Design method of aperture-shared dual-mode orbital angular momentum vortex wave antenna

Abstract

The invention provides a method for designing a dual-mode orbital angular momentum vortex wave antenna with a shared aperture, which comprises the following steps of: designing patch antenna units meeting the requirement of a working frequency band, forming two annular antenna arrays by the patch antenna units, and enabling the two annular antenna arrays to intersect to form a staggered arrangement layout and share the same antenna aperture; respectively designing respective feed networks of the two loop antenna arrays, so that feed signals among the array units meet the phase difference of the target orbital angular momentum; the positions of feeding points are respectively determined in the two feeding networks, a coaxial line is introduced for feeding, and the dual-mode orbital angular momentum vortex wave antenna is formed; through cross arrangement of two uniform circular ring arrays and fine design of a feed network, generation of dual-mode OAM vortex waves in the same frequency band and the same polarization direction is realized. On the basis that the aperture of the antenna is not increased, the OAM new degree of freedom is introduced, and the antenna has wide application prospects in the fields of high-capacity communication, radar target detection and imaging and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of antenna, in particular to a shared aperture dual-mode orbital angular momentum vortex wave antenna design method. BACKGROUND

[0002] The electromagnetic wave carrying the orbital angular momentum (OAM) has a spiral wave front structure, and is therefore called OAM vortex wave. The OAM vortex waves of different vortex modes have the unique property of orthogonal isolation, and can independently carry information, so the OAM becomes another new information modulation degree of freedom after amplitude, frequency, phase and polarization, and is expected to bring a new solution to the problem of increasingly tight information spectrum resources.

[0003] In order to fully utilize the OAM degree of freedom, the antenna needs to be able to produce multiple vortex wave modes at the same time, however, some existing researches produce different vortex modes in different polarization directions or different frequency bands, which is equivalent to wasting a degree of freedom; some use multi-ring nested array structure, which increases the aperture size of the antenna. How to produce different OAM vortex waves in the same polarization and the same frequency band without significantly increasing the aperture size of the array antenna is of great significance. SUMMARY

[0004] The present application aims at the deficiencies of the prior art, and provides a shared aperture dual-mode orbital angular momentum vortex wave antenna design method, which fully utilizes the new OAM degree of freedom and solves the problem of producing multiple mode OAM vortex waves under multiple constraints.

[0005] To achieve the above object, the technical scheme adopted by the present application is as follows: The present application provides a shared aperture dual-mode orbital angular momentum vortex wave antenna design method, comprising the following steps: S1, designing a patch antenna unit meeting the requirements of the working frequency band, grouping the patch antenna units into two ring antenna arrays, and making the two ring antenna arrays intersect to form an interleaved layout, sharing the same antenna aperture; The two ring antenna arrays are respectively a first ring antenna array and a second ring antenna array, and the array factors of the first ring antenna array and the second ring antenna array are respectively represented as: (1); (2); Wherein, N is the number of patch antenna units in the ring antenna array; is the position vector of the field point in space; and respectively the first annular antenna array and the second annular antenna array are spatial position vectors; j is an imaginary unit; k is a wave number in free space; and respectively the first annular antenna array and the second annular antenna array are spatial position vectors; j is an imaginary unit; k is a wave number in free space; and respectively the first annular antenna array and the second annular antenna array are spatial position vectors; j is an imaginary unit; k is a wave number in free space; ; S2, respectively, design the feeding network of the two annular antenna arrays, so that the feeding signals between the array units meet the phase difference of the target orbital angular momentum; S3, using the positions of the feeding points determined in the two feeding networks obtained in S2, introducing a coaxial line for feeding, to form a dual-mode orbital angular momentum vortex wave antenna.

[0006] Further, in the S1, the two annular antenna arrays are each composed of four patch antenna units arranged in a ring, the patch antenna units are etched on an FR4 dielectric substrate, the relative dielectric constant of the dielectric substrate is 4.4, the thickness of the dielectric substrate is 1.6 mm, the size of the patch antenna unit is 16 mm x 11.7 mm, the radius of the annular antenna array is 30 mm, and the gap between adjacent patch antenna units is 4 mm.

