A radar target angle simulation method based on near-field spatial synthesis

Abstract

The present invention proposes a radar target angle simulation method based on near-field spatial synthesis. The angle range of a single binary array simulation is expanded to 1.5 to 2.3 times the radar beam width, so that the normal direction of the simulator's transmitting antenna array is consistent with the normal direction of the radar receiving antenna, and the radar target angle simulation is performed by changing the transmitting antenna transmission signal amplitude ratio. Compared with the traditional method, the present invention effectively improves the angle simulation range of a single binary array. Under the same angle simulation range requirement, fewer array elements are required, which greatly saves costs.

Description

Technical Field

[0001] The invention relates to a radar target angle simulation method based on near-field space synthesis, and belongs to the field of radar testing. Background Art

[0002] With the rapid development of assisted driving and autonomous driving, the demand for vehicle-mounted millimeter-wave radar is increasing day by day. Radars require target simulators during research and development and mass production testing. The existing angle simulation methods mainly include mechanical slides and traditional far-field angle simulation methods. Each of them has its own limitations: the manufacturing process of the mechanical rocker arm of the arc mechanical slide is complex, which is prone to large simulation errors. Although the manufacturing process of the linear mechanical slide is relatively simple and easy to install, it requires certain compensation for the distance, speed, and signal power of the target, which increases the amount of calculation; the traditional far-field angle simulation method needs to meet the far-field conditions, so the angle simulation range is small. In order to increase the angle simulation range, the number of binary arrays needs to be increased, which greatly increases the cost. Summary of the invention

[0003] In view of the above technical problems, the present invention proposes a radar target angle simulation method based on near-field spatial synthesis.

[0004] The present invention is achieved through the following technical solutions.

[0005] A radar target angle simulation method based on near-field spatial synthesis,

[0006] The angle range of a single binary array simulation is expanded to 1.5 to 2.3 times the radar beam width, so that the normal direction of the simulator's transmitting antenna array is consistent with the normal direction of the radar receiving antenna, and the radar target angle simulation is performed by changing the amplitude ratio of the transmitting antenna's transmitting signal.

[0007] Beneficial effects of the present invention:

[0008] Compared with the traditional method, the present invention effectively improves the angular simulation range of a single binary array, requires fewer array elements under the same angular simulation range requirement, and greatly saves costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a schematic diagram of an angle simulation method with two radar receiving array elements in a specific implementation manner of the present invention;

[0010] Figure 2 is the simulation result of the near-field spatial angle simulation method in the specific implementation mode of the present invention;

[0011] Figure 3 is a simulation result of the ratio of the simulated angle range to the radar beam width in a specific embodiment of the present invention;

[0012] Figure 4 It is an amplitude compensation curve for ensuring the consistency of target RCS in a specific implementation manner of the present invention. DETAILED DESCRIPTION

[0013] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0014] A radar target angle simulation method based on near-field spatial synthesis in this specific implementation method specifically includes:

[0015] The angle range of a single binary array simulation is expanded to 1.5 to 2.3 times the radar beam width, so that the normal direction of the simulator's transmitting antenna array is consistent with the normal direction of the radar receiving antenna, and the radar target angle simulation is performed by changing the amplitude ratio of the transmitting antenna's transmitting signal.

[0016] In specific implementation, when the simulator has two transmitting antenna arrays, i.e., a two-element array, and the number of radar receiving array elements is also two, the angle calculation formula of the simulated target relative to the radar equivalent receiving center is as follows:

[0017]

[0018]

[0019] Among them, d is the array element spacing of the radar antenna array, a is the amplitude ratio of the binary array transmission signal, is the phase difference caused by the path difference of the transmitted signal reaching each radar array element, and λ is the wavelength.

[0020] For example, Figure 1 As shown in the schematic diagram of the angle simulation method with a radar receiving array element number of 2, point A represents the position of the target simulator transmitting antenna 1, point B represents the position of the target simulator transmitting antenna 2, point a represents the position of the radar receiving antenna 1, point b represents the position of the radar receiving antenna 2, the normal direction of the target simulator and the radar are in the same direction, that is, the line segment ab and the perpendicular bisector of the line segment AB are the same. Assuming that the distance between the radar and the simulator satisfies the condition that it is greater than the interval d between the radar receiving antennas a and b, the phase difference of the signal transmitted by antenna 1 at point A received by antenna a and antenna b is only related to the distance between antennas a and b, and the angle α of line segment AO relative to the perpendicular bisector. Similarly, the phase difference of the signal transmitted by antenna 2 at point B is also only related to d and α.

