Frequency selective surface antenna cover structure and method with lightning protection capability

Abstract

The application discloses a frequency selective surface antenna cover structure with lightning protection capability, comprising a dielectric substrate, the front surface of the dielectric substrate is provided with an FSS lightning shunt function layer, the back surface of the dielectric substrate is provided with a back surface metal fixing layer, the outer edge of the FSS lightning shunt function layer is provided with a metal bus border, the dielectric substrate is provided with a metalized via hole, and the FSS lightning shunt function layer and the back surface metal fixing layer are connected through the metalized via hole. The application further discloses a preparation method of the frequency selective surface antenna cover structure with lightning protection capability. The application solves the problems of the prior art, such as the absence of lightning protection capability of the frequency selective surface antenna cover, the influence of the external shunt strip on electromagnetic performance, and poor structural reliability.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic protection technology for radomes, specifically relating to a frequency selective surface radome structure with lightning protection capability, and also to a method for preparing a frequency selective surface radome structure with lightning protection capability. Background Technology

[0002] A frequency selective surface (FSS) is a spatial electromagnetic filter structure composed of periodic metal resonant units. When applied to radomes, it can achieve low-loss wave transmission in the operating frequency band and high cutoff reflection in the non-operating frequency band. It is a core technology solution for the next generation of stealth radomes and has been widely used in airborne antennas, satellite communications and other fields.

[0003] Airborne radomes are located in lightning 1A and 2A zones of the aircraft and are susceptible to direct lightning strikes during flight. High voltage and high current can break down the radome and damage the internal radar equipment, so lightning protection is essential. In existing technologies, lightning protection for composite material radomes is mainly achieved by attaching metal shunt strips to the surface of the radome, using continuous metal conductors to divert lightning current to the metal frame of the fuselage.

[0004] However, the above-mentioned solutions have significant technical flaws in frequency selective surface radomes. The metal elements of a pure FSS radome are discontinuous periodic structures, lacking a continuous high-current discharge path. When struck by direct lightning, they are prone to localized breakdown, ablation, and damage to the metal structure, resulting in extremely weak lightning protection and failing to meet the requirements for use in strong lightning environments such as airborne applications. The continuous metal shunt strips disrupt the frequency selective surface's wave transmission characteristics, leading to operating frequency band shifts, significantly increased insertion loss, and antenna pattern distortion. These negatively impact the antenna's operating range and effectiveness, while also increasing the radome's radar cross-section, weakening the aircraft's stealth capabilities. Summary of the Invention

[0005] The purpose of this invention is to provide a frequency selective surface radome structure with lightning protection capability, which solves the problems of existing frequency selective surface radomes having no lightning protection capability, external shunt bars affecting electromagnetic performance, and poor structural reliability.

[0006] Another objective of this invention is to provide a method for fabricating a frequency-selective surface radome structure with lightning protection capability.

[0007] The technical solution adopted in this invention is a frequency selective surface radome structure with lightning protection capability, including a dielectric substrate, an FSS lightning shunt functional layer on the front side of the dielectric substrate, a back metal fixing layer on the back side of the dielectric substrate, a metal bus frame on the outer edge of the FSS lightning shunt functional layer, and metallized vias penetrating the dielectric substrate. The FSS lightning shunt functional layer and the back metal fixing layer are connected through the metallized vias.

[0008] The invention is further characterized by: The dielectric substrate is an epoxy glass fiber composite board with a thickness of 1mm to 3mm, a real part of dielectric constant of 2.0 to 4.0, a loss tangent of less than 0.01, and a glass transition temperature of greater than or equal to 170℃.

[0009] The metal thickness of the FSS lightning shunt functional layer is 120μm~200μm; the FSS lightning shunt functional layer consists of periodically arranged quadrangular star-shaped metal resonant units, which are arranged in a planar array on the front side of the dielectric substrate with a period of 18mm~22mm. The gap width between two adjacent quadrangular star-shaped metal resonant units is 0.1mm~0.3mm; the quadrangular star-shaped metal resonant unit has a quadrangular star-shaped cross structure with four branches arranged in a cross shape. The root width of the four branches is 3.0mm~5.0mm, and the length of the four branches is 19.6mm~19.9mm; the operating frequency band of the FSS lightning shunt functional layer is 9.4GHz~12GHz, the in-band insertion loss of the FSS lightning shunt functional layer is less than or equal to 0.5dB, and the out-of-band rejection of the FSS lightning shunt functional layer is greater than or equal to 20dB.

[0010] The thickness of the back metal fixing layer is 120μm~160μm; the back metal fixing layer is a circular metal sheet, the axis of the circular metal sheet is aligned with the geometric center of the four-pointed star metal resonant unit in the thickness direction of the dielectric substrate, the radius of the circular metal sheet is 1.2mm~2.0mm, the circular metal sheet is located on the back of the dielectric substrate and corresponds to the position of the four-pointed star metal resonant unit.

