High-angle-stability frequency selective surface with adjustable double-frequency wave-transparent window

Abstract

The invention discloses a high-angle stable frequency selective surface with an adjustable dual-frequency wave-transparent window. The frequency selective surface comprises a metal resonant structure, a dielectric substrate and a bottom-layer metal feed structure, the top metal resonant structure comprises a crossed dipole with an arc-shaped branch knot, an arc-shaped metal ring with a bent branch knot, and a square patch with an inner concave fillet at the periphery; the first variable capacitance diode is welded between the arc-shaped branch knot and the bent branch knot, and the second variable capacitance diode is welded between the patch and the arc-shaped metal ring; the bottom layer metal feed structure comprises a cross metal feed line and a T-shaped metal feed line, and lumped resistors are loaded between the feed lines to form a complete direct current power supply network; the upper surface and the lower surface of the dielectric substrate are communicated through metal via holes in the vertical direction, so that the bottom feeder line can provide reverse bias voltage for independently regulating and controlling the passband resonant frequency for the two sets of variable capacitance diodes on the top layer. According to the invention, the number of adopted active devices is small, and the antenna has the advantages of double-frequency independence, continuous adjustability and high-angle stability.

Description

Technical Field

[0001] The invention belongs to the field of electromagnetic field and microwave technology, and in particular relates to a frequency selective surface with an adjustable dual-frequency wave-transmitting window and high-angle stability. Background Art

[0002] Frequency Selective Surface (FSS) is usually a two-dimensional periodic array structure, which has a specific selection function for the working frequency, polarization form, incident angle, etc. of electromagnetic waves, and can effectively control the reflection and transmission of electromagnetic waves. Due to its unique spatial filtering properties, frequency selective surfaces are widely used in radar stealth, electromagnetic compatibility, wireless communication, electronic countermeasures and other fields.

[0003] In order to overcome the defect of the traditional passive frequency selective surface that the resonance characteristics remain unchanged after processing, active devices (such as PIN diodes, varactor diodes, etc.) are loaded in the FSS structure to adapt to the complex and changeable electromagnetic environment. Due to the advantages of varactor diodes such as short response time, wide tuning range, small size and low cost, adjustable frequency selective surfaces based on varactor diodes have gradually become a research hotspot in recent years. Adjustable frequency selective surfaces can not only solve the in-band stealth problem of antenna covers, but also provide tuning solutions for absorbing materials, electromagnetic shielding materials, active phased array radars, beam steering antennas, etc., and have broad application prospects.

[0004] Dual-band FSS has a wide range of applications in the fields of MIMO antennas and multi-band communication systems, and has received extensive attention in the past few years. However, there are relatively few studies on dual-band adjustable FSS. On the one hand, the bias network that provides bias voltage for the varactor will affect the electromagnetic characteristics of the adjustable frequency selective surface, and the complexity of the feed line increases the design difficulty of the independently adjustable dual-passband FSS design. On the other hand, in order to achieve independent tuning of the dual-band wave-transmitting window, multiple varactor diode elements are required. The active FSS structure proposed in the relevant literature currently requires 16 varactor diode elements in one periodic unit. If they are arranged into an array structure, the number of active devices is huge; too many active elements increase the processing complexity and cost. In addition, when the electromagnetic wave is incident at a large angle, the resonant frequency of the frequency selective surface will shift. In order to meet the actual application requirements of engineering fields such as conformal radar antenna covers, further research is needed on how to achieve stable wave transmission performance.

[0005] Purpose of the Invention

[0006] In view of the defects of the prior art and the application requirements of broadband, ultra-wideband, multi-frequency and frequency conversion in current military radar, modern communications and other fields, the present invention provides a high-angle stable dual-frequency wave-transmitting window with an adjustable frequency selective surface to achieve independent tuning of the dual frequencies, thereby improving the stability at large incident angles while reducing the number of active devices.

