WO2022233169A1 - 非规则轨迹水中运动目标前向声散射多普勒频移计算方法 - Google Patents

非规则轨迹水中运动目标前向声散射多普勒频移计算方法 Download PDF

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WO2022233169A1
WO2022233169A1 PCT/CN2022/076459 CN2022076459W WO2022233169A1 WO 2022233169 A1 WO2022233169 A1 WO 2022233169A1 CN 2022076459 W CN2022076459 W CN 2022076459W WO 2022233169 A1 WO2022233169 A1 WO 2022233169A1
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target
trajectory
frequency shift
doppler frequency
calculating
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PCT/CN2022/076459
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French (fr)
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何传林
于洋
孙守扬
马健博
吕红敏
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山东省科学院海洋仪器仪表研究所
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/539—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section

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  • the invention relates to the technical field of marine acoustics, in particular to a method for calculating forward acoustic scattering Doppler frequency shifts of moving targets in water.
  • the Doppler shift of the direct wave is zero and the target has a time-varying Doppler shift.
  • the forward scattering Doppler frequency shift information of the target is extracted from the received acoustic signal, and the moving target in water that invades the transceiver line can be detected.
  • the authenticity and accuracy of the extraction results of the forward scattering Doppler frequency shift of the target need to be compared and tested by the corresponding theoretical calculation results.
  • the first method mainly uses the two parameters of the bistatic separation angle, the target heading and the included angle of the bistatic separation angle bisector, and its expression is:
  • v is the speed of the target
  • ⁇ is the wavelength of the sound source signal
  • ⁇ is the bistatic separation angle
  • ⁇ is the angle between the target heading and the bistatic separation angle bisector.
  • the calculation principle of the second method is the same as that of the first method, but the geometric description is replaced by an algebraic description, and the forward acoustic scattering Doppler frequency shift of the target is directly established.
  • the expression of the parameters such as the position of the crossing point, the heading angle, etc., namely:
  • t is the movement time of the target
  • t c is the time when the target crosses the transceiver line
  • d is the length of the transceiver line
  • d TR is the horizontal distance from the target crossing point to the receiving end
  • ⁇ is the angle between the target track and the baseline.
  • the purpose of the present invention is to solve the above-mentioned defects existing in the prior art, and to provide a method for calculating the forward acoustic scattering Doppler frequency shift of targets in water with irregular trajectories,
  • the technical scheme adopted by the present invention to solve the technical problem is: a method for calculating forward acoustic scattering Doppler frequency shift of a moving target in water with irregular trajectories, including: (1) transforming the earth's latitude and longitude coordinates of the transmitting end, the target trajectory and the receiving end into right angles The coordinates are marked as (x S , y S ), (x T , y T ) and (x R , y R ) in turn;
  • the smoothing method is as follows: using a time window with a length of l w points and intercepting the target trajectory coordinate sequence with a step size t w points in turn, and taking the arithmetic mean of the trajectory coordinates in each window as the time period.
  • the equivalent trajectory coordinates of the target, the smoothed target trajectory coordinates are:
  • the calculation method of the horizontal distance from the target and the receiving end to the intersection of its virtual straight line trajectory and the baseline is:
  • the target At any time t i , the target reaches the intersection of its virtual straight line trajectory and the baseline The horizontal distance is:
  • the horizontal distance from the intersection of the target virtual straight line trajectory and the baseline to the receiving end is:
  • the horizontal distance from the current position of the target to the receiver is:
  • the calculation method of the angle between the virtual linear trajectory and the baseline is: applying the cosine theorem to obtain the angle between the target virtual linear trajectory and the baseline at time t i :
  • the calculation method of the forward acoustic scattering Doppler frequency shift of the target includes:
  • d TC (t i ), d TR (t i ), ⁇ (t i ), the signal center frequency f c , and the ambient sound speed c are substituted into the forward sound scattering Doppler frequency shift parameter formula of the linear trajectory:
  • the existing technology cannot calculate the forward acoustic scattering Doppler frequency shift when the target trajectory is irregular; when smoothing the target trajectory, it adopts azimuth sampling at equal time intervals and performs arithmetic mean calculation, and the process is rigorous; When estimating the angle between the virtual straight track of the target and the baseline, the cosine law is used, and the horizontal distance between the target, the intersection of the trajectory and the receiving end is calculated by using the geometric relationship, which has a strict theoretical basis; when calculating the forward acoustic scattering Doppler The frequency shift is based on strict parametric equations, and the results are accurate.
