CN113721185B - Method for estimating underwater target azimuth of land frame slope sea area - Google Patents
Method for estimating underwater target azimuth of land frame slope sea area Download PDFInfo
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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
- G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
- G01S3/80—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using ultrasonic, sonic or infrasonic waves
- G01S3/802—Systems for determining direction or deviation from predetermined direction
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Abstract
The invention relates to a land frame slope sea area underwater target azimuth estimation method, which aims at the problem of slope sea area underwater target azimuth estimation and applies a technology of separating a simple wave mode to a slope sea area horizontal array receiving signal, separates different order modes, then eliminates a high order mode greatly influenced by horizontal refraction, and reserves a low order mode little influenced by horizontal refraction. Simulation results show that in a typical practical marine environment, compared with a traditional method, the method can reduce the target azimuth estimation error from 7.7 degrees to 1.5 degrees. The method is expected to provide technical support for estimating the direction of the underwater target in the slope sea area.
Description
Technical Field
The invention belongs to the field of ships and ocean engineering, and relates to a land frame slope sea area underwater target azimuth estimation method.
Background
The land-based slope is a transition zone connecting land and a deep sea plain, and the sea area where the land-based slope is positioned is called a land-based slope sea area, and the sea area is a necessary path for the navy of China to go from shallow sea to deep sea; on the other hand, the enemy underwater target is close to the offshore field of China, and a large Liu Po sea area is the requisite path of the enemy underwater target, so that the method has important significance for accurately positioning the underwater target entering the offshore field of China, early warning, accurate striking and the like of army. However, due to the existence of the slope seabed, the sound wave can generate a horizontal refraction effect when colliding with the seabed in the process of propagation, so that the sound ray deflects at the horizontal plane, and the estimated target azimuth can deviate from the true azimuth seriously. The paper of "acoustic vector field impact analysis by elastic seabed wedge sea area sound field modeling and horizontal refraction" indicates that the azimuth angle estimated on certain areas can deviate by more than 20 degrees from the true azimuth angle due to the existence of wedge seabed, and the prior art can hardly accurately locate the target entering the continental slope sea area.
Disclosure of Invention
Technical problem to be solved
In order to avoid the defects of the prior art, the invention provides a land frame slope sea area underwater target azimuth estimation method, which is used for preprocessing signals received by a slope sea area, separating different order modes, eliminating high order modes greatly influenced by horizontal refraction, and only using low order modes weakly influenced by horizontal refraction to perform target azimuth estimation, thereby improving the accuracy of target azimuth estimation.
Technical proposal
A land frame slope sea area underwater target azimuth estimation method is characterized by comprising the following steps:
step 1: the employed Warping transformation operator is
Signals received by individual hydrophones
And (3) performing a Warping transformation, wherein the received signal transformed into the Warping domain is as follows:
wherein:
t 0 ＝r/c 0 r is the horizontal distance between the acoustic source and the receiving hydrophone, c 0 Is the reference sound velocity in water, t' is the warping time;
step 2: performing time-frequency analysis on g (t') to obtain single-order mode g of the Warping domain after separation l (t′)；
Step 3: with inverse transform operator expressions as
For single-order mode g l (t') performing reverse transformation to obtain a first-order modal received signal;
step 4: performing short-time Fourier transform on the first-order modal received signals of M array elements to obtain a frequency domain value X of the first-order modal received signals l (f, j) and then obtaining a first order modal cross-spectral density matrix R by using l (f)：
Step 5: the first order modal signal beam response at different azimuth angles θ:
B l (θ)＝ω H (θ)R l (f)ω(θ)
wherein ω (θ) is a steering vector:
ω(θ)＝[a 1 (θ) a 2 (θ) … a M (θ)] T
a m ＝e -jk(m-1)dsinθ
wherein k is wave number in water, d is the distance between two adjacent hydrophones;
when calculating l=1, B 1 And taking the theta corresponding to the maximum value as the true target azimuth.
