A broadband low-radar cross-section antenna loaded with ATFSS

Abstract

The application discloses a broadband low radar scattering cross section antenna loaded with an ATFSS, which comprises three layers of dielectric plates, namely, an upper layer plate, a middle layer plate and a lower layer plate, the upper surface and the lower surface of the upper layer plate are attached with wave absorbing structures, the lower surface of the middle layer plate is attached with a band-pass FSS structure, the upper surface of the lower layer plate is attached with a patch antenna, the lower surface of the lower layer plate is a metal ground plate, coaxial line feeding is adopted, and the upper layer plate, the middle layer plate and the lower layer plate are all air cavities. The broadband low radar scattering cross section antenna adopts the wave absorbing structure with a multi-resonance structure and the band-pass FSS structure, can realize the integrated characteristics of wave absorption and wave transmission, and the wave absorbing structure and the band-pass FSS can be loaded as a coating above the microstrip patch antenna to realize the RCS reduction in a wide frequency band under the condition of ensuring the normal radiation of the antenna.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of antennas, in particular to a wideband low radar cross section antenna loaded with ATFSS. BACKGROUND

[0002] Radar cross section (RCS) is a key performance indicator of radar stealth and radar counter-stealth, which is very important for military applications. Low radar cross section antenna is an ideal choice for high-stealth military systems. For this antenna, its scattering field contains structure mode and antenna mode. In the prior art, the structure mode can be reduced by using electromagnetic band gap (EBG) structure or artificial magnetic conductor (AMC), but it is very difficult to achieve wideband radar cross section reduction based on EBG or AMC.

[0003] Absorptive / transmissive frequency selective structure (ATFSS) has a wide absorption band to realize wave transmission within the antenna operating frequency band and electromagnetic wave absorption outside the frequency band, which can reduce the multi-station radar cross section of the antenna without interfering with the antenna radiation performance. The low radar cross section antenna can also be realized by directly placing ATFSS above the antenna, and ATFSS and antenna can be combined into an integrated radome antenna system. The out-of-band electromagnetic wave is absorbed by the resistive element, thereby realizing a wideband low radar cross section frequency band.

[0004] With the special needs of antenna system stealth in radar stealth technology, when the enemy and our radar work at different frequency bands, the combination of ATFSS structure and antenna into an antenna system to realize the reduction of radar cross section in a wide frequency band and maintain good radiation performance provides further requirements. SUMMARY

[0005] The purpose of the present application is to overcome the technical defects of the prior art and provide a wideband low radar cross section antenna loaded with ATFSS. The absorptive unit structure with multi-resonant structure is combined with the bandpass FSS structure to realize the characteristics of wave absorption and transmission integration. The absorptive unit structure and the bandpass FSS composed of the absorptive frequency selective structure can be loaded as a coating above the microstrip patch antenna to realize the reduction of wideband out-of-band RCS under the condition of ensuring the normal radiation of the antenna.

[0006] The purpose of the present application is achieved by the following technical solutions:

[0007] In a first aspect, the application provides a broadband low radar cross section antenna, comprising: an upper layer plate, a middle layer plate and a lower layer plate, the upper surface and the lower surface of the upper layer plate are attached with wave-absorbing structures, the lower surface of the middle layer plate is attached with a band-pass FSS structure, the upper surface of the lower layer plate is attached with a patch antenna, and the lower surface of the lower layer plate is a metal ground plate, the antenna is fed by a coaxial line, and the upper layer plate, the middle layer plate and the lower layer plate are air cavities.

[0008] In an optional embodiment, the wave-absorbing structure comprises a plurality of uniformly distributed and identically sized wave-absorbing units, each of the wave-absorbing units comprises a left half and a right half of a butterfly-shaped dipole which are left-right symmetrical, and the left half and the right half of the butterfly-shaped dipole are connected with a U-shaped microstrip line and a PCB printed conductor via a lumped resistor.

[0009] In an optional embodiment, the band-pass FSS structure comprises a plurality of identically sized band-pass FSS units, each of the band-pass FSS units comprises a cross-shaped patch which is placed in a cross-shaped slot.

[0010] In an optional embodiment, the wave-absorbing units are horizontally distributed on the wave-absorbing structure of the upper surface of the upper layer plate, and the wave-absorbing units are vertically distributed on the wave-absorbing structure of the lower surface of the upper layer plate.

[0011] In an optional embodiment, the height between the upper surface of the lower layer plate and the lower surface of the middle layer plate is greater than the height between the lower surface of the upper layer plate and the lower surface of the middle layer plate.

[0012] In an optional embodiment, the height between the upper surface of the lower layer plate and the lower surface of the middle layer plate is 23 mm.

[0013] In an optional embodiment, the height between the lower surface of the upper layer plate and the lower surface of the middle layer plate is 8 mm.

