An antenna array

Abstract

The present invention discloses an antenna array, which includes a transmitting antenna array composed of m antenna elements and a receiving antenna array composed of n antenna elements. The transmitting and receiving antenna arrays form a virtual antenna array. The length N of the main array vector of the virtual antenna array is greater than the number M of non-zero elements of the main array vector plus 4. The main side lobe ratio of the array response curve of the main array vector in any angular direction within the angular range of -90° to 90° is above 2.5 dB. All sub-array spacings in the sub-array vectors of the virtual antenna array are equal, and the number of array elements in the sub-array is ≥4. The antenna array of the present invention can not only improve the angular resolution, but also distinguish large and small targets in the angular dimension.

Description

Technical Field

[0001] The present invention relates to the technical field of automotive radar, and in particular to an antenna array applicable to automotive radar. Background Art

[0002] With the rapid development of intelligent driving technology, the Advanced Driving Assistant System (ADAS) has become an indispensable part of intelligent driving vehicles. The ADAS senses the surrounding environment at any time during the driving of the vehicle through various sensors installed on the vehicle, collects environmental data, identifies, detects, and tracks static or dynamic objects, and combines the map data of the navigator to perform system operation and analysis, thereby predicting possible dangers and effectively increasing the comfort and safety of vehicle driving. Among them, millimeter-wave radar has become the main sensor of ADAS due to its long detection range, small environmental impact, low cost, and mature technology. For the millimeter-wave radar of existing vehicles, in order to achieve higher angular resolution with as few antennas as possible, the transmitting and receiving are separated on the antenna, and a MIMO (Multiple Input Multiple Output) architecture with multiple transmitting antennas and multiple receiving antennas is adopted. The antenna layout greatly affects the angular resolution of the radar. In order to improve the angular resolution, sparse layout is often used. Although sparse layout improves the angular resolution, it also introduces the disadvantages of high sidelobes and inability to distinguish between large and small targets in the angular dimension. No effective solution has been proposed for the above technical problems. Summary of the Invention

[0003] In order to overcome the deficiencies of the prior art, the present invention provides an antenna array that can not only improve the angular resolution but also distinguish between large and small targets in the angular dimension.

[0004] To achieve the above object, the present invention first proposes a concept called a position vector for the antenna array. A horizontal baseline is set for the antenna array. The foot of the perpendicular from the position where the array element is located to the baseline is called the projection position of the array element on the baseline. For all the projection positions of the antenna array elements on the baseline, starting from the projection position of the first antenna array element to the projection position of the last antenna array element, the distance between each projection position of the antenna array element and the projection position of the first antenna array element is an integer multiple of d, where d is the grid spacing and d≥0.15λ, and λ is the wavelength. Starting from the projection position of the first antenna array element, grid quantization is performed with a spacing of d. If there is a projection of an antenna array element on the grid, it is denoted as 1, and if there is no projection of an antenna array element, it is denoted as 0. Such a vector composed of 1 and 0 representing the projection positions of the antenna array elements is called the position vector of the antenna array.

[0005] Based on the above concepts, the technical solution proposed in this invention is as follows: An antenna array includes a transmitting antenna array composed of m antenna elements and a receiving antenna array composed of n antenna elements. The spacing between any two antenna elements in the transmitting antenna array and the receiving antenna array is an integer multiple of d, where d is the grid spacing of the antenna position vector, d≥0.15λ, and λ is the operating wavelength of the antenna. The convolution of the transmitting antenna position vector and the receiving antenna position vector is performed. After modifying the vector elements greater than 1 in the convolution to 1, the formed vector is used as the main array vector. The virtual antenna array corresponding to the main array vector is used as the main array. The length of the main array vector is denoted as N, and the number of non-zero elements in the main array vector is denoted as M.

[0006] The dot product of the steering vector of a target in an angular direction and the main array vector is called the array response vector in that angular direction. Based on the array response vector, a Fourier transform is performed to obtain a new complex vector. Taking the modulus of this new complex vector gives the array response curve in that angular direction. The ratio of the largest peak value to the second largest peak value in the array response curve is denoted as Ratio, and 20lg(Ratio) is defined as the main-to-side lobe ratio of the main array vector in that angular direction.

