A 2.5D large-angle stable bandpass frequency selective surface structure

Abstract

This invention provides a 2.5D large-angle stable bandpass frequency selective surface structure, comprising, from bottom to top, a first dielectric substrate, a second dielectric substrate, a third dielectric substrate, a fourth dielectric substrate, a fifth dielectric substrate, and a sixth dielectric substrate. Interdigitated capacitor layers are printed on the upper and lower surfaces of the first dielectric substrate, respectively. A metal strip layer is printed on the upper surface of the third dielectric substrate, and an I-shaped metal patch layer is printed on its lower surface. An I-shaped metal patch layer is printed on the upper surface of the fourth dielectric substrate. Interdigitated capacitor layers are printed on the upper and lower surfaces of the sixth dielectric substrate. A semi-cured adhesive sheet is disposed between each dielectric substrate for interlayer bonding. The invention also includes metallized vias that penetrate the third dielectric substrate, the fourth dielectric substrate, and the semi-cured adhesive sheet between the two dielectric substrates. This 2.5D large-angle stable bandpass frequency selective surface structure of the invention balances large-angle stability and high selectivity.

Description

Technical Field

[0001] This invention relates to the field of microwave technology, and in particular to a 2.5D large-angle stable bandpass frequency selective surface structure, suitable for airborne or shipborne radome systems requiring large-angle stable filtering characteristics. Background Technology

[0002] A Frequency Selective Surface (FSS) is a spatial filter composed of periodically arranged metallic resonant elements, capable of selectively transmitting or reflecting electromagnetic waves in a specific frequency band. In practical applications, the incident angles of electromagnetic waves are often diverse and uncertain, while modern radar systems have increasingly demanding performance requirements under large-angle incident waves. This necessitates that FSSs maintain a stable frequency response and possess steep filtering edges even under large-angle oblique incidence conditions. Traditional FSSs often exhibit passband drift and selectivity degradation under large-angle oblique incidence, severely limiting their reliable application in various scenarios. Summary of the Invention

[0003] This application provides a 2.5D large-angle stable bandpass frequency selective surface structure to solve the problems in the background art.

[0004] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.

[0005] According to a first aspect of the present application, a 2.5D large-angle stable bandpass frequency selective surface structure is provided, comprising a first dielectric substrate, a second dielectric substrate, a third dielectric substrate, a fourth dielectric substrate, a fifth dielectric substrate, and a sixth dielectric substrate arranged sequentially from bottom to top; interdigitated capacitor layers are printed on the upper and lower surfaces of the first dielectric substrate; a metal strip layer is printed on the upper surface of the third dielectric substrate, and an I-shaped metal patch layer is printed on the lower surface; an I-shaped metal patch layer is printed on the upper surface of the fourth dielectric substrate; interdigitated capacitor layers are printed on the upper and lower surfaces of the sixth dielectric substrate; a semi-cured adhesive sheet is disposed between each dielectric substrate for interlayer lamination; and a metallized via is further included, the metallized via penetrating the third dielectric substrate, the fourth dielectric substrate, and the semi-cured adhesive sheet between the two dielectric substrates.

[0006] According to one embodiment of this application, the upper and lower surfaces of the first dielectric substrate, the second dielectric substrate, the third dielectric substrate, the fourth dielectric substrate, the fifth dielectric substrate, and the sixth dielectric substrate are all squares with equal side lengths, and the first dielectric substrate and the second dielectric substrate have the same thickness, the second dielectric substrate and the fifth dielectric substrate have the same thickness, and the third dielectric substrate and the fourth dielectric substrate have the same thickness.

[0007] According to one embodiment of this application, the interdigitated capacitor layer includes two sets of nested comb-shaped metal structures, which are placed opposite each other and form a bend line gap between the teeth.

[0008] According to one embodiment of this application, the I-shaped metal patch layer is formed by combining a first rectangular metal patch running longitudinally and two second rectangular metal patches located at its ends and perpendicular to it.

[0009] According to one embodiment of this application, the I-shaped metal patch layer is placed in the center, and its geometric center coincides with the center of the dielectric substrate surface, and its overall length is less than the surface side length of the dielectric substrate.

[0010] According to one embodiment of this application, the metal strip layer is formed by combining a longitudinal rectangular metal strip and a square metal patch located at the center.

