阅读说明：本技术 雷达目标方向确定方法、系统及计算机可读存储介质 (Radar target direction determination method, system and computer readable storage medium ) 是由 叶峰 于 2021-09-10 设计创作，主要内容包括：本发明涉及一种雷达目标方向确定方法、系统及计算机可读存储介质,属于雷达技术领域。采用了该发明的雷达目标方向确定方法,所述的雷达包括一根发射天线和三根接收天线,所述的方法利用接收回波信号,计算获得两个目标的反射信号叠加后的幅度和相位,利用数学模型计算出两个目标的反射信号在叠加之前的幅度及相位,准确估算两个目标的波达方向,确定目标方向。从而有效解决了相干信号的问题,实现分辨率高的目标定位,且本发明的雷达目标方向确定方法中计算过程简单,对应硬件环境要求低,且适用范围相当广泛。(The invention relates to a method and a system for determining the direction of a radar target and a computer readable storage medium, belonging to the technical field of radars. The method comprises the steps of calculating and obtaining the amplitude and the phase of the superposed reflected signals of two targets by utilizing the received echo signals, calculating the amplitude and the phase of the reflected signals of the two targets before superposition by utilizing a mathematical model, accurately estimating the directions of arrival of the two targets and determining the direction of the target. Therefore, the problem of coherent signals is effectively solved, the target positioning with high resolution is realized, the radar target direction determining method is simple in calculation process, low in requirement on corresponding hardware environment and quite wide in application range.)

1. A method for determining a radar target direction is characterized in that the radar comprises an antenna array, the antenna array comprises a transmitting antenna and three receiving antennas, and the method for determining the radar target direction comprises the following steps:

(S101) receiving an echo signal by a radar;

(S102) carrying out two-dimensional fast Fourier transform processing on the echo signal to obtain a processing result;

(S103) extracting and obtaining a peak data model according to the processing result;

(S104) calculating the direction of arrival based on the peak data model, and determining the target direction.

2. The radar target direction determining method according to claim 1, wherein the three receiving antennas are not equidistant, and a distance between the receiving antenna one and the receiving antenna two is 0.5 λ, and a distance between the receiving antenna two and the receiving antenna three is 2.5 λ, λ being an air wavelength.

3. The radar target direction determining method according to claim 2, wherein the step (S102) is specifically:

and performing two-dimensional fast Fourier transform on the echo signal, and converting the echo signal from time domain signal data into frequency domain signal data.

4. The radar target direction determining method according to claim 3, wherein the peak data model is specifically:

X＝AS，

A＝[a(θ₁)，a(θ₂)]，

S＝[ρ₁，ρ₂]^T，

wherein X is a two-dimensional snapshot data vector; a is a two-dimensional flow pattern matrix of a space array; s is a two-dimensional vector of the space signal; theta is the signal level incidence angle [ ·]^TIs transposed.

5. The radar target direction determining method according to claim 4, wherein the step (S104) is specifically:

the delta is calculated according to the following formula,

(α²-1)cos(14Δ)-(β²-1)cos(4Δ)+(β²-α²)cos(2Δ)＝0

p is calculated according to the following formula,

(α²-1)P²-2[cos(4Δ)-α²cos(2Δ)]P+α²-1＝0

gamma is calculated according to the following formula,

calculate ω from the equation₁And ω₂，

tanω_m＝-tan(mΔ)tanγ

Calculate Θ according to the formula

η₂₁＝(ω₂+2Θ)-(ω₁+Θ)

η₂₁Is the phase difference;

calculating phi from₁，φ₂

Calculating the signal horizontal incident angle according to the following formula

φ₁＝-πsin(θ₁)

φ₂＝-πsin(θ₂)

And determining the target direction according to the signal horizontal incidence angle.

6. A computer-readable storage medium having stored thereon computer software which, when read and executed, implements data interaction with a radar and implements a radar target direction determination method as claimed in any one of claims 1 to 5.

