmission model with an electromagnetic discontinuity structure. By loading the electromagnetic discontinuity structure and monitoring the scattering parameters of the port network, the method quantitatively studies the influence of the electromagnetic discontinuity structure on the electromagnetic scattering characteristics of surface waves by changing the structural parameters of the electromagnetic discontinuity structure.

[0009] Furthermore, the baseline model of the dual-port transmission model is a centrally symmetric structure, consisting of a planar waveguide I, a surface waveguide, and a planar waveguide II from left to right. The lower wall of planar waveguide I, the base plate of the surface waveguide, and the lower wall of planar waveguide II share the same metal plate. The upper walls of planar waveguide I and planar waveguide II have a centrally symmetric tapered gradient structure. The interiors of planar waveguide I and planar waveguide II, as well as the surface of the base plate of the surface waveguide, are filled with a lossless dielectric. An excitation port is provided on one end face of planar waveguide I, and a matching load port is provided on the symmetrical end face of planar waveguide II.

[0010] The electromagnetic discontinuity structure of the two-port transmission model is to set a convex electromagnetic discontinuity structure or a concave electromagnetic discontinuity structure at the center of the reference model; or to set a step or gap at the center of the reference model, with the step or gap forming an electromagnetic defect.

[0011] Furthermore, the loading method for the convex electromagnetic discontinuity structure is semi-circular ring loading, the loading method for the concave electromagnetic discontinuity structure is 1 / 4 circular ring loading, and the loading method for the steps or gaps is insertion into the interior of the two-port surface wave transmission model.

[0012] The present invention provides a quantitative analysis method for surface wave electromagnetic scattering characteristics based on a two-port transmission model, comprising the following steps:

[0013] S10. Monitor the reflection parameters S of the excitation port of a two-port surface wave propagation model with electromagnetic discontinuities. 11 Reflection parameter S 11 The echo scattering components of the discontinuous electromagnetic structure were characterized.

[0014] S20. Monitoring and Reflection Parameters S 11 The scattering parameter S of the corresponding matched load port 21 ;

[0015] S30. Calculate the scattering efficiency η = 1 - (S 11 ) 2 -(S 21 ) 2 ;

[0016] S40. Define the two-port surface wave transmission model without electromagnetic discontinuity structure as the reference model. The scattering efficiency of the reference model is η0. The scattering efficiency of the two-port surface wave transmission model with electromagnetic discontinuity structure is η. By comparing the two-port surface wave transmission model with electromagnetic discontinuity structure with the reference model, the spatial leakage scattering capability of electromagnetic discontinuity structure for surface waves is obtained.

[0017] The present invention provides a quantitative analysis method for surface wave electromagnetic scattering characteristics based on a two-port transmission model. By quantitatively monitoring the scattering parameters of the ports, the method studies the surface wave electromagnetic scattering characteristics of electromagnetic discontinuous structures and obtains the correspondence between the key size parameters of the electromagnetic discontinuous structures and the wavelength, scattering intensity, and reflection intensity.

[0018] The quantitative analysis method for surface wave electromagnetic scattering characteristics based on a two-port transmission model of the present invention removes the spatial electromagnetic scattering component when directly illuminated by space electromagnetic waves, and can analyze the electromagnetic scattering characteristics of surface waves in discontinuous electromagnetic structures independently. This lays the foundation for studying the surface wave electromagnetic scattering characteristics of electromagnetic discontinuous structures such as curved surfaces, gaps, and steps, and provides guidance for the stealth design of aircraft shape and structure. Attached Figure Description

[0019] Figure 1a A schematic diagram of the structure of a two-port surface wave transmission model (xoz plan view);

[0020] Figure 1b A schematic diagram of the structure of a two-port surface wave transmission model (xoy plane view);

[0021] Figure 2a This refers to the loading method for the semi-circular annular convex surface in a discontinuous electromagnetic structure.

[0022] Figure 2b This refers to the 1 / 4 circular concave surface loading method in a discontinuous electromagnetic structure.

