Broadband low-RCS compact circularly polarized antenna based on polarization conversion technology

Abstract

The invention provides a broadband low-RCS compact circularly polarized antenna based on a polarization conversion technology. The broadband low-RCS compact circularly polarized antenna comprises a polarization conversion unit, a first-layer dielectric plate, a metal grounding plate, a second-layer dielectric plate and a feed network, the polarization conversion unit is arranged on the upper layer of the first dielectric plate; the lower layer of the first dielectric plate is a metal grounding plate; the lower layer of the metal grounding plate is a second dielectric plate; and the lower layer of the second dielectric plate is a feed network. According to the antenna, the number of arranged units is reduced, the performance of RCS reduction is maintained, the size is reduced, the antenna is more convenient, and the radar stealth performance of the antenna is further improved.

Description

Technical Field

[0001] This invention belongs to the field of microwave and millimeter-wave band technology, specifically relating to a broadband low RCS compact circularly polarized antenna based on polarization conversion technology. Background Technology

[0002] In the field of modern radar detection, the radar cross section (RCS) has become a hot research topic recently. RCS is defined as the ratio of the power reflected by a target per unit solid angle to the incident power, measuring the target's stealth capability under radar detection. RCS is affected not only by the shape, size, and material properties of the object being detected, but also by factors such as the frequency and polarization of the radar wave. Polarization conversion metasurfaces (PCMs) are a common RCS reduction scheme. Their principle involves periodically arranging two polarization conversion units. After the incident wave is reflected by these units, its polarization direction is deflected by ±90°, creating a 180° phase difference. The two reflected waves then converge and cancel each other out in the far field.

[0003] Using metasurfaces to reduce RCS is not only applied to radar stealth of weapon platforms and vehicles, but can also be used to further reduce the RCS of antennas through co-design. Low-RCS surfaces consist of multiple metal patches, with a structure similar to an array antenna. Therefore, a feeding structure can be introduced to use the metal patches of the metasurface as antenna elements to form an array antenna. Co-designing the antenna and the low-RCS metasurface not only improves the antenna's stealth performance but also increases the utilization rate of the metasurface.

[0004] Due to the electromagnetic properties of metasurfaces, low-RCS surfaces can only operate within a limited bandwidth. Electromagnetic signals outside or below a specific frequency band cannot achieve good RCS reduction. Therefore, improving the bandwidth for RCS reduction is one of the most pressing issues in low-RCS metasurface research. On the other hand, achieving good RCS reduction performance with low-RCS metasurfaces typically requires a sufficient number of elements and a large enough area. This leads to a larger final product size and area when co-designing metasurfaces and antennas. This not only increases costs but also makes the metasurface antenna very bulky and inconvenient to carry. Summary of the Invention

[0005] Purpose of the invention: The technical problem to be solved by the present invention is to provide a broadband low RCS compact circularly polarized antenna based on polarization conversion technology, which has the characteristics of broadband RCS reduction, high gain circular polarization and small size, in order to overcome the shortcomings of the prior art.

[0006] The antenna of the present invention includes a polarization conversion unit, a first dielectric substrate, a metal ground plane, a second dielectric substrate, and a feed network; The polarization conversion unit is disposed on the upper layer of the first dielectric substrate; The lower layer of the first dielectric substrate is a metal ground plane; The lower layer of the metal ground plane is a second dielectric plate; The lower layer of the second dielectric substrate is the power supply network.

[0007] There are N polarization conversion units, which are arranged alternately in a checkerboard pattern on the upper surface of the first dielectric substrate to form a polarization conversion array.

[0008] The polarization conversion unit includes a metal ground plane and a metal patch; The metal patch includes a square patch with chamfered corners at the lower left and upper right corners, a pair of I-shaped patches, and a pair of right-angled V-shaped patches; The right-angled V-shaped patch is located on the extension of the diagonal of the square patch without the corners being cut, and the V-shaped angle of the right-angled V-shaped patch extends outward along the diagonal of the square patch; The I-shaped patch is located on the diagonal extension line of the square patch after the diagonal has been cut off, and the long side of the I-shaped patch is parallel to the diagonal of the square patch.