7. A radar target direction determining system, characterized in that it comprises a CPU and a memory, said memory having stored thereon computer software, when said CPU reads and runs said computer software, said system implements data interaction with a radar and implements a radar target direction determining method according to any one of claims 1 to 5.

8. The radar target direction determining system is characterized by being a vehicle-mounted system, and the radar is a vehicle-mounted millimeter wave radar.

Technical Field

The invention relates to the technical field of radar, in particular to the technical field of radar target positioning, and specifically relates to a method and a system for determining a radar target direction and a computer-readable storage medium.

Background

The radar can calculate the relative distance to the target, the relative speed and the direction of the target by transmitting electromagnetic waves and receiving electromagnetic wave signals reflected by an object.

The direction of the target is estimated by measuring and calculating the direction of arrival of the electromagnetic wave reflected by the object. The existing practical direction of arrival estimation techniques are mainly classified into two categories. One is an algorithm for directly processing the covariance matrix of the antenna array reception data, represented by a Linear Prediction (LP) algorithm, a Conventional Beamforming (CBF) algorithm. The other is an algorithm for performing characteristic decomposition on the covariance matrix of the antenna array received data, which is represented by a multiple signal classification (MUSIC) algorithm and a rotation invariant subspace (ESPRIT) algorithm.

When resolving signal sources in multiple directions, multiple receiving antennas must be designed. The angle resolution is proportional to the number of receive antennas, and the number of distinguishable signal sources is proportional to the number of receive antennas. In addition, in the actual environment, the received data of the signal sources in multiple directions generally has signal coherence problems, such as multipath phenomenon in the signal transmission process. Coherent signal sources will result in an incorrect estimation of the direction of arrival. There are two basic categories of processing currently involved in decoherence. One is a dimension reduction processing algorithm represented by spatial smoothing and matrix reconstruction. The other is a non-dimensionality reduction processing algorithm represented by frequency domain smoothing, Toeplite.

In order to meet the miniaturization requirement of the vehicle-mounted radar, the size of the antenna, the position of the receiving antenna and the installation position are limited by the setting environment. Therefore, the problems of low angular resolution, incapability of solving coherent signals and the like generally exist in the prior art.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, and provides the method for determining the direction of the radar target, which has high resolution, can effectively solve the problem of coherent signals, is simple and convenient in implementation mode, has lower requirements on corresponding hardware environments, and is wide in application range.

In order to achieve the above object, the method for determining a radar target direction of the present invention is applied to various radar apparatuses, particularly to millimeter wave radar, and includes an antenna array including a transmitting antenna and three receiving antennas. The method for determining the direction of the radar target comprises the following steps:

(S101) receiving an echo signal by a radar;

(S102) carrying out two-dimensional fast Fourier transform processing on the echo signal to obtain a processing result;

(S103) extracting and obtaining a peak data model according to the processing result;

(S104) calculating the direction of arrival based on the peak data model, and determining the target direction.

In the method for determining the radar target direction, the three receiving antennas are not equidistant, the distance between a first receiving antenna and a second receiving antenna is 0.5 lambda, the distance between the second receiving antenna and a third receiving antenna is 2.5 lambda, and lambda is the air wavelength.

In the method for determining the direction of the radar target, the step (S102) is specifically: and performing two-dimensional fast Fourier transform on the echo signal, and converting the echo signal from time domain signal data into frequency domain signal data.

In the method for determining the radar target direction, the peak data model specifically comprises the following steps:

X＝AS，

A＝[a(θ₁)，a(θ₂)]，

S＝[ρ₁，ρ₂]^T，

wherein X is a two-dimensional snapshot data vector; a is a two-dimensional flow pattern matrix of a space array; s is a two-dimensional vector of the space signal; theta is the signal level incidence angle [ ·]^TIs transposed.

