Offset-fed millimeter-wave broadband OAM reflecting array antenna

Abstract

The positive-feed excited millimeter-wave broadband OAM reflecting array antenna belongs to the field of microwave technology. It includes a dielectric substrate, a ground plane, an air layer, a feed source, and a microstrip split-ring reflecting array; the microstrip split-ring reflecting array includes n split-ring units, and the n split-ring units are uniformly arranged on the upper surface of the dielectric substrate according to a certain relationship, and the microstrip split-ring reflecting array faces the feed source; each split-ring unit contains a rectangular ring composed of 4 metal strip lines; the back of the dielectric substrate is the air layer, and the back of the air layer is the ground plane. By adjusting the number and length of the metal strip line rectangular rings in the microstrip split-ring reflecting array antenna, phase modulation can be performed and the gain can be increased, achieving effects such as generating vortex beams with high mode numbers. It is easy to manufacture, has a low cost, and can be widely used in 5G millimeter-wave communication.

Description

Technical Field

[0001] The present invention belongs to the field of microwave technology, and particularly relates to a front-fed excited millimeter-wave broadband OAM reflecting array antenna. Background Art

[0002] Traditional OAM antennas include circular array antennas, spiral phase plates, circular traveling wave antennas, etc. However, circular array antennas are only suitable for generating low-order vortex beams. For high-order vortex beams, not only more array elements are required, but the design of the feeding network is also very complex; the spiral phase plate controls the optical path difference of the incident wave by adjusting the thickness of the dielectric substrate to achieve a spiral distribution of the reflection wave phase on the aperture surface. Obviously, this method has very high requirements for the processing technology of the dielectric substrate, resulting in a high cost; the principle of the circular traveling wave antenna is similar to that of the circular array antenna, but in the case of a fixed size, the number of generated modes is single and the gain is low.

[0003] Combining the characteristics of the above three antennas, the reflecting array antenna came into being. The reflecting array antenna uses air-coupled feeding, eliminating the complex feeding network design. By changing the reflection phase of each unit on the aperture surface, a vortex beam with high gain, high purity, and high mode number can be generated. Summary of the Invention

[0004] The purpose of the present invention is to provide a front-fed excited millimeter-wave (26 GHz) broadband OAM reflecting array antenna with the performance of high gain, high purity, and high mode number vortex waves, which can be widely applied to wireless communication technology.

[0005] The present invention includes a dielectric substrate, a ground plane, an air layer, a feed source, and a microstrip split-ring reflecting array; the microstrip split-ring reflecting array includes n split-ring units, and the n split-ring units are uniformly arranged on the upper surface of the dielectric substrate according to a certain relationship, and the microstrip split-ring reflecting array faces the feed source; each split-ring unit includes a rectangular ring composed of 4 metal strip lines; the back of the dielectric substrate is an air layer, and the back of the air layer is a ground plane.

[0006] The reflection phase delay is realized by changing the size of the metal of the microstrip split-ring itself, and the required compensation phase is obtained from the phase distribution according to the aperture field superposition method. According to the phase shift curve of the split-ring unit, the size of the metal strip line of the corresponding split-ring is obtained, so that split-ring units with different sizes are uniformly distributed on the dielectric board.

[0007] For the microstrip split ring, each of the 4 rectangular split rings of each microstrip split ring unit is composed of m segments of rectangular microstrip lines, and the number of rectangular microstrip lines extends step by step as 3, 4, 5...; taking half of the length L of the central metal strip line as the reference, the lengths of the m segments of rectangles spiraling inwards starting from the top end of the central metal strip line are k1*L, k2*L, k3*L, k4*L,...km*L respectively; where k1, k2, k3, k4...km*L are obtained by comparing the reflection phase and amplitude changes of the open rectangular ring unit for different values through HFSS simulation, k1 = 0.8 - 1.0, k2 = 0.7 - 0.9, k3 = 0.4 - 0.6, k4 = 0.5 - 0.7...; the width of the metal strip line is w = 0.1 - 0.3 mm.

[0008] The dielectric substrate uses a high-performance low-loss millimeter-wave dielectric substrate. The dielectric constant of the dielectric substrate is 3.0 - 4.0, the contour of the dielectric substrate is circular, and the thickness of the dielectric substrate is H1 = 0.8 - 1.2 mm; the outer contour of the microstrip split ring unit is square, and the side length P of the square contour is 5.5 - 6 mm; the thickness of the air layer is H2 = 1.0 - 2.0 mm.

[0009] The feed uses a conical corrugated horn antenna for normal feed excitation, and the beam direction is perpendicular to the microstrip split ring array antenna. The distance between the conical corrugated horn antenna feed and the array reflector is 100 - 120 mm.

