阅读说明：本技术 用于产生多模态oam波束的紧凑型顺序旋转同心均匀圆阵列 (Compact sequential rotating concentric uniform circular array for generating multi-modal OAM beams ) 是由 胡俊 张田子 吴文 张琪芸 于 2021-08-22 设计创作，主要内容包括：本发明公开了一种用于产生多模态OAM波束的紧凑型顺序旋转同心均匀圆阵列,单个均匀圆阵列采用等腰直角三角形圆极化贴片单元以顺序旋转的方式均匀排列,在结构上提供连续的相位差来产生OAM波束可省略馈电网络中移相器,采用CUCAs在阵列结构紧凑的条件下可以同时产生多种模式的OAM波。本发明所提出的带切角的等腰直角三角形圆极化单元使阵列结构更加紧凑；本发明可用于无线通信来提高频谱效率或用于雷达成像来实现高分辨率的方位角成像。(The invention discloses a compact sequential rotation concentric uniform circular array for generating multi-mode OAM wave beams, wherein a single uniform circular array adopts isosceles right triangle circular polarization patch units which are uniformly arranged in a sequential rotation mode, continuous phase difference is provided structurally to generate OAM wave beams, a phase shifter in a feed network can be omitted, and CUCAs is adopted to generate OAM wave in multiple modes under the condition of compact array structure. The isosceles right triangle circular polarization unit with the cutting angles provided by the invention enables the array structure to be more compact; the invention can be used for wireless communication to improve spectral efficiency or for radar imaging to achieve high resolution azimuthal imaging.)

1. A compact sequential rotation concentric uniform circular array for generating multi-mode OAM wave beams is characterized in that a single uniform circular array is uniformly arranged in a sequential rotation mode by adopting isosceles right triangle circular polarization patch units, and a plurality of uniform circular arrays are concentrically arranged; the isosceles right triangle circular polarization patch unit with the cutting angles is formed by symmetrically cutting off two base angles from an isosceles right triangle patch.

2. The compact sequential rotational concentric uniform circular array for generating multi-modal OAM beams as recited in claim 1, wherein said isosceles right triangle microstrip patch elements with chamfers are divided according to feed position into:

the isosceles right triangle hypotenuse is horizontally placed, the two right-angle sides are located above the hypotenuse, when the feed point is located on the left side, the isosceles right triangle microstrip patch with the cutting angle is a left circular polarization unit, and when the feed point is located on the right side, the isosceles right triangle microstrip patch with the cutting angle is a right circular polarization unit.

3. The compact sequential rotation concentric uniform circular array for generating multi-modal OAM beams as recited in claim 2, wherein if an OAM wave with a mode l is to be generated, the number N of cells of UCA shall satisfy N/2> | l |, when l >0, N circularly polarized cells may be employed to rotate clockwise 0 °, 2 π l/N °, 4 π l/N °, … …, 2 π l (N-1)/N °, respectively, if the cells are left circularly polarized cells, then sequentially arranged counterclockwise as UCA, if the cells are right circularly polarized cells, then sequentially arranged clockwise as UCA; both cases can generate OAM waves with l >0 mode;

on the contrary, according to the clockwise rotation angle of the units, the left circularly polarized units are sequentially arranged clockwise to form the UCA or the right circularly polarized units are sequentially arranged counterclockwise to form the UCA, and both the i <0 mode OAM wave can be generated.

4. The compact sequential rotated concentric uniform circular array for generation of multimodal OAM beams as recited in claim 3, wherein a beam generated with an array of left circularly polarized elements is LHCP near a center frequency and a beam generated with an array of right circularly polarized elements is RHCP near a center frequency.

5. The compact sequentially rotated concentric uniform circular array for generation of multi-modal OAM beams as recited in claim 3, wherein a left circularly polarized cell's sequentially rotated UCA is employed to generate a-1 mode OAM wave, or a right circularly polarized cell's sequentially rotated UCA is employed to generate a +1 mode OAM wave.

6. The compact sequential rotational concentric uniform circular array for generating multi-modal OAM beams as recited in claim 3, wherein an inner four LHCP units and an outer eight LHCP units are employed in sequential rotational arrangement as CUCAs, simultaneously radiating-1, -2 modes of OAM waves.

7. The compact sequential rotational concentric uniform circular array for generating multi-modal OAM beams as recited in claim 6, wherein said circularly polarized patch elements are printed on the upper surface of said dielectric substrate, the UCA radii of the inner and outer circles are 0.3 λ 0 and 0.7 λ 0, respectively, λ 0 is the free space wavelength with frequency of 9.2GHz, the lower surface of said dielectric substrate is a ground plane, and the antenna employs coaxial feeding.

Technical Field

The invention relates to the field of wireless communication, in particular to a compact sequential rotation concentric uniform circular array for generating multi-mode OAM wave beams.

Background

With the rapid development of wireless communication, the explosive capacity demand brings challenges to the traditional wireless communication resources. The electromagnetic wave carrying OAM has infinite topological loads orthogonal to each other, and can be used as a new degree of freedom to improve the spectrum efficiency of wireless communication. Besides the application in wireless communication, the application of the multi-modal OAM antenna in radar imaging can realize azimuth imaging without relative motion between radar and a target. In addition, OAM may also be used for medical imaging, rotating object detection, and the like.

However, in the field of OAM applications, it is mostly required to implement multi-mode OAM wave radiation, so that the premise of implementing its application value is the generation of OAM beams. There are several typical methods currently available to generate OAM beams, such as Spiral Phase Plate (SPP), circular traveling wave antenna, super surface and UCA. The UCA is a relatively common OAM antenna, and generally, continuous phase feeding to array elements can easily generate OAM waves of various modes, but phase shifting between elements generally needs a complex feeding network to implement, and generating a high-mode OAM beam requires more antenna elements, resulting in a larger antenna size.

Disclosure of Invention

An object of the present invention is to provide a compact sequentially rotated concentric uniform circular array for generating multi-mode OAM beams, to simultaneously generate multi-mode OAM waves with a more compact and simple antenna structure.

The technical solution for realizing the purpose of the invention is as follows: a compact sequential rotation concentric uniform circular array for generating multi-mode OAM wave beams, wherein a single uniform circular array is uniformly arranged in a sequential rotation mode by adopting isosceles right triangle circular polarization patch units, and a plurality of uniform circular arrays are concentrically arranged; the isosceles right triangle circular polarization patch unit with the cutting angles is formed by symmetrically cutting off two base angles from an isosceles right triangle patch.

Further, the isosceles right triangle microstrip patch with the chamfer is divided into:

the isosceles right triangle hypotenuse is horizontally placed, the two right-angle sides are located above the hypotenuse, when the feed point is located on the left side, the isosceles right triangle microstrip patch with the cutting angle is a left circular polarization unit, and when the feed point is located on the right side, the isosceles right triangle microstrip patch with the cutting angle is a right circular polarization unit.

Further, if an OAM wave with a mode of l is to be generated, the number N of the UCA units should satisfy N/2> | l |, when l >0, N circularly polarized units may be adopted to rotate clockwise 0 °, 2 π l/N °, 4 π l/N °, … …, 2 π l (N-1)/N °, respectively, if the unit is a left circularly polarized unit, the UCA is sequentially arranged counterclockwise, and if the unit is a right circularly polarized unit, the UCA is sequentially arranged clockwise; both cases can generate OAM waves with l >0 mode;

on the contrary, according to the clockwise rotation angle of the units, the left circular polarization units are sequentially arranged clockwise to form the UCA or the right circular polarization units are sequentially arranged counterclockwise to form the UCA, and both OAM waves of a mode l <0 can be generated.

Further, the beam generated using the array of left circularly polarized elements is LHCP near the center frequency and the beam generated using the array of right circularly polarized elements is RHCP near the center frequency.

Further, the OAM wave of the-1 mode is generated by sequentially rotating the UCA with the left circular polarized unit, or the OAM wave of the +1 mode is generated by sequentially rotating the UCA with the right circular polarized unit.

Furthermore, four LHCP units at the inner circle and eight LHCP units at the outer circle are sequentially arranged in a rotating mode to form CUCAs, and OAM waves in a-1 mode and a-2 mode are radiated at the same time.

Further, the circularly polarized patch unit is printed on the upper surface of the dielectric substrate, the radius of UCA of the inner and outer circles is 0.3 lambda 0 and 0.7 lambda 0 respectively, lambda 0 is free space wavelength with the frequency of 9.2GHz, the lower surface of the dielectric substrate is a ground plate, and the antenna adopts coaxial feed.

Compared with the prior art, the invention has the following remarkable advantages: (1) the invention generates OAM waves of various modes by arranging circularly polarized units into UCAs in a sequential rotation mode and omits the design of phase shifters in a feed network; (2) the CUCAs structure is adopted to generate a plurality of modes of OAM waves, so that the array has compactness; (3) the isosceles right triangle circular polarization microstrip patch unit with the cutting angle is adopted, so that the array is more compact.

Drawings

Fig. 1 is a schematic diagram of LHCP units and their generation of-1 mode OAM wave sequentially rotating UCAs and RHCP units and their generation of +1 mode OAM wave sequentially rotating UCAs.

FIG. 2 is a front view of CUCAs capable of simultaneously radiating-1 and-2 mode OAM waves based on LHCP unit

Fig. 3 is a side view of CUCAs based LHCP units that can radiate-1, -2 mode OAM waves simultaneously.

FIG. 4 is the S parameter of-1, -2 mode OAM waves radiated by CUCAs

FIG. 5 is a-1, -2 mode OAM wave far-field directional diagram of CUCAs radiation

Detailed Description

To simplify the feed network of the UCA while reducing the array size to produce multiple modes of Orbital Angular Momentum (OAM) beams, the present invention proposes a compact sequentially rotated Concentric Uniform Circular Array (CUCAs). The CUCAs can be used for simultaneously radiating OAM wave beams in multiple modes, the design of a phase shifter in a feed network is omitted, and the array has the characteristic of compactness.

A compact sequential rotation concentric uniform circular array for generating multi-mode OAM wave beams in an X wave band is concentrically arranged by a plurality of uniform circular arrays, and a single uniform circular array is uniformly arranged in a sequential rotation mode by adopting a circular polarization unit, thereby providing continuous phase shift structurally and realizing OAM wave radiation in various modes under the condition of no phase shifter in a feed network; and the CUCAs can radiate a plurality of OAM modes simultaneously, and the array has compactness.

The circular polarization unit adopts isosceles right triangle circular polarization patches with cutting angles, and two base angles are symmetrically cut off from the isosceles right triangle patches;

the isosceles right-angle triangular microstrip patch with the cutting angle is divided into the following parts according to the feed position:

the isosceles right triangle hypotenuse is horizontally placed, the two right-angle sides are located above the hypotenuse, when the feed point is located on the left side, the isosceles right triangle microstrip patch with the cutting angle is a left circular polarization unit, and when the feed point is located on the right side, the isosceles right triangle microstrip patch with the cutting angle is a right circular polarization unit.

If an OAM wave with a mode of l is to be generated, the number N of the elements of UCA should satisfy N/2> | l |, when l >0, N circularly polarized elements may be adopted to rotate clockwise 0 °, 2 π l/N °, 4 π l/N °, … …, 2 π l (N-1)/N °, respectively, and if the elements are left circularly polarized (LHCP), they are sequentially arranged counterclockwise to form UCA, and if the elements are right circularly polarized (RHCP), they are sequentially arranged clockwise to form UCA. Both cases can generate OAM waves in l >0 mode. On the contrary, according to the clockwise rotation angle of the above units, the OAM wave of the l <0 mode can be generated by sequentially arranging the LHCP units clockwise to the UCA or sequentially arranging the RHCP units counterclockwise to the UCA. Further, the beam generated using the array of LHCP elements is LHCP near a center frequency and the beam generated using the array of RHCP elements is RHCP near the center frequency.

The isosceles right-angled triangle circularly polarized microstrip antenna with the cutting angle is optimized by adopting Characteristic Mode Analysis (CMA). Firstly, two acute angles are symmetrically cut off from an isosceles right triangle microstrip patch, the Mode Significance (MS) of two orthogonal main modes of the antenna at a central frequency point is the same by adjusting the size of the cut angles, the difference of Characteristic Angles (CA) is about 90 degrees, and the two orthogonal characteristic modes can be simultaneously excited by finding a proper feed position to realize LHCP or RHCP radiation of the antenna. The structural characteristics of the unit enable the array structure of OAM waves in a-1 mode generated by sequentially rotating UCA by adopting the LHCP unit or OAM waves in a +1 mode generated by sequentially rotating UCA by adopting the RHCP unit to be more compact.