[0007] In order to achieve the above tasks, the present invention adopts the following technical solutions:

[0008] A high-angle stable dual-frequency wave-transmitting window continuously adjustable frequency selective surface, comprising: a dielectric substrate, on which frequency selective units of a square structure are distributed;

[0009] Each frequency selection unit includes a top metal resonant structure arranged on the upper surface of the dielectric substrate, a bottom metal feeding structure arranged on the lower surface of the dielectric substrate, an active device, and a first metal via and a second metal via connecting the upper and lower surfaces, wherein:

[0010] The top metal resonance structure is a centrally symmetrical structure, comprising: a cross dipole with arc-shaped branches, an arc-shaped metal ring with bent branches, and a square patch with inner concave rounded corners on all sides; the arc-shaped metal rings are distributed around the square patch, the ends of adjacent arc-shaped metal rings are connected, the bent branches are connected to the outside of the arc-shaped metal rings, and the cross dipoles are arranged on the outside of the bent branches; the arc-shaped metal rings of adjacent frequency selection units are connected to each other, and the cross dipoles of adjacent frequency selection units are connected to each other;

[0011] The bottom metal feeding structure includes: a cross metal feed line and a T-shaped metal feed line; the cross metal feed line is connected to a square patch on the upper surface of a dielectric substrate through a first metal via hole, and the first metal via hole is located at the center of a frequency selection unit; the T-shaped metal feed line is distributed around the cross metal feed line and the ends are connected to each other; the T-shaped metal feed line is connected to a cross dipole on the upper surface of a dielectric substrate through a second metal via hole, and the second metal via hole is located at the four corners of the frequency selection unit; there is a first gap between each T-shaped metal feed line and the cross metal feed line, and a second gap is left near the two ends of each T-shaped metal feed line; the T-shaped metal feed lines of adjacent frequency selection units are connected to each other to form a cross-shaped structure; a lumped resistor is provided in part of the first gap and the second gap;

[0012] The active device includes a first varactor diode and a second varactor diode; the positive electrode of the first varactor diode is connected to the arc-shaped branch of the top metal resonant structure, and the negative electrode is connected to the bent branch; the positive electrode of the second varactor diode is connected to the corner of the square patch, and the negative electrode is connected to the end connection of the adjacent arc-shaped metal ring.

[0013] Furthermore, the positive electrode of a DC power supply is used to connect the arc-shaped metal ring; the negative electrode of the DC power supply is connected to the cross metal feeder at the center of the frequency selection unit, and a reverse bias voltage is provided to the square patch through the first metal via; the other negative electrode of the DC power supply is connected to the T-shaped metal feeder, and another reverse bias voltage is provided to the cross dipole through the second metal via; the change of the variable capacitance value of the active device is controlled by changing the bias voltage, thereby independently regulating the dual working frequency bands of the adjustable frequency selection surface, thereby realizing the broadband reconfigurable function of the wave-transmitting window.

[0014] Furthermore, one side of the frequency selection unit is in the X direction, and a lumped resistor is arranged in the first gap in the X direction between the cross metal feeder and the T-shaped metal feeder and in the second gap in the X direction on the T-shaped metal feeder, so as to connect the cross metal feeder in the X direction with the T-shaped metal feeder.

[0015] Furthermore, the cross dipoles and the arc-shaped branches together form a T-shaped structure, and the arc-shaped branch is a section of arc-shaped metal sheet; the cross dipoles are distributed at the four corners of the frequency selection unit.

[0016] Furthermore, the bent branch on the arc-shaped metal ring is a structure formed by connecting the ends of multiple arc-shaped metal sheets with gradually decreasing arc lengths in sequence, these arc-shaped metal sheets and the arc-shaped metal ring have the same center of the circle, and the bent branch is located on the outside of the arc-shaped metal ring; the bent branch is connected to the middle part of the inner side of the arc-shaped metal ring through a metal sheet.

[0017] Furthermore, the square patch with rounded inner corners is a structure formed by cutting circular depressions on the four sides of a square metal sheet and processing the corners into rounded corners; there is an arc-shaped through groove between the arc-shaped metal ring and the square patch.

[0018] Furthermore, the T-shaped metal feed line is composed of a first feed line located on the outside and a second feed line vertically arranged in the middle of the inner side of the first feed line. There is a first gap between the second feed line and the cross metal feed line, and a second gap is left near both ends of the first feed line; the width of the first feed line is smaller than that of the second feed line, and after the first feed lines in adjacent frequency selection units are spliced, the first feed line and the second feed lines inside the two first feed lines together form a cross structure.

