A frequency selective surface with wide-band reconfigurable characteristics of a wave-transmitting window
The stacked structure of variable capacitive and inductive elements in frequency selective surfaces addresses the limitations of RFSS, providing wideband tunability and enhanced interference suppression, suitable for electromagnetic interference and stealth applications.
Patent Information
- Application Number
- CN202211499598.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-11-28
- Publication Date
- 2025-07-15
- Estimated Expiration
- 2042-11-28
AI Technical Summary
The existing tuning reconfigurable frequency selection surface has a small adjustment range in the wide frequency domain, a wave-transmitting window adjustment is not fine enough, and a large unit size, resulting in inflexible frequency band adjustment.
Using a top-down stacked resonant unit structure, combining variable capacitive and inductive surface units, multi-order passband and large-range frequency adjustment is achieved through the combination of variable capacitive diodes and switch diodes. The miniaturization unit is designed using electromagnetic coupling to control the conduction and turn-off of the switch diodes to change the equivalent capacitance value.
It achieves a relative bandwidth of more than 40% under 0.8dB insertion loss condition, has no ripple in the band, good out-of-band suppression effect, and the unit size is reduced to about 10% of the center frequency of the lowest frequency passband. The wave-transmitting window is reconfigurable in a wide range within a wide band.
Smart Images
Figure CN115864003B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of microwave technology, and particularly relates to a frequency selective surface with wide-band reconfigurable characteristics of a wave-transmitting window, which can be applied to related devices in fields with requirements for anti-electromagnetic interference and electromagnetic stealth. Background Art
[0002] A frequency selective surface (FSS) is a two-dimensional periodic structure composed of a large number of identical units arranged in combination, and it has selectivity for electromagnetic waves such as frequency and polarization.
[0003] Due to its special spatial filtering characteristics, FSS is widely used in multiple fields such as radomes, electromagnetic shielding, and reflectors. When the enemy detection radar and our radar operate in different frequency bands, the radome loaded with FSS can transmit electromagnetic waves in the operating frequency band of our radar to ensure the normal operation of our antenna, and reflect electromagnetic waves in the remaining frequency bands. In other aspects, such as mobile communication, applying an FSS shielding layer can improve the interference problem of signals between various communication systems with more and more forms and types, enabling signals within the operating frequency band of the communication device to pass normally while reflecting signals outside the frequency band.
[0004] A reconfigurable frequency selective surface (RFSS) is to add active devices and matching bias circuits to the basic structure of the traditional passive frequency selective surface to achieve the change of filtering characteristics. Currently, the main technical route of the reconfigurable frequency selective surface is to load PIN diodes or varactor diodes to achieve the change of filtering characteristics. Therefore, the current reconfigurable frequency selective surface can be mainly divided into a switch-type RFSS and a tuning-type RFSS.
[0005] The switch-type RFSS realizes a filter response with switchable passband / stoppband by loading PIN diodes. Currently, the research on the switch-type RFSS mainly focuses on how to design better switchable characteristics between the passband and the stoppband (i.e., having a good stoppband effect in another state within the frequency band corresponding to the passband), how to independently control the operating state and polarization state, and how to simplify the bias network; the tuning-type RFSS is mainly realized by loading varactor diodes or variable dielectric materials. The research on the tuning-type RFSS mainly focuses on improving the tuning accuracy or range. Limited by the parameter adjustment range of existing materials or active devices, the operating frequency band of the tuning-type RFSS can only be adjusted in a small range and cannot be moved in a large range.
[0006] At present, it is impossible to achieve fine tuning of the wave - transmitting window of a frequency - selective surface in a wide frequency band through a single device only in the prior art. Therefore, the method of combining multiple tuning means for joint tuning has become a new research hotspot. Summary of the Invention
[0007] In order to overcome the above - mentioned shortcomings of the prior art, the purpose of the present invention is to provide a frequency - selective surface with reconfigurable characteristics in a wide frequency band of the wave - transmitting window. This frequency - selective surface has miniaturized low - profile and reconfigurable characteristics with tunable characteristics in a wide frequency band, and mainly solves one or all of the problems existing in the tunable reconfigurable frequency - selective surface, such as relatively large unit size, low tuning accuracy, small adjustment range of the wave - transmitting window, and narrow passband (relative bandwidth less than 40%).