[0007] Further, the S2 is specifically: In order to make the target orbital angular momentum mode meet the phase conditions of the vortex wave mode index l1 of the first annular antenna array and the vortex wave mode index l2 of the second annular antenna array, respectively, the phase difference between the patch antenna units of the first annular antenna array and the second annular antenna array needs to meet: (3) ; wherein, is the feeding signal phase of the nth patch antenna unit in the first annular antenna array; is the feeding signal phase of the nth patch antenna unit in the second annular antenna array.

[0008] Further, when , , , the feeding phase between each patch antenna unit meets: [ ϕ 1 2 − ϕ 1 1 ϕ 1 3 − ϕ 1 2 ϕ 1 4 − ϕ 1 3 ϕ 1 1 − ϕ 1 4 ] = [ π 2 π 2 π 2 π 2 ] (4) ; [ ϕ 2 2 − ϕ 2 1 ϕ 2 3 − ϕ 2 2 ϕ 2 4 − ϕ 2 3 ϕ 2 1 − ϕ 2 4 ] = [ − π 2 − π 2 − π 2 − π 2 ] (5).

[0009] Further, in order to satisfy the phase condition defined by the formula (4) and the formula (5), the parallel point and the feed point are accurately calculated, and then the length difference of the feed line of the adjacent patch antenna unit is: (6) ; (7) ; is the length of the feed line from the first parallel point to the patch antenna unit on the adjacent one side in the first annular antenna array; is the length of the feed line from the first parallel point to the patch antenna unit on the adjacent other side in the first annular antenna array; is the length of the feed line from the second parallel point to the patch antenna unit on the adjacent one side in the first annular antenna array; is the length of the feed line from the second parallel point to the patch antenna unit on the adjacent other side in the first annular antenna array; is the length of the feed line from the third parallel point to the patch antenna unit on the adjacent one side in the second annular antenna array; is the length of the feed line from the third parallel point to the patch antenna unit on the adjacent other side in the second annular antenna array; is the length of the feed line from the fourth parallel point to the patch antenna unit on the adjacent one side in the second annular antenna array; is the length of the feed line from the fourth parallel point to the patch antenna unit on the adjacent other side in the second annular antenna array; is the wavelength of the wave in the medium.

[0010] Further, in the S3, the position of the feed point is: ; ; is the length of the feed line from the first feed point to the first parallel point in the first annular antenna array; is the length of the feed line from the first feed point to the second parallel point in the first annular antenna array; is the length of the feed line from the second feed point to the third parallel point in the second annular antenna array; is the length of the feed line from the second feed point to the fourth parallel point in the second annular antenna array.

[0011] ​​The application has the beneficial effects that: by cross arrangement of two uniform circular array and fine design of the feed network, dual-mode OAM vortex wave generation in the same frequency band and the same polarization direction is realized. The application introduces a new degree of freedom of OAM without increasing the antenna aperture, and has broad application prospects in the fields of large-capacity communication, radar target detection and imaging. In addition, the application can be combined with the existing multi-ring array technology, so that the generated OAM vortex wave mode is doubled, further expanding the application space of the multi-mode OAM vortex wave antenna. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 A flowchart of a shared-aperture dual-mode orbital angular momentum vortex wave antenna design method; Figure 2 An antenna structure schematic diagram; Figure 3 A parameter curve of the antenna varying with frequency; Figure 4 A radiation pattern when port 1 is fed; Figure 5 A radiation pattern when port 2 is fed; Figure 6 A radiation electric field phase distribution when port 1 is fed; Figure 7 A radiation electric field phase distribution when port 2 is fed. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical scheme and advantages of the application clearer and more understandable, the application will be further described in detail below with reference to the drawings. It should be understood that the specific embodiments described herein are only used to explain the application and not to limit the application.