[0007] It is characterized in that: 1) N>M + 4; 2) The main-to-side lobe ratio of the array response curve of the main array vector in any angular direction within the angular range of -75° to 75° is above 2.5 dB; 3) The main array contains at least one sub-array. The characteristics of the sub-array are that the spacing between all adjacent two elements equal to 1 in the sub-array vector is equal. The spacing between adjacent two elements equal to 1 is called the sub-array spacing, and the number of elements in the sub-array ≥4.

[0008] Furthermore, the spacing between two adjacent elements equal to 1 in the transmitting antenna position vector is denoted as d_tx(i,i + 1), where 1≤i<m, and the spacing between two adjacent elements equal to 1 in the receiving antenna position vector is denoted as d_rx(j,j + 1), where 1≤j<n. The length of the transmitting antenna position vector is defined as the aperture of the transmitting antenna, denoted as A_tx, and the length of the receiving antenna position vector is defined as the aperture of the receiving antenna, denoted as A_rx. The maximum spacing of the receiving antenna max(d_rx(j,j + 1)) is greater than the aperture of the transmitting antenna A_tx, and the transmitting antenna is located within the maximum spacing of the receiving antenna, or the maximum spacing of the transmitting antenna max(d_tx(j,j + 1)) is greater than the aperture of the receiving antenna A_rx, and the receiving antenna is located within the maximum spacing of the transmitting antenna.

[0009] In the above structure, the transmitting antenna array is inserted into the receiving antenna array, or the receiving antenna array is inserted into the transmitting antenna array. The advantage of this is that the transmitting antenna and the receiving antenna can share the same area, thereby reducing the occupied area of the PCB and further reducing costs.

[0010] Further, the main array includes two or more sub-arrays, and the spacing between two sub-arrays is not a multiple.

[0011] In the above structure, if the sub-array spacing is greater than 1, the individual sub-array needs to be de-aliased. If there are two sub-arrays and the sub-array spacing is not a multiple, the ambiguity can be resolved by the cooperation of the two sub-arrays.

[0012] Further, among the sub-arrays included in the main array, the number of array elements in at least one sub-array is ≥5.

[0013] In the above structure, the more the number of array elements in the sub-array, the better the performance of the sub-array.

[0014] Further, among the sub-arrays included in the main array, the number of array elements in at least one sub-array is ≥6, the sub-array spacing of at least one sub-array is ≤3, d = 0.5λ, m = 4 or 3 or 2, and n = 4.

[0015] In the above structure, the more the number of array elements in the sub-array, the better the performance of the sub-array, and the smaller the sub-array spacing, the fewer the multiples for which the sub-array needs to be de-aliased.

[0016] Further, in the array response curve in the 0-degree direction of the main array vector, there is an angular interval with an interval span greater than 10 degrees, and the position of this angular interval is not at the edge of the entire interval. The maximum value within this angular interval is at least 7 dB lower than the maximum value of the array response curve.

[0017] In the above structure, small targets in a fixed angular interval can be identified using the main array.

[0018] Further, the minimum spacing of the receiving antennas is greater than Xd, where X is an integer greater than 1, and the minimum spacing of the positions of the transmitting antennas is greater than Yd, where Y is an integer greater than 1.

[0019] In the above structure, some of the antenna array elements that make up the array have a relatively large width. For example, the width of a single array element exceeds d.

[0020] Further, X is an integer greater than 2, and Y is an integer greater than 2.

[0021] Adopting the above solution, compared with the traditional antenna array, the present invention has the following advantages: high angular resolution, ability to distinguish large and small targets in the angular dimension, small PCB area occupation, and low cost.

[0022] The technical solution of the present invention will be further explained below with reference to the accompanying drawings. Description of the Drawings

[0023] Att Figure 1 is a schematic diagram of the antenna array structure of Embodiment 1 of the present invention.

[0024] Appendix Figure 2 This is the array response curve in the 0-degree direction in Embodiment 1 of the present invention.

[0025] Appendix Figure 3 This is the array response curve in the -20-degree direction in Embodiment 1 of the present invention.

[0026] Appendix Figure 4 This is the array response curve in the -40-degree direction in Embodiment 1 of the present invention.

[0027] Appendix Figure 5 This is the array response curve in the -60-degree direction in Embodiment 1 of the present invention.