In the method for determining the direction of the radar target, the step (S104) is specifically:

the delta is calculated according to the following formula,

(α²-1)cos(14Δ)-(β²-1)cos(4Δ)+(β²-α²)cos(2Δ)＝0

p is calculated according to the following formula,

(α²-1)P²-2[cos(4Δ)-α²cos(2Δ)]P+α²-1＝0

gamma is calculated according to the following formula,

calculate ω from the equation₁And ω₂，

tanω_m＝-tan(mΔ)tanγ

Calculate Θ according to the formula

η₂₁＝(ω₂+2Θ)-(ω₁+Θ)

η₂₁Is the phase difference;

calculating phi from₁，φ₂

Calculating the signal horizontal incident angle according to the following formula

φ₁＝-πsin(θ₁)

φ₂＝-πsin(θ₂)

And determining the target direction according to the signal horizontal incidence angle.

The invention also provides a computer readable storage medium, which stores computer software, realizes data interaction with radar when the computer software is read and operated, and realizes the method for determining the target direction of the radar.

The invention also provides a system for determining the target direction of the radar, which is a vehicle-mounted system, wherein the radar is a vehicle-mounted millimeter wave radar. The system comprises a CPU and a memory, wherein computer software is stored in the memory, and when the CPU reads and runs the computer software, the system realizes data interaction with the radar and realizes the method for determining the target direction of the radar.

The method comprises the steps of calculating and obtaining the amplitude and the phase of the superposed reflected signals of two targets by utilizing the received echo signals, calculating the amplitude and the phase of the reflected signals of the two targets before superposition by utilizing a mathematical model, accurately estimating the directions of arrival of the two targets and determining the direction of the target. Therefore, the problem of coherent signals is effectively solved, the target positioning with high resolution is realized, the radar target direction determining method is simple in calculation process, low in requirement on corresponding hardware environment and quite wide in application range.

Drawings

Fig. 1 is a schematic flow chart of a radar target direction determining method according to the present invention.

Fig. 2 is a schematic diagram of a layout of radar antennas in the radar target direction determining system of the present invention.

Detailed Description

In order to clearly understand the technical contents of the present invention, the following examples are given in detail.

Fig. 1 is a schematic flow chart of a method for determining a direction of a radar target according to the present invention.

In one embodiment, the radar includes an antenna array including a transmitting antenna and three receiving antennas. As shown in fig. 2, the three receiving antennas are not equidistant, the distance between the first receiving antenna and the second receiving antenna is 0.5 λ, the distance between the second receiving antenna and the third receiving antenna is 2.5 λ, and λ is the air wavelength. The radar target direction determining method comprises the following steps:

(S101) receiving an echo signal by a radar;

(S102) carrying out two-dimensional fast Fourier transform processing on the echo signal to obtain a processing result;

(S103) extracting and obtaining a peak data model according to the processing result;

(S104) calculating the direction of arrival based on the peak data model, and determining the target direction.

In a preferred embodiment, the step (S102) is specifically:

and performing two-dimensional fast Fourier transform on the echo signal, and converting the echo signal from time domain signal data into frequency domain signal data.

The peak data model specifically comprises:

X＝AS，

A＝[a(θ₁)，a(θ₂)]，

S＝[ρ₁，ρ₂]^T，

wherein X is a two-dimensional snapshot data vector; a is a two-dimensional flow pattern matrix of a space array; s is a two-dimensional vector of the space signal; theta is the signal level incidence angle [ ·]^TIs transposed.

The step (S104) is specifically:

the delta is calculated according to the following formula,

(α²-1)cos(14Δ)-(β²-1)cos(4Δ)+(β²-α²)cos(2Δ)＝0

p is calculated according to the following formula,

(α²-1)P²-2[cos(4Δ)-α²cos(2Δ)]P+α²-1＝0

gamma is calculated according to the following formula,

calculate ω from the equation₁And ω₂，

tanω_m＝-tan(mΔ)tanγ

Calculate Θ according to the formula

η₂₁＝(ω₂+2Θ)-(ω₁+Θ)

η₂₁Is the phase difference;

calculating phi from₁，φ₂

Calculating the signal horizontal incident angle according to the following formula

φ₁＝-πsin(θ₁)

φ₂＝-πsin(θ₂)

And determining the target direction according to the signal horizontal incidence angle.