[0008] In order to achieve the above - mentioned purpose, the technical solution adopted by the present invention is:
[0009] A frequency - selective surface with reconfigurable characteristics in a wide frequency band of the wave - transmitting window, including M×N two - dimensional periodically arranged resonant units, where M≥3, N≥3. Each of the resonant units includes a first variable capacitive surface unit, a passive inductive surface unit, and a second variable capacitive surface unit arranged from top to bottom;
[0010] The first variable capacitive surface unit includes a first dielectric substrate, a first - layer metal patch, and a second - layer metal patch;
[0011] The first - layer metal patch is arranged on the upper surface of the first dielectric substrate and includes four first arrow - shaped metal patches. The first arrow - shaped metal patch is composed of a first - part metal patch and a second - part metal patch. The shape of the first - part metal patch is an isosceles triangle, and the shape of the second - part metal patch is a T - shape. The end of the middle part of the T - shape is connected to the center of the base of the isosceles triangle; the apex angles of the isosceles triangles of the four first arrow - shaped metal patches are opposite and symmetrically distributed at the center; there is a gap between the sides of the isosceles triangles of adjacent first arrow - shaped metal patches and they are connected by a first switching diode; at the central position of the bottom of each T - shape, a second metal connection line is connected through a first variable - capacitance diode; the two ends of the T - shaped base of the second - part metal patch of two opposite first arrow - shaped metal patches are respectively connected to a first metal connection line through a first inductor; the two ends of the T - shaped base of the second - part metal patch of the other two opposite first arrow - shaped metal patches are respectively connected to a third metal connection line through a first inductor;
[0012] The second - layer metal patch includes four strip - shaped metal patches, and each strip - shaped metal patch is connected to a second metal connection line through a first metallized via in the first dielectric substrate;
[0013] The second variable capacitive surface unit has the same structure as the first variable capacitive surface unit and is symmetrically arranged with respect to the passive inductive surface unit, realizing ultra-wideband passband characteristics and wide-band reconfigurable characteristics.
[0014] In one embodiment, in the first layer of metal patches, the first arrow-shaped metal patches are oppositely placed on the central axis of the unit, and the second metal connection lines are respectively located at the midpoints of the four edges of the unit.
[0015] In one embodiment, the first switching diode is connected between the midpoints of the sides of the isosceles triangle formed by adjacent first arrow-shaped metal patches to control the conduction and disconnection of the first arrow-shaped metal patches, thereby controlling the size of the distributed capacitance in the gap.
[0016] In one embodiment, the first metal connection line, the second metal connection line, and the third metal connection line are all strip-shaped metal patches. The length of the third metal connection line is greater than the length of the first metal connection line, and the length of the first metal connection line is greater than the length of the second metal connection line; the first inductor is a lumped inductor.
[0017] In the second layer of metal patches of adjacent resonant units, they are connected by strip metal patches.
[0018] In one embodiment, the passive inductive surface unit includes a second dielectric substrate, a third dielectric substrate, and a third layer of metal patches; the third layer of metal patches is an inductive surface unit arranged on the lower surface of the second dielectric substrate or the upper surface of the third dielectric substrate and directly below the projection of the middle part of each T shape.
[0019] In one embodiment, the third layer of metal patches is a cross-shaped grid metal patch. In the passive inductive surface units of adjacent resonant units, they are connected by cross-shaped grid metal patches.
[0020] The frequency selective surface with wide-band reconfigurable characteristics of the through-wave window of the present invention can be applied to related devices in fields with anti-electromagnetic interference and electromagnetic stealth requirements.
[0021] Compared with the prior art, the beneficial effects of the present invention are:
[0022] 1. The present invention adopts a unit structure arranged in a cascaded manner from top to bottom, combines a variable capacitive surface unit composed of arrow-shaped metal patches, varactor diodes, and switching diodes with an inductive surface unit to form a filtering structure with a C-L-C structure, realizes the in-band flatness and ultra-wideband characteristics of the passband, and achieves a relative bandwidth of more than 40% with an insertion loss of 0.8 dB and no ripples in the passband. While realizing multiple-order passbands by using electromagnetic coupling between different surfaces, a transmission zero is introduced outside the band, improving the out-of-band rejection and overcoming the technical problems of insufficient out-of-band interference suppression when the radar is working and insufficient blocking of external electromagnetic interference in the entire frequency band within the wide frequency band when the radar is not working in the prior art.