[0028] Appendix Figure 6 This is the array response curve in the -80-degree direction in Embodiment 1 of the present invention.

[0029] Appendix Figure 7 This is the array response curve in the 20-degree direction in Embodiment 1 of the present invention.

[0030] Appendix Figure 8 This is the array response curve in the 40-degree direction in Embodiment 1 of the present invention.

[0031] Appendix Figure 9 This is the array response curve in the 60-degree direction in Embodiment 1 of the present invention.

[0032] Appendix Figure 10 This is the array response curve in the 80-degree direction in Embodiment 1 of the present invention.

[0033] Appendix Figure 11 This is the schematic structural diagram of the sub-array extracted from the main array in Embodiment 1 of the present invention.

[0034] Appendix Figure 12 This is the array response curve of the sub-array in the 0-degree direction in Embodiment 1 of the present invention.

[0035] Appendix Figure 13 This is the schematic structural diagram of 2 sub-arrays extracted from the main array in Embodiment 2 of the present invention.

[0036] Appendix Figure 14 This is the array response curve graph in the 0-degree direction in Embodiment 2 of the present invention.

[0037] Appendix Figure 15 This is the schematic diagram of the angle interval of the array response curve graph in the 0-degree direction in Embodiment 1 of the present invention. Detailed implementation manner

[0038] Embodiment 1 of the present invention, as Figure 1As shown, in this example, the antenna array includes a transmitting antenna array composed of 3 transmitting antenna elements and a receiving antenna array composed of 4 receiving antenna elements. The arrangement of each element in the transmitting antenna array and the receiving antenna array is as shown. According to the antenna position vector concept proposed by the present invention, the transmitting antenna position vector [1 0 1 0 0 0 0 0 0 1] and the receiving antenna position vector [1 0 0 1 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1] are obtained respectively. The transmitting antenna position vector and the receiving antenna position vector are convolved. After convolution, the vector elements greater than 1 are modified to 1. The formed vector is called the main array vector (1 0 1 1 0 1 1 0 1 1 0 0 1 0 0 1 0 0 0 0 0 0 1 0 1 0 0 0 0 0 0 1), and the corresponding virtual antenna array is called the main array.

[0039] The distance between adjacent elements 1 in the transmitting antenna position vector is denoted as d_tx(i, i + 1), where 1 ≤ i < m. (In this embodiment, d_tx(1, 2) = 2, d_tx(2, 3) = 7). The distance between adjacent elements 1 in the receiving antenna position vector is denoted as d_rx(j, j + 1), where 1 ≤ j < n. (In this embodiment 1, d_rx(1, 2) = 3, d_rx(2, 3) = 3, d_rx(3, 4) = 17). The aperture A_tx of the transmitting antenna is the length of the transmitting antenna position vector (in this embodiment 1, A_tx = 10), and the aperture A_rx of the receiving antenna is the length of the receiving antenna position vector (in this embodiment 1, A_rx = 24). The length of the main array vector is denoted as N (in this embodiment 1, it is 33), and the number of non-zero elements of the main array vector is denoted as M (in this embodiment 1, it is 12).

[0040] In this embodiment 1, N = 33, M = 12, and N > M + 4.

[0041] The dot product of the steering vector of a target in an angular direction and the main array vector is called the array response vector in that angular direction. Based on the array response vector (either directly perform a Fourier transform on the array response vector or supplement zeros after the array response vector), a Fourier transform is performed to obtain a new complex vector. Taking the modulus of this new complex vector gives the array response curve in that angular direction. The ratio of the largest peak value to the second largest peak value in the array response curve is denoted as Ratio, and 20lg(Ratio) is defined as the main sidelobe ratio of the main array vector in that angular direction. The characteristic of the main array vector is that the main sidelobe ratio of the array response curve in any angular direction from -75° to 75° is above 2.5 dB; as Figures 2 - 10 shown.

[0042] As Figure 2As shown, it is the array response curve in the 0-degree direction. The first largest peak is 12, the second largest peak is approximately 6, Ratio = 2, and 20lg Ratio = 20lg2 = 6 dB.

[0043] As Figure 3 shown, it is the array response curve in the -20-degree direction.

[0044] As Figure 4 shown, it is the array response curve in the -40-degree direction.

