A Method for Decoupling Azimuth Angle and Elevation Angle of a Two-Dimensional Cross Array

Abstract

A method for decoupling azimuth and elevation angles of a two-dimensional cross array. The elevation angle of the target is solved by using the interference phase difference of the data received by the cross array elements. The data is compensated according to the phase generated by the elevation angle, and the azimuth angle of the target is calculated by using a one-dimensional angle measurement algorithm for the compensated data. The present invention has a small amount of calculation and increases the unambiguous range of angle measurement, provides a new idea for measuring angles by millimeter-wave vehicle-mounted radars, and is applicable to improving the real-time performance of angle measurement and increasing the field of view of millimeter-wave vehicle-mounted radars.

Description

Technical Field

[0001] The present invention relates to the technical field of millimeter-wave vehicle-mounted radars, and particularly to a two-dimensional cross-array azimuth and elevation decoupling method based on differential phase compensation. Background Art

[0002] Millimeter-wave vehicle-mounted radars are the main sensors for autonomous driving and play a very important role in improving traffic safety. They have the advantages of being unaffected by weather and having low costs compared with lidar. DOA (Direction of Arrival) estimation is one of the main functions of millimeter-wave vehicle-mounted radars. The unambiguous angle measurement range and the real-time performance of angle measurement processing are two key technical indicators of millimeter-wave vehicle-mounted radars.

[0003] Currently, there are two main categories of two-dimensional DOA estimation methods. One is the subspace-based algorithm. The prerequisite for this type of algorithm is that the signals are non-coherent. However, in the actual application of vehicle-mounted radars, due to signal reflections, etc., it is very difficult to ensure that the received signals are non-coherent. The other is the angle search-based method, such as the beamforming method. Using this type of method to estimate the target azimuth and elevation angles requires two-dimensional angle search, and the data processing time is relatively long. Summary of the Invention

[0004] The purpose of the present invention is to provide a two-dimensional cross-array azimuth and elevation decoupling method, which has a small amount of calculation and increases the unambiguous angle measurement range, provides a new idea for the angle measurement of millimeter-wave vehicle-mounted radars, and is applicable to improving the real-time performance of angle measurement and increasing the field of view of millimeter-wave vehicle-mounted radars.

[0005] To achieve the above purpose, the present invention provides a two-dimensional cross-array azimuth and elevation decoupling method, which includes the following steps:

[0006] Step S1: Solve the target elevation angle using the interference phase difference of the data received by the cross elements;

[0007] Step S2: Compensate the data according to the phase generated by the elevation angle;

[0008] Step S3: Calculate the target azimuth angle using a one-dimensional angle measurement algorithm for the compensated data.

[0009] In the above step S1, the target elevation angle is:

[0010]

[0011] where θ e is the target elevation angle. Both rows of the two-dimensional cross-array are uniform arrays. Let the element spacing in the elevation direction be d e , the azimuth position difference between element 2 and element 1 is equal to the azimuth position difference between element 3 and element 2, and both are d a , and so on;

[0012] Taking the origin O as the reference point, the phases of the received data of each array element are as follows:

[0013]

[0014]

[0015]

[0016]

[0017] …

[0018] where θ e and θ a are the elevation angle and azimuth angle of the target respectively;

[0019] The expression for the received data of the array element with an odd serial number i is:

[0020]

[0021] The expression for the received data of the array element with an even serial number i is:

[0022]

[0023] The phase difference between array element 1 and array element 2 is:

[0024]

[0025] The phase difference between array element 3 and array element 2 is:

[0026]

[0027] It can be obtained that:

[0028]

[0029] The mean value of multiple groups of data is calculated and then the elevation angle is calculated.

[0030] In step S2, the received data of each array element is compensated to remove the phase caused by the target elevation angle, and the phase of the compensated data is:

[0031]

[0032]

[0033]

[0034]

[0035] …

[0036]

[0037] The received data of the element with serial number i after compensation is The compensated data is equivalent to the received data of a one-dimensional linear array with an azimuth interval of d a .

[0038] In the step S3, the conventional one-dimensional DOA estimation method is used to solve the target azimuth angle.

[0039] The present invention has significant advantages in the practical application of millimeter-wave vehicle radars, as the two-dimensional cross array can expand the unambiguous angle measurement range compared with the ordinary two-dimensional DOA algorithm, with small computational complexity and high real-time performance. Brief Description of the Drawings

[0040] Figure 1 is a flowchart of a method for decoupling azimuth and elevation angles of a two-dimensional cross array provided by the present invention.

[0041] Figure 2 is a schematic diagram of a two-dimensional cross array.

[0042] Figure 3 is a schematic diagram of an equivalent one-dimensional uniform linear array.

[0043] Figure 4 is the angle measurement result of one-dimensional DOA estimation.

[0044] Figure 5 is the target azimuth angle measurement result of the present invention. Detailed Embodiment

[0045] The following is based on Figures 1 to 5 to specifically describe the preferred embodiments of the present invention.

[0046] As Figure 1 shown, the present invention provides a method for decoupling azimuth and elevation angles of a two-dimensional cross array based on differential phase compensation, including the following steps:

[0047] Step S1, solving the target elevation angle according to the interference phase of the cross elements;

[0048] As Figure 2 shown, both rows of the two-dimensional cross array are uniform arrays. Let the element spacing in the elevation direction be d e , and the azimuth position difference between element 2 and element 1 is equal to the azimuth position difference between element 3 and element 2, and both are d a , and so on;

[0049] Taking the origin O as the reference point, the phases of the received data of each element are:

[0050]

[0051]

[0052]

[0053]

[0054] …

[0055] wherein, θ e and θ a are respectively the pitch angle and azimuth angle of the target;

[0056] The received data expression of the array element with an odd serial number i is:

[0057]

[0058] The received data expression of the array element with an even serial number i is:

[0059]

[0060] The phase difference between array element 1 and array element 2 is:

[0061]

[0062] The phase difference between array element 3 and array element 2 is:

[0063]

[0064] It can be obtained that:

[0065]

[0066] Then the target pitch angle is:

[0067]

[0068] There is also the above relationship between the phase differences of array elements 3 and 4 and array elements 5 and 4. By analogy, multiple sets of data with the above corresponding relationships can be obtained;

[0069] Calculating the average value of multiple sets of data and then calculating the pitch angle can reduce the calculation error of the pitch angle;

[0070] Step S2, compensating the phase caused by the pitch angle of the received data of all array elements;

[0071] According to Step 1, the phase generated by the target pitch angle can be obtained. Compensate the received data of each array element to remove the phase caused by the target pitch angle. The phase of the compensated data is:

[0072]

[0073]

[0074]

[0075]

[0076] …

[0077]

[0078] The received data of the array element with serial number i after compensation is The compensated data is equivalent to the received data of a one-dimensional linear array with an azimuth interval of d a as shown in the equivalent linear array as Figure 3 shown. Since the azimuth interval of the equivalent linear array is halved, the compensated data can increase the unambiguous angle measurement range;

[0079] Step S3: For the received data equivalent to that of a one-dimensional linear array with a halved interval after compensation, the target azimuth angle can be solved by using a conventional one-dimensional DOA estimation method.

[0080] The parameters of the two-dimensional cross-array azimuth and elevation angle decoupling based on differential phase compensation in this embodiment are: the radar carrier frequency is 77 GHz, the elevation array element spacing of the cross-array is 11.215 mm, the azimuth array element interval is 9.15 mm, and the target azimuth angle is set to 10° and the elevation angle is 3°.

[0081] Performing two-dimensional beamforming on the received data gives the angle measurement result as Figure 4 shown. It can be seen from the figure that the azimuth angle measurement result is ambiguous, which is caused by the large azimuth interval of the array. Using the method of the present invention, the calculated target elevation angle result is 3°. According to the elevation angle measurement value, the received data of the array element is compensated, and then one-dimensional DOA estimation is performed on the data to obtain the target azimuth angle. The present invention uses the beamforming method to measure the target azimuth angle, as Figure 5 shown. The azimuth angle measurement result is not ambiguous, and the measured value is 10°, which proves the effectiveness of the angle measurement result of this method. In addition, compared with two-dimensional angle search, the one-dimensional angle search has greatly reduced computational complexity. Therefore, the method of the present invention also has the advantages of simple operation and high real-time performance.

[0082] The present invention can expand the unambiguous angle measurement range compared with the ordinary two-dimensional DOA algorithm for a two-dimensional cross-array, and has small computational complexity and high real-time performance, and has significant advantages in the practical application of millimeter-wave vehicle-mounted radars.

[0083] It should be noted that in the embodiments of the present invention, the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the embodiments and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0084] Although the content of the present invention has been introduced in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation to the present invention. After those skilled in the art have read the above content, various modifications and alternatives to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A decoupling method for azimuth and elevation angles of a two-dimensional cross array, characterized in that, It includes the following steps: Step S1: Solve the target elevation angle by using the interference phase difference of the data received by the cross array elements; The target elevation angle is: Among them, θ e is the target pitch angle. The two rows of arrays of the two-dimensional cross array are both uniform arrays. Let the element spacing in the pitch direction be d e , the azimuth position difference between element 2 and element 1 is equal to the azimuth position difference between element 3 and element 2, and both are d a , and so on; Taking the origin O as the reference point, the phases of the data received by each array element are: Among them, θ e and θ a are respectively the pitch angle and azimuth angle of the target; The expression for the data received by the array elements with odd serial numbers i is: The expression for the data received by the array elements with even serial numbers i is: The phase difference between array element 1 and array element 2 is: The phase difference between array element 3 and array element 2 is: It can be obtained that: Calculate the elevation angle after averaging multiple groups of data; Step S2: Compensate the data according to the phase generated by the elevation angle; Compensate the data received by each array element to remove the phase caused by the target elevation angle. The phase of the compensated data is: The received data of the i-th array element after compensation is The compensated data is equivalent to the received data of a one-dimensional linear array with an azimuth interval of d a ; Step S3: Calculate the target azimuth angle by using a one-dimensional angle measurement algorithm for the compensated data.

2. The two-dimensional cross-array azimuth and elevation decoupling method according to claim 1, wherein In the said step S3, the target azimuth angle is solved by using a conventional one-dimensional DOA estimation method.

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