Small broadband microwave darkroom based on non-uniform artificial surface

Abstract

The invention relates to a small broadband microwave anechoic chamber based on a non-uniform artificial surface, the small broadband microwave anechoic chamber comprises a 36-polygon cylindrical shell, a broadband artificial medium wave-absorbing unit and a transmitting antenna, the broadband artificial medium wave-absorbing unit is attached to the inner wall of the 36-polygon cylindrical shell, edges are uniformly arranged on the 36-polygon cylindrical shell at intervals along the perimeter direction of the outer side of the 36-polygon cylindrical shell, and the transmitting antenna is arranged on the outer side of the 36-polygon cylindrical shell. A transmitting antenna is attached between every two adjacent edges, and the transmitting antennas are microstrip patch antennas. The broadband artificial medium wave-absorbing unit can effectively absorb 8-12 GHz electromagnetic waves incident at 0-70 degrees, has the advantages of multiple angles, broadband and high absorptivity, and provides a high-quality low-reflection test environment for scenes such as antenna measurement and microwave imaging which have strict requirements on the electromagnetic environment; the device is small in size, compact in structure and easy to install and integrate, the used materials are common materials, large-scale expansion is easy, and the device has the advantages of being passive, easy to machine and low in cost.

Description

Technical Field

[0001] The invention relates to the technical field of microwave measurement experimental systems, in particular to a small broadband microwave darkroom based on a non-uniform artificial surface. Background Art

[0002] A microwave anechoic chamber is a specialized facility that provides a low-reflection, low-interference environment for electromagnetic testing. It is widely used in fields such as antenna measurement, radar cross-section testing, and electromagnetic compatibility testing. Its core function is to simulate a free-space environment, absorbing electromagnetic waves through absorbing materials and reducing reflection from walls, floors, and ceilings, thereby ensuring the accuracy and reliability of test results. With the rapid development of high-tech industries such as modern wireless communications, aerospace, and defense, the demand for microwave anechoic chamber performance, particularly broadband absorption and miniaturization, has become increasingly urgent. Traditional microwave anechoic chambers rely on a full-length lining of pyramidal absorbing materials or foam absorbing layers, which absorb electromagnetic energy through dielectric loss. Their absorption performance depends on the thickness of the absorbing material, requiring larger space and limiting flexibility, making them difficult to use in applications with strict space constraints. The absorption performance of traditional absorbing materials decreases significantly as the angle of incidence increases.

[0003] With the development of technologies such as electromagnetic metamaterials and artificial surfaces, absorbing units based on artificial structures have gradually become a research hotspot. Electromagnetic wave absorbing units that rely on the equivalent medium theory are essentially realized by relying on the high loss of the constitutive parameters of their electromagnetic resonance region, and their operating frequency band is generally very narrow. In addition, the thickness of the electromagnetic wave absorbing unit and its corresponding absorption efficiency are often mutually restricted, and there is still room for improvement in broadband absorption and miniaturized integration. To achieve broadband absorption, multilayer metamaterials have been widely studied. However, multilayer metamaterial absorbers are relatively thick, difficult to manufacture, and have high production costs. Therefore, there is an urgent need for a new type of microwave anechoic chamber that can be miniaturized, easily manufactured, and has excellent absorption performance over a wide frequency band. Summary of the Invention

[0004] In order to solve the problems of large size and high cost of traditional microwave anechoic chambers, the purpose of the present invention is to provide a small broadband microwave anechoic chamber based on a non-uniform artificial surface with small size, compact structure, easy installation and integration, and low cost.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a small broadband microwave anechoic chamber based on a non-uniform artificial surface, comprising a 36-sided cylindrical shell, a broadband artificial medium absorbing unit, and a transmitting antenna. The broadband artificial medium absorbing unit is attached to the inner wall of the 36-sided cylindrical shell. The 36-sided cylindrical shell has edges evenly spaced along its outer circumference, and the transmitting antenna is attached between two adjacent edges. The transmitting antenna is a microstrip patch antenna.

[0006] The transmitting antenna consists of a first metal floor, a dielectric layer, a radiation patch and a feeding port. The dielectric layer is arranged above the first metal floor, and the radiation patch and the feeding port are arranged on the upper surface of the dielectric layer. The radiation patch is composed of a microstrip line and multiple microstrip patches in series. The transmitting antenna adopts a coaxial feeding method, and the feeding port is located at the end of the microstrip line.

