Antenna array for satellite communication

Abstract

The invention discloses an antenna array for satellite communication, which comprises a plurality of antenna units and feeder lines, the plurality of antenna units are arranged along a straight line, all the antenna units are distributed in a mirror symmetry manner along the center of the antenna array, and the distances between any antenna unit on any side of the center of the antenna array and the centers of two adjacent antenna units are different; each antenna unit is connected with a feeder line deviating from the center of the antenna unit, and the feeder lines connected with any pair of antenna units which are in mirror symmetry along the center of the antenna array deviate from the center of the antenna unit in opposite directions; the device is high in integration level and low in complexity, and can effectively suppress side lobes during broadband and wide-angle beam scanning.

Description

Technical Field

[0001] The present invention relates to antennas, and in particular to an antenna array for satellite communications. Background Art

[0002] With the rapid development of wireless communications, spectrum resources below 6 GHz are about to be exhausted and cannot meet the high-bandwidth, high-speed, and high-throughput communication requirements of the fifth generation and future mobile communications and satellite communications. The millimeter wave band has abundant spectrum resources, which can provide sufficient carrier bandwidth for wireless communication systems and achieve higher transmission rates and lower latency. As an indispensable and important air interface component in millimeter wave systems, high-performance planar antennas with wide bandwidth, high gain, miniaturization, high integration, wide scanning angle, and low cost have become an important research hotspot.

[0003] In the design of broadband and ultra-wideband antenna arrays, it is difficult to keep the element spacing less than one wavelength over the entire operating frequency band. Therefore, broadband arrays will inevitably have high side lobes or grating lobes, especially when the beam is scanned to a large angle range, the side lobe level will increase significantly or even exceed the main lobe, resulting in failure to work properly. Although antenna miniaturization can alleviate the above problems to a certain extent, the design complexity of the antenna will increase significantly and the working bandwidth will be limited. In addition, the reduction in radiation area will lead to the deterioration of antenna gain performance. By utilizing the characteristics of sparse array technology that allows flexible arrangement of array elements, the antenna position can be adjusted with the help of optimization algorithms to achieve the desired beam scanning characteristics within a wide angle range within the working bandwidth. However, sparse array technology is usually only applicable to larger-scale antenna arrays. For small-scale antenna arrays with limited design freedom, it is almost impossible to achieve grating lobe suppression during broadband beam scanning. This is the current design challenge of small-scale phased arrays with broadband and wide angle scanning. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide an antenna array for satellite communications which has high integration, low complexity and can effectively suppress side lobes during wide-band and wide-angle beam scanning.

[0005] Technical solution: The antenna array for satellite communication described in the present invention includes multiple antenna units and feeders, wherein the multiple antenna units are arranged along a straight line, and all antenna units are distributed in a mirror-symmetrical manner along the center of the antenna array. Any antenna unit on either side of the center of the antenna array has a different center distance from its two adjacent antenna units; each antenna unit is connected to a feeder that deviates from its center, and the feeders connected to any pair of antenna units that are mirror-symmetrical along the center of the antenna array deviate from their centers in opposite directions.

[0006] Based on the above technical solution, multiple antenna units uniformly arranged along a straight line are set to a non-uniform arrangement, that is, multiple antenna units uniformly arranged in a straight line with equal spacing are changed to an arrangement with unequal spacing, specifically, they are mirror-symmetrical along the center of the antenna array, and the spacing between any antenna unit on either side of the center of the antenna array is different from that of the adjacent antenna units on both sides; at the same time, the feeder connected to each antenna unit deviates from its center to deflect the radiation beam of the antenna unit, and a scanning beam with low sidelobe characteristics can be generated under the excitation of the non-uniform arrangement of the antenna units and the offset of the feeder; and as long as the antenna units and the feeders of the antenna array are arranged in this way, effective suppression of side lobes can be achieved without complex design when high integration requirements are required and wide-band and wide-angle beam scanning is required.

