A tightly coupled antenna array based on polarization conversion parasitic elements

Abstract

The present invention discloses a tightly coupled antenna array based on polarization conversion parasitic units, comprising an antenna radiation layer, a dielectric support layer (3), an absorbing layer (4) and a carrier platform metal surface (5) arranged in sequence from top to bottom; the antenna radiation layer comprises a plurality of antenna radiation units (1) constituting a two-dimensional uniform plane array, and the antenna radiation units (1) are provided with array gaps when constituting the two-dimensional uniform plane array, wherein the array gaps are loaded with polarization conversion parasitic units (2). The present invention performs same-layer embedded loading on the radiator of the tightly coupled antenna array, thereby solving the problems of scattering suppression and the difficulty in compatibility of array gain and physical size in the design process of a low-scattering tightly coupled array.

Description

Technical Field

[0001] The invention belongs to the field of antennas, and in particular relates to a tightly coupled antenna array based on polarization conversion parasitic units. Background Art

[0002] Radiation scattering suppression of array antennas is an important research direction in the field of modern antenna technology. As a key component for signal transmission and reception in communication radar systems, array antennas are one of the conventional strong scattering sources of carrier platforms. How to suppress the scattering amplitude and scattering peak value while transmitting and receiving electromagnetic wave signals normally is an important technical direction in the field of antenna design.

[0003] The tightly coupled antenna array is an array antenna with ultra-wideband, wide-angle scanning, and low profile characteristics. In recent years, it has been widely used in the field of ultra-wideband antennas. At the same time, the tightly coupled array of small-pitch periodic arrays has a certain frequency cutoff characteristic, which can suppress the electromagnetic scattering in the antenna structure to a certain extent; in addition, the small-pitch array arrangement has a decisive role in the suppression of the scattering grating lobe of the array, so the tightly coupled array is also an important means to achieve the scattering suppression of the antenna array. However, whether it is the effect of the frequency cutoff characteristic or the suppression of the scattering grating lobe of high-frequency electromagnetic waves, it is required to further reduce the array spacing, which will lead to a decrease in the gain of the antenna array and has certain limitations.

[0004] Polarization conversion material is an artificial electromagnetic material that can suppress the polarization characteristics of electromagnetic wave echoes. Since polarization conversion materials can achieve polarization mismatch between incident electromagnetic waves and reflected electromagnetic waves, the scattering amplitude of the target can be effectively suppressed. In order to achieve better polarization conversion characteristics, polarization conversion materials require a certain spatial size scale and have restrictions on the incoming direction of electromagnetic waves. A common application is for unit antennas. Loading polarization conversion materials on the periphery of the antenna unit aperture brings about scale effects. This idea achieves scattering suppression at the expense of increasing the aperture of the antenna array. Another application scenario is to design the polarization conversion material and the antenna radiation layer in layers. The polarization conversion material covers the upper layer of the antenna or is loaded on the antenna floor. It is one of the means of tightly coupled antenna scattering suppression, but it also sacrifices the antenna's profile height.

[0005] In summary, among the conventional scattering suppression methods of tightly coupled arrays, the method of suppressing scattering using frequency-selective cutoff characteristics relies heavily on small-period array spacing. To achieve better scattering suppression effects, the array spacing must be further reduced, which will result in a smaller equivalent aperture of the antenna array and a decrease in gain, which has certain limitations. The method of using layered loading of polarization conversion parasitic units will result in an antenna profile that is too high or an enlarged aperture, which is not conducive to the integration and low-profile of the antenna array and has low machinability. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a tightly coupled antenna array based on polarization conversion parasitic units, which performs same-layer embedded loading on the radiator of the tightly coupled antenna array, thereby solving the problems of scattering suppression and compatibility of array gain and physical size in the design process of low-scattering tightly coupled arrays.

[0007] The object of the present invention is achieved through the following technical solutions: A tightly coupled antenna array based on polarization conversion parasitic units, comprising an antenna radiation layer, a dielectric support layer, an absorbing layer and a carrier platform metal surface arranged in sequence from top to bottom;

[0008] The antenna radiation layer comprises a plurality of antenna radiation units constituting a two-dimensional uniform plane array, and array gaps are reserved when the antenna radiation units constitute the two-dimensional uniform plane array, and polarization conversion parasitic units are loaded in the array gaps.

