Method for improving angular accuracy of sparse array antenna of millimeter wave radar

Abstract

The invention relates to a method for improving angular accuracy of a sparse array antenna of a millimeter wave radar. The method comprises the following steps: obtaining a real receiving channel of transmitting antennas of a millimeter wave radar antenna array comprising three transmitting antennas and four receiving antennas; determining virtual channel cavity positions, and calculating distances between 16 virtual channel positions and the first receiving channel; virtual expansion signals are calculated, and 16 virtual expansion signals are respectively inserted into virtual channel cavity positions to obtain a new uniform antenna array; performing FFT (Fast Fourier Transform) processing on each uniform array signal base output by the new antenna array to obtain angle data of a target; according to the method, the hole signals of the sparse array are complemented through virtual extension, the equivalent uniform linear array is generated, the problems that in the prior art, the cost of a uniform linear array is high, and under-sampling is caused by holes existing in the sparse array are solved, meanwhile, spectrum sidelobes are effectively restrained, and the angle measurement precision is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of millimeter wave radars, and in particular to a method for improving the angular accuracy of a millimeter wave radar sparse array antenna. Background Art

[0002] Multiple-input multiple-output (MIMO) radar technology has attracted wide attention in the field of automotive radar technology. Compared with traditional single-input multiple-output (SIMO) radar, MIMO radar can synthesize a large-aperture virtual array through fewer transmitting and receiving wires, thereby achieving high angular resolution; MIMO radar uses multiple transmitting antennas to simultaneously transmit mutually orthogonal signals to illuminate the target, and multiple receiving antennas receive and process the target echo signals to extract information such as the target's spatial position and motion state; MIMO radar has the advantages of higher processing dimensions, more efficient use of the transmit and receive apertures, and higher angular resolution; uniform linear arrays as MIM The traditional application form of O radar has the advantages of simple structure and convenient signal processing. However, according to the Nyquist sampling theorem, the element spacing of the uniform linear array cannot exceed half a wavelength, otherwise grating lobe problems will occur, resulting in angle measurement errors. In practical applications, if the angular resolution of automotive radar is to be improved, it is necessary to ensure that the radar array aperture is large enough. In a uniform array, under the premise that the element spacing meets the requirements, a larger array aperture can only be achieved by increasing the number of elements, which usually greatly increases the cost. The use of a sparse array can meet the array aperture requirements while using a relatively small number of elements, thereby achieving high angular resolution.

[0003] However, there are holes in the sparse array antenna channel. Directly filling the holes with zeros will cause undersampling, which will lead to increased spectral sidelobes during angle measurement and affect the accuracy of angle measurement. Especially in multi-target scenarios, the sidelobes of high-energy targets are likely to cover the mainlobes of low-energy targets, causing angle measurement errors. Summary of the invention

[0004] In view of this, the present invention provides a method for improving the angular accuracy of a millimeter-wave radar sparse array antenna, which can solve the problem of undersampling of a virtual antenna array and improve the accuracy of extracting target angle information.

[0005] To achieve the above object, the present invention provides a method for improving the angular accuracy of a millimeter wave radar sparse array antenna, comprising the following steps: S1, obtaining a real receiving channel of a millimeter wave radar antenna array transmitting antenna including 3 transmitting antennas and 4 receiving antennas; S2, determining the virtual channel hole position, and calculating the distance between the 16 virtual channel positions and the first receiving channel; S3, calculating virtual extension signals, and inserting 16 virtual extension signals into the virtual channel hole positions respectively to obtain a new uniform antenna array; S301. Calculate the virtual extended signals at the positions of 16 virtual channel holes , and the expression is: ; Among them, represents the signal received by the real receiving channel, represents the conjugate of represents the virtual extended signal at the k-th hole position; The difference at the k-th hole position also needs to satisfy: ; Among them, represents the distance between the th hole position and the first receiving channel, respectively represent the th and the th real receiving channels; S302. Insert the 16 virtual extended signals into the corresponding hole positions respectively; S4. Perform FFT processing on each uniform array signal output by the new antenna array to obtain the angle data of the target.

[0006] Preferably, the millimeter-wave radar antenna array includes 3 transmitting antennas and 4 receiving antennas. The 4 receiving channels of the transmitting antenna The expression is: ; ; The 4 receiving channels of the transmitting antenna The expression is: ; ; The 4 receiving channels of the transmitting antenna The expression is: ; ; Among them, represents the complex envelope of the incident signal.

[0007] Preferably, calculate the distances between the 16 virtual channel holes and the first receiving channel to obtain the hole position array: ; Among them, d represents the half-wavelength.

[0008] Preferably, the distance between the hole position and the reference array element is 2d. The two real channels with a real channel spacing of 2d in the antenna array are , , the virtual extended signal at the hole position satisfies: ; The virtual extended signal expression of the hole position is: ; Similarly, the interpolation at the hole position is calculated; ; ; ; ; ; The 16 virtual extended signals and 12 actual received signals form a uniform array with an equivalent number of array elements of 28 and an element spacing of half a wavelength.

[0009] Compared with the prior art, the beneficial effects of the present invention are: Without increasing the actual number of array elements, the present invention equivalently transforms a sparse array into a uniform linear array with 28 array elements and an element spacing of half a wavelength through virtual extension. At the same time, the hole signals in the sparse array antenna are complemented, effectively solving the under-sampling problem, avoiding the increase of spectral sidelobes caused by direct zero-padding processing, improving the accuracy of angle measurement and achieving higher angular resolution, meeting the requirements of high-precision angle measurement in applications such as automotive radars; moreover, by reducing the spectral sidelobes, the present invention reduces the masking effect of the sidelobes of high-energy targets on the main lobes of low-energy targets in a multi-target scenario, improving the anti-interference ability of the radar in a complex environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a schematic diagram of the half-wavelength spacing of each array of the present invention relative to the reference channel 0; Figure 2 is a schematic diagram of the arrangement position of the virtual channels of the antenna of the present invention Figure 3 is a schematic diagram of the antenna array of the present invention receiving an incident signal. SPECIFIC EMBODIMENTS

[0011] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following describes in detail the specific embodiments, structures, features, and effects of the present invention in combination with the accompanying drawings and preferred embodiments.

[0012] In this embodiment, it is assumed that there is a narrowband incident signal in the far field of space, and the included angle between the incident signal and the radar discovery is , the path difference between any two array elements is , taking the first receiving array element as the reference unit, the path difference between the second array element and the first array element is , the path difference between the third array element and the first array element is , and so on, the path difference between the Mth array element and the first array element is , so the time delay of the incident signal reaching the Mth array element relative to the reference array element is: ; where represents the speed of light; The expression of the incident signal received by the first array element is: ; ; where represents the complex envelope of the incident signal, , , respectively represent the amplitude, frequency and phase of the incident signal, represents the wavelength of the signal; The expression of the incident signal received by the Mth array element is: ; Since the signals received by the array are all far-field narrowband signals, it is considered that the incident wave to the array is a plane wave and the incident signal sources are uncorrelated, then: ; ; Let , then ; Writing the incident signals of the uniform linear array of M receiving array elements in vector form: ; Then the expression of the received signal vector is: ; For the signal , the expression of the steering vector is: ; Then the expression of the incident signals of the uniform linear array of M receiving array elements is: ; Similarly, when there are k signal sources, the signal model can be expressed as: ; The millimeter-wave radar antenna array in this embodiment includes 3 transmitting antennas and 4 receiving antennas, and the corresponding positions of the antenna virtual channels are asFigure 2 as shown, where represents the transmitting antenna 's receiving channel represents the transmitting antenna 's receiving channel represents the transmitting antenna 's receiving channel Figure 1 is a schematic diagram of the half-wavelength spacing of each array relative to the reference channel 0, where is the hole in the array , that is, the virtual interpolation signal to be generated, and the element position interval d represents half a wavelength; Due to the use of a sparse array in the antenna array design, holes will be formed in the array, resulting in undersampling and thus an increase in the sidelobes of the spectrum during the angle measurement process. When multiple targets exist, it is easy for the sidelobes of the target with higher energy to cover the main lobe of the target with lower energy, resulting in angle measurement errors. Therefore, it is necessary to fill the holes to reduce the sidelobes.

