A sparse antenna array for vehicle-mounted 4D millimeter-wave radar and its design method

Abstract

This invention discloses a sparse antenna array for a vehicle-mounted 4D millimeter-wave radar and its design method. The radar system used in this invention includes 12 transmitting antennas and 16 receiving antennas, which cannot overlap. The 12 transmitting antennas are divided into two groups, TX1 and TX2, where TX1 consists of 9 antennas and TX2 consists of 3 antennas. The 16 receiving antennas are also divided into two groups, RX1D and RX2D. TX1 and RX1D are combined to form a one-dimensional virtual array for two-dimensional target detection, and TX1 and RX2D are combined to form a two-dimensional virtual array for three-dimensional target detection, providing azimuth and elevation detection capabilities. This invention utilizes a random search algorithm to successively optimize the main lobe width and side lobe level of the radiation patterns of the two-dimensional and one-dimensional virtual arrays, improving the angular resolution in both the elevation and azimuth directions without increasing the radar's elevation dimension.

Description

Technical Field

[0001] This invention relates to the field of automotive millimeter-wave radar, and more particularly to a sparse antenna array for vehicle-mounted 4D millimeter-wave radar and its design method. Background Technology

[0002] 4D millimeter-wave radar is a next-generation radar system that demonstrates a new approach to improving vehicle safety through highly automated driving (HAD). The all-weather and day-and-night operation inherent in millimeter-wave radar makes it superior to sensors such as onboard optical cameras and lidar, and it is also more affordable than lidar. The emergence of 4D millimeter-wave radar addresses the shortcomings of traditional millimeter-wave radar, such as low horizontal angular resolution and lack of altitude measurement capabilities.

[0003] High-resolution sensing capabilities are required in the range-Doppler-azimuth-elevation domain, HAD systems necessitate high-resolution 4D imaging radar to provide high angular resolution and better direction-of-arrival (DOA) estimation. Achieving high angular resolution in azimuth and elevation requires a large antenna array aperture size and numerous transmit and / or receive channels. However, for automotive applications, the radar size cannot be too large. Virtual aperture technology in Multiple Input Multiple Output (MIMO) mode largely resolves the conflict between radar angular resolution and size. The arrangement of transmit and receive antennas is a primary challenge in developing 4D millimeter-wave radar, directly determining crucial parameters such as product size and angular resolution. Current technologies, within limited antenna panel space, still exhibit relatively low horizontal and elevation angular resolution and are relatively large in size, requiring further improvement.

[0004] Highly integrated radar chips integrate transceiver radio frequency links, waveform generation, and transceiver digital links. A single MIMO radar chip has a limited number of transceiver channels, so the number of antennas in a single-chip design cannot be changed, which restricts the design of the radar system. The antenna design in a MIMO radar system directly affects the system's angular resolution. A small number of transceiver antennas will result in low radar system resolution. Increasing the spacing between antenna elements and using a sparse array design can increase the array aperture and improve resolution, but excessive element spacing can lead to grating lobes. Summary of the Invention

[0005] In view of the technical problems of low horizontal and pitch angular resolution and large antenna panel size in the existing technology, the purpose of this invention is to provide a vehicle-mounted 4D millimeter-wave radar sparse antenna array and its design method.

[0006] The objective of this invention is achieved through the following technical methods:

[0007] A method for designing a sparse antenna array for a vehicle-mounted 4D millimeter-wave radar includes 12 transmitting antennas (TX) and 16 receiving antennas (RX). The antennas cannot overlap. The 12 transmitting antennas (TX) are divided into two groups, TX1 and TX2, where TX1 consists of 9 antennas and TX2 consists of 3 antennas. The 16 receiving antennas (RX) are also divided into two groups, RX1D and RX2D. TX1 and RX1D are combined to form a one-dimensional virtual array for two-dimensional target detection. TX and RX2D are combined to form a two-dimensional virtual array for three-dimensional target detection, providing azimuth and elevation detection capabilities.

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

[0009] Step 1. Set the fixed position of the radar as the origin of the coordinate system; set the radar along the direction of the car's movement as the +x axis; set the radar along the horizontal rightward direction of the car as the +y axis; 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; 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 elevation and azimuth directions; arrange the RX2D antennas in the z-direction; the spacing dz between adjacent antennas in the z-direction is 2.05λ, where λ is the wavelength; set the maximum difference in the y-coordinates and randomly generate the y-coordinates of the RX2D antennas;

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

[0011] Step 3. Combine 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 for objects with 0° azimuth and 0° elevation angles;

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

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

[0014] Step 6. Combine TX1 from the TX obtained in Step 4 with the randomly generated RX1D to form a one-dimensional virtual array, and calculate the main lobe width and side lobe level of the radiation pattern of the one-dimensional virtual array for an object at the 0° position (the object at the 0° position is directly in front of the array).

[0015] Step 7. Repeat steps 5 and 6 until the maximum number of cycles is reached, select the case that satisfies the requirements for sidelobe level and has the narrowest main lobe width, and determine its corresponding RX1D coordinates.

[0016] Furthermore, since the radiation pattern of the antenna is only related to the relative position between the antennas and not to the absolute position between the antennas, TX, RX1D, and RX2D can each be translated in the planar space as a whole until the antennas no longer overlap.

[0017] Further, in step 3, the synthesis of TX and RX2D into a two-dimensional virtual array specifically involves 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] This invention also provides a vehicle-mounted 4D millimeter-wave radar sparse antenna array, comprising 12 transmitting antennas TX and 16 receiving antennas RX, wherein the antennas cannot overlap. The transmitting antennas TX include TX1 and TX2, wherein TX1 has 9 antennas and TX2 has 3 antennas. The receiving antennas RX include RX1D and RX2D, wherein each of RX1D and RX2D has 8 antennas. TX1 and RX1D are combined to form a one-dimensional virtual array for two-dimensional target detection. TX and RX2D are combined to form a two-dimensional virtual array for three-dimensional target detection.

[0019] The beneficial effects of this invention are as follows:

[0020] 1. This invention improves the angular resolution of the pitch direction without increasing the radar pitch dimension.

[0021] 2. This invention improves the angular resolution in the azimuth direction by utilizing a sparse array.

[0022] 3. This invention utilizes a random search algorithm to optimize the main lobe width and side lobe level of the radiation patterns of two-dimensional and one-dimensional virtual arrays. Attached Figure Description

[0023] Figure 1 This is a flowchart of the arrangement method of the present invention;

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

[0025] Figure 3 This is a schematic diagram showing the positional distribution of the radar antenna array elements of the present invention;

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

[0027] Figure 5 This is the orientation pattern of a two-dimensional virtual array for an object located at (0°, 0°);

[0028] Figure 6 This is a cross-sectional view of the orientation of an object located at (0°, 0°) for a two-dimensional virtual array.

[0029] Figure 7 This is a pitch section view of a two-dimensional virtual array for an object located at (0°, 0°).

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

[0031] Figure 9 This is the orientation pattern of a one-dimensional virtual array for an object at 0°. Detailed Implementation

[0032] To better understand the purpose, technical method, and function of this invention, the following detailed description, in conjunction with the accompanying drawings, provides a vehicle-mounted 4D millimeter-wave radar sparse antenna array and its design method.

[0033] like Figure 2 As shown, forward-facing vehicle radar is typically placed on the car's bumper, establishing a Cartesian coordinate system and defining pitch and azimuth directions. For example... Figure 3 As shown, this invention provides a vehicle-mounted 4D millimeter-wave radar sparse antenna array. The radar system used in this invention includes 12 transmitting antennas TX and 16 receiving antennas RX. The antennas cannot overlap. The transmitting antennas TX include TX1 and TX2, wherein TX1 has 9 antennas and TX2 has 3 antennas. The receiving antennas RX include RX1D and RX2D, wherein each of RX1D and RX2D has 8 antennas. 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, with azimuth and elevation detection capabilities.

[0034] The TX and RX1D antennas used in this embodiment of the invention are 25mm long and 3.3mm wide, while the RX2D antenna is 17.5mm long and 7.8mm wide. The millimeter wave wavelength used is approximately 3.9mm, denoted as 1λ.

[0035] like Figure 1 As shown in the figure, 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 origin of the coordinate system; set the radar along the direction of the car's movement as the +x axis; set the radar along the horizontal rightward direction of the car as the +y axis; 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; 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 elevation and azimuth directions; arrange the RX2D antennas in the z-direction; set the spacing dz between adjacent antennas in the z-direction, where dz is 2.05λ, and λ is the wavelength; set the maximum difference in the y-coordinates and randomly generate the y-coordinates of the RX2D antennas.

[0037] Step 2: Arrange TX1 and TX2 in the y-direction, with the y-coordinates of TX1 and TX2 being the same; the distance between TX1 and TX2 in the z-direction is 8dz; fix the positions of the two antennas at both ends of TX1, and randomly generate the y-coordinates of the remaining 10 transmitting antennas TX, requiring that the y-coordinates of the transmitting antennas TX are within the range of the fixed y-coordinates of the two TX1 antennas, and that 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 to form a two-dimensional virtual array. Calculate the main lobe width and side lobe level of the array's radiation pattern for an object with both azimuth and elevation angles of 0°. Assume the coordinate vectors of the transmitting antenna and the transmitting antenna are respectively:

[0039]

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

[0041] Obtain the coordinate vector y of the virtual array element.v z v They are:

[0042]

[0043] The formula for calculating the pattern function AF of the target at (0°, 0°) is:

[0044]

[0045] in, θ is the azimuth angle, and θ is the elevation angle. θ0 represents the azimuth and elevation angles of the target location, respectively, and j is the imaginary unit. The main lobe width is the angle corresponding to a 3dB drop in the peak value of the radiation pattern, and the sidelobe level is the level value of the highest sidelobe. Main lobe width and sidelobe level are two conflicting objectives; improving one objective may lead to deterioration of the other. Therefore, a balance needs to be found so that both can be optimized. The sidelobe level affects the radar's anti-jamming capability. The sidelobe level of a uniform array is -13.25dB. In this invention, the sidelobe level requirement is set to -13.25dB (or lower).

[0046] Step 4: Repeat steps 1, 2, and 3 until the maximum number of loops is reached, which can be freely set; select the case that satisfies the sidelobe level requirement and has the narrowest main lobe width, and determine its corresponding TX and RX2D coordinates. The coordinates obtained in this 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] A two-dimensional virtual array is obtained as follows Figure 4 As shown, the corresponding pattern function is as follows: Figure 5 As shown. The azimuth and elevation cross-sectional views are respectively... Figure 6 and Figure 7 .

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

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

[0054]

[0055] Where, N 1D The unique() function represents the deduplication operation, which determines the number of virtual array elements remaining after removing overlapping virtual array elements.

[0056] Step 7: Repeat steps 5 and 6 until the maximum number of loops is reached, select the case that satisfies the requirements for sidelobe level and has the narrowest main lobe width, and determine its corresponding RX1D coordinates.

[0057] The coordinates obtained in this invention are RX1D_y = [0 3.5 9 12.5 16 20.5 31 35.5], where RX1D_z is a suitable constant. A one-dimensional virtual array is shown below. Figure 8 As shown, its corresponding pattern function is as follows: Figure 9 As shown.

[0058] Because the radiation pattern function of the antenna array depends only on the relative position and not on the absolute position, the obtained coordinate results can be appropriately shifted to obtain... Figure 2 The antennas shown do not overlap.

[0059] In summary, the specific parameters of the radar antenna array arrangement obtained using the method of this invention are as follows: the antenna array occupies 0.85λ (antenna size) + 35.5λ in length and 6.41λ (antenna size) + 16.4λ in height. The two-dimensional elevation resolution is 1.76°, the azimuth resolution is 2.57°, and the maximum sidelobe is -13.88dB. The one-dimensional resolution is 1.1°, and the maximum sidelobe is -14.48dB.

[0060] The above embodiments are only used to illustrate the design concept 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, all equivalent changes or modifications made based on the principles and design ideas disclosed in 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, characterized in that... The 12 transmitting antennas TX are divided into two groups, TX1 and TX2, with 9 antennas in TX1 and 3 antennas in TX2; the 16 receiving antennas RX are also divided into two groups, 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. Specifically, the following steps are included: (1) Set the fixed position of the radar as the origin of the coordinate system, set the radar along the direction of the car's 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 and azimuth directions; arrange the RX2Ds in the z direction; the spacing dz between adjacent antennas in the z direction is 2.05λ, where λ is the wavelength; set the maximum difference of the y coordinates and randomly generate the y coordinates of the RX2Ds; (2) Arrange TX1 and TX2 in the y direction, with the y coordinates of TX1 and TX2 being the same; the distance between TX1 and TX2 in the z direction is 8dz; fix the positions of the two antennas at both ends of TX1, and randomly generate the y coordinates of the remaining 10 transmitting antennas TX, requiring that the y coordinates of the transmitting antennas TX are within the range of the fixed y coordinates of the two TX1 antennas, and that the distance between two adjacent TXs in the y direction is not less than 1λ and is an integer multiple of 0.5λ; (3) Combine TX and RX2D into a two-dimensional virtual array; use the FFT algorithm to calculate the main lobe width and side lobe level of the radiation pattern of the virtual array for an object with both azimuth and elevation angles of 0°; (4) Repeat steps (1) to (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 its 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. The y coordinates of the remaining 6 RX1Ds are randomly generated. The size of the y coordinates of the randomly generated RX1Ds is within the range of the y coordinates of the two fixed RX1D antennas. The distance between two adjacent RX1Ds is not less than 1λ and is an integer multiple of 0.5λ. (6) Combine TX1 in the TX obtained in step (4) with the randomly generated RX1D to form a one-dimensional virtual array, and calculate the main lobe width and side lobe level of the radiation pattern of the one-dimensional virtual array for an object at the 0° position. (7) Repeat steps (5) and (6) until the maximum number of cycles is reached, select the case that satisfies the requirements of sidelobe level and the narrowest main lobe width, and determine its corresponding RX1D coordinates.

2. The design method for a sparse antenna array of a vehicle-mounted 4D millimeter-wave radar according to claim 1, characterized in that, In step (3), the synthesis of TX and RX2D into a two-dimensional virtual array specifically involves adding the horizontal and vertical coordinates of each transmitting antenna TX to the horizontal and vertical coordinates of each RX2D to obtain the positions of 96 virtual array elements.

3. A vehicle-mounted 4D millimeter-wave radar sparse antenna array designed based on the method described in any one of claims 1-2, characterized in that, It includes 12 transmitting antennas (TX) and 16 receiving antennas (RX), and the antennas cannot overlap. The transmitting antennas (TX) include TX1 and TX2, wherein TX1 has 9 antennas and TX2 has 3 antennas. The receiving antennas (RX) include RX1D and RX2D, wherein RX1D and RX2D each have 8 antennas. 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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