Two-dimensional sidelobe suppression and axial ratio optimization method applied to circularly polarized antenna

Abstract

The invention discloses a two-dimensional sidelobe suppression and axial ratio optimization method applied to a circularly polarized antenna, and belongs to the technical field of wireless communication. According to the method provided by the invention, a circularly polarized antenna array is realized by adopting a two-dimensional regulation and control mechanism mode, and the two-dimensional regulation and control mechanism mode comprises a feed phase dimension and a chiral inversion dimension. According to the method, two-dimensional low-sidelobe forming can be achieved by optimizing the position distribution of the 180-degree original arrays, complex and tedious feed network design is avoided, the antenna performance is guaranteed, meanwhile, the antenna structure is simplified, and the manufacturing cost is reduced; the axial ratio can be optimized by optimizing the positions of the 0-degree chiral arrays and the 180-degree chiral arrays, global parameter adjustment is not needed in the optimization process, continuous parameter adjustment and optimization of a large-scale array are avoided, the time cost is saved, and the design flexibility is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communications, and in particular relates to a dual-dimensional sidelobe suppression and axial ratio optimization method applied to a circularly polarized antenna. Background Art

[0002] Circularly polarized antennas are widely used in satellite communications, radar detection, 5G millimeter-wave communications, the Internet of Things, and other fields due to their advantages, such as reducing polarization mismatch losses and suppressing multipath interference. As wireless systems continue to place increasing demands on antenna performance, circularly polarized antennas must simultaneously meet low sidelobe level (SLL) and high axial ratio (AR). Low sidelobe levels reduce sidelobe interference and improve system anti-interference capabilities, while a low axial ratio ensures circular polarization purity and ensures stable signal transmission.

[0003] Existing circularly polarized antenna designs typically follow a progressive "element optimization-array expansion" process, where individual elements are periodically arranged based on their ideal axial ratio performance. However, this design process often faces two major bottlenecks in engineering practice: first, mutual coupling between elements, which leads to a decrease in polarization purity and deterioration in the array's axial ratio performance; second, insufficient sidelobe suppression in the array pattern under uniform excitation, making it difficult to meet the requirements of high-security scenarios. Therefore, to simultaneously achieve low sidelobe and improved axial ratio, separate optimizations for these two objectives are necessary. Improving axial ratio often requires continuous parameter optimization and full-wave simulation of large-scale arrays. This requires long simulation cycles, and if the element parameters have many degrees of freedom, finding a balance between these parameters and axial ratio is difficult. To achieve low sidelobe, precise amplitude and phase control of the antenna feed structure is often required. For example, Taylor or Chebyshev distributions can be used to adjust the excitation amplitude of the element antenna to optimize the radiation pattern, or advanced algorithms can be used to obtain the optimal phase configuration for low sidelobe. However, both amplitude modulation and phase modulation are difficult to implement for large feed networks. Summary of the Invention

[0004] The object of the present invention is to overcome the above-mentioned defects of the prior art and provide a dual-dimensional sidelobe suppression and axial ratio optimization method for circularly polarized antennas.

[0005] The technical problem proposed by the present invention is solved as follows:

[0006] A two-dimensional sidelobe suppression and axial ratio optimization method for circularly polarized antennas is implemented using a two-dimensional control mechanism for the circularly polarized antenna array, including a feed phase dimension and a chirality inversion dimension. In the feed phase dimension, the feed phase of some unit antennas is reversed so that the feed phase of the unit antenna is in two states, 0° and 180°. In the chirality inversion dimension, the chirality of some unit antennas is reversed so that the unit antenna forms two states, namely, an original array and a chiral array. By optimizing the distribution positions of the reversed feed phase unit antennas and the chiral array, two-dimensional low sidelobe shaping and improved axial ratio performance of the circularly polarized array antenna are achieved.

