Electromagnetic scattering parameter calculation method suitable for one-dimensional periodic structure

Abstract

The invention discloses an electromagnetic scattering parameter calculation method suitable for a one-dimensional periodic structure. The method comprises the steps of establishing a numerical calculation model of the one-dimensional periodic structure, setting boundary conditions, setting ports, performing simulation calculation according to the established model, and performing normalization processing. According to the calculation method, accurate numerical calculation of the scattering parameters of the artificial electromagnetic surface based on the one-dimensional periodic structure is realized, including the reflection coefficient and the transmission coefficient of the artificial electromagnetic surface, and a brand new method is provided for the design of the artificial electromagnetic surface. The calculation method disclosed by the invention can be simultaneously suitable for a two-dimensional periodic structure and a one-dimensional periodic structure of which one direction is an infinite periodic structure and the other orthogonal direction is a finite non-periodic structure, and a feasible design scheme is provided for loading application of an artificial electromagnetic surface in a finite space.

Description

Technical Field

[0001] The present invention relates to a method for designing an artificial electromagnetic surface, and particularly to a method for calculating electromagnetic scattering parameters applicable to a one-dimensional periodic structure. Background Art

[0002] The manipulation and regulation of spatial electromagnetic waves have always been a research hotspot in the field of information technology. By designing a specific artificial electromagnetic surface, flexible regulation of electromagnetic waves can be achieved in the frequency domain, polarization domain, and angular domain respectively. In the design of traditional artificial electromagnetic surfaces such as frequency selective surfaces, metamaterials, and metasurfaces, the artificial electromagnetic surface is usually considered as an infinitely large two-dimensional periodic structure in the plane. Therefore, during the design, only periodic boundary conditions need to be added around the unit and its unit structure is designed to obtain the electromagnetic scattering parameters of the two-dimensional periodic structure, including the reflection coefficient and transmission coefficient.

[0003] However, in many special application scenarios, due to the limited loading space of the artificial electromagnetic surface, it is impossible to place a huge artificial electromagnetic surface designed based on a two-dimensional periodic structure. Therefore, there is an urgent need to study a design method for an artificial electromagnetic surface based on a one-dimensional periodic structure, especially a method for calculating electromagnetic scattering parameters. A one-dimensional periodic structure is a periodic structure that is infinite in one direction and non-periodic and finite in the other orthogonal direction. Therefore, the same simulation design method as that for a two-dimensional periodic structure cannot be used, and there is an urgent need to propose a method for calculating electromagnetic scattering parameters for a one-dimensional periodic structure. Summary of the Invention

[0004] Object of the Invention: Aiming at the above-mentioned prior art, a method for calculating electromagnetic scattering parameters applicable to a one-dimensional periodic structure is proposed to achieve accurate calculation of the scattering parameters of an artificial electromagnetic surface based on a one-dimensional periodic structure.

[0005] Technical Solution: A method for calculating electromagnetic scattering parameters applicable to a one-dimensional periodic structure includes: 1) Establishing a numerical calculation model of a one-dimensional periodic structure: Constructing a numerical calculation model of a one-dimensional periodic structure with a large number of units in the y direction and a small number of units in the x direction, so it can be approximated as a one-dimensional periodic structure; 2) Setting boundary conditions: Setting the three directions of x, y, and z of the model as PML (perfectly matched layer) boundaries and leaving a gap at the edge; 3) Port settings: Two waveguide ports are used. The distance between the ports and the one-dimensional periodic structure is one-quarter wavelength of the lowest operating frequency. The port surfaces cover the entire one-dimensional periodic structure, and two PEC (Perfect Electric Conductor) boundaries, one above and one below, are set at each port to limit the modes generated by the ports, thereby exciting the TEM mode; 4) Simulation calculation: According to the established model, numerical calculations are respectively carried out using electromagnetic simulation software to obtain the scattering parameters under normal incidence and oblique incidence; 5) Normalization processing: Since the four sides of the model are PML boundaries, which will dissipate a part of the electromagnetic wave, it is necessary to normalize the calculated scattering parameter results; The scattering parameters include the transmission coefficient and the reflection coefficient. For the transmission coefficient, it is normalized using the calculation result of the air layer structure; For the reflection coefficient, it is normalized using the calculation result of the metal plate structure.

[0006] Further, in step 4), for oblique incidence setting: For incidence on the xoz plane, the one-dimensional periodic structure is rotated along the y-axis by θ 1 angle to achieve oblique incidence on the xoz plane; For incidence on the yoz plane, the one-dimensional periodic structure is rotated along the x-axis by θ 2 angles to achieve oblique incidence on the yoz plane.

[0007] Further, in step 5), the calculation results of the air layer structure and the metal plate structure are respectively obtained based on the numerical calculation models of the air layer structure and the metal plate structure, using the same simulation calculation method as in step 4).