[0023] Figure 3a This refers to the step loading method in defective electromagnetic structures.

[0024] Figure 3b This refers to the gap loading method in defective electromagnetic structures.

[0025] In the figure, 1. Excitation section; 2. Matching load section; 3. Metal wall of the planar waveguide of the excitation section; 4. Inner dielectric of the excitation section; 5. Lower metal base plate of the planar waveguide of the excitation section; 6. Feed port of the excitation section; 7. Metal wall of the planar waveguide of the matching load section; 8. Inner dielectric of the matching load section; 9. Lower metal base plate of the planar waveguide of the matching load section; 10. Matching load port of the matching load section; 11. Semi-circular convex surface; 12. Semi-circular metal base plate; 13. Semi-circular coated dielectric; 14. 1 / 4 circle concave surface; 15. 1 / 4 circle metal base plate; 16. 1 / 4 circle coated dielectric; 17. Step; 18. Gap. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] Example 1:

[0028] This embodiment presents a typical two-port surface wave transmission model structure, i.e., a reference model.

[0029] like Figure 1a As shown, the baseline model consists of an excitation part 1 and a matching load part 2 connected in sequence, and the overall structure is symmetrical about the xoy plane.

[0030] The excitation section 1 includes, from top to bottom, a planar waveguide upper metal wall 3, an inner filling medium 4, and a planar waveguide lower metal base plate 5 of the excitation section. The planar waveguide upper metal wall 3 of the excitation section has a tapered gradient structure, and the feed port 6 of the excitation section is installed on the inner filling medium 4. Correspondingly, the matching load section 2 includes, from top to bottom, a planar waveguide upper metal wall 7, an inner filling medium 8, and a planar waveguide lower metal base plate 9 of the matching load section. The planar waveguide upper metal wall 7 of the matching load section has a tapered gradient structure corresponding to the tapered gradient structure of the planar waveguide upper metal wall 3 of the excitation section, and the matching load port 10 of the matching load section is installed on the inner filling medium 8.

[0031] The metal wall surface 3 on the planar waveguide of the excitation section and the metal wall surface 7 on the planar waveguide of the matching load section have a metal wall thickness of t2 in the x-direction and a length of L1 in the z-direction. The length of the tapered gradient structure is L2. The filler dielectric 4 in the excitation section and the filler dielectric 8 in the matching load section have a thickness of t along the x-axis in the planar waveguide section and a thickness of h in the surface waveguide section. The portion of the planar waveguide outside the tapered gradient structure of the metal wall surface 3 and the metal wall surface 7 on the planar waveguide of the matching load section is filled with a lossless dielectric with a dielectric constant of μ and a permeability of ε. The metal base plate 5 under the planar waveguide of the excitation section and the metal base plate 9 under the planar waveguide of the matching load section have a thickness of t1 in the x-axis direction and a total length of L in the z-axis direction. Figure 1b As shown, the width of the two-port surface wave transmission model along the y-axis is w.

[0032] Energy matching design is performed on the benchmark model, with the power supply input via feed port 6 of the excitation section. The reflection parameter of feed port 6 of the excitation section is S. 11(0) The matching load port 10 of the matching load section is connected to an external matching load, and the scattering parameter of the matching load port 10 of the matching load section is S. 21(0) .

[0033] By optimizing the main structural parameters t, h, and L2, the reflection parameter S can be improved. 11(0) <-20dB, and make the scattering parameter S 21(0) As large as possible. The scattering efficiency η0 of the baseline model is:

[0034] η0=1-(S 11(0) ) 2 -(S 21(0) ) 2 (1)

[0035] Example 2:

[0036] This embodiment presents a typical curved discontinuous electromagnetic structure.