[0011] According to one embodiment of this application, the length of the rectangular metal strip is equal to the side length of the surface of the dielectric substrate; the side length of the square metal patch is greater than the width of the rectangular metal strip.

[0012] According to one embodiment of this application, the side length of the semi-cured adhesive sheet is the same as that of the dielectric substrate, and it is made of WL-PP280 material with a relative permittivity of 2.74 and a loss tangent of 0.0017.

[0013] According to one embodiment of this application, the diameter of the metallized via is smaller than the width of the first rectangular metal patch in the T-shaped metal patch layer and the side length of the square metal patch in the metal strip layer.

[0014] According to one embodiment of this application, the metallized via axis coincides with the center of each layer.

[0015] Compared with existing technologies, the beneficial effects of adopting the above technical solution are as follows: 1. By designing an interdigital capacitor layer to increase its equivalent capacitance, the FSS can significantly reduce the unit size and improve the structural compactness while maintaining the target resonant frequency, thereby improving the angular stability of the FSS under TE polarization.

[0016] 2. By cascading multiple interdigital capacitor layers and "I"-shaped metal patch layers, the out-of-band steepness is improved and high-frequency out-of-band harmonics are effectively suppressed, giving FSS both excellent selectivity and wide stopband performance.

[0017] 3. By adding metallized vias in the vertical direction to increase additional current paths and form additional inductance in the vertical direction, the sensitivity of LC resonance in TM mode to changes in incident angle can be reduced, and the angular stability under TM polarization can be improved.

[0018] 4. The 2.5D large-angle stable bandpass frequency selective surface structure provided by this invention operates in the 0-18GHz frequency band. Under x-polarization, the passband characteristics of this FSS in the 5-6GHz frequency range remain good under oblique incidence at 0-35° elevation angles and 0-60° azimuth angles, and |S21| is consistently less than -20dB in the 0-3GHz and 10-18GHz frequency ranges. Under y-polarization, the FSS consistently maintains |S21| < -20dB under oblique incidence at 0-35° elevation angles and 0-60° azimuth angles, exhibiting full-impedance performance. This frequency selective surface has the advantages of large-angle stability, high selectivity, and excellent out-of-band suppression capability. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0020] Figure 1 This is a schematic diagram of the 2.5D large-angle stable bandpass frequency selection surface structure according to an embodiment of this application.

[0021] Figure 2 This is a schematic diagram of the interdigital capacitor layer structure of the 2.5D large-angle stable bandpass frequency selective surface structure according to an embodiment of this application.

[0022] Figure 3 This is a schematic diagram of the I-shaped metal patch layer structure of the 2.5D large-angle stable bandpass frequency selective surface structure according to an embodiment of this application.

[0023] Figure 4 This is a schematic diagram of the metal strip layer structure of the 2.5D large-angle stable bandpass frequency selective surface structure according to an embodiment of this application.

[0024] Figure 5 This is a schematic diagram of the metallized vias and the metal layer, dielectric substrate, and prepreg bonding sheet structure that the vias penetrate through in the 2.5D large-angle stable bandpass frequency selective surface structure of this application embodiment.

[0025] Figure 6 This is a diagram showing the main dimensions of the 2.5D large-angle stable bandpass frequency selection surface structure according to an embodiment of this application.

[0026] Figure 7 This is a diagram showing the main dimensions of the interdigital capacitor layer of the 2.5D large-angle stable bandpass frequency selective surface structure according to an embodiment of this application.

[0027] Figure 8 This is a diagram showing the main dimensions of the I-shaped metal patch layer of the 2.5D large-angle stable bandpass frequency selective surface structure according to an embodiment of this application.

[0028] Figure 9 This is a diagram showing the main dimensions of the metal strip layer in the 2.5D large-angle stable bandpass frequency selective surface structure of this application embodiment.

[0029] Figure 10 This is a diagram showing the main dimensions of the metallized vias and the metal layer, dielectric substrate, and prepreg bonded sheet that the 2.5D large-angle stable bandpass frequency selective surface structure of this application embodiment penetrates.

[0030] Figure 11 For the 2.5D large-angle stable bandpass frequency selection of the surface structure in the embodiments of this application, the x-polarization and |S| at 0-35° pitch angles are selected. 21 Simulation result diagram.