[0008] Further, the numerical calculation model of the air layer structure is that in the numerical calculation model of the one-dimensional periodic structure, the one-dimensional periodic structure is replaced by an air layer structure of the same size.

[0009] Further, the numerical calculation model of the metal plate structure is that in the numerical calculation model of the one-dimensional periodic structure, the one-dimensional periodic structure is replaced by a metal plate structure of the same size.

[0010] Further, in step 1), a numerical calculation model of a one-dimensional periodic structure with more than 10 units in the y direction and 1 unit in the x direction is constructed.

[0011] Beneficial effects: 1. The present invention proposes a method for calculating the electromagnetic scattering parameters of a one-dimensional periodic structure, which realizes the accurate numerical calculation of the scattering parameters of an artificial electromagnetic surface based on a one-dimensional periodic structure, including the reflection coefficient and transmission coefficient of the artificial electromagnetic surface, and provides a brand-new method for the design of artificial electromagnetic surfaces.

[0012] 2. The present invention can be applied to two-dimensional periodic structures, as well as one-dimensional periodic structures with an infinite periodic structure in one direction and a finite aperiodic structure in the other orthogonal direction, expanding the degree of freedom of structure design and providing a feasible design scheme for the loading application of artificial electromagnetic surfaces in a limited space. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Schematic diagram of the numerical calculation model of the one-dimensional periodic structure provided by the embodiment of the present invention; Figure 2 Schematic diagram of the numerical calculation model of the air layer structure provided by the embodiment of the present invention; Figure 3 Transmission coefficient curve of the one-dimensional periodic structure provided by the embodiment of the present invention; In the figure, the reference numerals are: 100 - one-dimensional periodic structure, 200 - the first waveguide port of the one-dimensional periodic structure model, 201 - the PEC upper boundary of port 1 of the one-dimensional periodic structure model, 202 - the PEC lower boundary of port 1 of the one-dimensional periodic structure model, 300 - the second waveguide port of the one-dimensional periodic structure model, 301 - the PEC upper boundary of port 2 of the one-dimensional periodic structure model, 302 - the PEC lower boundary of port 2 of the one-dimensional periodic structure model, 400 - air layer structure, 500 - the first waveguide port of the air layer structure, 501 - the PEC upper boundary of port 1 of the air layer structure, 502 - the PEC lower boundary of port 1 of the air layer structure, 600 - the second waveguide port of the air layer structure, 601 - the PEC upper boundary of port 2 of the air layer structure, 602 - the PEC lower boundary of port 2 of the air layer structure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0014] The present invention will be further explained below with reference to the accompanying drawings.

[0015] An electromagnetic scattering parameter calculation method applicable to a one-dimensional periodic structure includes: a numerical calculation model of the one-dimensional periodic structure and a numerical calculation model of the air layer structure.

[0016] Figure 1Schematic diagram of the numerical calculation model for a one-dimensional periodic structure. The unit in the one-dimensional periodic structure 100 is a Jerusalem cross unit. The structure is arranged along the y direction, with 10 units in the y direction and 1 unit in the x direction. PML boundaries are set in the x, y, and z directions of the model, and gaps are left at the edges. At positions one-quarter wavelength away from the one-dimensional periodic structure 100 in the z direction, two waveguide ports, namely the first waveguide port 200 of the one-dimensional periodic structure model and the second waveguide port 300 of the one-dimensional periodic structure model, are set. The port planes can cover the entire structure, and the distances from the ports to the one-dimensional periodic structure are both one-quarter wavelength of the lowest operating frequency. At the first waveguide port 200 of the one-dimensional periodic structure model, a PEC (Perfect Electric Conductor) upper boundary 201 of port 1 of the one-dimensional periodic structure model and a PEC lower boundary 202 of port 1 of the one-dimensional periodic structure model are set. At the second waveguide port 300 of the one-dimensional periodic structure model, a PEC upper boundary 301 of port 2 of the one-dimensional periodic structure model and a PEC lower boundary 302 of port 2 of the one-dimensional periodic structure model are set. These PEC conductors can limit the modes generated at the ports, thereby exciting the TEM mode. The number of modes required for the ports needs to be calculated according to the port size.

[0017] Figure 2 Schematic diagram of the numerical calculation model for an air layer structure. The air layer structure 400 is arranged along the y direction, with the same size as the one-dimensional periodic structure 100. PML boundaries are set in the x, y, and z directions of the model, and gaps are left at the edges. At positions one-quarter wavelength away from the air layer structure 400 in the z direction, two waveguide ports, namely the first waveguide port 500 of the air layer structure and the second waveguide port 600 of the air layer structure, are set. The port planes can cover the entire structure. At the first waveguide port 500 of the air layer structure, a PEC upper boundary 501 of port 1 of the air layer structure and a PEC lower boundary 502 of port 1 of the air layer structure are set. At the second waveguide port 600 of the air layer structure, a PEC upper boundary 601 of port 2 of the air layer structure and a PEC lower boundary 602 of port 2 of the air layer structure are set. These PEC conductors can limit the modes generated at the ports, thereby exciting the TEM mode.

[0018] When calculating the scattering parameters of the one-dimensional periodic structure, based on the established numerical calculation model of the one-dimensional periodic structure, the electromagnetic simulation software is used to first calculate the results of normal incidence, and then calculate the 30° oblique incidence with respect to the xoz plane, which is achieved by rotating the one-dimensional periodic structure 30° along the y axis; then calculate the 30° oblique incidence with respect to the yoz plane, which is achieved by rotating the one-dimensional periodic structure 30° along the x axis.

[0019] Since the four sides of the structure are PML boundaries, which will dissipate a part of the electromagnetic wave, it is necessary to normalize the calculated scattering parameter results. The scattering parameters include the transmission coefficient and the reflection coefficient. For the transmission coefficient, it is normalized with the calculation result of the air layer structure; for the reflection coefficient, it is normalized with the calculation result of the metal plate structure. Specifically, based on the established numerical calculation model of the air layer structure, the calculation result of the air layer structure is obtained by using the same simulation calculation method. The numerical calculation model of the metal plate structure is Figure 2 In the structure, the air layer structure 400 is replaced by a metal plate of the same size as the one-dimensional periodic structure 100. On the basis of this model, the calculation result of this metal plate structure is obtained by using the same simulation calculation method.

[0020] Figure 3 It is the transmission coefficient curve of the one-dimensional periodic structure, and the transmission coefficient curves of the artificial electromagnetic surface designed based on the one-dimensional periodic structure at normal incidence, oblique incidence in the xoz plane, and oblique incidence in the yoz plane are given respectively, verifying the effectiveness of the present invention.

[0021] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for calculating electromagnetic scattering parameters applicable to one-dimensional periodic structures, characterized in that, Including: 1) Establishing a numerical calculation model of a one-dimensional periodic structure: constructing a numerical calculation model of a one-dimensional periodic structure with a large number of units in the y direction and a small number of units in the x direction; 2) Setting boundary conditions: setting the PML boundary for the x, y, and z directions of the model and leaving a gap at the edge; 3) Port setting: using two waveguide ports, the distance between the ports and the one-dimensional periodic structure is one-quarter wavelength of the lowest operating frequency, the port surface covers the entire one-dimensional periodic structure, and two PEC boundaries are set at each port to limit the modes generated by the ports, thereby exciting the TEM mode; 4) Simulation calculation: according to the established model, perform numerical calculations using electromagnetic simulation software respectively to obtain the scattering parameters under normal incidence and oblique incidence; 5) Normalization processing: since the PML boundary is set around the model, a part of the electromagnetic wave will be lost, so it is necessary to perform normalization processing on the calculated scattering parameter results; The scattering parameters include the transmission coefficient and the reflection coefficient. For the transmission coefficient, it is normalized with the calculation result of the air layer structure; For the reflection coefficient, it is normalized with the calculation result of the metal plate structure.

2. The electromagnetic scattering parameter calculation method applicable to one-dimensional periodic structures according to claim 1, characterized in that In step 4), the oblique incidence setting: for incidence on the xoz plane, rotate the one-dimensional periodic structure along the y-axis by θ 1 angle to achieve oblique incidence on the xoz plane; for incidence on the yoz plane, rotate the one-dimensional periodic structure along the x-axis by θ 2 angles to achieve oblique incidence on the yoz plane.

3. The electromagnetic scattering parameter calculation method applicable to one-dimensional periodic structures according to claim 1 or 2, characterized in that, In step 5), the calculation results of the air layer structure and the metal plate structure are obtained by using the same simulation calculation method as in step 4) based on the numerical calculation models of the air layer structure and the metal plate structure respectively.

4. The electromagnetic scattering parameter calculation method applicable to one-dimensional periodic structures according to claim 3, wherein The numerical calculation model of the air layer structure is that in the numerical calculation model of the one-dimensional periodic structure, the one-dimensional periodic structure is replaced by an air layer structure of the same size.

5. The electromagnetic scattering parameter calculation method applicable to one-dimensional periodic structures according to claim 3, characterized in that, The numerical calculation model of the metal plate structure is that in the numerical calculation model of the one-dimensional periodic structure, the one-dimensional periodic structure is replaced by a metal plate structure of the same size.

6. The method for calculating electromagnetic scattering parameters applicable to one-dimensional periodic structures according to any one of claims 1-5, characterized in that In step 1), construct a numerical calculation model of a one-dimensional periodic structure with more than 10 units in the y direction and 1 unit in the x direction.

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