[0007] The broadband artificial medium absorbing unit is composed of a second metal floor, a metal pattern, a thin film resistor, and a dielectric substrate. The dielectric substrate is in an I-shape and consists of a top plate, a bottom plate, and a vertical plate. The vertical plate is sandwiched between the top and bottom plates. The second metal floor is located on the bottom surface of the dielectric substrate, and the metal pattern is printed on the right side of the vertical plate. The metal pattern is roughly annular, with an opening on one side of the ring facing the second metal floor and two parallel lines extending inward. The two parallel lines are of the same length. A thin film resistor is welded between the two parallel lines, and the resistance of the thin film resistor is R.

[0008] The broadband artificial medium absorbing unit has an absorption performance of more than 87% when the incident angle of the electromagnetic wave is between 0° and 70°, achieving a near-perfect absorption effect of electromagnetic waves within a 4GHz bandwidth.

[0009] The broadband artificial medium absorbing unit has a thickness of 7.018 mm and a height of 8.2 mm.

[0010] The operating frequency range of the small broadband microwave anechoic chamber is 8GHz to 12GHz, with a relative bandwidth of 40%; the diameter of the small broadband microwave anechoic chamber is 468.6mm.

[0011] The material of the 36-sided cylindrical shell is organic glass.

[0012] The top and bottom plates are the same thickness, and the vertical plates are twice as thick as the top plate.

[0013] It can be seen from the above technical solution that the beneficial effects of the present invention are: First, the broadband artificial medium absorbing unit of the present invention can effectively absorb 8-12GHz electromagnetic waves with an incidence angle of 0° to 70°, and has the advantages of multi-angle, broadband, and high absorption rate, providing a high-quality low-reflection test environment for scenarios with strict requirements on the electromagnetic environment, such as antenna measurement and microwave imaging; Second, the present invention is small in size, compact in structure, and easy to install and integrate. This miniaturization feature enables it to adapt to application scenarios with limited space, and it is easy to install and integrate into existing test systems without the need for large-scale site modifications; Third, the size and operating frequency of the present invention can be customized according to actual application requirements. By adjusting parameters such as the thin film resistance value, metal pattern and dielectric substrate size of the broadband artificial medium absorbing unit, it can be adapted to different application requirements, and the manufacturing difficulty is low, and it is expected to be widely used in antenna measurement, microwave imaging, etc.; Fourth, the materials used in the present invention are all common materials, which are easy to expand on a large scale and have the advantages of being passive, easy to process and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of the present invention;

[0015] Figure 2 It is a structural schematic diagram of the broadband artificial medium absorbing unit in the present invention;

[0016] Figure 3 It is a schematic structural diagram of the metal pattern in the present invention;

[0017] Figure 4 This is a schematic diagram of the spatial arrangement of broadband artificial medium absorbing units in a small broadband microwave anechoic chamber;

[0018] Figure 5 、 6 7 and 8 are schematic diagrams of the structures of the transmitting antennas with operating frequencies of 8, 10, and 12 GHz respectively;

[0019] Figure 8 is the simulation result of the reflection parameters of the transmitting antenna;

[0020] Figure 9 The following are the simulation results of reflection parameters of broadband artificial medium absorbing units operating at incident angles of 0°, 10°, ..., and 70°.

[0021] Figure 10 These are the simulation results of the instantaneous distribution of the electric field in the present invention at operating frequencies of 8, 10, and 12 GHz. DETAILED DESCRIPTION

[0022] like Figure 1As shown, a small broadband microwave anechoic chamber based on a non-uniform artificial surface includes a 36-sided cylindrical shell 4, a broadband artificial medium absorbing unit 3, and a transmitting antenna 2. The broadband artificial medium absorbing unit 3 is attached to the inner wall of the 36-sided cylindrical shell 4. Ridges are evenly spaced along the outer perimeter of the 36-sided cylindrical shell 4, and a transmitting antenna 2, employing a microstrip patch 11, is attached between adjacent ridges. After the position of the transmitting antenna 2 is fixed, the incident angle of the electromagnetic waves radiated by the transmitting antenna 2 on each side of the chamber's inner wall is also fixed accordingly. Based on this fixed incident angle relationship, a series of broadband artificial medium absorbing units 3 operating at different incident angles are placed at corresponding incident angles to achieve near-perfect absorption of the electromagnetic waves radiated by the transmitting antenna 2, completing the configuration of the small broadband microwave anechoic chamber.