[0031] Figure 12 For the 2.5D large-angle stable bandpass frequency selection of the surface structure in the embodiments of this application, the x-polarization and |S| at 0-60° azimuth angles are selected. 21 Simulation result diagram.

[0032] Figure 13 For the 2.5D large-angle stable bandpass frequency selection of the embodiments of this application, the surface structure's y-polarization and |S| at 0-35° pitch angles are selected. 21 Simulation result diagram.

[0033] Figure 14 For the 2.5D large-angle stable bandpass frequency selection of the surface structure in the embodiments of this application, the y-polarization and |S| at 0-60° azimuth angles are selected. 21 Simulation result diagram.

[0034] Among them, 100-interdigitated capacitor layer, 101-comb-shaped metal structure, 102-bending line gap, 200-I-shaped metal patch layer, 201-first rectangular metal patch, 202-second rectangular metal patch, 300-metal strip layer, 301-rectangular metal strip, 302-square metal patch, 400-metallized via, 10-first dielectric substrate, 20-second dielectric substrate, 30-third dielectric substrate, 40-fourth dielectric substrate, 50-fifth dielectric substrate, 60-sixth dielectric substrate, 70-prepreg adhesive sheet. Detailed Implementation

[0035] The embodiments of this application are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar modules or modules having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. Rather, the embodiments of this application include all variations, modifications, and equivalents falling within the spirit and scope of the appended claims.

[0036] To address the shortcomings of the prior art, this application provides a 2.5D large-angle stable bandpass frequency selective surface structure. It adopts an interdigital capacitor structure to achieve miniaturization of the unit, and through the cascading of multiple metal layers and the metallized vias 400 in the vertical direction, the frequency selective surface achieves both large-angle stability and high selectivity.

[0037] Please refer to Figure 1 The 2.5D large-angle stable bandpass frequency selective surface structure includes, from bottom to top, a first dielectric substrate 10, a second dielectric substrate 20, a third dielectric substrate 30, a fourth dielectric substrate 40, a fifth dielectric substrate 50, and a sixth dielectric substrate 60. The first dielectric substrate 10 has interdigitated capacitor layers 100 printed on its upper and lower surfaces, respectively. The second dielectric substrate 20 has no metal layers on either its upper or lower surfaces. The third dielectric substrate 30 has a metal strip layer 300 printed on its upper surface and an I-shaped metal patch layer 200 printed on its lower surface. The fourth dielectric substrate 40 has an I-shaped metal patch layer 200 printed on its upper surface and no metal layer on its lower surface. The fifth dielectric substrate 50 has no metal layers on either its upper or lower surfaces. The sixth dielectric substrate 60 has interdigitated capacitor layers 100 printed on both its upper and lower surfaces. Semi-cured adhesive sheets 70 are placed between the dielectric substrates, and the substrates are stacked by interlayer lamination. During lamination, the dielectric substrates and semi-cured adhesive sheets 70 are aligned vertically. The structure also includes a metallized via 400, which penetrates the third dielectric substrate 30, the fourth dielectric substrate 40, and the semi-cured adhesive sheet 70 between the two dielectric substrates.

[0038] Furthermore, the upper and lower surfaces of the first dielectric substrate 10, the second dielectric substrate 20, the third dielectric substrate 30, the fourth dielectric substrate 40, the fifth dielectric substrate 50, and the sixth dielectric substrate 60 are all squares with equal side lengths, and the first dielectric substrate 10 and the second dielectric substrate 20 have the same thickness, the second dielectric substrate 20 and the fifth dielectric substrate 50 have the same thickness, and the third dielectric substrate 30 and the fourth dielectric substrate 40 have the same thickness.

[0039] In one embodiment, the first dielectric substrate 10, the second dielectric substrate 20, the third dielectric substrate 30, the fourth dielectric substrate 40, the fifth dielectric substrate 50, and the sixth dielectric substrate 60 are all made of the same material, namely F4BME265 board, with a relative permittivity of 2.65 and a loss tangent of 0.0013; the semi-cured adhesive sheet 70 is made of WL-PP280 material, with a relative permittivity of 2.74 and a loss tangent of 0.0017.