[0014] A shared-aperture dual-mode orbital angular momentum vortex wave antenna design method, comprising the following steps: S1, a patch antenna unit meeting the working frequency band requirement is designed, the patch antenna unit is composed of two annular antenna arrays, and the two annular antenna arrays are intersected to form an interleaved arrangement, sharing the same antenna aperture; The array factors of the first annular antenna array and the second annular antenna array are respectively represented as: (1); (2); Wherein, N is the number of patch antenna units in the annular antenna array; is the position vector of a field point in space; and are the spatial position vectors of the first and second annular antenna arrays respectively; j is the imaginary unit; k is the wave number in free space; and are the coordinate azimuth angles of the n-th patch antenna element of the first and second annular antenna arrays respectively; and are the vortex wave mode indexes of the first and second annular antenna arrays respectively; take ; S2, the feeding networks of the two annular antenna arrays are respectively designed, so that the phase difference of the feeding signals between the array elements meets the target orbital angular momentum; S3, the positions of the feeding points in the two feeding networks obtained in S2 are determined, a coaxial line is introduced for feeding, and a dual-mode orbital angular momentum vortex wave antenna is formed.

[0015] In S1, the two annular antenna arrays are each composed of four patch antenna elements arranged in a ring. The patch antenna elements are etched on an FR4 dielectric substrate. The relative dielectric constant of the dielectric substrate is 4.4. The thickness of the dielectric substrate is 1.6 mm. The size of the patch antenna element is 16 mm x 11.7 mm. The radius of the annular antenna array is 30 mm. The gap between adjacent patch antenna elements is 4 mm.

[0016] S2 is specifically: In order to make the target orbital angular momentum mode meet the phase conditions of the vortex wave mode index l1 of the first annular antenna array and the vortex wave mode index l2 of the second annular antenna array respectively, the phase difference between the patch antenna elements of the first annular antenna array and the second annular antenna array needs to meet: (3) ; wherein, is the feeding signal phase of the n-th patch antenna element in the first annular antenna array; is the feeding signal phase of the n-th patch antenna element in the second annular antenna array.

[0017] As shown in Figure 2 , the patch antenna elements of the first annular antenna array are four, which are the first patch antenna element 101, the second patch antenna element 102, the third patch antenna element 103 and the fourth patch antenna element 104, which are uniformly arranged on the ring on one side in clockwise order; the patch antenna elements of the second annular antenna array are four, which are the fifth patch antenna element 201, the sixth patch antenna element 202, the seventh patch antenna element 203 and the eighth patch antenna element 204, which are uniformly arranged on the ring on the other side in clockwise order.

[0018] The first annular antenna array and the second annular antenna array are staggered.

[0019] At this time, the feeding structure of the antenna includes two independent four-feed networks, which feed the two annular antenna arrays respectively. For the first annular antenna array, the four patch antenna units are divided into two groups, i.e., the first patch antenna unit 101 and the fourth patch antenna unit 104 are a group, and the second patch antenna unit 102 and the third patch antenna unit 103 are a group.

[0020] When the target frequency point is 5.6 GHz, the first patch antenna unit 101 and the fourth patch antenna unit 104 are fed by microstrip lines at the upper edge of the patch antenna unit, the width of the microstrip line is 0.72 mm, the input impedance is 100 Ω, and the two microstrip lines are connected in parallel at the first parallel point A1, and the impedance after parallel connection is 50 Ω. In order to match the impedance, an impedance transformer with a characteristic impedance of 70.7 Ω is connected at the first parallel point A1, and the impedance after transformation is still 100 Ω. The width of the impedance transformer is 1.66 mm, and the length is 7.12 mm. Correspondingly, the second patch antenna unit 102 and the third patch antenna unit 103 are fed by microstrip lines at the lower edge of the patch antenna unit, the width of the microstrip line is 0.72 mm, the input impedance is 100 Ω, and the two microstrip lines are connected in parallel at the second parallel point B1, and the impedance after parallel connection is 50 Ω. In order to match the impedance, an impedance transformer with a characteristic impedance of 70.7 Ω is connected at the second parallel point B1, and the impedance after transformation is still 100 Ω. The width of the impedance transformer is 1.66 mm, and the length is 7.12 mm. After impedance transformation at the first parallel point A1 and the second parallel point B1, the two 100 Ω microstrip lines are connected together and are fed by a coaxial line at the first feeding point C1. For the second annular antenna array, the same feeding method is adopted, and details are not described here.