[0019] Furthermore, the dielectric substrate is made of F4B material with a thickness of 0.5 mm, a dielectric constant of 2.55, and a loss tangent of 0.001.

[0020] Furthermore, the first varactor diode and the second varactor diode can provide a variable capacitance between 0.1-1 pF at a reverse bias voltage between 16V and 0V.

[0021] Compared with the prior art, the present invention has the following technical features:

[0022] 1. The present invention adopts a composite multi-resonance structure design to achieve dual passband independent tuning performance in a single-layer frequency selective surface. By controlling the bias voltage of the corresponding varactor diode, the passband can be independently tuned in the range of 2.4-5.75GHz and 5.7-9.63GHz, respectively, with an insertion loss of less than 1dB. The operating frequency range covers 2.4-9.63GHz, and the relative operating bandwidth reaches 120.2%.

[0023] 2. The present invention adopts a bending structure and a compact array to miniaturize the dual-frequency adjustable frequency selective surface, and exhibits a stable transmission response when the incident TE and TM dual-polarized electromagnetic waves change from 0° to 75°.

[0024] 3. The present invention requires only 8 active devices in one period unit, which significantly reduces the number of active devices, reduces processing complexity, and saves costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic diagram of the overall structure of an adjustable frequency selective surface in one embodiment of the present invention;

[0026] Figure 2 is a schematic diagram of a top-layer resonant structure in one embodiment of the present invention;

[0027] Figure 3 is a schematic diagram of the bottom feeding structure in one embodiment of the present invention;

[0028] Figure 4 is a cross-sectional schematic diagram of a dielectric substrate in one embodiment of the present invention;

[0029] Figure 5 It is a simulation result diagram of independent regulation of varactor diodes in one embodiment of the present invention, wherein (a) is the transmission curve corresponding to the second varactor diode value C2 being maintained at 0.1pF and the first varactor diode value C1 changing from 0.1pF to 0.8pF; (b) is the transmission curve corresponding to the first varactor diode value C1 being maintained at 0.8pF and the second varactor diode value C1 changing from 0.1pF to 0.5pF.

[0030] Figure 6 It is a simulation result diagram of the adjustable frequency selective surface of an embodiment of the present invention under incident waves at different angles, wherein (a) is the oblique incidence transmission curve corresponding to the second varactor diode value C2 being maintained at 0.1pF and the first varactor diode value C1 being maintained at 0.4pF; (b) is the oblique incidence transmission curve corresponding to the first varactor diode value C1 being maintained at 0.8pF and the second varactor diode value C1 being maintained at 0.3pF.

[0031] Explanation of the numbers in the figure: 1 dielectric substrate, 2 top metal resonant structure, 21 cross dipole, 22 arc-shaped branch, 23 square patch, 24 bent branch, 25 arc-shaped metal ring, 3 bottom metal feeding structure, 31 cross metal feed line, 32 T-shaped metal feed line, 321 first feed line, 322 second feed line, 33 first gap, 34 second gap, 4 first varactor diode, 5 second varactor diode, 6 lumped resistor, 7 first metal via, 8 second metal via. DETAILED DESCRIPTION

[0032] The present invention provides a frequency selective surface with an adjustable dual-frequency wave-transmitting window with high angle stability, adopts miniaturization technology to achieve high angle stability characteristics, and uses multi-band independent regulation technology to achieve independent adjustment of the dual-frequency wave-transmitting window while effectively reducing the number of active components, reducing processing complexity and saving costs; this structure has more advantages in application fields such as frequency hopping communication, MIMO antenna and collaboration between different standards and systems.