[0011] The metallized vias are vertically disposed along the thickness direction of the dielectric substrate. The upper end of the metallized via is connected to the geometric center of the quadrangular star metal resonator, and the lower end of the metallized via is connected to the axis of the back metal fixing layer. The radius of the metallized via is 0.8mm~1.0mm, and the copper plating thickness of the via wall is 25μm~35μm. The metallized vias are arranged in an equally spaced array on the dielectric substrate, and the center-to-center distance between two adjacent metallized vias is the same as the array period of the quadrangular star metal resonator.

[0012] The metal busbar frame is a continuous metal ring structure with a width of 20mm~25mm. It is located around the outermost edge of the FSS lightning shunt functional layer. The inner edge of the metal busbar frame is connected to the outer edge of the outermost FSS lightning shunt functional layer to form a discharge path, and is also connected to the outermost four-corner star-shaped metal resonant unit.

[0013] Another technical solution adopted in this invention is a method for preparing a frequency-selective surface radome structure with lightning protection capability, comprising the following steps: Step 1: Take a double-sided copper-clad dielectric substrate and process through holes on the dielectric substrate; Step 2: Perform hole metallization treatment on the through holes to form metallized vias within the through holes; Step 3: Fabricate an FSS lightning shunt functional layer and a metal bus border on the front side of the dielectric substrate, and fabricate a back metal fixing layer on the back side of the dielectric substrate.

[0014] Another feature of the technical solution adopted in this invention is that: In step 1, the dielectric substrate is an epoxy glass fiber composite board with a thickness of 1mm to 3mm, a real part of dielectric constant of 2.0 to 4.0, a loss tangent of less than 0.01, and a glass transition temperature of greater than or equal to 170℃; the radius of the through hole is 0.8mm to 1.0mm, and the position of the through hole corresponds one-to-one with the geometric center position of the preset FSS resonant unit; the through hole is machined using a CNC drilling machine, the roughness of the hole wall is controlled to be less than or equal to 10μm, and the burrs at the opening of the through hole are removed.

[0015] In step 2, the via metallization process includes a desmearing process, a palladium activation process, a chemical copper plating process, and a full-board electroplating process performed sequentially. The desmearing process removes the adhesive residue from the via wall. The palladium activation process forms a palladium activation layer on the surface of the via wall. The chemical copper plating process forms a continuous copper seed layer on the via wall. The full-board electroplating process thickens the copper layer on the via wall to 25μm~35μm, forming a metallized via inside the via. The metallized via enables electrical interconnection between the copper layer on the front side and the copper layer on the back side of the dielectric substrate.

[0016] In step 3, photosensitive dry films are attached to the front and back sides of the dielectric substrate, respectively. The FSS resonant unit pattern, metal bus border pattern, and back metal pattern are transferred to the copper foil surface through photolithography exposure and development. The exposed copper foil is removed using an acidic copper chloride etching process, retaining the target metal pattern. Then the dry film is removed, forming the FSS lightning shunt functional layer and metal bus border on the front side, and forming the back metal fixing layer on the back side. The metal layer thickness of the FSS lightning shunt functional layer, metal bus border, and back metal fixing layer is 120μm~160μm. It also includes step 4: electroplating silver on the FSS lightning shunt functional layer, the metal bus frame on the front side of the dielectric substrate and the back metal fixing layer on the back side; it also includes a finished product inspection process, which includes conducting continuity tests, pattern accuracy tests and insulation resistance tests on the FSS lightning shunt functional layer and the metal bus frame.

[0017] The beneficial effects of this invention are: (1) Electromagnetic performance is unaffected, and wave transmission and lightning protection functions are compatible: This invention incorporates the protection concept of lightning current discharge into the design of the frequency selective surface, taking into account the electromagnetic transmission characteristics of the frequency selective surface. Simulation tests show that the insertion loss in the operating frequency band is less than 0.5dB, which replaces the defect of traditional shunt bar design that seriously affects the electromagnetic characteristics of the frequency selective surface radome.

[0018] (2) Constructing a leakage path to improve lightning protection capability: The leakage path is formed by “frequency selective surface + outer edge bus ring”. After lightning strikes the frequency selective surface, the high voltage forms a plasma conductive path on the upper part of the frequency selective surface. The lightning current is quickly dispersed to the frame bus ring and then discharged to the equipotential grounding terminal of the body, realizing the integrated design of frequency selective wave transmission and lightning protection.

[0019] (3) Reliable structure and mature process: The whole is manufactured using standard PCB process. The frequency selection surface metal layer, back metal fixing plate and dielectric substrate are firmly bonded. Metallized vias enhance the reliability of both and avoid the problem of metal sheet delamination and detachment under repeated high current impacts, which greatly improves long-term stability. No special customized process is required. It can be achieved by following the mature double-sided PCB processing flow. The pattern accuracy is high and the consistency is good. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the frequency selective surface radome structure with lightning protection capability of the present invention. Figure 2 This is a schematic diagram of the connection of the FSS lightning shunt functional layer of the present invention.

