Ultralow-profile high-gain circularly polarized folded transmission array antenna with low radar cross section

Abstract

The invention discloses an ultra-low-profile high-gain circular polarization folding transmission array antenna with a low radar cross section. The antenna comprises a PCM array, a transmission array, a reflection array and a feed source horn which are distributed in a chessboard mode. The PCM array of the chessboard type array is placed above the transmission array, and the PCM array and the transmission array are separated by an air layer 1; the transmission array is placed above the reflection array, and the transmission array and the reflection array are separated by an air layer 2; the center of the reflective array is provided with a rectangular hole, and the feed source horn is embedded in the rectangular hole. The folding transmission array antenna provided by the invention has broadband high-gain circular polarization radiation performance and out-of-band dual-frequency radar scattering cross section reduction.

Description

Technical Field

[0001] The invention belongs to antenna technology, and in particular relates to an ultra-low profile high-gain circularly polarized folded transmission array antenna with low radar scattering cross section. Background Art

[0002] The folded transmission array antenna is a high-gain and high-efficiency planar array antenna with low spatial feeding loss, flexible planar array element phase control, easy integration with platforms and systems, and convenient manufacturing and low cost. It has extremely important applications in military communications and detection systems with limited carrying space and stealth requirements.

[0003] In information network military systems, such as long-range radar, short-wave high-sensitivity sensor systems, and long-range wireless communications, high-gain antennas are an important component. At the same time, with the development of modern electronic countermeasure technology, radar stealth has become another key requirement for detection systems. Therefore, radar stealth technology and electromagnetic protection measures should be adopted in detection systems. In addition, due to the strict space limitations of detection platforms, efficient and low-profile antennas are urgently needed.

[0004] Although the folded transmission array antenna has a low profile, it is still very high for some specific detection platforms that require small-volume antennas. The traditional technology for reducing the cross-section of out-of-band dual-frequency radar has high profile and complex structure. Summary of the invention

[0005] The invention aims to provide an ultra-low profile high-gain circularly polarized folded transmission array antenna with low radar cross section.

[0006] The technical solution for realizing the present invention is: an ultra-low profile high-gain circularly polarized folded transmission array antenna with a low radar scattering cross section, comprising a PCM array, a transmission array, a reflection array and a feed horn arranged in a chessboard pattern; the PCM array arranged in a chessboard pattern is placed above the transmission array, and the two are separated by an air layer 1; the transmission array is placed above the reflection array, and the two are separated by an air layer 2; a rectangular hole is opened in the center of the reflection array, and the feed horn is placed in the rectangular hole and embedded.

[0007] Furthermore, the PCM array is composed of a PCM unit and a mirror unit thereof, the PCM unit is composed of a bidirectional arrow patch 1 and a dielectric layer 1, the mirror unit is obtained by rotating the PCM unit 90° around a center point, the PCM unit is arranged in the upper left and lower right parts of the array, and the mirror unit is arranged in the lower left and upper right parts of the array.

[0008] Furthermore, the transmission array is composed of a transmission unit of an RT structure, and the transmission unit is composed of a transmission layer, an intermediate layer, a receiving layer and a metal through-hole. The transmission layer is composed of a U-shaped slot corner patch with a truncated square split ring and a dielectric layer 2, which is located at the top, and the transmission layer patch is phase-modulated by rotation; the intermediate layer is composed of a thin metal layer with a circular hole in the center and a dielectric layer 3, which is located in the middle, and the thin metal layer is used to isolate the transmission layer and the receiving layer, and the dielectric layer 3 is used to connect the transmission layer and the receiving layer; the receiving layer is composed of a U-shaped slot patch with a square split ring and a dielectric layer 4, which is located at the bottom; the metal through-hole passes through the transmission layer, the intermediate layer and the receiving layer, and connects the transmission layer patch and the receiving layer patch.

[0009] Furthermore, the reflective array is composed of phase-adjustable reflective units, and the reflective units are composed of a bidirectional arrow patch 2 and a dielectric layer 5. The size of the bidirectional arrow unit varies according to the phase adjustment requirements.