  • 1 is a flowchart of a method for calculating forward acoustic scattering Doppler frequency shifts of moving targets in water with irregular tracks provided by an embodiment of the present invention
  • Fig. 2 is a schematic diagram of piecewise linear approximation of target trajectory
  • Figure 5 is the target trajectory comparison curve before and after smoothing, wherein (a) is before smoothing; (b) is after smoothing;
  • Fig. 6 is an intersection point distribution diagram of the target virtual straight line trajectory and the baseline
  • Figure 7 is the horizontal distance from the target to the intersection of its virtual straight line trajectory and the baseline
  • Figure 8 is the horizontal distance from the virtual crossing point of the baseline to the receiving end
  • Fig. 10 The estimation result of the Doppler frequency shift of the forward acoustic scattering of the target
  • Embodiment 1 The method for calculating the forward acoustic scattering Doppler frequency shift of a moving target in water with an irregular trajectory provided by the present invention, the main process is shown in Figure 1, and specifically includes the following steps:
  • the average velocity is taken as the target moving velocity when calculating the target forward acoustic scattering Doppler frequency shift.
  • the target trajectory can be realized.
  • the smoothing of the original trajectory can reduce the influence of the violent swing of the target trajectory in the local period on the calculation results.
  • the smoothed target trajectory coordinates are:
  • the straight line equation where the baseline is located can be obtained from the position coordinates of the transmitter and receiver:
  • the target At any time t i , the target reaches the intersection of its virtual straight line trajectory and the baseline The horizontal distance is:
  • the horizontal distance from the intersection of the target virtual straight line trajectory and the baseline to the receiving end is:
  • the horizontal distance from the current position of the target to the receiver is:
  • the processed parameters will be recorded on the real trajectory of the target: d TC (t i ), d TR (t i ), ⁇ (t i ), together with the signal center frequency f c and the ambient sound speed c, are substituted into the forward sound scattering Doppler shift parameter formula of the linear trajectory:
  • Embodiment 2 The algorithm of the present invention is verified by using the target track data and the extraction results of the target forward acoustic scattering Doppler frequency shift of the Qiandao Lake scaled target forward acoustic scattering detection test in 2011.
  • the transmitter and receiver are separated, and the distance is about 1100 meters.
  • the target is a double-layer aluminum plate assembly with foam interlayer (without automatic power), which is towed by a tugboat through a flexible rope with a length of 10 meters to cross the transceiver connection.
  • the positions of the transmitter, receiver and target track are shown in Figure 3.
  • the center frequency of the sound source emission signal f c 10 kHz
  • the sound speed of the test water layer is approximately constant
  • the sound speed value is c ⁇ 1485 m/s.
  • the tugboat's motion trajectory is not straight and there are significant deflections and swaying.
  • a portable GPS device was used to record the true trajectory position information of the tugboat, and the sampling interval was 1 second.
  • a rectangular window with a time length of 5 seconds is used to slide and intercept the sequence of tugboat position points with a step of 3 seconds, and the arithmetic mean of the five position points intercepted each time is used as the position of the target at this moment, so as to realize the original tugboat position.
  • Figures 5(a) and 5(b) show the tugboat trajectory before and after smoothing, respectively. It can be seen that the smoothing process can reduce the violent oscillation in the local period. As mentioned above, since the tugboat and the target are connected by a flexible rope, the smoothed trajectory can be regarded as the true trajectory of the target.
