X / Ka dual-band diffraction-free Airy vortex electromagnetic wave antenna

Abstract

The invention discloses an X / Ka dual-band diffraction-free Airy vortex electromagnetic wave antenna, which comprises a feed source and a reflective array surface, the reflective array surface faces an aperture radiating surface of the feed source and is divided into a central disc region and an external annular region; the reflection array plane comprises a plurality of square ring patches which are periodically arranged and a plurality of cross patches which are periodically arranged, and the square ring patch located in a central disc area is used for performing phase compensation on Ka-frequency-band incident electromagnetic waves emitted by the feed source; the cross patches located in the central disc area and the outer annular area are used for conducting phase compensation on X-frequency-band incident electromagnetic waves emitted by the feed source. According to the invention, the phase of the reflected electromagnetic wave is modulated, so that the antenna has vortex characteristics and Airy beam self-healing and long-distance focusing characteristic capabilities on the incident electromagnetic wave, and Airy vortex beams in different modes have equal divergence angles. The method has a potential application prospect in the fields of large-capacity high-speed communication of spacecrafts and high-resolution radar imaging.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave antennas, and specifically relates to an X / Ka dual-band non-diffraction Airy vortex electromagnetic wave antenna. Background Art

[0002] In the face of future demands for large-capacity, high-speed communications and high-resolution radar imaging, vortex electromagnetic waves carrying orbital angular momentum (OAM) can improve spectral efficiency, communication capacity and radar resolution by utilizing the orthogonality between their modes, becoming a potential technology for the next generation of large-capacity, high-speed wireless transmission, and has the potential to be applied in various fields such as satellite communications, the Internet of Things, virtual reality / augmented reality, and high-definition video transmission.

[0003] However, the OAM beam has a "donut"-shaped electric field intensity distribution, and its cross-section increases with the increase of transmission distance. Obviously, the divergence of the vortex beam severely limits the range of communication and radar. However, the non-diffracting vortex electromagnetic wave antenna combines the OAM beam with infinite modulation freedom with the non-diffracting beam (NDB) with long-distance bunching propagation characteristics, realizing the high-focusing and low-divergence transmission of the OAM beam. However, at present, most scholars at home and abroad have relatively mature research on the generation principle of vortex electromagnetic waves and preliminary experimental verification for communication, and only a very small number of scholars study non-diffracting vortex beams. At present, most non-diffracting vortex beams are high-order Bessel vortex beams, and few scholars pay attention to Airy vortex electromagnetic wave beams with sudden self-focusing and self-healing characteristics. Considering that the antenna is severely blocked by the large number of carrier platform equipment, the Airy beam is very suitable for complex satellite platform applications due to its self-healing and long-distance focusing characteristics.

[0004] However, in order to achieve OAM multiplexing, the vortex electromagnetic wave antenna is required to generate multiple OAM modes at the same time. However, the higher the OAM mode, the larger the beam divergence angle. The different divergence angles and beam widths of vortex waves of different modes result in the fact that once the aperture of the receiving antenna is determined, it may not be able to receive the peak power of the high-order OAM mode. Therefore, the sub-channel link estimates of different modes are different, which seriously reduces the receiving signal-to-noise ratio of OAM wireless communication. In addition, most of the current multi-modal vortex electromagnetic wave antennas have problems with complex generation structures and inconsistent beam divergence angles, making it difficult to achieve multi-modal and multi-dimensional multiplexing. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects and provide an X / Ka dual-band diffraction-free Airy vortex electromagnetic wave antenna, which solves the technical problems of beam divergence, single mode and inconsistent divergence angles of different modes of existing vortex electromagnetic wave antennas. The present invention modulates the phase of the reflected electromagnetic wave so that the antenna has vortex characteristics and Airy beam self-healing and long-distance focusing characteristics for the incident electromagnetic wave, thereby achieving the characteristic of consistent divergence angles of beams of different modes, and has potential application prospects in the fields of large-capacity high-speed communications and high-resolution radar imaging of spacecraft.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] An X / Ka dual-band non-diffraction Airy vortex electromagnetic wave antenna, comprising a feed source and a reflection array;

[0008] The feed sources include X-band feed and Ka-band feed. The X-band feed uses oblique incidence feeding, and the Ka-band feed uses positive feeding to reduce the impact of shielding.