[0021] The distance between radar receiving antennas a and b is d. Assume that the path of the signal transmitted by antenna 1 to the receiving antenna a is R. Aa The phase difference caused by The wave path of the signal transmitted by antenna 1 to the receiving antenna b is R AbThe phase difference is By analogy, the wave path between point B and point a is R Ba The phase difference is The wave path between point B and point b is R Bb The phase difference is The composite complex signal received by antenna a is x a , the composite complex signal received by antenna b is x b , the phase difference between the two received composite complex signals is The amplitude of the signal transmitted by antenna 1 is a1, the amplitude of the signal transmitted by antenna 2 is a2, and the initial phase difference between the two signals transmitted by antenna 1 and 2 is Φ, then:

[0022]

[0023]

[0024]

[0025] Assuming that the simulated point target D is on the line segment OB, the angle θ of the target is positive. From the geometric relationship, we can know that:

[0026] ΔR=R Ab -R Aa =R Bb -R Ba

[0027] R Aa =R Bb , R Ab =R Ba

[0028]

[0029] The phase difference caused by the wave path difference ΔR is α is the angle of the simulated target:

[0030]

[0031] Let the amplitude ratio be a=a1 / a2, and further organize it:

[0032]

[0033]

[0034] When the initial phase difference of the signals transmitted by antennas 1 and 2 hour:

[0035]

[0036]

[0037] Combined with the phase difference formula The angle formula of the simulated point D relative to the radar equivalent receiving center is as follows:

[0038]

[0039] In specific implementation, when the simulator has two transmitting antenna arrays and the number of radar receiving array elements is N, the calculation formula of the synthetic signal amplitude F(k) is as follows:

[0040]

[0041]

[0042] Where N is the number of radar receiving antenna elements, d is the radar antenna array element spacing, θ FOS is the opening angle of the two transmitting antennas of the target simulator relative to the radar, and θ is the azimuth angle of the current simulated target.

[0043] In specific implementation, when the simulator has N transmitting antenna arrays and N radar receiving array elements, every two transmitting antennas of the simulator form a binary array. When performing angle simulation, first determine which binary array's angle simulation range the simulated angle is within based on the relative positions of the radar and the simulator, then control the simulator to select the binary array at a suitable position, and finally the selected binary array performs angle simulation.

[0044] For example, when the number of radar receiving array elements is N, assuming that the number of radar receiving antenna array elements is N, N>2, taking the center point of the radar linear array as the reference point, the signal transmitted by antenna 1 received by the nth array element can be expressed as follows. Among them, FOS (Field of Simulation) is the angle between the two antennas 1 and 2 of the target simulator relative to the radar. Use the variable θ FOS express.

[0045]

[0046] The signal transmitted by antenna 2 received by the nth array element can be expressed as:

[0047]

[0048] Where A is the normalized amplitude of the signal transmitted by antenna 1, and 1-A is the amplitude of the signal transmitted by antenna 2. When A is in the interval (0,1), the amplitude ratio of the two signals can be from 0 to infinity, and N is the number of array elements of the radar receiving antenna.

[0049] Then the synthetic signal expression of the receiving linear array is:

[0050]

[0051] make Simplifying further:

[0052]

[0053] When the number of radar receiving antenna elements N, the interval d between radar receiving antenna elements, and the opening angle FOS of the two transmitting antennas of the target simulator relative to the radar are determined, it can be seen from the formula that, since k is proportional to sinθ, when sinθ is the horizontal axis, the amplitude spectrum of the synthetic signal is the superposition of two sinc shape functions multiplied by different proportional coefficients.

[0054] like Figure 2 From the simulation results of the directional pattern change process, it can be seen that the synthesized directional pattern is the superposition of two sinc function-shaped beam patterns, which also confirms the formula for the output of the synthetic signal of multiple receiving array elements derived above. As the FOS value increases, the two sinc function-shaped beam patterns gradually separate and can no longer be synthesized into a peak. As the number of antenna array elements increases, the FOS value at which distortion begins to occur becomes smaller, and the angle range that can be simulated decreases. This is because the number of antenna array elements increases, the antenna size increases, and the 3dB beam width of the radar antenna beam pattern becomes smaller. The critical value of FOS distortion is related to the radar 3dB beam width, which is generally about 1.5 to 2.3 times the radar 3dB beam width. This is proved below:

[0055] The synthesized directional pattern is the result of the superposition of two sinc function-shaped beam patterns after translation. The translation distance contains the FOV. If the translation distance is too large, two peaks will appear and the maximum value will no longer be taken at the 0° angle. When simulating a 0° angle, the coefficients of the two sinc functions are equal, which will not affect whether the maximum or minimum value is taken. For the sake of simplicity in analysis, the coefficient can be changed to 1. The angle spectrum expression is as follows:

[0056]

[0057] When G”(0)=0, two peaks appear; because the sinc function is symmetrical, and the two sinc functions are exactly the same, the translation distance is also the same, and only the translation direction is different, so the second-order derivatives of the two sinc functions at θ=0 are equal. The problem is transformed into finding the horizontal coordinate when the second-order derivative of a single sinc function is equal to 0 after translation. We can start by analyzing the original sinc function before translation.