[0013] This embodiment provides a method for improving the angular accuracy of a sparse array antenna of a millimeter-wave radar, including the following steps: S1. Obtain the true receiving channels of the transmitting antennas of the millimeter-wave radar antenna array including 3 transmitting antennas and 4 receiving antennas; The transmitting antenna 's 4 receiving channels The expression is: ; The transmitting antenna 's 4 receiving channels The expression is: ; The transmitting antenna 's 4 receiving channels The expression is: ; Wherein, represents the complex envelope of the incident signal.

[0014] S2. Determine the positions of the virtual channel holes, calculate the distances between the 16 virtual channel positions and the first receiving channel, and obtain the hole position array: ; Wherein, d represents half a wavelength.

[0015] S3. Calculate the virtual extended signals, and insert the 16 virtual extended signals at the positions of the virtual channel holes respectively to obtain a new uniform antenna array; S301. Calculate the virtual extended signals at the positions of the 16 virtual channel holes The expression is: ; Among them, represents the signal received by the real receiving channel, represents the conjugate of, represents the virtual extended signal at the k-th hole position; The difference at the k-th hole position also needs to satisfy: ; Among them, represents the spacing between the k-th hole position and the first receiving channel, respectively represent the th and th real receiving channels; S302. Insert the 16 virtual extended signals into the corresponding hole positions respectively; As Figure 1 shown, the hole position is at a distance of 2d from the reference array element . The two real channels with a real channel spacing of 2d in the antenna array are , . The virtual extended signal at the hole position satisfies: ; The virtual extended signal expression at the hole position is: ; Similarly, the interpolation at the hole position is calculated; ; ; ; ; ; S303. Insert the 16 virtual extended signals into the corresponding hole positions respectively. The 16 virtual extended signals and the 12 actual received signals form a uniform array with an equivalent number of array elements of 28 and an array element spacing of half a wavelength. Use these 28 signals during the angle measurement process to achieve the purpose of reducing sidelobes.

[0016] S4. Perform FFT processing on the 28 uniform array signals output by the new antenna array to obtain more accurate target angle data.

[0017] The above are only the preferred embodiments of the present invention and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the disclosed technical content without departing from the technical solution of the present invention. However, as long as it does not depart from the technical solution content of the present invention, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for improving the angular accuracy of a millimeter wave radar sparse array antenna, characterized in that: The following steps are involved: S1, obtaining a real receiving channel of a millimeter wave radar antenna array transmitting antenna including 3 transmitting antennas and 4 receiving antennas; S2, determining the virtual channel hole position, and calculating the distance between the 16 virtual channel positions and the first receiving channel; S3, calculating virtual extension signals, and inserting 16 virtual extension signals into the virtual channel hole positions respectively to obtain a new uniform antenna array; S301, calculating the virtual extension signals of the hole positions of 16 virtual channels , the expression is: ； in, Indicates the signal received by the real receiving channel. express The conjugate of A virtual extension signal representing the k-th hole position; The difference of the kth hole position also needs to satisfy: ； in, Indicates The distance between the hole position and the first receiving channel, Respectively represent and A real receiving channel; S302, inserting 16 virtual extension signals into corresponding hole positions respectively; S4. Perform FFT processing on each uniform array signal output by the new antenna array to obtain angle data of the target.

2. The method for improving angular accuracy of a millimeter wave radar sparse array antenna according to claim 1, characterized in that: The millimeter wave radar antenna array includes 3 transmitting antennas and 4 receiving antennas. 4 receiving channels The expression is: ； Transmitting antenna 4 receiving channels The expression is: ； Transmitting antenna 4 receiving channels The expression is: ； in, represents the complex envelope of the incident signal.

3. The method for improving angular accuracy of a millimeter wave radar sparse array antenna according to claim 2, characterized in that: Calculate the distance between the 16 virtual channel holes and the first receiving channel to get the hole position array: ； Here, d represents half wavelength.

4. The method for improving angular accuracy of a millimeter wave radar sparse array antenna according to claim 3, characterized in that: Hole location Distance reference element The spacing between the two real channels in the antenna array is 2d. , , the hole position The virtual extension signal satisfies: ； Hole location The virtual extended signal expression is: ； Similarly, the hole position is calculated Interpolation at ; ； ； ； ； ； The 16 virtual extended signals and the 12 actual received signals form a uniform array with an equivalent number of 28 array elements and an array element spacing of half a wavelength.

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