Band elimination frequency selective surface based on impedance conversion and comprehensive design method thereof

Abstract

The invention discloses a band-stop frequency selective surface based on impedance transformation and a comprehensive design method thereof, the band-stop frequency selective surface adopts a three-dimensional laminated slot line structure, a periodic array is formed by a plurality of laminated slot line units, each laminated slot line unit is composed of two layers and / or three layers, the first layer is a metal layer A, the second layer is a dielectric substrate, and the third layer is a metal layer B; the third layer is selectively arranged and is a metal layer B parallel to the first layer, and the first to second layers and / or the first to third layers are sequentially laminated together. In the invention, the designed band-stop frequency selective surface can be mapped and modeled by two parts of an equivalent impedance conversion network and a band-stop network, and has the advantages of compact unit structure, high selectivity, narrow stop band, good out-of-band passband performance, comprehensive design and the like; the method is suitable for the fields of radars, antenna systems, satellite communication, electromagnetic shielding and the like with narrowband band-stop requirements.

Description

Technical Field

[0001] The invention relates to the field of electromagnetic field and microwave technology, in particular to a band-stop frequency selective surface based on impedance transformation and a comprehensive design method thereof. Background Art

[0002] Frequency selective surfaces are array structures composed of several units arranged in a periodic or quasi-periodic manner, and have the characteristics of selecting and regulating electromagnetic waves in space. With the rapid development of wireless communication and radio frequency technology, band-stop frequency selective surfaces have been widely used in radar, antenna systems, satellite communications, electromagnetic shielding and other fields. Band-stop frequency selective surfaces can effectively achieve frequency band isolation and interference suppression by suppressing the propagation of electromagnetic waves in a specific frequency band, thereby improving the signal quality of the system. However, existing design methods still face many technical difficulties in achieving high-performance band-stop response, mainly including poor stopband selectivity, difficulty in meeting narrowband requirements, and lack of comprehensive design methods.

[0003] The traditional two-dimensional frequency selective surface adopts patch structure design, and forms resonant units (such as open loop, ring resonator, cross resonator, etc.) by designing the geometric shapes of different metal iron sheets, and adjusting their size and layout parameters to control the resonant frequency, thereby achieving band-stop response. For example, slotted or periodic metal structures are loaded to introduce the resonance phenomenon of electromagnetic waves. However, this method has high accuracy in low frequency bands and is sensitive to changes in geometric dimensions, making it difficult to meet high-frequency and high-precision requirements.

[0004] The existing three-dimensional frequency selective surface can also achieve the band-stop effect by loading an open or short-circuited resonant structure in the stacked microstrip line structure. This frequency selective surface has the characteristics of good frequency selectivity and simple processing. However, the design of this method is relatively complex and it is difficult to meet the needs of comprehensive design.

[0005] In general, in the current design of two-dimensional and three-dimensional frequency selective surfaces, how to explore the comprehensively designed band-stop frequency selective surfaces while taking into account narrowband and high in-band selectivity is a technical problem that needs to be solved urgently. Summary of the invention

[0006] The present invention provides a band-stop frequency selective surface based on impedance transformation with high selectivity and good full-band passband and a comprehensive design method thereof, which can solve at least one of the above technical problems.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions: The impedance transformation-based band-stop frequency selective surface adopts a three-dimensional stacked slot line structure, and is composed of a periodic array of multiple stacked slot line units. Each of the stacked slot line units is composed of two layers and / or three layers, including: the first layer is a metal layer A, the second layer is a dielectric substrate, and the third layer can be optionally set to be a metal layer B parallel to the first layer. The first to second layers and / or the first to third layers are pressed together in sequence.