[0037] Figure 2aThe loading method of the semi-circular annular convex surface 11 in the discontinuous electromagnetic structure differs from that in Embodiment 1. A semi-circular annular convex surface 11 is provided between the excitation part 1 and the matching load part 2 of the two-port surface wave transmission model. The semi-circular annular convex surface 11 includes a semi-circular annular metal base plate 12 and a semi-circular annular coated medium 13 stacked sequentially from the outside to the inside. The width of the semi-circular annular convex surface 11 in the y-axis direction is w; the thickness of the semi-circular annular metal base plate 12 is t1, its inner radius is R1, and its outer radius is R1+t1. One end of the semi-circular annular metal base plate 12 is connected to the planar waveguide lower metal base plate 5 of the excitation part, and the other end is connected to the planar waveguide lower metal base plate 9 of the matching load part. The thickness of the semi-circular annular coated medium 13 is h, its inner radius is R1+t1, and its outer radius is R1+t1+h. One end of the semi-circular annular coated medium 13 is connected to the inner filling medium 4 of the excitation part, and the other end is connected to the inner filling medium 8 of the matching load part. The connected parts are tangent.

[0038] Figure 2b The loading method of the 1 / 4-ring concave surface 14 in the discontinuous electromagnetic structure differs from that in Embodiment 1. A 1 / 4-ring concave surface 14 is provided between the excitation part 1 and the matching load part 2 of the two-port surface wave transmission model. The 1 / 4-ring concave surface 14 includes a 1 / 4-ring metal base plate 15 and a 1 / 4-ring coated medium 16 stacked sequentially from the outside to the inside. The width of the 1 / 4-ring concave surface 14 in the y-axis direction is w; the thickness of the 1 / 4-ring metal base plate 15 is t1, the inner radius is R2+h, and the outer radius is R2+h+t1. One end of the 1 / 4-ring metal base plate 15 is connected to the planar waveguide lower metal base plate 5 of the excitation part, and the other end is connected to the planar waveguide lower metal base plate 9 of the matching load part. The thickness of the 1 / 4-ring coated medium 16 is h, the inner radius is R2, and the outer radius is R2+h. One end of the 1 / 4-ring coated medium 16 is connected to the inner filling medium 4 of the excitation part, and the other end is connected to the inner filling medium 8 of the matching load part. The connection parts are tangent.

[0039] Example 3:

[0040] This embodiment presents a typical planar discontinuous electromagnetic structure.

[0041] Figure 3a This describes the loading method of the step in the defective electromagnetic structure. The difference from Example 1 is that the step 17 is made of metal, symmetrical about the xoy plane, and positioned between the excitation part 1 and the matching load part 2 of the two-port surface wave transmission model. Specifically, it is located between the filling medium 4 of the excitation part and the filling medium 8 of the matching load part, protruding from the upper surface of the metal base plate 5 under the planar waveguide of the excitation part and the metal base plate 9 under the planar waveguide of the matching load part. The width of the step 17 in the y-axis direction is w, the height of the step 17 in the x-axis direction is d1, and the width in the z-axis direction is s1.

[0042] Figure 3b This describes the loading method for the gap in the defective electromagnetic structure. The difference from Example 1 is that the gap 18 is a concave cavity filled with a lossless dielectric, symmetrical about the xoy plane, and placed between the planar waveguide under-metal base plate 5 and the planar waveguide under-metal base plate 9 of the matching load portion. The dielectric constant of the lossless dielectric is μ, and its permeability is ε. The width of the gap 18 in the y-axis direction is w, its height in the x-axis direction is d2, and its width in the z-axis direction is s2.