  • Figure 6 shows the distribution of the intersection points (*) of the target virtual straight line trajectory and the baseline calculated using the target trajectory information of Figure 5(b) through equations (7) and (8).
  • the results show that since the target trajectory is not in the form of a straight line, the intersection position of the virtual trajectory and the baseline at each moment after piecewise linear approximation is different from the real crossing position of the target, but most of them are gathered in the area near the real position.
  • Figure 7 shows the calculation result of the horizontal distance from the target to the intersection of its virtual straight line trajectory and the baseline in the whole voyage obtained by equation (9). Obviously, the greater the position deviation between the virtual crossing point and the actual crossing point of the target in the baseline, the greater the value of d TC . But the overall trajectory evolution trend is clear, especially when the target is near the baseline, the distance fluctuation is small.
  • Figure 9 shows the angle information between the target virtual straight line trajectory and the baseline calculated by formula (12).
  • the Doppler shift of the direct wave is zero.
  • the forward sound scattered wave usually interferes with the direct wave, the final effect is to make the received sound field low-frequency modulation.
  • Extracting the envelope of the received signal and performing time-frequency analysis on the envelope the Doppler frequency-shifted fringes shown in Fig. 11 are obtained.
  • the target scattered wave passing through the transceiver line corresponds to the "V"-shaped Doppler frequency shift fringes in the figure
  • the direct wave corresponds to the horizontal fringes with approximately zero Doppler frequency shift.
  • the Doppler frequency shift curve obtained by this method is shown in the dot-dash line in Figure 11.