The following is a detailed description of the compact sequential rotating CUCAs for generating multi-mode OAM beams provided by the present invention:

firstly, because the microstrip antenna has the characteristics of low profile, low cost and wide bandwidth, and is widely applied to a microwave frequency band, the invention provides an isosceles right triangle circular polarization microstrip antenna with a cutting angle as a basic array element of CUCAs. Specifically, a multilayer solver in CST is used for realizing the characteristic mode analysis of the circularly polarized antenna unit, two main characteristic molds of the unit have orthogonality, the size of a corner cut is optimized by analyzing the simulation result of the Modal Significance (MS) and the Characteristic Angle (CA) of the characteristic mold, the MS of two effective characteristic molds can be overlapped at the central frequency of the unit, the difference between the characteristic angles of the two characteristic molds at the frequency point is 90 degrees, and the circularly polarized radiation can be realized through a proper feed position.

Secondly, based on the above circular polarized unit, we use the sequentially rotated UCAs of four LHCP units to generate OAM waves in the-1 mode, or use the sequentially rotated UCAs of four RHCP units to generate OAM waves in the +1 mode, so that the array has a compact structure.

Finally, according to the foregoing, the larger the number of elements, the higher the OAM modal value that can be generated, we can place the UCA generating low-order mode OAM waves in the center of the antenna, such as the LHCP four-element UCA generating-1 mode or the RHCP four-element UCA generating +1 mode, and then arrange more elements in a sequentially rotating manner on the outer circle to generate the UCA generating high-order mode, so that when the coupling degree between the array elements meets the requirement, multiple CUCAs can simultaneously radiate OAM waves of multiple modes in the same frequency band in a compact array structure by using the same antenna aperture, and because different modes are orthogonal to each other, the antenna can be used for wireless communication to improve spectral efficiency or for radar imaging to realize azimuth imaging and the like without relative motion between the target and the radar.

The invention will be further elucidated with reference to the drawings and specific embodiments, it being understood that these examples are intended to illustrate the invention only and are not intended to limit the scope of the invention.

Examples

As shown in fig. 1, in fig. 1(a), fig. 1(c) are LHCP and RHCP antenna elements, respectively, four identical LHCP elements or RHCP elements are used, respectively, rotated clockwise by 0 °, 90 °, 180 ° and 270 °, and arranged in a UCA in a clockwise direction, as shown in fig. 1(b), and fig. 1(d) can generate OAM waves in-1 and +1 modes, respectively, while the array is compact.

As shown in fig. 2 and 3, OAM waves of-1 mode and-2 mode can be radiated simultaneously by adopting four LHCP units at the inner circle and eight LHCP units at the outer circle which are arranged in sequence and rotated to CUCAs. The radiation unit 1 is printed on the upper surface of a Rogers RT5880 dielectric substrate 2 with the thickness of 2mm, the dielectric constant of the dielectric substrate 2 is 2.2, the loss tangent is 0.0009, the radius of UCA of the inner circle and the outer circle is 0.3 lambda 0 and 0.7 lambda 0 respectively, lambda 0 is free space wavelength with the frequency of 9.2GHz, the lower surface of the dielectric substrate 2 is a grounding plate 3 with the thickness of 2mm, the overall size of the antenna is pi 40mm x 4mm, and coaxial feeding 4 is adopted.

In FIG. 4, Active1_ S₁₁Active2_ S, the reflection coefficient of one of the cells when the inner four cells of the CUCAs in FIG. 2 are simultaneously fed₁₁And the reflection coefficient of one of the eight outer units when the eight outer units are simultaneously fed. It can be seen from the figure that the impedance bandwidth of the inner circle unit is narrow because there is some coupling between the array elements, but the whole array can still work in a wider impedance bandwidth, and its-10 dB impedance bandwidth is 11% (8.7-9.7 GHz).

Fig. 5 is a far-field pattern of-1 and-2 mode OAM waves generated by CUCAs at 9.2GHz in fig. 2, the center-notched far-field pattern indicating the effectiveness of OAM generation. Wherein the main lobe gain of the-1 mode beam is 5.47dBi and the main lobe gain of the-2 mode beam is 8.24dBi, and the main lobe gain of the-2 mode beam is higher than that of the-1 mode because the array of the-2 mode has more array elements and larger array radius.