[0023] 2. The present invention adopts a technical solution designed by coupling electric fields and coupling magnetic fields to realize the miniaturization of the unit, optimizes the disadvantage of poor angular stability caused by the relatively large size of traditional frequency selective surface units, and reduces the unit size to about 10% of the wavelength corresponding to the center frequency of the lowest-frequency passband.
[0024] 3. The present invention adopts a technical solution designed by combining varactor diodes and switching diodes to realize the reconfigurable characteristics of the passband within a wide frequency band. By setting the varactor diode on the capacitive slot of the structure, the resonant frequency of the frequency selective surface can be shifted within a small range by changing the capacitance value of the varactor diode, realizing the reconfiguration within a small range of the passband. However, due to the limited change range of the capacitance value of the varactor diode, it is difficult for a reconfigurable frequency selective surface based only on varactor diodes to achieve large-range reconfiguration. To solve the above problems, the present invention newly loads a switching diode on the basis of the varactor diode. By controlling the on and off of the switching diode, the equivalent capacitance value in the structure can be changed significantly, realizing a large-range cross-change of the resonant point of the unit structure. Then, combined with the small-range adjustment of the varactor diode, fine adjustment within a large range of the transmission window is finally realized. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The drawings described herein are used to provide a further understanding of the present invention, form a part of this application, and do not constitute an improper limitation to the present invention. In the drawings:
[0026] Figure 1 It is a schematic diagram of the unit structure of the present invention.
[0027] Figure 2 It is a schematic diagram of the variable capacitive surface unit structure of the first-layer metal patch of the present invention and a side view of the first dielectric substrate.
[0028] Figure 3 It is a schematic diagram of a partial bias network structure of the second-layer metal patch of the present invention.
[0029] Figure 4Schematic diagram of the inductive surface unit structure of the third-layer metal patch of the present invention and side views of the second and third dielectric substrates.
[0030] Figure 5 Schematic diagram of a partial bias network structure of the fourth-layer metal patch of the present invention.
[0031] Figure 6 Schematic diagram of the variable capacitive surface unit structure of the fifth-layer metal patch of the present invention and side view of the fourth dielectric substrate.
[0032] Figure 7 Simulation result diagrams of different capacitance values of the present invention, where (a) is the simulation result diagram of different capacitance values in the on state of the switching diode; (b) is the simulation result diagram of different capacitance values in the off state of the switching diode.
[0033] Figure 8 Five wave-transmitting states selected by the present invention.
[0034] Figure 9 Schematic diagram of the feeding method of the variable capacitive surface unit array of the present invention, where V1, V2, V3, and V4 in the figure represent four independently adjustable DC voltages and V1 > V2 > V3 > V4. Detailed implementation manners
[0035] The implementation manners of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.
[0036] Herein, the exemplary embodiments and descriptions of the present invention are used to explain the present invention, but not to limit the present invention.
[0037] As Figure 1 shown, a miniaturized frequency selective surface with wide-band reconfigurable characteristics of a wave-transmitting window according to the present invention includes M×N resonant units arranged in a two-dimensional periodic manner, where M≥3 and N≥3.
[0038] In the present invention, each resonant unit includes a first variable capacitive surface unit, a passive inductive surface unit, and a second variable capacitive surface unit arranged in sequence from top to bottom.
[0039] Referring to Figure 1 , Figure 2 and Figure 3 , the first variable capacitive surface unit mainly includes a first dielectric substrate 6, a first-layer metal patch 1, and a second-layer metal patch 2; among them, a first metallized via 12 is loaded in the first dielectric substrate 6, and a first variable capacitance diode 15, a first switching diode 13, and a first inductor 17 are loaded in the first-layer metal patch 1.
[0040] Referring to Figure 1 and Figure 4, the passive inductive surface unit includes a second dielectric substrate 7, a third dielectric substrate 8, and a third-layer metal patch 3, and the third-layer metal patch 3 is the inductive surface unit.
