Polarization conversion unit, polarization conversion surface, and electromagnetic cloaking slot antenna

Abstract

The application belongs to the technical field of antennas and relates to a polarization conversion unit, a polarization conversion surface and an electromagnetic stealth slot antenna. The polarization conversion unit comprises, from top to bottom, a patch layer, a dielectric layer and a ground layer. The patch layer comprises a first part and two second parts. The first part and the second parts are rectangular structures, and the edges of the two second parts partially overlap the edges of the first part, so that the patch layer forms a central symmetric structure. The center of the patch layer is directly above the center of the dielectric layer, and the patch layer is distributed along the diagonal of the dielectric layer. The length of the first part is greater than the length of the second part, the width of the first part is twice the width of the second part, and the two vertices of the first part on the same diagonal are respectively arranged at the midpoint of the long side of a second part. The application can reduce the scattering performance while normally radiating electromagnetic waves.

Description

Technical Field

[0001] This application relates to the field of antenna technology, and in particular to polarization conversion units, polarization conversion surfaces, and electromagnetic stealth slot antennas. Background Technology

[0002] Radar detection technology has seen rapid development and innovation in recent years. Unlike in the past, the modern environment is undergoing many changes, accompanied by changes in the form of electronic information. Therefore, enhancing our stealth capabilities in this rapidly changing environment, and thus improving our ability to penetrate defenses, is a key technology that countries worldwide highly value. Thus, accelerating research into the stealth performance of equipment and devices is extremely important.

[0003] Radar Cross Section (RCS) characterizes a target's stealth performance. For missiles, fighter jets, and other flight combat platforms, stealth performance determines their survivability on the battlefield, making it crucial to reduce RCS values. Various communication antennas are inevitably installed on aircraft platforms, and their metallic nature and large size result in electromagnetic energy scattering, which has become the largest contributor to the total RCS of the aircraft. As devices that radiate or receive electromagnetic waves, antennas exhibit contradictory radiation and scattering performance. Therefore, ensuring that antennas can radiate electromagnetic waves normally while minimizing their scattering performance is a critical technology that urgently needs to be mastered.

[0004] Currently, there are various existing technologies that can reduce RCS, such as changing the surface structure of the target, loading absorbing materials, adding active or passive impedance, and loading frequency-selective surfaces.

[0005] However, the above methods cannot reduce scattering performance while radiating electromagnetic waves normally. Summary of the Invention

[0006] Therefore, it is necessary to provide a polarization conversion unit, a polarization conversion surface, and an electromagnetic stealth slot antenna to address the above-mentioned technical problems, which can reduce scattering performance while radiating electromagnetic waves normally.

[0007] The polarization conversion unit includes, from top to bottom, a patch layer, a dielectric layer and a ground layer;

[0008] The patch layer includes a first part and two second parts; both the first part and the second parts are rectangular structures, and one side of each of the two second parts partially overlaps with one side of the first part, so that the patch layer forms a centrally symmetrical structure.

[0009] In one embodiment, the center of the patch layer is located directly above the center of the dielectric layer, and the patch layer is distributed along the diagonal of the dielectric layer.

[0010] In one embodiment, the length of the first part is greater than the length of the second part, the width of the first part is twice the width of the second part, and the two vertices of the first part located on the same diagonal are respectively set at the midpoint of the long side of the second part.

[0011] The polarization conversion surface includes: multiple polarization conversion units, which are divided into four equal groups and located in the four quadrants respectively;

[0012] Each group of polarization conversion units is arranged in an array, and the four groups of polarization conversion units are centrally symmetrically distributed.

[0013] In one embodiment, each group of polarization conversion units is distributed in a square array.

[0014] In one embodiment, the patch layer of each polarization conversion unit points to the center of the polarization conversion surface.

[0015] Electromagnetic stealth slot antenna, comprising: slot antenna array and polarization conversion surface;

[0016] The polarization conversion surface is positioned above the slot antenna array.

[0017] In one embodiment, a through hole is provided on the polarization conversion surface at the position corresponding to each slot of the slot antenna array to fully expose each slot.

[0018] In one embodiment, the slot antenna array includes: a radiating layer, a substrate layer, and a feed layer stacked sequentially from top to bottom;

[0019] The slit is located on the radiation layer, and the polarization conversion surface abuts against the top of the radiation layer.

[0020] In one embodiment, the power feed layer includes: three T-type power dividers; each T-type power divider includes an input terminal and two output terminals, with the two output terminals symmetrically distributed about the input terminal.

[0021] The first T-type power divider and the second T-type power divider are symmetrically distributed about the third T-type power divider.

[0022] The output of the first T-type power divider extends towards the input to form an E-type structure. The inputs of the first and second T-type power dividers are used as the outputs of the third T-type power divider to form a one-to-four power divider feeder network.

[0023] The aforementioned polarization conversion unit, polarization conversion surface, and electromagnetic stealth slot antenna were designed first. The polarization conversion unit achieved a polarization conversion rate exceeding 0.9. Further, a polarization conversion surface was obtained by assembling the elements in a mirror checkerboard pattern. The cross-polarization conversion rate exceeded 0.9 within the 7.4-15.6 GHz bandwidth. Since the polarization conversion units in adjacent quadrants differed by 180° in direction, the reflected waves also differed by 180°. This phase cancellation resulted in a reduction in the RCS, achieving electromagnetic stealth. Furthermore, the polarization conversion surface was loaded onto the surface of the slot antenna array, and a 1-to-4 equal power distribution feed network was designed for the array. The antenna's radiation performance did not deteriorate, and the RCS was reduced by at least 5 dB within the 7.4-15.6 GHz band, significantly reducing the antenna's scattering characteristics. The simulated and measured radiation performance of this application are excellent, especially in terms of electromagnetic stealth. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the polarization conversion unit in one embodiment, where (a) is a top view and (b) is a side view;

[0025] Figure 2 This is a structural simulation model diagram of the polarization conversion unit in one embodiment;

[0026] Figure 3 In one embodiment, the cross-polarization and co-polarization of the polarization conversion unit are given.

[0027] Figure 4 This is a schematic diagram of the polarization conversion rate of a polarization conversion unit in one embodiment;

[0028] Figure 5 This is a schematic diagram of the polarization conversion surface in one embodiment;

[0029] Figure 6 This is a comparison of the monostation RCS of a polarization conversion surface and a perfect conductor in one embodiment;

[0030] Figure 7 Here are 3D mode RCS diagrams of the polarization conversion surface of this application and the polarization conversion surface of the prior art in one embodiment, wherein (a) is the 3D mode RCS diagram of the polarization conversion surface of this application, and (b) is the 3D mode RCS diagram of the polarization conversion surface of the prior art.

[0031] Figure 8 This is a schematic diagram of the electromagnetic stealth slot antenna in one embodiment;

[0032] Figure 9 This is a schematic diagram of a one-to-two T-type power divider in one embodiment, wherein (a) is a structural schematic diagram, (b) is a structural model diagram, and (c) is a transmission line model diagram;

[0033] Figure 10 Here is a schematic diagram of a one-to-four power distribution network structure in one embodiment, where (a) is a simulation model diagram and (b) is a schematic diagram of the structure.

[0034] Figure 11 This is a port matching characteristic diagram of a one-to-four power distribution network in one embodiment.

[0035] Figure 12 This is a schematic diagram of a reference antenna in one embodiment;

[0036] Figure 13 The following is a simulation result diagram of the reflection parameters of two antennas in one embodiment;

[0037] Figure 14 This is a radiation E-plane pattern of two antennas in one embodiment;

[0038] Figure 15 The figure shows the monostation RCS simulation results for two antennas in one embodiment;

[0039] Figure 16 The following are physical diagrams of two antennas in one embodiment, wherein (a) is an electromagnetic stealth slot antenna and (b) is a reference antenna;

[0040] Figure 17 This is a radiation pattern of two antennas at 9.5 GHz in one embodiment;

[0041] Figure 18 The image shows a monostation RCS test diagram of two antennas in one embodiment, where (a) is an electromagnetic stealth slot antenna and (b) is a reference antenna.

[0042] Figure 19 This is a comparison chart of the monostation RCS results for two antennas in one embodiment. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0044] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0045] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of those features. In the description of this application, "multiple sets" means at least two sets, such as two sets, three sets, etc., unless otherwise explicitly specified.

[0046] In this application, unless otherwise expressly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0047] Furthermore, the technical solutions of the various embodiments of this application can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this application.

[0048] This application provides a polarization conversion unit, such as Figure 1 As shown, in one embodiment, it includes: a patch layer, a dielectric layer, and a floor layer.

[0049] The relationship between the layers is as follows: the patch layer, dielectric layer, and ground layer are stacked sequentially from top to bottom. Preferably, the patch layer, dielectric layer, and ground layer are all the same shape and size, so that the polarization conversion unit forms a right prism structure or a cylindrical structure. More preferably, the patch layer, dielectric layer, and ground layer are squares of the same size, so that the polarization conversion unit forms a hexahedral structure.

[0050] The patch layer is disposed on top of the dielectric layer and includes: a first part and two second parts; both the first part and the second part are rectangular structures, and one side of each of the two second parts partially overlaps with one side of the first part, so that the patch layer forms a centrally symmetrical metal structure.

[0051] Preferably, the center of the patch layer is located directly above the center of the dielectric layer, and the patch layer is distributed along the diagonal of the dielectric layer so that the patch layer forms a lightning-shaped structure.

[0052] More preferably, the length of the first part is greater than the length of the second part, the width of the first part is twice the width of the second part, the two vertices of the first part located on the same diagonal are respectively set at the midpoint of the long side of the second part, and both the first part and the second part are at 45° with the horizontal line to achieve a polarization conversion rate greater than 0.9 and a better polarization conversion effect.

[0053] The dielectric layer is made of F4B with a dielectric constant of 2.65 and a loss tangent of 0.001.

[0054] The floor layer is located at the bottom of the dielectric layer, and the material used is PEC, a perfect conductor.

[0055] The aforementioned polarization conversion unit (PCM unit) is a type of metasurface unit capable of rotating the polarization direction by 90 degrees, achieving a polarization conversion rate greater than 0.9 over a wide frequency band. This allows for better RCS reduction (10dB) over an extremely wide frequency range by controlling the polarization of electromagnetic waves. By using these metasurface units to form a metasurface, electromagnetic wave polarization can be controlled. When electromagnetic waves irradiate a target, the polarization direction of the incident wave can be changed, rotating it by a certain angle. Simultaneously, the amplitude and phase can be adjusted, effectively obtaining the desired properties and creating a polarization conversion surface. Different polarization conversion surfaces can be designed to alter the polarization state of electromagnetic waves, achieving electromagnetic stealth through phase cancellation, thus applicable to a wide range of scenarios. In aircraft platforms such as missiles and fighter jets where radar antennas are used, stealth can be achieved. In common electromagnetic wave scenarios, polarization conversion surfaces can adjust the polarization performance of light. In satellite communication and radar navigation fields, polarization conversion surfaces can meet specific electromagnetic wave requirements.

[0056] In a specific embodiment, such as Figure 2 As shown in Table 1, the designed polarization conversion unit was modeled using the electromagnetic simulation software CST2020. The analysis adopted Floquet's periodic theorem and set the structure of the polarization conversion unit to be perpendicularly irradiated by a plane electromagnetic wave. Under the condition of consistent polarization conversion units, the physical properties exhibited by the metasurface structure can be analyzed. The target parameters were set for simulation, specifically including setting the plane polarization mode and incident angle in the model, and obtaining a high polarization conversion rate (PCR) of the polarization conversion unit through the post-processing module.

