A dual-dimension sidelobe suppression and axial ratio optimization method applied to circularly polarized antennas

Abstract

The application discloses a dual-dimension sidelobe suppression and axial ratio optimization method applied to a circularly polarized antenna and belongs to the technical field of wireless communication. The method is realized by adopting a dual-dimension regulation mechanism mode for the circularly polarized antenna array, including a feeding phase dimension and a chiral inversion dimension. The method can realize two-dimensional low sidelobe shaping by optimizing the position distribution of 180-degree original array elements, avoids complex and tedious feeding network design, simplifies the structure of the antenna while ensuring the performance of the antenna, and reduces the manufacturing cost. The axial ratio can be optimized by optimizing the positions of 0-degree chiral array elements and 180-degree chiral array elements, and the optimization process does not need global parameter adjustment, avoids constant parameter adjustment and optimization for a large-scale array, saves time cost, and significantly improves the flexibility of design.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, specifically relating to a two-dimensional sidelobe suppression and axial ratio optimization method for circularly polarized antennas. Background Technology

[0002] Circularly polarized antennas are widely used in satellite communications, radar detection, 5G millimeter-wave communications, and the Internet of Things (IoT) due to their advantages such as reducing polarization mismatch loss and suppressing multipath interference. As wireless systems increasingly demand higher antenna performance, circularly polarized antennas must simultaneously meet the requirements of low sidelobe level (SLL) and high axial ratio (AR): low sidelobes reduce sidelobe interference and improve the system's anti-interference capability; while a low axial ratio ensures circular polarization purity and guarantees signal transmission stability.

[0003] The design of existing circularly polarized antennas typically follows a progressive process of "element optimization - array expansion," which involves periodically arranging elements based on their ideal axial ratio performance. However, this design process often faces two major coupling bottlenecks in engineering practice: first, mutual coupling effects between elements lead to a decrease in polarization purity and a deterioration in array axial ratio performance; second, insufficient sidelobe suppression in the array pattern under uniform excitation makes it difficult to meet the requirements of high-security scenarios. To simultaneously achieve low sidelobes and improved axial ratio, different optimizations are needed for each. Improving axial ratio often requires continuous parameter tuning and full-wave simulation of large-scale arrays, which has a long simulation cycle, and if the element parameters have many degrees of freedom, it is difficult to find a balance between parameters and axial ratio. For low sidelobes, precise control of the amplitude and phase of the antenna feed structure is usually required. For example, this can be achieved by using Taylor or Chebyshev distributions to adjust the excitation amplitude of the element antennas to optimize the radiation mode, or by using advanced algorithms to obtain the optimal phase configuration for low sidelobes. However, both amplitude modulation and phase modulation are extremely difficult for large feed networks. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a two-dimensional sidelobe suppression and axial ratio optimization method for circularly polarized antennas.

[0005] The technical problem addressed by this invention is solved as follows:

[0006] A two-dimensional sidelobe suppression and axial ratio optimization method for circularly polarized antennas is proposed. This method employs a two-dimensional control mechanism for the circularly polarized antenna array, including a feed phase dimension and a chiral reversal dimension. In the feed phase dimension, the feed phase of some antenna elements is reversed, resulting in two states: 0° and 180°. In the chiral reversal dimension, the chirality of some antenna elements is reversed, resulting in two states: original element and chiral element. By optimizing the distribution of the reversed feed phase antenna elements and the chiral elements, two-dimensional low sidelobe shaping and improved axial ratio performance of the circularly polarized array antenna are achieved.

[0007] Furthermore, based on the dual-dimensional control mechanism, each element antenna in the circularly polarized antenna array is ultimately configured into four states: the element antenna without feed phase reversal and chirality reversal is the first state, a 0° original element; the element antenna with only feed phase reversal is the second state, a 180° original element; the element antenna with only chirality reversal is the third state, a 0° chiral element; and the element antenna with both feed phase reversal and chirality reversal is the fourth state, a 180° chiral element. Optimizing the positional distribution of the 0° original element, 180° original element, 0° chiral element, and 180° chiral element can achieve two-dimensional low sidelobe shaping and improved axial ratio performance of the circularly polarized antenna.