  • the Doppler frequency shift range and variation trend represented by this curve are consistent with the Doppler frequency shift fringes obtained by data analysis. The results confirm that the feasibility of the method of the present invention.

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  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
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Abstract

一种非规则轨迹水中运动目标前向声散射多普勒频移计算方法，包括：(1)将发射端、目标轨迹和接收端的地球经纬度坐标转换为直角坐标，并依次标记为(x S,y S)、(x T,y T)和(x R,y R)；(2)将目标轨迹坐标序列记为(x T(t i),y T(t i)),i＝1,2,...,N，计算所有时段内的平均航速（I）；(3)对目标轨迹进行平滑处理，获得虚拟直线轨迹，分别计算目标和接收端到其虚拟直线轨迹与基线交点的水平距离、虚拟直线轨迹与基线的夹角；(4)利用步骤(2)和(3)计算得到的参数，计算各时刻目标的前向声散射多普勒频移。

Description

非规则轨迹水中运动目标前向声散射多普勒频移计算方法 技术领域
本发明涉及海洋声学技术领域，尤其涉及水中运动目标前向声散射多普勒频移计算方法。
背景技术
在前向声散射探测***中，由于发射端和接收端的位置均固定而只有目标运动，直达波的多普勒频移为零而目标具有时变的多普勒频移。从接收声信号中提取目标的前向散射多普勒频移信息，可以探测到入侵收发连线的水中运动目标。然而，目标前向散射多普勒频移提取结果的真实性和准确性，需要通过相应的理论计算结果作对比检验。
水中目标的前向声散射多普勒频移的理论计算方法有两种：
第一种方法主要利用双基地分置角、目标航向与双基地分置角平分线的夹角这两个参数，其表达式为：
Figure PCTCN2022076459-appb-000001
其中v为目标运动速度，λ为声源信号的波长，β为双基地分置角，δ为目标航向与双基地分置角平分线的夹角。该方法本质上是一种几何描述，其优势是能够计算目标任意运动形式下的前向声散射多普勒频移，但也存在两个明显不足之处。一个是难以直观地建立目标多普勒频移与目标参数的对应关系，而且对多普勒频移关于目标运动时间的演变历程的描述不够清晰。另一个是要求记录目标航向角，否则在只给定目标轨迹坐标和航速的条件下，通常需要多层计算才能得到角度δ的值。显然，数值计算层数越多，误差积累越大，计算结果的精度也就越差。
第二种方法的计算原理与第一种方法的原理相同，但用代数描述替换了几何描述，直接建立了目标的前向声散射多普勒频移关于目标运动时间、穿越收发连线时刻、穿越点位置、航向角等参数的表达式，即：
Figure PCTCN2022076459-appb-000002
式中t为目标运动时间、t c为目标穿越收发连线的时刻、d为收发连线长度、d TR为目标穿越点到接收端的水平距离、α为目标航迹与基线的夹角。该方法的突出优势是能够直接描述目标的前向散射多普勒频移与各参数的依赖关系，并能够直观地刻画多普勒频移关于目标运动时间的演变历程，且不需要目标的航向记录。然而，该方法的缺点是只适用于目标轨迹为直线的情形，并不适合非规则目标轨迹的情形。
目前尚未有针对非规则轨迹的水中目标前向声散射多普勒频移的计算方法。
发明内容
本发明的目的是为了解决现有技术存在的上述缺陷，提供一种针对非规则轨迹的水中目标前向声散射多普勒频移的计算方法，
本发明解决其技术问题采用的技术方案是：非规则轨迹水中运动目标前向声散射多普勒频移计算方法，包括：(1)将发射端、目标轨迹和接收端的地球经纬度坐标转换为直角坐标，并依次标记为(x S,y S)、(x T,y T)和(x R,y R)；
(2)将目标轨迹坐标序列记为(x T(t i),y T(t i)),i＝1,2,…,N，计算所有时段内的平均航速
Figure PCTCN2022076459-appb-000003
(3)对目标轨迹进行平滑处理，获得虚拟直线轨迹，分别计算目标和接收端到其虚拟直线轨迹与基线交点的水平距离、虚拟直线轨迹与基线的夹角；
(4)利用步骤(2)和(3)计算得到的参数，计算各时刻目标的前向声散射多普勒频移。
