A miniature dual-frequency microwave anechoic chamber based on spatially distributed ultrathin absorbing materials

Abstract

This invention relates to a miniature dual-frequency microwave anechoic chamber based on spatially distributed ultrathin absorbing materials. It includes a rigid cylindrical shell mounted on a support. An ultrathin dual-frequency electromagnetic wave absorbing unit and a transmitting antenna are attached to the inner wall of the rigid cylindrical shell. The ultrathin dual-frequency electromagnetic wave absorbing unit and the transmitting antenna are integrally formed, and the transmitting antenna is a microstrip patch antenna. This invention, through research on spatially distributed ultrathin electromagnetic wave absorbing materials, realizes a wavelength-scale miniature dual-frequency microwave anechoic chamber. The shape and size of the microwave anechoic chamber can be customized according to actual application requirements, and it is expected to be widely used in antenna measurement, microwave imaging, and other fields. This invention features low cost, simple construction, and portability.

Description

Technical Field

[0001] This invention relates to the field of microwave measurement experimental system technology, and in particular to a miniature dual-frequency microwave anechoic chamber based on spatially distributed ultrathin absorbing materials. Background Technology

[0002] With the widespread application of electronic information systems such as mobile communications, broadcasting, satellite communications, and the Internet of Things, the electromagnetic environment we live in is becoming increasingly complex. To provide equipment support for the development of communication technologies, simulation testing technologies, and electronic equipment, research on microwave anechoic chambers has attracted increasing attention.

[0003] Traditional microwave anechoic chambers are constructed by laying pyramidal absorbing materials on the inner walls of metal structures. Their high cost, large footprint, and immobility once built limit their application in practical engineering scenarios. Miniature microwave anechoic chambers, on the other hand, are small and portable, enabling convenient and rapid electromagnetic scattering measurements. They also play a crucial role in the evaluation and measurement of electrically small antennas and in electromagnetic scattering.

[0004] In recent years, electromagnetic wave absorbing surfaces based on artificial media have been extensively studied. Electromagnetic wave absorbing units relying on equivalent medium theory essentially depend on the high loss of their constitutive parameters in the electromagnetic resonance region, resulting in generally narrow operating bandwidths. Furthermore, the thickness of the electromagnetic wave absorbing unit and its corresponding absorption efficiency are often mutually constrained. Therefore, achieving near-perfect absorption performance for dual-frequency electromagnetic waves with ultrathin absorbing units is very difficult, and the construction of miniature dual-frequency microwave anechoic chambers also faces significant challenges. Summary of the Invention

[0005] To address the shortcomings of traditional microwave anechoic chambers, such as high cost, complex structure, and lack of portability, the present invention aims to provide a miniature dual-frequency microwave anechoic chamber based on spatially distributed ultrathin absorbing materials that achieves wavelength-scale performance, low cost, simple structure, and high portability.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a miniature dual-frequency microwave anechoic chamber based on spatially distributed ultrathin absorbing material, comprising a rigid cylindrical shell, the rigid cylindrical shell being mounted on a support, an ultrathin dual-frequency electromagnetic wave absorbing unit and a transmitting antenna being attached to the inner wall of the rigid cylindrical shell, the ultrathin dual-frequency electromagnetic wave absorbing unit and the transmitting antenna being integrally formed, and the transmitting antenna being a microstrip patch antenna.

[0007] The ultrathin dual-frequency electromagnetic wave absorbing unit consists of a metal ground plane, an intermediate dielectric layer, and a first upper metal pattern. The transmitting antenna consists of a metal ground plane, an intermediate dielectric layer, and a second upper metal pattern. The second upper metal pattern is composed of a microstrip line and multiple microstrip patches connected in series. The feed port is located at the end of the bottommost microstrip line. The transmitting antenna and the ultrathin dual-frequency electromagnetic wave absorbing unit share a metal ground plane and an intermediate dielectric layer.