[0057] Table 1 Structural dimensions of the polarization conversion unit

[0058] Parameter name Parameter value (mm) p 6 l1 2 l2 3.5 w1 0.5 w2 1

[0059] Irradiating the polarization conversion unit with a plane electromagnetic wave whose main polarization is y-polarized along the normal direction, the resulting cross-polarization and co-polarization are as follows: Figure 3 As shown, cross-polarization represents the cross-polarization reflection coefficient ryx, and co-polarization represents the co-polarization reflection coefficient ryy. Within the simulation's frequency range of 2-18 GHz, the phase difference varies from -π to π. or When, it indicates the transition from electromagnetic line polarization to cross polarization. Figure 3 There are three resonant points in total, located at 7.86 GHz, 11.23 GHz, and 16.62 GHz, corresponding to the minimum ryy and the maximum ryx. According to the PCR formula:

[0060]

[0061] Therefore, the smaller ryy is, the greater the polarization conversion rate, and the better the polarization conversion effect of the polarization conversion unit. The y-polarized wave is almost completely converted into the x-polarized wave. In other words, the polarization conversion unit can convert the y-polarized wave into the cross-polarized wave over a wide frequency band, and the conversion efficiency is very high.

[0062] like Figure 4 As shown, the polarization conversion efficiency of the polarization conversion unit is displayed when a y-polarized electromagnetic wave is incident along the normal direction of the polarization conversion unit. The polarization conversion efficiency of this structure exceeds 90% in the 7.4–15.6 GHz range, indicating that within this range, the y-polarized wave is essentially converted into an x-polarized wave (polarized wave), and the designed polarization conversion unit exhibits a high polarization conversion efficiency over a wide frequency band. Furthermore, three peaks are observed at 7.86 GHz, 11.23 GHz, and 16.62 GHz, indicating that the polarization rotation rate of the polarization conversion unit is close to 100%. The polarization conversion unit demonstrates excellent performance.

[0063] This application also provides a polarization conversion surface, such as Figure 5 As shown, in one embodiment, it includes: a plurality of polarization conversion units, which are divided into four groups of equal number and respectively located in the four quadrants; each group of polarization conversion units is arranged in an array, and the four groups of polarization conversion units are centrally symmetrically distributed.

[0064] Preferably, each group of polarization conversion units is distributed in a square array.

[0065] More preferably, the patch layer of each polarization conversion unit points to the center of the polarization conversion surface to form a symmetrical structure and achieve better RCS reduction.

[0066] The aforementioned polarization conversion surface arranges the polarization conversion units and their mirror units in a checkerboard pattern, distributing the polarization conversion units across four different quadrants. Due to this checkerboard arrangement, when a plane wave illuminates the polarization conversion unit along the same direction, the mirror structures in adjacent quadrants can perform polarization conversion. The polarization conversion surface can rotate the polarization direction of the electromagnetic wave by 90°, thus achieving a 180° phase difference in the reflected wave. These two components cancel each other out, decomposing the electromagnetic wave away from the normal direction and dispersing it to the four corners, thereby achieving RCS reduction capability. Furthermore, the cross-polarization conversion rate exceeds 0.9 within the 7.4-15.6 GHz bandwidth, and the RCS value is reduced over a wide frequency band, achieving electromagnetic stealth functionality for both the polarization conversion surface and the antenna. Simultaneously, the polarization conversion surface has a low profile, making it easy to load onto the antenna surface to meet conformal requirements, and its thin and lightweight structure avoids the complex manufacturing process of traditional structures.

[0067] In one specific embodiment, the polarization conversion units are distributed in a 5×5 array to form four sets of polarization conversion unit arrays. Two sets are distributed in the second and fourth quadrants, and the other two sets are mirror images distributed in the first and third quadrants, together forming a polarization conversion metasurface. Simulations are performed, using the RCS of a metal plate as a reference, to analyze the single-station RCS reduction capability of the polarization conversion surface.