[0010] The microstrip split ring unit is etched on one side of the dielectric substrate using copper plating technology, and the copper plating thickness is 0.03 - 0.12 mm.

[0011] The reflection array antenna can realize vortex beams with different mode numbers, where the mode number l = 1, 2, 3, 4..., and has good bandwidth, that is, while maintaining a certain bandwidth, it can radiate OAM beams with multiple different mode numbers and maintain a high purity ratio.

[0012] The composition method of the microstrip split ring reflection array antenna is to obtain the required compensation phase from the phase field distribution of the desired beam according to the aperture field superposition method. That is, the compensation phase of the (m,n)th unit. Assuming the feed position vector is The position vector of the (m,n)th unit is The target beam direction should satisfy By adjusting to make it satisfy the above formula, a reflection array with an arbitrarily oriented main beam is designed; then, according to the phase shift curve of the microstrip split ring unit, the corresponding dimensions of the open microstrip ring unit along the unit are obtained.

[0013] Compared with traditional microstrip reflectarray antennas, the present invention adjusts the number of metal strip rectangular rings in the microstrip split-ring reflectarray antenna, and the length can be phase-adjusted to improve the gain, achieving effects such as generating vortex beams with high mode numbers. The present invention can obtain radiation performance with high gain and low side lobes. The structure of the present invention is simple, easy to process, and has a low cost, and can be widely used in 5G millimeter-wave communication. The application prospect of the present invention is very broad. Description of the Drawings

[0014] Figure 1 It is the overall composition structure diagram of the embodiment of the present invention;

[0015] Figure 2 It is the front view of the microstrip split-ring unit structure of the embodiment of the present invention;

[0016] Figure 3 It is the side view of the microstrip split-ring unit structure of the embodiment of the present invention;

[0017] Figure 4 It is the relationship curve between the length of each section of the strip line of the microstrip split-ring unit and half of the length L of the central metal strip line;

[0018] Figure 5 It is the relationship curve between the reflection phase of the microstrip split-ring unit and the incident angle;

[0019] Figure 6 A phase observation plane is set at z = 300 mm to obtain the radiation pattern distribution;

[0020] Figure 7 A phase observation plane is set at z = 300 mm to obtain the electric field phase distribution;

[0021] Figure 8 It is the situation of the mode purity ratio;

[0022] Figure 9 It is the phase distribution and mode purity at different frequencies. Detailed Implementation Manner

[0023] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following embodiments will further illustrate the present invention in conjunction with the drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. On the contrary, the present invention covers any alternatives, modifications, equivalent methods and solutions made within the spirit and scope of the present invention defined by the claims. Further, in order to enable the public to have a better understanding of the present invention, some specific details are described in detail in the following detailed description of the present invention. Those skilled in the art can fully understand the present invention without the description of these details.

[0024] Such as Figures 1 to 3, in the embodiment of the present invention, a dielectric substrate 1 is provided. A microstrip split-ring reflector array 4 is provided on the upper surface of the dielectric substrate 1. The back surface of the dielectric substrate is an air layer 2, and the back surface of the air layer is a ground plane 3. The dielectric substrate and the ground plane are circular in contour; the microstrip split-ring reflector arrays 4 arranged according to a certain relationship are distributed in a certain size on the upper surface, and the surface of the microstrip split-ring reflector array faces the conical corrugated horn feed 5. By changing the size of the metal of the microstrip split-ring itself, the reflection phase delay is realized, and the required compensation phase is obtained from the phase distribution according to the aperture field superposition method. The size of the metal strip line of the corresponding split ring is obtained according to the phase shift curve of the split ring unit.

[0025] The 4 rectangular split rings of the microstrip split-ring unit are all composed of m segments of rectangular microstrip lines, and the number of microstrip lines extends step by step according to 3, 4, 5...; taking half of the length L of the central metal strip line as the reference, the lengths of the m segments of rectangles spiraling inwards from the top of the central metal strip line are k1*L, k2*L, k3*L, k4*L,..., km*L respectively.

[0026] The dielectric substrate uses a high-performance low-loss millimeter-wave dielectric substrate. The dielectric constant of the dielectric substrate is 3.0 - 4.0. The contour of the dielectric substrate is circular, and the thickness of the dielectric substrate is H1 = 0.8 - 1.2 mm; the outer contour of the microstrip split-ring unit is square, and the side length P of the square contour is 5.5 - 6 mm; the thickness of the air layer is H2 = 1.0 - 2.0 mm.

[0027] The feed uses a conical corrugated horn antenna for positive feed excitation, and the beam direction is perpendicular to the microstrip split-ring array antenna. The distance between the conical corrugated horn antenna feed and the array reflector is 100 - 120 mm.