[0021] In the figure, 1. dielectric substrate, 2. FSS lightning shunt functional layer, 3. back metal fixing layer, 4. metallized via, 5. metal bus frame. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0023] This invention provides a frequency-selective surface radome structure with lightning protection capability, such as... Figure 1 , 2As shown, the device includes a dielectric substrate 1, an FSS lightning shunt functional layer 2 on the front side of the dielectric substrate 1, a back metal fixing layer 3 on the back side of the dielectric substrate 1, a metal busbar frame 5 on the outer edge of the FSS lightning shunt functional layer 2, and a metallized via 4 penetrating the dielectric substrate 1. The FSS lightning shunt functional layer 2 and the back metal fixing layer 3 are connected through the metallized via 4. The dielectric substrate 1 is an epoxy glass fiber composite material board with a thickness of 1 mm. The dielectric substrate 1 has a dielectric constant of 2.0 to 4.0 with a thickness of ~3mm, and a loss tangent of less than 0.01. The glass transition temperature of the dielectric substrate 1 is greater than or equal to 170℃. The metal thickness of the FSS lightning shunt functional layer 2 is 120μm to 200μm. The FSS lightning shunt functional layer 2 is composed of periodically arranged quadrangular star-shaped metal resonant units. These units are arranged in a planar array on the front side of the dielectric substrate 1 with a period of 18mm to 22mm. The gap between adjacent quadrangular star-shaped metal resonant units is wide. The thickness is 0.1mm~0.3mm; the four-pointed star-shaped metal resonator unit has a four-pointed star-shaped cross structure with four branches arranged in a cross shape. The root width of the four branches is 3.0mm~5.0mm, and the length of the four branches is 19.6mm~19.9mm; the operating frequency band of the FSS lightning shunt functional layer 2 is 9.4GHz~12GHz, the in-band insertion loss of the FSS lightning shunt functional layer 2 is less than or equal to 0.5dB, and the out-of-band suppression of the FSS lightning shunt functional layer 2 is greater than or equal to 20dB; the metal thickness of the back metal fixing layer 3 is 120μm~160μm. m; The back metal fixing layer 3 is a circular metal sheet. The axis of the circular metal sheet is aligned with the geometric center of the four-pointed star metal resonator unit in the thickness direction of the dielectric substrate 1. The radius of the circular metal sheet is 1.2mm~2.0mm. The circular metal sheet is located on the back of the dielectric substrate 1 and corresponds to the position of the four-pointed star metal resonator unit. The metallized via 4 is perpendicularly disposed along the thickness direction of the dielectric substrate 1. The upper end of the metallized via 4 is connected to the geometric center of the four-pointed star metal resonator unit, and the lower end of the metallized via 4 is connected to the axis of the back metal fixing layer 3. The radius of the metallized via 4 is 0. The metallized vias 4 have a wall copper plating thickness of 25μm~35μm and a diameter of 8mm~1.0mm. The metallized vias 4 are arranged in an equally spaced array on the dielectric substrate 1. The center-to-center distance between two adjacent metallized vias 4 is the same as the array period of the four-corner star-shaped metal resonant unit. The metal bus frame 5 is a continuous metal ring structure with a width of 20mm~25mm. It is located around the outermost edge of the FSS lightning shunt functional layer 2. The inner edge of the metal bus frame 5 is connected to the outer edge of the outermost FSS lightning shunt functional layer 2 to form a leakage path, and is connected to the outermost four-corner star-shaped metal resonant unit.

