阅读说明：本技术 基于多径判断的阵列雷达复杂地形低仰角估计方法 (Array radar complex terrain low elevation angle estimation method based on multipath judgment ) 是由 赵永波 陈�胜 牛奔 苏洪涛 于 2020-06-18 设计创作，主要内容包括：本发明公开了一种基于多径判断的阵列雷达复杂地形低仰角估计方法,包括：根据阵列雷达系统参数建立目标多径信号模型；根据所述目标多径信号模型计算第一多径特征值,以得到鉴反射系数幅度曲线；获取雷达系统采集的目标回波数据,并根据所述目标回波数据计算第二多径特征值；根据所述鉴反射系数幅度曲线和所述第二多径特征值得到反射系数幅度估计值；采用波束扫描算法对所述目标回波数据进行扫描,得到波束扫描曲线的3dB波束宽度；根据所述反射系数幅度估计值与所述波束扫描曲线的3dB波束宽度进行多径判断,得到最终的目标仰角估计值。本发明提供的阵列雷达复杂地形低仰角估计方法,减弱了复杂反射面对测角的影响,提高了测角精度与稳健性。(The invention discloses a low elevation angle estimation method for an array radar complex terrain based on multipath judgment, which comprises the following steps: establishing a target multipath signal model according to the array radar system parameters; calculating a first multipath characteristic value according to the target multipath signal model to obtain an amplitude curve of the reflection coefficient; acquiring target echo data acquired by a radar system, and calculating a second multipath characteristic value according to the target echo data; obtaining a reflection coefficient amplitude estimation value according to the reflection coefficient amplitude curve and the second multipath characteristic value; scanning the target echo data by adopting a beam scanning algorithm to obtain the 3dB beam width of a beam scanning curve; and performing multipath judgment according to the reflection coefficient amplitude estimation value and the 3dB beam width of the beam scanning curve to obtain a final target elevation angle estimation value. The array radar complex terrain low elevation angle estimation method provided by the invention weakens the influence of a complex reflecting surface on angle measurement, and improves the angle measurement precision and robustness.)

1. A low elevation angle estimation method for an array radar complex terrain based on multipath judgment is characterized by comprising the following steps:

establishing a target multipath signal model according to the array radar system parameters;

calculating a first multipath characteristic value according to the target multipath signal model to obtain an amplitude curve of the reflection coefficient;

acquiring target echo data acquired by a radar system, and calculating a second multipath characteristic value according to the target echo data;

obtaining a reflection coefficient amplitude estimation value according to the reflection coefficient amplitude curve and the second multipath characteristic value;

scanning the target echo data by adopting a beam scanning algorithm to obtain the 3dB beam width of a beam scanning curve;

and performing multipath judgment according to the reflection coefficient amplitude estimation value and the 3dB beam width of the beam scanning curve to obtain a final target elevation angle estimation value.

2. The array radar complex terrain low elevation angle estimation method of claim 1, wherein the target multipath signal model is:

y＝ws；

wherein y represents the echo signal received by the array element, and y belongs to C^M×1C represents a complex number set, M represents the number of antenna elements, w represents a composite steering vector, and the expression is: w ═ a (θ)_r)+ρe^-jψa(-arcsin(sin(θ_r)+2h_r/R_d) Wherein, a (theta)_r) A guide vector, theta, representing the direct wave signal_rRepresenting the true value of the target elevation angle, p representing the reflection coefficient, psi representing the phase difference between the direct wave signal and the multipath signal at the array reference point, and psi-2 pi Δ R/λ, Δ R representing the distance between the direct distance and the multipath distanceDispersion, λ represents the radar operating wavelength; a (-arcsin (sin (theta))_r)+2h_r/R_d) A steering vector h representing a multipath signal_rTrue value, R, representing antenna frame height_dRepresenting the distance of the target from the radar antenna and s representing the complex envelope of the direct wave signal of the target.

3. The array radar complex terrain low elevation angle estimation method of claim 1, wherein calculating a first multipath feature value according to the target multipath signal model to obtain an identification reflection coefficient amplitude curve comprises:

calculating the mean value of M array element data of the multipath signals according to the target multipath signal model;

calculating the echo amplitude without the zero frequency component according to the average value of the M array element data of the multipath signal;

performing FFT processing on the echo amplitude without the zero frequency component to obtain a first multipath characteristic value;

and taking the change curve of the first multipath characteristic value along with the reflection coefficient amplitude as the reflection coefficient amplitude identification curve.