[0068] like Figure 6 As shown, the monostatic RCS values ​​(RCS on the normal phase of the antenna surface when the transmitting and receiving antennas are aligned and the included angle is 0 degrees) of PCM_1 and PCM_2 are displayed. PCM_1 represents the polarization conversion surface in the prior art, and PCM_2 represents the polarization conversion surface of this application. The RCS reduction is observed by comparison. In PCM_1, when a y-polarized electromagnetic wave is incident on the polarization conversion unit, it will reflect an x-polarized electromagnetic wave with the same amplitude. Therefore, for this metasurface, the RCS value is not reduced compared to that of a perfect conductor (PEC). However, in PCM_2, the polarization conversion units and their mirror images are arranged in the four quadrants of the polarization conversion surface, causing their reflected waves to be out of phase and resulting in phase cancellation. In the 7.4 GHz to 15.6 GHz frequency band, the single-station RCS is reduced by more than 5 dB. At the same time, when the polarization conversion rate of the polarization conversion unit is greater than 0.9, the frequency band is basically consistent, and the best RCS reduction is achieved at the three resonant points of 7.86 GHz, 11.23 GHz and 16.62 GHz. The electromagnetic stealth effect of the polarization conversion surface can be achieved through the design of the polarization conversion unit.

[0069] like Figure 7As shown, the 3D scattering modes of two different checkerboard structures under vertical incidence at 7.8 GHz are illustrated, allowing for a more intuitive comparison of RCS reduction. The checkerboard structure of this application uniformly distributes the energy of vertically incident electromagnetic waves in four directions, significantly weakening the electromagnetic wave energy originally reflected back along the normal direction and dispersing it to other non-normal directions. This results in a smaller normal component, reduced main lobe power, and the arrangement of polarization conversion units and their mirror images in the four quadrants of the polarization conversion surface. This causes their reflected waves to be out of phase and lead to phase cancellation, significantly reducing the electromagnetic wave energy in the normal direction and thus achieving electromagnetic stealth.

[0070] This application also provides an electromagnetic stealth slot antenna, such as Figure 8 As shown, in one embodiment, it includes: a slot antenna array and a polarization conversion surface; the polarization conversion surface is disposed above the slot antenna array.

[0071] The slotted antenna array comprises, from top to bottom, a radiating layer, a substrate layer, and a feed layer. The radiating layer has slots and is made of a metallic material. The substrate layer is made of F4B. The feed layer is a power divider.

[0072] A power divider is a passive device that can split a single signal into multiple signals for transmission. For example... Figure 9 As shown, a T-type power divider can also be considered a three-port network. Port 1 is the input terminal with an input signal power of P1, and ports 2 and 3 are the output terminals with output powers of P2 and P3, respectively. Ideally, according to the law of conservation of energy, P1 = P2 + P3. The signal enters from port 1, and after power distribution, exits from ports 2 and 3. Ports 2 and 3 should generally have equal power. Z0, Z1, and Z2 are the characteristic impedances of the transmission lines at ports 1, 2, and 3, respectively. At the nodes, this is equivalent to a lumped susceptance. To ensure complete signal transmission, the parallel impedance of Z1, Z2, and jB must match Z0. This requires satisfying the following:

[0073]

[0074] At this point, the signal is not reflected at the T-junction. Ports 2 and 3 can also be allocated according to the Z2:Z1 ratio. For example, in a 1-to-2 power divider, Z2:Z1 = 1, then Z1 = Z2 = 2 * Z0. In this case, a quarter-wavelength impedance transformer is usually used to transform the impedances of Z1 and Z2 to the desired value, such as 50 ohms.

[0075] Preferably, the feed layer includes: three T-type power dividers; each T-type power divider includes one input terminal and two output terminals, with the two output terminals symmetrically distributed about the input terminal; the first and second T-type power dividers are symmetrically distributed about the third T-type power divider; the output terminal of the first T-type power divider extends towards the input terminal to form an E-type structure, and the input terminals of the first and second T-type power dividers are used as the output terminals of the third T-type power divider to form a 1-to-4 power divider feed network, which can be used for a 2×2 slot antenna array to ensure that each slot can receive equal amplitude and in-phase excitation.

[0076] like Figure 10 As shown, a 1-to-4 power distribution network was modeled and simulated, and its performance results were obtained. In the simulation model, the input port was set to port 1, and the four output ports were ports 2, 3, 4, and 5, respectively. The simulation results are as follows. Figure 11 As shown, within the 8-12GHz range, the S11 values ​​of the 1-to-4 power divider network are all below -15dB, indicating that the input port of the 1-to-4 power divider network is well matched and the reflected wave is small. The simulation values ​​S21, S31, S41, and S51 of the 1-to-4 power divider network reflect the energy transfer from the input port to the output port. The closer the two values ​​are, the better the power distribution effect of the power divider phase shifter. The difference between the two values ​​is about -6.5dB, indicating that the more energy the power divider transmits to the output port, the less the loss.

[0077] The polarization conversion surface abuts against the top of the radiating layer, and a through hole is provided on the polarization conversion surface at the position corresponding to each slot of the slot antenna array to fully expose each slot.

[0078] It should be noted that, due to the presence of through holes on the polarization conversion surface, the number of polarization conversion units is no longer a square number.

[0079] The aforementioned electromagnetic stealth slotted antenna incorporates a polarization conversion surface onto the surface of the slotted antenna array and employs a 1-to-4 equal power distribution network. This design achieves better feeding and impedance matching, resulting in superior power distribution. While maintaining its original radiation performance, the antenna's RCS is reduced by at least 5 dB within the 7.4-15.6 GHz band, significantly reducing its scattering characteristics and achieving electromagnetic stealth. Simulations and measured radiation performances of this application are excellent, particularly in electromagnetic stealth. Furthermore, the electromagnetic stealth slotted antenna of this application offers advantages such as integrability, ease of arraying, ease of fabrication, strong concealment, low profile radiation efficiency, and high aperture utilization. It meets conformal requirements and can be perfectly integrated with the aircraft platform while radiating electromagnetic waves for radar detection, without incurring additional area requirements. It is particularly suitable for aircraft and other equipment systems and can be extended to more platforms such as land-based and water-based systems, demonstrating significant value in the field of communications.

[0080] In a specific embodiment, such as Figure 12 As shown, the reference antenna measures 60mm × 60mm and is a 2×2 slotted antenna array. The radiating layer is a metal plate with four slots, printed on a 1mm thick substrate. The bottom of the antenna is a 1-to-4 power divider feed network. Simulation results analysis are as follows. Figures 13 to 19 As shown, the presence of PCM indicates this application, while the absence of PCM indicates prior art.

[0081] First, the radiation characteristics of the two antennas are analyzed, and the reflection parameters are as follows: Figure 13 As shown in the figure, the antenna resonance characteristics remain essentially unchanged. It can be seen from the figure that the two antennas have similar S11 characteristics. The -10dB impedance bandwidth of the slot antenna array in this application is 9.06 to 10.72 GHz, while the -10dB impedance bandwidth of the reference antenna is 9.12 to 10.74 GHz. This means that the resonance point of this application shifts slightly to lower frequencies, and the bandwidth is broadened to a certain extent. Comparing the reflection coefficients of the two antennas, when the reference antenna is loaded with a polarization conversion surface, the antenna's S11 remains essentially unchanged; therefore, the antenna's impedance matching performance is good.

[0082] like Figure 14 As shown, the E-plane radiation patterns of two different antennas at 9.5 GHz demonstrate that at this frequency, RCS reduction is achieved with almost no impact on other performance characteristics. The gain of the reference antenna is 12.4 dB, while the gain of the antenna in this application is reduced by approximately 2.4 dB, down to about 10 dB. This gain is sufficient for normal operation of a slot antenna. Because the polarization conversion surface is covered, the excitation of electromagnetic waves from the slot is affected, resulting in good antenna performance.

[0083] like Figure 15As shown, the scattering characteristics of the two antennas are analyzed. When the plane wave is incident perpendicularly to the antenna plane in a y-polarized manner, compared with the reference antenna, the antenna of this application has a frequency band of 7.4-15.6GHz, the RCS is reduced by more than 5dB in a single station, and more than 10dB in a wider frequency band. The maximum RCS reduction is 20.3dB, and the antenna RCS is reduced both in-band and out-of-band.

[0084] like Figure 16 The image shows the actual antennas; both antennas are 60mm in size, further verifying their radiation and scattering performance.