[0023] Transmitting antenna 2 comprises a first metal floor 14, a dielectric layer 13, a radiating patch, and a feed port 1. Dielectric layer 13 is positioned above first metal floor 14, and a radiating patch and feed port 1 are positioned on the upper surface of dielectric layer 13. The radiating patch is constructed from a microstrip line 12 and multiple microstrip patches 11 connected in series, enabling quasi-cylindrical electromagnetic wave radiation, with the radiation pattern significantly compressed in the height direction. Transmitting antenna 2 utilizes coaxial feeding, with feed port 1 located at the end of microstrip line 12.

[0024] With the transmitting antenna 2 positioned, the incident angles of the electromagnetic waves radiated by the transmitting antenna 2 on the other 35 inner surface surfaces are also fixed accordingly. Based on this fixed incidence angle relationship, a series of broadband artificial medium absorbing units 3 operating at different incidence angles are placed at corresponding incidence angle positions. Adjacent broadband artificial medium absorbing units 3 are closely spaced, leaving no gaps.

[0025] like Figure 2 As shown, the broadband artificial medium absorbing unit 3 is composed of a second metal floor 10, a metal pattern 9, a thin film resistor, and a dielectric substrate 5. The dielectric substrate 5 is in an I-shape and consists of a top plate 6, a bottom plate 8, and a vertical plate 7. The vertical plate 7 is sandwiched between the top plate 6 and the bottom plate 8. The top plate 6 and the bottom plate 8 have the same thickness, and the vertical plate 7 is twice as thick as the top plate 6. The depth g of the top plate 6, the bottom plate 8, and the vertical plate 7 is 7 mm. The thickness 2d of the vertical plate 7 is 0.762 mm, and the thickness d of the top plate 6 and the bottom plate 8 is 0.381 mm. The second metal floor 10 is located on the bottom surface of the dielectric substrate 5, and the metal pattern 9 is printed on the right side of the vertical plate 7; as shown in FIG. Figure 3 As shown, the metal pattern 9 is roughly annular with a thickness of 0.018 mm. The ring opens on one side facing the second metal floor 10 and extends two parallel lines inward. The two parallel lines have the same length. A thin film resistor is welded between the two parallel lines. The resistance of the thin film resistor is R.

[0026] The broadband artificial medium absorbing unit 3 exhibits an absorption performance exceeding 87% when the electromagnetic wave incident angle is between 0° and 70°, achieving near-perfect electromagnetic wave absorption within a 4GHz bandwidth. Simulations optimize the resistance of the thin film resistor of the broadband artificial medium absorbing unit 3, the dimensions of the metal pattern 9, and the dimensions of the dielectric substrate 5, resulting in broadband artificial medium absorbing units 3 operating at different electromagnetic wave incident angles. The unit operating at a 0° electromagnetic wave incident angle is referred to as a 0° broadband artificial medium absorbing unit. Similarly, the units operating at 5°, 10°, ..., and 70° electromagnetic wave incident angles are referred to as 5°, 10°, ..., and 70° broadband artificial medium absorbing units. The width f of the 0°, 5°, ..., and 50° broadband artificial medium absorbing units is 8.2mm, while the width f of the 55°, 60°, 65°, and 70° broadband artificial medium absorbing units is 6.83mm.

[0027] The broadband artificial medium absorbing unit 3 has a thickness of 7.018 mm and a height of 8.2 mm. The operating frequency range of the small broadband microwave anechoic chamber is 8 GHz to 12 GHz, with a relative bandwidth of 40%. The diameter of the small broadband microwave anechoic chamber is 468.6 mm. The size and operating frequency of the small broadband microwave anechoic chamber can be customized according to actual application requirements, and it is expected to be widely used in fields such as antenna measurement and microwave imaging.

[0028] The material of the 36-sided cylindrical shell 4 is organic glass. The 36-sided cylindrical shell 4 plays the role of supporting the small broadband microwave darkroom.

[0029] By adjusting the resistance of the thin-film resistor, the dimensions of the metal pattern 9, and the dimensional parameters of the dielectric substrate 5, a broadband artificial medium absorbing unit 3 operating at different incident angles is obtained. The dimensional parameters of the metal pattern 9 that require adjustment include r, a, b, and c, where r is the inner diameter of the ring, a is the distance between the two parallel lines, the width of the ring and the width of the two parallel lines are both b, and c is the length of the two parallel lines. The dimensional parameters of the dielectric substrate 5 that require adjustment include e and f, where e is the height of the dielectric substrate 5 and f is the width of the dielectric substrate 5. The dimensional parameters of the broadband artificial medium absorbing unit 3 operating at different incident angles are shown in the following table, where θ is the incident angle of the electromagnetic wave.