4. The array radar complex terrain low elevation angle estimation method of claim 3, wherein the expression of the first multipath eigenvalue is:

F_y＝max(F(m))；

wherein, F_yDenotes a first multipath characteristic value, max (-) denotes a maximum operation, F (m) denotes a spectrum of the amplitude of the echo from which the zero frequency component is removed, and is expressed byM represents the number of frequency spectrum points, Y represents the amplitude of an echo with zero frequency components removed, and M represents the number of antenna elements.

5. The array radar complex terrain low elevation angle estimation method of claim 1, wherein the expression of the target echo data is:

x＝ws+n；

wherein x represents the target echo data and x ∈ C^M×1C represents a complex set, M represents the number of antenna elements, w represents a composite steering vector, s represents the complex envelope of the target direct wave signal, n represents zero-mean round Gaussian white noise, and n belongs to C^M×1。

6. The array radar complex terrain low elevation angle estimation method of claim 1, wherein obtaining a reflection coefficient amplitude estimation value according to the reflection coefficient amplitude curve and the second multipath characteristic value comprises:

and finding out the value closest to the second multipath characteristic value in the reflection coefficient amplitude curve, and taking the corresponding reflection coefficient amplitude as the reflection coefficient amplitude estimation value.

7. The array radar complex terrain low elevation angle estimation method of claim 1, wherein multipath judgment is performed according to the reflection coefficient amplitude estimation value and the 3dB beam width of the beam scanning curve to obtain a final target elevation angle estimation value, and the method comprises the following steps:

if the reflection coefficient amplitude estimation value is judged to be larger than a first preset value or the BD is larger than or equal to T, estimating a target elevation angle according to an alternate projection two-dimensional search algorithm to obtain a first target elevation angle estimation value, and outputting the first target elevation angle estimation value as a final target elevation angle estimation value;

otherwise, estimating the target elevation according to a beam scanning algorithm to obtain a second target elevation estimation value, and outputting the second target elevation estimation value as a final target elevation estimation value;

where BD represents the 3dB beamwidth of the beamsweeping curve and T represents the 3dB width threshold of the beamsweeping curve.

8. The array radar complex terrain low elevation angle estimation method of claim 7, further comprising, before estimating a target elevation angle according to an alternate projection two-dimensional search algorithm to obtain a first target elevation angle estimate:

if the reflection coefficient amplitude estimation value is judged to be less than or equal to a second preset value and BD is more than or equal to T, the reflection coefficient amplitude estimation value is made to be 0.9; otherwise, keeping the reflection coefficient amplitude estimation value unchanged.

9. The array radar complex terrain low elevation angle estimation method of claim 7, wherein estimating a target elevation angle according to an alternate projection two-dimensional search algorithm to obtain a first target elevation angle estimation value comprises:

setting an initial estimation value of the antenna elevation;

taking the initial estimation value of the antenna frame height as a true value of the antenna frame height, performing one-dimensional search on a target elevation angle, and calculating the initial estimation value of the target elevation angle;

taking the initial estimation value of the target elevation angle as a true value of the target elevation angle, and performing one-dimensional search on the antenna frame height to obtain an estimation value of the antenna frame height;

and repeating the one-dimensional search of the target elevation angle and the antenna frame height until the iteration result is converged to obtain a first target elevation angle estimation value.

10. The array radar complex terrain low elevation estimation method of claim 7, wherein the calculation formula of the second target elevation estimation value is as follows:

wherein the content of the first and second substances,representing a second target elevation estimate value,

Technical Field

The invention belongs to the technical field of radars, and particularly relates to a low elevation angle estimation method for an array radar complex terrain based on multipath judgment.

Background

The radar mainly aims to effectively detect a target and simultaneously realize angle measurement and tracking of the target. When the array radar positions a low elevation angle target, radar beams strike the ground, and direct waves of the target and multipath reflected waves reflected by the ground are superposed in an antenna beam main lobe. The direct wave signals and the multipath signals are coherent, the two paths of coherent signals are received by the radar antenna at the same time, the existence of the multipath signals can cause lobe splitting and upwarping of a radar vertical plane, the detection of the signals is influenced, the estimation of the radar to a target elevation angle is also seriously influenced, and especially when a reflecting surface is complex, the influence of multipath reflected signals is more complex.