[0024] The present invention discloses a method for fabricating a frequency-selective surface radome structure with lightning protection capability, comprising the following steps: Step 1: Take a double-sided copper-clad dielectric substrate 1 and process through holes on the dielectric substrate 1; In step 1, the dielectric substrate 1 is an epoxy glass fiber composite board with a thickness of 1mm to 3mm, a real part of dielectric constant of 2.0 to 4.0, a loss tangent of less than 0.01, and a glass transition temperature of greater than or equal to 170℃; the radius of the through hole is 0.8mm to 1.0mm, and the position of the through hole corresponds one-to-one with the geometric center position of the preset FSS resonant unit; the through hole is machined using a CNC drilling machine, the roughness of the hole wall is controlled to be less than or equal to 10μm, and the burrs at the opening of the through hole are removed; Step 2: Perform hole metallization treatment on the through hole to form a metallized via 4 inside the through hole; In step 2, the via metallization process includes a desmearing process, a palladium activation process, a chemical copper plating process, and a full-board electroplating process performed sequentially. The desmearing process removes the adhesive residue from the via wall. The palladium activation process forms a palladium activation layer on the surface of the via wall. The chemical copper plating process forms a continuous copper seed layer on the via wall. The full-board electroplating process thickens the copper layer on the via wall to 25μm~35μm and forms a metallized via 4 in the via. The metallized via 4 realizes the electrical interconnection between the front copper layer and the back copper layer of the dielectric substrate 1. Step 3: Fabricate the FSS lightning shunt functional layer 2 and the metal bus frame 5 on the front side of the dielectric substrate 1, and fabricate the back metal fixing layer 3 on the back side of the dielectric substrate 1. In step 3, photosensitive dry films are attached to the front and back sides of the dielectric substrate 1, respectively. The FSS resonant unit pattern, the metal bus frame pattern, and the back metal pattern are transferred to the copper foil surface by photolithography exposure and development. The exposed copper foil is removed by acidic copper chloride etching process, retaining the target metal pattern. Then the dry film is removed, and the FSS lightning shunt functional layer 2 and the metal bus frame 5 are formed on the front side, and the back metal fixing layer 3 is formed on the back side. The metal layer thickness of the FSS lightning shunt functional layer 2, the metal bus frame 5, and the back metal fixing layer 3 is 120μm~160μm. It also includes step 4: electroplating silver on the FSS lightning shunt functional layer 2, the metal bus frame 5 on the front side of the dielectric substrate 1 and the back metal fixing layer 3 on the back side; it also includes a finished product inspection process, which includes conducting continuity tests, pattern accuracy tests and insulation resistance tests on the FSS lightning shunt functional layer 2 and the metal bus frame 5.

[0025] By integrating lightning protection and frequency selective surface design, the system achieves coordinated lightning attachment, rapid current shunting, and frequency selection functions. It can be widely applied in the design and manufacturing of frequency selective surface radomes for aircraft, significantly improving the lightning protection effect of the radome while ensuring frequency selection functionality.

[0026] Example 1 The frequency-selective surface radome structure with lightning protection capability proposed in this embodiment is as follows: Figure 1 , 2 As shown, the device includes a dielectric substrate 1, an FSS lightning shunt functional layer 2 on the front side of the dielectric substrate 1, a back metal fixing layer 3 on the back side of the dielectric substrate 1, a metal bus frame 5 on the outer edge of the FSS lightning shunt functional layer 2, and a metallized via 4 through the dielectric substrate 1. The FSS lightning shunt functional layer 2 and the back metal fixing layer 3 are connected through the metallized via 4.

[0027] Example 2 The frequency-selective surface radome structure with lightning protection capability proposed in this embodiment is as follows: Figure 1 , 2 As shown, the device includes a dielectric substrate 1, an FSS lightning shunt functional layer 2 on the front side of the dielectric substrate 1, a back metal fixing layer 3 on the back side of the dielectric substrate 1, a metal busbar frame 5 on the outer edge of the FSS lightning shunt functional layer 2, and a metallized via 4 penetrating the dielectric substrate 1. The FSS lightning shunt functional layer 2 and the back metal fixing layer 3 are connected through the metallized via 4. The dielectric substrate 1 is an epoxy glass fiber composite material board with a thickness of 1 mm. The dielectric substrate 1 has a dielectric constant of 2.0 to 4.0 with a thickness of ~3mm, and a loss tangent of less than 0.01. The glass transition temperature of the dielectric substrate 1 is greater than or equal to 170℃. The metal thickness of the FSS lightning shunt functional layer 2 is 120μm to 200μm. The FSS lightning shunt functional layer 2 is composed of periodically arranged quadrangular star-shaped metal resonant units. These units are arranged in a planar array on the front side of the dielectric substrate 1 with a period of 18mm to 22mm. The period is 18mm to 22mm. Adjacent quadrangular star-shaped metal resonant units are arranged in a planar array. The gap width between the metal resonator units is 0.1mm~0.3mm; the four-pointed star metal resonator unit has a four-pointed star cross structure with four branches arranged in a cross shape. The root width of the four branches is 3.0mm~5.0mm and the length of the four branches is 19.6mm~19.9mm; the operating frequency band of the FSS lightning shunt functional layer 2 is 9.4GHz~12GHz, the in-band insertion loss of the FSS lightning shunt functional layer 2 is less than or equal to 0.5dB, and the out-of-band suppression of the FSS lightning shunt functional layer 2 is greater than or equal to 20dB.