[0028] The reflector array antenna can realize vortex beams with different mode numbers, where the mode number l = 1, 2, 3, 4..., and has a good bandwidth. That is, while maintaining a certain bandwidth, it can radiate multiple OAM beams with different mode numbers and maintain a high purity ratio.

[0029] The composition method of the microstrip split-ring reflector array antenna obtains the required compensation phase from the phase field distribution of the required beam according to the aperture field superposition method. That is, the compensation phase of the (m, n)th unit. Assuming the feed position vector is The position vector of the (m, n)th unit is The target beam direction should satisfy By adjusting to make it satisfy the above formula, a reflector array with an arbitrarily oriented main beam is designed; according to the phase shift curve of the microstrip split-ring unit, the size of the corresponding open microstrip ring unit along the unit is obtained.

[0030] As a preferred solution, the overall radius of the antenna in the embodiment is 60.9 mm, the thickness is 2.5 mm, the dielectric substrate uses Rossgers RO4003, the dielectric constant εr = 3.55, the loss tangent σ = 0.0027, the thickness h of the dielectric substrate is 1 mm, the thickness of the air layer is 1.5 mm, and the mode number l = 2. The side length P of the square contour of the microstrip split-ring unit is 5.8 mm, and n = 351 microstrip split-ring units are placed on the dielectric substrate.

[0031] In the embodiment of the present invention, the feed source used is a pyramidal horn. The size contours of the 26 GHz horn in the Cartesian coordinate system are 26 mm, 19.5 mm, and 27.4 mm. The gain at the center frequency of 38 GHz is 15.4 dBi, the covered bandwidth exceeds 4 GHz, and the performance is good at the center frequency. The E-plane and H-plane of the horn antenna have good symmetry, and the half-power beam width is about 30°.

[0032] The preferred embodiment of the present invention is described in detail as follows:

[0033] In the embodiment, a four-section microstrip line split-ring unit structure is adopted, that is, m = 4. The optimized dimensions of the central metal strip line and the four-section rectangular microstrip line structure unit are as follows: the range of the central metal strip line L is 1 - 2.8 mm, and the lengths of the m-section rectangles spiraling inward from the top of the central metal strip line are k0.9*L, 0.8*L, 0.5*L, and 0.6*L respectively; the widths of the metal strip lines are the same, all w = 0.2 mm.

[0034] As a preferred solution, the focal diameter ratio F / D = 1 is the best feed source position, the split-ring unit period P = 5.8 mm, the radiation radius D = 115 mm, and the distance between the pyramidal horn feed 5 and the array reflector 4 is 112.5 mm. A single-feed reflector array is designed using a four-section microstrip line unit structure and is positively fed and excited by a pyramidal horn antenna.

[0035] See Figure 4 , the microstrip split-ring unit shows an excellent linear relationship with the phase shift within the range of L from 1 to 2.8 mm, and satisfies a phase difference of more than 360°.

[0036] See Figure 5 , and the curve of the reflection phase of the microstrip split-ring unit versus the incident angle is given.

[0037] See Figure 6 , in HFSS, the full-wave simulation analysis of the above four types of antennas is carried out using the FEBI boundary condition, and a phase observation plane is set at z = 300 mm to obtain the radiation pattern and the electric field phase distribution, and the results are as Figure 6As shown. From its far-field radiation pattern, it can be seen that the maximum gain is 19.4 dB, its radiation energy is distributed in a ring shape, and there is an energy hole in the central propagation direction; observing the electric field phase distribution, it can be seen that its electric field phase presents an obvious spiral structure without obvious distortion. The designed reflectarray antenna can better realize vortex beams with different mode numbers.

[0038] See Figure 7 , the main mode purity ratios of the reflectarray antenna reach 97.3% respectively, while the purity ratios of other modes except the main mode only account for a very small proportion. Therefore, the designed orbital angular momentum reflectarray antenna can better radiate vortex beams.

[0039] See Figure 8 and 9 , as the frequency changes, the electric field phase still maintains a good vortex distribution. At 25 GHz, the first-order mode purity ratio reaches 94.6%; at 27 GHz, the first-order mode purity ratio reaches 87.3%. It can be seen that the designed OAM antenna has good bandwidth.

[0040] Table 1 shows the influence characteristics of the manufacturing and processing errors of the present invention on the antenna.

[0041] Table 1

[0042]

[0043] Note: The data in Table 1 already has a certain redundancy, and there is a certain correlation between the parameters. The structural parameters can be optimized according to needs to complete special designs.