[0040] Please refer to Figure 6 In one embodiment, the overall height H of the frequency selective surface structure is 3.793 mm, the side length L of each dielectric substrate is 2.25 mm, the thickness h1 of the first dielectric substrate 10 and the sixth dielectric substrate 60 is 0.254 mm; the thickness h2 of the second dielectric substrate 20 and the fifth dielectric substrate 50 is 0.254 mm; the thickness h3 of the third dielectric substrate 30 and the fourth dielectric substrate 40 is 1.016 mm; the thickness h4 of the semi-cured adhesive sheet 70 is 0.1 mm; and the thickness of each metal layer is 0.035 mm.

[0041] Please refer to Figure 2 In this embodiment, the interdigitated capacitor layer 100 includes two sets of nested comb-shaped metal structures 101, wherein the two sets of comb-shaped metal structures 101 are placed opposite each other in an alternating manner, with bent line gaps 102 formed between the teeth. Each comb-shaped metal structure 101 consists of multiple longitudinally extending comb strips and a transverse busbar, with the busbar located on opposite sides of the unit and not directly connected to each other. Please continue to refer to... Figure 7 The diagram shows the specific design dimensions of the interdigital capacitor layer 100 in this embodiment of the application, wherein the width a1 of the bend line gap 102102 is 0.22 mm, the length a3 is 1.82 mm, and the width a2 of the comb tooth is 0.28 mm.

[0042] Please check Figure 3 In this embodiment, the I-shaped metal patch layer 200 is formed by combining a longitudinally extending first rectangular metal patch 201 and two second rectangular metal patches 202 located at its ends and perpendicular to it. Furthermore, the I-shaped metal patch layer 200 is centrally placed on the surface of the dielectric substrate, with its geometric center coinciding with the center of the dielectric substrate surface, and its overall length is less than the surface side length of the dielectric substrate. Please refer to... Figure 8 The diagram shows the main dimensions of the I-shaped metal patch layer 200200 according to an embodiment of this application. The first rectangular metal patch 201201 in the longitudinal direction has a length b1 of 1.4 mm and a width b2 of 0.75 mm. The second rectangular metal patch 202202 in the transverse direction has a length b3 of 1.4 mm and a width b4 of 0.3 mm.

[0043] Please refer to Figure 4In this embodiment, the metal strip layer 300 is formed by combining a longitudinally oriented rectangular metal strip 301 and a centrally located square metal patch 302. Further, the length of the rectangular metal strip 301 is equal to the side length of the dielectric substrate surface; the side length of the square metal patch 302 is greater than the width of the rectangular metal strip 301. The centers of the rectangular metal strip 301 and the square metal patch 302 coincide with the center of the dielectric substrate. Please refer to... Figure 9 The diagram shows the main dimensions of the metal strip layer 300 in this embodiment of the application: the width c1 of the longitudinal rectangular metal strip 301301 is 0.36 mm; and the side length c2 of the central square metal patch 302302 is 0.75 mm.

[0044] Please refer to Figure 5 In this embodiment, the metallized via 400 penetrates the third dielectric substrate 30, on both sides of which are respectively printed with an I-shaped metal patch layer 200 and a metal strip layer 300, the fourth dielectric substrate 40, on one side of which is printed with an I-shaped metal patch layer 200, and the semi-cured adhesive sheet 70 between the two dielectric substrates; the diameter of the metallized via 400 is slightly smaller than the width of the first rectangular metal patch 201 in the I-shaped metal patch layer 200 and the side length of the square metal patch 302 in the metal strip layer 300, and the axis of the metallized via 400 coincides with the center of each layer. Please refer to... Figure 10 The diagram shows the main dimensions of the metallized via 400 of this application embodiment, as well as the two I-shaped metal patches, one metal strip layer 300, two third dielectric substrates 30 and the prepreg adhesive sheet 70 that it penetrates. The axis of the cylindrical metallized via 400 coincides with the center of each layer. The bottom diameter D of the metallized via 400 is 0.5 mm and the height H0 is 2.237 mm.

[0045] Please refer to Figure 11 , Figure 12 The diagrams illustrate the x-polarization, 0-35° pitch angle, and 0-60° azimuth angle of the 2.5D large-angle stable bandpass frequency selective surface according to embodiments of this application, along with their respective |S| values. 21 The simulation results show that, under x-polarization, the FSS maintains good passband characteristics in the 5-6 GHz frequency range with good incidence at 0-35° elevation angles and 0-60° azimuth angles. 21 | It drops to -20dB at 3GHz and 10GHz, and remains below -20dB in the 0-3GHz and 10-18GHz frequency ranges.