[0010] Furthermore, the PCM units of the PCM array have the same periodic size as the transmission units of the transmission array, and the center projections of the two coincide in the vertical direction; the reflection units of the reflection array are half the periodic size of the transmission units of the transmission array, the area of ​​one transmission unit can cover four reflection units, and the projections of the transmission unit and the four reflection units coincide in the vertical direction.

[0011] Furthermore, the feed horn is a pyramid horn, and three layers of metal shell are added to be embedded in the center of the reflection array.

[0012] Furthermore, the height of the air layer 1 is h1=12.3 mm, the material used for the dielectric layer 1 is F4BM220, the thickness is 0.43 mm, the dielectric constant is 2.2, and the dielectric loss angle is 0.0015.

[0013] Furthermore, the height of the air layer 2 is h2=67.2 mm, the dielectric layer 2 and the dielectric layer 4 are made of F4BM350, with a thickness of 2 mm, a dielectric constant of 3.48, and a dielectric loss angle of 0.003, and the dielectric layer 3 is made of RO4450F, with a thickness of 0.1 mm, a dielectric constant of 3.52, and a dielectric loss angle of 0.0041.

[0014] Furthermore, the size of the rectangular hole is 43.8 mm×36 mm, the dielectric layer 5 is made of F4BM350, has a thickness of 3 mm, a dielectric constant of 3.48, and a dielectric loss factor of 0.003.

[0015] Furthermore, the transmission array and the reflection array are phase-adjusted simultaneously, i.e., double-sided phase-adjustment method. Under the condition of low profile, the transmission array phase-adjusts to compensate the path loss of the electromagnetic wave to generate a plane wave to achieve high gain, and the reflection array phase-adjusts to lengthen the equivalent focus of the folded transmission array to obtain a larger focal length, as follows:

[0016] The transmission array compensates for the phase difference caused by the distance between the equivalent feed source and different transmission units and the central transmission unit. The phase compensation formula of the mnth transmission unit is:

[0017]

[0018] Where k0 is the free space constant, x mn and mn is the x-axis distance and y-axis distance of the unit from the center unit, F is the focal length, is the phase of the central unit;

[0019] The reflective array compensates for the phase anomaly caused by the profile reduction, and the phase compensation formula of the mnth reflective unit is:

[0020]

[0021] The first half of the minus sign on the right side of the equation represents the phase of the electromagnetic wave before the phase compensation when it reaches the reflection array, and the second half of the minus sign on the right side of the equation represents the phase of the electromagnetic wave after the phase compensation. F2 is the equivalent focal length of the electromagnetic wave at the reflection array after the phase compensation.

[0022] During double-sided phase modulation, the feed source will first emit an x-polarized wave toward the transmission array. At this time, the x-polarized wave will be reflected by the transmission array and directed toward the reflection array. After phase compensation in the reflection array, the x-polarized wave will lengthen the equivalent focal length of the antenna and be polarized into a y-polarized wave. When the y-polarized wave is directed toward the transmission array again, it can be received by the transmission array and converted into a right-hand circularly polarized wave, thereby achieving phase compensation.

[0023] Compared with the prior art, the present invention has the following significant advantages: 1) The folded transmission array antenna of the present invention has broadband high-gain circular polarization radiation performance. 2) The present invention adopts a double-sided phase modulation method to reduce the cross-section of the antenna. 3) The present invention adopts a PCM array with a special size of chessboard arrangement to achieve RCS reduction in dual-band broadband. 4) The present invention decouples the transmission array and the PCM array with chessboard arrangement, so that the transition band also has a certain RCS reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a cross-sectional view of an ultra-low profile high-gain circularly polarized folded transmission array antenna with a low radar cross-section according to the present invention.

[0025] Figure 2It is a simulation schematic diagram of the ultra-low profile high-gain circularly polarized folded transmission array antenna with low radar scattering cross section of the present invention.

[0026] Figure 3 It is a three-dimensional diagram of the corresponding positions of the PCM unit, the transmission unit, and the reflection unit of the present invention.

[0027] Figure 4 This is the PCM patch diagram of the present invention.

[0028] Figure 5 It is the patch layer diagram of the transmission unit, where (a) is the transmission layer patch diagram and (b) is the receiving layer unit patch diagram.

[0029] Figure 6 This is the reflection performance diagram of the PCM unit.

[0030] Figure 7 This is the transmission performance diagram when the transmission unit is not truncated.

[0031] Figure 8 This is the reflection performance diagram after the PCM unit and the transmission unit are combined.

[0032] Fig. 9 This is the transmission performance diagram after the PCM unit and the transmission unit are combined and truncation measures are taken.

[0033] Fig.10 This is a three-dimensional view of the reflection unit of the present invention.

[0034] Fig.11 This is a three-view diagram of the speaker feed of the present invention.

[0035] Fig.12 Measured and simulated S-parameter diagrams of the antenna of the present invention.

[0036] Fig.13 Measured and simulated gain diagrams of the antenna of the present invention.

[0037] Fig.14 Measured and simulated directional diagrams of the antenna of the present invention when Phi=0° at 9.9 GHz.

[0038] Fig.15 Measured and simulated directional diagrams of the antenna of the present invention when Phi=90° at 9.9 GHz.

[0039] Fig.16 The RCS diagram after subtracting the ground from the measured and simulated RCS of the antenna of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0041] The present invention proposes to use a double-sided phase modulation method to further reduce the cross-section of the folded transmission array antenna, and designs a PCM array with a chessboard arrangement that can achieve dual-frequency RCS reduction using only a single-layer structure.

[0042] Combination Figure 1 , an ultra-low profile high-gain circularly polarized folded transmission array antenna with a low radar scattering cross section, including a PCM array 1 arranged in a chessboard pattern, a transmission array 2, a reflection array 3, and a feed horn 4; the PCM array 1 arranged in a chessboard pattern is placed above the transmission array 2, and the two are separated by an air layer 1; the transmission array 2 is placed above the reflection array 3, and the two are separated by an air layer 2; a rectangular hole is opened in the center of the reflection array 3, and the feed horn 4 is placed in the rectangular hole and embedded.

[0043] The PCM array 1 is composed of a PCM unit and a mirror unit thereof, wherein the mirror unit is obtained by rotating the PCM unit 90° around the center point. The PCM array is arranged in a checkerboard pattern: the PCM units are arranged in the upper left and lower right parts of the array, and the mirror units are arranged in the lower left and upper right parts of the array. Through the checkerboard arrangement of the PCM unit and its mirror unit, the scattered energy can be redirected to a 45° plane different from the incident direction, thereby achieving RCS reduction in the incident direction of the antenna.

[0044] The double-sided phase modulation method is used to phase-modulate the transmission array 2 and the reflection array 3 simultaneously. Under low-profile conditions, the transmission array phase modulation can compensate for the path loss of the electromagnetic wave to generate a plane wave to achieve high gain, and the reflection array phase modulation can lengthen the equivalent focus of the folded transmission array to obtain a larger focal length.

[0045] Furthermore, the transmission array 2 is mainly responsible for compensating the phase difference caused by the distance between the equivalent feed source and different transmission units and the central transmission unit, so the phase compensation formula of the mnth transmission unit is:

[0046]

[0047] Where k0 is the free space constant, x mn and mn is the x-axis distance and y-axis distance of the unit from the center unit, F is the focal length, is the phase of the center unit.

[0048] Furthermore, the reflective array 3 mainly compensates for the phase anomaly caused by the profile reduction, so the phase compensation formula of the mnth reflective unit is:

[0049]

[0050] The first half of the minus sign on the right side of the equation represents the phase of the electromagnetic wave before the phase compensation when it reaches the reflection array, and the second half of the minus sign on the right side of the equation represents the phase of the electromagnetic wave after the phase compensation. F2 is the equivalent focal length of the electromagnetic wave at the reflection array after the phase compensation.

[0051] During double-sided phase modulation, the feed source will first emit an x-polarized wave toward the transmission array. At this time, the x-polarized wave will be reflected by the transmission array and directed toward the reflection array. After phase complementation at the reflection array, the x-polarized wave will lengthen the equivalent focal length of the antenna and be polarized into a y-polarized wave. When the y-polarized wave is directed toward the transmission array again, it can be received by the transmission array and converted into a right-hand circularly polarized wave, and phase complementation can be achieved to produce high-gain radiation.

[0052] The PCM unit is composed of a bidirectional arrow patch 1 and a dielectric layer 1. The bidirectional arrow patch 1 is composed of a bevel patch and a double L-shaped patch. The size of the bevel patch can control the polarization conversion performance of the out-of-band low frequency, and the size of the double L-shaped patch can control the polarization conversion performance of the out-of-band high frequency.

[0053] The transmission array 2 is composed of transmission units of RT structure, and the transmission units are composed of transmission layer, middle layer, receiving layer, and metal through hole. The transmission layer is composed of U-shaped slotted corner patch with truncated square split ring and dielectric layer 2, which is located at the top, and the transmission layer patch can be phase-adjusted by rotation; the middle layer is composed of a thin metal layer with a circular hole in the center and dielectric layer 3, which is located in the middle, and the thin metal layer is used to isolate the transmission layer and the receiving layer, and the dielectric layer 3 is used to connect the transmission layer and the receiving layer; the receiving layer is composed of U-shaped slot patch with square split ring and dielectric layer 4, which is located at the bottom; the metal through hole penetrates the transmission layer, middle layer, and receiving layer, and connects the transmission layer patch and the receiving layer patch.

[0054] The transmission layer patch is composed of a U-shaped slot cut corner square structure and a square split ring. The U-shaped slot can increase the low-frequency bandwidth of the patch, and the square split ring can increase the high-frequency bandwidth of the patch and achieve good high-frequency out-of-band suppression characteristics.

[0055] Furthermore, at the four ends of the square split ring of the transmission layer patch of the transmission unit, a truncation of length k is implemented at a distance m along the x-axis direction and the y-axis direction respectively. The truncation can reduce the coupling of the reflection performance of the PCM unit and the transmission unit at high frequencies.

[0056] The reflective array 3 is composed of phase-adjustable reflective units, and the reflective units are composed of bidirectional arrow patches 2 and a dielectric layer 5. The size of the bidirectional arrow patches 2 will vary accordingly according to phase adjustment requirements.

[0057] Combination Figure 3 The period of the PCM unit is the same as that of the transmission unit, and the center projections of the two coincide in the vertical direction. The reflection unit of the reflection array is half the period of the transmission unit of the transmission array, the area of ​​a single transmission unit can cover four reflection units, and the projections of the transmission unit and the four reflection units coincide in the vertical direction. From top to bottom, they are arranged in the order of PCM unit, transmission unit, and reflection unit.

[0058] The feed horn 4 is a pyramid horn, and three layers of metal shell are added to embed in the center of the reflection array.

[0059] Example

[0060] In order to verify the effectiveness of the scheme of the present invention, the following experimental design was carried out.

[0061] Combination Figure 1 In this embodiment, the height of the air layer 1 is h1=12.3 mm, the material used for the dielectric layer 1 is F4BM220, the thickness is 0.43 mm, the dielectric constant is 2.2, and the dielectric loss angle is 0.0015.

[0062] The height of the air layer 2 is h2=48.3 mm. The material used for the dielectric layer 2 and the dielectric layer 4 is F4BM350, with a thickness of 2 mm, a dielectric constant of 3.48, and a dielectric loss angle of 0.003. The material used for the dielectric layer 3 is RO4450F, with a thickness of 0.1 mm, a dielectric constant of 3.52, and a dielectric loss angle of 0.0041.

[0063] The size of the rectangular hole is 43.8 mm×36 mm, and the material used for the dielectric layer 5 is F4BM350, with a thickness of 3 mm, a dielectric constant of 3.48, and a dielectric loss factor of 0.003.

[0064] Figure 2 The simulation diagram of the antenna in this embodiment is shown in Figure 2. The transmission unit and PCM unit have a total of 24×24 units, the reflection unit has a total of 48×48 units, and the antenna aperture size is 336mm×336mm. The F / D value is 1, and the cross-section height is designed to be F / 5, which is 67.2mm.

[0065] Combination Figure 3 The period of the PCM unit and the transmission unit is 14mm, and the center projections of the two coincide in the vertical direction. The period of the reflection unit is 7mm, the area of ​​a single transmission unit can cover four reflection units, and the projections of the transmission unit and the four reflection units coincide in the vertical direction. From top to bottom, they are arranged in the order of PCM unit, transmission unit, and reflection unit.

[0066] Figure 4The double-arrow patch 1 is composed of a bevel patch and a double L-shaped patch. The bevel patch can achieve the polarization conversion performance of the out-of-band low frequency, and the double L-shaped patch can achieve the polarization conversion performance of the out-of-band high frequency. The parameters of the double-arrow patch 1 are: a1 = 4.82, l 10 =13, w1=0.6, w2=0.5.

[0067] The transmission unit is composed of a transmission layer, an intermediate layer, a receiving layer, and a metal through hole. The transmission layer is composed of a U-shaped slotted corner patch with a truncated square split ring and a dielectric layer 2, which is located at the top. The transmission layer patch can be phase-adjusted by rotation, and the angle of rotation is the phase-adjusting angle; the intermediate layer is composed of a thin metal layer with a circular hole in the center and a dielectric layer 3, which is located in the middle. The diameter of the circular hole is 1.8mm, and the thickness of the thin metal layer is 0.1mm. The thin metal layer is used to isolate the transmission layer and the receiving layer, and the dielectric layer 3 is used to connect the transmission layer and the receiving layer; the receiving layer is composed of a U-shaped slot patch with a square split ring and a dielectric layer 4, which is located at the bottom; the metal through hole penetrates the transmission layer, the intermediate layer, and the receiving layer, and connects the transmission layer patch and the receiving layer patch. The diameter of the metal through hole is 0.6mm.

[0068] Figure 5 (a) is a transmission layer patch, which consists of a U-shaped slit corner-cut square structure and a square split ring. The U-shaped slit can increase the low-frequency bandwidth of the patch, and the square split ring can increase the high-frequency bandwidth of the patch and achieve good high-frequency out-of-band suppression characteristics. The corner size is 1.9mm.

[0069] At the four ends of the square split ring of the transmission layer patch of the transmission unit, a truncation with a length of k=0.4mm is implemented at a distance of m=0.6mm along the x-axis direction and the y-axis direction respectively. The truncation can reduce the coupling of the high-frequency reflection performance of the PCM unit and the transmission unit.

[0070] Figure 5 (b) is the receiving layer patch, which has a similar shape to the transmitting layer patch, but is not truncated and has no corner cuts.

[0071] The receiving layer patch parameters are: L1 = 9, L2 = 6.4, L3 = 4, L5 = 2.4, q2 = 1, q3 = 1.2, p = 14, where p is the period of the unit.

[0072] The PCM unit and the transmission unit are integrated, hereinafter referred to as the integrated unit, which can achieve out-of-band high and low frequency polarization conversion performance without excessive degradation of in-band radiation performance.

[0073] Figure 6The figure is the reflection performance diagram of the PCM unit. When a single-layer PCM unit is loaded onto a metal ground with an air gap of 12.3mm between the unit and the metal ground, the single-layer PCM unit can achieve a polarization conversion performance of more than -1dB in the low-frequency band of 2.85-7.93GHz and the high-frequency band of 12.34-16.26GHz, and there is no polarization conversion performance in the passband of 8-12GHz. In addition, in the transition band from polarization conversion to non-polarization conversion, that is, the adjacent bands with 8GHz and 12GHz as the center frequencies, the Rxy curve of the PCM unit has a steep change. This good passband edge selectivity enables the PCM and radiation unit to achieve low RCS and high-gain radiation when combined, and can effectively narrow the gap between the radiation band and the RCS reduction band.

[0074] The size of the bevel patch can control the polarization performance of the low frequency outside the PCM unit band, and the size of the double L-shaped patch can control the polarization performance of the high frequency outside the PCM unit band. The bevel patch and the double L-shaped patch are approximately perpendicular in position, so the polarization effects cancel each other out in the passband of 8-12GHz, achieving non-polarization performance in the passband.

[0075] Figure 7 This is the transmission performance diagram when the transmission unit is not truncated. At the center frequency of about 10G, the transmission amplitude of the unit reaches 0.96, achieving a high transmission conversion rate. In the 8.38-12.38GHz band, the transmission amplitude is maintained above 0.8. In the edge area of ​​the passband, that is, the adjacent bands with 8.3GHz and 12.4GHz as the center frequencies, it can be seen that the amplitude curve changes very steeply, and the unit exhibits good out-of-band suppression characteristics and passband edge selectivity. The steep edge characteristics of the transmission unit prevent it from generating too much coupling when combined with the scattering cancellation metasurface, which is conducive to eliminating the gap between the antenna radiation band and the RCS reduction band.

[0076] Figure 8 This is a reflection performance diagram after the PCM unit and the transmission unit are integrated and truncated. During integration, the thin metal layer in the middle layer of the transmission unit provides a metal ground for the PCM unit; and in order to achieve the decoupling of the high-frequency reflection performance of the PCM unit and the transmission unit, the square split ring of the transmission layer patch of the transmission unit is also truncated. The integrated unit has at least -1dB polarization conversion performance in the range of 2.54GHz-7.98GHz and 12.38-16.63GHz.

[0077] Fig. 9 This is the transmission performance diagram after the PCM unit and the transmission unit are combined and truncated. The maximum transmission amplitude is 0.95, which is 0.1 lower than when the transmission unit is not truncated. The gain of the antenna array is reduced. The amplitude of the unit is greater than 0.8 in the range of 8.29GHz-11.64GHz.

[0078] Combination Fig.10 is the three-dimensional view of the reflection unit, and its parameters are: p r =7,h r =3, a2=3.2, l 20 =4.6, w3=0.6. When the reflector unit is phase-modulated, its phase can be changed by changing the size of a2. The smaller a2 is, the more phase the reflector unit compensates.

[0079] Combination Fig.11 The feed horn is a pyramid horn, and three layers of metal shell are added to embed in the center of the reflection array.

[0080] The pyramid horn feed uses a waveguide port of 22.86mm×10.16mm as input, and the horn aperture is 31mm×24mm. The first layer of rectangular shell is to be embedded in the reflective array, so the thickness is consistent with the thickness of the reflective array medium, which is 3mm, and the aperture size is 32mm×40mm. The second layer of rectangular shell is to fix the feed source as a whole to the reflective array, so its size is larger than the first layer of rectangular shell, which is 45mm×45mm, and the thickness is also 3mm. And four circular holes are punched around it to facilitate screw fixation to the dielectric layer of the reflective array. The third rectangular shell is for easy processing and easy assembly of the horn feed and the waveguide to coaxial structure, so its size is consistent with the flange of the waveguide to coaxial structure, which is 34mm×34mm and the thickness is 22.2mm.

[0081] Fig.12 The S parameter diagram of the antenna measurement and simulation shows that the antenna has extremely high impedance matching near 10 GHz, and has an S close to -10 dB in the radiation band of 8.5 GHZ-12.5 GHz. 11 .

[0082] Fig.13 The measured and simulated gain-to-axis ratio diagrams for the antenna show that the antenna achieves a maximum gain of 27.52dBic at 9.9GHz and an aperture efficiency of 35.6%. In addition, the 3dB gain bandwidth is 21.9% (8.9GHz-11.1GHz) and the 3dB axial ratio bandwidth is 28.5% (8.4GHz-11.2GHz).

[0083] Fig.14 The radiation pattern of φ=0° at 9.9GHz measured and simulated for the antenna, the main lobe gain of the main polarization is 27.52dBic, the cross-polarization main lobe gain is 5.3dBic, and the main polarization sidelobe is -17.5dB.

[0084] Fig.15The radiation pattern of φ=90° at 9.9GHz measured and simulated for the antenna is as follows: the main-polarization main-lobe gain is 27.52dBic, the cross-polarization main-lobe gain is 5.1dBic, and the main-polarization sidelobe is -14.9dB.

[0085] Fig.16 The RCS measured and simulated for the antenna is subtracted from the ground under different polarized wave incidence. The antenna achieves at least 10dB RCS reduction at 3.24GHz-7.53GHz and 13.2GHz-16.42GHz out-of-band, respectively. And the RCS reduction of the antenna remains basically unchanged under 45° polarized wave, x-polarized wave, and y-polarized wave incidence. Because the transmitting antenna and the receiving antenna cannot overlap during antenna measurement, there is an angle of 4.2° between the two, so the RCS measurement value of the high-frequency out-of-band part is higher than the simulated value.

[0086] The antenna also has a significant RCS reduction in its own radiation band, and the RCS is slightly different when the polarization of the incident wave is different. The antenna has at least 10dB of RCS reduction in the 9.4GHz-10.23GHz range. This is because the transmission unit of the FTA is rotated for phase compensation, and the transmission units with different rotation angles have different phase shift effects on the incident wave, so that the scattered energy can also be scattered in different directions. The antenna as a whole has a certain RCS reduction capability in the full frequency band of 2.5GHz-17GHz.

[0087] In summary, the ultra-low profile high-gain circularly polarized folded transmission array antenna with low radar cross section of the present invention can achieve high-gain broadband circularly polarized radiation within the band, and combined with the specific polarization-transferred bidirectional arrow units arranged in a chessboard pattern, it realizes the reduction of the radar cross section of the double-side band outside the band. The radiation part has the characteristics of a plane and a low profile, and the radar cross section reduction part has the characteristics of double-side band reduction, high transmission within the band, and a simple structure without stacking.

[0088] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, 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 above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. An ultra-low profile high-gain circularly polarized folded transmission array antenna with low radar cross section, characterized in that: The invention comprises a PCM array (1) arranged in a chessboard pattern, a transmission array (2), a reflection array (3) and a feed horn (4); the PCM array (1) arranged in a chessboard pattern is placed above the transmission array (2), and the two are separated by an air layer 1; the transmission array (2) is placed above the reflection array (3), and the two are separated by an air layer 2; a rectangular hole is opened in the center of the reflection array (3), and the feed horn (4) is placed in the rectangular hole and embedded.

2. The ultra-low profile high-gain circularly polarized folded transmission array antenna with low radar cross section according to claim 1, characterized in that: The PCM array is composed of a PCM unit and a mirror unit thereof. The PCM unit is composed of a bidirectional arrow patch 1 and a dielectric layer 1. The mirror unit is obtained by rotating the PCM unit 90° around a center point. The PCM unit is arranged in the upper left and lower right parts of the array, and the mirror unit is arranged in the lower left and upper right parts of the array.

3. The ultra-low profile high-gain circularly polarized folded transmission array antenna with low radar cross section according to claim 1, characterized in that: The transmission array is composed of a transmission unit of RT structure, and the transmission unit is composed of a transmission layer, an intermediate layer, a receiving layer and a metal through hole. The transmission layer is composed of a U-shaped slotted corner patch with a truncated square split ring and a dielectric layer 2, which is located at the top. The transmission layer patch is phase-modulated by rotation; The intermediate layer is composed of a thin metal layer with a circular hole in the center and a dielectric layer 3, which is located in the middle. The thin metal layer is used to isolate the transmission layer and the receiving layer, and the dielectric layer 3 is used to connect the transmission layer and the receiving layer; the receiving layer is composed of a U-shaped seam patch with a square split ring and a dielectric layer 4, which is located at the bottom; the metal through hole passes through the transmission layer, the intermediate layer and the receiving layer, and connects the transmission layer patch and the receiving layer patch.

4. The ultra-low profile high-gain circularly polarized folded transmission array antenna with low radar cross section according to claim 1, characterized in that: The reflective array is composed of phase-adjustable reflective units, which are composed of a bidirectional arrow patch 2 and a dielectric layer 5. The size of the bidirectional arrow unit varies according to the phase adjustment requirements.

5. The ultra-low profile high-gain circularly polarized folded transmission array antenna with low radar cross section according to claim 1, characterized in that: The PCM units of the PCM array have the same periodic size as the transmission units of the transmission array, and their center projections coincide with each other in the vertical direction; the reflection units of the reflection array are half the periodic size of the transmission units of the transmission array, the area of ​​one transmission unit can cover four reflection units, and the projections of the transmission unit and the four reflection units coincide with each other in the vertical direction.

6. The ultra-low profile high-gain circularly polarized folded transmission array antenna with low radar cross section according to claim 1, characterized in that: The feed horn (4) is a pyramid horn, and is provided with three layers of metal shell so as to be embedded in the center of the reflection array (3).

7. The ultra-low profile high-gain circularly polarized folded transmission array antenna with low radar cross section according to claim 2, characterized in that: The height of the air layer 1 is h1=12.3 mm. The material used for the dielectric layer 1 is F4BM220, with a thickness of 0.43 mm, a dielectric constant of 2.2, and a dielectric loss angle of 0.0015.

8. The ultra-low profile high-gain circularly polarized folded transmission array antenna with low radar cross section according to claim 3, characterized in that: The height of the air layer 2 is h2=67.2 mm. The dielectric layer 2 and the dielectric layer 4 are made of F4BM350 with a thickness of 2 mm, a dielectric constant of 3.48, and a dielectric loss angle of 0.

003. The dielectric layer 3 is made of RO4450F with a thickness of 0.1 mm, a dielectric constant of 3.52, and a dielectric loss angle of 0.0041.

9. The ultra-low profile high-gain circularly polarized folded transmission array antenna with low radar cross section according to claim 4, characterized in that: The rectangular hole has a size of 43.8 mm×36 mm, and the dielectric layer 5 is made of F4BM350 with a thickness of 3 mm, a dielectric constant of 3.48, and a dielectric loss factor of 0.

003.

10. The ultra-low profile high-gain circularly polarized folded transmission array antenna with low radar cross section according to claim 1, characterized in that: The transmission array and the reflection array are phase-modulated simultaneously, i.e., double-sided phase modulation. Under the condition of low profile, the transmission array phase-modulates to compensate for the path loss of the electromagnetic wave to generate a plane wave to achieve high gain, and the reflection array phase-modulates to lengthen the equivalent focus of the folded transmission array to obtain a larger focal length, as follows: The transmission array compensates for the phase difference caused by the distance between the equivalent feed source and different transmission units and the central transmission unit. The phase compensation formula of the mnth transmission unit is: Where k0 is the free space constant, x mn and mn is the x-axis distance and y-axis distance of the unit from the center unit, F is the focal length, is the phase of the central unit; The reflective array compensates for the phase anomaly caused by the profile reduction, and the phase compensation formula of the mnth reflective unit is: The first half of the minus sign on the right side of the equation represents the phase of the electromagnetic wave before the phase compensation when it reaches the reflection array, and the second half of the minus sign on the right side of the equation represents the phase of the electromagnetic wave after the phase compensation. F2 is the equivalent focal length of the electromagnetic wave at the reflection array after the phase compensation. During double-sided phase modulation, the feed source will first emit an x-polarized wave toward the transmission array. At this time, the x-polarized wave will be reflected by the transmission array and directed toward the reflection array. After phase compensation in the reflection array, the x-polarized wave will lengthen the equivalent focal length of the antenna and be polarized into a y-polarized wave. When the y-polarized wave is directed toward the transmission array again, it can be received by the transmission array and converted into a right-hand circularly polarized wave, thereby achieving phase compensation.

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