Radio frequency shielding box based on frequency selective surface structure

Abstract

The invention relates to a radio frequency shielding box based on a frequency selective surface structure, which comprises a box body, the box body comprises a surrounding plate and a medium between / around the surrounding plate, and the surrounding plate is provided with an etching groove or a patch; the coaming is formed by combining single / multiple layers of FSSs, and a nanotechnology is introduced into the structure of the FSSs; the FSS design method comprises the following steps: determining a working frequency; determining the size of the etching groove or the patch and the arrangement period of the etching groove or the patch according to the working frequency; by adjusting the geometrical shape and the arrangement mode of the FSS unit structure and accurately designing the FSS structure, the accurate frequency response design becomes possible, the performance is not easily influenced by environmental factors, and the stability and the reliability of the shielding effect are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of radio frequency shielding, and in particular relates to a radio frequency shielding box based on a frequency selective surface structure. Background Art

[0002] In the development of modern information technology, radio frequency interference (RFI) and electromagnetic interference (EMI) have become important factors affecting the performance and reliability of electronic equipment. There are many traditional RF shielding methods, but most of them have problems such as high complexity, high cost, unstable shielding effect, and performance is easily affected by environmental factors, and the frequency response cannot be designed. Frequency Selective Surface (FSS) is an emerging RF shielding technology. By constructing metal patches or etched grooves with specific patterns on the surface, it can selectively shield and filter RF signals of specific frequencies. However, how to use FSS to accurately filter and shield RF signals of specific frequencies, and how to determine the operating frequency and determine the size and arrangement period of the etched grooves or patches according to the operating frequency are blanks in the existing technology. Summary of the invention

[0003] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0004] In view of the following technical problems existing in the prior art: the prior art has the problems of high loss and low selectivity.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a radio frequency shielding box based on a frequency selective surface structure, comprising:

[0006] The box body includes a panel, and the panel is provided with an etching groove or a patch; the panel is composed of a FSS combination, and nano materials are introduced into the structure of the FSS;

[0007] The design methods of FSS include:

[0008] Determine the operating frequency;

[0009] The size of the etching groove or patch and the arrangement period of the etching groove or patch are determined according to the operating frequency.

[0010] As a preferred solution of the radio frequency shielding box based on the frequency selective surface structure of the present invention, wherein:

[0011] The etching groove or patch is in the shape of a square, a circle, an annular ring or a cross or a combination thereof.

[0012] As a preferred solution of the radio frequency shielding box based on the frequency selective surface structure of the present invention, wherein:

[0013] Also includes a radome.

[0014] As a preferred solution of the radio frequency shielding box based on the frequency selective surface structure of the present invention, when the etching groove or patch is square, its size is:

[0015]

[0016] in:

[0017] f r is the operating frequency,

[0018] C is the electromagnetic wave velocity,

[0019] ∈ r is the relative dielectric constant of the substrate

[0020] a is the side length of the square patch or etched groove.

[0021] As a preferred solution of the radio frequency shielding box based on the frequency selective surface structure of the present invention, when the etching groove or patch is circular, its size is:

[0022]

[0023] f r is the operating frequency, C is the electromagnetic wave speed, ∈ r is the relative dielectric constant of the dielectric substrate, r is the radius of the circular patch, and 1.841 is the zero point of the first root Bessel function.

[0024] As a preferred solution of the radio frequency shielding box based on the frequency selective surface structure of the present invention, when the etching groove or patch is annular, its size is:

[0025]

[0026] Where: r avg is the average radius of the annular patch, defined as (r in +r out ) / 2, where r in and r out are the inner and outer radius of the ring, respectively, and f r is the operating frequency, C is the electromagnetic wave speed, ∈ r is the relative dielectric constant of the dielectric substrate.

[0027] As a preferred solution of the radio frequency shielding box based on the frequency selective surface structure of the present invention, wherein:

[0028] When the etching groove or patch is rectangular, its dimensions are:

[0029]

[0030] Where: L and W are the length and width of the rectangular patch, respectively, and m and n are integers of the resonant modes. r is the operating frequency, C is the electromagnetic wave speed, ∈ r is the relative dielectric constant of the dielectric substrate.

[0031] As a preferred solution of the radio frequency shielding box based on the frequency selective surface structure of the present invention, wherein: the size of the cross-shaped etching groove is set, and the lengths of the four arms are defined as l1, l2, l3 and l4 respectively. For each arm, its corresponding resonant frequency f can be calculated respectively. 0i (i=1, 2, 3, 4), when the substrate dielectric constant and arm width are the same:

[0032]

[0033] Where c is the speed of light, ∈ eff is the effective dielectric constant.

[0034] As a preferred solution of the radio frequency shielding box based on the frequency selective surface structure of the present invention, the arrangement period of the etching grooves or patches is:

[0035] p=(1+α)×a

[0036] α is an additional spacing factor chosen between 0.1 and 0.5.

[0037] As an independent resonant mode design, p is usually chosen slightly larger than the unit size to avoid mutual coupling. p = (1 + α) × a, α is an additional spacing factor, usually between 0.1 and 0.5, to avoid coupling effects between units.

[0038] As a coupled mode resonator design, the choice of p should be determined by the wavelength at the coupled resonant mode and its frequency. The value of P can be non-uniform in the plane to achieve a specific combination pattern, i.e., boundary conditions, to facilitate the coupling of the designed resonant modes.

[0039] The beneficial effects of the present invention are as follows: by adjusting the geometric shape and arrangement of the FSS unit structure and accurately designing the FSS structure, accurate frequency response design becomes possible, and the performance is not easily affected by environmental factors, thereby improving the stability and reliability of the shielding effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0041] Figure 1 is a schematic diagram of the structure of the frequency selective surface in the present invention;

[0042] Figure 2 A schematic diagram of the structure of the combination of two shapes on the frequency selective surface of the present invention;

[0043] Figure 3 It is a schematic diagram of the structure of a single double-ring open resonator in the present invention;

[0044] Figure 4 It is a schematic diagram of the structure in which the frequency selective surface in the present invention is a cross. DETAILED DESCRIPTION

[0045] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0046] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0047] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0048] Secondly, the present invention is described in detail with reference to the schematic diagram. When describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0049] Example 1

[0050] Reference Figure 1 to Figure 4,This embodiment provides a radio frequency shielding box based on a frequency selective surface structure, including, a box body, the box body includes a panel, and the panel is provided with an etched groove or a patch; the panel is composed of a multi-layer FSS combination, and nano materials are introduced into the structure of the FSS;

[0051] The design methods of FSS include:

[0052] Determine the operating frequency;

[0053] The size of the etching groove or patch and the arrangement period of the etching groove or patch are determined according to the operating frequency.

[0054] The etched grooves or patches are square, circular, annular or cross-shaped and combinations thereof.

[0055] By using different types of FSS units / combinations as the isolation box walls of the RF shielding box (room), various transmission and reflection characteristics can be customized to meet the signal attenuation requirements of the RF shielding box (room) at single / multiple frequency points and within the frequency range (bandwidth).

[0056] The multilayer FSS filter is composed of multiple layers of single-layer FSS structures stacked together with dielectric layers in between. The multilayer structure can provide more complex frequency selectivity characteristics and improve bandwidth and performance.

[0057] The interlayer structures can be FSS patterns of the same or different shapes and sizes.

[0058] The dielectric layer between each layer can be the same or different material, and can be selected to be the same or different material as the substrate to adjust the layer spacing and electrical characteristics.

[0059] Furthermore, the multi-layer FSS structure is precisely aligned through alignment technology, and then bonded together using an adhesive or lamination process, and laminated under high temperature and high pressure, so that the multi-layer structure is firmly combined to form an overall FSS filter, which is then integrated in the box to form a RF shielding box.

[0060] The following is a comparison of single-layer and multi-layer FSS structures:

[0061] The single-layer FSS structure is relatively simple, and the design and manufacturing process is relatively straightforward, which is suitable for some basic frequency selectivity requirements; due to its simple structure, the required materials and manufacturing process costs are relatively low, making it suitable for mass production; the single-layer structure is lighter than the multi-layer structure, which has advantages for some weight-sensitive applications; it is suitable for occasions that require a thin design, such as patch antennas, stealth technology, etc.; it can be more easily integrated with other antennas or RF devices, making it suitable for compact designs.

[0062] The multi-layer FSS structure can achieve a wider operating frequency band and more complex frequency response characteristics, and is suitable for applications that require wide-band operation; through the multi-layer design, selective filtering of multiple frequency bands can be achieved, which is suitable for multi-band communication systems and complex radar systems; the multi-layer structure can provide higher filtering accuracy and better ability to suppress out-of-band signals, thereby improving system performance; the multi-layer design allows the use of different FSS patterns and dielectric materials in different layers to achieve more flexible electrical property adjustment; the multi-layer structure can achieve a higher quality factor (Q value), which is beneficial to improving the selectivity of the filter and reducing losses; the multi-layer FSS can realize the integration of multiple functions, such as having both reflection and transmission characteristics, or combining absorbing materials to achieve more complex electromagnetic characteristics.

[0063] Single-layer FSS is suitable for simple frequency selective applications, such as band shielding systems.

[0064] Multi-layer FSS is suitable for complex multi-band communication systems and occasions requiring multi-band selectivity and high-performance shielding.

[0065] Furthermore, in terms of manufacturing process, nanofabrication technology can be used to produce more sophisticated and complex FSS structures to improve performance.

[0066] In terms of regulation, the FSS filter can be electrically tuned to adjust the frequency response in real time by applying an electric field or voltage.

[0067] In terms of material selection, the use of metamaterials with negative refractive index or other unique electromagnetic properties can achieve more complex and efficient frequency selection characteristics, and the use of high dielectric constant materials to make substrates can reduce the size of FSS units and improve frequency selectivity.

[0068] Secondly, based on different application scenarios, different materials can be used to cope with different on-site environments. Specific examples are as follows:

[0069] Copper: High conductivity, widely used in electromagnetic shielding, easy to process.

[0070] Aluminum: Lightweight and highly conductive, suitable for applications requiring lightweight shielding.

[0071] Silver: Very conductive but more expensive, suitable for high performance shielding applications.

[0072] Nickel: Strong corrosion resistance, suitable for harsh environments.

[0073] Silver or copper coating: can be applied to non-conductive substrates such as plastics or ceramics to provide good shielding effects.

[0074] Conductive Paint: Paint containing conductive particles (such as silver, copper, carbon) that can be applied to a variety of substrates.

[0075] Metal fiber composites: Combines the advantages of metal fibers and polymers, with high conductivity and mechanical strength.

[0076] Carbon nanotube composite materials: have high conductivity and excellent shielding effect, but the cost is relatively high.

[0077] Polyaniline, polypyrrole: They have electrical conductivity and good mechanical properties and can be used in flexible shielding applications.

[0078] The following factors need to be considered in the design:

[0079] Highly conductive materials can effectively reflect and shield radio frequency signals. Conductive materials can produce strong electromagnetic shielding effects.

[0080] The thickness of the material needs to be large enough to ensure shielding effectiveness, but at the same time, weight and cost must be taken into consideration.

[0081] Select materials with high mechanical strength and durability, especially when used in harsh environmental conditions.

[0082] The material should be easy to process and fabricate so that complex geometries and fine patterns can be achieved.

[0083] Materials need to maintain stable EMI shielding performance under a variety of environmental conditions, including temperature changes, humidity, and chemical corrosion.

[0084] Compared with traditional filters or shielding devices, FSS can achieve a lightweight design and is suitable for applications with restrictions on device size and weight.

[0085] Custom designs can be made based on the frequency requirements and space constraints of specific applications, providing a more flexible solution.

[0086] In shielding equipment, FSS can be used as the surface of doors and windows to ensure communication and visual transmission within the frequency range; it can also be combined with other damping layers / absorption material patches to quickly achieve frequency-selective sound wave attenuation and fine-tune the frequency bandwidth.

[0087] As an example, when the etched slot or patch is square, its dimensions are:

[0088]

[0089] in:

[0090] f r is the operating frequency,

[0091] C is the electromagnetic wave velocity,

[0092] ∈ r is the relative dielectric constant of the substrate

[0093] a is the side length of the square patch or etched groove.

[0094] When the etching groove or patch is circular, its dimensions are:

[0095]

[0096] f r is the operating frequency, C is the electromagnetic wave speed, ∈ r is the relative dielectric constant of the dielectric substrate, r is the radius of the circular patch, and 1.841 is the zero point of the first root Bessel function.

[0097] When the etching groove or patch is annular, its dimensions are:

[0098]

[0099] Where: r avg is the average radius of the annular patch, defined as (r in +r out ) / 2, where r in and r out are the inner and outer radius of the ring, respectively, and f r is the operating frequency, C is the electromagnetic wave speed, ∈ r is the relative dielectric constant of the dielectric substrate.

[0100] When the etched slot or patch is rectangular, its dimensions are:

[0101]

[0102] Where: L and W are the length and width of the rectangular patch, m and n are integers of the resonant mode, and f r is the operating frequency, C is the electromagnetic wave speed, ∈ r is the relative dielectric constant of the dielectric substrate.

[0103] As an example, set the size of the cross-shaped etching groove and define the lengths of the four arms as l1, l2, l3 and l4. For each arm, the corresponding resonant frequency f can be calculated separately. 0i (i=1,2,3,4), when the substrate dielectric constant and arm width are the same:

[0104]

[0105] Where c is the speed of light, ∈ eff is the effective dielectric constant.

[0106] Effective dielectric constant∈ eff Relative dielectric constant of the substrate r To estimate.

[0107] The design process for the cross-shaped etching groove size is:

[0108] Determine the target frequency range: Determine the frequency range you want FSS to cover. It can be designed to cover a wide band or target specific multiple frequency points;

[0109] Select arm length: Set the respective resonant frequency f by selecting different arm lengths li 0i .

[0110] Determine the period a: Choose a suitable period a to ensure the periodicity and good frequency selectivity of the structure. Usually, the period a is still roughly 1.5 to 2 times the longest arm length.

[0111] Select arm width w: The selection of arm width w can be based on mechanical strength and manufacturing process considerations. Generally speaking, the arm width can be between 1 / 10 and 1 / 5 of the shortest arm length.

[0112] As a design example:

[0113] Assume that the lengths of the four arms are l = 40 mm, l2 = 30 mm, l3 = 20 mm, and l = 10 mm; the relative dielectric constant of the substrate is r =2.2.

[0114] Calculate the effective dielectric constant ∈ eff :

[0115]

[0116] Calculate the resonant frequency f 0i :

[0117]

[0118] Therefore, the design dimensions can resonate at 1.88 GHz, 2.5 GHz, 3.76 GHz, and 7.52 GHz; the location and bandwidth of these frequency points can be further optimized by properly adjusting the arm length and other structural parameters.

[0119] The arrangement period of etching grooves or patches is:

[0120] p=(1+α)×a

[0121] α is an additional spacing factor chosen between 0.1 and 0.5.

[0122] As an independent resonant mode design, p is usually chosen slightly larger than the unit size to avoid mutual coupling. p = (1 + α) × a, α is an additional spacing factor, usually between 0.1 and 0.5, to avoid coupling effects between units.

[0123] As a coupled mode resonator design, the choice of p should be determined by the wavelength at the coupled resonant mode and its frequency. The value of P can be non-uniform in the plane to achieve a specific combination pattern, i.e., boundary conditions, to facilitate the coupling of the designed resonant modes.

[0124] In addition to independent and coupled resonant modes, frequency selective surfaces (FSS) can also use multi-mode resonant modes to achieve multi-frequency selective response within a specific frequency band. This design approach uses multiple resonant modes in the structure to enhance the response of a specific frequency, thereby achieving more complex functions such as multi-band beam steering, focusing and filtering.

[0125] Furthermore, multi-band beam steering can achieve multi-band beam steering by utilizing different resonance modes to control the phase and amplitude responses of different frequency bands. In ultrasound imaging, this can help optimize imaging quality at multiple frequencies.

[0126] Further, its uses may include:

[0127] Multimode FSS can be used to design spectrum selective devices that allow specific frequencies to pass while blocking other frequencies, which has wide applications in communications and radar systems.

[0128] By sensing the changes in response at different frequencies, multimode FSS can be used for precise sensing and detection applications, such as measuring the material properties of an object or identifying signals of specific frequencies.

[0129] In communication systems, multimode design can increase system capacity and data transmission rate. For example, in fiber optic communications, multimode optical fiber can transmit multiple light modes at the same time, improving information transmission capabilities.

[0130] Multimode systems can optimize performance by selecting the appropriate mode to adapt to different working environments or requirements.

[0131] Dual-mode resonant FSS design example: Taking the double split-ring resonator (DSRC) as an example, when the inner ring is in the same plane as the outer ring, the widths of the inner ring and the outer ring are assumed to be equal. Its geometric parameters are outer ring diameter: D1 = 10mm, inner ring diameter: D2 = 7mm, ring spacing: g = 1mm, opening width: w = 0.5mm.

[0132] In resonance mode 1, the outer loop dominates, with a center frequency of 3 GHz; in resonance mode 2, the inner loop dominates, with a center frequency of 5 GHz.

[0133] The widths of the inner ring and the outer ring may also be set to be different, and the inner ring and the outer ring may be between different planes, and the two may be set in planes parallel to each other.

[0134] In a dual ring split resonator, the split width refers to the physical width of the split opening in the resonator. This is a key geometric parameter and is usually expressed as the linear distance between the two metal edges at the split opening.

[0135] This opening width affects the capacitance of the resonator, and thus its resonant frequency. Specifically, a narrower opening width increases the capacitance, causing the resonant frequency to decrease, while a wider opening width reduces the capacitance, causing the resonant frequency to increase; therefore, when designing DSRC, the opening width needs to be precisely adjusted according to the desired electromagnetic properties.

[0136] In a dual-ring split resonator, the split angle refers to the relative angle between the split parts of the two rings. This is a geometric parameter that describes the split direction and position.

[0137] Specifically, the opening angle represents the angle between the opening positions of the two concentric metal rings of the resonator. It determines the relative positioning between the opening parts of the two rings. The choice of the opening angle affects the electromagnetic properties of the resonator, including the resonant frequency, bandwidth, quality factor, and the distribution of electric and magnetic fields.

[0138] Small opening angle: When the opening angle is small, the opening positions of the two rings are relatively close. Such a design usually makes the resonator coupling stronger, which may lead to a larger bandwidth and a lower quality factor.

[0139] Large opening angle: When the opening angle is large, the opening positions of the two rings are relatively far apart; such a design will result in weaker coupling, usually resulting in a narrower bandwidth and a higher quality factor.

[0140] Multimode effect: By precisely adjusting the dimensions of the outer and inner rings, a strong resonant response can be achieved at both 3 GHz and 5 GHz; suitable for beam steering or filtering applications that process both frequency bands simultaneously.

[0141] The present invention aims to solve the problems in the prior art that radio frequency shielding has no frequency selectivity, the frequency response cannot be designed, the effect is poor, the design is complex and the cost is high. The present invention proposes a radio frequency shielding box based on a frequency selective surface structure and a design method thereof. The method achieves accurate shielding of radio frequency signals of a specific frequency / segment through the design of a frequency selective surface, determines the size of the etching groove or patch and the arrangement period of the etching groove or patch and the combination within / between the plane according to the operating frequency, and achieves an efficient radio frequency shielding effect. The design method makes accurate frequency response design possible, and the performance is not easily affected by environmental factors, thereby improving the stability and reliability of the shielding effect.

[0142] Specifically, a periodic structure is designed in the frequency selective surface, and precise shielding of the target frequency radio frequency signal is achieved through specific design.

[0143] Determine the operating frequency / band and select the appropriate etch slot or patch size based on that frequency.

[0144] The arrangement period of the etched grooves or patches is designed to ensure that the shielding effect of the frequency selective surface is optimized.

[0145] Optimization of process parameters during manufacturing, including material selection, etching process, and assembly methods.

[0146] The technical effect is: making accurate frequency response design possible, and the performance is not easily affected by environmental factors, improving the stability and reliability of the RF shielding effect;.

[0147] Furthermore, a suitable type of RF filter is selected, such as a bandpass filter, a bandstop filter or a low-pass filter, and is designed according to the frequency range required for shielding.

[0148] Determine the operating frequency and choose the appropriate etch slot or patch size based on the frequency, including:

[0149] Based on the application requirements and target environment, determine the operating frequency range of the RF signal that needs to be shielded. This step is usually completed through electromagnetic simulation and experimental measurement.

[0150] Calculate the size of the etching slot or patch based on the operating frequency. The size calculation formula is as follows:

[0151]

[0152] Where c is the speed of light, f is the operating frequency, ∈ r is the dielectric constant. According to the calculation results, choose the appropriate size for etching or patch design.

[0153] Design the arrangement period of etching grooves or patches to ensure the optimal shielding effect of the frequency selective surface, including:

[0154] According to the working frequency and size calculation results, the arrangement period of the etching groove or patch is determined. For the independent resonance mode, the arrangement period should ensure the minimum coupling between adjacent units to avoid mutual interference. For the coupled resonance mode, the period size is determined by the coupling strength required by the design, and the design size can be optimized by finite element analysis.

[0155] Through electromagnetic simulation and optimization algorithms, the arrangement structure of etching grooves or patches is adjusted to ensure that the frequency selective surface is at the target frequency.

[0156] Prototypes were made and experimental verification was carried out to confirm the rationality and effectiveness of the arrangement period and structural design by measuring the shielding effectiveness and filtering characteristics.

[0157] Furthermore, the process parameter optimization during the manufacturing process includes:

[0158] Select appropriate substrate materials and conductive materials. The substrate material needs to have good dielectric properties and mechanical strength, such as FR4, ceramic substrate, etc. Conductive materials are commonly copper or silver.

[0159] According to the design requirements, select the appropriate etching process, such as wet etching or laser etching, to ensure the accuracy and consistency of the etching groove or patch. Process parameters such as etching time and etching solution concentration need to be optimized through experiments.

[0160] Select appropriate assembly methods, such as patch welding, screw fixing, etc., to ensure the mechanical stability and electrical connection reliability of the filter and FSS structure. Be careful to avoid damaging the etching grooves or patches during assembly.

[0161] It should be understood that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but for those of ordinary skill having the benefit of this disclosure, the development effort will be a routine task of design, fabrication, and production without undue experimentation.

[0162] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A radio frequency shielding box based on a frequency selective surface structure, characterized in that: include, The box body includes a panel, and the panel is provided with an etching groove or a patch; the panel is composed of a FSS combination, and nano materials are introduced into the structure of the FSS; The design methods of FSS include: Determine the operating frequency; The size of the etching groove or patch and the arrangement period of the etching groove or patch are determined according to the operating frequency.

2. The radio frequency shielding box based on frequency selective surface structure according to claim 1 is characterized in that: The etching groove or patch is in the shape of a square, a circle, an annular ring or a cross or a combination thereof.

3. The radio frequency shielding box based on frequency selective surface structure according to claim 2 is characterized in that: Also includes a radome.

4. The design method of the radio frequency shielding box according to claim 3 is characterized in that: When the etching groove or patch is square, its dimensions are: in: f r is the operating frequency, C is the electromagnetic wave velocity, ∈ r is the relative dielectric constant of the dielectric substrate a is the side length of the square patch or etched groove.

5. The design method of the radio frequency shielding box according to claim 4 is characterized in that: When the etching groove or patch is circular, its dimensions are: f r is the operating frequency, C is the electromagnetic wave speed, ∈ r is the relative dielectric constant of the dielectric substrate, r is the radius of the circular patch, and 1.841 is the zero point of the first root Bessel function.

6. The design method of the radio frequency shielding box according to claim 5, characterized in that: When the etching groove or patch is annular, its dimensions are: Where: r avg is the average radius of the annular patch, defined as (r in +r out ) / 2, where r in and r out are the inner and outer radii of the ring, respectively, and f r is the operating frequency, C is the electromagnetic wave speed, ∈ r is the relative dielectric constant of the dielectric substrate.

7. The design method of the radio frequency shielding box according to claim 6, characterized in that: When the etching groove or patch is rectangular, its dimensions are: Where: L and W are the length and width of the rectangular patch, respectively, and m and n are integers of the resonant modes. r is the operating frequency, C is the electromagnetic wave speed, ∈ r is the relative dielectric constant of the dielectric substrate.

8. The design method of the radio frequency shielding box according to claim 7, characterized in that: Set the size of the cross-shaped etching groove and define the lengths of the four arms as l1, l2, l3 and l4. For each arm, the corresponding resonant frequency f can be calculated separately. 0i (i=1, 2, 3, 4), when the substrate dielectric constant and arm width are the same: Where c is the speed of light, ∈ eff is the effective dielectric constant.

9. The design method of the radio frequency shielding box according to claim 8, characterized in that: The arrangement period of etching grooves or patches is: p=(1+α)×a α is an additional spacing factor chosen between 0.1 and 0.5.

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