[0058]

[0059] make F sinc1 When the second derivative of (θ) is 0, x = 2.082, we get:

[0060]

[0061] When the beam points to an angle of 0°, the radar 3dB beam width is:

[0062] when When the change occurs, the ratio of (FOV)max to 3dB beam width is simulated by computer. Figure 3 The results show that the simulated angular range can reach about 1.5 to 2.3 times the radar 3dB beamwidth.

[0063] When the default radar is a 360° omnidirectional array element, the amplitude of the synthetic signal can directly reflect the target RCS. Therefore, reducing the amplitude of the transmitted signal on one side for angle simulation will inevitably lead to a decrease in the amplitude of the synthetic signal. In order to ensure the RCS consistency of the simulated target, the amplitude of the transmitted signal needs to be increased accordingly at a certain ratio.

[0064] It can be seen that the angle range that can be simulated by a single binary array is increased by the above method, thereby reducing the number of binary arrays.

[0065] Figure 4 It shows that at fov / θ bw When the value of is different, with the angle of 0° as the reference, the amplitude of the antenna transmitting signal needs to increase in proportion with the angle. The larger the absolute value of the simulated angle, the greater the amplitude needs to increase; at the same simulated angle, the smaller the ratio of FOS to the radar 3dB beam width, the greater the amplitude needs to increase. According to the different fov / θ selected bw , find the corresponding statistical curve of the relationship between the amplitude increase ratio and the angle, and adjust the amplitude of the transmitted signal so that the amplitude of the synthetic target at different simulated target angles is the same, thereby ensuring the consistency of the simulated target rcs.

[0066] The near-field space synthesis angle simulation method will sacrifice a certain degree of angle accuracy. The angle accuracy calculation formula under this method is as follows:

[0067]

[0068] Among them, θ bw is the radar 3dB beam width, snr is the signal-to-noise ratio, k is the proportional factor, usually 1.4 to 2, y is the 3dB beam width expansion coefficient, and p is a constant, usually 3 to 5. Although the angle accuracy is reduced, multi-target resolution can still be achieved with other features such as distance and speed.

[0069] To sum up, the present invention provides a near-field spatial synthetic radar target angle simulation method based on an improved binary array angle simulation method. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A radar target angle simulation method based on near-field spatial synthesis, characterized in that: include: The angle range of a single binary array simulation is expanded to 1.5 to 2.3 times the radar beam width, so that the normal direction of the simulator's transmitting antenna array is consistent with the normal direction of the radar receiving antenna. The radar target angle is simulated by changing the transmit antenna transmit signal amplitude ratio. Specifically, when the simulator has two transmit antenna arrays and the number of radar receiving array elements is also two, the angle calculation formula of the simulated target relative to the radar equivalent receiving center is as follows: Among them, d is the array element spacing of the radar antenna array, a is the amplitude ratio of the binary array transmission signal, is the phase difference caused by the path difference of the transmitted signal reaching each radar array element, and λ is the wavelength.

2. A radar target angle simulation method based on near-field spatial synthesis as claimed in claim 1, characterized in that: When the simulator has two transmitting antenna arrays and the number of radar receiving array elements is N, the calculation formula for the synthetic signal amplitude F(k) is as follows: Where A is the normalized amplitude of the signal transmitted by antenna 1, N is the number of radar receiving antenna elements, d is the interval between radar antenna array elements, and θ FOS is the opening angle of the two transmitting antennas of the target simulator relative to the radar, and θ is the azimuth angle of the current simulated target.

3. A radar target angle simulation method based on near-field spatial synthesis as claimed in claim 2, characterized in that: When the simulator's transmitting antenna array is N and the number of radar receiving array elements is N, every two transmitting antennas of the simulator form a binary array for angle simulation.

4. A radar target angle simulation method based on near-field spatial synthesis as claimed in claim 3, characterized in that: The angle simulation first determines within which binary array's angle simulation range the simulated angle falls according to the relative positions of the radar and the simulator, then controls the simulator to select a binary array at a suitable position, and finally performs angle simulation using the selected binary array.

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