Advantageous effects
The invention provides a land frame slope sea area underwater target azimuth estimation method, which aims at the problem of slope sea area underwater target azimuth estimation, applies a technology of separating a simple wave mode to a slope sea area horizontal array to receive signals, separates different order modes, then eliminates a high order mode greatly influenced by horizontal refraction, and reserves a low order mode less influenced by horizontal refraction. Simulation results show that in a typical practical marine environment, compared with a traditional method, the method can reduce the target azimuth estimation error from 7.7 degrees to 1.5 degrees. The method is expected to provide technical support for estimating the direction of the underwater target in the slope sea area.
Drawings
FIG. 1 is a flow chart of a framework embodying the present invention
FIG. 2, schematic diagram of a wedge-shaped marine waveguide
Fig. 3 and 2 show the track diagrams of the acoustic ray of the first two-order modes in the waveguide
Fig. 4, A1 station (a) receives a signal and (b) time-frequency diagram; (c) Received signal of warp domain and (d) time-frequency diagram thereof
Fig. 5, A1 site receives (a) A1 st order mode and (b) a 2 nd order mode, wherein the solid line indicates that the effect of horizontal refraction is considered, and the dash-dot line indicates that the effect of horizontal refraction is ignored.
Fig. 6, target azimuth estimated using (a) full wave signal, 1-order modality, 2-order modality, 1-order modality first arrival envelope, and (b) local amplification result. The arrowed line indicates the true position of the target.
Detailed Description
The invention will now be further described with reference to examples, figures:
the invention is realized by the following technical scheme:
(1) A slope sea area receiving signal modal separation method;
(2) Analyzing the influence of horizontal refraction on each order of modes in the slope sea area;
(3) A slope sea area target azimuth estimation method based on single-mode signals.
The modal separation of the receiving signals in the slope sea area is realized by adopting a Warping transformation technology. The warping transform is a nonlinear transform of a time axis, and is a signal waveform obtained by superimposing a plurality of received modal simple waves:
wherein:
s (t) is a wideband pulse signal emitted by a sound source, S (f) is a corresponding signal spectrum, and time transformation is adopted
The received signal p (r, t) is transformed into:
wherein the method comprises the steps of
t 0 ＝r/c 0 R is the horizontal distance between the acoustic source and the receiving hydrophone, c 0 Is the reference sound velocity in water, the average sound velocity in water is general, and t' is the warping time. g (t', r) is a signal after the received signal p (t) warping transform. The different orders Jian Zhengbo are separated from each other in the Warping domain, and the first order Jian Zhengbo component g of the Warping domain can be obtained by filtering l (t') and then obtaining the required p by using the reverse transformation of the warping l (t)。
The M-element horizontal array with the distance d is arranged at a certain depth under water, and the first-order modal signal received by the M-th array element is set as p lm (t) the vector formed by the first-order modal sound pressure signals received by the horizontal array is:
X l (t)＝[p l1 (t) p l2 (t) ···· p lM (t)] T
constructing a steering vector ω (θ):
ω(θ)＝[a 1 (θ) a 2 (θ) … a n (θ)] T
wherein a is n ＝e -jk(n-1)dsinθ K is the wave number. Cross spectral density matrix R of first order modal signal received by horizontal array l (f) Can be written as:
R l (f)＝E[X l (f)X l H (f)]
wherein X is l (f) Is X l (t) frequency domain values after fourier transform. In practice R l (f) The following equation can be used to find the L sets of sampled data:
where J is the number of beats of the signal, i.e., the data over the observation time is equally divided into J portions. And performing short-time Fourier transform on each snapshot data to obtain a frequency domain value Y (f, j) under each snapshot data. Then, beam scanning is carried out in the azimuth interval range, so that beam responses at all angles are obtained, and the response of the mth-order mode at the angle theta is as follows:
B l (θ)＝ω H (θ)R l (f)ω(θ)
B l θ corresponding to the maximum value of (θ) is the direction of arrival. The existing research shows that the high-order mode is more influenced by horizontal refraction, and the low-order mode is less influenced by horizontal refraction, so that the target azimuth estimation error can be improved by using the mode signal transmitted by the first order for beam forming.