[0028] Example 3 The frequency-selective surface radome structure with lightning protection capability proposed in this embodiment is as follows: Figure 1 , 2As shown, the device includes a dielectric substrate 1, an FSS lightning shunt functional layer 2 on the front side of the dielectric substrate 1, a back metal fixing layer 3 on the back side of the dielectric substrate 1, a metal busbar frame 5 on the outer edge of the FSS lightning shunt functional layer 2, and a metallized via 4 penetrating the dielectric substrate 1. The FSS lightning shunt functional layer 2 and the back metal fixing layer 3 are connected through the metallized via 4. The dielectric substrate 1 is an epoxy glass fiber composite material board with a thickness of 1mm to 3mm, a real part of a dielectric constant of 2.0 to 4.0, a loss tangent of less than 0.01, and a glass transition temperature greater than or equal to 170℃. The metal thickness of the FSS lightning shunt functional layer 2 is 120μm to 200μm. The FSS lightning shunt functional layer 2 is composed of periodically arranged quadrangular star-shaped metal resonant units. The quadrangular star-shaped metal resonant units are arranged in a planar array on the front side of the dielectric substrate 1 with a period of 18mm to 22mm. The diameter of the FSS lightning shunt functional layer 2 is 22 mm, and the gap width between two adjacent quadrangular star-shaped metal resonator units is 0.1 mm to 0.3 mm. The quadrangular star-shaped metal resonator unit has a quadrangular star-shaped cross structure with four branches arranged in a cross shape. The root width of the four branches is 3.0 mm to 5.0 mm, and the length of the four branches is 19.6 mm to 19.9 mm. The operating frequency band of the FSS lightning shunt functional layer 2 is 9.4 GHz to 12 GHz, and the in-band insertion loss of the FSS lightning shunt functional layer 2 is less than or equal to 19.4 GHz. 0.5dB, the out-of-band suppression of the FSS lightning shunt functional layer 2 is greater than or equal to 20dB; the metal thickness of the back metal fixing layer 3 is 120μm~160μm; the back metal fixing layer 3 is a circular metal sheet, the axis of the circular metal sheet is aligned with the geometric center of the four-pointed star metal resonator unit in the thickness direction of the dielectric substrate 1, the radius of the circular metal sheet is 1.2mm~2.0mm, the circular metal sheet is located on the back of the dielectric substrate 1 and corresponds to the position of the four-pointed star metal resonator unit; metallization process Hole 4 is perpendicularly disposed along the thickness direction of dielectric substrate 1. The upper end of the metallized via 4 is connected to the geometric center of the quadrangular star metal resonant unit, and the lower end of the metallized via 4 is connected to the axis of the back metal fixing layer 3. The radius of the metallized via 4 is 0.8mm~1.0mm, the copper plating thickness of the hole wall of the metallized via 4 is 25μm~35μm, and the metallized via 4 is arranged in an equally spaced array on dielectric substrate 1. The center distance between two adjacent metallized via 4 is the same as the array period of the quadrangular star metal resonant unit.

[0029] Example 4 The frequency-selective surface radome structure with lightning protection capability proposed in this embodiment is as follows: Figure 1 , 2As shown, the device includes a dielectric substrate 1, an FSS lightning shunt functional layer 2 on the front side of the dielectric substrate 1, a back metal fixing layer 3 on the back side of the dielectric substrate 1, a metal busbar frame 5 on the outer edge of the FSS lightning shunt functional layer 2, and a metallized via 4 penetrating the dielectric substrate 1. The FSS lightning shunt functional layer 2 and the back metal fixing layer 3 are connected through the metallized via 4. The dielectric substrate 1 is an epoxy glass fiber composite material board with a thickness of 1 mm. The dielectric substrate 1 has a dielectric constant of 2.0 to 4.0 with a thickness of ~3mm, and a loss tangent of less than 0.01. The glass transition temperature of the dielectric substrate 1 is greater than or equal to 170℃. The metal thickness of the FSS lightning shunt functional layer 2 is 120μm to 200μm. The FSS lightning shunt functional layer 2 is composed of periodically arranged quadrangular star-shaped metal resonant units. These units are arranged in a planar array on the front side of the dielectric substrate 1 with a period of 18mm to 22mm. The gap between adjacent quadrangular star-shaped metal resonant units is wide. The thickness is 0.1mm~0.3mm; the four-pointed star-shaped metal resonator unit has a four-pointed star-shaped cross structure with four branches arranged in a cross shape. The root width of the four branches is 3.0mm~5.0mm, and the length of the four branches is 19.6mm~19.9mm; the operating frequency band of the FSS lightning shunt functional layer 2 is 9.4GHz~12GHz, the in-band insertion loss of the FSS lightning shunt functional layer 2 is less than or equal to 0.5dB, and the out-of-band suppression of the FSS lightning shunt functional layer 2 is greater than or equal to 20dB; the metal thickness of the back metal fixing layer 3 is 120μm~160μm. m; The back metal fixing layer 3 is a circular metal sheet. The axis of the circular metal sheet is aligned with the geometric center of the four-pointed star metal resonator unit in the thickness direction of the dielectric substrate 1. The radius of the circular metal sheet is 1.2mm~2.0mm. The circular metal sheet is located on the back of the dielectric substrate 1 and corresponds to the position of the four-pointed star metal resonator unit. The metallized via 4 is perpendicularly disposed along the thickness direction of the dielectric substrate 1. The upper end of the metallized via 4 is connected to the geometric center of the four-pointed star metal resonator unit, and the lower end of the metallized via 4 is connected to the axis of the back metal fixing layer 3. The radius of the metallized via 4 is 0. The metallized vias 4 have a wall copper plating thickness of 25μm~35μm and a diameter of 8mm~1.0mm. The metallized vias 4 are arranged in an equally spaced array on the dielectric substrate 1. The center-to-center distance between two adjacent metallized vias 4 is the same as the array period of the four-corner star-shaped metal resonant unit. The metal bus frame 5 is a continuous metal ring structure with a width of 20mm~25mm. It is located around the outermost edge of the FSS lightning shunt functional layer 2. The inner edge of the metal bus frame 5 is connected to the outer edge of the outermost FSS lightning shunt functional layer 2 to form a leakage path, and is connected to the outermost four-corner star-shaped metal resonant unit.