[0041] Reference Figure 1 、 Figure 5 and Figure 6 , the second varactor surface unit has the same structure as the first varactor surface unit, and includes a fourth dielectric substrate 9, a fourth-layer metal patch 4, and a fifth-layer metal patch 5; wherein a second metallized via 52 is loaded in the fourth dielectric substrate 9, and a second varactor diode 55, a second switching diode 53, and a second inductor 57 are loaded in the fifth-layer metal patch 5.
[0042] Refer again to Figure 1 and Figure 2 , the first-layer metal patch 1 is disposed on the upper surface of the first dielectric substrate 6, and mainly includes four first metal connection lines 11, four first switching diodes 13, four first arrow-shaped metal patches 14, four first varactor diodes 15, four second metal connection lines 16, eight first inductors 17, and four third metal connection lines 18. Among them, the shapes and areas of the four first arrow-shaped metal patches 14 are equal, and each is composed of a first part of the metal patch 141 and a second part of the metal patch 142. The shape of the first part of the metal patch 141 is an isosceles triangle, and the shape of the second part of the metal patch 142 is a T shape. The end of the middle part of the T shape is connected to the center of the base of the isosceles triangle. The apex angles of the isosceles triangles of the four first arrow-shaped metal patches 14 are opposite, and they are symmetrically distributed about the center, and there is a gap between the sides of the isosceles triangles of adjacent first arrow-shaped metal patches 14. The four first switching diodes 13 are respectively arranged at the four gaps, so as to connect the isosceles triangles of adjacent first arrow-shaped metal patches 14, control the conduction and disconnection of the first arrow-shaped metal patches 14, and further control the size of the distributed capacitance in the gap. At the central position of the bottom of the T shape of each first arrow-shaped metal patch 14, a second metal connection line 16 is connected through a first varactor diode 15 respectively. The two ends of the T-shaped bottom edge of the second part of the metal patch 142 of two opposite first arrow-shaped metal patches 14 are respectively connected to a first metal connection line 11 through a first inductor 17; the two ends of the T-shaped bottom edge of the second part of the metal patch 142 of the other two opposite first arrow-shaped metal patches 14 are respectively connected to a third metal connection line 18 through a first inductor 17.
[0043] For the first-layer metal patch 1, adjacent resonant units are connected through the second metal connection line 16, and also through the third metal connection line 18. That is, the second metal connection lines 16 of adjacent resonant units are connected, and along the length direction of the third metal connection line 18, the third metal connection lines 18 of adjacent resonant units are connected.
[0044] Exemplarily, each of the first arrow-shaped metal patches 14 is preferably placed relatively on the central axis of the resonant unit, and each of the second metal connection lines 16 is preferably located at the midpoints of the four edges of the resonant unit respectively. Moreover, the first switching diode 13 is preferably connected between the midpoints of the sides of the isosceles triangle formed by adjacent first arrow-shaped metal patches 14.
[0045] Furthermore, in the present invention, the first metal connection line 11, the second metal connection line 16, and the third metal connection line 18 are all strip-shaped metal patches, and: the length of the third metal connection line 18 is greater than the length of the first metal connection line 11, and the length of the first metal connection line 11 is greater than the length of the second metal connection line 16; the first inductor 17 is a lumped inductor. Wherein the second metal connection line 16 serves as the soldering point of the first variable capacitance diode 15.
[0046] Refer again to Figure 1 and Figure 3 , the second-layer metal patch 2 mainly includes four strip metal patches 22. One metalized via connection point 21 is provided at one end of each strip metal patch 22.
[0047] For the second-layer metal patch 2, along the length direction of the strip metal patch 22, one end of each metal strip patch 22 is connected to the metal strip patch 22 of the adjacent resonant unit, and the other end is connected to the aforementioned first metalized via 12 through its metalized via connection point 21, that is, finally connected to a first metal connection line 11. Thus, the first-layer metal patch 1 and the second-layer metal patch 2 are connected through the first metalized via 12, forming a first variable capacitive surface unit with a bias control network.
[0048] Refer again to Figure 1 and Figure 4 , the third-layer metal patch 3 serves as an inductive surface unit, which adopts the cross-shaped grid metal patch 31 shown in Figure 4 , and can be arranged on the lower surface of the second dielectric substrate 7 or the upper surface of the third dielectric substrate 8, and is directly below the projection of the middle part of each of the said T-shapes, that is, on the symmetric central axis of the resonant unit. The cross-shaped grid metal patches 31 of adjacent resonant units are connected to form an inductive surface structure of a grid structure.