进一步优选地，所述平滑处理的方法为：采用长度为l w点的时间窗并以步长t w点依次截取目标轨迹坐标序列，将每个窗口内轨迹坐标的算术平均值作为该时段内目标的等效轨迹坐标，平滑后的目标轨迹坐标为：
Figure PCTCN2022076459-appb-000004
Figure PCTCN2022076459-appb-000005
进一步优选地，目标和接收端到其虚拟直线轨迹与基线交点的水平距离的计算方法为：
在任意t i时刻，目标到其虚拟直线轨迹与基线交点
Figure PCTCN2022076459-appb-000006
的水平距离为：
Figure PCTCN2022076459-appb-000007
目标虚拟直线轨迹与基线的交点到接收端的水平距离为：
Figure PCTCN2022076459-appb-000008
目标当前位置到接收端的水平距离为：
Figure PCTCN2022076459-appb-000009
进一步优选地，虚拟直线轨迹与基线的夹角的计算方法为：应用余弦定理，得到t i时刻目标虚拟直线轨迹与基线的夹角：
Figure PCTCN2022076459-appb-000010
进一步优选地，目标的前向声散射多普勒频移的计算方法包括：
在t i时刻，将计算得到的参数：
Figure PCTCN2022076459-appb-000011
d TC(t i)、d TR(t i)、α(t i)及信号中心频率f c、环境声速c，一并代入线性轨迹的前向声散射多普勒频移参数公式：
Figure PCTCN2022076459-appb-000012
遍历平滑后的所有目标轨迹点，获得多普勒频移关于目标运动时间的变化曲线。
本发明的非规则轨迹水中运动目标前向声散射多普勒频移计算方法，具有的有益效果是：
解决了现有技术无法计算目标运动轨迹非规则时的前向声散射多普勒频移的问题；在对目标轨迹作平滑处理时采用等时间间隔方位采样并作算术平均计算，过程严谨；对估计目标虚拟直线航迹与基线的夹角时依据余弦定理，并利用几何关系计算目标、轨迹交点和接收端两两之间的水平距离，具有严格理论依据；在计算前向声散射多普勒频移时依据严格的参数方程，得到的结果准确。
附图说明
图1为本发明实施例提供的非规则轨迹水中运动目标前向声散射多普勒频移计算方法流程图；
图2目标轨迹分段线性近似示意图；
图3试验中某航程的发射端、接收端位置以及目标轨迹；
图4目标运动轨迹分段估计示意图；
图5平滑前后的目标轨迹对比曲线，其中，(a)为平滑前；(b)为平滑后；
图6目标虚拟直线轨迹与基线的交点分布图；
图7目标到其虚拟直线轨迹与基线交点的水平距离；
图8目标在基线的虚拟穿越点到接收端的水平距离；
图9目标的虚拟直线轨迹与基线的夹角信息；
图10目标前向声散射多普勒频移的估算结果；
图11前向声散射多普勒频移的近似计算与试验数据结果对比。
具体实施方式
为了便于理解本发明，下面结合附图和具体实施例，对本发明进行更详细的说明。附图中给出了本发明的较佳的实施例。但是，本发明可以以许多不同的形式来实现，并不限于本说明书所描述的实施例。相反地，提供这些实施例的目的是使对本发明公开内容的理解更加透彻全面。
实施例1本发明提供的非规则轨迹水中运动目标前向声散射多普勒频移计算方法，主要流程如图1所示，具体包括以下步骤：
(1)目标航迹坐标变换
在二维平面内选择合适的参考位置为原点建立直角坐标系，将发射端、接收 端和目标轨迹的地球经纬度坐标转换为直角坐标，并依次标记为(x S,y S)、(x T,y T)和(x R,y R)，其中的基线长度(收发连线长度)可表示为：
Figure PCTCN2022076459-appb-000013
(2)估算目标运动速度
将目标轨迹坐标序列记为(x T(t i),y T(t i)),i＝1,2,…,N，则目标在任意两个相邻时刻t i和t i+1之间的运动速度可直接求得：
Figure PCTCN2022076459-appb-000014
对所有时段内的航速求算术平均，得
Figure PCTCN2022076459-appb-000015
将该平均速度作为计算目标前向声散射多普勒频移时的目标运动速度。
(3)计算平滑处理后的目标轨迹坐标
采用长度为l w点的时间窗并以步长t w点依次截取目标轨迹坐标序列，将每个窗口内轨迹坐标的算术平均值作为该时段内目标的等效轨迹坐标，即可实现对目标原始轨迹的平滑，以减弱局部时段内目标轨迹剧烈摇摆对计算结果的影响。平滑后的目标轨迹坐标为：
Figure PCTCN2022076459-appb-000016
(4)计算目标轨迹与基线的交点坐标