[0009] N takes the value 16.

[0010] The antenna also includes a circularly polarized array antenna, which is an array antenna composed of eight metal patches selected from the polarization conversion array forming a U-shaped array. The polarization conversion units are arranged in two arrays in a 2×2 configuration: a +45° polarization conversion array and a -45° polarization conversion array.

[0011] The two arrays have the same geometry; the -45° polarization conversion array is obtained by rotating the +45° polarization conversion array by 90° around the array's center of symmetry. Two +45° polarization conversion arrays and two -45° polarization conversion arrays are arranged in a grid pattern, with arrays of the same type placed diagonally.

[0012] Both the first and second dielectric substrates use F4B material with a dielectric constant of 2.65.

[0013] The metal ground plane is located between the first dielectric substrate and the second dielectric substrate, and there are slits as radiation gaps at the positions of the patch units that serve as antennas for the corresponding circularly polarized array antenna.

[0014] The power supply network includes a 50Ω characteristic impedance microstrip line, a 70Ω characteristic impedance microstrip line, and three 100Ω resistors.

[0015] The 50Ω characteristic impedance microstrip line, the 70Ω characteristic impedance microstrip line and the three 100Ω resistors together form three Wilkinson power dividers, which constitute a two-stage power divider network and split one input signal into four signals with a phase difference of 90° in sequence through a phase shifter. Each of the four signals, which are 90° out of phase, is equipped with a T-shaped power divider at its end. The signal is then split into two equal-phase signals and distributed to each antenna element in the circularly polarized array antenna through a feed network.

[0016] Beneficial effects: This invention provides a broadband low RCS compact circularly polarized antenna based on polarization conversion technology, which has a broadband RCS reduction effect; some polarization conversion elements in the polarization conversion array also serve as radiating elements of the circularly polarized array antenna; the number of elements is reduced while maintaining the RCS reduction performance, and the reduced size makes the antenna more convenient while further improving the antenna's radar stealth performance; the "U"-shaped circularly polarized array antenna has high radiation gain, a circular polarization axial ratio of less than 3dB in the operating frequency band, and a field pattern that is symmetrical between the E-plane and H-plane. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0018] Figure 2 This is a schematic diagram of the polarization conversion unit structure of the present invention.

[0019] Figure 3 This is a diagram illustrating the polarization conversion effect of the present invention.

[0020] Figure 4 A schematic diagram of the power supply network structure of this invention.

[0021] Figure 5 This is a diagram of the port reflection parameters of the present invention.

[0022] Figure 6 This is a diagram illustrating the RCS reduction effect of the present invention.

[0023] Figure 7 This is the effect of the axial ratio in this invention.

[0024] Figure 8 This is a 1D far-field pattern of the E-plane and H-plane at 15GHz according to the present invention.

[0025] Figure 9 This is a 1D far-field pattern of the E-plane and H-plane at 15.5 GHz according to the present invention.

[0026] Figure 10 This is a 1D far-field pattern of the E-plane and H-plane at 16GHz according to the present invention.

[0027] Explanation of reference numerals in the attached figures: 1, polarization conversion array; 2, first dielectric substrate; 3, metal ground plane; 4, second dielectric substrate; 5, feed network; 6, circularly polarized array antenna. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0029] like Figure 1 As shown, this embodiment of the invention provides a broadband low RCS compact circularly polarized antenna based on polarization conversion technology. The invention has a five-layer structure: a polarization conversion array 1, a first dielectric substrate 2, a metal ground plane 3, a second dielectric substrate 4, and a feed network 5. The first dielectric substrate 2 has a thickness of H1 = 1.8 mm, and the second dielectric substrate 4 has a thickness of H2 = 0.25 mm. Both dielectric substrates are squares with a width of W = 39.5 mm and are made of F4B material with a dielectric constant of 2.65.