[0008] Furthermore, the first metal layer A is composed of cascaded metal slotted lines and series-connected short-circuit slotted lines; For the third-order band-stop frequency selective surface, the metal slotted lines include a first metal slotted line, a second metal slotted line, a third metal slotted line and a fourth metal slotted line, and the short-circuit slot lines include a first short-circuit slot line, a second short-circuit slot line and a third short-circuit slot line; The first metal slotted line and the second metal slotted line are symmetrically arranged and are uniform transmission lines respectively, and the two form an impedance transformation network; The third metal slotted line and the fourth metal slotted line are symmetrically arranged and are uniform transmission lines respectively. The second short-circuit slot line is an inverted "T" structure. The first short-circuit slot line and the third short-circuit slot line are respectively rotated toward the first metal slotted line and the second metal slotted line, and are symmetrically arranged on both sides of the second short-circuit slot line. The first short-circuit slot line, the second short-circuit slot line and the third short-circuit slot line are respectively series short-circuit branches. The third metal slotted line, the fourth metal slotted line, the first short-circuit slot line, the second short-circuit slot line and the third short-circuit slot line form a short-circuit branch type band-stop network.

[0009] Furthermore, in the short-circuit branch type band-stop network, the physical structure of the short-circuit branch is realized by the short-circuit slot line, and the impedance of the short-circuit slot line increases with the increase of its own width.

[0010] Furthermore, the third metal layer B can be optionally set as needed, parallel to the first metal layer A, and includes a first metal strip, a second metal strip and a third metal strip, and the first metal strip, the second metal strip and the third metal strip are parallel to each other and correspond to the first short-circuit groove line, the second short-circuit groove line and the third short-circuit groove line respectively.

[0011] The comprehensive design method of the band-stop frequency selective surface based on impedance transformation is implemented by using the band-stop frequency selective surface based on impedance transformation, and comprises the following steps: S1. According to the stopband index requirements of the required stopband frequency selection surface, select the short-circuit branch type stopband network of appropriate order and its port impedance; S2. For a short-circuit branch-type band-stop network of known order, the band-stop transformation function or appropriate characteristic function can be used to establish the analytical relationship between the band-stop index and each component in the band-stop network, and solve the parameters of each component; S3. According to the impedance transformation theory, the port impedance of the selected band-stop network is transformed with the free space wave impedance to determine the parameters of each component in the impedance transformation network when the impedance matching is achieved within the stopband frequency range; S4. The selected band-stop network and the determined impedance transformation network are mapped respectively to form a three-dimensional stacked slot-line band-stop frequency selective surface unit, and finally the actual physical structure of the band-stop frequency selective surface is determined, and a physical sample can be produced using a printed circuit board process.

[0012] Furthermore, the factors for the comprehensive design of the band-stop frequency response in the band-stop network include at least: stop-band center frequency, stop-band bandwidth and pass-band return loss.

[0013] Furthermore, the band-stop network adopts a short-circuit branch-type band-stop circuit topology, and the characteristic functions that can be used include at least an optimal band-stop characteristic function.

[0014] Furthermore, the physical structure of the band-stop network is realized by a three-dimensional stacked slot-line structure, and the band-stop network includes series-connected short-circuit branches and cascaded uniform transmission lines, the short-circuit branches serve as band-stop resonators, and the uniform transmission lines serve as coupling structures / resonators, both of which operate at the center frequency of the stop band; In the three-dimensional stacked slot line structure, the series short-circuit slot lines correspond to the series short-circuit branches in the band-stop network, and the cascaded metal slot lines correspond to the cascaded uniform transmission lines in the band-stop network.

[0015] Furthermore, the band-stop frequency selective surface is used as a spatial electromagnetic wave amplitude control device, and the impedance transformation network of its input and output ports is used to realize the impedance transformation between the free space wave and the band-stop network, while widely solving the problem of the spatial electromagnetic wave keeping the stopband performance unchanged within the amplitude comprehensive design band, and ensuring good low-reflection bandpass performance outside the stopband; The impedance transformation network uses a single-section or multi-section cascaded uniform transmission line as a single-section or multi-section impedance transformer, all of which work at the stopband center frequency; In the three-dimensional stacked slot line structure, a single section or multiple sections of cascaded metal slotted lines correspond to a single section or multiple sections of cascaded uniform transmission lines in an impedance transformation network.

[0016] Furthermore, the three-dimensional stacked slot-line type band-stop frequency selective surface has the ability to convert spatial electromagnetic waves and guided wave modes, converting complex spatial electromagnetic waves into guided waves that are easy to control, thereby performing a comprehensive design of "field-to-path" conversion from the perspective of "path", and directly mapping the distributed transmission line model to realize the three-dimensional stacked slot-line structure to improve design efficiency and accuracy.