对于平滑后的目标轨迹采用分段线性近似处理，即假设目标在任意两个相邻时刻t i和t i+1之间的运动轨迹为直线，如图2所示，这一虚拟直线轨迹必然会与基线交于某点。显然，在目标运动历程的不同时刻，目标的虚拟直线轨迹会与基线相交于多个不同的点。
利用目标在t i和t i+1两个时刻的位置坐标
Figure PCTCN2022076459-appb-000017
和
Figure PCTCN2022076459-appb-000018
求得目标在此时段内的虚拟直线轨迹方程：
Figure PCTCN2022076459-appb-000019
同时，由发射端和接收端的位置坐标可得基线所在的直线方程：
Figure PCTCN2022076459-appb-000020
联立(5)、(6)两式，得到t i时刻目标虚拟直线轨迹与基线的交点坐标为：
Figure PCTCN2022076459-appb-000021
Figure PCTCN2022076459-appb-000022
(5)计算目标、轨迹交点和接收端两两之间的水平距离
在任意t i时刻，目标到其虚拟直线轨迹与基线交点
Figure PCTCN2022076459-appb-000023
的水平距离为：
Figure PCTCN2022076459-appb-000024
目标虚拟直线轨迹与基线的交点到接收端的水平距离为：
Figure PCTCN2022076459-appb-000025
目标当前位置到接收端的水平距离为：
Figure PCTCN2022076459-appb-000026
(6)计算目标虚拟直线轨迹与基线的夹角
应用余弦定理并联立(9)、(10)和(11)式，得到t i时刻目标虚拟直线轨迹与基线的夹角：
Figure PCTCN2022076459-appb-000027
(7)计算目标的前向声散射多普勒频移
在t i时刻，将对目标真实轨迹记录处理后的参数：
Figure PCTCN2022076459-appb-000028
d TC(t i)、d TR(t i)、α(t i)连同信号中心频率f c、环境声速c，一并代入线性轨迹的前向声散射多普勒频移参数公式：
Figure PCTCN2022076459-appb-000029
遍历平滑后的所有目标轨迹点，依次经过步骤(4)-(7)的计算，得到各时刻目标的前向声散射多普勒频移，最终得到对应的多普勒频移关于目标运动时间的变化曲线。
实施例2利用2011年千岛湖缩尺目标前向声散射探测试验的目标航迹数据和目标前向声散射多普勒频移提取结果对本发明的算法进行验证。
试验中的发射端和接收端分置、间距约为1100米。目标为含泡沫夹层的双层铝板组合体(无自动力)，由拖船通过长度为10米的柔性绳拖拽穿越收发连线。发射端、接收端位置以及目标航迹如图3所示。试验中声源发射信号的中心频率f c＝10千赫兹，试验水层的声速近似恒定，声速值c≈1485米/秒。受风和水流影响，拖船的运动轨迹并非直线且存在较显著的偏转和摇摆。试验中采用便携式GPS设备记录拖船的真实轨迹位置信息，采样间隔为1秒。
(1)估算目标航速
将(2)式和(3)式依次应用于图3的目标轨迹序列，得到航速估计结果示于图4，其中点划线表示实测的拖船航速，速度值的起伏振荡源于拖船轨迹的摇摆。实线为求算术平均后的结果，约为0.5米/秒，将该值作为目标的运动速度。
(2)目标轨迹平滑
采用时间长度为5秒的矩形窗以3秒为步长对拖船位置点序列滑动截取，并以每次截取的五个位置点的算术平均值作为目标在该时刻的位置，从而实现对拖船原始轨迹的平滑处理。图5(a)和图5(b)分别示出了平滑前、后的拖船轨迹，可见平滑处理能够减弱局部时段的剧烈震荡。如前所述，因拖船与目标通过 柔性绳连接，故可把平滑后的轨迹视为目标的真实轨迹。
(3)目标轨迹与基线的交点坐标分布
图6给出了利用图5(b)的目标轨迹信息经(7)式和(8)式计算得到的目标虚拟直线轨迹与基线的交点分布(*号)。结果表明：由于目标轨迹并非直线形式，经分段线性近似处理后各时刻的虚拟轨迹与基线的交点位置不同于目标的真实穿越位置，但也大都聚集在真实位置附近区域。
(4)目标到轨迹交点的水平距离
图7给出了由(9)式得到的整个航程中目标到其虚拟直线轨迹与基线交点的水平距离计算结果。显然，目标在基线的虚拟穿越点与实际穿越点的位置偏差越大，则d TC的取值也越大。但是总体的轨迹演变趋势是清晰的，尤其当目标位于基线附近时，距离波动较小。
(5)轨迹交点和接收端的水平距离
由(10)式得到的计算结果示于图8，目标在基线的虚拟穿越点到接收端的水平距离变化趋势与图6中的虚拟穿越点在基线上的分布形式保持一致。对比图8和图7可知：目标位置越是靠近基线，各个距离参量的起伏程度也就越小。