[0033] See also Figure 1 , a high-angle stable dual-frequency wave-transmitting window continuously adjustable frequency selective surface of the present invention comprises: a dielectric substrate 1, on which frequency selective units of a square structure are distributed;

[0034] Each frequency selection unit includes a top metal resonant structure 2 arranged on the upper surface of a dielectric substrate 1, a bottom metal feeding structure 3 arranged on the lower surface of the dielectric substrate 1, an active device, and a first metal via 7 and a second metal via 8 connecting the upper and lower surfaces, wherein:

[0035] 1. Top metal resonant structure 2

[0036] The top metal resonant structure 2 is a centrally symmetrical structure, comprising: a cross dipole 21 with an arcuate branch 22, an arcuate metal ring 25 with a bent branch 24, and a square patch 23 with concave rounded corners on all sides; the arcuate metal rings 25 are distributed around the square patch 23, the ends of adjacent arcuate metal rings 25 are connected, and after rotating an arcuate metal ring 25 90° clockwise or counterclockwise, the bent branches 24 on it can overlap with the bent branches 24 on the adjacent arcuate metal ring 25; the bent branches 24 are connected to the outside of the arcuate metal ring 25, and the cross dipole 21 is arranged on the outside of the bent branch 24; the arcuate metal rings 25 of adjacent frequency selection units are connected to each other, and the cross dipoles 21 of adjacent frequency selection units are connected to each other.

[0037] See also Figure 1 and Figure 2 In this embodiment, the cross dipole 21 and the arc-shaped branch 22 together form a T-shaped structure, and the arc-shaped branch 22 is a section of arc-shaped metal sheet; the cross dipole 21 is distributed at the four corners of the frequency selection unit.

[0038] The bent branch 24 on the arc-shaped metal ring 25 is a structure composed of multiple arc-shaped metal sheet ends with gradually decreasing arc lengths connected in sequence. These arc-shaped metal sheets and the arc-shaped metal ring 25 have the same center of the circle, and the bent branch 24 is located on the outside of the arc-shaped metal ring 25; the bent branch 24 is connected to the middle part of the inner side of the arc-shaped metal ring 25 through a metal sheet.

[0039] The square patch 23 with rounded inner corners refers to a structure formed by cutting circular depressions on the four sides of a square metal sheet and processing the corners into rounded corners; there is an arc-shaped through groove between the arc-shaped metal ring 25 and the square patch 23.

[0040] See attached Figure 2 In this embodiment of the present invention, the side length of the frequency selection unit is p = 6.75 mm, the distance between the side of the end connection of the adjacent arc-shaped metal ring 25 and the edge of the frequency selection unit is g = 3.2 mm, and the distance from the end of the cross dipole 21 to the outside of the arc-shaped branch 22 is l 1 =1.25mm, diagonal spacing of square patch 23 l 2 =3.55mm, the width w of the second variable capacitance diode 5 installation position 1 =0.3mm, the width w of the connection between the ends of adjacent arc-shaped metal rings 25 2 =0.4mm, the length d of the first variable capacitance diode 4 installation position 1 =0.7mm, the length d of the second variable capacitance diode 5 installation position 2 =0.4mm, the distance d between the bent branch 24 and the arc-shaped metal ring 25 3 = 0.2 mm, the distance d between adjacent arc-shaped metal sheets in the bending branch 24 4 = 0.25 mm, the distance d between the arc-shaped branch 22 and the edge of the frequency selection unit 5 =0.2mm.

[0041] 2. Bottom metal feed structure 3

[0042] The bottom metal feeding structure 3 includes: a cross metal feed line 31 and a T-shaped metal feed line 32; the cross metal feed line 31 is connected to the square patch 23 on the upper surface of the dielectric substrate 1 through a first metal via 7, and the first metal via 7 is located at the center of the frequency selection unit; the T-shaped metal feed line 32 is distributed around the cross metal feed line 31 and the ends are connected to each other, forming a square structure matching the size of the frequency selection unit; the T-shaped metal feed line 32 is connected to the cross dipole 21 on the upper surface of the dielectric substrate 1 through a second metal via 8, and the second metal via 8 is located at the four corners of the frequency selection unit; there is a first gap 33 between each T-shaped metal feed line 32 and the cross metal feed line 31, and a second gap 34 is left on the part close to the two ends of each T-shaped metal feed line 32; the T-shaped metal feed lines 32 of adjacent frequency selection units are connected to each other to form a cross structure.