Currently, for the estimation of an elevation angle including a multipath signal, the prior art mainly provides the following methods: in the prior art, an array radar low elevation angle estimation method is disclosed, which is an angle measurement method for measuring a real position of a target by using a synthetic steering vector. The synthetic guide vector method is to utilize prior information of reflection coefficient, replace conventional guide vector in free space with composite guide vector under multipath condition, and then estimate elevation direction by maximum likelihood method. However, this method requires that the reflecting surface must be flat, when the reflecting surface is complex, part of the target echoes do not contain multipath signals, the signal model does not match with the actual situation, and the angle measurement accuracy is seriously reduced.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a low elevation angle estimation method for the array radar complex terrain based on multipath judgment. The technical problem to be solved by the invention is realized by the following technical scheme:

a low elevation angle estimation method for an array radar complex terrain based on multipath judgment comprises the following steps:

establishing a target multipath signal model according to the array radar system parameters;

calculating a first multipath characteristic value according to the target multipath signal model to obtain an amplitude curve of the reflection coefficient;

acquiring target echo data acquired by a radar system, and calculating a second multipath characteristic value according to the target echo data;

obtaining a reflection coefficient amplitude estimation value according to the reflection coefficient amplitude curve and the second multipath characteristic value;

scanning the target echo data by adopting a beam scanning algorithm to obtain the 3dB beam width of a beam scanning curve;

and performing multipath judgment according to the reflection coefficient amplitude estimation value and the 3dB beam width of the beam scanning curve to obtain a final target elevation angle estimation value.

In one embodiment of the present invention, the target multipath signal model is:

y＝ws；

wherein y represents the echo signal received by the array element, and y belongs to C^M×1C represents a complex number set, M represents the number of antenna elements, w represents a composite steering vector, and the expression is: w ═ a (θ)_r)+ρe^-jψa(-arcsin(sin(θ_r)+2h_r/R_d) Wherein, a (theta)_r) A guide vector, theta, representing the direct wave signal_rRepresenting the true value of the target elevation angle, rho representing a reflection coefficient, psi representing the phase difference between the direct wave signal and the multipath signal at the array reference point, and psi being 2 pi delta R/lambda, wherein delta R represents the distance difference between the direct distance and the multipath distance, and lambda represents the radar working wavelength; a (-arcsin (sin (theta))_r)+2h_r/R_d) A steering vector h representing a multipath signal_rTrue value, R, representing antenna frame height_dRepresenting the distance of the target from the radar antenna and s representing the complex envelope of the direct wave signal of the target.

In one embodiment of the present invention, calculating a first multipath characteristic value according to the target multipath signal model to obtain an amplitude curve of the identified reflection coefficient comprises:

calculating the mean value of M array element data of the multipath signals according to the target multipath signal model;

calculating the echo amplitude without the zero frequency component according to the average value of the M array element data of the multipath signal;

performing FFT processing on the echo amplitude without the zero frequency component to obtain a first multipath characteristic value;

and taking the change curve of the first multipath characteristic value along with the reflection coefficient amplitude as the reflection coefficient amplitude identification curve.

In an embodiment of the present invention, the expression of the first multipath characteristic value is:

F_y＝max(F(m))；

wherein, F_yRepresenting a first multipath characteristic value, max (·) representing a max operation, and F (m) representing removal of zero-frequency componentsThe frequency spectrum of the echo amplitude is expressed as

M represents the number of frequency spectrum points, Y represents the amplitude of an echo with zero frequency components removed, and M represents the number of antenna elements.

In an embodiment of the present invention, the expression of the target echo data is:

x＝ws+n；

wherein x represents the target echo data and x ∈ C^M×1C represents a complex set, M represents the number of antenna elements, w represents a composite steering vector, s represents the complex envelope of the target direct wave signal, n represents zero-mean round Gaussian white noise, and n belongs to C^M×1。

In one embodiment of the present invention, obtaining the reflection coefficient amplitude estimation value according to the reflection coefficient amplitude curve and the second multipath characteristic value comprises:

and finding out the value closest to the second multipath characteristic value in the reflection coefficient amplitude curve, and taking the corresponding reflection coefficient amplitude as the reflection coefficient amplitude estimation value.

