A Low RCS Antenna with Modified Radiation Patch

Abstract

The present invention relates to a low-RCS antenna with a modified radiation patch, belonging to the technical field of antennas, and is used to reduce the RCS of a radar in a communication device that requires stealth design, thereby improving the stealth ability of the target. The modified slot introduced by this method maintains the surface current distribution of the prototype reference antenna while reducing the metal area of the antenna, so that the RCS reduction of the antenna can be effectively achieved and the radiation characteristics of the antenna can be maintained, which helps to improve the stealth performance of electronic communication devices. The present invention solves the problem that the modified slot changes the radiation characteristics of the prototype reference antenna in the design of antenna RCS reduction based on the modification technology, and provides a new idea for the application of the modification technology in the design of antenna RCS reduction.

Description

Technical Field

[0001] The present invention relates to the technical field of antennas, and particularly to a low RCS antenna based on antenna radiation patch modification technology. Background Art

[0002] As a device for transmitting and receiving electromagnetic waves in a wireless system, an antenna is an essential component of the wireless system. In civilian systems, only the radiation performance of the antenna is generally concerned, while in military systems, in addition to the radiation performance of the antenna, the antenna is also required to have low scattering characteristics. When the electromagnetic wave emitted by a detection radar irradiates a military equipment, the antenna in the wireless device acts as a scattering source and will generate strong scattering, which is not conducive to the stealth of military wireless devices. For military wireless devices that require strong stealth characteristics, the scattering generated by the antenna elements in the wireless device will greatly affect the stealth performance of the device. Therefore, how to reduce the scattering of the antenna is one of the key factors restricting the further improvement of the platform stealth performance.

[0003] The scattering characteristics of an antenna are characterized by the Radar Cross Section (RCS). Therefore, the research on antennas with low scattering characteristics is also the research on antenna RCS reduction technology, which is of great significance for ensuring the stealth performance of the entire platform. In addition, in order to ensure the normal operation of the antenna in the wireless system, when studying the reduction of the antenna RCS, the radiation performance of the antenna should be maintained as much as possible, and the antenna should not be unable to work properly in order to reduce the antenna RCS. Therefore, when designing a low RCS antenna, both the radiation problem of the antenna and how to reduce the antenna scattering should be considered, which determines the complexity and importance of the antenna RCS reduction technology. Therefore, how to reduce the scattering of the antenna is one of the research hotspots in current antenna technology.

[0004] Currently, the research on antenna RCS reduction technology mainly focuses on the antenna RCS reduction technology based on metamaterials and the RCS reduction technology based on the modification of the antenna electric field distribution. The research group of Professor Cao Xiangyu from Air Force Engineering University designed a low RCS microstrip antenna with a butterfly structure according to the biological principle of butterflies. The black scales distributed on the wings can effectively reflect or absorb some light, enabling the butterfly to achieve visual stealth to a certain extent. The antenna radiation patch was grooved and modified with reference to the color distribution on the butterfly wings. As Figure 1 and Figure 2 shown. The simulation results and the measured results show that although the designed biomimetic microstrip antenna can effectively reduce the out-of-band RCS of the antenna under oblique incidence, the operating frequency of the modified microstrip antenna is significantly lower than that of the prototype antenna, changing the original radiation characteristics of the antenna and not meeting the requirements of modern antenna RCS technology for maintaining radiation characteristics.

[0005] Another current technical idea for reducing the RCS of an antenna using a shaping technique is to remove the metal areas with relatively weak electric field distribution from the prototype antenna. For example, the low-RCS ultra-wideband antenna designed by Cengizhan Figure 3 shows an unshaped double-axe antenna. The black part is the metal part of the antenna radiation surface and the microstrip feeder, the gray part is the metal plate of the antenna ground metal surface, and the light-colored part is the dielectric substrate without metal attachment. Figure 4 shows the double-axe antenna after slotting. It can be seen that there are modifications on both the radiation surface and the metal ground plane of the reference antenna. Simulation and measurement results show that although the improved antenna can achieve a 10 dB reduction in antenna RCS within the operating frequency range, the resonant frequency of the antenna also changes significantly.