[0009] The reflection array is the aperture radiation surface facing the feed source, which is divided into a central disk area and an outer ring area; the reflection array includes a number of periodically arranged square ring patches and a number of periodically arranged cross patches. The square ring patches are used to perform phase compensation for the Ka-band incident electromagnetic waves emitted by the feed source, and the cross patches are used to perform phase compensation for the X-band incident electromagnetic waves emitted by the feed source.

[0010] Furthermore, the square ring patch includes a square metal ring and a square patch embedded in the square metal ring.

[0011] Furthermore, the inner side length l of the square metal ring Ka =0.05λ1~1λ1, λ1 is the wavelength of the incident wave in the Ka band in vacuum;

[0012] The reflection phase of the square ring patch varies with the inner side length l of the square metal ring. Ka increases with the increase of

[0013] The side length of the square patch is l2 = k′·l Ka , k′=0.5~1.

[0014] Furthermore, the arm length l of the cross patch X =0.2λ2~0.6λ2, λ2 is the wavelength of the X-band incident wave in vacuum; the reflection phase of the cross patch changes with the arm length l of the cross patch X increases with the increase of

[0015] The width w of the cross patch x It is 0.1mm~0.5mm.

[0016] Furthermore, the inner side length l of the square metal ringKa and the arm length l of the cross patch X They are determined according to the expected reflection phase of the Ka band and the expected reflection phase of the X band respectively.

[0017] Furthermore, the expected reflection phase ψ mn Calculate according to the following formula:

[0018]

[0019] Where Φ1 is the Airy phase distribution, l is the vortex mode number, is the azimuth angle corresponding to the (m,n)th patch, k0 is the propagation constant at different frequencies, r mn is the distance from the (m,n)th reflection unit to the center of the reflection front, and F is the distance from the phase center of the feed antenna to the center of the reflection front;

[0020] The Airy phase distribution Φ1 is calculated according to the following formula:

[0021]

[0022] Where Ai(·) is the Airy function, b0 is a constant, r0 is the radius parameter of the main ring of the Airy beam, and the initial radius of the Airy vortex beam is R0=r0+(1+b0); r0=k m ·D, k m Take 0.02~0.3, D is the aperture size of the reflection array, satisfying b0=k rb / r0, where k rb Is a positive number.

[0023] Further, the area where the square ring patch is located is recorded as the first area, and the area where the cross patch is located is recorded as the second area;

[0024] The first area is a circle centered on the reflection front, namely the central disk area, and the radius of the circle is R1;

[0025] The second area is a circle centered on the reflection front, and the radius of the circle is R2;

[0026] 1 / 2D≥R2>R1>0; D is the aperture size of the reflection array;

[0027] In the first area, there are both square ring patches and cross patches;

[0028] In the second region outside the first region, i.e., the outer annular region, only cross patches exist;

[0029] Furthermore, R1 and R2 are determined according to the following two formulas:

[0030] When the undiffracted Airy beam is not considered, the radiation pattern of the circular reflector array is calculated as follows:

[0031]

[0032] Where R is the radius parameter of the circular reflection array, is the hypergeometric function, θ and Denote the elevation angle and azimuth angle respectively, and l is the OAM mode order. Select the X-band circular reflector array radius R2 value and OAM mode order l according to the requirements. OAM1 , the elevation angle θ corresponding to the peak value of the X-band radiation pattern is obtained by formula (3): max In order to achieve the same beam divergence angle for the X-band and Ka-band vortex beams, the elevation angle corresponding to the peak of the Ka-band radiation pattern is set to be equal to θ max . Select the Ka-band OAM mode order l according to the requirements OAM2 The radius R of the Ka-band circular reflector array with only vortex characteristics without considering the non-diffracting Airy beam is obtained by formula (3): 1-OAM value.

[0033] When the vortex beam is not considered, the radius of the non-diffraction Airy circular reflection array is calculated as follows:

[0034]

[0035] Where R is the radius parameter of the circular reflection array, z f is the ideal focal distance of the non-diffracting Airy beam when the vortex beam is not considered. k rb The larger the k is, the stronger the non-diffraction focusing property of the Airy beam is. rb , k m The value and the determined X-band circular reflection array radius R2 value can be used to obtain the focal distance z of the X-band non-diffracting Airy beam without considering the vortex electromagnetic wave through formula (4): f In order to achieve the focusing of the X-band and Ka-band non-diffracting Airy beams at the same position, the focal distance of the Ka-band non-diffracting Airy beam is set to be equal to z f According to the determined z f , k m , R 1-OAM , the Ka-band non-diffraction Airy beam k is obtained by formula (4): r ' b value.

[0036] The non-diffraction Airy vortex electromagnetic wave antenna combines the vortex characteristics and the non-diffraction Airy beam focusing characteristics to achieve a non-diffraction vortex beam. Considering that the larger the vortex beam mode order, the larger the beam divergence angle, the Ka-band reflector array needs to enhance the non-diffraction focusing effect of the Airy beam, so a larger k is selected. r ” b value, whose value is greater than k r ' b According to the determined z f , k m , k r ” b , the radius R of the Ka-band reflective array with better non-diffraction effect is obtained by formula (4): 1-Airy Finally, considering the vortex characteristics, the radius R1 of the Ka-band non-diffraction Airy vortex reflection array is R 1-OAM ~R 1-Airy The final result value is obtained by iteration based on the near-field synthesis theory.

[0037] R refers to the radius of different reflection arrays corresponding to different modal values, and R refers to the radius of the R1 small circle of the reflection array where the Ka square ring patch is located and the radius of the R2 large circle of the reflection array where the X cross patch is located.

[0038] More specifically, iterate R 2-OAM , R 1-OAM , R 2-Airy , R 1-Airy The value methods include:

[0039] S1 selects the X-band circular reflector radius R2 and OAM mode order l according to the requirements. OAM1 ;

[0040] S2 is based on the R2 value selected in step S1 and l OAM1 , the elevation angle θ corresponding to the peak value of the X-band radiation pattern is obtained by formula (3): max ;

[0041] S3 is to achieve the same beam divergence angle for the X-band and Ka-band vortex beams, and let the elevation angle corresponding to the peak of the Ka-band radiation pattern be equal to θ max ;

[0042] S4 selects the Ka-band OAM mode order l according to the requirements OAM2 , according to θ max and l OAM2 The radius R of the Ka-band circular reflector array with only vortex characteristics without considering the non-diffracting Airy beam is obtained by formula (3): 1-OAM value;

[0043] S5 selects k according to the requirements rb , k m value;

[0044] S6 is based on the k selected in step S5 rb , k m The value and the R2 value selected in step S1 are used to obtain the focal distance z of the X-band non-diffracting Airy beam without considering the vortex electromagnetic wave through formula (4): f ;

[0045] S7 is to realize that the X-band and Ka-band non-diffracting Airy beams are focused at the same position, and the focal distance of the Ka-band non-diffracting Airy beam is equal to the z obtained in step S6. f ;

[0046] S8: z determined in step S7 f , k determined in step S5 m The value and R obtained in step S4 1-OAM , the Ka-band non-diffraction Airy beam k is obtained by formula (4): r ' b value;

[0047] S9 To enhance the non-diffraction focusing of the Airy beam by using the Ka-band reflectarray, a new k r ' b value, so that the new k r ' b The value is greater than k obtained in step S8 r ' b value;

[0048] S10: The new k selected in step S9 r ' b value, z determined in step S7 f and k determined in step S5 m The Ka-band reflector array radius R is obtained by formula (4): 1-Airy value;

[0049] S11 uses the near-field synthesis algorithm to calculate the R 1-Airy and R obtained in step S4 1-OAM , and the radius R1 of the Ka-band non-diffraction Airy vortex reflection array considering the vortex characteristics is obtained.

[0050] In the above process, k m Take 0.02~0.3;

[0051] k rb The following conditions must be met at the same time:

[0052] 5k m <k rb <60k m .

[0054] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0055] (1) The present invention provides an X / Ka dual-band non-diffraction Airy vortex electromagnetic wave antenna, which can simultaneously achieve phase compensation for incident electromagnetic waves in the Ka and X bands through the design of square ring patches and cross patches, and the reflected phase is flexibly adjustable and has strong applicability;

[0056] (2) The present invention provides a divergence angle design method for X / Ka dual-band dual-mode non-diffraction Airy vortex electromagnetic waves. By selecting a low-coupling X / Ka dual-band reflection unit and a suitable reflection surface area radius, the divergence angles of different modes can be made consistent;

[0057] (3) The present invention provides a specific structure and size design of the square ring patch and the cross patch, so that the reflection phase is flexibly adjustable and has strong applicability;

[0058] (4) The present invention provides a square ring patch and a cross patch method, which is beneficial to reducing the mutual coupling effect between the two frequency band units and can meet the polarization insensitivity characteristics. For different polarized incident waves, they have almost the same reflection phase and amplitude response.

[0059] (5) The antenna of the present invention is simple to manufacture and low in cost. It has the characteristics of self-healing and long-distance focusing. It not only provides an effective solution for the realization of long-distance Airy vortex beams, but is also suitable for the application of satellite-borne planar reflector arrays in the field of spacecraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is a three-dimensional overall schematic diagram of the X / Ka non-diffraction Airy vortex electromagnetic wave reflection array antenna of the present invention;

[0061] Figure 2 This is a schematic diagram of the phase distribution of the X / Ka non-diffraction Airy vortex electromagnetic wave reflection array antenna of the present invention;

[0062] Figure 3 A three-dimensional schematic diagram of a non-diffraction Airy vortex reflectarray unit of the present invention;

[0063] Figure 4 Schematic diagram of the structure of the reflective array unit of the present invention in top and side views;

[0064] Figure 5 The curve of the reflection phase of the X / Ka single-layer dual-frequency reflection unit according to the present invention varies with the corresponding size; wherein (a) is the reflection phase of the Ka band varies with l Ka (b) is the curve of the reflection phase of X-band with l x The change curve of

[0065] Figure 6The electric field distribution of the Airy vortex beam of the present invention; wherein (a) is the electric field amplitude distribution of the Airy vortex beam on the xoz plane, and (b) is the electric field amplitude distribution of the Airy vortex beam on the xy plane;

[0066] In the figure:

[0067] 1-feed source; 2-reflection array; 3-reflection array unit; 31-metal patch; 32-dielectric substrate; 33-air layer; 34-metal reflection floor. DETAILED DESCRIPTION

[0068] The following detailed description of the present invention will make the features and advantages of the present invention more clear and explicit.

[0069] The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise noted.

[0070] The present invention proposes an X / Ka dual-band non-diffraction Airy vortex electromagnetic wave antenna, comprising: a feed source and a reflection array; the reflection array faces the aperture radiation surface of the feed source, and each reflection sub-array is provided with a plurality of reflection array units for phase compensation. The X / Ka dual-band non-diffraction Airy vortex electromagnetic wave antenna feed source performs spatial feeding on the reflection array antenna, and the reflection array unit can achieve the same polarization characteristics as the feed source.

[0071] like Figure 1 The present invention provides an X / Ka dual-band non-diffraction Airy vortex electromagnetic wave antenna, comprising: a feed source 1 and a reflection array 2; the feed source 1 comprises an X-band feed source 101 and a Ka-band feed source 102, the X-band feed source 101 adopts oblique incidence feeding, and the Ka-band feed source 102 adopts positive feeding to reduce the influence of shielding; the reflection array 2 faces the aperture radiation surface of the feed source 1, and is divided into a central disk area and an outer annular area, and each reflection sub-array surface is provided with a plurality of reflection array units 3 for phase compensation. The reflection array units 3 are arranged periodically.

[0072] In a specific implementation, the area where the reflection array 2 is located can be circular, square, rectangular or other symmetrical shapes, and the aperture shape is not limited here and can be set according to actual needs.

[0073] In a specific implementation, the feed source 1 uses an X / Ka feed source to perform spatial feeding on the reflectarray antenna, wherein the reflectarray antenna uses a plurality of reflectarray units 3 with a phase compensation function. Further, it should be noted that the feed source 1 can be a linearly polarized feed source or a circularly polarized feed source, and the polarization mode of the feed source is not limited here and can be set according to actual application needs.

[0074] In a specific embodiment, the phase distribution of the X / Ka non-diffraction Airy vortex electromagnetic wave reflection array antenna is as follows: Figure 2 As shown, the X-band reflectarray has a non-diffraction Airy vortex electromagnetic wave reflection phase with a mode of +1, and the Ka-band reflectarray has a non-diffraction Airy vortex electromagnetic wave reflection phase with a mode of +4.

[0075] In a specific embodiment, Figure 3 The reflective array unit 3 is stacked in sequence in the direction toward the feed source 1 with a metal reflective floor 34, an air layer 33, a dielectric substrate 32 and a metal patch 31; the surface of the dielectric substrate 32 is etched with a metal patch 31, and its metal pattern is used for reflecting the phase; the metal patch 31 includes square ring patches 311 and cross patches 312 distributed at equal intervals; the square ring patch 311 has a phase compensation effect on the Ka-band incident electromagnetic wave emitted by the feed source 1, and the cross patch 312 has a phase compensation effect on the X-band incident electromagnetic wave emitted by the feed source 1.

[0076] In a specific implementation, the metal pattern of the square ring patch 311 includes: a square metal ring 3112 with a fixed outer frame and a square patch 3111 embedded in the square metal ring 3112 .

[0077] The reflective array unit 3 modulates the phase of the reflected electromagnetic wave by changing the pattern size of the metal patch 31, so that the antenna has vortex characteristics and Airy beam self-healing and long-distance focusing characteristics for the incident electromagnetic wave.

[0078] In a specific embodiment, Figure 4 The square ring patch 311 works in the Ka band, keeping the size of the outer frame l1 unchanged, and adjusting the inner side length l of the square ring Ka , to adjust the reflection phase of the square ring patch 311. l1 is 3.4 mm, l Ka It varies from 0.05λ1 to 1λ1, where λ1 is the wavelength of the incident wave in the Ka band in vacuum, and the side length of the square ring patch 3111 satisfies l2=k'·l Ka , k' is 0.5~1. The spacing d between square ring patch 311 units Ka Satisfies 0.2λ1~1λ1; the thickness of the dielectric substrate 32 is H s , the thickness of the air layer 33 is Ha , the thickness of the metal reflective floor 34 is H m .

[0079] In a specific implementation manner, the metal cross patch 312 operates in the X-band, and by adjusting the cross arm length l x Controls the reflection phase of the X-band, l x The value varies from 0.2λ2 to 0.6λ2, where λ2 is the wavelength of the X-band incident wave in vacuum, and the width w of the cross patch 312 is x Take 0.1mm~0.5mm; the spacing d between the metal cross patch 312 units X Satisfies 0.2λ2~1λ2, where d X =gd Ka , g is a positive integer.

[0080] Specifically, the reflection phase of the pattern of each patch is calculated by the following formula:

[0081]

[0082] Where Φ1 is the Airy phase distribution, l is the vortex mode number, is the azimuth corresponding to the (m,n)th reflection unit, k0 is the propagation constant, r mn is the distance from the (m,n)th reflection unit to the center of the reflection front, and F is the distance from the phase center of the feed antenna to the center of the reflection front. According to formula (1), the expected reflection phases of the Ka-band and X-band reflection units are obtained respectively. According to the expected reflection phases of the Ka-band and X-band, the inner side length l of the square metal ring 3112 is determined respectively. Ka and the arm length l of the cross patch 312 x , and then determine the size of the square ring patch 311 and the cross patch 312; when the expected reflection phases of the Ka band and the X band are obtained according to formula (1), is the azimuth angle corresponding to the (m,n)th square ring patch or cross patch.

[0083] The Airy phase distribution Φ1 of the reflection front is determined by the following formula:

[0084]

[0085] Where Ai(·) is the Airy function, b0 is a constant, r0 is the radius parameter of the main ring of the Airy beam, and the initial radius of the Airy vortex beam is R0=r0+(1+b0); r0=k m D, k m Take 0.02~0.3, D is the aperture size of the reflection array (2), satisfying b0=k rb / r0, where k rb is a constant greater than 0.

[0086] In a specific implementation, the square ring patch 311 is arranged in the central disk area with a radius of R1, and R1 is 520 mm; the cross patch 312 is specifically arranged in the large circle area with a radius of R2, and R2 is 700 mm. Therefore, the central disk area (i.e., the reflection array area with a radius smaller than R1) has both the square ring patch 311 and the cross patch 312, and the two units are arranged in an alternating periodic manner, and the position relationship is as follows: Figure 3 As shown, there is only a cross patch 312 in the outer annular area (ie, the reflection front area with a radius greater than R1 and less than R2).

[0087] In a specific implementation, the phases of the square ring patch 311 and the cross patch 312 are adjusted to make the vortex electromagnetic wave modes in different areas different; the radii R1 and R2 of different concentric circle areas are adjusted to make the beam divergence angles of different vortex electromagnetic wave modes consistent.

[0088] As an optional embodiment, the radii of the concentric circles of different areas of the reflection front are determined by the following formula:

[0089] When the undiffracted Airy beam is not considered, the radiation pattern of the circular reflector array is calculated as follows:

[0090]

[0091] Where R is the radius parameter of the circular reflection array, is the hypergeometric function, θ and Denote the elevation angle and azimuth angle respectively, and l is the OAM mode order. According to the requirements, select the X-band circular reflector array radius R2 = 700mm and the OAM mode order l OAM1 =1, and the elevation angle θ corresponding to the peak value of the X-band radiation pattern is obtained by formula (3) max =2.3°. In order to achieve the same beam divergence angle for the X-band and Ka-band vortex beams, the elevation angle corresponding to the peak of the Ka-band radiation pattern is set to 2.3°. The Ka-band OAM mode order l is selected according to the requirements. OAM2 =4, and the radius R of the Ka-band circular reflector array with only vortex characteristics without considering the non-diffracting Airy beam is obtained by formula (3): 1-OAM =490mm.

[0092] When the vortex beam is not considered, the radius of the non-diffraction Airy circular reflection array is calculated as follows:

[0093]

[0094] Where R is the radius parameter of the circular reflection array, z fis the ideal focal distance of the non-diffracting Airy beam when the vortex beam is not considered. k rb The larger the k is, the stronger the non-diffraction focusing property of the Airy beam is. rb =1.2, k m =0.088 and the determined X-band circular reflection array radius R2 =700 mm, the ideal focal distance z of the X-band non-diffracting Airy beam without considering the vortex electromagnetic wave can be obtained through formula (4): f =1.38m. In order to achieve the focusing of the X-band and Ka-band non-diffracting Airy beams at the same position, the ideal focal distance of the Ka-band non-diffracting Airy beam is equal to z f =1.38m. According to the determined z f , k m , R 1-OAM , the Ka-band non-diffraction Airy beam k is obtained by formula (4): r ' b =1.72.

[0095] The non-diffraction Airy vortex electromagnetic wave antenna combines the vortex characteristics and the non-diffraction Airy beam focusing characteristics to achieve a non-diffraction vortex beam. Considering that the larger the vortex beam mode order, the larger the beam divergence angle, the Ka-band reflector array needs to enhance the non-diffraction focusing effect of the Airy beam, so a larger k is selected. r ” b value, its value k r ” b =1.9>k r ' b According to the determined z f , k m , k r ” b , the radius R of the Ka-band reflective array with better non-diffraction effect is obtained by formula (4): 1-Airy =531.5mm. Finally, considering the vortex characteristics, the radius R1 of the Ka-band non-diffraction Airy vortex reflection array is R 1-OAM ~R 1-Airy The final result is obtained by iterating the near-field comprehensive algorithm, which is 520mm.

[0096] In addition, in one or more embodiments disclosed in the present invention, concentric circle areas of different radii are divided on each dielectric substrate; the square ring patch 311 and the cross patch 312 are located in concentric circle areas of different radii, and the two are arranged in a periodic pattern accordingly; the phases of the square ring patch 311 and the cross patch 312 are adjusted, and the vortex electromagnetic wave modes in different areas are different, so that the beam divergence angles of different vortex electromagnetic wave modes are consistent.

[0097] As an optional embodiment, two areas are set on the reflection array, namely the central disk area and the outer ring area. Combining formula (3) and formula (4), the radius R1 of the central disk area is determined to be 520 mm, the outer radius R2 of the outer ring area is determined to be 700 mm, the square ring patch 311 is only located in the inner circular area, and the cross patch 312 is located in both the central disk area and the outer circular area.

[0098] Specifically, Figure 5 The reflection phase-size curves of the unit at the two center frequencies of the X and Ka bands are given. The results show that the mutual coupling effect of the X-band cross unit and the Ka-band square unit is relatively small, and can achieve a phase range of 340° and 360° respectively, which can basically meet the phase distribution of the planar reflection array. Among them, the ordinate Phase represents the phase of the reflection coefficient.

[0099] Specifically, Figure 6 The electric field distribution of X / Ka dual-band Airy vortex beam is given. Figure 6 (a) is the electric field amplitude distribution of the Airy vortex beam on the xoz plane. The results show that both the X- and Ka-band vortex beams achieve non-diffraction focusing propagation near the 1.05m focus and have an equal focal radius of 47mm. Considering the divergence of the vortex beam and the limited aperture that only quasi-diffraction-free beams exist, the actual focal distance of the Airy vortex beam is always smaller than the ideal focal distance. Figure 6 (b) is the electric field distribution of the Airy vortex beam at the focus of the xy plane. The results show that the X- and Ka-band reflectarrays realize +1 and +4 mode vortex beams respectively, and their beam divergence angles are equal.

