A multi-modal reconfigurable frequency selective surface unit structure, radome and communication system

Abstract

The application provides a multi-mode reconfigurable frequency selective surface unit structure, a radome and a communication system, the multi-mode reconfigurable frequency selective surface unit structure comprising: an upper insulating substrate, a lower insulating substrate, a first conductor structure and a second conductor structure constituting a frequency selection pattern, a PIN diode and a varactor diode for regulating the wave-transparent state of the frequency selective surface; the first conductor structure comprising: a square metal feed line, an octagonal metal feed line located inside the square metal feed line, and a first cross metal feed line located inside the octagonal metal feed line; the second conductor structure comprising: a second cross metal feed line, and 4 cross feed lines located at the corners of the lower insulating substrate. The radome and the communication system of the application are both based on the above multi-mode reconfigurable frequency selective surface unit structure. The PIN diode and the varactor diode are used to regulate the wave-transparent state of the frequency selective surface, so that the frequency selective surface can realize the switching of three modes.

Description

Technical Field

[0001] This invention relates to the field of microwave antenna technology, and in particular to a multimode reconfigurable frequency selective surface unit structure, radome, and communication system. Background Technology

[0002] The statements in this section are merely background information relating to this disclosure and do not necessarily constitute prior art.

[0003] With the development of radar and electronic countermeasures technologies, the electromagnetic environment has become increasingly complex, consisting of a dense distribution of numerous, varied, and dynamically alternating electromagnetic signals within a given space. Achieving compatibility between communication detection and electromagnetic stealth in such complex electromagnetic environments has become a crucial research topic in the field of radar radomes.

[0004] A radome is a protective shield that allows electromagnetic waves to pass through. It encloses a millimeter-wave antenna and can effectively protect the millimeter-wave antenna from the influence of the external environment. Although traditional radomes can attenuate the electromagnetic wave signals emitted or received by the antenna to a minimum, they are not suitable for reconfigurable antennas with flexible and variable relationships between array elements. Therefore, reconfigurable frequency-selective radomes have emerged.

[0005] Existing reconfigurable frequency-selective radome technologies generally fall into two categories: one is frequency-tunable transmission, which uses varactor diodes placed in a metal slot structure to adjust the frequency-selective transmission frequency; the other is switchable transmission / reflection mode, typically using pin diodes to control the on / off state of the transmission band. Regardless of whether the transmission frequency is adjustable or the transmission / reflection mode is switchable, the achievable stealth effect is relatively limited and cannot cover the complex environments of the battlefield. Summary of the Invention

[0006] This invention provides a multimode reconfigurable frequency selective surface unit structure, an radome, and a communication system. The cross-shaped structure at the center of the upper and lower insulating substrates is connected to the cross-shaped feed line of the lower insulating substrate via metal vias. The octagonal inner rings of the upper and lower insulating substrates are connected to the cross-shaped feed line of the lower insulating substrate via metal vias. This design creates three different potentials in the outer ring, inner ring, and central cross of the pattern. By controlling the magnitude of these three potentials, the on / off state of the PIN diode and the capacitance of the varactor diode can be controlled. The two feeding networks and tri-polar bias of this invention utilize PIN diodes and varactor diodes to regulate the transmission state of the frequency selective surface, enabling switching between three modes: X-band narrowband tunable transmission, broadband transmission, and full-band reflection.