[0046] Please refer to Figure 13 , Figure 14 The diagrams illustrate the y-polarization of the 2.5D large-angle stable bandpass frequency selective surface according to embodiments of this application, and the |S| at elevation angles of 0-35° and azimuth angles of 0-60°. 21The simulation results show that under y-polarization, the FSS maintains its constant |S| under oblique incidence at elevation angles of 0-35° and azimuth angles of 0-60°. 21 |<-20dB, with full resistance performance.

[0047] The simulation results above show that the frequency-selective surface structure has the advantages of bandpass performance, large-angle stability, high selectivity, and excellent out-of-band suppression capability.

[0048] It should be noted that, in the description of the embodiments of this application, unless otherwise expressly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The accompanying drawings in the embodiments are used to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0049] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A 2.5D large-angle stable bandpass frequency selective surface structure, characterized in that, It includes a first dielectric substrate, a second dielectric substrate, a third dielectric substrate, a fourth dielectric substrate, a fifth dielectric substrate, and a sixth dielectric substrate arranged sequentially from bottom to top; The first dielectric substrate has interdigitated capacitor layers printed on its upper and lower surfaces, respectively; the third dielectric substrate has a metal strip layer printed on its upper surface and an I-shaped metal patch layer printed on its lower surface; the fourth dielectric substrate has an I-shaped metal patch layer printed on its upper surface; the sixth dielectric substrate has interdigitated capacitor layers printed on its upper and lower surfaces; a semi-cured adhesive sheet is disposed between each dielectric substrate for interlayer lamination; and the substrate also includes metallized vias that penetrate the third dielectric substrate, the fourth dielectric substrate, and the semi-cured adhesive sheet between the two dielectric substrates.

2. The 2.5D large-angle stable bandpass frequency selective surface structure according to claim 1, characterized in that, The upper and lower surfaces of the first dielectric substrate, the second dielectric substrate, the third dielectric substrate, the fourth dielectric substrate, the fifth dielectric substrate, and the sixth dielectric substrate are all squares with equal side lengths. The first dielectric substrate and the second dielectric substrate have the same thickness, the second dielectric substrate and the fifth dielectric substrate have the same thickness, and the third dielectric substrate and the fourth dielectric substrate have the same thickness.

3. The 2.5D large-angle stable bandpass frequency selective surface structure according to claim 1, characterized in that, The interdigitated capacitor layer includes two sets of nested comb-shaped metal structures. The two sets of comb-shaped metal structures are placed opposite each other and interlaced, with bent line gaps formed between the teeth.

4. The 2.5D large-angle stable bandpass frequency selective surface structure according to claim 1, characterized in that, The I-shaped metal patch layer is formed by combining a first rectangular metal patch running longitudinally and two second rectangular metal patches located at its two ends and perpendicular to it.

5. The 2.5D large-angle stable bandpass frequency selective surface structure according to claim 4, characterized in that, The I-shaped metal patch layer is placed in the center, and its geometric center coincides with the center of the dielectric substrate surface. Its overall length is less than the surface side length of the dielectric substrate.

6. The 2.5D large-angle stable bandpass frequency selective surface structure according to claim 4, characterized in that, The metal strip layer is formed by combining longitudinal rectangular metal strips and a centrally located square metal patch.

7. The 2.5D large-angle stable bandpass frequency selective surface structure according to claim 6, characterized in that, The length of the rectangular metal strip is equal to the side length of the dielectric substrate; the side length of the square metal patch is greater than the width of the rectangular metal strip.

8. The 2.5D large-angle stable bandpass frequency selective surface structure according to claim 1, characterized in that, The side length of the semi-cured adhesive sheet is the same as that of the dielectric substrate. It is made of WL-PP280 material with a relative permittivity of 2.74 and a loss tangent of 0.0017.

9. The 2.5D large-angle stable bandpass frequency selective surface structure according to claim 6, characterized in that, The diameter of the metallized via is smaller than the width of the first rectangular metal patch in the T-shaped metal patch layer and the side length of the square metal patch in the metal strip layer.

10. The 2.5D large-angle stable bandpass frequency selective surface structure according to claim 9, characterized in that, The metallized via axis coincides with the center of each layer.

Images