[0014] In an optional embodiment, the resistance of the lumped resistor is 90 ohms.

[0015] In an optional embodiment, the U-shaped microstrip line is a rectangular strip with a length of 5 mm and a width of 0.5 mm.

[0016] In an optional embodiment, the butterfly-shaped dipole is obtained by cutting two triangular patches from a rectangular patch.

[0017] The above main scheme of the application and each further selected scheme can be freely combined to form multiple schemes, which are all the schemes that can be adopted and claimed by the application; and the application can also be freely combined between each non-conflict selection and between other selections. Those skilled in the art can understand that there are many combinations according to the prior art and common knowledge after understanding the schemes of the application, which are all the technical schemes claimed by the application, and are not listed here.

[0018] The application discloses a broadband low radar cross section antenna loaded with ATFSS, which comprises three layers of dielectric plates: an upper layer plate, a middle layer plate and a lower layer plate, the upper surface and the lower surface of the upper layer plate are attached with wave-absorbing structures, the lower surface of the middle layer plate is attached with a band-pass FSS structure, the upper surface of the lower layer plate is attached with a patch antenna, the lower surface of the lower layer plate is a metal ground plate, a coaxial line is used for feeding, and the upper layer plate, the middle layer plate and the lower layer plate are all air cavities. The broadband low radar cross section antenna combines the wave-absorbing unit structure with a multi-resonant structure and the band-pass FSS structure, can realize the characteristics of wave-absorbing and wave-transmitting integration, and the wave-absorbing frequency selective structure composed of the wave-absorbing unit structure and the band-pass FSS can be loaded above the microstrip patch antenna as a coating, so that the RCS reduction in a wide frequency band outside the antenna can be realized under the condition of ensuring normal radiation of the antenna. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A structure schematic diagram of a broadband low radar cross section antenna provided by an embodiment of the application is shown.

[0020] Figure 2 A structure schematic diagram of a wave-absorbing unit provided by an embodiment of the application is shown.

[0021] Figure 3 A structure schematic diagram of a band-pass FSS unit provided by an embodiment of the application is shown.

[0022] Figure 4 A schematic diagram of a wave-absorbing frequency selective structure provided by an embodiment of the application is shown.

[0023] Figure 5 A structure schematic diagram of a lower layer plate provided by an embodiment of the application is shown.

[0024] Figure 6 Simulation results of the reflection coefficients of the broadband low radar cross section antenna and a reference antenna in a radiation state.

[0025] Figure 7a Simulation results of the radiation patterns of the inventive antenna and the reference antenna.

[0026] Figure 7b Another simulation results of the radiation patterns of the inventive antenna and the reference antenna.

[0027] Figure 8a Simulation results of monostatic radar cross section of the invented antenna and reference antenna under x polarization of the embodiments of the present application.

[0028] Figure 8b Simulation results of monostatic radar cross section of the invented antenna and reference antenna under y polarization of the embodiments of the present application.

[0029] Legend: 1 - upper layer board; 2 - middle layer board, 3 - lower layer board; 4 - wave absorbing structure; 5 - band-pass FSS structure; 6 - patch antenna; 7 - metal ground plate. DETAILED DESCRIPTION

[0030] The above embodiments of the present application are described with reference to specific examples. Other advantages and effects of the present application can be easily understood by those skilled in the art from the above description. The present application can be implemented or applied in other different embodiments, and the details in the description can be modified or changed based on different views and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0031] All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative labor are within the scope of protection of the present application.

[0032] In the prior art, the scattering field of a low radar cross section antenna contains structure mode and antenna mode. The structure mode is reduced by using electromagnetic band gap structure or artificial magnetic conductor, but it is difficult to achieve wideband radar cross section reduction based on EBG or AMC antenna. With the special requirements of antenna system stealth in radar stealth technology, when the enemy and our radar work at different frequency bands, the combination of loading ATFSS structure and antenna into the antenna system provides further requirements for realizing radar cross section reduction in wide frequency band and maintaining good radiation performance.

[0033] To solve the above problems, the embodiments of the present application provide a wideband low radar cross section antenna, please refer to Figure 1 , Figure 1 The structure schematic diagram of a wideband low radar cross section antenna provided by the embodiments of the present application is shown, as shown in the figure, the wideband low radar cross section antenna includes three layers of dielectric boards: upper layer board 1, middle layer board 2 and lower layer board 3. The upper surface and the lower surface of the upper layer board 1 are attached with wave absorbing structure 4, the lower surface of the middle layer board 2 is attached with band-pass FSS structure 5, the upper surface of the lower layer board 3 is attached with patch antenna 6, the lower surface of the lower layer board 3 is metal ground plate 7, and the coaxial line is used for feeding, the upper layer board 1, the middle layer board 2 and the lower layer board 3 are air cavities.