[0007] The technical solution for achieving the objective of this invention is as follows: On one hand, the present invention provides a multimodal reconfigurable frequency selective surface unit structure, including: an upper insulating substrate, a lower insulating substrate, a first conductor structure and a second conductor structure constituting a frequency selective pattern, and a PIN diode and a varactor diode for controlling the wave transmission state of the frequency selective surface; The first conductor structure is located on the upper surface of the upper insulating substrate and the lower surface of the lower insulating substrate, and the second conductor structure is located on the upper surface of the lower insulating substrate. The first conductor structure includes: a square metal feed line, an octagonal metal feed line located inside the square metal feed line, and a first cross metal feed line located inside the octagonal metal feed line; four PIN diodes are soldered to the middle of two parallel and adjacent sides of the square metal feed line and the octagonal metal feed line, and the four PIN diodes are soldered between the inner ring side of the square metal feed line and the outer ring side of the octagonal metal feed line; a varactor diode is soldered to the middle of each of the four sides of the first cross metal feed line through a slot. The second conductor structure includes: a second cross metal feed line and four cross feed lines located at the corner of the lower insulating substrate; the cross feed lines are connected to the octagonal metal feed line through a first metal via and a first metal pillar opened on the upper and lower insulating substrates, the first metal pillar passing through the first metal via; the second cross metal feed line is connected to the first cross metal feed line through a second metal via and a second metal pillar opened on the lower insulating substrate, the second metal pillar passing through the second metal via.

[0008] Based on one aspect, in one embodiment of the present invention, both the upper insulating substrate and the lower insulating substrate are Rogers 5880 dielectric boards with a thickness of 2 mm, a dielectric constant of 2.2, and a loss tangent of 0.0009.

[0009] In one embodiment of the present invention, the upper insulating substrate and the lower insulating substrate are laminated together using a lamination process.

[0010] In one embodiment of the present invention, both the first conductor structure and the second conductor structure are copper foils.

[0011] Based on one aspect, in one embodiment of the present invention, the cross located at the center of the upper insulating substrate and the lower insulating substrate is connected to the cross feed line through a metal via, and the octagonal inner ring located at the upper insulating substrate and the lower insulating substrate is connected to the cross feed line through a metal via, so that the outer ring, inner ring and central cross of the first conductor structure and the second conductor structure form three different potentials.

[0012] Based on one aspect, in one embodiment of the present invention, the PIN diode is in a forward biased state, the varactor diode is in a reverse biased state, and the radome is in an X-band narrowband adjustable transparent state. The PIN diode is in reverse bias, the varactor diode is in forward bias, and the radome is in broadband transparency. When both the PIN diode and the varactor diode are in a forward bias state, the radome is in a full-band reflection state.

[0013] On the other hand, the present invention provides an antenna radome, which is a frequency selective antenna radome equipped with the above-mentioned multimode reconfigurable frequency selective surface unit structure.

[0014] On the other hand, in one embodiment of the present invention, the multimode reconfigurable frequency selective surface unit structure of the frequency selective radome is arranged periodically.

[0015] In another aspect, the present invention provides a communication system including an antenna equipped with the aforementioned radome.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. To address the problem that existing reconfigurable frequency selective surfaces typically have poor wave transmission and cannot achieve frequency selectivity for incident electromagnetic waves with multiple polarization directions, this invention connects the cross-shaped center of the upper and lower insulating substrates to the cross-shaped feed lines via metal vias. The octagonal inner rings of the upper and lower insulating substrates are also connected to the cross-shaped feed lines via metal vias. This design creates three different potentials in the outer ring, inner ring, and central cross of the pattern. By controlling the magnitude of these three potentials, the on / off state of the PIN diode and the capacitance of the varactor diode can be controlled. The two feeding networks and tri-polar bias of this invention utilize PIN diodes and varactor diodes to regulate the wave transmission state of the frequency selective surface, enabling switching between three modes: X-band narrowband tunable wave transmission, broadband wave transmission, and full-band reflection.

[0017] 2. The upper and lower insulating substrates of the present invention adopt a dual-symmetric frequency selection pattern and feed line, which realizes dual polarization and low insertion loss. In the transmission band, electromagnetic waves of various polarization directions have a transmission window of less than 1dB.