[0017] The beneficial effects of the present invention are embodied in: 1. The present invention provides a comprehensive design method for realizing band-stop response in a three-dimensional stacked slot-line structure, which is comprehensively designed based on the stop-band center frequency, stop-band bandwidth and pass-band return loss, and provides an effective narrow-band band-stop frequency selection surface design scheme, which can achieve a 3dB bandwidth of less than 10%, including an effective impedance transformation network design scheme, so that the stop-band has high selectivity and good full-band passband. At the same time, the cross-sectional thickness of the band-stop frequency selection surface is small, which is about one wavelength of the center frequency.

[0018] 2. Compared with the design of traditional two-dimensional band-stop frequency selective surfaces, the three-dimensional band-stop frequency selective surface of the present invention has the ability to convert spatial electromagnetic waves and guided wave modes, and can convert complex spatial electromagnetic waves into guided waves that are easy to control, thereby performing a comprehensive design of "field-to-path" conversion from the perspective of "path", and directly mapping the distributed transmission line model to realize the three-dimensional stacked slot line structure, thereby improving its design efficiency and accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are used to provide further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0020] Figure 1 It is a schematic diagram of the three-dimensional structure of the band-stop frequency selective surface according to the first embodiment of the present invention.

[0021] Figure 2 It is a schematic diagram of the unit structure of the band-stop frequency selective surface of the first embodiment of the present invention in a three-dimensional space coordinate system.

[0022] Figure 3 It is a front view of the band-stop frequency selective surface of the first embodiment of the present invention.

[0023] Figure 4 It is a schematic diagram of the dimensions of a band-stop frequency selective surface according to an embodiment of the present invention.

[0024] Figure 5 It is a front view of the band-stop frequency selective surface of the second embodiment of the present invention.

[0025] Figure 6 It is a rear view of the band-stop frequency selective surface according to the second embodiment of the present invention.

[0026] Figure 7 It is a schematic diagram of the front structural dimensions of the band-stop frequency selective surface according to the second embodiment of the present invention.

[0027] Figure 8 It is a schematic diagram of the reverse structural dimensions of the band-stop frequency selective surface according to the second embodiment of the present invention.

[0028] Fig. 9 It is an overall flow chart of the comprehensive design method of the band-stop frequency selective surface according to an embodiment of the present invention.

[0029] Fig.10 It is a circuit topology diagram of the comprehensive design method of the band-stop frequency selective surface according to the embodiment of the present invention.

[0030] Fig.11 is a typical S parameter curve diagram of an embodiment of the present invention.

[0031] Fig.12 It is an S parameter curve diagram of the full-wave electromagnetic simulation of the band-stop frequency selective surface according to the first embodiment of the present invention.

[0032] Fig.13 It is an S parameter curve diagram of the full-wave electromagnetic simulation of the band-stop frequency selective surface according to the second embodiment of the present invention.

[0033] Fig.14 It is a structural block diagram of a computer device according to an embodiment of the present invention.

[0034] The markings of the components in the accompanying drawings are: In the first embodiment: 1. dielectric substrate; 2. metal layer A; 3. first metal slotted line; 4. third metal slotted line; 5. fourth metal slotted line; 6. second metal slotted line; 7. first short-circuit slot line; 8. second short-circuit slot line; 9. third short-circuit slot line; In the second embodiment: 10. Dielectric substrate; 11. First metal slotted line; 12. Third metal slotted line; 13. Fourth metal slotted line; 14. Second metal slotted line; 15. First short-circuit slot line; 16. Second short-circuit slot line; 17. Third short-circuit slot line; 18. Metal layer A; 19. Metal layer B; 20. First metal strip; 21. Second metal strip; 22. Third metal strip. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0036] It should be noted that if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, "multiple" refers to more than two.

[0037] See also Figure 1-Figure 4 Embodiment 1 of the present invention provides a band-stop frequency selective surface based on impedance transformation, which has design indicators of a center frequency of 5 GHz and a 3 dB bandwidth of 4%. A three-dimensional stacked slot line structure is adopted, and a periodic array is formed by a plurality of stacked slot line units through equidistant air gaps. Each of the stacked slot line units is composed of two layers, including: a first layer is a metal layer A2, and a second layer is a dielectric substrate 1, and the dielectric substrate 1 is closely attached to the metal layer A2.

[0038] In the first embodiment, the provided band-stop frequency selective surface is of three-order, and the first metal layer A2 is composed of cascaded metal slotted lines and series-connected short-circuited slotted lines, wherein: The metal slotted wires include a first metal slotted wire 3, a second metal slotted wire 6, a third metal slotted wire 4 and a fourth metal slotted wire 5, and the short-circuit slot wires include a first short-circuit slot wire 7, a second short-circuit slot wire 8 and a third short-circuit slot wire 9; The first metal slotted line 3 and the second metal slotted line 6 are symmetrically arranged and are uniform transmission lines respectively, and the two form an impedance transformation network; The third metal slotted line 4 and the fourth metal slotted line 5 are symmetrically arranged and are respectively uniform transmission lines. The second short-circuit slot line 8 is an inverted "T" structure. The first short-circuit slot line 7 and the third short-circuit slot line 9 are respectively rotated toward the first metal slotted line 3 and the second metal slotted line 6, and are symmetrically arranged on both sides of the second short-circuit slot line 8. The first short-circuit slot line 7, the second short-circuit slot line 8 and the third short-circuit slot line 9 are respectively series short-circuit branches. The third metal slotted line 4, the fourth metal slotted line 5, the first short-circuit slot line 7, the second short-circuit slot line 8 and the third short-circuit slot line 9 form a short-circuit branch type band-stop network.

[0039] Combination Figure 2 and Figure 4 The physical dimensions of the band-stop frequency selective surface are marked, and its design parameters are as follows: P x =15mm, P y =15mm, d 1=0.508mm, d 2 = 7.246 mm, W 1=7.8mm, W 2=6.7mm, W 3=0.8mm, W 4=0.6mm, W 5=1mm, L 1=14mm, L 2 = 13.84 mm, L 3=10.31mm, L 4=5mm, L 5=5.9mm.

[0040] In the first embodiment, in the short-circuit branch type band-stop network, the physical structure of the short-circuit branch is implemented by the short-circuit slot line, and the impedance of the short-circuit slot line increases with the increase of its own width.

[0041] The short-circuit branch-type band-stop network is combined with the impedance transformation network to form the band-stop frequency selection surface of the present invention. The band-stop frequency selection surface is bilaterally symmetrical in design. The rotation of the first short-circuit slot line 7 and the third short-circuit slot line 9, as well as the bending of the second short-circuit slot line 8, is intended to reduce y In order to avoid the grating lobe effect of the band-stop frequency selective surface, in the three-dimensional space coordinate system, y , x The stacked slot line unit size in the direction P y , Px Less than or equal to one quarter of the wavelength corresponding to the center frequency of 5 GHz, usually P y and P x They are equal in size, and they jointly affect the free space wave impedance and the stacked slot line impedance.

[0042] To summarize, the band-stop frequency selective surface of the first embodiment of the present invention adopts a three-dimensional stacked slot line structure, which is mapped and modeled by two parts: an equivalent impedance transformation network and a band-stop network, thereby achieving high selectivity within the stopband operating frequency band and good passband performance outside the operating frequency band.

[0043] See also Figure 5-Figure 8 Embodiment 2 of the present invention further provides a band-stop frequency selective surface based on impedance transformation, which has design indicators of a center frequency of 5 GHz and a 3 dB bandwidth of 4%. A three-dimensional stacked slot line structure is adopted, and a plurality of stacked slot line units are connected through equidistant air gaps to form a periodic array, and each of the stacked slot line units is composed of three layers, including: a first layer is a metal layer A18, a second layer is a dielectric substrate 10, and a third layer is a metal layer B19. The third layer is parallel to and corresponds to the first layer, and the first to third layers are pressed together in sequence.