[0030] like Figure 1 As shown, a set of diagonal patches is selected from each +45° polarization conversion array or -45° polarization conversion array as an antenna. The four sets of diagonal patches form a "U"-shaped antenna array, which is the circular polarization array antenna 6 in this invention. Each patch is fed as an individual antenna element.

[0031] like Figure 2 As shown, a single polarization conversion unit consists of surface metal patches and a metal ground plane. The central portion of the metal patch is obtained by cutting an isosceles right triangle with a leg length of b=3mm from a square with side length a=5mm. The I-shaped portion of the metal patch consists of rectangular strips of metal patches with length c=3mm and width e=0.5mm, with a distance g=1.16mm between the I-shaped metal patch and the central patch. The right-angled V-shaped portion of the metal patch consists of two rectangular metal patches with length d=2.5mm and width e=0.5mm, with a distance f=0.5mm between the right-angled V-shaped metal patch and the central patch. The unit period of the polarization conversion unit is P=9.5mm, and the polarization conversion surface is arranged in a checkerboard pattern.

[0032] like Figure 2As shown, the right-angled V-shaped patch and the central patch form a capacitor-like structure. When electromagnetic waves irradiate the metal patch and generate surface current, the current in the u-direction exhibits capacitive behavior. The I-shaped patch has an inductor-like structure; when electromagnetic waves irradiate the metal patch and generate surface current, the current in the v-direction exhibits inductive behavior. By adjusting the parameters of the right-angled V-shaped patch and the I-shaped patch, the current characteristics in the u and v directions can be changed, that is, the reflection phase of the u and v-direction components after the electromagnetic wave is incident can be altered. When the reflection phase difference between the u and v-direction components reaches 180°, a better polarization conversion effect can be obtained.

[0033] like Figure 3 As shown, when the simulation sets the unit boundary condition to a periodic structure and the electromagnetic wave is polarized along the x-axis and incident perpendicularly along the z-axis, the reflected wave component Rxx along the polarization direction along the x-axis is reduced by more than 10 dB in the 13.8 GHz to 23.5 GHz range, and the reflected wave component Rxy with the polarization direction converted to the y-axis is close to 0 dB. This indicates that the periodic surface composed of this unit structure can achieve a good polarization conversion effect in this frequency band.

[0034] like Figure 4 As shown, the feed network of this invention mainly consists of a 50Ω characteristic impedance microstrip line with a width of W50 = 0.65m, and a two-stage power divider network composed of three Wilkinson power dividers, which divide the original signal into four signals with equal amplitude. These four signals are modulated into four signals with phases of 0°, 90°, 180°, and 270° respectively by a phase shifter, thereby achieving circular polarization feeding. The four signals are further divided into eight signals by four T-shaped power dividers. Each signal is ultimately fed to the uppermost metal patch, i.e., the antenna patch, through a slot with a length of L1 = 6mm and a width of L2 = 0.3mm. A fan-shaped patch with a radius of R = 1.15mm is set at the feed line terminal. This fan-shaped patch optimizes the impedance matching between the feed line and the slot while reducing the back lobe radiation of the antenna to a certain extent.

[0035] like Figure 5 As shown, the port reflection coefficient of this invention remains basically below -10dB, exhibiting excellent anti-reflection performance. Furthermore, there is a noticeable dip at the antenna's radiation center frequency of 16GHz, indicating that more energy is converted into electromagnetic wave radiation at this frequency.

[0036] like Figure 6 As shown, the RCS reduction range of this invention is 13.7GHz~27.4GHz. Within this range, it can maintain an RCS reduction of more than 10dB compared to the reference antenna (equal area metal plate). The 10dB RCS relative bandwidth reaches 66.7%.

[0037] like Figure 7As shown, the present invention achieves a circular polarization axial ratio of less than 3dB in the range of 12.5GHz to 16.5GHz, a minimum axial ratio of 0.23dB at 15.3GHz, and a good circular polarization effect at 1dB at 16GHz.

[0038] like Figure 8 , Figure 9 , Figure 10 As shown, the present invention has a maximum gain of 11.43 dBi at 15 GHz, a maximum gain of 11.98 dBi at 15.5 GHz, and a maximum gain of 12.22 dBi at 16 GHz, and exhibits good symmetry in both the E-plane and H-plane.

[0039] This invention provides a broadband, low RCS, compact circularly polarized antenna based on polarization conversion technology. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A broadband, low RCS, compact circularly polarized antenna based on polarization conversion technology, characterized in that, It includes a polarization conversion unit, a first dielectric substrate (2), a metal ground plane (3), a second dielectric substrate (4), and a power supply network (5); The polarization conversion unit is disposed on the upper layer of the first dielectric substrate (2); The lower layer of the first dielectric substrate (2) is a metal ground plane (3); The lower layer of the metal grounding plate (3) is the second medium plate (4). The lower layer of the second dielectric substrate (4) is the power supply network (5).

2. The broadband low RCS compact circularly polarized antenna based on polarization conversion technology according to claim 1, characterized in that, There are N polarization conversion units, and the N polarization conversion units are arranged alternately in a checkerboard pattern on the upper surface of the first dielectric substrate to form a polarization conversion array (1).

3. A broadband low RCS compact circularly polarized antenna based on polarization conversion technology according to claim 2, characterized in that, The polarization conversion unit includes a metal ground plane and a metal patch; The metal patch includes a square patch with chamfered corners at the lower left and upper right corners, a pair of I-shaped patches, and a pair of right-angled V-shaped patches; The right-angled V-shaped patch is located on the extension of the diagonal of the square patch without the corners being cut, and the V-shaped angle of the right-angled V-shaped patch extends outward along the diagonal of the square patch; The I-shaped patch is located on the diagonal extension line of the square patch after the diagonal has been cut off, and the long side of the I-shaped patch is parallel to the diagonal of the square patch.

4. A broadband low RCS compact circularly polarized antenna based on polarization conversion technology according to claim 3, characterized in that, N takes the value 16.

5. A broadband low RCS compact circularly polarized antenna based on polarization conversion technology according to claim 4, characterized in that, It also includes a circularly polarized array antenna, which is an array antenna composed of eight metal patches selected from the polarization conversion array (1) forming a square-shaped array.

6. A broadband low RCS compact circularly polarized antenna based on polarization conversion technology according to claim 5, characterized in that, The polarization conversion units are arranged in two arrays in the form of a 2×2 array: a +45° polarization conversion array and a -45° polarization conversion array. The two arrays have the same geometry; the -45° polarization conversion array is obtained by rotating the +45° polarization conversion array by 90° around the array's center of symmetry. Two +45° polarization conversion arrays and two -45° polarization conversion arrays are arranged in a grid pattern, with arrays of the same type placed diagonally.

7. A broadband low RCS compact circularly polarized antenna based on polarization conversion technology according to claim 6, characterized in that, Both the first dielectric substrate (2) and the second dielectric substrate (4) are made of F4B material with a dielectric constant of 2.

65.

8. A broadband low RCS compact circularly polarized antenna based on polarization conversion technology according to claim 7, characterized in that, The metal ground plane (3) is located between the first dielectric substrate (2) and the second dielectric substrate (4), and there are slits as radiation gaps at the positions of the patch units that act as antennas for the corresponding circularly polarized array antenna.

9. A broadband low RCS compact circularly polarized antenna based on polarization conversion technology according to claim 8, characterized in that, The power supply network (5) includes a 50Ω characteristic impedance microstrip line, a 70Ω characteristic impedance microstrip line, and three 100Ω resistors.

10. A broadband low RCS compact circularly polarized antenna based on polarization conversion technology according to claim 9, characterized in that, The 50Ω characteristic impedance microstrip line, the 70Ω characteristic impedance microstrip line and the three 100Ω resistors together form three Wilkinson power dividers, which constitute a two-stage power divider network and split one input signal into four signals with a phase difference of 90° in sequence through a phase shifter. Each of the four signals, which are 90° out of phase, is equipped with a T-shaped power divider at its end. The signal is then split into two equal-phase signals and distributed to each antenna element in the circularly polarized array antenna through a feed network.

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