Vehicle-mounted 4D millimeter wave radar sparse antenna array and design method thereof

Abstract

The invention discloses a vehicle-mounted 4D millimeter wave radar sparse antenna array and a design method thereof. A radar system used in the invention comprises 12 transmitting antennas and 16 receiving antennas, and the antennas cannot be overlapped. The 12 transmitting antennas are divided into two groups, namely TX1 and TX2, the number of the TX1 is 9, and the number of the TX2 is 3; the 16 receiving antennas are equally divided into two groups of RX1D and RX2D. The TX1 and the RX1D are synthesized into a one-dimensional virtual array for two-dimensional target detection, and the TX and the RX2D are synthesized into a two-dimensional virtual array for three-dimensional target detection, so that the detection capability in the azimuth direction and the pitching direction is realized. According to the method, the main lobe width and the side lobe level of the directional diagrams of the two-dimensional virtual array and the one-dimensional virtual array are successively optimized by using the random search algorithm, and the angular resolution in the pitching direction and the angular resolution in the azimuth direction are improved under the condition of not increasing the size of the radar in the pitching direction.

Description

Technical Field

[0001] The present invention relates to the field of automotive millimeter wave radar, and in particular to a vehicle-mounted 4D millimeter wave radar sparse antenna array and a design method thereof. Background Art

[0002] 4D millimeter-wave radar is a next-generation radar system that demonstrates a new way for highly automated driving (HAD) to improve automotive safety. The unique advantage of millimeter-wave radar, which can work all day and all weather, makes it superior to sensors such as on-board optical cameras and lidar. In addition, it is cheaper than lidar. The emergence of 4D millimeter-wave radar solves the shortcomings of traditional millimeter-wave radar, which has low horizontal angular resolution and lacks height measurement capabilities.

[0003] Since high-resolution sensing capabilities are required in the range-Doppler-azimuth-elevation domain, the HAD system requires a high-resolution 4D imaging radar to provide high angular resolution and better direction of arrival (DOA) estimation. In order to obtain high angular resolution in azimuth and elevation, a larger antenna array aperture size and a large number of transmit and / or receive channels are required. However, to be applicable to automobiles, the size of the radar cannot be too large. The virtual aperture technology in the multiple input multiple output (MIMO) mode has largely solved the contradiction between the radar angular resolution and size, and the arrangement of the transmitting and receiving antennas is the first problem to be solved in the development of 4D millimeter-wave radars, and the arrangement of the array directly determines the product size and angular resolution and other important indicators. In the limited antenna panel space, the existing technology has relatively low angular resolution in the horizontal and elevation directions, and the size is relatively large, which needs to be further improved.

[0004] Highly integrated radar chips integrate transceiver RF links, waveform formation, transceiver digital links, etc. A single MIMO radar chip has a certain number of transceiver channels, so the number of antennas based on a single chip design cannot be changed, which limits the design of the radar system. The antenna design in the MIMO radar system directly affects the angular resolution of the system. A small number of transceiver antennas will result in low resolution of the radar system. Increasing the antenna element spacing and sparsely designing the array can increase the array aperture and improve the resolution, but too large an element spacing will lead to the generation of grating lobes. Summary of the invention

[0005] In view of the technical problems in the prior art of low angular resolution in the horizontal and elevation directions and large size of the antenna panel, the object of the present invention is to provide a vehicle-mounted 4D millimeter-wave radar sparse antenna array and a design method thereof.

[0006] The purpose of the present invention is achieved through the following technical methods:

[0007] A sparse antenna array design method for a vehicle-mounted 4D millimeter-wave radar comprises 12 transmitting antennas TX and 16 receiving antennas RX, wherein the antennas cannot overlap, and the 12 transmitting antennas TX are divided into two groups, namely TX1 and TX2, wherein TX1 has 9 antennas and TX2 has 3 antennas; the 16 receiving antennas RX are divided into two groups, namely RX1D and RX2D; TX1 and RX1D are combined into a one-dimensional virtual array for two-dimensional target detection; TX and RX2D are combined into a two-dimensional virtual array for three-dimensional target detection, and have the detection capability in azimuth and elevation directions.

[0008] Furthermore, the design method specifically comprises the following steps:

[0009] Step 1. Set the fixed position of the radar as the coordinate origin, set the radar along the direction of the car's forward movement as the +x axis, set the radar along the horizontal right direction of the car as the +y axis, and set the radar along the vertical downward direction of the ground as the +z axis; set the horizontal angle between the +x axis and the target direction line as the azimuth angle, and set the vertical angle between the +x axis and the target direction line as the azimuth angle; construct a rectangular coordinate system and define the pitch direction and azimuth direction; arrange the RX2D in the z direction; the spacing dz between adjacent antennas in the z direction, the dz is 2.05λ, where the λ is the wavelength; set the maximum difference of the y coordinate, and randomly generate the y coordinate of the RX2D;

[0010] Step 2. Arrange the TX1 and the TX2 in the y direction, with the y coordinates of the TX1 being the same, and the y coordinates of the TX2 being the same; the distance between the TX1 and the TX2 in the z direction is 8dz; fix the positions of the two antennas at both ends of the TX1, and randomly generate the y coordinates of the remaining 10 transmitting antennas TX, requiring that the y coordinate size of the transmitting antenna TX is within the y coordinate range of the two fixed TX1 antennas, and the distance between two adjacent TX antennas in the y direction is not less than 1λ and is an integer multiple of 0.5λ;

[0011] Step 3. Synthesize TX and RX2D into a two-dimensional virtual array, and use the FFT algorithm to calculate the main lobe width and side lobe level of the array's directional pattern for an object at 0° in azimuth and elevation.

[0012] Step 4. Repeat step 1 to step 3 until the maximum number of cycles is reached, select the case that meets the sidelobe level requirements and has the narrowest main lobe width, and determine the corresponding TX and RX2D coordinates;

[0013] Step 5. A group of RX1Ds are arranged in the y direction, the antenna positions at both ends of the RX1Ds are fixed, and the y coordinates of the remaining 6 RX1Ds are randomly generated. The y coordinate size of the randomly generated RX1Ds is within the y coordinate range of the two fixed RX1D antennas, and the distance between two adjacent RX1Ds is not less than 1λ and is an integer multiple of 0.5λ;

[0014] Step 6. Synthesize TX1 in TX obtained in step 4 and randomly generated RX1D into a one-dimensional virtual array, and calculate the main lobe width and side lobe level of the directional pattern of the one-dimensional virtual array for an object at a 0° position (the 0° position means that the object is directly in front of the array);

[0015] Step 7. Repeat step 5 and step 6 to the maximum number of cycles, select the case where the sidelobe level meets the requirements and the main lobe width is the narrowest, and determine the corresponding RX1D coordinates.

[0016] Furthermore, since the radiation patterns of the antennas are only related to the relative positions between the antennas and have nothing to do with the absolute positions between the antennas, TX, RX1D, and RX2D can each be translated as a whole in the plane space until the antennas do not overlap with each other.

[0017] Furthermore, in step 3, the step of synthesizing TX and RX2D into a two-dimensional virtual array is specifically as follows: adding the horizontal and vertical coordinates of each TX antenna to the horizontal and vertical coordinates of each RX2D antenna to obtain the positions of 96 virtual array elements.

[0018] The present invention also provides a vehicle-mounted 4D millimeter-wave radar sparse antenna array, including 12 transmitting antennas TX and 16 receiving antennas RX, the antennas cannot overlap, the transmitting antenna TX includes TX1 and TX2, wherein the TX1 has 9 antennas and the TX2 has 3 antennas; the receiving antenna RX includes RX1D and RX2D, wherein the RX1D and RX2D have 8 antennas each; TX1 and RX1D synthesize a one-dimensional virtual array for two-dimensional target detection; TX and RX2D synthesize a two-dimensional virtual array for three-dimensional target detection.

[0019] The beneficial effects of the present invention are:

[0020] 1. The present invention improves the angular resolution in the elevation direction without increasing the elevation dimension of the radar.

[0021] 2. The present invention utilizes a sparse array to improve the angular resolution in azimuth.