[0045] As Figure 5 shown, it is the array response curve in the -60-degree direction.

[0046] As Figure 6 shown, it is the array response curve in the -80-degree direction.

[0047] As Figure 7 shown, it is the array response curve in the 20-degree direction.

[0048] As Figure 8 shown, it is the array response curve in the 40-degree direction.

[0049] As Figure 9 shown, it is the array response curve in the 60-degree direction.

[0050] As Figure 10 shown, it is the array response curve in the 80-degree direction.

[0051] Sub-arrays can be extracted from the main array. The sub-array is a uniform array. The position vector of the uniform array is such that the spacing between all adjacent two elements with a value of 1 is equal. The spacing between adjacent two elements with a value of 1 is called the sub-array spacing, and the number of array elements in the sub-array ≥ 4.

[0052] As Figure 11 shown, a sub-array can be extracted from the main array. The sub-array spacing is 3, and the number of array elements in the sub-array is 6. Since the sub-array is uniform, different Chebyshev windows can be added when processing the sub-array to reduce the main-to-side lobe ratio to 30 dB, which is much lower than the main-to-side lobe ratio in the main array, serving the purpose of distinguishing between large and small targets.

[0053] For example, using the window function [0.2956, 0, 0, 0.6837, 0, 0, 1.0000, 0, 0, 1.0000, 0, 0, 0.6837, 0, 0, 0.2956] for the sub-array vector, its array response curve is as Figure 12 shown, which is the array response curve of the sub-array in the 0-degree direction.

[0054] The maximum spacing max(d_rx(j,j + 1)) of the receiving antenna positions is greater than the transmitting antenna aperture A_tx, or the maximum spacing max(d_tx(j,j + 1)) of the transmitting antenna positions is greater than the receiving antenna aperture A_rx. In an embodiment, the maximum spacing of the receiving antenna array positions is 17, and the aperture of the transmitting antenna array is 7. In this way, the transmitting antenna array can be inserted into the receiving antenna array. The advantage of this is that the area occupied by the antenna can be reduced. If this condition is not met, the transmitting antenna array must be arranged side by side with the receiving antenna array, and the occupied area will increase. The transmitting array is [1 0 1 0 0 0 0 0 0 1], the minimum spacing d_tx_min is 2, and the receiving array is [1 0 0 1 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1], and the minimum spacing d_rx_min is 3

[0055] Embodiment 2 extracts 2 sub - arrays from the main array, and the sub - array spacing is not in multiples.

[0056] As Figure 13 shown, tx = [1 0 0 1 0 0 0 1],

[0057] rx = [1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1],

[0058] After convolution, the main array vector is [1 0 0 1 0 0 1 1 0 1 0 0 1 1 0 1 0 0 0 1 0 0 0 0 00 1 0 0 1 0 0 0 1].

[0059] This embodiment meets other requirements in the above - mentioned embodiments, such as N > M, the main - to - sidelobe ratio of the array response curves in each direction, and the insertion of the transmitting array into the receiving array, etc.

[0060] From Figure 12 the array response curve of the sub - array in the 0 - degree direction shown, it can be seen that one target causes 3 targets on the array response curve. Which target is the real one requires ambiguity resolution. If there are two sub - arrays, the array response curves of the two sub - arrays can be combined for ambiguity resolution. As Figure 14 shown are the array response curves of two sub - arrays in the 0 - degree direction. It can be seen from the figure that only the peaks of the two curves overlap at 0 degrees. From this, it is concluded that 0 degrees is the real direction of the target, and thus the solution is obtained.

[0061] It can be seen from Embodiment 1 and Embodiment 2 that there is at least one sub - array with 6 array elements, and the sub - array spacing is 3.

[0062] From Figure 15The array response curve in the 0-degree direction is shown. It can be seen that there are two angular intervals with a span of more than 10 degrees and a level more than 7 dB lower than the peak maximum value.

[0063] The transmitting array is [1 0 0 1 0 0 0 1], and the minimum spacing d_tx_min is 3. The receiving array is [1 0 0 0 0 0 10 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1], and the minimum spacing d_rx_min is 6.

[0064] The present invention is not limited to the above specific embodiments. Those of ordinary skill in the art can implement the present invention in many other specific embodiments according to the content disclosed in the present invention. Or, any simple changes or modifications made by adopting the design structure and concept of the present invention fall within the protection scope of the present invention.