[0043] See attached Figure 1 and Figure 3 , a cross metal feed line 31 is located at the center of the lower surface of the dielectric substrate 1 in each frequency selection unit, and four T-shaped metal feed lines 32 are distributed around it; the T-shaped metal feed line 32 is composed of a first feed line 321 located on the outside and a second feed line 322 vertically arranged in the middle of the inner side of the first feed line 321, a first gap 33 exists between the second feed line 322 and the cross metal feed line 31, and a second gap 34 is left near both ends of the first feed line 321. The width of the first feed line 321 is smaller than that of the second feed line 322, and after the first feed lines 321 in adjacent frequency selection units are spliced, their width is consistent with that of the second feed line 322; that is, the spliced ​​first feed line 321 and the second feed line 322 inside the two first feed lines 321 together form a cross structure.

[0044] exist Figure 3 In the given embodiment, the distance between adjacent second gaps 34 on the T-shaped metal feed line 32 is l 3 =4.75mm, the length l of each feeder line in the cross metal feeder line 31 4 =1mm, the width of each feed line w=0.2mm; the width of the second gap 34 d=0.5mm.

[0045] exist Figure 4 In the given embodiment, the dielectric substrate 1 is made of F4B material with a thickness of 0.5 mm, a dielectric constant of 2.55, a loss tangent of 0.001, and a diameter of the first metal via 7 of r=0.2 mm.

[0046] 3. Active devices

[0047] The active device includes a first varactor diode 4 and a second varactor diode 5; the first varactor diode 4 is welded between the arc branch 22 and the bent branch 24 of the top metal resonant structure 2, and its positive electrode is connected to the cross dipole 21 through the arc branch 22, and its negative electrode is connected to the bent branch 24; the second varactor diode 5 is welded between the end connection of the adjacent arc-shaped metal ring 25 and the corresponding corner of the square patch 23, and its positive electrode is connected to the square patch 23, and its negative electrode is connected to the arc-shaped metal ring 25.

[0048] The two adjacent sides of the frequency selection unit are denoted as the X direction and the Y direction, and the vertical direction is denoted as the Z direction. A lumped resistor 6 is arranged in the first gap 33 in the X direction between the cross metal feed line 31 and the T-shaped metal feed line 32 and in the second gap 34 in the X direction on the T-shaped metal feed line 32, so as to connect the cross metal feed line 31 in the X direction with the T-shaped metal feed line 32; the resistance value of the lumped resistor 6 is 10000Ω.

[0049] In this embodiment, the first varactor diode 4 and the second varactor diode 5 are both of model MA46H120, which can provide a variable capacitance between 0.1-1 pF under a reverse bias voltage between 16V and 0V.

[0050] Please refer to Figure 1 The top metal resonant structure 2 on the upper and lower surfaces of the dielectric substrate 1 corresponds to the center of the cross metal feed line 31 in the bottom metal feeding structure 3, and is connected in the vertical direction by the first metal via 7; the top metal resonant structure 2 located on the upper surface of the dielectric substrate 1 forms three different potentials: the positive pole of the DC power supply is connected to the arc-shaped metal ring 25; the negative pole of the DC power supply is connected to the cross metal feed line 31 in the center of the frequency selection unit, and a reverse bias voltage is provided to the square patch 23 through the first metal via 7; the negative pole of the DC power supply is connected to the T-shaped metal feed line 32, and another reverse bias voltage is provided to the cross dipole 21 through the second metal via 8; the change of the variable capacitance value of the active device is controlled by changing the bias voltage, so as to independently adjust the dual working frequency bands of the adjustable frequency selection surface, and realize the broadband reconfigurable function of the wave-transmitting window.

[0051] The following is a further explanation of the technical effects of the present invention in combination with simulation experiments:

[0052] In order to verify that the proposed adjustable frequency selective surface has the characteristics of broadband reconfigurable wave window, the transmission curves of the varactor diodes of the embodiment of the present invention that are independently regulated are simulated. The results are as follows: Figure 5 shown.