[0030] Example 5 The frequency selective surface radome structure with lightning protection capability proposed in this embodiment includes a dielectric substrate 1, an FSS lightning shunt functional layer 2, a back metal fixing layer 3, a metallized via 4, and a metal bus frame 5. In this embodiment, the dielectric substrate 1 is made of FR-4 epoxy fiberglass board with a thickness of 2mm and a dielectric constant ε. =3.0, loss tangent tanδ=0.008, plate Tg≥170℃, meeting the temperature resistance requirements of airborne environment; The FSS lightning shunt functional layer 2 is printed on the upper surface of the dielectric substrate 1. It consists of periodically arranged quadrangular cross-shaped metal resonant units with a unit period of 20 mm, a cross arm length of 19.9 mm, and a base width of 3 mm. The gap width between units is 0.2 mm. The operating frequency band is 9.4 GHz to 12 GHz, with in-band insertion loss ≤ 0.5 dB and out-of-band rejection ≥ 20 dB. The copper thickness of the front metal layer is 4 oz (approximately 140 μm). A continuous metal busbar frame 5 with a width of 20mm is set on the outer edge of the FSS lightning shunt functional layer 2. The outermost ring of resonant units are electrically connected to the busbar frame 5 to form an in-plane distributed discharge network. The back metal fixing layer 3 is printed on the lower surface of the dielectric substrate 1, and the copper thickness is also 4oz, which is used to fix the metal sheet. Metallized vias 4 are disposed through the dielectric substrate 1 along the thickness direction, with a radius of 1 mm and a copper plating thickness of 30 μm on the via wall; the metallized vias 4 are disposed at the center of the FSS resonant unit, arranged in an equally spaced array, with the center-to-center distance between adjacent vias being a single cycle distance; the upper end of the metallized vias 4 is electrically connected to the FSS lightning shunt functional layer 2, and the lower end is electrically connected to the back metal fixing layer 3, forming a continuous conductive path through both sides; The lightning discharge path in this embodiment is as follows: when the lightning current hits the front of the radome, the current is first quickly dispersed to the metal busbar frame 5 through the front FSS lightning shunt functional layer 2, and then discharged to the radome frame grounding system through the installation interface of the frame grounding layer, thus completing the safe conduction of the lightning current.

[0031] Example 6 The method for fabricating a frequency-selective surface radome structure with lightning protection capability proposed in this embodiment includes the following steps: Step 1: Take a double-sided copper-clad dielectric substrate 1 and process through holes on the dielectric substrate 1; Step 2: Perform hole metallization treatment on the through hole to form a metallized via 4 inside the through hole; Step 3: Fabricate an FSS lightning shunt functional layer 2 and a metal bus frame 5 on the front side of the dielectric substrate 1, and fabricate a back metal fixing layer 3 on the back side of the dielectric substrate 1.