[0007] Furthermore, based on the two-dimensional control mechanism, each unit antenna in the circularly polarized antenna array is finally configured into four states; the unit antenna without feeding phase inversion and chirality inversion is in the first state, which is a 0° original array; the unit antenna with only feeding phase inversion is in the second state, which is a 180° original array; the unit antenna with only chirality inversion is in the third state, which is a 0° chiral array; the unit antenna with both feeding phase inversion and chirality inversion is in the fourth state, which is a 180° chiral array; optimizing the position distribution of the 0° original array, 180° original array, 0° chiral array, and 180° chiral array can achieve two-dimensional low sidelobe shaping and axial ratio performance improvement of the circularly polarized antenna.

[0008] Furthermore, an optimization algorithm is used to optimize the position distribution of the 0° primary array, 180° primary array, 0° chiral array, and 180° chiral array. In the multi-objective genetic algorithm, the state of each unit antenna is used as the optimization variable, and the gain, sidelobe, and axial ratio of the circularly polarized antenna array are used as optimization targets.

[0009] Furthermore, the scale of the circularly polarized antenna array is 16×16.

[0010] Furthermore, the feeding network of the circularly polarized antenna array is a co-feed network, and each unit antenna is fed with equal power.

[0011] Furthermore, the feed phase of some antenna units of the circularly polarized antenna array is reversed. The radiation field of the unit antenna with reversed feed phase in the sidelobe direction forms destructive interference with the radiation field of other unit antennas, thereby reducing the synthetic field strength in the sidelobe direction and reducing the sidelobe level; the distribution position of the unit antenna with reversed feed phase is determined by an optimization algorithm to achieve sidelobe optimization of the circularly polarized array antenna.

[0012] Furthermore, the chirality of some of the topologically symmetrically distributed unit antennas in the circularly polarized antenna array is reversed to reduce the gap between the major axis and the minor axis, thereby improving the axial ratio.

[0013] The electric field of the circularly polarized array antenna is decomposed into two orthogonal directions, with equal electric field amplitudes and a 90° phase difference, as shown in equation (1):

[0014]

[0015] in, and are right-handed electric field and left-handed electric field, respectively. and denote the unit vectors in the horizontal and vertical directions respectively, E0 is the electric field amplitude, and j is the sign of the imaginary part;

[0016] During the process of chirality reversal and rotational control of the unit antenna, the phase difference of the electric field component in one direction is 180°; if there is a 180° phase lag on the short axis, the unit antenna at this position should be in a 180° chirality array state after chirality reversal; if there is a 180° phase lag on the long axis, the unit antenna at this position should be in a 0° chirality array state after chirality reversal.

[0017] Furthermore, for right-hand circularly polarized array antennas, the chirality of some units is reversed to 0° left-hand arrays to improve the axial ratio;

[0018] Electric field of right-hand circularly polarized array antenna Decomposed into two orthogonal axes, the short axis and the long axis, the electric field component is expressed by formula (2). The axial ratio AR of the right-hand circularly polarized array antenna is RHCP is approximately 3, which can be expressed by formula (3):

[0019]

[0020] in, and represent the amplitudes of the right-handed electric field components of the right-handed circularly polarized array in the horizontal and vertical directions, respectively;

[0021] In the process of right-hand circularly polarized unit antenna becoming left-hand circularly polarized unit antenna, the phase of the electric field component on the long axis is delayed, so the electric field of the left-handed array after the chirality reversal is Expressed by formula (4):

[0022]

[0023] in, and They represent the amplitudes of the left-handed electric field components in the horizontal and vertical directions of the left-handed array after chirality reversal;

[0024] After the left-handed array after chirality inversion is superimposed on the right-handed circularly polarized array antenna, the total electric field vector Given by formula (5):

[0025]

[0026] in, is the electric field vector of the right-handed array replaced by the left-handed array after chirality reversal, and Respectively represent the amplitude of the right-handed electric field component of the replaced right-handed array in the horizontal and vertical directions; because the chirality reversal does not change the axis ratio,

[0027] After the left-handed array after chirality inversion is superimposed on the right-handed circularly polarized array antenna, the array axis ratio AR ALL Given by formula (6):

[0028]

[0029] It can be seen from the above formula that the axial ratio is improved after the left-handed array after chirality inversion is superimposed on the original right-handed circularly polarized array antenna.