[0008] The ultrathin dual-frequency electromagnetic wave absorbing unit has a thickness of 0.636 mm, a length of 6 mm, and a height of 8 mm. The two operating frequencies of the ultrathin dual-frequency electromagnetic wave absorbing unit are 5.12 GHz and 8.97 GHz, respectively.

[0009] The diameter of the rigid cylindrical outer shell is 345 mm.

[0010] The first upper metal pattern includes an upper I-shape and a lower I-shape. The lower end of the upper I-shape is the upper end of the lower I-shape. The upper I-shape is folded inward, and the lower I-shape is folded upward.

[0011] As can be seen from the above technical solution, the beneficial effects of the present invention are as follows: First, the present invention realizes a micro dual-frequency microwave anechoic chamber at the wavelength scale through the research on spatially distributed ultrathin electromagnetic wave absorbing materials. The shape and size of the microwave anechoic chamber can be customized according to actual application requirements, and it is expected to be widely used in antenna measurement, microwave imaging and other fields. Second, the present invention has the characteristics of low cost and simple structure, and is portable. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the structure of the present invention;

[0013] Figure 2 This is a schematic diagram of the transmitting antenna in this invention;

[0014] Figure 3 This is a schematic diagram of the far-field gain of the transmitting antenna in this invention;

[0015] Figure 4 This is an analysis diagram of the incident angle of electromagnetic waves radiated by the fixed-position transmitting antenna to any position on the inner wall of the dark room in this invention.

[0016] Figure 5 This is a schematic diagram of the structure of the ultrathin dual-frequency electromagnetic wave absorption unit in this invention;

[0017] Figure 6 This is a schematic diagram of the constitutive parameter inversion results of the ultrathin dual-frequency electromagnetic wave absorbing unit operating at a 20° oblique incidence angle according to the present invention;

[0018] Figure 7 This is a schematic diagram of the simulation results of the reflection parameters of the ultrathin dual-frequency electromagnetic wave absorption unit in this invention;

[0019] Figure 8 This is a schematic diagram of the full-wave simulation results of the present invention;

[0020] Figure 9 This is a schematic diagram of the transmitting antenna and the ultra-thin dual-frequency electromagnetic wave absorbing unit in this invention. Detailed Implementation

[0021] like Figure 1 , 9 As shown, a miniature dual-frequency microwave anechoic chamber based on spatially distributed ultrathin absorbing material includes a rigid cylindrical shell 1, which is mounted on a support. The support serves to fix the rigid cylindrical shell 1. The specific structure is not limited. An ultrathin dual-frequency electromagnetic wave absorbing unit 2 and a transmitting antenna 3 are attached to the inner wall of the rigid cylindrical shell 1. The ultrathin dual-frequency electromagnetic wave absorbing unit 2 and the transmitting antenna 3 are integrally formed. The transmitting antenna 3 is a microstrip patch antenna. Figure 1 In the diagram, transmitting antenna 3 is shown below; its specific structure is as follows: Figure 2 , 9 As shown.

[0022] like Figure 1 , 2 As shown in Figures 5 and 9, the ultrathin dual-frequency electromagnetic wave absorbing unit 2 consists of a metal ground plane 4, an intermediate dielectric layer 5, and a first upper metal pattern 6. The transmitting antenna 3 consists of a metal ground plane 4, an intermediate dielectric layer 5, and a second upper metal pattern. The second upper metal pattern is composed of a microstrip line 8 and multiple microstrip patches 7 connected in series. The feed port is located at the end of the lowest microstrip line 8, using a coaxial feed method. The transmitting antenna 3 and the ultrathin dual-frequency electromagnetic wave absorbing unit 2 share a metal ground plane 4 and an intermediate dielectric layer 5. In this invention, the ultrathin dual-frequency electromagnetic wave absorbing unit 2 uses a spatially distributed ultrathin absorbing material, where the intermediate dielectric layer 5 is an F4B flexible dielectric plate with a dielectric constant of 2.55 and a loss tangent of 0.003.