[0049] The first variable capacitive surface unit and the second variable capacitive surface unit are cascaded through a passive inductive surface unit, that is, the second dielectric substrate 7, the inductive surface unit, and the third dielectric substrate 8 in sequence, to realize the ultra-wideband and wide-band tuning characteristics within the passband.
[0050] The structure of the second variable capacitive surface unit of the present invention is the same as that of the first variable capacitive surface unit, and is symmetrically arranged with respect to the third-layer metal patch 3.
[0051] Figure 5 , Figure 6 In the second variable capacitive surface unit shown, the fourth-layer metal patch 4 is exactly the same as the second-layer metal patch 2, and the fifth-layer metal patch 5 is exactly the same as the first-layer metal patch 1. Specifically, the strip metal patch 42 is exactly the same as the strip metal patch 22, and the setting form of the metallized-via connection point 41 is exactly the same as that of the metallized-via connection point 21.
[0052] The fourth metal connection line 51 is exactly the same as the first metal connection line 11, the second metallized via 52 is exactly the same as the first metallized via 12, the second switching diode 53 is exactly the same as the first switching diode 13, the second arrow-shaped metal patch 54 is exactly the same as the first arrow-shaped metal patch 14, the second variable capacitance diode 55 is exactly the same as the first variable capacitance diode 15, the fifth metal connection line 56 is exactly the same as the second metal connection line 16, the second inductor 57 is exactly the same as the first inductor 17, and the sixth metal connection line 58 is exactly the same as the third metal connection line 18.
[0053] In the first variable capacitive surface unit, the first metal connection line (11), the second metal connection line (16), the third metal connection line (18), the metal connection line (22), and the first metallized via 12 in the first dielectric substrate (6) constitute its bias control network. The bias control network controls each PIN diode and variable capacitance diode in the unit. Specifically, a DC voltage is applied across the two devices through the bias control network, thereby changing the overall response characteristics of the structure. The bias control network of the second variable capacitive surface unit has a similar composition and function.
[0054] Thus, the resonant units from top to bottom are the first-layer metal patch 1, the first dielectric substrate 6, the second-layer metal patch 2, the second dielectric substrate 7, the third-layer metal patch 3, the third dielectric substrate 8, the fourth-layer metal patch 4, the fourth dielectric substrate 9, and the fifth-layer metal patch 5.
[0055] In the embodiment of the present invention, the first dielectric substrate 6 and the fourth dielectric substrate 9 have the same thickness, and both are provided with metallized vias; the second dielectric substrate 7 and the third dielectric substrate 8 have the same thickness, and the thickness is greater than that of the first dielectric substrate 6 and the fourth dielectric substrate 9.
[0056] According to the above structure, the first variable capacitive surface unit, inductive surface unit, and second variable capacitive surface unit of the present invention achieve the filtering characteristics of multi-order passbands through the upper, middle, and lower relationship laminations. By controlling whether the first switching diode 13 is turned on, a large-range jump of the wave-transmitting window of the frequency selective surface is realized. When the first switching diode 13 is at zero bias voltage, the first switching diode 13 is approximately open, and the gaps between adjacent first arrow-shaped metal patches 14 in the unit structure exhibit a large distributed capacitance. At this time, the wave-transmitting window is in the high-frequency band; when the first switching diode 13 is turned on, it is approximately a good conductor, changing the original induced current distribution, destroying the original unit resonance state, and equivalently short-circuiting the distributed capacitance between the gaps of adjacent first arrow-shaped metal patches 14 in parallel. At this time, the wave-transmitting window is in the low-frequency band, thereby realizing a large-range reconstruction of the wave-transmitting window. Then, in cooperation with the control of the overall equivalent capacitance size of the structure by the varactor diode 15, tuning is performed within a small range. The two jointly control to finally achieve the reconfigurable characteristic within the wide frequency band of the wave-transmitting window of the structure.
[0057] As Figure 8 shown, the frequency selective surface after arraying needs to set 4 DC voltages for control. By controlling the magnitude of the DC bias voltage difference, the on-off of the first switching diode 13 and the capacitance value of the first variable capacitance diode 15 are controlled to achieve the reconfigurable characteristic of the wave-transmitting window within the wide frequency band.