[0053] See also Figure 5(a) shows the frequency response curves of the first varactor diode with different capacitance values ​​when the second varactor diode value C2 is kept at 0.1pF under the condition of vertical incidence of TE polarized wave. It can be seen that as the first varactor diode value C1 increases from 0.1pF to 0.8pF, the resonant frequency of the second passband remains at 9.63GHz, while the resonant frequency of the first passband can be continuously tuned in the range of 2.4-5.75GHz, with a relative bandwidth of 82.1% and an insertion loss that is always less than 1dB.

[0054] See also Figure 5 (b) shows the frequency response curves of the first varactor diode with different capacitance values ​​when the first varactor diode value C1 is kept at 0.8pF under the condition of vertical incidence of TE polarized wave. It can be seen that as the second varactor diode value C2 increases from 0.1pF to 0.4pF, the resonant frequency of the first passband remains at 2.4GHz, while the resonant frequency of the second passband can be continuously tuned in the range of 5.7-9.63GHz, with a relative bandwidth of 51.2% and an insertion loss that is always less than 1dB.

[0055] In order to verify that the proposed adjustable frequency selective surface has the characteristic of stable incident angle, the transmission curves of electromagnetic waves with different oblique incident angles of the embodiment of the present invention are simulated. The results are as follows: Figure 6 shown.

[0056] See also Figure 6 (a) shows the frequency response curves of TE polarized waves at different incident angles when the first varactor diode value C1 is kept at 0.1pF and the second varactor diode value C2 is kept at 0.4pF. It can be seen that as the angle of the oblique incident electromagnetic wave increases to 75°, the resonant frequency is still basically the same as that at vertical incidence, and the in-band insertion loss is always less than 3dB, showing good angle stability.

[0057] See also Figure 6 (b) shows the frequency response curves of TE polarized waves at different incident angles when the first varactor diode value C1 is kept at 0.8pF and the second varactor diode value C2 is kept at 0.3pF. It can be seen that as the angle of the oblique incident electromagnetic wave increases to 75°, the resonant frequency is still basically the same as that at vertical incidence, and the in-band insertion loss is always less than 3dB, showing good angle stability.

[0058] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A high-angle stable dual-frequency wave-transmitting window continuously adjustable frequency selective surface, characterized in that: include: A dielectric substrate (1), on which frequency selection units having a square structure are distributed; Each frequency selection unit comprises a top metal resonant structure (2) arranged on the upper surface of a dielectric substrate (1), a bottom metal feeding structure (3) arranged on the lower surface of the dielectric substrate (1), an active device, and a first metal via (7) and a second metal via (8) connecting the upper and lower surfaces, wherein: The top metal resonant structure (2) is a centrally symmetrical structure, comprising: a cross dipole (21) with an arcuate branch (22), an arcuate metal ring (25) with a bent branch (24), and a square patch (23) with concave rounded corners on all sides; the arcuate metal rings (25) are distributed around the square patch (23), the ends of adjacent arcuate metal rings (25) are connected, the bent branch (24) is connected to the outside of the arcuate metal ring (25), and the cross dipole (21) is arranged on the outside of the bent branch (24); the arcuate metal rings (25) of adjacent frequency selection units are connected to each other, and the cross dipoles (21) of adjacent frequency selection units are connected to each other; The bottom metal feed structure (3) comprises: a cross metal feed line (31) and a T-shaped metal feed line (32); the cross metal feed line (31) is connected to a square patch (23) on the upper surface of a dielectric substrate (1) through a first metal via (7), and the first metal via (7) is located at the center of the frequency selection unit; the T-shaped metal feed line (32) is distributed around the cross metal feed line (31) and the ends are connected to each other; the T-shaped metal feed line (32) is connected to the dielectric substrate through a second metal via (8). (1) A cross dipole (21) on the upper surface, a second metal via (8) located at the four corners of the frequency selection unit; a first gap (33) exists between each T-shaped metal feed line (32) and the cross metal feed line (31), a second gap (34) is left near the two ends of each T-shaped metal feed line (32), and a lumped resistor (6) is arranged in part of the first gap (33) and the second gap (34); the T-shaped metal feed lines (32) of adjacent frequency selection units are connected to each other to form a cross-shaped structure; The active device comprises a first varactor diode (4) and a second varactor diode (5); the positive electrode of the first varactor diode (4) is connected to the arc-shaped branch node (22) of the top metal resonant structure (2), and the negative electrode is connected to the bent branch node (24); the positive electrode of the second varactor diode (5) is connected to the corner of the square patch (23), and the negative electrode is connected to the end connection of the adjacent arc-shaped metal ring (25).