[0008] Furthermore, the positional distribution of the 0° original array, 180° original array, 0° chiral array, and 180° chiral array is optimized using an optimization algorithm. In the multi-objective genetic algorithm, the state of each element antenna is used as the optimization variable, and the gain, sidelobes, and axial ratio of the circularly polarized antenna array are used as the optimization objectives.

[0009] Furthermore, the circularly polarized antenna array has a size of 16×16.

[0010] Furthermore, the feeding network of the circularly polarized antenna array is a common-feed network, with each element antenna being fed with equal power.

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

[0012] Furthermore, chiral reversal rotation control is applied to some of the topologically symmetrically distributed element antennas in the circularly polarized antenna array to reduce the gap between the long axis and the short axis, thereby improving the axial ratio.

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

[0014]

[0015] in, and These are right-handed and left-handed electric fields, respectively. and Let E0 and j represent the unit vectors in the horizontal and vertical directions, respectively, where E0 is the electric field amplitude and j is the imaginary part.

[0016] During the chiral reversal and rotation control of a unit antenna, the electric field components in one direction have a phase difference of 180°. If there is a 180° phase lag on the short axis, the unit antenna at that position should be in a 180° chiral state after chiral reversal. If there is a 180° phase lag on the long axis, the unit antenna at that position should be in a 0° chiral state after chiral reversal.

[0017] Furthermore, for right-hand circularly polarized array antennas, some elements are chirally inverted to become 0° left-hand circular arrays to improve the axial ratio;

[0018] Electric field of a right-hand circularly polarized array antenna Decomposed onto the two orthogonal axes of the minor and major axes, its electric field components are expressed by equation (2). The axial ratio AR of the right-hand circularly polarized array antenna is... RHCP Approximately 3, expressed by equation (3):

[0019]

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

[0021] During the transformation of a right-hand circularly polarized element antenna into a left-hand circularly polarized element antenna, if we denote the phase lag of the electric field component along the major axis, then the electric field of the left-hand circularly polarized element after chiral reversal... Expressed using equation (4):

[0022]

[0023] in, and These represent the amplitudes of the left-handed electric field components in the horizontal and vertical directions of the left-handed qubit after chiral reversal;

[0024] After the chiral-inverted left-handed array antenna is superimposed with the right-handed circularly polarized array antenna, the total electric field vector is... As given by equation (5):

[0025]

[0026] in, The electric field vector is the one from which the right-handed qubit is replaced by the left-handed qubit after chiral reversal. and These represent the amplitudes of the right-handed electric field components in the horizontal and vertical directions of the replaced right-handed strobe, respectively; since chiral reversal does not change the axial ratio, therefore

[0027] After the chiral inversion of the left-handed circular array is superimposed with the right-handed circularly polarized array antenna, the array axial ratio AR ALL As given by equation (6):

[0028]

[0029] As can be seen from the above formula, the axial ratio is improved after the chiral reversal is superimposed on the left-handed circularly polarized array antenna and the original right-handed circularly polarized array antenna.

[0030] The beneficial effects of this invention are:

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

[0032] (2) The method described in this invention can optimize the axis ratio by optimizing the positions of the 0° chiral array and the 180° chiral array. Moreover, the optimization process does not require global parameter adjustment, which avoids the need for continuous parameter tuning and optimization of large-scale arrays, saves time and significantly improves the flexibility of the design.

[0033] (3) The method described in this invention is applicable to the design of large-scale circularly polarized antennas. Attached Figure Description

[0034] Figure 1 This is a three-dimensional structural diagram of the antenna array in the method described in the embodiment;

[0035] Figure 2 This is a top view of the antenna array in the method described in the embodiment;

[0036] Figure 3 This is a diagram showing the state distribution of the antenna array elements in the method described in the embodiment.

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

[0038] Figure 5This is a top view of the second coupling slot layer, the third dielectric substrate, and the metal ground plane of the antenna array in the method described in the embodiment;

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

[0040] Figure 7 The graph shows 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 Implementation

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

[0042] This embodiment provides a two-dimensional sidelobe suppression and axial ratio optimization method for circularly polarized antennas, applicable to the design of circularly polarized antennas in satellite communications, radar systems, and 5G millimeter-wave communications. A two-dimensional control mechanism is employed for the circularly polarized antenna array, including a feed phase dimension and a chiral inversion dimension. In the feed phase dimension, the feed phase of some antenna elements is inverted, resulting in two phase differences between the feed phase of one element and the original element: 0° and 180°. In the chiral inversion dimension, the chirality of some antenna elements is inverted, resulting in two states: original element and chiral element. By optimizing the distribution of the inverted feed phase antenna elements and the chiral elements, two-dimensional low sidelobe shaping and improved axial ratio performance of the circularly polarized array antenna are achieved, ensuring circular polarization purity.

[0043] Based on a dual-dimensional control mechanism, each element antenna in the circularly polarized antenna array is ultimately configured into four states: the first state, a 0° original antenna, is an antenna without feed phase reversal and chirality reversal; the second state, a 180° original antenna, is an antenna with only feed phase reversal; the third state, a 0° chiral antenna, is an antenna with only chirality reversal; and the fourth state, a 180° chiral antenna, is an antenna with both feed phase reversal and chirality reversal. A multi-objective genetic optimization algorithm is used to optimize the positional distribution of the 0° original antenna, 180° original antenna, 0° chiral antenna, and 180° chiral antenna. The state of each element antenna is used as the optimization variable, and the gain, sidelobes, and axial ratio of the circularly polarized antenna array are used as optimization objectives, thereby achieving two-dimensional low sidelobe shaping and improved axial ratio performance of the circularly polarized antenna.

[0044] (1) Feed phase reversal shaping

[0045] Without requiring complex modifications to the feed network design of the circularly polarized antenna array, the feed phase of some element antennas can be reversed to achieve a 0° / 180° radiation phase. The radiation field of the element antenna with phase reversal in the sidelobe direction forms destructive interference with the radiation field of other element antennas, thereby reducing the combined field strength in that sidelobe direction and reducing the sidelobe level. The distribution position of the element antennas with phase reversal is determined by an optimization algorithm, thereby achieving sidelobe optimization on both sides of the circularly polarized array antenna.

[0046] (2) Chiral reversal rotation regulation

[0047] Based on the principle of chiral reversal compensation, the axial ratio of a circularly polarized array antenna is optimized by reconstructing the polarization characteristic distribution of the unit antennas. Chiral reversal chiral control is applied to some topologically symmetrically distributed unit antennas to reduce the difference between the major and minor axes, thereby improving the axial ratio. For a circularly polarized array antenna, its electric field can be decomposed into two orthogonal directions with equal amplitudes and a 90° phase difference, as shown in equation (1):

[0048]

[0049] in, and These are right-handed and left-handed electric fields, respectively. and Let E0 and j represent the unit vectors in the horizontal and vertical directions, respectively, where E0 is the electric field amplitude and j is the imaginary part.

[0050] It can be seen that during the chiral reversal rotation control process, the electric field components in one direction have a phase difference of 180°. Therefore, if there is a 180° phase lag on the short axis, the unit antenna at that position should be in a 180° chiral state after chiral reversal. If there is a 180° phase lag on the long axis, the unit antenna at that position should be in a 0° chiral state after chiral reversal.

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

[0052] For a right-hand circularly polarized array antenna, its electric field When decomposed onto the two orthogonal axes x (minor axis) and y (major axis), its electric field components can be expressed by equation (2). Due to its poor axis ratio, the axis ratio AR RHCP Approximately equal to 3, which can be expressed by equation (3):

[0053]

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

[0055] During the transformation from a right-hand circularly polarized RHCP unit to a left-hand circularly polarized LHCP unit, it is impossible to determine whether the phase lag is due to the electric field component on the major axis or the electric field component on the minor axis. Here, we assume that the electric field component on the major axis lags, then the electric field of the left-hand circularly polarized inductor after chiral reversal... It can be expressed by equation (4):

[0056]

[0057] in, and These represent the amplitudes of the left-handed electric field components in the horizontal and vertical directions of the left-handed qubit after chiral reversal.

[0058] After the chiral-inverted left-handed array antenna is superimposed with the right-handed circularly polarized array antenna, the total electric field vector is... As given by equation (5):

[0059]

[0060] in, The electric field vector is the one from which the right-handed qubit is replaced by the left-handed qubit after chiral reversal. and These represent the amplitudes of the right-handed electric field components in the horizontal and vertical directions of the replaced right-handed strobe, respectively. Since chiral reversal does not change the axial ratio, therefore...

[0061] After the chiral inversion of the left-handed circular array is superimposed with the right-handed circularly polarized array antenna, the array axial ratio AR ALL As given by equation (6):

[0062]

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

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

[0065] In this embodiment, the right-hand circularly polarized array antenna is a stacked structure slot-coupled fed dipole antenna array, comprising, 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 ground plane; the coupling slot layer is implemented using SIW (Single Injection Wave) technology. The signal is input from a waveguide port on the metal ground plane, then coupled through a 1-to-64 power divider composed of SIWs in the third dielectric substrate and through the second coupling slot layer to several 1-to-4 power dividers composed of SIWs in the second dielectric substrate, then coupled through the first coupling slot layer to the first dielectric substrate, and finally radiated into free space through the radiating patch layer. The operating frequency band of this embodiment is 37-39 GHz, and the selected dielectric substrate is Taconic TLY-5.

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

[0067] A top view of the second coupling gap layer, the third dielectric substrate, and the metal ground plane is shown below. Figure 5 As shown, coupling slots 51 of the same size are etched on the second coupling slot layer, and waveguide ports 71 are etched on the metal floor.

[0068] The radiation pattern of the 16×16 array (placed in the xoy plane) designed 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, and the sidelobe electrical averages of the two planes remain below -19dB.

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

[0070] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for dual-dimension sidelobe suppression and axial ratio optimization applied to a circularly polarized antenna, characterized in that, The dual-dimension regulation mechanism is adopted to realize the circularly polarized antenna array, including a feed phase dimension and a chiral inversion dimension; in the feed phase dimension, the feed phase of part of the unit antennas is inverted, so that the feed phase of the unit antennas presents two states of 0° and 180°; in the chiral inversion dimension, the chiral of part of the unit antennas is inverted, so that the unit antennas form two states of original subarrays and chiral subarrays; by optimizing the distribution positions of the inverted feed phase unit antennas and the chiral subarrays, the two-dimensional low-sidelobe shaping and the axial ratio performance improvement of the circularly polarized array antenna are realized.

2. The dual dimension sidelobe suppression and axial ratio optimization method applied to a circularly polarized antenna according to claim 1, characterized in that, Based on the dual-dimension regulation mechanism, each unit antenna in the circularly polarized antenna array is finally configured in four states; the unit antenna without feed phase inversion and chiral inversion is in the first state, which is a 0° original subarray; the unit antenna only with feed phase inversion is in the second state, which is a 180° original subarray; the unit antenna only with chiral inversion is in the third state, which is a 0° chiral subarray; and the unit antenna with both feed phase inversion and chiral inversion is in the fourth state, which is a 180° chiral subarray; by optimizing the position distribution of the 0° original subarray, the 180° original subarray, the 0° chiral subarray and the 180° chiral subarray, the two-dimensional low-sidelobe shaping and the axial ratio performance improvement of the circularly polarized antenna are realized.