In an embodiment of the present invention, obtaining a final target elevation angle estimated value according to the reflection coefficient amplitude estimated value and the 3dB beamwidth of the beamsweeping curve includes:

if the reflection coefficient amplitude estimation value is judged to be larger than a first preset value or the BD is larger than or equal to T, estimating a target elevation angle according to an alternate projection two-dimensional search algorithm to obtain a first target elevation angle estimation value, and outputting the first target elevation angle estimation value as a final target elevation angle estimation value;

otherwise, estimating the target elevation according to a beam scanning algorithm to obtain a second target elevation estimation value, and outputting the second target elevation estimation value as a final target elevation estimation value;

where BD represents the 3dB beamwidth of the beamsweeping curve and T represents the 3dB width threshold of the beamsweeping curve.

In an embodiment of the present invention, before estimating the target elevation according to the alternating projection two-dimensional search algorithm to obtain the first target elevation estimation value, the method further includes:

if the reflection coefficient amplitude estimation value is judged to be less than or equal to a second preset value and BD is more than or equal to T, the reflection coefficient amplitude estimation value is made to be 0.9; otherwise, keeping the reflection coefficient amplitude estimation value unchanged.

In one embodiment of the present invention, estimating a target elevation according to an alternative projection two-dimensional search algorithm to obtain a first target elevation estimate, includes:

setting an initial estimation value of the antenna elevation;

taking the initial estimation value of the antenna frame height as a true value of the antenna frame height, performing one-dimensional search on a target elevation angle, and calculating the initial estimation value of the target elevation angle;

taking the initial estimation value of the target elevation angle as a true value of the target elevation angle, and performing one-dimensional search on the antenna frame height to obtain an estimation value of the antenna frame height;

and repeating the one-dimensional search of the target elevation angle and the antenna frame height until the iteration result is converged to obtain a first target elevation angle estimation value.

In one embodiment of the present invention, the calculation formula of the second target elevation angle estimation value is:

wherein the content of the first and second substances,

representing a second target elevation estimate value,

represents the time when T (-) is maximized_rA value of (d); theta_rActual value, T (theta), representing the elevation of the target_r) Representing the beam scanning cost function value.

The invention has the beneficial effects that:

1. the array radar complex terrain low elevation angle estimation method based on multipath judgment estimates the amplitude of the reflection coefficient by utilizing the characteristic value of the multipath signal, and judges the target characteristic according to the estimation value of the amplitude of the reflection coefficient and the 3dB width of the beam scanning curve so as to select a more appropriate angle measurement algorithm, thereby obtaining the final estimation value of the target elevation angle, weakening the influence of the complex reflection surface on angle measurement, and improving the accuracy and the robustness of the angle measurement;

2. according to the array radar complex terrain low elevation angle estimation method, when the target echo data comprise multipath signals, an alternate projection two-dimensional search algorithm is adopted, so that the operation amount of the two-dimensional search algorithm is reduced; meanwhile, the two-dimensional search algorithm can obtain the estimated value of the target elevation angle without the information of the antenna height and the topographic information, and the angle measurement robustness is further improved.

The present invention will be described in further detail with reference to the accompanying drawings and examples.

Drawings

Fig. 1 is a schematic flowchart of a method for estimating a low elevation angle of an array radar complex terrain based on multipath judgment according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a multipath reflection model provided by an embodiment of the present invention;

fig. 3 is a schematic flow chart of another method for estimating a low elevation angle of an array radar complex terrain based on multipath judgment according to an embodiment of the present invention;

FIG. 4 is a comparison graph of the variation curve of the root mean square error of the angle measurement with the target elevation of the prior two-dimensional search algorithm and the beam scanning algorithm provided by the embodiment of the invention and the method of the invention;

fig. 5 is a comparison graph of the variation curve of the root mean square error of the angle measurement with the signal-to-noise ratio of the direct wave detection in the conventional two-dimensional search algorithm and beam scanning algorithm provided in the embodiment of the present invention and the method of the present invention.

Detailed Description

The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto.