A shared-aperture dual-mode orbital angular momentum vortex wave antenna design method

Abstract

The application provides a shared-aperture dual-mode orbital angular momentum vortex wave antenna design method, designs a patch antenna unit meeting working frequency band requirements, forms two annular antenna arrays by using the patch antenna unit, and makes the two annular antenna arrays intersect to form a staggered arrangement and share the same antenna aperture; the two annular antenna arrays are respectively designed to have a respective feed network, so that the feed signals between the array units meet the phase difference of a target orbital angular momentum; the positions of the feed points in the two feed networks are determined, a coaxial line is introduced for feed, and a dual-mode orbital angular momentum vortex wave antenna is formed; through the staggered arrangement of the two uniform circular ring arrays and the 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 OAM freedom degree on the basis of not increasing the antenna aperture, and has broad application prospects in the fields of large-capacity communication, radar target detection and imaging, etc.

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 present application adopts the following technical scheme:

[0006] The present application provides a shared aperture dual-mode orbital angular momentum vortex wave antenna design method, comprising the following steps:

[0007] S1, design a patch antenna unit meeting the requirements of the working frequency band, group the patch antenna units into two annular antenna arrays, and make the two annular antenna arrays intersect to form an interleaved layout, sharing the same antenna aperture;

[0008] The two annular antenna arrays are respectively a first annular antenna array and a second annular antenna array, and the array factors of the first annular antenna array and the second annular antenna array are respectively represented as:

[0009] (1);

[0010] (2);

[0011] Wherein, N is the number of patch antenna units in the annular antenna array. Let V be the position vector of the midpoint in space; and The first and second loop antenna arrays are spatial position vectors, respectively; j is the imaginary unit; k is the wave number in free space; and These are the coordinate azimuth angles of the nth patch antenna element in the first and second loop antenna arrays, respectively. and These are the vortex wave mode indices of the first and second loop antenna arrays, respectively; take... ;

[0012] S2. Design the feeding networks for the two ring antenna arrays respectively, so that the feeding signals between the array elements satisfy the phase difference of the target orbital angular momentum.

[0013] S3. Using the two feeding networks obtained in S2, determine the positions of the feeding points respectively, introduce a coaxial line for feeding, and form a dual-mode orbital angular momentum vortex wave antenna.

[0014] Furthermore, in S1, both of the ring antenna arrays are composed of four patch antenna elements arranged in a ring. The patch antenna elements are etched on an FR4 dielectric substrate with a relative permittivity of 4.4. The thickness of the dielectric substrate is 1.6 mm. The size of the patch antenna element is 16 mm × 11.7 mm. The radius of the ring antenna array is 30 mm, and the gap between adjacent patch antenna elements is 4 mm.

[0015] Furthermore, S2 specifically refers to:

[0016] To ensure that the target orbital angular momentum mode satisfies the phase conditions of the vortex wave mode index l1 of the first loop antenna array and the vortex wave mode index l2 of the second loop antenna array, the phase difference between the patch antenna elements of the first and second loop antenna arrays must respectively satisfy:

[0017] (3);

[0018] in, The phase of the feed signal for the nth patch antenna element in the first loop antenna array; This represents the phase of the feed signal for the nth patch antenna element in the second loop antenna array.

[0019] Furthermore, when , , At that time, the feed phase between each patch antenna element satisfies:

[0020] [ 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);

[0021] [ 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] Furthermore, in order to satisfy the phase conditions defined by formulas (4) and (5), the parallel connection point and feed point are precisely calculated, and the difference in feed line length between adjacent patch antenna elements is:

[0023] (6);

[0024] (7);

[0025] in, The feed line length from the first parallel point in the first loop antenna array to the patch antenna element on the adjacent side; The feed line length from the first parallel point in the first loop antenna array to the patch antenna element on the adjacent other side; The feed line length from the second parallel point in the first loop antenna array to the patch antenna element on the adjacent side; The feed line length from the second parallel point in the first loop antenna array to the patch antenna element on the other side is denoted as . The feed line length from the third parallel point in the second loop antenna array to the patch antenna element on the adjacent side; The feed line length from the third parallel point in the second loop antenna array to the patch antenna element on the other side; The feed line length from the fourth parallel point in the second loop antenna array to the patch antenna element on the adjacent side; The feed line length from the fourth parallel point in the second loop antenna array to the patch antenna element on the other side; λ is the phase wavelength in the medium.

[0026] Furthermore, in S3, the location of the power supply point is as follows:

[0027] ;

[0028] ;

[0029] in, The length of the feed line from the first feed point to the first parallel point in the first loop antenna array; The length of the feed line from the first feed point to the second parallel point in the first loop antenna array; The length of the feed line from the second feed point to the third parallel point in the second loop antenna array; This refers to the length of the feed line from the second feed point to the fourth parallel point in the second loop antenna array.

[0030] The beneficial effects of this invention are as follows: by arranging two uniform circular arrays in a cross pattern and designing a finely crafted feed network, dual-mode OAM vortex wave generation in the same frequency band and polarization direction is achieved. This invention introduces a new degree of freedom in OAM without increasing the antenna aperture, and has broad application prospects in fields such as high-capacity communication, radar target detection, and imaging. Furthermore, this invention can be combined with existing multi-ring array technology, resulting in a significant increase in the number of generated OAM vortex wave modes, further expanding the application space of multi-mode OAM vortex wave antennas. Attached Figure Description

[0031] Figure 1 A flowchart illustrating a design method for a dual-mode orbital angular momentum vortex wave antenna with a shared aperture;

[0032] Figure 2 This is a schematic diagram of the antenna structure;

[0033] Figure 3 The curves show how the antenna parameters change with frequency.

[0034] Figure 4 Radiation pattern when port 1 is fed;

[0035] Figure 5 Radiation pattern when port 2 is fed;

[0036] Figure 6 The phase distribution of the radiated electric field when port 1 is fed;

[0037] Figure 7 The phase distribution of the radiated electric field when port 2 is fed. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0039] A design method for a shared-aperture dual-mode orbital angular momentum vortex wave antenna includes the following steps:

[0040] S1. Design patch antenna units that meet the operating frequency band requirements, assemble the patch antenna units into two ring antenna arrays, and make the two ring antenna arrays intersect to form an interleaved layout, sharing the same antenna aperture.

[0041] The array factors of the two ring antenna arrays, namely the first ring antenna array and the second ring antenna array, are expressed as follows:

[0042] (1);

[0043] (2);

[0044] Where N is the number of patch antenna elements in the ring antenna array; Let V be the position vector of the midpoint in space; and The first and second loop antenna arrays are spatial position vectors, respectively; j is the imaginary unit; k is the wave number in free space; and These are the coordinate azimuth angles of the nth patch antenna element in the first and second loop antenna arrays, respectively. and These are the vortex wave mode indices of the first and second loop antenna arrays, respectively; take... ;

[0045] S2. Design the feeding networks for the two ring antenna arrays respectively, so that the feeding signals between the array elements satisfy the phase difference of the target orbital angular momentum.

[0046] S3. Using the two feeding networks obtained in S2, determine the positions of the feeding points respectively, introduce a coaxial line for feeding, and form a dual-mode orbital angular momentum vortex wave antenna.

[0047] In S1, both of the ring antenna arrays are composed of four patch antenna elements arranged in a ring. The patch antenna elements are etched on an FR4 dielectric substrate with a relative permittivity of 4.4. The thickness of the dielectric substrate is 1.6 mm. The size of the patch antenna element is 16 mm × 11.7 mm. The radius of the ring antenna array is 30 mm, and the gap between adjacent patch antenna elements is 4 mm.

[0048] Specifically, S2 is:

[0049] To ensure that the target orbital angular momentum mode satisfies the phase conditions of the vortex wave mode index l1 of the first loop antenna array and the vortex wave mode index l2 of the second loop antenna array, the phase difference between the patch antenna elements of the first and second loop antenna arrays must respectively satisfy:

[0050] (3);

[0051] in, The phase of the feed signal for the nth patch antenna element in the first loop antenna array; This represents the phase of the feed signal for the nth patch antenna element in the second loop antenna array.

[0052] like Figure 2As shown, the first ring antenna array has four patch antenna elements, namely 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 evenly arranged on one side of the ring in a clockwise order; the second ring antenna array has four patch antenna elements, namely 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 evenly arranged on the other side of the ring in a clockwise order.

[0053] The first and second loop antenna arrays are interleaved.

[0054] At this point, the antenna feeding structure includes two independent four-feed networks, which feed the two loop antenna arrays respectively. For the first loop antenna array, the four patch antenna elements are divided into two groups: the first patch antenna element 101 and the fourth patch antenna element 104 form one group, and the second patch antenna element 102 and the third patch antenna element 103 form another group.

[0055] When the target frequency is 5.6GHz, the first patch antenna element 101 and the fourth patch antenna element 104 are fed by microstrip lines at the upper edge of the patch antenna elements. The width of the microstrip lines is 0.72mm and the input impedance is 100Ω. The two microstrip lines are connected in parallel at the first parallel connection point A1. The impedance after parallel connection is 50Ω. In order to perform impedance matching, an impedance transformer with a characteristic impedance of 70.7Ω is connected at the first parallel connection point A1. The impedance after transformation is still 100Ω. The width of the impedance transformer is 1.66mm and the length is 7.12mm. Correspondingly, the second patch antenna element 102 and the third patch antenna element 103 are fed by microstrip lines at the lower edge of the patch antenna elements. The microstrip line width is 0.72 mm and the input impedance is 100 Ω. The two microstrip lines are connected in parallel at the second parallel point B1, and the impedance after parallel connection is 50 Ω. To perform impedance matching, an impedance transformer with a characteristic impedance of 70.7 Ω is connected at the second parallel point B1. The impedance after transformation is still 100 Ω. The impedance transformer has a width of 1.66 mm and a length of 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 fed by a coaxial line at the first feed point C1. The same feeding method is used for the second loop antenna array, which will not be described in detail here.

[0056] when , , At that time, the feed phase between each patch antenna element satisfies:

[0057] [ 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);

[0058] [ 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).

[0059] To satisfy the phase conditions defined by formulas (4) and (5), precise calculations are performed on the parallel connection point and the feed point. The difference in feed line length between adjacent patch antenna elements is then:

[0060] (6);

[0061] (7);

[0062] In the first loop antenna array, the feed line lengths from the first parallel point A1 to the first patch antenna element 101 and the fourth patch antenna element 104 are respectively... and In the first loop antenna array, the feed line lengths from the second parallel point B1 to the second patch antenna element 102 and the third patch antenna element 103 are respectively... and In the second loop antenna array, the feed line lengths from the third parallel point A2 to the fifth patch antenna element 201 and the eighth patch antenna element 204 are respectively... and In the second ring antenna array, the feed line lengths from the fourth parallel point B2 to the sixth patch antenna element 202 and the seventh patch antenna element 203 are respectively... and ; λ is the phase wavelength in the medium.

[0063] In S3, the location of the power supply point is:

[0064] (8);

[0065] (9);

[0066] in, The length of the feeder line from the first feed point C1 to the first parallel point A1; The length of the feeder line from the first feed point C1 to the second parallel point B1; The length of the feeder line from the second feed point C2 to the third parallel point A2; The length of the feeder line from the second feed point C2 to the fourth parallel point B2.

[0067] Furthermore, 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.

[0068] This multi-mode OAM vortex wave antenna design method, namely the dual-mode OAM vortex wave antenna based on a shared aperture, is based on the traditional array antenna design concept. It deploys two antenna arrays on the same aperture plane and, combined with an appropriate feed network design, successfully generates OAM vortex waves of different modes.

[0069] OAM vortex waves of different modes can be generated under the same frequency band and polarization conditions, which can make full use of the new degrees of freedom of OAM.

[0070] It can be easily combined with other multimode OAM generation methods, such as multi-ring array antenna technology, to further expand the number of modes of OAM vortex wave antennas, and has broad application prospects in communication and radar fields.

[0071] Figure 3 The graph shows the emission coefficient curves of the two arrays. As can be seen from the graph, the port reflection coefficients of the first and second loop antenna arrays are both less than -10dB in the 5.4GHz~6GHz frequency band, which demonstrates good impedance matching characteristics. Furthermore, the mutual coupling in this frequency band is less than -20dB, which shows good port isolation characteristics.

[0072] Figure 4 and Figure 5 The images show the 5.6 GHz radiation patterns of the antenna when fed by port 1 and port 2, respectively. It can be seen that the radiation patterns in both modes exhibit an energy dip at the beam axis, which is typical of vortex beams. Figure 6 and Figure 7 The figures show the spatial phase distribution characteristics of the 5.6 GHz radiation beam when fed by port 1 and port 2, respectively. It can be seen that when fed by port 1, the phase of the radiation beam is distributed in a counterclockwise spiral, indicating that its corresponding vortex wave mode is +1. When fed by port 2, the phase of the radiation beam is distributed in a clockwise spiral, indicating that its corresponding vortex wave mode is -1.