[0044] In the second embodiment, the provided band-stop frequency selective surface is of three-order, and the first metal layer A18 is composed of cascaded metal slotted lines and series-connected short-circuited slotted lines, wherein: The metal slotted wires include a first metal slotted wire 11, a second metal slotted wire 14, a third metal slotted wire 12, and a fourth metal slotted wire 13, and the short-circuit slot wires include a first short-circuit slot wire 15, a second short-circuit slot wire 16, and a third short-circuit slot wire 17; The first metal slotted line 11 and the second metal slotted line 14 are symmetrically arranged and are uniform transmission lines respectively, and the two form an impedance transformation network; The third metal slotted line 12 and the fourth metal slotted line 13 are symmetrically arranged and are uniform transmission lines respectively. The second short-circuit slot line 16 is an inverted "T" structure. The first short-circuit slot line 15 and the third short-circuit slot line 17 are respectively rotated toward the first metal slotted line 11 and the second metal slotted line 14, and are symmetrically arranged on both sides of the second short-circuit slot line 16. The first short-circuit slot line 15, the second short-circuit slot line 16 and the third short-circuit slot line 17 are respectively series short-circuit branches. The third metal slotted line 12, the fourth metal slotted line 13, the first short-circuit slot line 15, the second short-circuit slot line 16 and the third short-circuit slot line 17 form a short-circuit branch type band-stop network.

[0045] In the second embodiment, in the short-circuit branch type band-stop network, the physical structure of the short-circuit branch is implemented by the short-circuit slot line, and the impedance of the short-circuit slot line increases with the increase of its own width.

[0046] In the second embodiment, the third metal layer B19 is parallel to the first metal layer A18, and includes a first metal strip 20, a second metal strip 21 and a third metal strip 22. The first metal strip 20, the second metal strip 21 and the third metal strip 22 are parallel and correspond to the first short-circuit slot line 15, the second short-circuit slot line 16 and the third short-circuit slot line 17 in sequence. The three metal strips are used to reduce the characteristic impedance of the first short-circuit slot line 15, the second short-circuit slot line 16 and the third short-circuit slot line 17, thereby reducing the slot line short-circuit branch width. In the second embodiment, the periodic size of the provided band-stop frequency selective surface is the same as that of the first embodiment. Combined with Figure 7-Figure 8 The physical dimensions of the band-stop frequency selective surface are marked, and its design parameters are as follows: P x =15mm, P y =15mm, d 1=0.508mm, d 2 = 7.246 mm, W 6=7.8mm, W 7=6.7mm, W 8=0.4mm, W 9=0.5mm, W 10 =0.4mm, W 11 =0.6mm, W 10 =0.4mm, L 6=14mm, L 7=13.84mm, L 8=10.06mm, L 9=4.4mm, L 10 =6.9mm, L 11 =10.06mm, L 12 =4.4mm, L 13 =6.9mm.

[0047] By covering the third layer with parallel metal strips parallel to the short-circuit slot lines of the first layer, the impedance of the slot lines can be further reduced, thereby meeting the design requirements of narrow-band stop response with small impedance, thereby achieving a narrower stopband bandwidth.

[0048] The short-circuit branch-type band-stop network is combined with the impedance transformation network to form the band-stop frequency selection surface of the present invention. The band-stop frequency selection surface is designed to be bilaterally symmetrical. The rotation of the first short-circuit slot line 15 and the third short-circuit slot line 17, as well as the bending of the second short-circuit slot line 16, is intended to reduce y In order to avoid the grating lobe effect of the band-stop frequency selective surface, in the three-dimensional space coordinate system, y , x The stacked slot line unit size in the direction P y , P x Less than or equal to one quarter of the wavelength corresponding to the center frequency of 5 GHz, usually P y and P x They are equal in size, and they jointly affect the free space wave impedance and the stacked slot line impedance.

[0049] In summary, the band-stop frequency selective surface of the second embodiment of the present invention still adopts a three-dimensional stacked slot line structure, which is mapped and modeled by two parts: an equivalent impedance transformation network and a band-stop network. However, the difference from the first embodiment is that the second embodiment adds a metal strip parallel to the upper metal slot on the lower surface of the dielectric substrate to reduce the width of the slot line short-circuit branch, and also achieves high selectivity within the stop band working frequency band, while having good passband performance outside the working frequency band.