[0023] The diameter of the rigid cylindrical shell 1 is 345 mm. The thickness of the ultra-thin dual-frequency electromagnetic wave absorbing unit 2 is 0.636 mm, the length is 6 mm, and the height is 8 mm. The two operating frequencies of the ultra-thin dual-frequency electromagnetic wave absorbing unit 2 are 5.12 GHz and 8.97 GHz, respectively.

[0024] To reduce the operating frequency without increasing the size of the ultra-thin dual-frequency electromagnetic wave absorption unit 2, and to provide an adjustable range for the simulation optimization process, a folded structure was further introduced. The first upper metal pattern 6 includes an upper I-shape 6a and a lower I-shape 6b. The lower end of the upper I-shape 6a is the upper end of the lower I-shape 6b. The upper I-shape 6a is folded inward, and the lower I-shape 6b is folded upward.

[0025] By changing the dimensions of the second upper-layer metal pattern, transmitting antenna 3 can operate at different frequencies. Transmitting antenna 3 can radiate quasi-cylindrical electromagnetic waves, and the radiation pattern is significantly compressed in the height direction, avoiding scattering of electromagnetic waves at the edges of the darkened interior walls within a limited height. After simulation and optimization, the reflection parameter S11 at 5.12 GHz is -30.4 dB. The far-field gain diagram of the antenna is shown below. Figure 3 As shown.

[0026] For a given microwave anechoic chamber architecture, once the position of transmitting antenna 3 is fixed, the incident angle of the electromagnetic waves radiated by transmitting antenna 3 onto any position on the inner wall of the anechoic chamber is also fixed accordingly, such as... Figure 4 As shown. Based on this fixed incident angle relationship, by placing a series of ultra-thin dual-frequency electromagnetic wave absorbing units 2 operating at different incident angles at the corresponding incident angle positions, near-perfect absorption performance of the electromagnetic waves radiated by the transmitting antenna 3 can be achieved, thus completing the configuration of the microwave anechoic chamber. For different closed or semi-closed microwave anechoic chamber shapes and structures, the same method can be used to realize a miniature dual-frequency microwave anechoic chamber.

[0027] The ultrathin dual-frequency electromagnetic wave absorbing unit 2 can be realized using an artificial medium. For operation at dual frequencies, a unit structure possessing both upper I-shaped 6a and lower I-shaped 6 electromagnetic resonances is advantageous. When an electric field polarized along the z-axis is incident on the surface of the ultrathin dual-frequency electromagnetic wave absorbing unit 2, two electric resonances will be induced simultaneously; when a magnetic field polarized along the φ-axis is incident on the surface of the ultrathin dual-frequency electromagnetic wave absorbing unit 2, a magnetic resonance will be induced between the first upper metal pattern 6 and the metal ground plane 4. Using electromagnetic simulation software CST or HFSS, the electromagnetic resonances can be adjusted by regulating the dimensions of the first upper metal pattern 6, thereby realizing an electromagnetic wave absorbing unit capable of operating at two frequencies simultaneously. The constitutive parameter inversion results of the ultrathin dual-frequency electromagnetic wave absorbing unit 2 operating at a 20° oblique incidence angle are illustrated in the diagram. Figure 6 As shown, the constitutive parameters include dielectric constant and permeability. Observation revealed two electromagnetic resonances near 5.12 GHz and 8.97 GHz. At a frequency of 5.08 GHz, the dielectric constant and permeability are -0.13+i88.4 and -0.08+i45.7, respectively, and at a frequency of 8.97 GHz, the dielectric constant and permeability are -0.13+i116.7 and -0.08+i68.4, respectively, satisfying near-perfect absorption performance of electromagnetic waves.