[0100] The present invention proposes an X / Ka dual-band non-diffraction Airy vortex electromagnetic wave antenna, which modulates the phase of the incident electromagnetic wave. The process is as follows: the X-band circularly polarized electromagnetic wave radiated by the circularly polarized feed source is irradiated onto the reflection array 2, and the square ring patch 311 located in the inner circular area is adjusted by adjusting the inner side length l of the square ring. Ka , the reflection phase of the Ka band can be adjusted to obtain the +4 mode vortex electromagnetic wave; the cross patch 312 located in the outer annular area and the inner circular area is adjusted by adjusting the cross arm length l x By controlling the reflection phase in the X-band, the vortex electromagnetic wave of the +1 mode can be obtained. By selecting different concentric circle radii of the reflection array, the beam divergence angles of the +1 and +4 modes can be made equal.

[0101] In summary, the embodiments of the present disclosure provide a non-diffraction Airy vortex reflector array antenna structure that is simple to process and operates in the X / Ka frequency band. The phase of the reflected electromagnetic wave is modulated by changing the size of the reflection unit, and the beam divergence angles of different modes are equal by selecting different concentric circle radii of the reflector array, so that the reflected electromagnetic beam generated by the antenna has vortex and non-diffraction focusing capabilities, and different modes have equal divergence angle characteristics.

[0102] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

[0103] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. An X / Ka dual-band non-diffraction Airy vortex electromagnetic wave antenna, characterized in that: It comprises a feed source (1) and a reflection array (2); The feed source (1) comprises an X-band feed source (101) and a Ka-band feed source (102), wherein the X-band feed source (101) adopts oblique incidence feeding, and the Ka-band feed source (102) adopts positive feeding; The reflection array (2) faces the aperture radiation surface of the feed source (1); the reflection array (2) comprises a plurality of periodically arranged square ring patches (311) and a plurality of periodically arranged cross patches (312); the square ring patches (311) are used to perform phase compensation on the Ka-band incident electromagnetic waves emitted by the feed source (1); and the cross patches (312) are used to perform phase compensation on the X-band incident electromagnetic waves emitted by the feed source (1).

2. The X / Ka dual-band non-diffraction Airy vortex electromagnetic wave antenna according to claim 1, characterized in that: The square ring patch (311) comprises a square metal ring (3112) and a square patch (3111) embedded in the square metal ring (3112).

3. The X / Ka dual-band non-diffraction Airy vortex electromagnetic wave antenna according to claim 2, characterized in that: Square metal ring (3112) inner side length l Ka =0.05λ1~1λ1, λ1 is the wavelength of the incident wave in the Ka band in vacuum; The reflection phase of the square ring patch (311) varies with the inner side length l of the square metal ring (3112). Ka increases with the increase of The side length of the square patch (3111) is l2 = k'·l Ka , k'=0.5~1.

4. The X / Ka dual-band non-diffraction Airy vortex electromagnetic wave antenna according to claim 1, characterized in that: The arm length l of the cross patch (312) X =0.2λ2~0.6λ2, λ2 is the wavelength of the X-band incident wave in vacuum; the reflection phase of the cross patch (312) varies with the arm length l of the cross patch (312). X increases with the increase of The width w of the cross patch (312) x It is 0.1mm~0.5mm.

5. The X / Ka dual-band non-diffraction Airy vortex electromagnetic wave antenna according to claim 2, characterized in that: Square metal ring (3112) inner side length l Ka and the arm length l of the cross patch (312) X They are determined according to the expected reflection phase of the Ka band and the expected reflection phase of the X band respectively.

6. The X / Ka dual-band non-diffraction Airy vortex electromagnetic wave antenna according to claim 5, characterized in that: Expected reflection phase ψ mn Calculate according to the following formula: Where Φ1 is the Airy phase distribution, l is the OAM mode order, is the azimuth angle corresponding to the (m,n)th patch, k0 is the propagation constant at different frequencies, r mn is the distance from the (m,n)th reflection unit to the center of the reflection front (2), and F is the distance from the phase center of the feed antenna to the center of the reflection front (2); The Airy phase distribution Φ1 is calculated according to the following formula: Where Ai(·) is the Airy function, b0 is a constant, r0 is the radius parameter of the main ring of the Airy beam, and the initial radius of the Airy vortex beam is R0=r0+(1+b0); r0=k m D, k m Take 0.02~0.3, D is the aperture size of the reflection array (2), satisfying b0=k rb / r0, where k rb Is a positive number.