(6)目标虚拟直线轨迹与基线的夹角
图9给出了(12)式计算的目标虚拟直线轨迹与基线的夹角信息。当目标刚好穿越收发连线时，目标航迹与基线的夹角会变为其补角。因而，在目标穿越基线的时刻航迹夹角会存在一定程度的跃变。目标航向越是偏离正橫方向(α＝90°)，跃变量就越大。但是，这里的角度跃变并不影响对目标前向散射多普勒频移的计算结果。
(7)计算目标的前向声散射多普勒频移
将从目标真实轨迹记录中提取的参数：
Figure PCTCN2022076459-appb-000030
d TC(t)、d TR(t)、α(t)连同信号中心频率f c、环境声速c，一并代入(13)式，得到的前向声散射多普勒频移曲线示于图10。
(8)数值计算与数据分析结果比对
由于发射端和接收端的位置均固定，直达波的多普勒频移为零。水中运动目标穿越收发连线时目标的前向声散射波存在时变的多普勒频移。但由于前向声散 射波通常与直达波干涉在一起，最终效果是使得接收声场发生低频调制现象。提取接收信号包络并对该包络作时频分析得到了图11所示的多普勒频移条纹。穿越收发连线的目标散射波对应了图中“V”型多普勒频移条纹，直达波则对应了多普勒频移近似为零的水平条纹。
本方法得到的多普勒频移曲线如图11的点划线所示，该曲线所表征的多普勒频移范围与变化趋势均同数据分析得到的多普勒频移条纹一致，结果证实了本发明方法的可行性。

Claims (5)

  1. 非规则轨迹水中运动目标前向声散射多普勒频移计算方法，其特征在于，包括：
    (1)将发射端、目标轨迹和接收端的地球经纬度坐标转换为直角坐标，并依次标记为(x S,y S)、(x T,y T)和(x R,y R)；
    (2)将目标轨迹坐标序列记为(x T(t i),y T(t i)),i＝1,2,…,N，计算所有时段内的平均航速
    Figure PCTCN2022076459-appb-100001
    (3)对目标轨迹进行平滑处理，获得虚拟直线轨迹，分别计算目标和接收端到其虚拟直线轨迹与基线交点的水平距离、虚拟直线轨迹与基线的夹角；
    (4)利用步骤(2)和(3)计算得到的参数，计算各时刻目标的前向声散射多普勒频移。
  2. 根据权利要求1所述的非规则轨迹水中运动目标前向声散射多普勒频移计算方法，其特征在于，所述平滑处理的方法为：采用长度为l w点的时间窗并以步长t w点依次截取目标轨迹坐标序列，将每个窗口内轨迹坐标的算术平均值作为该时段内目标的等效轨迹坐标，平滑后的目标轨迹坐标为：
    Figure PCTCN2022076459-appb-100002
    Figure PCTCN2022076459-appb-100003
  3. 根据权利要求2所述的非规则轨迹水中运动目标前向声散射多普勒频移计算方法，其特征在于，目标和接收端到其虚拟直线轨迹与基线交点的水平距离的计算方法为：
    在任意t i时刻，目标到其虚拟直线轨迹与基线交点
    Figure PCTCN2022076459-appb-100004
    的水平距离为：
    Figure PCTCN2022076459-appb-100005
    目标虚拟直线轨迹与基线的交点到接收端的水平距离为：
    Figure PCTCN2022076459-appb-100006
    目标当前位置到接收端的水平距离为：
    Figure PCTCN2022076459-appb-100007
  4. 根据权利要求3所述的非规则轨迹水中运动目标前向声散射多普勒频移计算方法，其特征在于，虚拟直线轨迹与基线的夹角的计算方法为：应用余弦定理，得到t i时刻目标虚拟直线轨迹与基线的夹角：
    Figure PCTCN2022076459-appb-100008
  5. 根据权利要求4所述的非规则轨迹水中运动目标前向声散射多普勒频移计算方法，其特征在于，目标的前向声散射多普勒频移的计算方法包括：
    在t i时刻，将计算得到的参数：
    Figure PCTCN2022076459-appb-100009
    d TC(t i)、d TR(t i)、α(t i)及信号中心频率f c、环境声速c，一并代入线性轨迹的前向声散射多普勒频移参数公式：
    Figure PCTCN2022076459-appb-100010
    遍历平滑后的所有目标轨迹点，获得多普勒频移关于目标运动时间的变化曲线。
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