[0018] 3. The present invention places the feed line between two layers of frequency selective patterns, and uses the inductive coupling of the feed line to widen the transmission band of the frequency selective surface, eliminate in-band ripple and depression, and reduce the cross-section of the radome. Attached Figure Description

[0019] Figure 1 This invention provides a three-dimensional multimodal reconfigurable frequency-selective surface unit structure. Figure 1 ; Figure 2 This invention provides a three-dimensional multimodal reconfigurable frequency-selective surface unit structure. Figure 2 ; Figure 3 A schematic diagram of the first conductor structure on the upper insulating substrate and the lower insulating substrate provided by the present invention; Figure 4 A schematic diagram of the second conductor structure on the lower insulating substrate provided by the present invention; Figure 5 This is a simulation diagram of the multimodal reconfigurable frequency-selective surface narrowband tunable transmission state of the present invention; Figure 6 This is a simulation diagram of the multimodal reconfigurable frequency-selective surface broadband transmission state of the present invention; Figure 7 This is a simulation diagram of the multimodal reconfigurable frequency-selective surface total internal reflection state of this invention; Figure 8 Equivalent circuit diagram of the multimodal reconfigurable frequency-selective surface unit structure provided by the present invention; Figure 9 A simplified equivalent circuit diagram of the multimodal reconfigurable frequency-selective surface unit cell structure provided by the present invention; Figure 10 The circuit schematic of the multimodal reconfigurable frequency selective surface unit provided by the present invention; Figure 11 The circuit schematic of the narrowband tunable multimodal reconfigurable frequency selective surface unit provided by the present invention; Figure 12 The circuit schematic diagram of the broadband transparent multimode reconfigurable frequency selective surface unit provided by the present invention; Figure 13 The circuit schematic diagram of the multi-mode reconfigurable frequency-selective surface unit for reflection state provided by the present invention; Reference numerals: 1-Square metal feed line; 2-Octagonal metal feed line; 3-First cross metal feed line; 4-PIN diode; 5-Varactor diode; 6-Second cross metal feed line; 7-Cross feed line; 8-First metal pillar; 9-Second metal pillar; 10-First metal via; 11-Second metal via. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings. However, it should be noted that these embodiments are not intended to limit the present invention. Equivalent changes or substitutions in function, method, or structure made by those skilled in the art based on these embodiments are all within the scope of protection of the present invention.

[0021] The ultra-wideband multimode intelligent stealth radome can dynamically control electromagnetic waves according to functional requirements. It not only has the characteristics of passband wave transmission and out-of-band ultra-wideband wave absorption stealth, but also can dynamically adjust the passband frequency or switch the on / off state under external voltage control. Therefore, it can freely switch between multiple functions such as wideband wave transmission, adjustable wave transmission, and ultra-wideband stealth without changing the physical structure.

[0022] Please see Figure 1 and Figure 2 , Figure 1 A three-dimensional multimodal reconfigurable frequency-selective surface unit structure provided in this embodiment of the invention. Figure 1 , Figure 2 A three-dimensional multimodal reconfigurable frequency-selective surface unit structure provided in this embodiment of the invention. Figure 2 This invention provides a multimodal reconfigurable frequency-selective surface unit structure, including: an upper insulating substrate, a lower insulating substrate, a first conductor structure and a second conductor structure constituting a frequency-selective pattern, and a PIN diode 4 and a varactor diode 5 for controlling the transmission state of the frequency-selective surface. The first conductor structure is located on the upper surface of the upper insulating substrate and the lower surface of the lower insulating substrate, and the second conductor structure is located on the upper surface of the lower insulating substrate. Both the first and second conductor structures are copper foil. Both the upper and lower insulating substrates are made of Rogers 5880 dielectric substrate with a thickness of 2mm, a dielectric constant of 2.2, and a loss tangent of 0.0009. The upper and lower insulating substrates are laminated together using a lamination process. This invention provides a two-layer insulating substrate, and conductor structures can be printed on both sides of the insulating substrate. The second conductor structure is printed on the upper surface of the lower insulating substrate. The upper and lower insulating substrates are laminated together using a PCB lamination process.

[0023] Please see Figure 3 , Figure 3 This is a schematic diagram of the first conductor structure on the upper and lower insulating substrates provided in an embodiment of the present invention. The first conductor structure includes: a square metal feed line 1, an octagonal metal feed line 2 located inside the square metal feed line 1, and a first cross metal feed line 3 located inside the octagonal metal feed line 2; four PIN diodes 4 are welded to the middle of two parallel and adjacent sides of the square metal feed line 1 and the octagonal metal feed line 2, and the four PIN diodes 4 are welded between the inner ring side of the square metal feed line 1 and the outer ring side of the octagonal metal feed line 2; a varactor diode 5 is welded to the middle of each of the four sides of the first cross metal feed line 3 through a slot.

[0024] Please see Figure 4 , Figure 4This is a schematic diagram of a second conductor structure located on the upper surface of a lower insulating substrate according to an embodiment of the present invention. The second conductor structure includes: a second cross metal feed line 6 and four cross feed lines 7 located at the corners of the lower insulating substrate; the cross feed lines 7 are connected to the octagonal metal feed line 2 through a first metal via 10 and a first metal pillar 8 opened in the insulating substrate, and the second cross metal feed line 6 is connected to the first cross metal feed line 3 through a second metal via 11 and a second metal pillar 9 opened in the insulating substrate.

[0025] Please continue reading. Figure 1 and Figure 2 In this embodiment of the invention, the cross-shaped structure located at the center of the upper and lower insulating substrates is connected to the cross-shaped feed line through metal vias. The octagonal inner ring located on the upper and lower insulating substrates is connected to the cross feed line 7 through metal vias, so that the outer ring, inner ring, and central cross of the first and second conductor structures form three different potentials. When the PIN diode 4 is forward biased and the varactor diode 5 is reverse biased, the radome is in an X-band narrowband adjustable transmission state; when the PIN diode 4 is reverse biased and the varactor diode 5 is forward biased, the radome is in a broadband transmission state; when both the PIN diode 4 and the varactor diode 5 are forward biased, the radome is in a full-band reflection state.

[0026] This invention provides a radome, which is a frequency selective radome equipped with the aforementioned multimode reconfigurable frequency selective surface element structure. Preferably, the multimode reconfigurable frequency selective surface element structure of the frequency selective radome is arranged periodically. Furthermore, this invention also provides a communication system including an antenna equipped with the aforementioned radome.

[0027] To address the issue that existing reconfigurable frequency selective surfaces typically exhibit poor wave transmission and fail to provide frequency selectivity for incident electromagnetic waves with multiple polarization directions, this invention proposes a design where the cross-shaped structure at the center of the upper and lower insulating substrates is connected to a cross-shaped feed line via metal vias, and the octagonal inner ring of the upper and lower insulating substrates is connected to the cross-shaped feed line via metal vias. This design creates three different potentials for the outer ring, inner ring, and central cross of the pattern. By controlling the magnitude of these three potentials, the on / off state of the PIN diode and the capacitance of the varactor diode can be controlled. This invention employs PIN diodes and varactor diodes to regulate the wave transmission state of the frequency selective surface using two feeding networks and a tri-polar bias voltage, enabling switching between three modes: X-band narrowband tunable wave transmission, broadband wave transmission, and full-band reflection.

[0028] In this embodiment of the invention, the upper and lower insulating substrates employ dual-symmetric frequency selective patterns and feed lines, achieving dual polarization and low insertion loss. In the transmission band, electromagnetic waves of various polarization directions have a transmission window of less than 1 dB. This embodiment places the feed line between the two frequency selective patterns, utilizing the inductive coupling of the feed line to widen the transmission band of the frequency selective surface, eliminating in-band ripple and dips, and reducing the profile of the radome.

[0029] The feeding method of a multimode reconfigurable frequency selective surface unit (MSU) structure according to an embodiment of the present invention is referred to as a sandwich-coupled feeding structure. In the design of an MSU, the feed line design is a crucial part because the diodes require power. Since the MSU is a periodically arranged array of cells, the feed line needs to cover each cell, often placed on the back side of the cell. However, the presence of metal feed lines often affects the frequency response of the cell itself, introducing parasitic capacitance and inductance, causing unavoidable high-order resonances, and degrading the performance of the MSU. A traditional solution is to connect a choke inductor in series in the feed line to reduce its influence on high-frequency electromagnetic waves in space. However, this solution often requires soldering a large number of choke inductors, increasing cost and processing difficulty, and still cannot completely eliminate the influence of the feed line on the performance of the MSU.

[0030] This invention places a feed line between two identical multimode reconfigurable frequency selective surface unit (MSU) patterns. The MSU patterns and the feed line are connected via metal vias, integrating the feed line into the overall structure of the MSU. The two MSU patterns and the feed line can undergo inductive coupling, forming two coupling cavities. These two coupling cavities can form a flat third-order passband, the mechanism of which is as follows: Figure 8 As shown, Figure 8 This is an equivalent circuit diagram of the multimode reconfigurable frequency selective surface unit structure provided in an embodiment of the present invention. In the equivalent circuit analysis, since the multimode reconfigurable frequency selective surface unit is a bandpass frequency selective surface, its equivalent circuit can be considered as a parallel LC structure. The dielectric substrate can be equivalent to a transmission line with a characteristic impedance of Z1, and the internal feed line can be equivalent to an inductor L1. Because the transmission line can be equivalent to... The circuit can be further simplified to a shape network. Figure 9The simplified equivalent circuit diagram of the multimode reconfigurable frequency selective surface unit (MSU) structure is shown. After simplification, the sandwich-structured MSU exhibits third-order bandpass characteristics, with the parallel LC structures coupled by inductor L3, creating a flat passband. By adjusting the length and width of the feed line, the equivalent inductance L1 can be controlled in this embodiment, at which point the center frequency of the passband... for:

[0031] Therefore, introducing a sandwich-coupled feeding structure can effectively broaden the passband of the multimode reconfigurable frequency selective surface unit (MSF) and eliminate its in-band ripple. This feeding method innovatively eliminates the influence of traditional feeders on the performance of MSFs and optimizes their performance by utilizing the distributed inductance characteristics of the feeder, representing a pioneering exploration of active metasurface feeding methods. In practical applications, because the feeder is wrapped between two layers of MSFs, its performance is more stable, less susceptible to erosion, and the feeding is more stable.

[0032] Designing metasurfaces to achieve their intended functions is the most crucial issue in the design process. Currently, most design approaches involve full-wave simulation using electromagnetic simulation software, followed by parameter sweep analysis to optimize the structure and achieve the desired functionality. This invention proposes a circuit analysis method that analyzes the model from the perspective of the metasurface's equivalent circuit, guiding modeling and design. To achieve a metasurface with three reconfigurable states, this invention designs circuit schematics for each state, and then synthesizes the metasurface model parameters based on the calculation formulas for distributed capacitance and inductance, guiding the metasurface's modeling and design. This design approach is clear and saves the time required for parameter sweeping in traditional design methods. An equivalent circuit for a multimodal reconfigurable frequency-selective surface cell is constructed, such as... Figure 10 As shown. A PIN diode can be approximated as an inductor in the forward-biased state and as a small capacitor in the reverse-biased state. A varactor diode can be approximated as an inductor in the forward-biased state and as a variable capacitor in the reverse-biased state. By controlling the switching on and off of the varactor diode and PIN diode in the circuit schematic, the circuit schematic can be further simplified, realizing the switching of various operating states of the multimode reconfigurable frequency selective surface unit. When the multimode reconfigurable frequency selective surface unit operates in the narrowband adjustable state, its equivalent circuit is as follows. Figure 11 As shown, by controlling the value of the variable capacitor C1, the passband frequency of this multimode reconfigurable frequency-selective surface unit can be adjusted. The passband center frequency... It can be calculated using formula (2):

[0033] In this circuit schematic, the embodiment of the invention uses a smaller L1 value to reduce the Q value of the parallel resonator, achieving narrowband transmission. Simultaneously, C1 and L3 form a series resonant circuit, allowing the multimode reconfigurable frequency selective surface unit to generate a zero at the right end of the passband, thereby further enhancing the passband selectivity. This zero frequency... It can be calculated using formula (3):

[0034] The circuit model is adopted as a third-order bandpass configuration, with the two coupling cavities connected by a transmission line with a characteristic impedance of Z1. This approach further improves the flatness of the passband. When the multimode reconfigurable frequency-selective surface unit operates in broadband mode, the varactor diode is in the conducting state, and the PIN diode is in the cutoff state. The circuit principle is as follows: Figure 12 As shown. At this point, L1 is larger, the Q value of the parallel resonator is larger, and the transmission band is wider. Similarly, the series resonator composed of L1 and C3 also introduces a transmission zero on the right side of the passband, enhancing the selectivity of the passband. When the multimode reconfigurable frequency selective surface unit operates in reflection mode, both the PIN diode and the varactor diode are forward biased, and its circuit principle is as follows. Figure 13 As shown, the large inductor L1 enables the multimode reconfigurable frequency selective surface unit to exhibit full-band reflection characteristics. Next, the structure of this frequency selector is synthesized using the adopted circuit schematic. To achieve dual polarization, the model is adopted as a centrally symmetric structure, as shown below. Figure 13 As shown. The metal strip along the direction of the electric field can be considered equivalent to an inductor, and the metal strip perpendicular to the direction of the electric field can be considered equivalent to a capacitor. In this structure, let... d The width of the metal strip. p For the metal strip period, The angle of incidence of the electromagnetic wave. The wavelength of electromagnetic waves, The angular frequency of electromagnetic waves. It is the free-space wave impedance. Then the capacitive reactance of the metal strip... It can be calculated using the following formula:

[0035]

[0036]

[0037]

[0038]

[0039]

[0040] Therefore, embodiments of the present invention can guide the adoption of the model based on the circuit schematic, thereby determining the shape of the model and the thickness of the patches.

[0041] Since this embodiment of the invention uses a sandwich structure to feed the multimode reconfigurable frequency selective surface unit (MSF), metal vias are a crucial connection structure in the feeding process. However, a significant coupling capacitance exists between the metal vias of adjacent units, which can degrade the performance of the MSF. To reduce and eliminate this coupling capacitance, this embodiment of the invention introduces a series inductor between adjacent vias using a cross feed line 7 (cross-shaped feed line), effectively decoupling the coupling capacitance. Simultaneously, the octagonal inner ring structure allows the vias around the perimeter to be further away from the periodic boundary, reducing the magnitude of the coupling capacitance between the vias of adjacent units.

[0042] In summary, the multimodal reconfigurable frequency-selective surface unit structure of this invention has three copper layers. The dielectric substrate uses Rogers 5880 with a thickness of 2mm, a dielectric constant of 2.2, and a loss tangent of 0.0009. Two dielectric layers are laminated together using a lamination process, where h is the total thickness of the model. The gray areas represent metal vias that connect the three copper layers. Figure 3 This is a schematic diagram of the parameters of the top-level structure. The top-level structure has the same pattern as the bottom-level structure. P is the structural period, s1 is the outer ring width, s2 is the octagonal inner ring width, s3 is the distance between the inner and outer rings, d1 is the side length of the octagonal inner ring, and s4 is the width of the PIN diode solder joint. Figure 4 Figure 5 shows the parameters of the intermediate layer metal feed line. d2 is the linewidth of the cross feed line, s5 is the linewidth of the cross feed line, and d3 is the spacing between the via and the cross feed line. When the elements are arranged periodically, the cross at the center of the top and bottom layers is connected to the cross feed line of the intermediate layer through metal vias, and the octagonal inner rings of the top and bottom layers are connected to the cross feed line of the intermediate layer through vias. This design creates three different potentials for the outer ring, inner ring, and central cross of the pattern. By controlling the magnitude of these three potentials, the on / off state of the PIN diode and the capacitance of the varactor diode can be controlled. When the PIN diode is forward biased and the varactor diode is reverse biased, the S-parameter simulation results are shown in Figure 5, indicating that the radome is in an X-band narrowband adjustable transmission state. Changing the voltage across the varactor diode can adjust the frequency of the transmission window; the 1dB transmission window bandwidth is greater than 500MHz. When the PIN diode is reverse biased and the varactor diode is forward biased, the radome is in a broadband transmission state, as shown in the S-parameter simulation results. Figure 6 As shown, the relative bandwidth of the 1dB transmission window is greater than 20%. When both the PIN diode and the varactor diode are forward biased, the radome exhibits full-band reflection. The S-parameter simulation results are as follows: Figure 7As shown, the feeder is designed between two layers of frequency selection units, which not only reduces the profile and structural complexity, but also provides inductive coupling between the two layers, eliminating in-band ripple and dips.