Claims

1. An antenna array, comprising a transmitting antenna array composed of m antenna elements and a receiving antenna array composed of n antenna elements. For the antenna array, a horizontal baseline is set. The foot of the perpendicular line drawn from the position where the antenna element is located to the baseline is called the projection position of the antenna element on the baseline. Starting from the projection position of the first antenna element, grid quantization is performed with a spacing of d. If there is a projection of an antenna element on the grid, it is denoted as 1, and if there is no projection of an antenna element, it is denoted as 0. The vector composed of 1 and 0 representing the projection positions of the antenna elements is called the position vector of the antenna array. The spacing between any two antenna elements of the transmitting antenna array and the receiving antenna array is an integer multiple of d. d is the grid spacing of the antenna position vector, d ≥ 0.15λ, where λ is the operating wavelength of the antenna. The transmitting antenna position vector and the receiving antenna position vector are convolved. After modifying the vector elements greater than 1 in the convolution to 1, the formed vector is used as the main array vector. The virtual antenna array corresponding to the main array vector is used as the main array. The length of the main array vector is denoted as N, and the number of non-zero elements of the main array vector is denoted as M. The dot product of the steering vector of a target in an angular direction and the main array vector is called the array response vector in that angular direction. Based on the array response vector, a Fourier transform is performed to obtain a new complex vector. Taking the modulus of this new complex vector gives the array response curve in that angular direction. The ratio of the largest peak value to the second largest peak value in the array response curve is denoted as Ratio. 20lg(Ratio) is defined as the main sidelobe ratio of the main array vector in that angular direction. It is characterized in that 1) N > M + 4; 2) The main sidelobe ratio of the array response curve of the main array vector in any angular direction within the angular range of -75° to 75° is above 2.5 dB; 3) The main array contains at least one sub-array. The characteristics of the sub-array are: the spacing between all adjacent two elements that are 1 in the sub-array vector is equal. The spacing between adjacent two elements that are 1 is called the sub-array spacing. The number of elements of the sub-array ≥ 4.

2. The antenna array according to claim 1, It is characterized in that The spacing between adjacent two elements that are 1 in the transmitting antenna position vector is denoted as d_tx(i, i + 1), where 1 ≤ i < m. The spacing between adjacent two elements that are 1 in the receiving antenna position vector is denoted as d_rx(j, j + 1), where 1 ≤ j < n. The length of the transmitting antenna position vector is defined as the aperture of the transmitting antenna, denoted as A_tx. The length of the receiving antenna position vector is defined as the aperture of the receiving antenna, denoted as A_rx. The maximum spacing of the receiving antenna max(d_rx(j, j + 1)) is greater than the aperture of the transmitting antenna A_tx, and the transmitting antenna is located within the maximum spacing of the receiving antenna, or the maximum spacing of the transmitting antenna max(d_tx(j, j + 1)) is greater than the aperture of the receiving antenna A_rx, and the receiving antenna is located within the maximum spacing of the transmitting antenna.

3. The antenna array according to claim 1, It is characterized in that The main array contains 2 or more sub-arrays, and the spacing between two sub-arrays is not in a multiple relationship.

4. The antenna array according to claim 3, It is characterized in that In the sub-arrays, the number of array elements in at least one sub-array ≥ 5.

5. The antenna array according to claim 4, wherein, the number of array elements in at least one sub-array ≥ 6, the sub-array spacing of at least one sub-array ≤ 3, d = 0.5λ, m = 4 or 3 or 2, n = 4.

6. The antenna array according to claim 1, wherein, in the array response curve in the 0-degree direction of the main array vector, there is an angular interval with an interval span greater than 10 degrees and the position of this angular interval is not the edge of the entire interval, and the maximum value within this angular interval is at least 7 dB lower than the maximum value of the entire array response curve.

7. The antenna array according to claim 2, wherein, the minimum spacing of the receiving antennas is greater than Xd, X is an integer greater than 1, and the minimum spacing of the positions of the transmitting antennas is greater than Yd, Y is an integer greater than 1.

8. The antenna array according to claim 7, wherein, X is an integer greater than 2, and Y is an integer greater than 2.

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