Correspondingly, the invention also provides a computer readable storage medium, which stores computer software, when the computer software is read and operated, the data interaction with the radar is realized, and the method for determining the target direction of the radar is realized.

In addition, the invention also provides a radar target direction determining system which can be a vehicle-mounted system, wherein the radar is a vehicle-mounted millimeter wave radar. The radar target direction determining system comprises a CPU and a memory, wherein computer software is stored in the memory, and when the CPU reads and runs the computer software, the system realizes data interaction with a radar and realizes the radar target direction determining method.

The invention obtains the amplitude and the phase position of the superposed reflected signals from two targets in each channel by using the signal data of the receiving antenna. And then, by utilizing the known information and through a mathematical model of the received signals, a brand new mathematical model is deduced, and the amplitude and the phase of the reflected signals of the two targets before superposition are respectively calculated, so that the arrival directions of the two targets are accurately estimated.

In practical applications, taking the millimeter wave radar with one transmitting antenna and three receiving antennas shown in fig. 2 as an example, the millimeter wave radar transmits electromagnetic waves by using one transmitting antenna and receives electromagnetic waves reflected by surrounding targets by using three antennas, that is, the radar apparatus receives the echo signal S101.

The two-dimensional FFT processing step S102 is a fast fourier transform processing of performing two-dimensional (distance dimension and velocity dimension) on the received signal. And converting the received echo signal data from a time domain into a frequency domain, thereby estimating the relative distance and the relative speed of the target and the radar.

In the two-dimensional FFT peak value extraction step S103, a peak value search is performed based on the two-dimensional FFT result. The peak represents a target candidate, i.e., there may be a target at the location of the peak in the distance dimension and velocity dimension. The extracted peak standard data model (antenna array) is defined as shown in formulas (1) to (5),

whereinIs an L x1 dimensional snapshot data vector of the array. L is the number of receive antennas.Is an L multiplied by K dimension flow pattern matrix (guiding vector matrix) of a space array. K is the number of targets at the same distance and speed relative to the radar, i.e. the required radarThe number of targets that the direction estimation algorithm distinguishes. And theta is the signal horizontal incidence angle. λ is the air wavelength. d is the antenna spacing, and formula (3) is an equal spacing uniform linear array model.Is a K x1 dimensional vector (complex amplitude) of the spatial signal.Is the L x1 dimensional noise vector of the spatial signal at time t. [. the]^TIs transposed.

On the basis of the peak standard data model, the resolving power of two targets is taken as an example.

As shown in fig. 2, the receiving antennas are not equally spaced. The distance between Rx1 (first receive antenna) and Rx2 (second receive antenna) is 0.5 λ, and the distance between Rx2 and Rx3 (third receive antenna) is 2.5 λ. The antenna spacing setting of 0.5 λ is to solve the angle ambiguity problem. However, the antenna spacing of 0.5 λ is too close, and the angle estimation error is large in practical situations, so that a set of 2.5 λ antennas is additionally designed.

The present example estimates only the horizontal incident angle, assuming that the vertical angle and the roll angle are 0. Based on the application scene of the vehicle-mounted millimeter wave radar, radar data only calculates a single-frame result, and multi-frame accumulation processing is not performed.

The standard model equations (1) to (5) are converted into the following forms according to the above settings,

X＝AS (6)

A＝[a(θ₁)，a(θ₂)] (7)

S＝[ρ₁，ρ₂]^T (9)

N＝[n₁，n₂，n₃]^T (10)

the effect of the noise N is ignored.

Bringing the formulae (7), (8) and (9) into the formula (6) to obtain the formula (11)

Set phi for simplicity of calculation₁＝-πsin(θ₁)，φ₂＝-πsin(θ₂). For in formula 11Converting the complex index into a trigonometric function by using an Euler formula, and finishing to obtain a formula (12)

Wherein Continuously decomposing the formula (12) by using a sine and cosine dihedral sum formula, and obtaining the formula (13) after arrangement

WhereinContinuously decomposing the formula (13) by using a sine and cosine dihedral sum and difference formula, and finishing to obtain a formula (14)

In the same way, the other two items in the result matrix of the formula (11) can be deduced, and the result matrix is arranged to obtain the formula (15)

The expression (16) holds

[cos(γ)cos(mΔ)-i sin(γ)sin(mΔ)]＝M_me^jω (16)

tanω_m＝-tan(mΔ)tanγ (17)

Then equation (15) can be converted to equation (18)

Is provided with And using the above assumptions as an equation set, developing and then proposing a gamma term to obtain the formula (19) and the formula (20)

Combining formula (19) with formula (20), and eliminating the gamma term to obtain formula (21)

(α²-1)cos(14Δ)-(β²-1)cos(4Δ)+(β²-α²)cos(2Δ)＝0 (21)

Here, only Δ in equation (21) is an unknown number, and therefore an approximate solution of Δ can be obtained by solving the equation. Then, the ratio of the amplitudes of the received signals is further calculated using the calculated ΔIt is known thatCos (2 gamma) can be arranged by using sine and cosine transform formula and sine double angle formula to obtain formula (22)

Combining formula (22) with formula (19) to give formula (23)

(α²-1)P²-2[cos(4Δ)-α²cos(2Δ)]P+α²-1＝0 (23)

Here, only P in equation (23) is an unknown number, and thus a solution to P can be obtained by solving the equation. At this time, γ can be calculated by equation (22) using the value of P, and ω can be further calculated by equation (17)₁，ω₂The value of (c). The phase difference η can then be determined by knowing the number of phase differences η₂₁Equation (24) of (a) solves for the value of Θ.

η₂₁＝(ω₂+2Θ)-(ω₁+Θ) (24)

Finally, using the calculated Δ, Θ, φ can be derived₁，φ₂To thereby obtain a final result theta₁，θ₂。

Compared with the prior art, the method for determining the radar target direction has the following advantages:

1. the angular resolution is high. The test result of the angle resolution capability is within 1 degree. The test is divided into two parts of simulation test and actual measurement of a prototype. In the simulation test, the normal direction of the radar is set to be 0 degree, any two targets with the angle difference of 1 degree are selected within the range from-75 degrees to 75 degrees for testing, and the final test result achieves the resolution within 1 degree. In the actual measurement test of a prototype, two targets (corner reflectors) are arranged right in front of a radar, the distance between the two static targets is the same, the angles are gradually separated until the radar can be distinguished, and the final test result reaches the resolution capability within 1 degree.

2. The problem of coherent signals is effectively solved. Under the influence of the coherent signals, the azimuth angle of the target can still be calculated.

3. The antenna layout is at unequal pitches. The method of the invention is proved to have no special limitation on the distance between the antennas, and the antennas can be equally spaced or unequally spaced, so the method can be widely applied to various radar devices and meet the requirement of radar miniaturization.

4. The calculation process is simple, and the requirement on hardware resources is low. The prototype actually used an AWR1642 chip (CPU: ARM-Cortex R4F 200MHz, DSP: C674x DSP 600MHz, on-chip memory: 1.5MB) with lower cost. Because the calculation flow of the invention is mostly equation operation, no circular calculation processing with large calculation amount exists. Therefore, the operation of the computing process can be completely realized by using limited computing resources and storage resources.

The method comprises the steps of calculating and obtaining the amplitude and the phase of the superposed reflected signals of two targets by utilizing the received echo signals, calculating the amplitude and the phase of the reflected signals of the two targets before superposition by utilizing a mathematical model, accurately estimating the directions of arrival of the two targets and determining the direction of the target. Therefore, the problem of coherent signals is effectively solved, the target positioning with high resolution is realized, the radar target direction determining method is simple in calculation process, low in requirement on corresponding hardware environment and quite wide in application range.

In this specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.