A wide-area ultra-sparse MIMO radar system high sidelobe / grating lobe suppression method

Abstract

This invention discloses a method for suppressing high sidelobes / grating lobes in a wide-area ultra-sparse MIMO radar system, comprising the following steps: (1) Based on a MIMO radar with sparse node distribution, select one set of array elements, each array element transmits orthogonal waveforms to obtain a joint transmit / receive beam pattern; (2) By changing the carrier frequency, obtain joint beam patterns respectively, multiply the obtained beam patterns to obtain an optimized joint beam pattern; (3) Select another set of array elements, repeat steps (1) and (2) to obtain joint beam pattern results under different array configurations; (4) Multiply the joint beam patterns under all array configurations to obtain the final optimized joint beam pattern. By multiplying the carrier agility results of the joint transmit / receive beam patterns obtained from different carrier frequencies of different MIMO radar transmit / receive array configurations, the joint transmit / receive beam pattern optimization is achieved, resulting in a joint transmit / receive beam pattern with lower sidelobes.

Description

Technical Field

[0001] This invention belongs to the field of radar communication and related fields, and in particular relates to a method for suppressing high sidelobes / grating lobes in a wide-area ultra-sparse MIMO radar system. Background Technology

[0002] To achieve the largest possible virtual aperture, MIMO radars often employ a sparse array configuration. Based on whether the element spacing is a multiple of half a wavelength, they are further divided into sparse arrays and loosely arranged arrays. However, due to antenna size limitations in actual array deployment, the sparse array designed in simulations cannot be implemented. Therefore, the element spacing is often set to a multiple of half a wavelength as a constraint for actual array deployment, i.e., a sparse array configuration is used.

[0003] In distributed MIMO radar, omnidirectional airspace coverage can be achieved when each node transmits orthogonal waveforms. At the receiving end, after the signal is scattered by the target and received by each receiving node, the echo, after signal processing such as matched filtering and pulse accumulation, can be matched and separated based on the relative positions of the transmitting and receiving nodes and the orthogonal transmitted waveform information. This results in virtual transmitted beamforming, or "joint beamforming," based on the received beamforming. Compared to traditional phased array beamforming, joint beamforming has the characteristics of narrower beamwidth and lower sidelobes.

[0004] The high sidelobe suppression problem in wide-area ultra-sparse MIMO radar systems can be addressed by establishing a convex optimization problem with constraints such as the power difference between the main lobe and sidelobes, the location of the main lobe's half-power point, and the sidelobe energy, based on actual requirements. In practical engineering, from a signal processing perspective, methods such as windowing are often used to reduce the amplitude of the joint beam sidelobes. Unlike the high sidelobe suppression method for wide-area ultra-sparse MIMO radar systems designed in this invention, such methods do not fully consider the essential conditions affecting the joint beam pattern, namely, the location information of the transmitting and receiving nodes and the transmitted waveform information. Summary of the Invention

[0005] This invention discloses a high sidelobe / grating lobe suppression method for a wide-area ultra-sparse MIMO radar system. It addresses the conditions affecting the joint beam pattern, namely (1) the location information of the transmitting and receiving nodes; and (2) the transmitted waveform information, used to obtain a joint beam pattern with a higher peak-to-sidelobe ratio. The method includes the following steps:

[0006] Step 1: Based on the MIMO radar with sparse node distribution, select one set of array elements, and each array element transmits orthogonal waveforms at a certain carrier frequency to obtain the transmit-receive joint beam pattern under this array configuration.

[0007] Step 2: Under this array configuration, by changing the carrier frequency, the joint beam pattern at each carrier frequency is obtained. The obtained beam patterns are multiplied together to obtain the joint beam pattern optimized by carrier agility under this array configuration.

[0008] Step 3: Select another set of array elements and repeat steps 1 and 2 to obtain the joint beam pattern results under different array configurations;

[0009] Step 4: Multiply the joint beam patterns of all array configurations to obtain the final optimized joint beam pattern.

[0010] Preferably, step 1 determines the MIMO radar transceiver array configuration, specifically: for sparse arrays, select radar nodes where the angles of the receiving array and the transmitting array relative to the target are almost equal.

[0011] Preferably, the carrier frequency in step 1 is 0.9-1.7 GHz. GHz .

[0012] Preferably, the specific process of joint beamforming in step 1 is as follows: there are M transmitting antennas and N receiving antennas, and the center coordinates of the transmitting node are... The coordinates of each launch node are The center coordinates of the receiving node are The coordinates of each receiving node are The target coordinates are By constructing the guide vector:

[0013]

[0014]

[0015] in, Represented as the length vector from each transmitting node to the center of the array, i.e.

[0016]

[0017] Indicates the beam center The direction vector to the center of the launch node, i.e.

[0018]

[0019] in, The beam center coordinates can be obtained through Coordinate transformation can be performed to obtain (let) )

[0020] Indicate target The direction vector to the center of the launch node, i.e.

[0021]

[0022] in, For the target coordinates, it can be obtained through Coordinate transformation can be performed to obtain (let) ).

[0023] Preferably, step 2 suppresses the sidelobes of the combined transmit and receive beam pattern under the same array by carrier agility. Specifically, it is based on the fact that changing the carrier frequency will not affect the main lobe of the pattern but will only change the sidelobes. The main lobe is accumulated and the sidelobes are canceled by multiplying the patterns under different carrier frequencies, thereby suppressing the high sidelobes of the combined beam pattern.

[0024] Preferably, steps 3 and 4 suppress the sidelobes of the joint beam pattern by changing the MIMO radar transceiver array configuration. Specifically, based on the fact that changing the MIMO radar transceiver array configuration does not affect the main lobe of the pattern but only changes the sidelobes, the main lobe is accumulated and the sidelobes are canceled by multiplying the patterns under different array configurations, thereby suppressing the high sidelobes of the joint beam pattern.

[0025] The beneficial effects of this invention are as follows: by multiplying the carrier agility results of the combined transmit and receive beam patterns obtained from different carrier frequencies of different MIMO radar transmit and receive arrays, the combined transmit and receive beam patterns with lower sidelobes are optimized. Attached Figure Description

[0026] Figure 1 This is a flowchart of a high sidelobe / grating lobe suppression method for a wide-area ultra-sparse MIMO radar system according to the present invention.

[0027] Figure 2 The optimized radiation pattern after carrier agility is used for simulation.

[0028] Figure 3 To obtain the final optimized beam direction result of the combined transmit and receive beams by repeating the process more than two times. Detailed Implementation

[0029] The specific implementation of the present invention will now be described in detail with reference to the method flowchart attached to the instruction manual.

[0030] The following is a principle demonstration of the high sidelobe / grating lobe suppression method for a wide-area ultra-sparse MIMO radar system according to the present invention:

[0031] The specific process of joint beamforming is as follows: there are M transmitting antennas and N receiving antennas, and the center coordinates of the transmitting node are... The coordinates of each launch node are The center coordinates of the receiving node are The coordinates of each receiving node are The target coordinates are By constructing the guide vector

[0032]

[0033]

[0034] in, Represented as the length vector from each transmitting node to the center of the array, i.e.

[0035]

[0036] Indicates the beam center The direction vector to the center of the launch node, i.e.

[0037]

[0038] in, The beam center coordinates can be obtained through Coordinate transformation can be performed to obtain (let) )

[0039] Indicate target The direction vector to the center of the launch node, i.e.

[0040]

[0041] in, For the target coordinates, it can be obtained through Coordinate transformation can be performed to obtain (let) )

[0042] Similarly, construct the guiding vector.

[0043]

[0044]

[0045] in, Represented as the length vector from each receiving node to the center of the array. Indicates the beam center The direction vector to the center of the receiving node. Indicate target The direction vector to the center of the receiving node is calculated in the same way as above, and a joint steering vector can then be constructed.

[0046]

[0047] in, If the Kronecker product is represented, then the joint beamforming output is...

[0048]

[0049] The superscript H indicates conjugate transpose.

[0050] make , , ,

[0051] The expression for the joint beam pattern is:

[0052]

[0053] Observing the joint beam pattern expression, it is easy to see that the pattern depends only on the following two conditions: (1) the position information of the transmitting and receiving nodes; (2) the wavelength of the transmitted waveform (carrier frequency). When radar nodes with almost equal angles between the receiving and transmitting arrays relative to the target are selected, it can be assumed that... , ,when hour, The maximum value is achieved. When the location information of the transmitting and receiving nodes or the carrier frequency are changed, the main lobe of the radiation pattern ( The maximum value will not change, but the sidelobes of the radiation pattern will be different. By multiplying the radiation patterns under different conditions, a transmit-receive joint beam pattern with lower sidelobes can be obtained.

[0054] like Figure 1 As shown, the high sidelobe / grating lobe suppression method for a wide-area ultra-sparse MIMO radar system of the present invention includes the following steps:

[0055] Step 1: Based on a MIMO radar with sparse node distribution, the distance between radar nodes is an integer multiple of half the wavelength. Select radar nodes where the angles of the receiving array and the transmitting array relative to the target are almost equal. Each transmitting node transmits orthogonal waveforms at a certain carrier frequency to obtain the joint transmit and receive beam pattern under this array configuration and carrier frequency.

[0056] Step 2: Perform "carrier agility" under this array configuration, that is, by changing the carrier frequency, obtain the joint beam pattern at each carrier frequency, and multiply the obtained beam patterns to obtain the joint beam pattern optimized by carrier agility under this array configuration.

[0057] Step 3: Select another set of array elements. Note that the selected array elements must still satisfy the constraint that the angles of the receiving array and the transmitting array relative to the target are almost equal. Repeat steps 1 and 2 to obtain the joint beam pattern results under different array configurations.