[0043] In Examples 2 and 3, the energy of the discontinuous electromagnetic structure is fed into the feed port 6 of the excitation section, and the reflection parameter of the feed port 6 of the excitation section is S. 11 The matching load port 10 of the matching load section is connected to an external matching load, and the scattering parameter of the matching load port 10 of the matching load section is S. 21 scattering parameter S 21 This reflects the echo scattering component of surface waves by the electromagnetic discontinuity structure. Therefore, the scattering efficiency η of the two-port surface wave transmission model of the discontinuous electromagnetic structure in Examples 2 and 3 is:

[0044] η = 1 - (S) 11 ) 2 -(S 21 ) 2 -η0 (2)

[0045] The scattering efficiency η reflects the scattering efficiency of the electromagnetic discontinuity structure for surface waves. By changing the structural parameters R1 of the semi-circular annular convex surface 11, R2 of the quarter-circular ring 14, s1 and d1 of the step 17, and s2 and d2 of the gap 18, the discontinuous electromagnetic structure and the reflection parameter S can be obtained. 11 The relationship between the scattering efficiency η and the electromagnetic structure can guide the selection of parameters in stealth design.

[0046] The above description is merely a specific embodiment of the quantitative analysis method for surface wave electromagnetic scattering characteristics based on a two-port transmission model of the present invention. Commonly known technical solutions and / or characteristics involved in the embodiments are not described in detail here. It should be noted that the quantitative analysis method for surface wave electromagnetic scattering characteristics based on a two-port transmission model of the present invention only provides a framework for studying the surface wave scattering characteristics of electromagnetically discontinuous structures based on a two-port surface wave transmission model. For those skilled in the art, several modifications and improvements can be made without departing from the technical method of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A quantitative analysis method for surface wave electromagnetic scattering characteristics based on a two-port transmission model, characterized in that, The quantitative analysis method for surface wave electromagnetic scattering characteristics based on a two-port transmission model has an electromagnetic discontinuity structure. By loading the electromagnetic discontinuity structure, the scattering parameters of the port network are monitored. By changing the structural parameters of the electromagnetic discontinuity structure, the influence of the electromagnetic discontinuity structure on the electromagnetic scattering characteristics of surface waves is quantitatively studied. The baseline model of the dual-port transmission model is a centrally symmetric structure, consisting of a planar waveguide I, a surface waveguide, and a planar waveguide II from left to right. The lower wall of planar waveguide I, the base plate of the surface waveguide, and the lower wall of planar waveguide II share the same metal plate. The upper walls of planar waveguide I and planar waveguide II have a centrally symmetric tapered gradient structure. The interiors of planar waveguide I and planar waveguide II, as well as the surface of the base plate of the surface waveguide, are filled with a lossless dielectric. An excitation port is provided on one end face of planar waveguide I, and a matching load port is provided on the symmetrical end face of planar waveguide II. The electromagnetic discontinuity structure of the dual-port transmission model is to set a convex electromagnetic discontinuity structure or a concave electromagnetic discontinuity structure at the center of the reference model; or to set a step or gap at the center of the reference model, with the step or gap forming an electromagnetic defect. The loading method for the convex electromagnetic discontinuity structure is semi-circular ring loading, the loading method for the concave electromagnetic discontinuity structure is 1 / 4 circular ring loading, and the loading method for the steps or gaps is insertion into the interior of the two-port surface wave transmission model.

2. The quantitative analysis method for surface wave electromagnetic scattering characteristics based on a two-port transmission model according to claim 1, characterized in that, The quantitative analysis method for surface wave electromagnetic scattering characteristics includes the following steps: S10. Monitor the reflection parameters S of the excitation port of a two-port surface wave propagation model with electromagnetic discontinuities. 11 Reflection parameter S 11 The echo scattering components of the discontinuous electromagnetic structure were characterized. S20. Monitoring and Reflection Parameters S 11 The scattering parameter S of the corresponding matched load port 21 ; S30. Calculate scattering efficiency η =1-(S 11 ) 2 -(S 21 ) 2 ; S40. Define the two-port surface wave propagation model without electromagnetic discontinuities as the reference model. The scattering efficiency of the reference model is: η The scattering efficiency of the two-port surface wave propagation model with electromagnetic discontinuities is 0. η By comparing a two-port surface wave transmission model with an electromagnetic discontinuity structure with a benchmark model, the spatial leakage scattering capability of the electromagnetic discontinuity structure for surface waves is obtained.

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