Specific examples:
the invention firstly carries out modal separation on all array element received signals, carries out Warping transformation on the signals received by each array element to transform the received signals into a Warping domain, and the frequencies corresponding to each order Jian Zhengbo in the Warping domain are cut-off frequencies, so that all the order modes are separable from each other, and can be filtered in a frequency domain to obtain single-order mode Warping domain signals. And then carrying out the warp inverse transformation on the signal of the single-order warp domain so as to obtain a single-order modal received signal. And carrying out beam forming on the single-order modal signals to obtain beam responses on different azimuth angles, finally obtaining the direction of arrival of the single-order modal signals, and giving an estimation result closest to the true azimuth angle of the target by combining the transmission characteristics of the sound field of the slope sea area.
The specific flow is shown in fig. 1, and specifically comprises the following steps:
step one: the signals received by each hydrophone are subjected to simple wave mode separation, and the signals received by each hydrophone are assumed to be
The p (t) is subjected to the warp transformation, and the warp transformation operator is +.>
The received signal transformed into the Warping domain is:
wherein the method comprises the steps of
t 0 ＝r/c 0 R is the horizontal distance between the acoustic source and the receiving hydrophone, c 0 Is the reference sound velocity in water, t' is the warping time.
Step two: the method comprises the steps that firstly, a received signal g (t ') of a Warping domain can be obtained, time-frequency analysis is carried out on the g (t'), and frequencies of different order modes on a time-frequency domain are different, so that different order modes can be separated through frequency filtering, and a single order mode g of the Warping domain after separation is obtained l (t′)。
Step three: for g l (t') performing a warp inverse transform with an inverse transform operator expression of
By p l (t)＝|w -1 (t′)| 1/2 g l [w -1 (t′)]A first order modal receive signal may be obtained.
Step four: let the first order modal signal received by the mth receive primitive be p lm (t) the signals received by the M array elements constitute a vector:
X l (t)＝[p l1 (t) p l2 (t) ···· p lM (t)] T
dividing each hydrophone receiving signal into J parts equally, wherein the m-th order modal signal of the J-th segment data received by the horizontal array is X l (t, j) performing Fourier transform to obtain frequency domain value X l (f, j) and then obtaining a first order modal cross-spectral density matrix R by using l (f)：
The beam response of the first order mode signal at different azimuth angles θ is obtained by the following equation.
B l (θ)＝ω H (θ)R l (f)ω(θ)
Wherein ω (θ) is a steering vector:
ω(θ)＝[a 1 (θ) a 2 (θ) … a M (θ)] T
a m ＝e -jk(m-1)dsinθ
where k is the wave number in water and d is the spacing between two adjacent hydrophones.
The azimuth angle estimated when l=1 is theoretically closest to the target true azimuth.
For a better description of the objects and advantages of the present invention, the following is a further description of the invention with reference to the accompanying drawings and examples:
FIG. 2 shows a schematic view of a typical sloped ocean waveguide with a sea-bottom tilt angle of 2.86 degrees, a sea-bottom sound speed of 1500m/s, a sea-bottom sound speed of 1650m/s, a sound source depth of 40m, and a receiving point A1 in the forward transverse direction of the sound source 16km from the sound source. Fig. 3 shows a sound ray trace diagram of A1-order mode and a 2-order mode of the sound source under the condition shown in fig. 2, and it can be seen from the figure that at a point A1, the 1-order mode is approximately transmitted along the direction of the connecting line between the sound source and the receiving point, and the 2-order mode transmission azimuth angle is seriously deviated from the connecting line between the sound source and the receiver, which indicates that the influence of horizontal refraction on the higher-order mode is obviously stronger than that on the lower-order mode. Therefore, a low-order mode is needed for the direction estimation.