[0058] In one embodiment, the first dielectric substrate 6 and the second dielectric substrate 7 adopt a square structure of Rogers RT 5880 with a relative dielectric constant of 2.2, the side length P = 5 mm, the thickness H1 of the first dielectric substrate 6 = 0.4 mm, and the thickness H2 of the second dielectric substrate 7 = 1.3 mm. Among the first layer of metal patches 1 and the fifth layer of metal patches 5, the side length l1 of the first arrow-shaped metal patch 14 = 2.3 mm, the arrow-shaped rod length l2 = 0.8 mm, the arrow rod width w = 0.2 mm, and the arrow tail length l3 = 0.5 mm; the gap width d2 between the first arrow-shaped metal patches 14 = 0.2 mm, the grooving width d4 between the gaps = 0.3; the length of the first metal connection line 11 l4 = 1 mm; the length of the varactor diode 15 used in the first and second variable capacitive surface units d1 = 0.4 mm, the width w = 0.2 mm; the length of the first switching diode 13 d3 = 0.4 mm, the width w1 = 0.2 mm; the length of the first inductor 17 w2 = 0.25 mm;
[0059] In one embodiment, the length of the strip metal patch 22 in the second layer of metal patches is l4 = 1 mm, the width is w = 0.2 mm, and the diameter of the metallized via 21 is 0.2 mm;
[0060] In one embodiment, the line width w3 of the cross-shaped grid 31 in the third-layer metal patch is 0.3 mm. The third dielectric substrate 8 is a square structure made of Rogers RT 5880 with a relative dielectric constant of 2.2, the side length P is 5 mm, and the thickness H2 is 1.3 mm.
[0061] The following further illustrates the technical effects of the present invention in combination with simulation experiments:
[0062] 1. Simulation conditions and content:
[0063] Using the commercial simulation software HFSS_19.0, the transmission coefficients under incident waves at different angles and the transmission coefficients under polarized waves at different angles of the design scheme are simulated and calculated. The results are as Figure 7 shown in ab.
[0064] 2. Analysis of simulation results:
[0065] Referring to Figure 7 a and b in, the full-wave simulation results of the wave transmission curves of the varactor diode with different capacitance values when the switching diode is conducting and cutoff are respectively shown. It can be seen that the designed example has the characteristic of reconfigurable wave transmission window in a wide frequency band. And compared with the traditional tuning-type RFSS based only on varactor diodes, due to the greater change in the total capacitance between the conducting and cutoff states of the switching diode, the interval between the high-frequency and low-frequency passband ranges is larger, and more suitable passband states can be selected.
[0066] Referring to Figure 8 , by combining and screening all passband states in two ranges, six passband reconstruction states are obtained: the passbands in each state can cover 4.88 GHz - 7.32 GHz, 5.30 GHz - 8.23 GHz, 6.09 GHz - 9.63 GHz, 7.04 GHz - 10.60 GHz, 7.86 GHz - 11.84 GHz, and 8.97 GHz - 14.24 GHz respectively; the -0.8 dB relative bandwidths of each passband are 40%, 43.3%, 45%, 40.4%, 40.4%, and 45.4% respectively. The designed RFSS can achieve wide passband reconstruction in a large range from 4.88 GHz to 14.24 GHz, and the passband has a wide bandwidth and good selectivity. The size of the FSS unit is 0.102λ, and the thickness is 0.07λ, which is the wavelength corresponding to the center frequency of the lowest-frequency passband.
[0067] Referring to Figure 9, four independently adjustable DC regulated power supplies are set for the bias voltage of each variable capacitive surface unit structure. The four arrow-shaped patch structures in each unit are respectively connected to four feed lines through the combination of feed wires and metal vias, and then the DC and AC are separated by the first inductor 17 or the second inductor 57. Since the inductor plays a role of passing DC and blocking AC, it is regarded as an open circuit in the simulation. Thus, four different feed voltages can be loaded on the four arrow-shaped patch structures of each unit. When the feed voltages satisfy the condition: V1 > V2 > V3 > V4, the on-off of the diode and the capacitance value of the varactor diode can be controlled by controlling the voltage difference.