[0030] Table 1 Dimensional parameters of broadband artificial medium absorbing units operating at different incident angles

[0031] Parameter θ R / Ω r / mm a / mm b / mm c / mm e / mm f / mm 0° 75 2.9 0.2 0.3 3.6 8.2 8.2 5° 75 2.9 0.2 0.3 3.6 8.2 8.2 10° 75 2.9 0.2 0.3 3.6 8.2 8.2 15° 75 2.9 0.2 0.3 3.6 8.2 8.2 20° 75 2.75 0.2 0.35 3.6 8.2 8.2 25° 75 2.75 0.2 0.35 3.7 8.2 8.2 30° 75 2.75 0.2 0.35 3.7 8.2 8.2 35° 75 2.75 0.2 0.35 3.6 8.2 8.2 40° 75 2.55 0.24 0.5 3.35 8.2 8.2 45° 75 2.3 0.26 0.75 2.9 8.2 8.2 50° 75 2.3 0.24 0.8 2.94 8.2 8.2 55° 75 2.05 0.2 0.95 2.85 8.2 6.83 60° 75 1.98 0.2 1.02 2.65 8.2 6.83 65° 75 2.05 0.2 0.95 2.9 8.2 6.83 70° 75 2.03 0.2 0.77 3 8.2 6.83

[0032] like Figure 4As shown, the transmitting antenna 2 is attached to a 36-sided cylindrical housing 4. Once the position of the transmitting antenna 2 is fixed, the incident angles of the electromagnetic waves radiated by the transmitting antenna 2 on the other inner sides of the darkroom are also fixed accordingly. The inner side surface with an electromagnetic wave incident angle of 0° is referred to as the 0° inner side surface, and the inner side surfaces with electromagnetic wave incident angles of 5°, 10°, ..., and 70° are referred to as the 5°, 10°, ..., and 70° inner sides. Based on this fixed incidence angle relationship, a series of broadband artificial medium absorbing units 3 operating at different incidence angles are placed at corresponding incidence angle positions. Therefore, the inner side surface of the 36-sided cylindrical housing 4 directly facing the transmitting antenna 2 is the 0° incident position for electromagnetic waves, where the 0° broadband artificial medium absorbing unit is attached. The inner side surface clockwise adjacent to the 0° inner side surface is the 5° incident position for electromagnetic waves, where the 5° broadband artificial medium absorbing unit should be placed. Similarly, the inner side surfaces adjacent to the 5° inner side surface in the clockwise direction should be placed with 10°, 15°, ..., and 70° broadband artificial medium absorbing units, respectively. 70° broadband artificial medium absorbing units should also be placed on the three inner side surfaces from the inner side surface of the 70° broadband artificial medium absorbing unit to the inner side surface of the transmitting antenna 2. The placement of the 17 inner side surfaces from the 0° inner side surface counterclockwise to the inner side surface of the antenna is similar to that from the clockwise direction to the inner side surface of the transmitting antenna 2. Adjacent broadband artificial medium absorbing units 3 should be closely spaced, leaving no gaps. The width of each inner side surface is 41 mm. The width f of the dielectric substrate 5 of the 0°, 5°, ..., 50° broadband artificial medium absorbing units is 8.2 mm. Five 0°, 5°, ..., 50° broadband artificial medium absorbing units are closely arranged on one inner side surface. The width f of the dielectric substrate 5 of the 55°, 60°, 65°, and 70° broadband artificial medium absorbing units is 6.83 mm. Six 55°, 60°, 65°, and 70° broadband artificial medium absorbing units are closely arranged on one inner side surface.

[0033] The 8, 10, and 12 GHz transmitting antenna structures are as follows: Figure 5 、 Figure 6 、 Figure 7 As shown, the simulation results of the reflection parameters of the transmitting antenna 2 are as follows Figure 8 As shown in the figure, the sizes of the microstrip lines and microstrip patches of the transmitting antennas at different operating frequencies are different; the reflection parameter of the 8GHz antenna at the operating frequency is -25.1dB, the reflection parameter of the 10GHz transmitting antenna at the operating frequency reaches -25.8dB, and the reflection parameter of the 12GHz transmitting antenna at the operating frequency reaches -25.9dB.