[0007] Preferably, the center spacing between the antenna units is based on the offset distance Δd of the nth antenna unit compared to the corresponding antenna unit in the uniform linear antenna array. n Sure;

[0008] Δd n The calculation formula is

[0009]

[0010] Among them, δ n is the spatial phase difference of the nth antenna element (1) compared to the corresponding antenna element (1) in the uniform linear antenna array, k = 2πc / f, c is the speed of light, and f is the operating frequency of the antenna; Δd n The sign of is determined by the offset direction of the feeder (2) connected to the antenna unit (1), and the feeder (2) takes a positive value if it is offset to the left relative to the center of the antenna unit (1) and a negative value if it is offset to the right;

[0011] δ n The distance between the feeder (2) and the center of the antenna unit (1) to which it is connected is calculated by the optimization method according to the following formula and the set target:

[0012] Solution

[0013]

[0014] Where AF(θ) is the actual array factor pattern of the antenna array, AF0(θ) is the array factor pattern of the uniform linear antenna array, N is the total number of antenna elements (1), θ is the angle between the vertical line in the antenna array and the array axis, and α n is the excitation phase of the nth antenna element (1).

[0015] Setting the antenna array according to the antenna unit offset distance solved by the above formula can more effectively achieve sidelobe suppression.

[0016] Preferably, the optimization algorithm adopts a genetic algorithm, a particle swarm acceleration algorithm or a gradient descent method.

[0017] Preferably, the feed line is offset from the center of the antenna unit to which it is connected by a distance less than 10% of the antenna's operating wavelength.

[0018] Setting the feed line offset within the above range will not have a significant impact on the impedance matching of the antenna unit port.

[0019] Preferably, the antenna unit is arranged on a first metal layer, a second metal layer and a third metal layer are arranged in sequence below the first metal layer, a feed line is arranged on the third metal layer, and a radiation slot matching the antenna unit is provided on the second metal layer, and the radiation slot is perpendicular to the feed line.

[0020] Preferably, a fourth metal layer and a fifth metal layer are sequentially arranged below the third metal layer, and the fifth metal layer is provided with a square groove whose center is projected on the antenna unit and coincides with the center thereof.

[0021] Preferably, the second metal layer is provided with a plurality of metallized through-hole arrays connected to the fifth metal layer so that the two form a quasi-closed metal shielding structure.

[0022] Preferably, the metallized through hole arrays are arranged on both sides of each feeder line.

[0023] Preferably, an insulating dielectric substrate is provided between adjacent metal layers.

[0024] Preferably, the size of the insulating dielectric substrate between the first metal layer and the second metal layer is smaller than the size of other insulating dielectric substrates.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following significant effects: by arranging the antenna units in a non-uniform manner in a specific manner and making the feeder connected to each antenna unit deviate from its center, it is possible to effectively suppress the side lobes. This can be achieved without complex design when a small-scale antenna array requires a high degree of integration, and effective suppression of the side lobes can be achieved during wide-band and wide-angle beam scanning; secondly, the limitation of the feeder offset can take into account the wide-band impedance matching of the antenna. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a side view of the overall structure of the present invention;

[0027] Figure 2 It is a schematic diagram of the overall structure of the present invention;

[0028] Figure 3 is a schematic diagram of the structure of the antenna array;

[0029] Figure 4It is a schematic diagram of the structure of the antenna array, radiation slot and feed line;

[0030] Figure 5 The S parameter test and simulation results of the antenna array;

[0031] Figure 6 The test and simulation results of the antenna array’s directional pattern in the Phi=90° plane at 22GHz;

[0032] Figure 7 The test and simulation results of the antenna array’s directional pattern in the Phi=90° plane at 30GHz;

[0033] Figure 8 The test and simulation results of the antenna array’s directional pattern in the Phi=90° plane at 38GHz. DETAILED DESCRIPTION

[0034] As shown in the figure, an antenna array for satellite communication described in the present invention includes a plurality of antenna units 1 and a feeder 2, wherein the plurality of antenna units 1 are arranged along a straight line, and all antenna units 1 are distributed in a mirror-symmetrical manner along the center of the antenna array, and any antenna unit 1 on either side of the center of the antenna array has a different center distance from the two adjacent antenna units 1; each antenna unit 1 is connected to a feeder 2 deviated from its center, and the feeders 2 connected to any pair of antenna units 1 that are mirror-symmetrical along the center of the antenna array deviate from their centers in opposite directions.

[0035] The antenna unit 1 is not limited to a specific antenna form, and can be a patch antenna, a slot antenna, a wire antenna, or other antenna forms with a mirror-symmetrical structure, and can form an asymmetric offset excitation through its feeder offset. The number of antenna units 1 can be an odd number or an even number, and the specific number is set according to actual needs; in this embodiment, 4 square antenna units 1 are used.

[0036] The antenna units 1 are arranged along a straight line, that is, the array axis. At the same time, all the antenna units 1 must also satisfy the distribution of mirror symmetry about the center of the antenna array. When the number of antenna units 1 is an odd number, the center of the antenna array is the center of the middle antenna unit 1. When the number of antenna units 1 is an even number, the center of the antenna array is the midpoint of the line connecting the centers of the two middle antenna units 1. Because the center of the antenna array is mirror symmetric, the spacing between the two antenna units 1 on the left side of the center point is equal to the spacing between the two corresponding antenna units 1 on the right side of the center of the antenna array that are mirror symmetric to it.

[0037] Existing linear array antennas are all arranged uniformly, that is, the spacing between antenna units 1 is equal. In addition to meeting the above requirements, the antenna units 1 of the present invention are also arranged non-uniformly, specifically: the center spacing between the antenna units 1 on either side of the center of the antenna array is different from the center spacing between the antenna units 1 adjacent to it on both sides. However, because all antenna units 1 are distributed in a mirror-symmetrical manner about the center, the center spacing between the antenna units 1 symmetrical to the other side of the center is still the same. For better explanation, assume that there are 6 antenna units 1 in total, and each antenna unit 1 is numbered from left to right according to the array axis, and is called the nth unit. For example, the first antenna unit 1 on the left is called the 1st unit, then the center spacing between the 2nd unit and the 1st unit is equal to the center spacing between the 5th unit and the 6th unit, but not equal to the center spacing between the 2nd unit and the 3rd unit.

[0038] The feeder line 2 needs to deviate from the center of the antenna unit 1, and the feeder line 2 of any pair of antenna units 1 that are mirror-symmetrical along the center of the antenna array are offset in opposite directions. For example, if the feeder line 2 connected to the second unit is offset to the left relative to its center, then the feeder line 2 connected to the fifth unit is offset to the right relative to its center. The feeder line 2 only needs to satisfy the opposite offset directions. The offset distances of the feeder lines 2 of different antenna units 1 do not need to be equal or satisfy other specific related relationships, but the distance that each feeder line 2 deviates from the center of the antenna unit 1 to which it is connected must be less than 10% of the antenna working wavelength.

[0039] The center spacing between the antenna elements 1 is based on the offset distance Δd of the nth antenna element 1 compared to the corresponding antenna element 1 in the uniform linear antenna array. n Determine, Δd n The specific meaning of is explained by an example. For example, Δd2 is the offset distance of the second unit arranged in the non-uniform arrangement according to the present invention compared with the second unit arranged in the uniform arrangement. The offset distance is calculated based on the center distance between the two, and the offset is translated along the array axis. All Δd n , combined with the center spacing of the originally evenly arranged antenna units 1, the center spacing between the antenna units 1 can be calculated.

[0040] Δd n The calculation formula is

[0041]

[0042] Among them, δ n is the spatial phase difference of the nth antenna element (1) compared to the corresponding antenna element (1) in the uniform linear antenna array, k = 2πc / f, c is the speed of light, and f is the operating frequency of the antenna; Δd nThe sign of is determined by the offset direction of the feeder (2) connected to the antenna unit (1). The feeder (2) takes a positive value if it is offset to the left relative to the center of the antenna unit (1), and a negative value if it is offset to the right. The offset distance of the feeder 2 relative to the center of the antenna unit 1 also takes a positive or negative sign, and the rules are the same as above.

[0043] δ n The distance between the feeder (2) and the center of the antenna unit (1) to which it is connected is calculated by the optimization method according to the following formula and the set target:

[0044] Solution

[0045]

[0046] Where AF(θ) is the actual array factor pattern of the antenna array, AF0(θ) is the array factor pattern of the uniform linear antenna array, N is the total number of antenna elements (1), θ is the angle between the vertical line in the antenna array and the array axis, and α n is the excitation phase of the nth antenna element (1).

[0047] In this embodiment, a genetic algorithm is used to jointly optimize the non-uniform arrangement parameters of the antenna array and the feeder offset. Specifically, the spatial phase difference δ corresponding to the spacing offset of each antenna unit is n The offset distance of the feeder relative to the center of the antenna unit to which it is connected (hereinafter referred to as the feeder offset for simplicity) is encoded as an optimization variable. Since the antenna unit spacing must satisfy the mirror symmetry constraint, the optimization variables only need to cover the unit parameters on one side of the center point, and the other side is automatically generated through the symmetry relationship, which significantly reduces the variable dimension. The implementation steps are divided into the following steps:

[0048] 1. Variable encoding and initialization: The spatial phase difference δ corresponding to the spacing offset of each antenna unit n The feeder offset is set as the optimization variable to generate the initial population. The optimization variable corresponding to each individual is represented by a string of binary codes.

[0049] 2. Fitness design: The maximum sidelobe level (SLL) within the scanning angle range of ±30° in a wide band (21-42GHz) is used as the main optimization target. The fitness is calculated for each individual, and individuals with high fitness are more likely to be selected to generate the next generation. SLL is the AF (θ) value within the range of the main lobe (θ0-BW / 2, θ0+BW / 2) at a specific frequency point f. In this embodiment, θ0 represents the direction of the scanning beam, which is agreed to be between -30° and 30°; BW represents the main beam width, which is agreed to be 30°; the value range of the frequency point f is within (21GHz, 42GHz), that is, the core goal of this algorithm is to ensure that the sidelobe level (SLL) at all frequencies (21-42GHz) and scanning angles (±30°) is strictly not higher than -13.5dB (the target can be appropriately modified according to actual needs), and the fitness function needs to directly quantify the degree of deviation of the design parameters from this target.

[0050]

[0051] Where: N f N is the number of discrete frequency points (such as 21GHz, 30GHz, 38GHz); θ is the number of discrete angle samples (covering the interval outside the main lobe at 10° intervals)

[0052] 3. Selection and evolution strategy: The tournament selection method is used to retain the top 20% elite individuals in fitness to ensure that excellent solutions are not lost; the crossover operation uses arithmetic crossover to retain the spacing correlation between adjacent units; the mutation operation introduces Gaussian perturbation, and the mutation probability is adaptively reduced with the number of iterations (from 5% to 1%) to balance global search and local convergence.

[0053] 4. Termination condition: The optimization is terminated when the fitness improvement is less than 1% for 10 consecutive generations or when it reaches 100 generations. In this embodiment, the specific optimization results of the antenna array are as follows Figure 3-4 shown.

[0054] As long as the antenna unit 1 and the feeder 2 meet the above conditions, the side lobe can be effectively suppressed. In this embodiment, the specific structure of the antenna is as follows:

[0055] The antenna as a whole adopts a stacked structure, including a first metal layer 3, a second metal layer 4, a third metal layer 5, a fourth metal layer 7 and a fifth metal layer 8 arranged in sequence from top to bottom, and an insulating dielectric substrate 11 is provided between two adjacent metal layers; the antenna unit 1 is arranged on the first metal layer 3, and the feed line 2 is arranged on the third metal layer 5. The feed line 2 on the third metal layer 5 is actually a printed excitation strip line. The feed lines 2 are arranged at unequal intervals and are open circuits. The second metal layer 4 is provided with a radiation slot 6 perpendicular to the feed line 2 and corresponds to the antenna unit 1 one by one, and the antenna unit 1 is excited through the radiation slot 6; the fifth metal layer 8 is provided with a square groove 9 whose center coincides with the projection of the center on the antenna unit.

[0056] The second metal layer 4 is provided with a plurality of metallized through-hole arrays 10 penetrating the insulating three-layer dielectric substrate 11 and connected to the fifth metal layer 8, so that the second metal layer 4 and the fifth metal layer 8 form a quasi-closed metal shielding structure for shielding the external electromagnetic interference to the antenna, and metallized through-holes are provided on both sides of each feeder 2. The antenna can also be provided with a switching structure and a port micro RF coaxial connector for testing. The size of the insulating dielectric substrate 11 between the first metal layer 3 and the second metal layer 4 is smaller than the size of other insulating dielectric substrates 11, and the remaining insulating dielectric substrates 11 are the same size. Of course, the size of the insulating dielectric substrate 11 can be set based on actual needs and there are no special requirements.