[0050] See also Fig. 9 The embodiment of the present invention further provides a comprehensive design method of a band-stop frequency selective surface based on impedance transformation, which is implemented by using the band-stop frequency selective surface based on impedance transformation, and includes the following steps: S1. According to the stopband index requirements of the required stopband frequency selection surface, select the short-circuit branch type stopband network of appropriate order and its port impedance; S2. For a short-circuit branch-type band-stop network of known order, the band-stop transformation function or appropriate characteristic function can be used to establish the analytical relationship between the band-stop index and each component in the band-stop network, and solve the parameters of each component; S3. According to the impedance transformation theory, the port impedance of the selected band-stop network is transformed with the free space wave impedance to determine the parameters of each component in the impedance transformation network when the impedance matching is achieved within the stopband frequency range; S4. The selected band-stop network and the determined impedance transformation network are mapped respectively to form a three-dimensional stacked slot-line band-stop frequency selective surface unit, and finally the actual physical structure of the band-stop frequency selective surface is determined, and a physical sample can be produced using a printed circuit board process.

[0051] The present invention designs a band-stop frequency selective surface with high selectivity in the stop band and good full-band passband by comprehensively designing the band-stop network and the impedance transformation network. Fig.10 As shown, a general circuit topology of the present invention is given, which is divided into two parts: space electromagnetic wave and guided wave, wherein the guided wave part is a combination of a single-section or multi-section cascade impedance transformation network and a short-circuit branch type band-stop network. Fig.11 As shown, a typical S parameter curve of the present invention is given. Within the working frequency band, a highly selective stop band is achieved, the full-band pass band is good, and the pass band return loss is below 10dB.

[0052] like Fig.12 As shown, the S parameter curve of the full-wave electromagnetic simulation of the band-stop frequency selective surface of Example 1 is given, with a center frequency of 5.00 GHz, a 3dB bandwidth of 4.90-5.10 GHz, high selectivity in the stop band, good pass band at 4.87-5.14 GHz, and a return loss of less than 10 dB.

[0053] like Fig.13 As shown, the S parameter curve of the full-wave electromagnetic simulation of the band-stop frequency selective surface of Example 2 is given, with a center frequency of 5.01 GHz, a 3dB bandwidth of 4.91-5.11 GHz, a high selectivity of the stop band, a good pass band outside 4.88-5.15 GHz, and a return loss of less than 10 dB.

[0054] In this embodiment, the factors of the comprehensive design of the band-stop frequency response in the band-stop network include at least: the stop-band center frequency, the stop-band bandwidth and the pass-band return loss. The band-stop network is combined with an impedance transformation network to have high selectivity within the stop-band, good full-band passband, and easy physical realization of the frequency selective surface.

[0055] In this embodiment, the band-stop network adopts a short-circuit branch-type band-stop circuit topology, and the characteristic function that can be used includes at least an optimal band-stop characteristic function.

[0056] In the first and second embodiments of the present application, the characteristic function of the short-circuit branch type band-stop network of the band-stop frequency selective surface is the optimal band-stop characteristic function. Compared with the Chebyshev characteristic function of the same order, the optimal band-stop characteristic function has a steeper attenuation characteristic in the stop band; Specifically, the optimal band-stop characteristic function F N （f） It is expressed as follows:

[0057] in: t andt c They are:

[0058] T n ( x )and U n ( x ) are respectively n Chebyshev functions of the first and second kind.

[0059] In this embodiment, the physical structure of the band-stop network is realized by a three-dimensional stacked slot line structure, and the band-stop network includes short-circuited branches in series and uniform transmission lines in cascade, the short-circuited branches serve as band-stop resonators, and the uniform transmission lines serve as coupling resonators, both of which operate at the center frequency of the stop band; In the circuit topology, the series short-circuit branches and the cascaded uniform transmission lines correspond to the series short-circuit slot lines and the cascaded metal slot lines in the three-dimensional stacked slot line structure respectively.

[0060] In this embodiment, the band-stop frequency selective surface is used as a spatial electromagnetic wave amplitude control device, and the impedance transformation network at its input and output ports is used to realize the impedance transformation between the free space wave and the band-stop network, while ensuring that the performance within the stopband remains unchanged and the out-of-band passband performance is good; The impedance transformation network uses a single-section or multi-section cascaded uniform transmission line as a single-section or multi-section impedance transformer, all of which work at the stopband center frequency; In the circuit topology, a single-section or multi-section cascaded uniform transmission line corresponds to a single-section or cascaded metal slotted line in the three-dimensional stacked slotted line structure.