[0068] In summary, the present invention utilizes the characteristics of varactor diodes and switching diodes to achieve five reconfigurable states of the transmission window of the frequency selective surface in the range of 5 GHz to 15 GHz by controlling the voltage difference across the device. The present invention makes up for the deficiencies of the traditional frequency selective surface, such as large unit size, small reconfigurable range of the transmission window, and narrow passband bandwidth; it has the characteristics of large-range reconfigurability of the transmission window, small unit size, and ultra-wide passband, and can be applied to related devices in fields with anti-electromagnetic interference and electromagnetic stealth requirements.
Claims
1. A frequency selective surface with wide-band reconfigurable characteristics of a wave-transmitting window, comprising M×N two-dimensional periodically arranged resonant units, where M≥3 and N≥3, characterized in that, Each of the resonant units includes a first variable capacitive surface unit, a passive inductive surface unit, and a second variable capacitive surface unit arranged from top to bottom; The first variable capacitive surface unit includes a first dielectric substrate (6), a first layer of metal patches (1), and a second layer of metal patches (2); The first layer of metal patches (1) is disposed on the upper surface of the first dielectric substrate (6) and includes four first arrow-shaped metal patches (14). The first arrow-shaped metal patches (14) are composed of a first partial metal patch (141) and a second partial metal patch (142). The shape of the first partial metal patch (141) is an isosceles triangle, and the shape of the second partial metal patch (142) is a T shape. The end of the middle part of the T shape is connected to the center of the base of the isosceles triangle. The apex angles of the isosceles triangles of the four first arrow-shaped metal patches (14) face each other and are centrosymmetrically distributed. There is a gap between the sides of the isosceles triangles of adjacent first arrow-shaped metal patches (14) and they are connected by a first switching diode (13). At the central position of the bottom of each T shape, a second metal connection line (16) is connected through a first variable capacitance diode (15). The two ends of the T-shaped base of the second partial metal patches (142) of two opposite first arrow-shaped metal patches (14) are respectively connected to a first metal connection line (11) through a first inductor (17). The two ends of the T-shaped base of the second partial metal patches (142) of the other two opposite first arrow-shaped metal patches (14) are respectively connected to a third metal connection line (18) through a first inductor (17); The second layer of metal patches (2) includes four strip metal patches (22), and each strip metal patch (22) is respectively connected to a second metal connection line (16) through a first metallized via hole (12) in the first dielectric substrate (6); The passive inductive surface unit includes a second dielectric substrate (7), a third dielectric substrate (8), and a third layer of metal patches (3); the third layer of metal patches (3) is an inductive surface unit disposed on the lower surface of the second dielectric substrate (7) or the upper surface of the third dielectric substrate (8) and is directly below the projection of the middle part of each T shape; The third layer of metal patches (3) is a cross-shaped grid metal patch (31), and in the passive inductive surface units of adjacent resonant units, they are connected through the cross-shaped grid metal patch (31); The second variable capacitive surface unit has the same structure as the first variable capacitive surface unit and is symmetrically arranged with respect to the passive inductive surface unit to achieve ultra-wideband passband characteristics and wide-band reconfigurable characteristics.
2. The frequency selective surface with wideband reconfigurable characteristics of the wave-transmitting window according to claim 1, wherein In the first layer of metal patches (1), each of the first arrow-shaped metal patches (14) is placed opposite to each other on the unit axis, and each of the second metal connection lines (16) is respectively located at the midpoints of the four edges of the unit.
3. The frequency selective surface with wideband reconfigurable characteristics of the wave-transmitting window according to claim 1, characterized in that, The first switching diode (13) is connected between the midpoints of the sides of the isosceles triangle of the adjacent first arrow-shaped metal patch (14) to control the conduction and disconnection of the first arrow-shaped metal patch (14), thereby controlling the magnitude of the distributed capacitance in the gap.
4. The frequency selective surface with the wide-band reconfigurable characteristic of the wave-transparent window according to claim 1, characterized in that The first metal connection line (11), the second metal connection line (16), and the third metal connection line (18) are all strip-shaped metal patches. The length of the third metal connection line (18) is greater than the length of the first metal connection line (11), and the length of the first metal connection line (11) is greater than the length of the second metal connection line (16); the first inductor (17) is a lumped inductor.
5. The frequency selective surface with wideband reconfigurable characteristics of the through-wave window according to any one of claims 1-4 is applied to related devices in fields with requirements for anti-electromagnetic interference and electromagnetic stealth.