[0043] This invention significantly increases the number of operating modes of the reconfigurable frequency-selective radome without increasing the structural cross-section, enabling the radome to possess multi-mode intelligent stealth capabilities and three operating modes: narrowband tunable wave transmission, broadband wave transmission, and full-band reflection. This provides a more comprehensive and intelligent stealth effect for various communication antennas within the radome.

[0044] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

[0045] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0046] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A multimodal reconfigurable frequency-selective surface unit structure, characterized in that, include: Upper insulating substrate, lower insulating substrate, first conductor structure and second conductor structure constituting frequency selective pattern, PIN diode and varactor diode for controlling the frequency selective surface transmittance state; The first conductor structure is located on the upper surface of the upper insulating substrate and the lower surface of the lower insulating substrate, and the second conductor structure is located on the upper surface of the lower insulating substrate. The first conductor structure includes: a square metal feed line, an octagonal metal feed line located inside the square metal feed line, and a first cross metal feed line located inside the octagonal metal feed line; four PIN diodes are soldered to the middle of two parallel and adjacent sides of the square metal feed line and the octagonal metal feed line, and the four PIN diodes are soldered between the inner ring side of the square metal feed line and the outer ring side of the octagonal metal feed line; a varactor diode is soldered to the middle of each of the four sides of the first cross metal feed line through a slot. The second conductor structure includes: a second cross metal feed line and four cross feed lines located at the corner of the lower insulating substrate; the cross feed lines are connected to the octagonal metal feed line through a first metal via and a first metal pillar opened on the upper and lower insulating substrates, the first metal pillar passing through the first metal via; the second cross metal feed line is connected to the first cross metal feed line through a second metal via and a second metal pillar, the second metal pillar passing through the second metal via; The cross located at the center of the upper and lower insulating substrates is connected to the cross feed line through metal vias, and the octagonal inner ring located at the center of the upper and lower insulating substrates is connected to the cross feed line through metal vias, so that the outer ring, inner ring and central cross of the first conductor structure and the second conductor structure form three different potentials. The PIN diode is in a forward biased state, the varactor diode is in a reverse biased state, and the frequency-selective surface unit structure is an X-band narrowband adjustable transparent state. The PIN diode is in reverse bias, the varactor diode is in forward bias, and the frequency-selective surface unit structure is in broadband transparent state. When both the PIN diode and the varactor diode are in a forward bias state, the frequency selective surface unit structure is in a full-band reflection state.

2. The multimodal reconfigurable frequency-selective surface unit structure according to claim 1, characterized in that, The upper and lower insulating substrates are made of Rogers 5880 dielectric substrate with a thickness of 2mm, a dielectric constant of 2.2, and a loss tangent of 0.0009.

3. The multimodal reconfigurable frequency-selective surface unit structure according to claim 1, characterized in that, The upper insulating substrate and the lower insulating substrate are laminated together using a lamination process.

4. The multimodal reconfigurable frequency-selective surface unit structure according to claim 1, characterized in that, Both the first conductor structure and the second conductor structure are copper foil.

5. An antenna radome, characterized in that, The radome is equipped with a multimode reconfigurable frequency selective surface unit structure as described in any one of claims 1-4.

6. The radome according to claim 5, characterized in that, The multimode reconfigurable frequency-selective surface unit structure of the frequency-selective radome is arranged in a periodic manner.

7. A communication system, characterized in that, Includes an antenna equipped with a radome as described in claim 5 or 6.

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