[0006] The application of metamaterials in the field of antenna technology has been a popular research direction in antenna technology in recent years. Loading metamaterials around antenna elements or antenna arrays can also effectively reduce the antenna RCS through appropriate arrangement and unit design. For example, Figure 5 and Figure 6 show that domestic and foreign scholars have achieved antenna RCS reduction by loading metamaterial array structures. Although the antenna RCS reduction technology based on metamaterials can simultaneously reduce the antenna RCS and maintain the antenna radiation characteristics. However, from the antenna structure diagrams shown in the figures, it can be clearly seen that with the use of the metamaterial array structure, the original size of the antenna is deliberately extended, increasing the original size of the antenna, which does not conform to the application scenarios in actual antenna engineering.

[0007] To more intuitively reflect the advantages and disadvantages of each antenna RCS reduction technology, based on the above review of each technical method, the common antenna RCS reduction technologies and their advantages and disadvantages are summarized in Table 1.

[0008] Table 1 Comparison of Antenna RCS Reduction Technologies

[0009]

[0010] Through the summary of the research results of each method, it can be seen that the RCS reduction technology of antennas based on metamaterials is a current research hotspot, and frequency selective surfaces, artificial magnetic conductors, metasurfaces, and absorbers are relatively common types of metamaterials. There are mainly two ways to load metamaterials on antennas. One is to load the cladding composed of a metamaterial array above or below the antenna to form an antenna-metamaterial cladding system. Although this combination can effectively reduce the in-band and out-of-band RCS of the antenna and maintain the original radiation characteristics of the antenna, this loading method greatly increases the volume of the antenna, which does not meet the current development requirements of antenna miniaturization and conformal shaping. The other loading method is to load multiple metamaterial units on the surface of the antenna dielectric substrate or replace the metal ground plane, so that the metamaterial units are coplanar with the antenna radiation patch or the metal bottom plate. Although this combination can also effectively reduce the antenna RCS and maintain the antenna radiation characteristics, the position loaded by this metamaterial loading technology is usually located in the extended plane of the reference antenna dielectric substrate, and the increased antenna size for extending the dielectric substrate is not conducive to the requirements of antenna miniaturization. Therefore, although metamaterial technology can effectively reduce the antenna RCS, the increased antenna size and volume are not suitable for the development trend of antenna miniaturization. Therefore, how to use metamaterials to reduce the antenna RCS and maintain the antenna radiation characteristics without changing the original volume size of the antenna is the future development trend of the metamaterial technology for reducing the antenna RCS.

[0011] Therefore, all the current common antenna RCS reduction technologies are achieved at the cost of sacrificing the antenna radiation performance or the antenna profile and antenna size, and it is difficult to achieve antenna RCS reduction and maintain the antenna radiation characteristics while maintaining the antenna size and profile. Based on the above summarized current technical status, the present invention intends to propose a technical solution for how to achieve antenna RCS reduction and maintain the antenna radiation characteristics while maintaining the antenna size and profile. Summary of the Invention

[0012] Technical Problems to be Solved

[0013] In order to avoid the deficiencies of the prior art, the present invention provides a low RCS antenna with a modified radiation patch. It is to meet the requirement of reducing the antenna RCS without changing the antenna size, profile, and radiation characteristics. The content of this invention has the advantages of simple structure, easy processing, and easy integration, and can effectively improve the stealth performance of communication devices. The invention purpose of the present invention can be clearly defined as the following points:

[0014] 1. Achieve antenna RCS reduction without changing the antenna shape and size structure;

[0015] 2. Achieve antenna RCS reduction without changing the antenna operating frequency band and radiation gain;

[0016] 3. In the C-band, the RCS is reduced both within and outside the antenna operating band;

[0017] Technical Solution

[0018] A low RCS antenna with a modified radiation patch, characterized in that it includes nine empty slots located in the radiation patch, an antenna radiation patch, an antenna dielectric substrate, an antenna metal bottom plate and an antenna feeding probe, the nine empty slots are marked as a first empty slot, a second empty slot, a third empty slot, a fourth empty slot, a fifth empty slot, a sixth empty slot, a seventh empty slot, an eighth empty slot and a ninth empty slot in sequence; the nine rectangular empty slots are all located in the antenna metal radiation patch; the antenna's metal radiation patch is arranged on the antenna's dielectric substrate, and the antenna's dielectric substrate is arranged on the antenna's metal bottom plate; the coaxial probe is located in the antenna's dielectric substrate.

[0019] A further technical solution of the present invention is as follows: the angle between the extension lines of the first empty slot, the second empty slot, the third empty slot, the fourth empty slot, the fifth empty slot, the sixth empty slot, the seventh empty slot and the eighth empty slot and the antenna radiation patch is 45°, and the fourth empty slot located near the diagonal line of the radiation patch (1) is the longest.