[0061] In this embodiment, impedance transformation can adopt multi-stage cascade technology, such as Chebyshev multi-section matching transformer, to further expand the stopband width of the band-stop frequency selective surface while maintaining good in-band insertion loss characteristics, and all can be achieved by multi-section cascaded metal slotted lines.

[0062] In this embodiment, the three-dimensional stacked slot-line type band-stop frequency selective surface has the ability to convert spatial electromagnetic waves and guided wave modes, and can convert complex spatial electromagnetic waves into guided waves that are easy to control, thereby performing a comprehensive design of "field-to-path" conversion from the perspective of "path", and directly mapping the distributed transmission line model to realize the three-dimensional stacked slot-line structure, thereby improving its design efficiency and accuracy.

[0063] An embodiment of the present invention further provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the processor executes the steps of the above method.

[0064] See also Fig.14 An embodiment of the present invention further provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the above method.

[0065] The embodiment of the present invention further provides a computer program product comprising instructions, which, when executed on a computer, enables the computer to execute the steps of the above method.

[0066] It is understandable that the system, device and storage medium provided in the embodiments of the present invention correspond to the method provided in the embodiments of the present invention, and the explanation, examples and beneficial effects of the relevant contents can refer to the corresponding parts in the above methods.

[0067] It should be noted that those skilled in the art can understand that all or part of the steps implemented in the embodiments of the present invention can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using hardware, it can be implemented in whole or in part in the form of purchased standard parts or modified parts. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from one website, computer, server or data center to another website, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated. The available medium may be a magnetic medium (eg, a floppy disk, a hard disk, a magnetic tape), an optical medium (eg, a DVD), or a semiconductor medium (eg, a solid state disk (SSD)).

[0068] In summary, the present invention proposes the idea of ​​combining band-stop circuit design with impedance transformation, realizes the comprehensive design of band-stop frequency selective surface in the three-dimensional stacked slot-line structure, and makes the band-stop circuit prototype correspond to the physical structure of the three-dimensional stacked slot-line frequency selective surface, so as to design a band-stop frequency selective surface with high selectivity within the stop band and good full-band passband.

[0069] It should be understood that the examples and implementation modes described herein are for illustrative purposes only and are not intended to limit the present invention. Those skilled in the art may make various modifications or changes based on the examples and implementation modes. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A band-stop frequency selective surface based on impedance transformation, characterized in that: A three-dimensional stacked slot line structure is adopted, and a periodic array is formed by multiple stacked slot line units. Each stacked slot line unit is composed of two layers and / or three layers, including: the first layer is a metal layer A, the second layer is a dielectric substrate, and the third layer can be optionally set to be a metal layer B parallel to the first layer. The first to second layers and / or the first to third layers are pressed together in sequence.

2. The band-stop frequency selective surface based on impedance transformation according to claim 1, characterized in that: The first metal layer A is composed of cascaded metal slotted lines and series-connected short-circuit slotted lines; For the third-order band-stop frequency selective surface, the metal slotted lines include a first metal slotted line, a second metal slotted line, a third metal slotted line and a fourth metal slotted line, and the short-circuit slot lines include a first short-circuit slot line, a second short-circuit slot line and a third short-circuit slot line; The first metal slotted line and the second metal slotted line are symmetrically arranged and are uniform transmission lines respectively, and the two form an impedance transformation network; The third metal slotted line and the fourth metal slotted line are symmetrically arranged and are uniform transmission lines respectively. The second short-circuit slot line is in an inverted "T" structure. The first short-circuit slot line and the third short-circuit slot line are respectively rotated toward the first metal slotted line and the second metal slotted line, and are symmetrically arranged on both sides of the second short-circuit slot line. The first short-circuit slot line, the second short-circuit slot line and the third short-circuit slot line are respectively series short-circuit branches. The third metal slotted line, the fourth metal slotted line, the first short-circuit slot line, the second short-circuit slot line and the third short-circuit slot line form a short-circuit branch type band-stop network.