[0022] 3. The present invention utilizes a random search algorithm to successively optimize the main lobe width and side lobe level of the directional patterns of a two-dimensional virtual array and a one-dimensional virtual array. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow chart of the arrangement method of the present invention;

[0024] Figure 2 It is a schematic diagram of the coordinate system of the present invention;

[0025] Figure 3 A schematic diagram of the position distribution of radar antenna array elements of the present invention;

[0026] Figure 4 is a schematic diagram of a two-dimensional virtual array;

[0027] Figure 5 is the directional diagram of the two-dimensional virtual array for the object at (0°, 0°);

[0028] Figure 6 is the azimuthal cross-sectional view of the two-dimensional virtual array for the object at (0°, 0°);

[0029] Figure 7 is a pitch-to-elevation cross-sectional view of a two-dimensional virtual array for an object at (0°, 0°);

[0030] Figure 8 It is a schematic diagram of a one-dimensional virtual array;

[0031] Fig. 9 is the directional pattern of the one-dimensional virtual array for an object at 0°. DETAILED DESCRIPTION

[0032] In order to better understand the purpose, technical method and function of the present invention, the following is a further detailed description of a vehicle-mounted 4D millimeter-wave radar sparse antenna array and a design method thereof in conjunction with the accompanying drawings.

[0033] like Figure 2 As shown in the figure, the forward-facing vehicle-mounted radar is generally placed on the bumper of the car, constructing a rectangular coordinate system and defining the pitch and azimuth directions. Figure 3 As shown, a vehicle-mounted 4D millimeter-wave radar sparse antenna array is provided in an embodiment of the present invention. The radar system used in the present invention includes 12 transmitting antennas TX and 16 receiving antennas RX, and the antennas cannot overlap. The transmitting antenna TX includes TX1 and TX2, wherein the TX1 has 9 antennas and the TX2 has 3 antennas; the receiving antenna RX includes RX1D and RX2D, wherein the RX1D and RX2D have 8 antennas each; TX1 and RX1D synthesize a one-dimensional virtual array for two-dimensional target detection; the TX and RX2D synthesize a two-dimensional virtual array for three-dimensional target detection, and have detection capabilities in azimuth and elevation directions.

[0034] The TX and RX1D antennas used in the embodiment of the present invention have a length of 25 mm and a width of 3.3 mm, and the RX2D antenna has a length of 17.5 mm and a width of 7.8 mm. The wavelength of the millimeter wave used is about 3.9 mm, which is denoted as 1λ.

[0035] like Figure 1 As shown, a design method for a vehicle-mounted 4D millimeter-wave radar sparse antenna array provided by an embodiment of the present invention includes the following steps:

[0036] Step 1, set the fixed position of the radar as the coordinate origin, set the direction of the radar along the car's forward movement as the +x axis, set the direction of the radar along the car's horizontal right direction as the +y axis, and set the direction of the radar along the vertical ground downward direction as the +z axis; set the horizontal angle between the +x axis and the target direction line as the azimuth angle, and set the vertical angle between the +x axis and the target direction line as the azimuth angle; construct a rectangular coordinate system and define the pitch direction and azimuth direction; arrange the RX2D in the z direction; the spacing dz between adjacent antennas in the z direction, the dz is 2.05λ, where the λ is the wavelength; set the maximum difference of the y coordinate, and randomly generate the y coordinate of the RX2D.

[0037] Step 2, arrange the TX1 and the TX2 in the y direction, the y coordinates between the TX1 are the same, and the y coordinates between the TX2 are the same; the distance between the TX1 and the TX2 in the z direction is 8dz; fix the positions of the two antennas at both ends of the TX1, and randomly generate the y coordinates of the remaining 10 transmitting antennas TX, requiring that the y coordinate size of the transmitting antenna TX is within the y coordinate range of the two fixed TX1 antennas, and the distance between two adjacent TXs in the y direction is not less than 1λ and is an integer multiple of 0.5λ.

[0038] Step 3. Combine TX and RX2D into a two-dimensional virtual array. Calculate the main lobe width and side lobe level of the array's pattern for an object at 0° in azimuth and elevation. Assume that the coordinate vectors of the transmitting antenna and the transmitting antenna are:

[0039]

[0040] Among them, y t 、z t are the y coordinate vector and z coordinate vector of the transmitting antenna, y r 、z r are the y coordinate vector and z coordinate vector of the receiving antenna respectively. y and z represent the y coordinate and z coordinate respectively, the subscripts t and r represent the transmitting antenna and the receiving antenna respectively, and N t and N r Represent the number of transmitting antennas and receiving antennas respectively.

[0041] Get the coordinate vector y of the virtual array elementv 、z v They are:

[0042]

[0043] Among them, the calculation formula of the directional pattern function AF of the target at (0°, 0°) is:

[0044]

[0045] in, is the azimuth angle, θ is the elevation angle, θ0 is the azimuth and elevation of the target location, and j is an imaginary unit. The main lobe width is the angle corresponding to a 3dB drop in the peak value of the pattern, and the side lobe level is the level of the highest side lobe. The main lobe width and the side lobe level are two conflicting goals, that is, the improvement of one goal may lead to the deterioration of the other goal. Therefore, it is necessary to find a balance so that both can be optimized. The side lobe level affects the anti-interference ability of the radar. The side lobe level of the uniform array is -13.25dB. In this invention, the side lobe level requirement is set to -13.25dB (or lower).

[0046] Step 4, repeat steps 1, 2, and 3 to the maximum number of cycles, which can be freely set; select the case that meets the sidelobe level requirements and has the narrowest main lobe width, and determine its corresponding TX and RX2D coordinates. The coordinates obtained in the present invention are:

[0047] TX_y=[0 6 10 11 13 14 16 17 18 0 8 9];

[0048] TX_z=[0 0 0 0 0 0 0 0 0 16.4 16.4 16.4];

[0049] RX2D_y = [5 3 2 1 5 1 1 2];

[0050] RX2D_z=[0 2.05 4.1 6.15 8.2 10.25 12.3 14.35].

[0051] Get a two-dimensional virtual array such as Figure 4 As shown, the corresponding directional pattern function is Figure 5 The cross-sectional views in azimuth and elevation are Figure 6 and Figure 7 .

[0052] Step 5: A group of RX1Ds are arranged in the y direction, the antenna positions at both ends of the RX1Ds are fixed, and the y coordinates of the remaining 6 RX1Ds are randomly generated. The y coordinate size of the randomly generated RX1D is within the y coordinate range of the two fixed RX1D antennas, and the distance between two adjacent RX1Ds is not less than 1λ and is an integer multiple of 0.5λ.

[0053] Step 6: Combine TX1 in TX obtained in step 4 and randomly generated RX1D into a one-dimensional virtual array, remove the overlapping virtual array elements, and calculate the main lobe width and side lobe level of the array's directional pattern for the object at 0°. The directional pattern function of the target at 0° can be simplified to:

[0054]

[0055] Among them, N 1D The number of virtual array elements remaining after removing the overlapping virtual array elements is unique(·) which indicates the de-duplication operation.

[0056] Step 7: Repeat steps 5 and 6 to the maximum number of cycles, select the case where the sidelobe level meets the requirements and the main lobe width is the narrowest, and determine the corresponding RX1D coordinates.

[0057] The coordinates obtained by the present invention are RX1D_y = [0 3.5 9 12.5 16 20.5 31 35.5], and RX1D_z is a suitable constant. Figure 8 As shown, the corresponding directional pattern function is as follows Fig. 9 shown.

[0058] Because the directional pattern function of the antenna array is only related to the relative position but not to the absolute position, the obtained coordinate results can be appropriately translated to obtain Figure 2 The antennas shown are not coincident with each other.

[0059] In summary, the specific parameters of the radar antenna array arrangement obtained by the method used in the present invention are as follows: the antenna array length accounts for 0.85λ (antenna size) + 35.5λ, and the height accounts for 6.41λ (antenna size) + 16.4λ. The two-dimensional pitch angle resolution is 1.76°, the azimuth angle is 2.57°, and the maximum side lobe is -13.88dB. The one-dimensional resolution is 1.1°, and the maximum side lobe is -14.48dB.

[0060] The above embodiments are only used to illustrate the design ideas and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, any equivalent changes or modifications made based on the principles and design ideas disclosed by the present invention are within the protection scope of the present invention.