[0044] In summary, the front-fed excited millimeter-wave broadband OAM reflectarray antenna of the present invention is composed of n open-loop units. The n open-loop units are evenly arranged on the upper surface of the dielectric substrate according to a certain relationship, and the microstrip open-loop reflectarray faces the feed source; each open-loop unit contains a rectangular ring composed of 4 metal strip lines; the back of the dielectric substrate is an air layer, and the back of the air layer is a ground plane. By changing the size of the metal of the microstrip open-loop itself, the reflection phase delay is realized, and the required compensation phase is obtained from the phase distribution according to the aperture field superposition method. According to the phase shift curve of the open-loop unit, the size of the metal strip line of the corresponding open-loop is obtained, so that open-loop units with different sizes are evenly distributed on the dielectric board. Compared with the traditional microstrip reflectarray antenna, it can obtain radiation performance with high gain and low side lobes, and has a simple structure and is easy to process. Therefore, the present invention has a very broad application prospect.

Claims

1. A millimeter-wave broadband OAM reflecting array antenna with normal feeding excitation, characterized in that It includes a dielectric substrate, a ground plane, an air layer, a feed source, and a microstrip split-ring reflector array; the microstrip split-ring reflector array includes n microstrip split-ring units, and the n microstrip split-ring units are uniformly arranged on the upper surface of the dielectric substrate according to a certain relationship, and the microstrip split-ring reflector array faces the feed source; each split-ring unit includes a rectangular split-ring composed of 4 metal strip lines; the back of the dielectric substrate is the air layer, and the back of the air layer is the ground plane; The reflection phase delay is achieved by changing the size of the metal of the microstrip split ring itself in the microstrip split ring reflector array, and the required compensation phase is obtained from the phase distribution according to the aperture field superposition method. Subsequently, the size of the metal strip line of the split ring is obtained according to the phase shift curve of the split ring unit, so that the split ring units with different sizes are evenly distributed on the dielectric substrate. For the microstrip split-ring reflector array, the 4 rectangular split-rings of each microstrip split-ring unit are all composed of m segments of microstrip lines, and the number of microstrip lines of the rectangular split-ring extends step by step as 3, 4, 5...; taking half of the length L of the central metal strip line as the reference, the lengths of the m segments of microstrip lines spiraling inwards from the top of the central metal strip line are k1*L, k2*L, k3*L, k4*L,...km*L respectively; where k1, k2, k3, k4...km*L are obtained by comparing the reflection phase and amplitude changes of the rectangular split-ring unit with different values through HFSS simulation, k1 = 0.8 - 1.0, k2 = 0.7 - 0.9, k3 = 0.4 - 0.6, k4 = 0.5 - 0.7......; the width of the metal strip line is w = 0.1 - 0.3 mm.

2. The positive-feed excited millimeter-wave broadband OAM reflecting array antenna according to claim 1, wherein The dielectric substrate uses a high-performance low-loss millimeter-wave dielectric substrate, the dielectric constant of the dielectric substrate is 3.0 - 4.0, the contour of the dielectric substrate is circular, and the thickness of the dielectric substrate is H1 = 0.8 - 1.2 mm; the outer contour of the microstrip split-ring unit is square, and the side length P of the square contour is 5.5 - 6 mm; the thickness of the air layer is H2 = 1.0 - 2.0 mm.

3. The positive-feed excited millimeter-wave broadband OAM reflecting array antenna according to claim 1, characterized in that The feed source uses a pyramidal corrugated horn antenna for positive feed excitation, the beam direction is perpendicular to the microstrip split-ring array antenna, and the distance between the pyramidal corrugated horn antenna feed source and the array reflector is 100 - 120 mm.

4. The right-fed excited millimeter-wave broadband OAM reflecting array antenna according to claim 1, characterized in that The microstrip split-ring unit is etched on one side of the dielectric substrate by copper plating technology, and the copper plating thickness is 0.03 - 0.12 mm.

5. The positive-feed excited millimeter-wave broadband OAM reflecting array antenna according to claim 1, characterized in that It is used to realize vortex beams with different mode numbers, the mode number l = 1, 2, 3, 4,..., and has good bandwidth, that is, while maintaining a certain bandwidth, it radiates OAM beams with multiple different mode numbers and maintains a high purity ratio.

6. The orthogonal feeding excited millimeter-wave broadband OAM reflecting array antenna according to claim 1, characterized in that The microstrip split-ring reflector array antenna is configured to obtain the required compensation phase from the phase field distribution of the desired beam according to the aperture field superposition method. That is, the compensation phase of the (m,n)th element. Assuming the feed vector is The vector of the (m,n)th element is The target beam direction should satisfy By adjusting to satisfy the above equation, a reflector array with an arbitrarily oriented main beam is designed; according to the phase shift curve of the microstrip split-ring element, the corresponding size of the open microstrip ring element along the element is obtained.

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