[0032] Example 7 The method for fabricating a frequency-selective surface radome structure with lightning protection capability proposed in this embodiment includes the following steps: Step 1: Take a double-sided copper-clad dielectric substrate 1 and process through holes on the dielectric substrate 1; In step 1, the dielectric substrate 1 is an epoxy glass fiber composite board with a thickness of 1mm to 3mm, a real part of dielectric constant of 2.0 to 4.0, a loss tangent of less than 0.01, and a glass transition temperature of greater than or equal to 170℃; the radius of the through hole is 0.8mm to 1.0mm, and the position of the through hole corresponds one-to-one with the geometric center position of the preset FSS resonant unit; the through hole is machined using a CNC drilling machine, the roughness of the hole wall is controlled to be less than or equal to 10μm, and the burrs at the opening of the through hole are removed; Step 2: Perform hole metallization treatment on the through hole to form a metallized via 4 inside the through hole; In step 2, the via metallization process includes a desmearing process, a palladium activation process, a chemical copper plating process, and a full-board electroplating process performed sequentially. The desmearing process removes the adhesive residue from the via wall. The palladium activation process forms a palladium activation layer on the surface of the via wall. The chemical copper plating process forms a continuous copper seed layer on the via wall. The full-board electroplating process thickens the copper layer on the via wall to 25μm~35μm and forms a metallized via 4 in the via. The metallized via 4 realizes the electrical interconnection between the front copper layer and the back copper layer of the dielectric substrate 1. Step 3: Fabricate the FSS lightning shunt functional layer 2 and the metal bus frame 5 on the front side of the dielectric substrate 1, and fabricate the back metal fixing layer 3 on the back side of the dielectric substrate 1. In step 3, photosensitive dry films are attached to the front and back sides of the dielectric substrate 1, respectively. The FSS resonant unit pattern, the metal bus frame pattern, and the back metal pattern are transferred to the copper foil surface by photolithography exposure and development. The exposed copper foil is removed by acidic copper chloride etching process, retaining the target metal pattern. Then the dry film is removed, and the FSS lightning shunt functional layer 2 and the metal bus frame 5 are formed on the front side, and the back metal fixing layer 3 is formed on the back side. The metal layer thickness of the FSS lightning shunt functional layer 2, the metal bus frame 5, and the back metal fixing layer 3 is 120μm~160μm. It also includes step 4: electroplating silver on the FSS lightning shunt functional layer 2, the metal bus frame 5 on the front side of the dielectric substrate 1 and the back metal fixing layer 3 on the back side; it also includes a finished product inspection process, which includes conducting continuity tests, pattern accuracy tests and insulation resistance tests on the FSS lightning shunt functional layer 2 and the metal bus frame 5.

[0033] Example 8 The method for fabricating a frequency-selective surface radome structure with lightning protection proposed in this embodiment, based on the aforementioned frequency-selective surface radome structure with lightning protection, is implemented using a standard double-sided PCB process and includes the following steps: S1. Substrate preparation: Select a 2mm thick FR-4 epoxy fiberglass substrate, cover both sides with 4oz copper foil, and perform substrate cleaning and surface roughening treatment. S2. CNC drilling: According to the design position, use a CNC drilling machine to machine through holes with a radius of 1mm, control the hole wall roughness to ≤10μm, and remove burrs from the hole opening; S3, Hole Metallization: Sequentially perform adhesive removal, palladium activation, and chemical copper plating to form a continuous copper seed layer on the hole wall. Then, through whole-board electroplating, the hole copper is thickened to 140μm to achieve reliable electrical interconnection of the copper layers on the front and back sides. S4. Pattern Transfer: Photosensitive dry film is applied to both sides, and the FSS resonant unit pattern and the back metal pattern are transferred to the copper foil surface through photolithography exposure and development. S5. Etching and shaping: Using an acidic copper chloride etching process, the exposed copper foil is removed, the target metal pattern is retained, and then the dry film is removed to obtain a complete metal structure on both sides. S6. Surface treatment: Electroplating silver on both sides of the metal layer improves conductivity and corrosion resistance; S7. Finished Product Inspection: Conduct continuity tests, graphic accuracy tests, and insulation resistance tests. Once the tests are passed, the finished product is obtained.

Claims

1. A frequency-selective surface radome structure with lightning protection capability, characterized in that, The device includes a dielectric substrate (1), on the front side of which is provided an FSS lightning shunt functional layer (2), and on the back side of which is provided a back metal fixing layer (3). The outer edge of the FSS lightning shunt functional layer (2) is provided with a metal bus frame (5). Metallized vias (4) are provided through the dielectric substrate (1). The FSS lightning shunt functional layer (2) and the back metal fixing layer (3) are connected through the metallized vias (4).

2. The frequency-selective surface radome structure with lightning protection capability according to claim 1, characterized in that, The dielectric substrate (1) is an epoxy glass fiber composite material board. The thickness of the dielectric substrate (1) is 1 mm to 3 mm. The real part of the dielectric constant of the dielectric substrate (1) is 2.0 to 4.

0. The loss tangent of the dielectric substrate (1) is less than 0.

01. The glass transition temperature of the dielectric substrate (1) is greater than or equal to 170°C.

3. The frequency-selective surface radome structure with lightning protection capability according to claim 2, characterized in that, The metal thickness of the FSS lightning shunt functional layer (2) is 120μm~200μm; the FSS lightning shunt functional layer (2) is composed of periodically arranged quadrangular star-shaped metal resonant units, which are arranged in a planar array on the front side of the dielectric substrate (1) with a period of 18mm~22mm, and the gap width between two adjacent quadrangular star-shaped metal resonant units is 0.1mm~0.3mm; the quadrangular star-shaped metal resonant units are arranged in a planar array with a period of 18mm~22mm. The resonant unit is a four-pointed star-shaped cross structure with four branches arranged in a cross shape. The root width of the four branches is 3.0mm~5.0mm and the length of the four branches is 19.6mm~19.9mm. The operating frequency band of the FSS lightning shunt functional layer (2) is 9.4GHz~12GHz. The in-band insertion loss of the FSS lightning shunt functional layer (2) is less than or equal to 0.5dB and the out-of-band suppression of the FSS lightning shunt functional layer (2) is greater than or equal to 20dB.