[0034] The height between the upper surface of the lower layer plate 3 and the lower surface of the middle layer plate 2 is greater than the height between the lower surface of the upper layer plate 1 and the lower surface of the middle layer plate 2.

[0035] The height between the upper surface of the lower layer plate 3 and the lower surface of the middle layer plate 2 is h2, which is 23mm.

[0036] The height between the lower surface of the upper layer plate 1 and the lower surface of the middle layer plate 2 is h1, which is 8mm.

[0037] The wave-absorbing structure 4 includes a plurality of uniformly distributed and equal-sized wave-absorbing units, each of which includes a left half and a right half of a butterfly-shaped dipole that are left-right symmetrical, and the left half and the right half of the butterfly-shaped dipole are connected with a U-shaped microstrip line through lumped resistors and PCB printed conductors. The U-shaped microstrip line is placed at the center of the butterfly-shaped dipole, and two lumped resistors and two PCB printed conductors are used for connection. The butterfly-shaped dipole provided in the embodiment of the present application is slightly different from the existing butterfly-shaped dipole, which is obtained by cutting off two triangular patches on the inner side of the existing butterfly-shaped dipole. The wave-absorbing structure 4 in the embodiment of the present application adopts a multi-resonant structure, which combines a plurality of effective frequency bands to expand the wave-absorbing bandwidth of the unit structure.

[0038] Please refer to Figure 2 , Figure 2 The structure of the wave-absorbing unit provided in the embodiment of the present application is shown in the structural schematic diagram. The wave-absorbing unit includes a left half and a right half of a butterfly-shaped dipole that are left-right symmetrical, lumped resistors, PCB printed conductors and a U-shaped microstrip line, and the connection sequence is the left half of the butterfly-shaped dipole, the lumped resistor, the PCB printed conductor, the U-shaped microstrip line, the PCB printed conductor, the lumped resistor, and the right half of the butterfly-shaped dipole.

[0039] The U-shaped microstrip line is a rectangular strip with a length L1 of 5mm and a width W1 of 0.5mm. The length of the bottom of the U-shaped microstrip line can be set according to actual conditions. The two ends of the U-shaped microstrip line are respectively connected with two PCB printed conductors, and the two ends of the two PCB printed conductors are connected with two lumped resistors. Each lumped resistor uses a resistor with a resistance of 90 ohms. Each lumped resistor is at a distance d1 of 2.5mm from the center of the wave-absorbing unit. The butterfly-shaped dipole is a rectangular patch with a length L2 of 21mm and a width W2 of 5mm, and two triangular patches with a length L3 of 9.85mm and a width W3 of 2mm.

[0040] The band-pass FSS structure 5 includes a plurality of equal-sized band-pass FSS units, such as N×N band-pass FSS units. Each band-pass FSS unit contains a cross patch, which is placed in a cross slot.

[0041] Please refer to Figure 3 , Figure 3The structure diagram of the band-pass FSS unit is shown. A cross-shaped slot is opened on the metal floor of the lower surface of the middle layer dielectric plate. The length L of the cross-shaped slot is 7.6 mm, and the width W is 1.2 mm. The cross-shaped patch is placed in the cross-shaped slot. The length L4 of the cross-shaped patch is 7.2 mm, and the width W4 is 0.8 mm. It is indicated that the length and width of the cross-shaped slot and the cross-shaped patch are not limited in the embodiment of the application. s The length L of the cross-shaped slot is 7.6 mm, and the width W s is 1.2 mm. The cross-shaped patch is placed in the cross-shaped slot. The length L4 of the cross-shaped patch is 7.2 mm, and the width W4 is 0.8 mm. It is indicated that the length and width of the cross-shaped slot and the cross-shaped patch are not limited in the embodiment of the application.

[0042] The upper surface of the lower layer plate 3 is attached with the patch antenna 6. The lower surface of the lower layer plate 3 is a metal floor 7. The coaxial line is used for feeding. The coaxial line is arranged below the microstrip patch antenna 6. The effective radiation of the antenna and the reduction of the wideband out-of-band radar scattering cross section can be realized.

[0043] In addition, please refer to Figure 4 , Figure 4 The structure diagram of the absorption frequency selective structure is shown. The absorption frequency selective structure (ATFSS) is composed of 3*3 band-pass FSS structures 5 of the lower surface of the middle layer plate 2, the wave-absorbing structure 4 of the upper surface of the upper layer plate 1, and the wave-absorbing structure 4 of the lower surface. Each band-pass FSS structure 5 contains 3*3 band-pass FSS units. Each wave-absorbing structure 4 contains 4*4 absorption units.

[0044] Next, the microstrip patch antenna 6 is described. Please refer to Figure 5 , Figure 5 The structure diagram of the lower layer plate 3 is shown. The center of the lower layer plate 3 is the patch antenna 6. The length L5 of the patch antenna 6 is 13 mm, and the width W5 is 10.2 mm.

[0045] The wideband low radar scattering cross section antenna of the embodiment of the application is tested. The flat plate slot antenna structure without any super surface layer is taken as a reference antenna. Please refer to Figure 6 , Figure 6 The simulation results of the reflection coefficients of the wideband low radar scattering cross section antenna and the reference antenna in the radiation state are shown. The invention antenna is the wideband low radar scattering cross section antenna. When the impedance bandwidth is-10 dB, the frequency is 8.49-9.35 GHz. At this time, the relative bandwidth of the wideband low radar scattering cross section antenna is 9.6%. This is basically consistent with the frequency (8.47-9.28 GHz) and the relative bandwidth (9.1%) of the reference antenna.

[0046] In addition, when the frequency is 11.3 GHz, Figure 7a and Figure 7bThe simulation results of the radiation patterns of the antenna and the reference antenna are shown in the figure, and the radiation performance of the antenna is good because the gain of the antenna is increased by about 2.5 dB than that of the reference antenna.

[0047] If the incident wave is irradiated under two polarizations, Figure 8a The simulation results of the monostatic radar cross sections of the antenna and the reference antenna under the x polarization of the embodiment of the application. Figure 8b The simulation results of the monostatic radar cross sections of the antenna and the reference antenna under the y polarization of the embodiment of the application. Compared with the reference antenna, the antenna can realize the antenna out-of-band monostatic RCS reduction in the range of 2.8 GHz to 8.9 GHz. If the frequency point is 6.5 GHz under different polarization modes, the maximum reduction of the monostatic RCS is 23 dB.

[0048] Compared with the prior art, the embodiment of the application has the following beneficial effects:

[0049] 1. By loading the wave-absorbing structure on the upper and lower surfaces of the upper layer dielectric plate, the out-of-band wave-absorbing characteristics of the wideband low radar cross section antenna can be realized, and the out-of-band RCS reduction function is ensured.

[0050] 2. The band-pass FSS structure can realize in-band wave transmission, and ensures that the antenna can normally work in the working frequency band.

[0051] 3. The wave-absorbing structure and the band-pass FSS structure form an ATFSS structure, which can ensure that the wideband low radar cross section antenna can realize the conversion of incident electromagnetic wave energy into heat energy under the condition of good radiation characteristics, so as to reduce the wideband out-of-band antenna RCS reduction.

[0052] The above only describes the preferred embodiments of the application and is not used to limit the application, and any modification, equivalent replacement and improvement made within the spirit and principle of the application should be included in the protection scope of the application.

Claims

1. A broadband low radar cross section antenna loaded with ATFSS, characterized in that, The antenna comprises an upper layer plate, a middle layer plate and a lower layer plate, the upper surface and the lower surface of the upper layer plate are attached with wave-absorbing structures, the wave-absorbing structures comprise a plurality of uniformly distributed and equal-sized wave-absorbing units, the wave-absorbing units comprise a butterfly-shaped dipole, the butterfly-shaped dipole is left-right symmetrical, the left half and the right half of the butterfly-shaped dipole are connected with a U-shaped microstrip line through a lumped resistor and a PCB printed conductor, the wave-absorbing units are horizontally distributed on the wave-absorbing structure of the upper surface of the upper layer plate, the wave-absorbing units are vertically distributed on the wave-absorbing structure of the lower surface of the upper layer plate, the lower surface of the middle layer plate is attached with a band-pass FSS structure, the band-pass FSS structure comprises a plurality of equal-sized band-pass FSS units, the band-pass FSS units contain a cross patch, the cross patch is placed in an opened cross slot, the upper surface of the lower layer plate is attached with a patch antenna, the lower surface of the lower layer plate is a metal floor, a coaxial line is used for feeding, the upper layer plate, the middle layer plate and the lower layer plate are air cavities.

2. The wideband low radar cross section antenna of claim 1, wherein, The height between the upper surface of the lower layer plate and the lower surface of the middle layer plate is greater than the height between the lower surface of the upper layer plate and the lower surface of the middle layer plate.

3. The wideband low radar cross section antenna of claim 1, wherein, The height between the upper surface of the lower layer plate and the lower surface of the middle layer plate is 23mm.

4. The wideband low radar cross section antenna of claim 1, wherein, The height between the lower surface of the upper layer plate and the lower surface of the middle layer plate is 8mm.

5. The wideband low radar cross section antenna of claim 1, wherein, The resistance of the lumped resistor is 90 ohms.

6. The wideband low radar cross section antenna of claim 1, wherein, The U-shaped microstrip line is a rectangular strip with a length of 5mm and a width of 0.5mm.

7. The wideband low radar cross section antenna of claim 1, wherein, The butterfly-shaped dipole is obtained by cutting two triangular patches from a rectangular patch.

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