[0021] When , , the feeding phase between each patch antenna unit satisfies: [ ϕ 1 2 − ϕ 1 1 ϕ 1 3 − ϕ 1 2 ϕ 1 4 − ϕ 1 3 ϕ 1 1 − ϕ 1 4 ] = [ π 2 π 2 π 2 π 2 ] (4); [ ϕ 2 2 − ϕ 2 1 ϕ 2 3 − ϕ 2 2 ϕ 2 4 − ϕ 2 3 ϕ 2 1 − ϕ 2 4 ] = [ − π 2 − π 2 − π 2 − π 2 ] (5).

[0022] In order to meet the phase conditions defined by formula (4) and formula (5), the parallel points and the feeding points are accurately calculated, and the length difference of the feeding lines of adjacent patch antenna units is: (6); (7); In the first annular antenna array, the lengths of the feed lines from the first parallel point A1 to the first patch antenna unit 101 and the fourth patch antenna unit 104 are respectively and In the first annular antenna array, the lengths of the feed lines from the second parallel point B1 to the second patch antenna unit 102 and the third patch antenna unit 103 are respectively and In the second annular antenna array, the lengths of the feed lines from the third parallel point A2 to the fifth patch antenna unit 201 and the eighth patch antenna unit 204 are respectively and In the second annular antenna array, the lengths of the feed lines from the fourth parallel point B2 to the sixth patch antenna unit 202 and the seventh patch antenna unit 203 are respectively and ; is the wavelength of the phase wave in the medium.

[0023] In the S3, the position of the feeding point is: (8); (9); wherein, is the length of the feed line from the first feeding point C1 to the first parallel point A1; is the length of the feed line from the first feeding point C1 to the second parallel point B1; is the length of the feed line from the second feeding point C2 to the third parallel point A2; is the length of the feed line from the second feeding point C2 to the fourth parallel point B2.

[0024] In addition, the feed phase difference between the first patch antenna unit 101 and the third patch antenna unit 103, the fourth patch antenna unit 104 and the second patch antenna unit 102, the fifth patch antenna unit 201 and the seventh patch antenna unit 203, and the eighth patch antenna unit 204 and the sixth patch antenna unit 202 should be 180 degrees.

[0025] The multi-mode OAM vortex wave antenna design method, i.e. the dual-mode OAM vortex wave antenna based on shared aperture, based on the design idea of shared aperture on the basis of traditional array antenna, two antenna arrays are arranged on the same aperture surface, and different modes of OAM vortex wave are successfully generated by combining appropriate feed network design; Different modes of OAM vortex wave can be generated under the same frequency band and the same polarization condition, and the new degree of freedom of OAM can be fully utilized; It is easy to combine with other multi-mode OAM generation methods, such as multi-ring array antenna technology, to further expand the mode number of OAM vortex wave antenna, and has broad application prospects in the fields of communication and radar.

[0026] Figure 3 The transmission coefficient curves of the two arrays are shown in the figure, and it can be seen that the port reflection coefficients of the first and second ring antenna arrays are less than-10dB in the frequency band of 5.4GHz~6GHz, which reflects good impedance matching characteristics, and the mutual coupling in the frequency band is less than-20dB, which has good port isolation characteristics.

[0027] Figure 4 and Figure 5 The 5.6GHz radiation patterns of the antenna when port 1 is fed and port 2 is fed are shown in the figures, and it can be seen that the directional patterns in the two modes are both concave at the beam axis, which has the typical directional pattern characteristics of vortex beams. Figure 6 and Figure 7 The spatial phase distribution characteristics of the 5.6GHz radiation beams when port 1 is fed and port 2 is fed are shown in the figures, and it can be seen that the radiation beam phase is counterclockwise spiral distribution when port 1 is fed, which indicates that the corresponding vortex wave mode is +1, and the radiation beam phase is clockwise spiral distribution when port 2 is fed, which indicates that the corresponding vortex wave mode is-1.

[0028] The above-described embodiments only express the embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as limiting the scope of the patent of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be based on the appended claims.

Claims

1. A design method for a dual-mode orbital angular momentum vortex wave antenna with a shared aperture, characterized in that, The method comprises the following steps: S1, designing a patch antenna unit meeting the requirements of a working frequency band, forming two annular antenna arrays by the patch antenna units, and making the two annular antenna arrays intersect to form an interleaved layout and share the same antenna aperture; The array factors of the first annular antenna array and the second annular antenna array are respectively denoted as: （1）； （2）； where N is the number of patch antenna elements in the ring antenna array; is the position vector of the field point in space; and are the position vectors of the first and second ring antenna arrays, respectively; j is the imaginary unit; k is the wave number in free space; and are the azimuthal angles of the n-th patch antenna element of the first and second ring antenna arrays, respectively; and are the vortex wave mode indices of the first and second ring antenna arrays, respectively; take ; S2, designing a feeding network for each of the two annular antenna arrays respectively, so that the feeding signals between the array units meet the phase difference of the target orbital angular momentum; S3, determining the positions of the feeding points in the two feeding networks obtained in S2, introducing a coaxial line for feeding, and forming a dual-mode orbital angular momentum vortex wave antenna.

2. The method of claim 1, wherein the shared-aperture dual-mode orbital angular momentum vortex wave antenna design method is characterized by: In S1, the two annular antenna arrays are each composed of four patch antenna units arranged in a ring, the patch antenna units are etched on an FR4 dielectric substrate, the relative dielectric constant of the dielectric substrate is 4.4, the thickness of the dielectric substrate is 1.6 mm, the size of the patch antenna unit is 16 mm x 11.7 mm, the radius of the annular antenna array is 30 mm, and the gap between adjacent patch antenna units is 4 mm.

3. The method of claim 2, wherein, In S2, the phase difference between the patch antenna units of the first annular antenna array and the second annular antenna array is calculated as follows: In order to make the target orbital angular momentum modes meet the phase conditions of the vortex wave mode index l1 of the first annular antenna array and the vortex wave mode index l2 of the second annular antenna array respectively, the phase difference between the patch antenna units of the first annular antenna array and the second annular antenna array needs to meet the following conditions respectively: （3）； wherein, is a feed signal phase of an nth patch antenna unit in the first annular antenna array; is a feed signal phase of an nth patch antenna unit in the second annular antenna array.

4. The method of claim 3, wherein the method further comprises: When , , the feeding phase between the individual patch antenna elements satisfies: （4）； （5）。 5. The method of claim 4, wherein the method further comprises: In order to meet the phase conditions defined by formula (4) and formula (5), the parallel points and the feeding points are accurately calculated, and the length difference of the feeding lines of adjacent patch antenna units is: （6）； （7）； wherein, is a feed line length from the first parallel point to a patch antenna element on an adjacent side in the first annular antenna array; is a feed line length from the first parallel point to a patch antenna element on an adjacent side in the first annular antenna array; is a feed line length from the second parallel point to a patch antenna element on an adjacent side in the first annular antenna array; is a feed line length from the second parallel point to a patch antenna element on an adjacent side in the first annular antenna array; is a feed line length from the third parallel point to a patch antenna element on an adjacent side in the second annular antenna array; is a feed line length from the third parallel point to a patch antenna element on an adjacent side in the second annular antenna array; is a feed line length from the fourth parallel point to a patch antenna element on an adjacent side in the second annular antenna array; is a feed line length from the fourth parallel point to a patch antenna element on an adjacent side in the second annular antenna array; is a phase wavelength in the medium.

6. The method of claim 5, wherein: In S3, the positions of the feeding points are as follows: ； ； wherein, is a feed line length from the first feed point to the first parallel point in the first loop antenna array; is a feed line length from the first feed point to the second parallel point in the first loop antenna array; is a feed line length from the second feed point to the third parallel point in the second loop antenna array; is a feed line length from the second feed point to the fourth parallel point in the second loop antenna array.

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