[0030] The beneficial effects of the present invention are:

[0031] (1) The method of the present invention can achieve two-dimensional low sidelobe shaping by optimizing the position distribution of the 180° primary array, avoiding the complex and tedious feeding network design, simplifying the antenna structure while ensuring the antenna performance, and reducing the manufacturing cost.

[0032] (2) The method described in the present invention can achieve the optimization of the axial ratio by optimizing the positions of the 0° chiral array and the 180° chiral array, and the optimization process does not require global parameter adjustment, avoiding the continuous parameter adjustment and optimization of large-scale arrays, saving time and cost and significantly improving the design flexibility.

[0033] (3) The method described in the present invention is applicable to the design of large-scale circularly polarized antennas. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the three-dimensional structure of the antenna array in the method described in the embodiment;

[0035] Figure 2 A top view of the antenna array in the method of the embodiment;

[0036] Figure 3 A distribution diagram of array states of the antenna array in the method described in the embodiment;

[0037] Figure 4 Schematic diagram of the structure of the first coupling slot layer of the antenna array in the method described in the embodiment;

[0038] Figure 5A top view of the second coupling slot layer, the third dielectric substrate, and the metal floor of the antenna array in the method described in the embodiment;

[0039] Figure 6 is the directional pattern of the antenna array in the method described in the embodiment, wherein (a) is the xoz plane and (b) is the yoz plane;

[0040] Figure 7 Graph showing the axial ratio of the antenna array and the original antenna array as a function of frequency in the method described in the embodiment. DETAILED DESCRIPTION

[0041] The present invention will be further described below with reference to the accompanying drawings and examples.

[0042] This embodiment provides a two-dimensional sidelobe suppression and axial ratio optimization method for circularly polarized antennas, which is applicable to circularly polarized antenna design in the following fields: satellite communications, radar systems, and 5G millimeter wave communications. The circularly polarized antenna array is implemented using a two-dimensional control mechanism, including the feed phase dimension and the chirality inversion dimension. In the feed phase dimension, the feed phase of some unit antennas is reversed, so that the phase difference between the feed phase of the unit antenna and the original unit antenna is 0° and 180°. In the chirality inversion dimension, the chirality of some unit antennas is reversed, so that the unit antenna forms two states: the original array and the chiral array. By optimizing the distribution position of the reversed feed phase unit antennas and the chiral array, the two-dimensional low sidelobe shaping and axial ratio performance of the circularly polarized array antenna are achieved, ensuring the purity of circular polarization.

[0043] Based on the two-dimensional control mechanism, each unit antenna in the circularly polarized antenna array is finally configured into four states: the unit antenna without feeding phase inversion and chirality inversion is in the first state, which is a 0° original array; the unit antenna with only feeding phase inversion is in the second state, which is a 180° original array; the unit antenna with only chirality inversion is in the third state, which is a 0° chiral array; the unit antenna with both feeding phase inversion and chirality inversion is in the fourth state, which is a 180° chiral array; a multi-objective genetic optimization algorithm is used to optimize the position distribution of the 0° original array, 180° original array, 0° chiral array, and 180° chiral array, with the state of each unit antenna as the optimization variable and the gain, sidelobe, and axial ratio of the circularly polarized antenna array as the optimization targets, thereby achieving two-dimensional low sidelobe shaping and axial ratio performance improvement of the circularly polarized antenna.

[0044] (1) Feed phase reversal shaping

[0045] Without making complex changes to the feeding network design of the circularly polarized antenna array, the feeding phase of some unit antennas can be reversed to achieve a 0° / 180° radiation phase. The radiation field of the phase-reversed unit antenna in the sidelobe direction forms destructive interference with the radiation field of other unit antennas, thereby reducing the composite field strength in this sidelobe direction and reducing the sidelobe level. The distribution position of the unit antennas with reversed feeding phase is determined by an optimization algorithm to achieve sidelobe optimization on both sides of the circularly polarized array antenna.

[0046] (2) Control of chirality reversal

[0047] Based on the principle of rotational reversal compensation, the axial ratio of the circularly polarized array antenna is optimized by reconstructing the polarization characteristic distribution of the unit antenna. The chirality reversal rotation control is performed on some of the topologically symmetrical unit antennas to narrow the gap between the major axis and the minor axis, thereby improving the axial ratio. For a circularly polarized array antenna, its electric field can be decomposed into two orthogonal directions with equal electric field amplitudes and a phase difference of 90°, as shown in Equation (1):

[0048]

[0049] in, and are right-handed electric field and left-handed electric field, respectively. and Represent the unit vectors in the horizontal and vertical directions respectively, E0 is the electric field amplitude, and j is the sign of the imaginary part.

[0050] It can be seen that during the process of chirality inversion rotation direction control, the phase difference of the electric field component in one direction is 180°; therefore, if there is a 180° phase lag on the short axis, the unit antenna at this position should be in a 180° chiral array state after chirality inversion; if there is a 180° phase lag on the long axis, the unit antenna at this position should be in a 0° chiral array state after chirality inversion.

[0051] Specifically, the principle of this method is explained by taking the example of performing chirality reversal on some elements in a right-hand circularly polarized array antenna to become a 0° left-hand array to improve the axial ratio.

[0052] For a right-hand circularly polarized array antenna, its electric field Decomposed into two orthogonal axes, the short axis x and the long axis y, the electric field components can be expressed by formula (2). Due to its poor axial ratio, the axial ratio AR RHCP is approximately equal to 3, which can be expressed by formula (3):

[0053]

[0054] in, and represent the amplitudes of the right-handed electric field components of the right-handed circularly polarized array in the horizontal and vertical directions, respectively.

[0055] In the process of right-hand circularly polarized RHCP unit becoming left-hand circularly polarized LHCP unit, it is impossible to determine whether the phase lag of the electric field component on the long axis or the phase lag of the electric field component on the short axis is the same. Here, it is assumed that the phase lag of the electric field component on the long axis is the same, so the electric field of the left-handed array after the chirality reversal is It can be expressed by formula (4):

[0056]

[0057] in, and They represent the amplitudes of the left-handed electric field components in the horizontal and vertical directions of the left-handed array after chirality reversal.

[0058] After the left-handed array after chirality inversion is superimposed on the right-handed circularly polarized array antenna, the total electric field vector Given by formula (5):

[0059]

[0060] in, is the electric field vector of the right-handed array replaced by the left-handed array after chirality reversal, and They represent the amplitude of the right-handed electric field component of the replaced right-handed array in the horizontal and vertical directions respectively. Since the chirality inversion does not change the axis ratio,

[0061] After the left-handed array after chirality inversion is superimposed on the right-handed circularly polarized array antenna, the array axis ratio AR ALL Given by formula (6):

[0062]

[0063] It can be seen that after the left-handed array after chirality reversal is superimposed on the original right-handed circularly polarized array antenna, the gap between the short axis and the long axis is reduced and the axial ratio is improved.

[0064] In this embodiment, the scale of the right-hand circularly polarized array antenna is 16×16, the feeding network is a common feeding network, and the power feeding between each unit is equal. The right-hand circularly polarized array antenna is designed using the method described in this embodiment. The three-dimensional structure diagram of the antenna array after algorithm optimization is shown as follows: Figure 1 As shown, the top view is Figure 2 As shown, the array state distribution diagram is as follows Figure 3 As shown, state 1 represents the 0° primary array 11 , state 2 represents the 180° primary array 12 , state 3 represents the 0° chiral array 13 , and state 4 represents the 180° chiral array 14 .