[0034] In order to verify the absorbing performance of broadband artificial medium absorbing unit 3 to electromagnetic waves with different incident angles, Figure 9 As shown in Figure 1, based on the electromagnetic simulation software CST, the reflection parameters of the broadband artificial medium absorbing unit working at electromagnetic wave incident angles of 0°, 10°, ..., 70° are simulated. Figure 9It can be seen that under the incidence of 8-12 GHz electromagnetic waves, the broadband artificial medium absorbing unit 3 has an absorption performance of more than 87% when the electromagnetic wave incident angle is between 0° and 70°, achieving a near-perfect absorption effect of electromagnetic waves within the 4 GHz bandwidth range.

[0035] In order to verify the working performance of a small broadband microwave anechoic chamber based on non-uniform artificial surfaces, such as Figure 10 As shown in the figure, based on the electromagnetic simulation software COMSOL, the instantaneous distribution of the electric field in a small broadband microwave darkroom at operating frequencies of 8, 10, and 12 GHz is simulated respectively. Figure 10 As can be seen in the figure, there is no obvious standing wave effect. The simulation results prove that the small broadband microwave anechoic chamber based on the non-uniform artificial surface has good working performance in the range of 8-12 GHz.

[0036] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions merely illustrate the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A small broadband microwave anechoic chamber based on a non-uniform artificial surface, characterized by: The invention comprises a 36-sided cylindrical shell (4), a broadband artificial medium absorbing unit (3) and a transmitting antenna (2), wherein the broadband artificial medium absorbing unit (3) is attached to the inner wall of the 36-sided cylindrical shell (4), and the 36-sided cylindrical shell (4) has edges evenly spaced along the outer perimeter thereof, and the transmitting antenna (2) is attached between two adjacent edges, and the transmitting antenna (2) is a microstrip patch (11) antenna.

2. The small broadband microwave anechoic chamber based on a non-uniform artificial surface according to claim 1, characterized in that: The transmitting antenna (2) is composed of a first metal floor (14), a dielectric layer (13), a radiation patch, and a feeding port (1); the dielectric layer (13) is arranged upward from the first metal floor (14); the radiation patch and the feeding port (1) are arranged on the upper surface of the dielectric layer (13); the radiation patch is composed of a microstrip line (12) and a plurality of microstrip patches (11) connected in series; the transmitting antenna (2) adopts a coaxial feeding method, and the feeding port (1) is located at the end of the microstrip line (12).

3. The small broadband microwave anechoic chamber based on a non-uniform artificial surface according to claim 1, characterized in that: The broadband artificial medium absorbing unit (3) is composed of a second metal floor (10), a metal pattern (9), a thin film resistor and a dielectric substrate (5). The dielectric substrate (5) is in an I-shape and is composed of a top plate (6), a bottom plate (8) and a vertical plate (7). The vertical plate (7) is sandwiched between the top plate (6) and the bottom plate (8). The second metal floor (10) is located on the bottom surface of the dielectric substrate (5). The metal pattern (9) is printed on the right side of the vertical plate (7). The metal pattern (9) is roughly in a circular ring shape. The circular ring opens toward one side of the second metal floor (10) and extends two parallel lines inward. The two parallel lines have the same length. A thin film resistor is welded between the two parallel lines. The resistance value of the thin film resistor is R.

4. The small broadband microwave anechoic chamber based on a non-uniform artificial surface according to claim 1, characterized in that: The broadband artificial medium absorbing unit (3) has an absorption performance of more than 87% when the incident angle of the electromagnetic wave is between 0° and 70°, and achieves a nearly perfect absorption effect of the electromagnetic wave within a 4 GHz bandwidth.

5. The small broadband microwave anechoic chamber based on a non-uniform artificial surface according to claim 1, characterized in that: The broadband artificial medium absorbing unit (3) has a thickness of 7.018 mm and a height of 8.2 mm.

6. The small broadband microwave anechoic chamber based on a non-uniform artificial surface according to claim 1, characterized in that: The operating frequency range of the small broadband microwave anechoic chamber is 8GHz to 12GHz, with a relative bandwidth of 40%; the diameter of the small broadband microwave anechoic chamber is 468.6mm.

7. The small broadband microwave anechoic chamber based on a non-uniform artificial surface according to claim 1, characterized in that: The material of the 36-sided cylindrical shell (4) is organic glass.

8. The small broadband microwave anechoic chamber based on a non-uniform artificial surface according to claim 3, characterized in that: The top plate (6) and the bottom plate (8) have the same thickness, and the vertical plate (7) has a thickness twice that of the top plate (6).

Images