[0073] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be defined by 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, Includes the following steps: S1. Design patch antenna units that meet the operating frequency band requirements, assemble the patch antenna units into two ring antenna arrays, and make the two ring antenna arrays intersect to form an interleaved layout, sharing the same antenna aperture. The array factors of the two ring antenna arrays, namely the first ring antenna array and the second ring antenna array, are expressed as follows: （1）； （2）； Where N is the number of patch antenna elements in the ring antenna array; Let V be the position vector of the midpoint in space; and The first and second loop antenna arrays are spatial position vectors, respectively; j is the imaginary unit; k is the wave number in free space; and Let l1 and l2 be the coordinate azimuth angles of the nth patch antenna element in the first and second loop antenna arrays, respectively; l1 and l2 are the vortex wave mode indices of the first and second loop antenna arrays, respectively; take l1 = -l2; S2. Design the feeding networks for the two ring antenna arrays respectively, so that the feeding signals between each array element satisfy the phase difference of the target orbital angular momentum. S3. Determine the positions of the feed points in the two feed networks obtained in S2, and introduce a coaxial line for feeding to form a dual-mode orbital angular momentum vortex wave antenna. Specifically, S2 is: To ensure that the target orbital angular momentum mode satisfies the phase conditions of the vortex wave mode index l1 of the first loop antenna array and the vortex wave mode index l2 of the second loop antenna array, the phase difference between the patch antenna elements of the first and second loop antenna arrays must respectively satisfy: （3）； in, The phase of the feed signal for the nth patch antenna element in the first loop antenna array; This represents the phase of the feed signal for the nth patch antenna element in the second loop antenna array.

2. The design method for a dual-mode orbital angular momentum vortex wave antenna with shared aperture according to claim 1, characterized in that: In S1, both of the ring antenna arrays are composed of four patch antenna elements arranged in a ring. The patch antenna elements are etched on an FR4 dielectric substrate with a relative permittivity of 4.

4. The thickness of the dielectric substrate is 1.6 mm. The size of the patch antenna element is 16 mm × 11.7 mm. The radius of the ring antenna array is 30 mm, and the gap between adjacent patch antenna elements is 4 mm.

3. The design method for a dual-mode orbital angular momentum vortex wave antenna with shared aperture according to claim 2, characterized in that: when , , At that time, the feed phase between each patch antenna element satisfies: （4）； （5）。 4. The design method for a dual-mode orbital angular momentum vortex wave antenna with shared aperture according to claim 3, characterized in that: To satisfy the phase conditions defined by formulas (4) and (5), precise calculations are performed on the parallel connection point and the feed point. The difference in feed line length between adjacent patch antenna elements is then: （6）； （7）； in, The feed line length from the first parallel point in the first loop antenna array to the patch antenna element on the adjacent side; The feed line length from the first parallel point in the first loop antenna array to the patch antenna element on the adjacent other side; The feed line length from the second parallel point in the first loop antenna array to the patch antenna element on the adjacent side; The feed line length from the second parallel point in the first loop antenna array to the patch antenna element on the other side is denoted as . The feed line length from the third parallel point in the second loop antenna array to the patch antenna element on the adjacent side; The feed line length from the third parallel point in the second loop antenna array to the patch antenna element on the other side; The feed line length from the fourth parallel point in the second loop antenna array to the patch antenna element on the adjacent side; The feed line length from the fourth parallel point in the second loop antenna array to the patch antenna element on the other side is denoted as . λ is the phase wavelength in the medium.

5. The design method for a shared-aperture dual-mode orbital angular momentum vortex wave antenna according to claim 4, characterized in that: In S3, the location of the power supply point is: ； ； in, The length of the feed line from the first feed point to the first parallel point in the first loop antenna array; The length of the feed line from the first feed point to the second parallel point in the first loop antenna array; The length of the feed line from the second feed point to the third parallel point in the second loop antenna array; This refers to the length of the feed line from the second feed point to the fourth parallel point in the second loop antenna array.

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