[0065] The right-handed circularly polarized array antenna in this embodiment utilizes a stacked, slot-coupled, dipole antenna array. The antenna comprises, from top to bottom, a radiating patch layer, a first dielectric substrate, a first coupling slot layer, a second dielectric substrate, a second coupling slot layer, a third dielectric substrate, and a metal floor. The coupling slot layer is implemented using a SIW. Signals are input through a waveguide port on the metal floor. Signals are then coupled through a 1-to-64 SIW power splitter in the third dielectric substrate and the second coupling slot layer to several 1-to-4 SIW power splitters in the second dielectric substrate. Signals are then coupled to the first dielectric substrate through the first coupling slot layer, and finally radiate into free space through the radiating patch layer. This embodiment operates in the 37-39 GHz frequency band, using a Taconic TLY-5 dielectric substrate.

[0066] The structural diagram of the first coupling gap layer is shown in FIG. Figure 4 As shown, each radiating patch is etched with a coupling slot 31 or a reverse slot 32 of the same size at its center. For the unit antenna corresponding to the 180° array, the coupling slot between its radiating patch and the first coupling slot layer is adjusted to the other side of the SIW based on the 0° array. For the unit antenna corresponding to the 0° chiral array, its radiating patch is mirrored at its original position based on the 0° array. For the unit antenna corresponding to the 180° chiral array, its radiating patch is mirrored at its original position based on the 180° array.

[0067] The top view of the second coupling gap layer, the third dielectric substrate and the metal floor is shown in FIG. Figure 5 As shown, coupling slots 51 of the same size are etched on the second coupling slot layer, and a waveguide opening 71 is etched on the metal floor.

[0068] The directional pattern of the 16×16 array (placed in the xoy plane) obtained by the dual-dimensional sidelobe suppression and axial ratio optimization method described in this embodiment is as follows: Figure 6 As shown, (a) is the xoz plane and (b) is the yoz plane. The sidelobe levels of the two planes are kept below -19dB on average.

[0069] The axial ratio variation curves of the 16×16 array and the direct array obtained by the dual-dimensional sidelobe suppression and axial ratio optimization method described in this embodiment are shown in FIG. Figure 7 As shown, for a center frequency of 38 GHz, the axial ratio of the direct array is 1.31 dB, which is reduced to 0.38 dB after applying the method; for the entire frequency band, the axial ratio range of the direct array is less than 2 dB, which is reduced to less than 1.4 dB after applying the method.

[0070] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to provide an exhaustive list of all embodiments. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the claims of the present invention.

Claims

1. A dual-dimensional sidelobe suppression and axial ratio optimization method for circularly polarized antennas, characterized in that: The circularly polarized antenna array is implemented using a two-dimensional control mechanism, including the feed phase dimension and the chirality inversion dimension. In the feed phase dimension, the feed phase of some unit antennas is reversed so that the feed phase of the unit antenna is in two states: 0° and 180°. In the chirality inversion dimension, the chirality of some unit antennas is reversed so that the unit antenna forms two states: the original array and the chiral array. By optimizing the distribution positions of the reversed feed phase unit antennas and the chiral array, the two-dimensional low sidelobe shaping and axial ratio performance improvement of the circularly polarized array antenna are achieved.

2. The dual-dimensional sidelobe suppression and axial ratio optimization method for circularly polarized antennas according to claim 1, wherein: Based on the two-dimensional control mechanism, each unit antenna in the circularly polarized antenna array is finally configured into four states: the unit antenna without feeding phase inversion and chirality inversion is in the first state, which is a 0° primary array; the unit antenna with only feeding phase inversion is in the second state, which is a 180° primary array; the unit antenna with only chirality inversion is in the third state, which is a 0° chiral array; the unit antenna with both feeding phase inversion and chirality inversion is in the fourth state, which is a 180° chiral array; optimizing the position distribution of the 0° primary array, 180° primary array, 0° chiral array, and 180° chiral array can achieve two-dimensional low sidelobe shaping of the circularly polarized antenna and improve the axial ratio performance.

3. The dual-dimensional sidelobe suppression and axial ratio optimization method for circularly polarized antennas according to claim 2, wherein: The optimization algorithm is used to optimize the position distribution of the 0° primary array, 180° primary array, 0° chiral array, and 180° chiral array. In the multi-objective genetic algorithm, the state of each unit antenna is used as the optimization variable, and the gain, sidelobe, and axial ratio of the circularly polarized antenna array are used as the optimization targets.

4. The dual-dimensional sidelobe suppression and axial ratio optimization method for circularly polarized antennas according to claim 1, wherein: The scale of the circularly polarized antenna array is 16×16.

5. The dual-dimensional sidelobe suppression and axial ratio optimization method for circularly polarized antennas according to claim 1, wherein: The feeding network of the circularly polarized antenna array is a common feeding network, and each unit antenna is fed with equal power.

6. The dual-dimensional sidelobe suppression and axial ratio optimization method for circularly polarized antennas according to claim 3, wherein: The feed phase of some antenna elements of the circularly polarized antenna array is reversed. The radiation field of the unit antenna with reversed feed phase in the sidelobe direction forms destructive interference with the radiation field of other unit antennas, thereby reducing the composite field strength in the sidelobe direction and the sidelobe level. The distribution position of the unit antenna with reversed feed phase is determined by an optimization algorithm to achieve sidelobe optimization of the circularly polarized array antenna.

7. The dual-dimensional sidelobe suppression and axial ratio optimization method for circularly polarized antennas according to claim 3, wherein: The chirality of some symmetrically distributed element antennas in the circularly polarized antenna array is reversed to reduce the gap between the major and minor axes, thereby improving the axial ratio. The electric field of the circularly polarized array antenna is decomposed into two orthogonal directions, with equal electric field amplitudes and a 90° phase difference, as shown in equation (1): in, and are right-handed electric field and left-handed electric field, respectively. and denote the unit vectors in the horizontal and vertical directions respectively, E0 is the electric field amplitude, and j is the sign of the imaginary part; During the process of chirality reversal and rotational control of the unit antenna, the phase difference of the electric field component in one direction is 180°; if there is a 180° phase lag on the short axis, the unit antenna at this position should be in a 180° chirality array state after chirality reversal; if there is a 180° phase lag on the long axis, the unit antenna at this position should be in a 0° chirality array state after chirality reversal.

8. The dual-dimensional sidelobe suppression and axial ratio optimization method for circularly polarized antennas according to claim 7, wherein: For right-hand circularly polarized array antennas, the chirality of some elements is reversed to 0° left-handed arrays to improve the axial ratio; Electric field of right-hand circularly polarized array antenna Decomposed into two orthogonal axes, the short axis and the long axis, the electric field component is expressed by formula (2). The axial ratio AR of the right-hand circularly polarized array antenna is RHCP is 3, which can be expressed by formula (3): in, and represent the amplitudes of the right-handed electric field components of the right-handed circularly polarized array in the horizontal and vertical directions respectively; In the process of right-hand circularly polarized unit antenna becoming left-hand circularly polarized unit antenna, the phase of the electric field component on the long axis is delayed, so the electric field of the left-handed array after the chirality reversal is Expressed by formula (4): in, and They represent the amplitudes of the left-handed electric field components in the horizontal and vertical directions of the left-handed array after chirality reversal; After the left-handed array after chirality inversion is superimposed on the right-handed circularly polarized array antenna, the total electric field vector Given by formula (5): in, is the electric field vector of the right-handed array replaced by the left-handed array after chirality reversal, and Respectively represent the amplitude of the right-handed electric field component of the replaced right-handed array in the horizontal and vertical directions; the chirality reversal does not change the axis ratio. After the left-handed array after chirality inversion is superimposed on the right-handed circularly polarized array antenna, the array axis ratio AR ALL Given by formula (6): It can be seen from the above formula that the axial ratio is improved after the left-handed array after chirality inversion is superimposed on the original right-handed circularly polarized array antenna.

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