[0058] Step 4: Multiply the joint beam patterns of all arrays to obtain the final optimized joint beam pattern with lower sidelobes.

[0059] Simulation results explanation:

[0060] Simulations were performed using a linear array with a 500m aperture. Thirty array elements were randomly selected at integer multiples of half the wavelength, and the carrier frequency was plotted. , , The transmit and receive joint beam pattern, and the optimized beam pattern after carrier agility, are shown in the following results. Figure 1 .

[0061] like Figure 1 As shown, after carrier agility, the peak value of the sidelobe in the transmit / receive joint beam pattern decreases by approximately 20 dB.

[0062] Repeat the process two or more times to obtain the transmit-receive joint beam pattern results after the download wave agility of the three different array configurations. Then, fuse the beam patterns from the different array configurations to obtain the final optimized transmit-receive joint beam pattern result, as shown below. Figure 2 .

[0063] like Figure 2 As shown, the peak value of the sidelobe in the transmit-receive joint beam pattern optimized by this method is reduced by approximately 90 dB, which is a good result.

[0064] The key elements of this invention address the conditions affecting the joint beam pattern: (1) the location information of the transceiver nodes; and (2) the transmitted waveform information. Based on the fact that changing the location information of the transceiver nodes or the carrier frequency does not change the main lobe of the beam pattern, but the side lobes differ, this invention optimizes the transceiver joint beam pattern by performing carrier agility on the joint beam patterns obtained from different carriers under the same array configuration, and then fusing the joint beam patterns obtained after carrier agility for different array configurations. The optimized transceiver joint beam pattern has a higher peak-to-side-lobe ratio and exhibits good high side-lobe suppression performance in ultra-sparse MIMO radar systems. This invention is not limited to one-dimensional linear array scenarios; it is also applicable to area array scenarios.

Claims

1. A method for suppressing high sidelobes / grating lobes in a wide-area ultra-sparse MIMO radar system, characterized in that, Includes the following steps: Step 1: Based on the MIMO radar with sparse node distribution, select one set of array elements, and each array element transmits orthogonal waveforms at a certain carrier frequency to obtain the transmit-receive joint beam pattern under this array configuration. Step 2: Under this array configuration, by changing the carrier frequency, the joint beam pattern at each carrier frequency is obtained. The obtained beam patterns are multiplied together to obtain the joint beam pattern optimized by carrier agility under this array configuration. Step 3: Select another set of array elements and repeat steps 1 and 2 to obtain the joint beam pattern results under different array configurations; Step 4: Multiply the joint beam patterns of all array configurations to obtain the final optimized joint beam pattern; Step 1 determines the MIMO radar transceiver array configuration, specifically: for sparse arrays, select radar nodes where the receiving and transmitting arrays have equal angles relative to the target.

2. The high sidelobe / grating lobe suppression method for a wide-area ultra-sparse MIMO radar system as described in claim 1, characterized in that, The carrier frequency mentioned in step 1 is 0.9 GHz. GHz 1.3 GHz or 1.7 GHz .

3. The high sidelobe / grating lobe suppression method for a wide-area ultra-sparse MIMO radar system as described in claim 1, characterized in that, Step 1, the joint beamforming process, is as follows: There are M transmitting antennas and N receiving antennas. The center coordinates of the transmitting node are... The coordinates of each launch node are The center coordinates of the receiving node are The coordinates of each receiving node are The target coordinates are By constructing the guide vector: ； ； in, Represented as the length vector from each transmitting node to the center of the array, i.e. ； Indicates the beam center The direction vector to the center of the launch node, i.e. ； in, For the beam center coordinates, through By performing a coordinate transformation, let r = 1; Indicate target The direction vector to the center of the launch node, i.e. ； in, For the target coordinates, through The coordinates are transformed to obtain the result.

4. The high sidelobe / grating lobe suppression method for a wide-area ultra-sparse MIMO radar system as described in claim 1, characterized in that, Step 2 suppresses the sidelobes of the combined transmit and receive beam pattern under the same array by carrier agility. Specifically, since changing the carrier frequency does not affect the main lobe of the pattern but only changes the sidelobes, the main lobe is accumulated and the sidelobes are canceled by multiplying the patterns under different carrier frequencies, thereby suppressing the high sidelobes of the combined beam pattern.

5. The high sidelobe / grating lobe suppression method for a wide-area ultra-sparse MIMO radar system as described in claim 1, characterized in that, Steps 3 and 4 suppress the sidelobes of the joint transmit and receive beam pattern by changing the MIMO radar transceiver array configuration. Specifically, since changing the MIMO radar transceiver array configuration does not affect the main lobe of the pattern but only changes the sidelobes, the main lobe is accumulated and the sidelobes are canceled by multiplying the patterns under different array configurations, thereby suppressing the high sidelobes of the joint beam pattern.

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