Fig. 4 (a) shows a 25Hz-75Hz broadband signal transmitted by a sound source received by an A1 receiving point, and fig. 4 (b) shows a corresponding time-frequency diagram, where it can be seen that different order modes have overlapping in a frequency domain, and it is difficult to directly separate the different order modes. Fig. 4 (c) and fig. 4 (d) show a time-frequency diagram and a received signal after the Warping transformation, respectively, and it can be seen that the front two-order modes after the transformation are separable in the frequency domain, the two-order modes can be easily separated by adopting frequency filtering, and then the Warping inverse transformation is utilized to obtain the separated modal signals of each order.
Fig. 5 shows the first two modes after separation, wherein the blue solid line represents the received signal taking into account the horizontal refraction effect and the black dashed line represents the received signal taking into account no horizontal refraction effect. It can be seen that the presence of the ramp has a significant effect on the received signal, especially on higher order modes than on lower order modes.
Fig. 6 shows the target azimuth angle estimated by the full-wave signal, the 1-order mode, the 2-order mode, and the 1-order mode, and the arrowed line indicates the target real position, and from the result, the target real azimuth is 0 degrees, and the estimated results of the first-order arrival envelope by the full-wave signal, the 1-order mode, the 2-order mode, and the 1-order mode are-7.7 degrees, -2.3 degrees, -9.9 degrees, and-1.5 degrees, respectively. If the full wave signal is directly utilized, the estimated azimuth angle deviates from the true angle by 7.7 degrees, and the estimated error can be reduced to 1.5 degrees by adopting the invention. The proposed invention proved to be effective and viable.
The physical quantities and their meanings in this example are shown in Table 1.
Table 1 physical quantity and meaning thereof
Claims (1)
1. A land frame slope sea area underwater target azimuth estimation method is characterized by comprising the following steps:
step 1: the employed Warping transformation operator is
Signals received by individual hydrophones
Making a warp transformationThe received signal to the warp domain is:
wherein:
t 0 ＝r/c 0 r is the horizontal distance between the acoustic source and the receiving hydrophone, c 0 Is the reference sound velocity in water, t' is the warping time;
step 2: performing time-frequency analysis on g (t') to obtain single-order mode g of the Warping domain after separation l (t′)；
Step 3: with inverse transform operator expressions as
For single-order mode g l (t') performing reverse transformation to obtain a first-order modal received signal;
step 4: performing short-time Fourier transform on the first-order modal received signals of M array elements to obtain a frequency domain value X of the first-order modal received signals l (f, j) and then obtaining a first order modal cross-spectral density matrix R by using l (f)：
Step 5: the first order modal signal beam response at different azimuth angles θ:
B l (θ)＝ω H (θ)R l (f)ω(θ)
wherein ω (θ) is a steering vector:
ω(θ)＝[a 1 (θ)a 2 (θ)…a M (θ)] T
a m ＝e -jk(m-1)dsinθ
wherein k is wave number in water, d is the distance between two adjacent hydrophones;
when calculating l=1, B 1 And taking the theta corresponding to the maximum value as the true target azimuth.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5481505A (en) * | 1995-05-15 | 1996-01-02 | The United States Of America As Represented By The Secretary Of The Navy | Tracking system and method |
| CN109815942A (en) * | 2019-03-18 | 2019-05-28 | 西北工业大学 | Normal mode feature extracting method based on ambient sea noise signal |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5481505A (en) * | 1995-05-15 | 1996-01-02 | The United States Of America As Represented By The Secretary Of The Navy | Tracking system and method |
| CN109815942A (en) * | 2019-03-18 | 2019-05-28 | 西北工业大学 | Normal mode feature extracting method based on ambient sea noise signal |
Non-Patent Citations (1)
| Title |
|---|
| 楔形海域中三维效应对声源距离估计的影响分析;吴祖勇;秦继兴;王龙昊;张燕;;应用声学(第04期);全文 * |
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