[0020] A further technical solution of the present invention is as follows: the fifth empty slot and the sixth empty slot are located on both sides of the coaxial probe.

[0021] A further technical solution of the present invention: the ninth slot is a vertical slot, which is parallel to the edge of the antenna radiation patch.

[0022] Beneficial Effects

[0023] The present invention provides a low RCS antenna with a modified radiation patch. By analyzing the distribution characteristics of the current flow direction on the antenna surface, slots are made along the current flow direction on the antenna surface to minimize the impact of the slots on the surface current flow path. Nine narrow rectangular slots are made on the antenna radiation patch along the surface current direction to reduce the metal area of ​​the radiation patch, thereby achieving simultaneous reduction of the antenna in-band RCS and out-of-band RCS while maintaining the antenna's radiation characteristics unchanged. The antenna has a simple structure, a low profile, and adopts printed circuit board processing technology. It has the characteristics of low cost and easy integration, and has a wide range of application value in future low RCS antenna technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0025] Figure 1 Butterfly patterns referenced in the literature;

[0026] Figure 2Butterfly-based bionic antennas in the literature;

[0027] Figure 3 Unmodified double-axe antennas in the literature;

[0028] Figure 4 Double-axe antennas with slots in the literature;

[0029] Figure 5 Low RCS antenna array model based on metamaterials;

[0030] Figure 6 Antenna based on artificial magnetic conductor chessboard structure;

[0031] Figure 7 Schematic diagram of the low RCS antenna structure of the present invention example;

[0032] Figure 8 Schematic diagram of the product structure of the low RCS antenna of the present invention example;

[0033] Figure 9 Surface current distribution of the prototype reference antenna;

[0034] Figure 10 Surface current distribution of the improved antenna after introducing empty slots;

[0035] Figure 11 Comparison of measured frequency characteristics of the prototype reference antenna and the improved antenna product samples;

[0036] Figure 12 Comparison of measured radiation characteristics of the prototype reference antenna and the improved antenna product samples;

[0037] Figure 13 Comparison of measured RCS characteristics of the prototype reference antenna and the improved antenna product samples. Detailed implementation manners

[0038] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0039] The physical basis of the present invention is as follows: Based on the analysis of the surface radiation current distribution of the prototype antenna, since it is necessary to maintain the antenna radiation characteristics as a prerequisite for the antenna RCS reduction design, the introduced modified slots should not have an obvious impact on the antenna radiation current distribution. Therefore, the direction of the introduced slots should be parallel to the direction of the antenna surface current propagation, rather than the region where the conventional electric field distribution is weak. In addition, in order to avoid the influence of the edge current effect generated by the introduction of the slots on the antenna radiation characteristics, the size of the slots should not be too large, and the slot spacing should not be too close. Since the introduced slots reduce the area of the metal part of the antenna, the scattering of the antenna to the incident electromagnetic wave is reduced, the antenna RCS reduction is achieved, and at the same time, the original radiation characteristics of the antenna are maintained.

[0040] The low-RCS antenna proposed by the present invention includes: nine rectangular slots located in the radiation patch, an antenna structure and a feeding structure. The rectangular slots include eight oblique slots and one vertical slot. The antenna structure includes the metal radiation patch of the antenna, the metal bottom plate of the antenna, and the dielectric substrate of the antenna. The antenna feeding structure includes a coaxial probe and a feeding port; the metal radiation patch of the antenna is arranged on the dielectric substrate of the antenna, and the dielectric substrate of the antenna is arranged on the metal bottom plate of the antenna; the coaxial probe is located inside the antenna dielectric substrate, and the feeding port is arranged inside the antenna metal bottom plate.

[0041] Different from the conventional antenna modification idea that only targets the surface electric field amplitude distribution at present, the present invention proposes an antenna modification method of introducing multiple narrow slots along the direction of the surface current flow to maintain the antenna radiation characteristics and reduce the metal area on the antenna surface. The influence of parameters such as the slot size and distribution position on the surface current flow path of the antenna is analyzed.

[0042] For the low-RCS antenna proposed by the present invention, the extension lines of the eight oblique slots form an angle of 45° with the antenna radiation patch, and the slot near the diagonal of the radiation patch is the longest.

[0043] For the low-RCS antenna proposed by the present invention, the vertical slot is parallel to the edge of the antenna radiation patch.

[0044] The technical idea for implementing the present invention is as follows: Model the prototype antenna in a high-frequency electromagnetic simulation software, and then analyze the surface current distribution of the prototype reference antenna. Slots are cut along the direction of the surface current propagation of the reference antenna, and efforts are made to ensure that the direction of the cut slot is parallel to the current direction at the slot position. At the same time, in order to ensure the normal operation of the antenna, it is necessary to retain the edge shape of the radiation patch of the prototype reference antenna. Optimize the size of the empty slot, and make the size of the empty slot as large as possible on the premise of ensuring the radiation characteristics of the antenna. Then analyze the RCS characteristics of the antenna after slotting, compare it with the RCS of the prototype reference antenna, and obtain the specific RCS reduction effect of the antenna. Finally, process the samples of the reference antenna and the improved antenna, test them, and verify the correctness of the theoretical analysis through the measured results.

[0045] The object of the present invention is achieved through the following specific steps:

[0046] 1) Model the prototype antenna and analyze its surface current distribution:

[0047] In a high-frequency electromagnetic simulation software, perform simulation design on the prototype reference antenna, establish the antenna model, set the corresponding radiation boundary conditions and excitations, and obtain the radiation characteristics of the prototype reference antenna at the resonant frequency. Analyze the surface current distribution of the radiation patch of the antenna at the resonant frequency to obtain the current propagation direction and current amplitude distribution at each position on the metal surface.

[0048] 2) Introduce an empty slot in the antenna radiation patch and optimize the analysis

[0049] Based on the current propagation direction on the surface of the antenna radiation patch obtained in the previous step, modify the shape of the antenna radiation patch in the simulation model. Introduce a rectangular empty slot parallel to the current propagation direction on the radiation patch. Set the length and width of the introduced empty slot as variable parameters respectively, and optimize the influence of the two on the radiation characteristics of the antenna to obtain the modified slotting size that can maintain the radiation characteristics of the antenna. In addition, optimize the position distribution of the empty slot on the surface of the antenna radiation patch and study the influence of the empty slot position distribution on the radiation characteristics of the antenna.

[0050] 3) Confirm whether the radiation characteristics of the improved antenna have changed compared with the reference antenna

[0051] Based on the modified improved antenna obtained in the previous step, compare its frequency characteristics and radiation characteristics with the performance of the reference antenna to confirm whether the modified structure in the previous step has an impact on the original radiation characteristics of the antenna. After ensuring that there is basically no impact on the radiation characteristics of the antenna, proceed to the next step.

[0052] 4) Introduce eight parallel oblique empty slots and one vertical empty slot in the antenna radiation patch successively

[0053] Based on the optimization analysis of the modified empty slot in the previous step, find the empty slot size and spatial distribution that make the radiation characteristics of the improved antenna similar to those of the reference antenna. On the premise of "maintaining the antenna radiation characteristics", minimize the metal area of the antenna radiation patch as much as possible in terms of the empty slot size and spatial distribution. After introducing the first parallel oblique empty slot, in the unslotted area of the metal plate of the antenna radiation patch, introduce the second oblique empty slot. The width of this empty slot is the same as that of the first empty slot, and the second empty slot is parallel to the first empty slot. Optimize the length and position of the second empty slot so that the combination of the current two parallel empty slots has basically no impact on the radiation characteristics of the improved antenna. In this way, a total of eight parallel oblique empty slots are introduced in sequence. After determining the size and spatial distribution of the existing eight parallel oblique empty slots, introduce a vertical empty slot at the remaining position of the antenna radiation patch, and optimize the size parameters and position distribution of this vertical empty slot so that the combination of the nine empty slots has basically no obvious impact on the radiation characteristics of the improved antenna. Thus, by introducing eight parallel oblique empty slots and one vertical empty slot, the metal area of the antenna radiation patch is reduced, and at the same time, the original radiation characteristics of the antenna are basically maintained.

[0054] 5) Compare the RCS characteristics of the improved antenna and the reference antenna

[0055] After confirming that the radiation characteristics of the modified antenna are similar to those of the prototype reference antenna, analyze the scattering patterns of the modified antenna and the reference antenna to obtain the RCS characteristic curves of the two antennas under the same incident conditions. Compare the RCS characteristics of the two antennas to clarify the specific performance parameters of the RCS of the improved antenna compared to the RCS of the reference antenna, and obtain the impact of the introduced empty slot on the performance of the antenna RCS.