[0009] The beneficial effects of the present invention are as follows: the present invention performs same-layer embedded loading on the radiator of the tightly coupled antenna array, thereby solving the problems of scattering suppression and difficulty in compatibility of array gain and physical size in the design process of the low-scattering tightly coupled array. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a schematic diagram of a tightly coupled antenna array after a polarization conversion parasitic unit is loaded in the present invention;

[0011] Figure 2 A schematic diagram of the antenna radiation unit and array used in the present invention;

[0012] Figure 3 This is a schematic diagram of loading the polarization conversion parasitic unit proposed by the present invention;

[0013] Figure 4 This is a schematic diagram of the simulation results of the frequency cutoff characteristics after polarization conversion parasitic loading;

[0014] Figure 5 This is a schematic diagram of the simulation results of polarization conversion rate after polarization conversion parasitic loading;

[0015] Figure 6 This is a schematic diagram of the simulation results of polarization conversion rate at large angle of incidence;

[0016] Figure 7 This is a schematic diagram of the simulation results of the scattering pattern;

[0017] Figure 8 This is a schematic diagram of the simulation results of the vertical polarization pattern;

[0018] Fig. 9 This is a schematic diagram of the simulation results of the horizontal polarization pattern;

[0019] Fig.10A partial schematic diagram of an antenna array loaded with polarization conversion parasitic elements;

[0020] Fig.11 Schematic diagram of a tightly coupled array loaded with polarization conversion parasitic units;

[0021] Fig.12 Schematic diagram of the feeding structure of a tightly coupled antenna array based on polarization conversion parasitic units;

[0022] In the figure, 1-antenna radiation unit, 2-polarization conversion parasitic unit, 3-dielectric support layer, 4-absorbing layer, 5-carrier platform metal surface, 6-gradient microstrip double line. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following.

[0024] like Figure 1 As shown, a tightly coupled antenna array based on polarization conversion parasitic units is characterized by comprising an antenna radiation layer, a dielectric support layer 3, an absorbing layer 4 and a carrier platform metal surface 5 arranged in sequence from top to bottom;

[0025] The antenna radiation layer includes a plurality of antenna radiation units 1 forming a two-dimensional uniform plane array, and the antenna radiation units 1 reserve array gaps when forming the two-dimensional uniform plane array, and the array gaps are loaded with polarization conversion parasitic units 2.

[0026] In the embodiment of the present application, the antenna radiation unit 1 is a printed circuit radiation patch, and its form includes but is not limited to a planar periodic structure composed of rectangular, diamond, circular and other patterns. The polarization conversion parasitic unit 2 is embedded in the array gap of the antenna radiation unit 1, and belongs to the same layer of printed circuit as the antenna radiation unit 1. The dielectric support layer 3 is placed under the antenna radiation unit 1 and the polarization conversion parasitic unit 2 printed circuit, and is connected to the absorbing layer 4, and the absorbing layer 4 is located between the dielectric support layer 3 and the carrier platform metal surface 5.

[0027] The structure of the antenna radiation unit 1 shown should be centrally symmetrical about its geometric center, and can be rectangular, square, rhombus (quasi-rhombus), circular, etc. Figure 2 As shown, Figure 2 (a) Figure 2 (b) Figure 2 (c) The radiation units are square, rhombus-like, and circular, respectively. The arrangement of the radiation units should be a two-dimensional uniform plane array. The period of the antenna radiation unit (1) in the two-dimensional uniform plane array is D. The maximum outer contour size P of the antenna radiation unit 1 in the 45° axis (i.e., B axis) should be less than This leaves enough space for loading the polarization conversion parasitic unit 2 .

[0028] The polarization conversion parasitic unit 2 is embedded in the antenna radiation unit 1. Figure 1 As shown, the outer contour radius r of the regular octagonal polarization conversion parasitic unit 2 should be less than The polarization conversion parasitic unit 2 can be embedded in the array gap of the antenna radiation unit 1, and the array spacing is the same as the array spacing D of the antenna radiation unit 1, and is not electrically connected to the antenna radiation unit 1. Figure 3 For example, the incident electromagnetic wave E in The polarization direction is horizontal polarization, and can be decomposed into E on the A axis and B axis. in1 、E in2 That is, E in =E in1 +E in2 , similarly, the reflected electromagnetic wave E re It can also be decomposed into E on the A axis and B axis re1 、E re2 That is, E in =E re1 +re. Since the polarization conversion parasitic unit 2 is designed as a central symmetrical structure (the center of symmetry is the intersection of the A and B axes, that is, the geometric center of the unit), the reflected electromagnetic wave E re The phase difference of the reflection generated in the A-axis and B-axis directions will be different. When the A-axis is reflected, the phase difference Φ(A)=Φ(E re1 )-Φ(E in1 ) and the B axis reflect the phase difference Φ(B)=Φ(E re2 )-Φ(E in2 ) When the relationship Φ(B)-Φ(A)=±180°, the reflected electromagnetic wave E re The direction of the incident electromagnetic wave E in The directions of the polarizations are orthogonal, that is, the transformation from horizontal polarization to vertical polarization is realized.

[0029] The antenna radiation unit 1 and the polarization conversion parasitic unit 2 should be designed based on a printed circuit;

[0030] The polarization conversion parasitic unit 2 is a printed circuit on the same layer as the antenna radiation unit 1, and the period d of the polarization conversion parasitic unit 2 and the period D of the antenna radiation unit 1 satisfy The polarization conversion parasitic unit 2 is embedded in the gap of the antenna radiation unit 1 so that the periodicity of the original array structure is not destroyed after loading;

[0031] The period D of the antenna radiation unit 1 refers to the distance between the center points of two adjacent antenna radiation units 1;

[0032] The period d of the polarization conversion parasitic unit 2 refers to the distance between the center points of two adjacent polarization conversion parasitic units 2 .

[0033] The curvature of the antenna radiation unit 1, the polarization conversion parasitic unit 2, the dielectric support material 3, and the absorbing material 4 should not differ too much from the curvature of the carrier platform metal surface 5;

[0034] The antenna radiation unit 1 is allowed to have a hole in the middle of the unit or in the unit gap to meet the installation of the feeding structure of the antenna unit, but the consistency of the unit hole opening should be ensured and the original cycle should not be destroyed. After the hole is opened, the hole position where the feeding structure is not installed should be loaded with a matching resistor of the same impedance.

[0035] In the embodiment of the present application, the polarization conversion parasitic unit 2 includes two symmetrically arranged trapezoidal resonant rings located in the same plane, the bottom sides of the two trapezoidal resonant rings are connected, and the maximum outer contour of the entire polarization conversion parasitic unit 2 is a regular octagonal structure; each trapezoidal resonant ring has an opening, and the openings of the two trapezoidal resonant rings are symmetrical. This structure is insensitive to the polarization direction of the incident electromagnetic wave, and can still maintain good polarization conversion characteristics when the electromagnetic wave is incident at a large angle;

[0036] Furthermore: the dielectric support material 3 should be a low-loss material with a dielectric constant not greater than 1.1;

[0037] Furthermore: the absorbing material 4 should have a wide-band absorbing function, including but not limited to common ferromagnetic materials, absorbing honeycombs, absorbing rubber and other electromagnetic materials with broadband absorbing function;

[0038] Preferably, the polarization conversion parasitic units 2 can form sub-arrays in a scale of at least 3×3 during loading, and the polarization conversion parasitic units in adjacent sub-arrays form an axial angle of 90° (axis A);

[0039] As a preference: the polarization conversion parasitic unit 2 should leave a certain gap from the antenna radiation unit, and the gap size should not be less than one twentieth of the antenna high-frequency working wavelength;

[0040] Preferably, the maximum outer contours of the combined dimensions of the antenna radiation unit 1 and the polarization conversion parasitic unit 2 should be as consistent as possible to achieve better scattering suppression within the antenna working band.

[0041] Due to the adoption of the above-mentioned technical solution, the present invention effectively improves the cutoff characteristics of the tightly coupled array radiator in the high frequency band without reducing the array spacing or increasing the overall cross-section of the structure, and suppresses the scattered clutter generated by high-frequency incoming waves in the antenna structure. Taking the simulation results of this implementation case as an example, the tightly coupled array exhibits high-pass characteristics at high frequencies before the polarization conversion parasitic unit is loaded; and through the loading of the polarization conversion parasitic unit, its cutoff characteristics are effectively improved. The present invention is conducive to suppressing the scattering generated by the antenna cavity structure. The simulation results of the frequency cutoff characteristics after the polarization conversion parasitic is loaded are shown as follows. Figure 4 As shown;

[0042] The polarization conversion parasitic unit of the present invention is loaded on the antenna array, and the array has good polarization conversion characteristics, such as Figures 5-6 As shown in the figure, the normal polarization conversion rate in the range of 11.3 to 20.6 GHz reaches more than 60%, and the polarization conversion rate can still be maintained at more than 40% within the ±45° airspace. From the simulation results of the scattering pattern, that is, Figure 7 It can be seen that after adopting the measures of the present invention, the overall scattering pattern of the antenna array has been significantly reduced, and the scattering mean value in the large-angle airspace of -45° to +45° has been reduced by 6dBm. 2 above.

[0043] The electrical performance simulation results of the antenna array are shown in Figures 8-9 :

[0044] Figure 8 It is a schematic diagram of the simulation results of vertical polarization patterns at different frequencies (2000MHZ, 6000MHZ, 12000MHZ, 16000MHZ); among them, Figure 8 (a) The corresponding frequency is 2000MHZ, Figure 8 (b) The corresponding frequency is 6000MHZ, Figure 8 (c) The corresponding frequency is 12000MHZ, Figure 8 (d) The corresponding frequency is 16000MHZ;

[0045] Fig. 9 It is a schematic diagram of the simulation results of horizontal polarization patterns at different frequencies (2000MHZ, 6000MHZ, 12000MHZ, 16000MHZ); among them, Fig. 9 (a) The corresponding frequency is 2000MHZ, Fig. 9 (b) The corresponding frequency is 6000MHZ, Fig. 9 (c) The corresponding frequency is 12000MHZ, Fig. 9 (d) The corresponding frequency is 16000MHZ;

[0046] Comparing the radiation characteristics of the antenna array before and after the polarization conversion parasitic unit is loaded, it can be seen that after the polarization conversion parasitic unit is loaded, the main electrical performance parameters of the antenna array are not significantly affected, and still maintain good radiation characteristics. The present invention does not affect the radiation performance of the antenna while suppressing scattering.

[0047] The polarization conversion parasitic unit used in the present invention is printed on the same layer as the antenna radiation unit, which does not change the original structure of the antenna, is easy to process, and has high manufacturability. The present invention does not increase the original profile height of the antenna array, does not increase the original aperture size of the antenna array, and can be widely used in scattering suppression of tightly coupled antenna arrays;

[0048] In the embodiments of the present application, Fig.10 A partial schematic diagram of an antenna array loaded with polarization conversion parasitic elements ( Fig.10 (a) is the front view, Fig.10 (b) is a side view), which consists of an antenna radiating unit 1, a polarization conversion parasitic unit 2, a dielectric support structure 3, and an absorbing layer 4. The geometric size of the polarization conversion parasitic unit 2 is smaller than the periodic spacing of the antenna radiating unit 1 in the antenna array, and is embedded in the gap of the antenna radiating unit 1. The antenna radiating unit 1 and the polarization conversion parasitic unit 2 are printed on the same layer on a flexible dielectric substrate. In an embodiment of the present application, the unit structure can also be simulated in HFSS or CST according to periodic boundary conditions to obtain the operating frequency band, polarization conversion rate and other characteristics of the structure, and the simulation results can be optimized by adjusting the size parameters of the polarization conversion parasitic unit 2.

[0049] The polarization conversion parasitic unit is embedded in the tightly coupled array. In this case, a rectangular antenna radiation unit 1 is selected to form a tightly coupled array. The polarization conversion parasitic unit is embedded in the tightly coupled array in a group of 9 elements in a 3×3 subarray. The polarization conversion parasitic units in adjacent subarrays are axially at an angle of 90° to each other. Fig.11 As shown, Fig.11 (a) is a tightly coupled array before loading polarization conversion parasitic units. Fig.11 (b) is a tightly coupled array after polarization conversion parasitic units are loaded in the form of 3×3 subarrays;

[0050] According to the actual use requirements of the antenna array, determine the number of feeding channels to be used and complete the detailed design of the tightly coupled antenna array. The feeding method is not limited to two-wire, coaxial, etc. Fig.12 As shown, in this case, a microstrip double line is selected to complete the feeding structure design. The gradient microstrip double line 6 based on the printed circuit passes through the dielectric support structure 3 and the absorbing layer 4. One end of the microstrip double line 6 is welded to the antenna radiating unit that needs to be fed, and the other end is welded to the insulator; the antenna radiating unit that does not need to be fed should be installed with a matching resistor of the same impedance to replace the feeding structure.

[0051] The modeling of the tightly coupled antenna array after loading the polarization conversion parasitic unit is completed in HFSS, and the main electrical performance indicators of the antenna array, such as the standing wave and radiation pattern, are obtained by simulation calculation. The antenna array model is imported into FEKO, and the far-field incoming wave is set according to the polarization mode, detection frequency and observation angle of the radar, and the scattering radiation pattern of the antenna array is simulated. The above steps are repeated for iterative optimization to obtain the optimal balance between electrical performance and stealth performance.

Claims

1. A tightly coupled antenna array based on polarization conversion parasitic units, characterized in that: It comprises an antenna radiation layer, a dielectric support layer (3), an absorbing layer (4) and a carrier platform metal surface (5) which are arranged in sequence from top to bottom; The antenna radiation layer comprises a plurality of antenna radiation units (1) forming a two-dimensional uniform plane array, and the antenna radiation units (1) are provided with array gaps when forming the two-dimensional uniform plane array, wherein the array gaps are loaded with polarization conversion parasitic units (2); The polarization conversion parasitic unit (2) is a printed circuit on the same layer as the antenna radiation unit (1), and the period d of the polarization conversion parasitic unit (2) and the period D of the antenna radiation unit (1) satisfy N=1, 2, ..., n, the polarization conversion parasitic unit (2) is embedded in the gap of the antenna radiation unit (1) so that the periodicity of the original array structure is not destroyed after loading; The period D of the antenna radiation unit (1) refers to the distance between the center points of two adjacent antenna radiation units (1); The period d of the polarization conversion parasitic unit (2) refers to the distance between the center points of two adjacent polarization conversion parasitic units (2); The polarization conversion parasitic unit (2) comprises two symmetrically arranged trapezoidal resonant rings, the bottom sides of the two trapezoidal resonant rings are connected, so that the maximum outer contour of the entire polarization conversion parasitic unit (2) is a regular octagonal structure; each trapezoidal resonant ring has an opening, and the openings of the two trapezoidal resonant rings are symmetrical.

2. The tightly coupled antenna array based on polarization conversion parasitic units according to claim 1, characterized in that: The antenna radiation unit (1) is a printed circuit radiation patch, and the antenna radiation unit (1) forms a two-dimensional uniform plane array with a plane periodic structure.

3. The tightly coupled antenna array based on polarization conversion parasitic units according to claim 1, characterized in that: The shape of the antenna radiation unit (1) is rectangular, rhombus or circular.

4. The tightly coupled antenna array based on polarization conversion parasitic units according to claim 1, characterized in that: The dielectric support layer (3) is made of a low-loss material with a dielectric constant not greater than 1.

1.

5. The tightly coupled antenna array based on polarization conversion parasitic units according to claim 1, characterized in that: The wave absorbing layer (4) is made of a wave absorbing material with a wide-band wave absorbing function, including a combination of one or more of a ferromagnetic body, a wave absorbing honeycomb, and a wave absorbing rubber.

6. The tightly coupled antenna array based on polarization conversion parasitic units according to claim 1, characterized in that: The polarization conversion parasitic unit (2) leaves a gap from the antenna radiation unit, and the size of the gap is not less than one twentieth of the high-frequency working wavelength of the antenna.

7. The tightly coupled antenna array based on polarization conversion parasitic units according to claim 1, characterized in that: The rightward direction of the line connecting the antenna radiation units (1) in the same row of the two-dimensional uniform plane array is the X-axis direction, and the upward direction of the line connecting the antenna radiation units (1) in the same column is the Y-axis direction; The period of the antenna radiation unit (1) in the two-dimensional uniform plane array is D, and the maximum outer contour size P of the antenna radiation unit (1) in the direction forming an angle of 45° with the X axis is less than It is used to reserve enough space for loading the polarization conversion parasitic unit (2).

8. The tightly coupled antenna array based on polarization conversion parasitic units according to claim 7, characterized in that: The outer contour radius r of the polarization conversion parasitic unit (2) is less than

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