4. The frequency-selective surface radome structure with lightning protection capability according to claim 3, characterized in that, The metal thickness of the back metal fixing layer (3) is 120μm~160μm; the back metal fixing layer (3) is a circular metal sheet, the axis of the circular metal sheet is aligned with the geometric center of the quadrangular star metal resonant unit in the thickness direction of the dielectric substrate (1), the radius of the circular metal sheet is 1.2mm~2.0mm, the circular metal sheet is located on the back of the dielectric substrate (1) and corresponds to the position of the quadrangular star metal resonant unit.

5. The frequency-selective surface radome structure with lightning protection capability according to claim 4, characterized in that, The metallized via (4) is perpendicularly disposed along the thickness direction of the dielectric substrate (1). The upper end of the metallized via (4) is connected to the geometric center of the quadrangular star metal resonator unit, and the lower end of the metallized via (4) is connected to the axis of the back metal fixing layer (3). The radius of the metallized via (4) is 0.8mm~1.0mm, and the copper plating thickness of the hole wall of the metallized via (4) is 25μm~35μm. The metallized via (4) is arranged in an equally spaced array on the dielectric substrate (1), and the center distance between two adjacent metallized vias (4) is the same as the array period of the quadrangular star metal resonator unit.

6. The frequency-selective surface radome structure with lightning protection capability according to claim 5, characterized in that, The metal busbar frame (5) is a continuous metal ring structure with a width of 20mm~25mm. It is located around the outermost edge of the FSS lightning shunt functional layer (2). The inner edge of the metal busbar frame (5) is connected to the outer edge of the outermost FSS lightning shunt functional layer (2) to form a leakage path, and is connected to the outermost four-corner star-shaped metal resonant unit.

7. A method for fabricating a frequency-selective surface radome structure with lightning protection capability, characterized in that, The frequency selective surface radome structure with lightning protection capability according to claim 6 includes the following steps: Step 1: Take a double-sided copper-clad dielectric substrate (1) and process through holes on the dielectric substrate (1); Step 2: Perform hole metallization treatment on the through hole to form a metallized via (4) in the through hole. Step 3: FSS lightning shunt functional layer (2) and metal bus frame (5) are fabricated on the front side of the dielectric substrate (1), and a back metal fixing layer (3) is fabricated on the back side of the dielectric substrate (1).

8. The method for preparing a frequency-selective surface radome structure with lightning protection capability according to claim 7, characterized in that, In step 1, the dielectric substrate (1) is an epoxy glass fiber composite material board with a thickness of 1mm to 3mm, a real part of dielectric constant of 2.0 to 4.0, a loss tangent of less than 0.01, and a glass transition temperature of greater than or equal to 170℃; the radius of the through hole is 0.8mm to 1.0mm, and the position of the through hole corresponds one-to-one with the geometric center position of the preset FSS resonant unit; the through hole is machined using a CNC drilling machine, the roughness of the hole wall is controlled to be less than or equal to 10μm, and the burrs at the opening of the through hole are removed.

9. The method for preparing a frequency-selective surface radome structure with lightning protection capability according to claim 7, characterized in that, In step 2, the via metallization process includes a desmearing process, a palladium activation process, a chemical copper plating process, and a full-board electroplating process performed sequentially. The desmearing process removes the adhesive residue from the wall of the via. The palladium activation process forms a palladium activation layer on the surface of the wall of the via. The chemical copper plating process forms a continuous copper seed layer on the wall of the via. The full-board electroplating process thickens the copper layer on the wall of the via to 25μm~35μm and forms the metallized via (4) in the via. The metallized via (4) realizes the electrical interconnection between the front copper layer and the back copper layer of the dielectric substrate (1).

10. The method for preparing a frequency-selective surface radome structure with lightning protection capability according to claim 7, characterized in that, In step 3, photosensitive dry films are attached to the front and back sides of the dielectric substrate (1), and the FSS resonant unit pattern, metal bus border pattern and back metal pattern are transferred to the copper foil surface by photolithography exposure and development. The exposed copper foil is removed by acidic copper chloride etching process, the target metal pattern is retained, and then the dry film is removed. The FSS lightning shunt functional layer (2) and the metal bus border (5) are formed on the front side, and the back metal fixing layer (3) is formed on the back side. The metal layer thickness of the FSS lightning shunt functional layer (2), the metal bus border (5) and the back metal fixing layer (3) is 120μm~160μm. It also includes step 4: electroplating silver onto the FSS lightning shunt functional layer (2) on the front side of the dielectric substrate (1), the metal bus frame (5), and the back metal fixing layer (3) on the back side; it also includes a finished product inspection process, which includes conducting continuity tests, pattern accuracy tests, and insulation resistance tests on the FSS lightning shunt functional layer (2) and the metal bus frame (5).

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