3. The band-stop frequency selective surface based on impedance transformation according to claim 2, characterized in that: In the short-circuit branch type band-stop network, the physical structure of the short-circuit branch is realized by the short-circuit slot line, and the impedance of the short-circuit slot line increases with the increase of its own width.

4. The band-stop frequency selective surface based on impedance transformation according to claim 2, characterized in that: The third metal layer B can be optionally set as needed, parallel to the first metal layer A, and includes a first metal strip, a second metal strip and a third metal strip. The first metal strip, the second metal strip and the third metal strip are parallel to each other and correspond to the first short-circuit slot line, the second short-circuit slot line and the third short-circuit slot line respectively.

5. A comprehensive design method of a band-stop frequency selective surface based on impedance transformation, implemented by using the band-stop frequency selective surface based on impedance transformation as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: S1. According to the stopband index requirements of the required stopband frequency selection surface, select the short-circuit branch type stopband network of appropriate order and its port impedance; S2. For a short-circuit branch-type band-stop network of known order, the band-stop transformation function or appropriate characteristic function can be used to establish the analytical relationship between the band-stop index and each component in the band-stop network, and solve the parameters of each component; S3. According to the impedance transformation theory, the port impedance of the selected band-stop network is transformed with the free space wave impedance to determine the parameters of each component in the impedance transformation network when the impedance matching is achieved within the stopband frequency range; S4. The selected band-stop network and the determined impedance transformation network are mapped respectively to form a three-dimensional stacked slot-line band-stop frequency selective surface unit, and finally the actual physical structure of the band-stop frequency selective surface is determined, and a physical sample can be produced using a printed circuit board process.

6. The comprehensive design method of the band-stop frequency selective surface based on impedance transformation according to claim 5, characterized in that: The factors for the comprehensive design of the band-stop frequency response in the band-stop network at least include: stop-band center frequency, stop-band bandwidth and pass-band return loss.

7. The comprehensive design method of the band-stop frequency selective surface based on impedance transformation according to claim 5, characterized in that: The band-stop network adopts a short-circuit branch-type band-stop circuit topology, and the characteristic functions that can be used include at least an optimal band-stop characteristic function.

8. The comprehensive design method of the band-stop frequency selective surface based on impedance transformation according to claim 7, characterized in that: The physical structure of the band-stop network is realized by a three-dimensional stacked slot line structure, and the band-stop network includes series-connected short-circuit branches and cascaded uniform transmission lines, the short-circuit branches serve as band-stop resonators, and the uniform transmission lines serve as coupling structures / resonators, both of which work at the center frequency of the stop band; In the three-dimensional stacked slot line structure, the series short-circuit slot lines correspond to the series short-circuit branches in the band-stop network, and the cascaded metal slot lines correspond to the cascaded uniform transmission lines in the band-stop network.

9. The comprehensive design method of the band-stop frequency selective surface based on impedance transformation according to claim 5, characterized in that: The band-stop frequency selective surface is used as a spatial electromagnetic wave amplitude control device, and the impedance transformation network of its input and output ports is used to realize the impedance transformation between the free space wave and the band-stop network, which can widely solve the problem of the spatial electromagnetic wave keeping the stopband performance unchanged within the amplitude comprehensive design band, and ensure good low-reflection bandpass performance outside the stopband; The impedance transformation network uses a single-section or multi-section cascaded uniform transmission line as a single-section or multi-section impedance transformer, all of which work at the stopband center frequency; In the three-dimensional stacked slot line structure, a single section or multiple sections of cascaded metal slotted lines correspond to a single section or multiple sections of cascaded uniform transmission lines in an impedance transformation network.

10. The comprehensive design method of the band-stop frequency selective surface based on impedance transformation according to claim 5, characterized in that: The three-dimensional stacked slot-line type band-stop frequency selective surface has the ability to convert spatial electromagnetic waves and guided wave modes, converting complex spatial electromagnetic waves into guided waves that are easy to control, thereby performing a comprehensive design of "field-to-path" conversion from the perspective of "path", and directly mapping the distributed transmission line model to realize the three-dimensional stacked slot-line structure to improve design efficiency and accuracy.

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