[0028] Based on commercial electromagnetic simulation software, the ultrathin dual-frequency electromagnetic wave absorbing unit 2 was simulated and optimized. The simulation results of the reflection parameters of the absorbing unit at other oblique incidence angles are shown in [the table]. Figure 7After obtaining a series of ultrathin dual-frequency electromagnetic wave absorbing units 2 operating at different incident angles, based on the aforementioned micro-cylindrical microwave anechoic chamber construction scheme, a two-dimensional cylindrical anechoic chamber with a diameter of only 345 mm was completed using a line current source. The diameter of 345 mm, described in wavelength terms, is equal to 5.86 wavelengths, calculated based on 5.12 GHz. The full-wave simulation results at frequencies of 5.12 GHz and 8.97 GHz are as follows: Figure 8 As shown in Panel I and Panel II, it can be seen that the real distribution of the electric field at the two operating frequencies meets the expectations.

[0029] As can be seen from the above implementation examples, the present invention can design an ultra-thin electromagnetic wave absorbing surface for two independent frequencies. This dual-frequency electromagnetic wave absorbing surface can realize a wavelength-scale microwave anechoic chamber with a semi-enclosed or enclosed structure according to working requirements. The size of the microwave anechoic chamber can also be customized according to requirements.

[0030] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A miniature dual-frequency microwave anechoic chamber based on spatially distributed ultrathin absorbing materials, characterized in that: It includes a rigid cylindrical shell (1), which is mounted on a bracket. An ultra-thin dual-frequency electromagnetic wave absorbing unit (2) and a transmitting antenna (3) are attached to the inner wall of the rigid cylindrical shell (1). The ultra-thin dual-frequency electromagnetic wave absorbing unit (2) and the transmitting antenna (3) are integrally formed. The transmitting antenna (3) is a microstrip patch antenna. The ultrathin dual-frequency electromagnetic wave absorbing unit (2) is composed of a metal ground plane (4), an intermediate dielectric layer (5) and a first upper metal pattern (6). The transmitting antenna (3) is composed of a metal ground plane (4), an intermediate dielectric layer (5) and a second upper metal pattern. The second upper metal pattern is composed of a microstrip line (8) and multiple microstrip patches (7) connected in series. The feed port is located at the end of the bottom microstrip line (8). The transmitting antenna (3) and the ultrathin dual-frequency electromagnetic wave absorbing unit (2) share a metal ground plane (4) and an intermediate dielectric layer (5). The ultrathin dual-frequency electromagnetic wave absorbing unit (2) has a thickness of 0.636 mm, a length of 6 mm, and a height of 8 mm. The two working frequencies of the ultrathin dual-frequency electromagnetic wave absorbing unit (2) are 5.12 GHz and 8.97 GHz, respectively. The diameter of the rigid cylindrical shell (1) is 345 mm; The first upper metal pattern (6) includes an upper I-shape (6a) and a lower I-shape (6b). The lower end of the upper I-shape (6a) is the upper end of the lower I-shape (6b). The upper I-shape (6a) is folded inward, and the lower I-shape (6b) is folded upward. The ultrathin dual-frequency electromagnetic wave absorbing unit (2) uses spatially distributed ultrathin absorbing material, in which the intermediate dielectric layer (5) is an F4B flexible dielectric plate with a dielectric constant of 2.55 and a loss tangent of 0.

003. By changing the size of the second upper metal pattern, the transmitting antenna (3) can operate at different frequencies. When an electric field polarized along the z-axis is incident on the surface of the ultrathin dual-frequency electromagnetic wave absorbing unit (2), two electric resonances will be induced simultaneously. When a magnetic field polarized along the φ-axis is incident on the surface of the ultrathin dual-frequency electromagnetic wave absorbing unit (2), a magnetic resonance will be induced between the first upper metal pattern (6) and the metal ground plane (4). By adjusting the size of the first upper metal pattern (6) using electromagnetic simulation software CST or HFSS, the electromagnetic resonance can be adjusted, thereby realizing an electromagnetic wave absorbing unit that can operate at two frequencies simultaneously.

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