3. The dual dimension sidelobe suppression and axial ratio optimization method applied to circularly polarized antennas according to claim 2, characterized in that, The position distribution of the 0° original subarray, the 180° original subarray, the 0° chiral subarray and the 180° chiral subarray is optimized by using an optimization algorithm; in the multi-objective genetic algorithm, the state of each unit antenna is used as an optimization variable, and the gain, sidelobe and axial ratio of the circularly polarized antenna array are used as optimization objectives.

4. The dual dimension sidelobe suppression and axial ratio optimization method for circularly polarized antenna according to claim 1, wherein, The size of the circularly polarized antenna array is 16×16.

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

6. The dual dimension sidelobe suppression and axial ratio optimization method for circularly polarized antennas according to claim 3, wherein, The feed phase of part of the unit antennas of the circularly polarized antenna array is inverted; the radiation field of the unit antenna after the feed phase inversion in the sidelobe direction and the radiation field of other unit antennas form destructive interference, so as to reduce the synthesized field strength in the sidelobe direction and reduce the sidelobe level; the distribution position of the unit antenna after the feed phase inversion is determined by using an optimization algorithm, so as to realize the sidelobe optimization of the circularly polarized array antenna.

7. The dual dimension sidelobe suppression and axial ratio optimization method applied to circularly polarized antennas according to claim 3, characterized in that, The chiral inversion of part of the unit antennas in the circularly polarized antenna array is controlled, so as to reduce the difference between the long axis and the short axis, and improve the axial ratio. The electric field of the circularly polarized array antenna is decomposed into two orthogonal directions, and the electric field amplitudes are equal and the phase difference is 90°, as shown in formula (1): wherein, and are right-handed and left-handed electric fields, respectively, and denote unit vectors in horizontal and vertical directions, respectively, E0is the electric field amplitude, and j is the imaginary unit. In the process of controlling the chiral inversion of the unit antennas, the phase difference of the electric field component in one direction is 180°; if the short axis has a 180° phase lag, the unit antenna at the position should be in the state of 180° chiral subarray after chiral inversion; if the long axis has a 180° phase lag, the unit antenna at the position should be in the state of 0° chiral subarray after chiral inversion.

8. The dual dimension sidelobe suppression and axial ratio optimization method for circularly polarized antenna according to claim 7, wherein, For a right-handed circularly polarized array antenna, part of the units are inverted to 0° left-handed subarrays to improve the axial ratio. Electric field of right-hand circularly polarized array antenna Decomposed into two orthogonal axes of minor axis and major axis, the electric field components are expressed by equation (2), and the axial ratio AR of the right-hand circularly polarized array antenna RHCP is 3, which is expressed by equation (3): wherein, and Eh and Ev represent the right-handed electric field component amplitudes of the right-handed circular polarization array in the horizontal direction and the vertical direction, respectively. In the process of right-handed circularly polarized element antenna becoming left-handed circularly polarized element antenna, the phase of the electric field component on the long axis lags behind, and then the electric field of the left-handed array after the chiral inversion is expressed by formula (4): wherein and Ei and E2represent the magnitude of the left-handed electric field component of the left-handed plasmons in the horizontal and vertical directions, respectively, after the chirality inversion. After the left-handed array elements are reversed, the total electric field vector of the left-handed array elements superimposed with the right-handed circularly polarized array antenna is given by equation (5): wherein, is the electric field vector of the right-handed array replaced by the left-handed array after the chirality inversion, and denote the right-handed electric field component amplitudes of the replaced right-handed array in the horizontal and vertical directions, respectively; the chirality inversion does not change the axial ratio magnitude, After the chiral inversion, the left-handed array elements are superimposed with the right-handed circularly polarized array antenna, and the array axial ratio AR ALL is given by equation (6): As shown in the above formula, after the left-handed subarrays are inverted, the axial ratio is improved after the left-handed subarrays are superimposed with the original right-handed circularly polarized array antenna.

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