Claims

1. A method for designing a sparse antenna array for a vehicle-mounted 4D millimeter-wave radar, comprising 12 transmitting antennas TX and 16 receiving antennas RX, wherein the antennas cannot overlap, and wherein: The 12 transmitting antennas TX are divided into two groups, namely TX1 and TX2, wherein TX1 has 9 antennas and TX2 has 3 antennas; the 16 receiving antennas RX are divided into two groups, namely RX1D and RX2D; TX1 and RX1D are combined into a one-dimensional virtual array for two-dimensional target detection; TX and RX2D are combined into a two-dimensional virtual array for three-dimensional target detection.

2. The method for designing a sparse antenna array for a vehicle-mounted 4D millimeter-wave radar according to claim 1, characterized in that: The method specifically comprises the following steps: (1) The fixed position of the radar is set as the coordinate origin, the radar is set along the direction of the car's forward movement as the +x axis, the radar is set along the horizontal right direction of the car as the +y axis, and the radar is set along the vertical downward direction of the ground as the +z axis; the horizontal angle between the +x axis and the target direction line is set as the azimuth angle, and the vertical angle between the +x axis and the target direction line is set as the azimuth angle; a rectangular coordinate system is constructed and the pitch direction and azimuth direction are defined; the RX2D is arranged in the z direction; the spacing dz between adjacent antennas in the z direction is 2.05λ, where λ is the wavelength; the maximum difference of the y coordinate is set, and the y coordinate of the RX2D is randomly generated; (2) Arrange the TX1 and TX2 in the y direction, with the y coordinates of the TX1 being the same, and the y coordinates of the TX2 being the same; the distance between the TX1 and TX2 in the z direction is 8dz; fix the positions of the two antennas at both ends of the TX1, and randomly generate the y coordinates of the remaining 10 transmitting antennas TX, requiring that the y coordinate size of the transmitting antenna TX is within the y coordinate range of the two fixed TX1 antennas, and the distance between two adjacent TX antennas in the y direction is not less than 1λ and is an integer multiple of 0.5λ; (3) synthesizing TX and RX2D into a two-dimensional virtual array; using an FFT algorithm to calculate the main lobe width and side lobe level of the directional pattern of the virtual array for an object at an azimuth angle and an elevation angle of 0°; (4) Repeating steps (1) to (3) until the maximum number of cycles is reached, selecting a case that meets the sidelobe level requirements and has the narrowest main lobe width, and determining the corresponding TX and RX2D coordinates; (5) A group of RX1Ds are arranged in the y direction, the antenna positions at both ends of the RX1Ds are fixed, and the y coordinates of the remaining 6 RX1Ds are randomly generated. The y coordinate size of the randomly generated RX1Ds is within the y coordinate range of the two fixed RX1D antennas, and the distance between two adjacent RX1Ds is not less than 1λ and is an integer multiple of 0.5λ; (6) synthesizing TX1 in TX obtained in step (4) and the randomly generated RX1D into a one-dimensional virtual array, and calculating the main lobe width and side lobe level of the directional pattern of the one-dimensional virtual array for an object at a 0° position; (7) Repeat steps (5) and (6) to the maximum number of cycles, select the case where the sidelobe level meets the requirements and the main lobe width is the narrowest, and determine the corresponding RX1D coordinates.

3. The method for designing a sparse antenna array for a vehicle-mounted 4D millimeter-wave radar according to claim 2, characterized in that: In the step (3), the step of synthesizing TX and RX2D into a two-dimensional virtual array is specifically as follows: adding the horizontal and vertical coordinates of each transmitting antenna TX to the horizontal and vertical coordinates of each RX2D respectively to obtain the positions of 96 virtual array elements.

4. A vehicle-mounted 4D millimeter wave radar sparse antenna array, characterized in that: The invention comprises 12 transmitting antennas TX and 16 receiving antennas RX, wherein the antennas cannot overlap, the transmitting antennas TX comprise TX1 and TX2, wherein the number of the transmitting antennas TX1 is 9 and the number of the receiving antennas TX2 is 3; the receiving antennas RX comprise RX1D and RX2D, wherein the number of the receiving antennas RX1D and RX2D is 8 respectively; TX1 and RX1D are combined into a one-dimensional virtual array for two-dimensional target detection; TX and RX2D are combined into a two-dimensional virtual array for three-dimensional target detection.

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