[0057] like Figure 5 As shown, the measured impedance bandwidth of each unit antenna of the antenna of the present invention can cover 21 GHz to 42 GHz, and meet the port reflection coefficient of less than -10 dB.

[0058] Figure 6-8 The directional diagrams of the antenna according to the present invention in the H-section plane (phi=90°) at three typical frequency points of 22 GHz, 30 GHz and 38 GHz are respectively given. Within the scanning angle range of ±30°, the sidelobe level is lower than -10 dB on average.

[0059] Figure 6-8 The results show that the antenna designed in the present invention has good low sidelobe characteristics, and meets the design requirements in terms of in-band standing wave, sidelobe level and scanning range, and is suitable for millimeter-wave wireless communication and satellite communication technology represented by 5G.

Claims

1. An antenna array for satellite communication, comprising a plurality of antenna units (1) and a feeder (2), characterized in that: The multiple antenna units (1) are arranged along a straight line, all antenna units (1) are distributed in a mirror-symmetrical manner along the center of the antenna array, and the center distances between any antenna unit (1) on either side of the center of the antenna array and its two adjacent antenna units (1) are different; each antenna unit (1) is connected to a feeder line (2) deviating from its center, and the feeder lines (2) connected to any pair of antenna units (1) that are mirror-symmetrical along the center of the antenna array deviate from their centers in opposite directions.

2. The antenna array for satellite communication according to claim 1, characterized in that: The center spacing between the antenna units (1) is based on the offset distance Δd of the nth antenna unit (1) compared to the corresponding antenna unit (1) in the uniform linear antenna array. n Sure; Δd n The calculation formula is Among them, δ n is the spatial phase difference of the nth antenna element (1) compared to the corresponding antenna element (1) in the uniform linear antenna array, k = 2πc / f, c is the speed of light, and f is the operating frequency of the antenna; Δd n The sign of is determined by the offset direction of the feeder (2) connected to the antenna unit (1), and the feeder (2) takes a positive value if it is offset to the left relative to the center of the antenna unit (1) and a negative value if it is offset to the right; δ n The distance of the feeder (2) from the center of the antenna unit (1) to which it is connected is solved by the optimization algorithm according to the following formula and the set target: Where AF(θ) is the actual array factor pattern of the antenna array, AF0(θ) is the array factor pattern of the uniform linear antenna array, N is the total number of antenna elements (1), θ is the angle between the vertical line in the antenna array and the array axis, and α n is the excitation phase of the nth antenna element (1).

3. The antenna array for satellite communication according to claim 2, characterized in that: The optimization algorithm adopts genetic algorithm, particle swarm acceleration algorithm or gradient descent method.

4. The antenna array for satellite communication according to claim 1, characterized in that: The feed line (2) is offset from the center of the antenna unit (1) to which it is connected by a distance less than 10% of the antenna's operating wavelength.

5. The antenna array for satellite communication according to claim 1, characterized in that: The antenna unit (1) is arranged on a first metal layer (3), a second metal layer (4) and a third metal layer (5) are arranged in sequence below the first metal layer (3), a feed line (2) is arranged on the third metal layer (5), and a radiation slot (6) matching the antenna unit (1) is provided on the second metal layer (4), and the radiation slot (6) is perpendicular to the feed line (2).

6. The antenna array for satellite communication according to claim 5, characterized in that: A fourth metal layer (7) and a fifth metal layer (8) are arranged in sequence below the third metal layer (5), and the fifth metal layer (8) is provided with a square groove (9) whose center is projected on the antenna unit (1) and coincides with its center.

7. The antenna array for satellite communication according to claim 6, characterized in that: The second metal layer (4) is provided with a plurality of metallized through hole arrays (10) connected to the fifth metal layer (8) so that the two form a quasi-closed metal shielding structure.

8. The antenna array for satellite communication according to claim 7, characterized in that: The metallized through hole arrays (10) are arranged on both sides of each feed line (2).

9. The antenna array for satellite communication according to claim 6, characterized in that: An insulating dielectric substrate (11) is arranged between adjacent metal layers.

10. The antenna array for satellite communication according to claim 9, characterized in that: The size of the insulating dielectric substrate (11) between the first metal layer (3) and the second metal layer (4) is smaller than the size of other insulating dielectric substrates (11).

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