7. The X / Ka dual-band non-diffraction Airy vortex electromagnetic wave antenna according to claim 1, characterized in that: The area where the square ring patch (311) is located is recorded as the first area, and the area where the cross patch (312) is located is recorded as the second area; The first area is a circle centered on the reflection front (2), namely the central disk area, and the radius of the circle is denoted as R1; The second area is a circle centered on the reflection front (2), and the radius of the circle is R2; 1 / 2D≥R2>R1>0; D is the aperture size of the reflection array (2); In the first area, there are both square ring patches (311) and cross patches (312); In the second region outside the first region, ie, the outer annular region, only cross patches (312) exist.

8. The X / Ka dual-band non-diffraction Airy vortex electromagnetic wave antenna according to claim 1, characterized in that: R1 and R2 are determined according to the following formula: When the undiffracted Airy beam is not considered, the radiation pattern of the circular reflector array is calculated as follows: Where R is the radius parameter of the circular reflection array, is the hypergeometric function, θ and denote the elevation angle and azimuth angle respectively, l is the OAM mode order; based on the same beam divergence angle in the X and Ka bands, according to the given OAM mode order, the circular reflector radius R corresponding to the X and Ka bands is obtained without considering the non-diffracting Airy beam. 2-OAM , R 1-OAM value; When the vortex beam is not considered, the radius of the non-diffraction Airy circular reflection array is calculated as follows: Where R is the radius parameter of the circular reflection array, z f is the ideal focal distance of the non-diffracting Airy beam when the vortex beam is not considered; based on the X and Ka bands z f The same value condition, according to the given k rb , k m The circular reflection array radius R corresponding to the X and Ka bands without considering the vortex electromagnetic wave is obtained. 2-Airy , R 1-Airy value; Combining Formula 1 and Formula 2, iterate R 2-OAM , R 1-OAM , R 2-Airy , R 1-Airy The values ​​of R2 and R1 of the circular reflection surface in the X and Ka bands are finally determined by considering both the undiffracted Airy beam and the vortex beam.

9. The X / Ka dual-band non-diffraction Airy vortex electromagnetic wave antenna according to claim 8, characterized in that: Combining Formula 1 and Formula 2, iterate R 2-OAM , R 1-OAM , R 2-Airy , R 1-Airy The value methods include: S1 selects the X-band circular reflector radius R2 and OAM mode order l according to the requirements. OAM1 ; S2 is based on the R2 value selected in step S1 and l OAM1 , the elevation angle θ corresponding to the peak value of the X-band radiation pattern is obtained by formula 1 max ; S3 is to achieve the same beam divergence angle for the X-band and Ka-band vortex beams, and let the elevation angle corresponding to the peak of the Ka-band radiation pattern be equal to θ max ; S4 selects the Ka-band OAM mode order l according to the requirements OAM2 , according to θ max and l OAM2 The radius R of the Ka-band circular reflector array with only vortex characteristics without considering the non-diffracting Airy beam is obtained by formula 1: 1-OAM value; S5 selects k according to the requirements rb , k m value; S6 is based on the k selected in step S5 rb , k m The value and the R2 value selected in step S1 are used to obtain the focal distance z of the X-band non-diffracting Airy beam without considering the vortex electromagnetic wave through formula 2. f ; S7 is to realize that the X-band and Ka-band non-diffracting Airy beams are focused at the same position, and the focal distance of the Ka-band non-diffracting Airy beam is equal to the z obtained in step S6. f ; S8: z determined in step S7 f , k determined in step S5 m The value and R obtained in step S4 1-OAM , the Ka-band non-diffraction Airy beam k is obtained by formula 2 r ' b value; S9 To enhance the non-diffraction focusing of the Airy beam by using the Ka-band reflectarray, a new k r ' b value, so that the new k r ' b The value is greater than k obtained in step S8 r ' b value; S10: The new k selected in step S9 r ' b value, z determined in step S7 f and k determined in step S5 m The Ka-band reflector array radius R is obtained by formula 2. 1-Airy value; S11 uses the near-field synthesis algorithm to calculate the R 1-Airy and R obtained in step S4 1-OAM , and the radius R1 of the Ka-band non-diffraction Airy vortex reflection array considering the vortex characteristics is obtained.

10. The X / Ka dual-band non-diffraction Airy vortex electromagnetic wave antenna according to claim 9, characterized in that: k m Take 0.02~0.3; k rb The following conditions must be met at the same time:

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