2. The high-angle stable dual-frequency wave-transmitting window continuously adjustable frequency selective surface according to claim 1, characterized in that: The positive electrode of a direct current power supply is connected to an arc-shaped metal ring (25); one path of the negative electrode of the direct current power supply is connected to a cross metal feeder (31) at the center of a frequency selection unit, and a reverse bias voltage is provided to a square patch (23) through a first metal via (7); another path of the negative electrode of the direct current power supply is connected to a T-shaped metal feeder (32), and another reverse bias voltage is provided to a cross dipole (21) through a second metal via (8); and the change of the variable capacitance value of the active device is controlled by changing the bias voltage, thereby independently regulating the dual working frequency bands of the adjustable frequency selection surface, and realizing the broadband reconfigurable function of the wave-transmitting window.

3. The high-angle stable dual-frequency wave-transmitting window continuously adjustable frequency selective surface according to claim 1, characterized in that: Note that one side of the frequency selection unit is in the X direction, and a lumped resistor (6) is arranged in a first gap (33) in the X direction between the cross metal feed line (31) and the T-shaped metal feed line (32) and in a second gap (34) in the X direction on the T-shaped metal feed line (32), thereby connecting the cross metal feed line (31) in the X direction with the T-shaped metal feed line (32).

4. The high-angle stable dual-frequency wave-transmitting window continuously adjustable frequency selective surface according to claim 1, characterized in that: The cross dipole (21) and the arc-shaped branch (22) together form a T-shaped structure, and the arc-shaped branch (22) is a section of arc-shaped metal sheet; the cross dipole (21) is distributed at the four corners of the frequency selection unit.

5. The high-angle stable dual-frequency wave-transmitting window continuously adjustable frequency selective surface according to claim 1, characterized in that: The bent branch (24) on the arc-shaped metal ring (25) is a structure formed by connecting the ends of multiple arc-shaped metal sheets with gradually decreasing arc lengths in sequence. These arc-shaped metal sheets and the arc-shaped metal ring (25) have the same center of a circle, and the bent branch (24) is located on the outside of the arc-shaped metal ring (25); the bent branch (24) is connected to the middle of the inner side of the arc-shaped metal ring (25) through a metal sheet.

6. The high-angle stable dual-frequency wave-transmitting window continuously adjustable frequency selective surface according to claim 1, characterized in that: The square patch (23) with rounded inner corners on all sides is a structure formed by cutting circular recesses on all sides of a square metal sheet and processing the corners into rounded corners; an arc-shaped through groove exists between the arc-shaped metal ring (25) and the square patch (23).

7. The high-angle stable dual-frequency wave-transmitting window continuously adjustable frequency selective surface according to claim 1, characterized in that: The T-shaped metal feed line (32) is composed of a first feed line (321) located on the outside and a second feed line (322) vertically arranged in the middle of the inside of the first feed line (321); a first gap (33) exists between the second feed line (322) and the cross metal feed line (31), and a second gap (34) is left near both ends of the first feed line (321); the width of the first feed line (321) is smaller than that of the second feed line (322); after the first feed lines (321) in adjacent frequency selection units are spliced, the first feed line 321 and the second feed lines 322 inside the two first feed lines 321 together form a cross structure.

8. The high-angle stable dual-frequency wave-transmitting window continuously adjustable frequency selective surface according to claim 1, characterized in that: The dielectric substrate (1) is made of F4B material with a thickness of 0.5 mm, a dielectric constant of 2.55, and a loss tangent of 0.

001.

9. The high-angle stable dual-frequency wave-transmitting window continuously adjustable frequency selective surface according to claim 1, characterized in that: The first variable capacitance diode (4) and the second variable capacitance diode (5) can provide a variable capacitance between 0.1 and 1 pF at a reverse bias voltage between 16 and 0 V.

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