[0085] like Figure 17 As shown, the far-field radiation patterns of the two antennas at 9.5 GHz were simulated and tested. At 9.5 GHz, the maximum radiation pattern of the antenna in this application is affected. The measured maximum radiation directional gain of the reference antenna is about 12.2 dBi, while the maximum radiation directional gain of the antenna after loading the polarization conversion surface is 9.8 dBi, which is basically consistent with the simulation results. For the electromagnetic stealth antenna of this application, there is a certain impact during the actual measurement. For the array antenna, it has basically no impact on the antenna's operating performance, which is consistent with the original intention of the designed antenna radiation and scattering characteristics. The simulation and test results have a high degree of agreement.

[0086] like Figure 18 As shown, the electromagnetic stealth performance of two types of antennas was tested and analyzed to verify the influence of the checkerboard polarization conversion surface on the antenna's electromagnetic stealth performance. The antenna was placed on a turntable, and y-polarized electromagnetic waves were incident perpendicularly to test the scattering performance of the designed antenna.

[0087] like Figure 19 As shown, a comparison of the monostatic RCS of two different antennas under y-polarization is presented. It is clear from the figures that, under perpendicular electromagnetic wave incidence, the antenna of this application achieves electromagnetic stealth performance. When the plane wave is incident in y-polarized form, the antenna of this application shows an RCS reduction of more than 5 dB compared to the reference antenna in the 7.4-15.6 GHz frequency band, demonstrating excellent electromagnetic stealth performance. In actual testing, the results show that the monostatic RCS value is even lower than the simulation results.

[0088] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0089] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A polarization conversion unit, characterized by, The application relates to a polarization conversion surface. The polarization conversion surface comprises a patch layer, a dielectric layer and a floor layer which are stacked from top to bottom. The patch layer comprises a first part and two second parts. The first part and the two second parts are rectangular structures, the two second parts are respectively located on opposite sides of the first part, and one side of each of the two second parts partially overlaps one side of the first part, so that the patch layer forms a center-symmetrical lightning-shaped structure, and the symmetry axis of the patch layer coincides with a diagonal line of the dielectric layer. The polarization conversion unit is used to be arranged and fixed on the dielectric substrate in a mirror-symmetrical manner to form the polarization conversion surface.

2. The polarization conversion unit of claim 1, wherein, The center of the patch layer is located directly above the center of the dielectric layer.

3. The polarization conversion unit of claim 2, wherein, The length of the first part is greater than the length of the second part, the width of the first part is twice the width of the second part, and the two top points on the same diagonal line are respectively located at the midpoint of the long side of one second part.

4. A polarization converting surface, characterized by The application relates to a polarization conversion surface. A plurality of polarization conversion units according to any one of claims 1 to 3 are divided into four groups with equal number and are respectively arranged in four quadrants. The polarization conversion units in each group are arranged in an array, and the four groups of polarization conversion units are arranged in a center-symmetrical manner.

5. The polarization converting surface of claim 4, wherein, The polarization conversion units in each group are arranged in a square array.

6. The polarization converting surface of claim 5, wherein, The patch layer of each polarization conversion unit points to the center of the polarization conversion surface.

7. Electromagnetic cloaked slot antenna, characterized in that The application relates to a polarization conversion surface. The polarization conversion surface is arranged above the slot antenna array. Each slot of the slot antenna array corresponds to a through hole on the polarization conversion surface, so that each slot is completely exposed.

8. The electromagnetic cloaked slot antenna according to claim 7, wherein, The slot antenna array comprises a radiation layer, a substrate layer and a feeding layer which are stacked from top to bottom.

9. The electromagnetic cloaked slot antenna according to claim 8, wherein, The slot is arranged on the radiation layer, and the polarization conversion surface abuts above the radiation layer. The feeding layer comprises three T-shaped power dividers.

10. The electromagnetic cloaked slot antenna according to claim 9, wherein, The first T-shaped power divider and the second T-shaped power divider are arranged in an axis-symmetrical manner about the third T-shaped power divider. The output end of the first T-shaped power divider extends to the input end to form an E-shaped structure. The input ends of the first T-shaped power divider and the second T-shaped power divider are used as the output ends of the third T-shaped power divider to form a one-to-four power division feeding network.

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