[0056] 6) Process antenna samples for testing

[0057] Process samples of the designed reference antenna and modified antenna, and test the radiation characteristics and RCS characteristics of the product samples in an anechoic chamber. Compare the radiation performance test results of the improved sample with those of the reference antenna to confirm whether there is an obvious change in the antenna radiation performance. Then compare the measured RCS results of the improved sample with the measured RCS results of the reference antenna sample to clarify the specific effect of the modification technology on the improvement of the RCS performance. Verify the correctness of the theoretical design through the testing of the product samples.

[0058] Next, in combination with the drawings in the present invention, in order to better understand and use the low-RCS antenna provided by the present invention, a low-RCS antenna design method based on radiation patch modification proposed by the present invention is described in detail through examples.

[0059] In an example of the low-RCS antenna provided by the present invention, the antenna operates in the C band and has low-RCS characteristics throughout the entire C-band frequency range.

[0060] According to the above design implementation process, the final results of the embodiments of the present invention are as follows: As Figure 7 shown, the antenna radiation patch is a square with a size of 21.6 mm. The antenna dielectric substrate is made of a material with a relative dielectric constant of 2.2, and the length and width of the substrate are both 27.5 mm, and the thickness is 2 mm. The horizontal distance from the feeding point to the center point of the antenna is 2.2 mm, and the vertical distance from the feeding point to the center point of the antenna is 2.2 mm. The lengths of the eight parallel oblique slots are 3 mm, 9.8 mm, 8 mm, 21 mm, 4.6 mm, 3 mm, 10 mm, and 7 mm respectively, and the widths are all 2 mm. The vertical slot has a length of 6 mm and a width of 3 mm.

[0061] Furthermore, as Figure 6 and Figure 10 shown, the radiation current direction of the improved antenna with nine slots introduced is basically the same as that of the reference antenna, and the current amplitude values are also basically the same.

[0062] As Figure 11 shown, the operating frequency of this low RCS antenna is 4.2 - 4.38 GHz, and the operating frequency of the reference antenna is 4.21 - 4.3 GHz. The nine slots introduced do not change the original operating frequency bandwidth of the antenna.

[0063] As Figure 12 shown, the E-plane and H-plane radiation patterns of this low RCS antenna are basically the same as those of the reference antenna Figure One consistent.

[0064] As Figure 13 shown, the RCS reduction effect of this low RCS antenna is obvious. Compared with the reference antenna, the maximum RCS reduction amounts in the band and out of the band are 4.3 dB and 4 dB respectively.

[0065] In summary, for the low RCS antenna provided by the present invention, by analyzing the distribution characteristics of the surface current flow direction of the antenna, slots are opened along the surface current flow direction of the antenna to minimize the influence of the slots on the surface current flow path. Nine long and narrow rectangular slots are opened along the surface current direction on the antenna radiation patch, reducing the metal area of the radiation patch. Thus, while maintaining the radiation characteristics of the antenna unchanged, the reduction of both in-band RCS and out-of-band RCS of the antenna is achieved.

[0066] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A low RCS antenna with a modified radiation patch, characterized in that: It includes nine empty slots located in the radiation patch, an antenna radiation patch (1), an antenna dielectric substrate (2), an antenna metal bottom plate, and an antenna feeding probe (3). The nine rectangular empty slots are sequentially labeled as the first empty slot (4), the second empty slot (5), the third empty slot (6), the fourth empty slot (7), the fifth empty slot (8), the sixth empty slot (9), the seventh empty slot (10), the eighth empty slot (11), and the ninth empty slot (12). All of the nine rectangular empty slots are located within the antenna radiation patch (1). The antenna radiation patch (1) is disposed on the dielectric substrate (2) of the antenna, and the dielectric substrate (2) of the antenna is disposed on the metal bottom plate of the antenna. The antenna feeding probe (3) is located within the antenna dielectric substrate (2). The extension lines of the first empty slot (4), the second empty slot (5), the third empty slot (6), the fourth empty slot (7), the fifth empty slot (8), the sixth empty slot (9), the seventh empty slot (10), and the eighth empty slot (11) form an angle of 45° with the antenna radiation patch (1), and the fourth empty slot (7) near the diagonal of the antenna radiation patch (1) is the longest. The ninth empty slot (12) is a vertically oriented empty slot and is parallel to the edge of the antenna radiation patch (1).

2. The low RCS antenna with a modified radiation patch according to claim 1, characterized in that: The fifth empty slot (8) and the sixth empty slot (9) are located on both sides of the antenna feeding probe (3).

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