CN112487887B - Method for improving signal-to-noise ratio of active target detection - Google Patents
Method for improving signal-to-noise ratio of active target detection Download PDFInfo
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- CN112487887B CN112487887B CN202011278977.1A CN202011278977A CN112487887B CN 112487887 B CN112487887 B CN 112487887B CN 202011278977 A CN202011278977 A CN 202011278977A CN 112487887 B CN112487887 B CN 112487887B
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- 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
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Abstract
The invention discloses a method for improving the signal-to-noise ratio of active target detection, which is suitable for the detection of an active target. The method comprises the steps of designing a plurality of copy signals by setting the scale and the speed range of an active target and performing matched filtering operation with received signals one by one; searching the maximum value in the matched filtering results to obtain the scale and speed information which are most matched with the echo signal of the active target, and designing a copy signal according to the scale and speed information; and performing matched filtering operation again by using the optimized copy signal and the echo signal, so that the signal-to-noise ratio of the active target detection can be improved. By the optimization design of the copy signal, the signal-to-noise ratio of the matched filtering result is effectively improved, and therefore the detection capability of the active target is improved.
Description
Technical Field
The invention relates to a method for improving the detection signal-to-noise ratio of an active target, in particular to a method for improving the detection signal-to-noise ratio of the active target, which is suitable for the detection of the active target.
Background
Signal detection is an important task of detection equipment such as sonar and radar. The active sonar or the radar transmits sound waves or electromagnetic waves in a certain form, and performs signal detection and feature extraction on the reflected echoes of the target, so that the active target is positioned, classified and tracked. Classical detection theory states that the best receiver to detect a known signal in a white gaussian noise background is a matched filter, which is also the most basic receiver commonly used in many detection systems such as sonar. The response function of the matched filter is a delayed conjugate mirror waveform of the matched signal u (t), which is also referred to as the replica signal or reference signal of the matched filter. For a typical input signal R (t), the output of the matched filter is y (t) = R vu (t 0 -t), wherein R vu Is the cross-correlation value of signal r (t) against u (t). t = t 0 When, y (t) 0 )＝R vu (0) Thus, the matched filter acts as a cross-correlator which can calculate the cross-correlation function.
In practical applications, the copy signal u (t) is generally a transmission signal in an active sonar or radar system. However, due to the reasons of complex channel influence, serious background interference and the like, and the sound stealth capability of the active target has been greatly improved in recent years, the functional requirements of an active detection system cannot be met by applying a conventional matched filtering method to active target detection. How to improve the detection capability of the active target, especially the performance of the matched filtering process, is one of the hot problems of the current research.
Disclosure of Invention
The purpose of the invention is as follows: in order to overcome the defects of the prior art, the method for improving the signal-to-noise ratio of the active target detection is provided, and the signal-to-noise ratio of the matched filtering result is effectively improved through the optimization design of the copy signal, so that the detection capability of the active target is improved.
In order to achieve the technical purpose, the method for improving the signal-to-noise ratio of active target detection of the invention uses an active sonar to emit an acoustic signal into water, the signal meets an active target to generate an echo signal when being transmitted in water, the emitted signal is selected from a linear frequency modulation signal or a hyperbolic frequency modulation signal, the pulse width of the emitted signal is T seconds, and the lower limit frequency is f 1 Hertz at an upper limit frequency f 2 Hertz, the sampling frequency of the active sonar system is f s Hertz, the propagation speed of sound waves in water is c m/s; the radial speed of the active target is v meters per second, and the dimension is l meters; the signal-to-noise ratio of the received signal is A decibels;
the method comprises the following steps:
firstly, setting a scale range of an active target, and extracting M scale values in the scale range of the active target; then setting a speed range of the active target, and extracting N speed values from the range; time series X constructed sequence X formed by active sonar emission signal i (ii) a Will sequence X i Performing variable sampling processing to obtain a copy signal sequence X corresponding to each speed ij (ii) a Then, the active sonar transmits the echo signal sequence R and copy signal sequence X received after the emission signal ij Performing matched filtering operation and taking the maximum value to obtain a matrix with the size of M multiplied by N; the mth row and the nth column of the maximum position in the matrix are the positions where the matching peak values are maximum; using sequence X i Constructing a sequence Y, and carrying out variable sampling processing on the sequence Y to obtain a copy signal sequence U; and matching and filtering the echo signal sequence R and the copy signal sequence U received by the active target detection system, so that the signal-to-noise ratio of the active target detection can be improved.
The scale range of the active target is Len 1 ～Len 2 And M scale values extracted from the range are respectively L i ＝Len 1 +i*(Len 2 -Len 1 ) (M-1), i =0, 1.., M-1, the dimension of the active target to be measured does not exceed the lower boundary Len 1 And an upper bound Len 2 A range of (a); master and slaveThe speed range of the moving target is Vel 1 ～Vel 2 Extracting N speed values, each V j ＝Vel 1 +j*(Vel 2 -Vel 1 ) V (N-1), j =0, 1.., N-1, with a speed range of the lower bound Vel 1 To the upper boundary Vel 2 In the meantime.
Using the formula: x i ＝x 1i +x 2i Wherein
Time series X construction sequence X formed by active sonar emission signal i And c is the speed of wave propagation.
Sequence X i I =0, 1.., M-1 is subjected to a variable sampling process to obtain a signal corresponding to each velocity V j Copy signal sequence X of ij : sampling rate of f s Is changed into f s c/(c-2V j )，j＝0,1,...,N-1；
An echo signal sequence R and a copy signal sequence X received by the active sonar ij Performing matched filtering operation and taking the maximum value Max ij I =0,1, ·, M-1, j =0,1, ·, N-1; this results in a matrix of size mxn:
sequence Y = Y 1 +Y 2 Wherein, in the step (A),
the sequence Y is subjected to variable sampling processing, namely the sampling rate is f s Is changed into f s c/(c-2V n ) And obtaining a copy signal sequence U.
All copy signals in the previous period can be stored and directly selected to be U = X mn As a copy signal, or the sequence Y is subjected to a variable sampling process to regenerate the copy signal and applied to avoid the need to apply X ij I =0, 1., M-1, j =0, 1., N-1 are all stored, thereby reducing the occupation of storage resources.
Has the advantages that: the invention searches the scale information and the speed information of the active target in a certain range, and optimizes the copy signal, thereby occupying less storage resources and effectively improving the signal-to-noise ratio of the active target detection.
Drawings
FIG. 1 is a flow chart of a method of improving active target detection signal-to-noise ratio in accordance with the present invention;
fig. 2 is a graph comparing the matched filtering result of the transmit signal as the copy signal with the matched filtering result of the optimized copy signal according to the present invention.
Detailed Description
Embodiments of the invention are further described below with reference to the accompanying drawings:
as shown in figure 1, the method for improving the signal-to-noise ratio of active target detection of the invention uses an active sonar to emit an acoustic signal into water, the signal meets the active target to generate an echo signal when propagating in water, the emitted signal is selected from a linear frequency modulation signal or a hyperbolic frequency modulation signal, the pulse width of the emitted signal is T seconds, and the lower limit frequency is f 1 Hertz at an upper frequency limit of f 2 Hertz, the sampling frequency of the active sonar system is f s Hertz, the propagation speed of sound waves in water is c meters per second; the radial speed of the active target is v meters per second, and the dimension is l meters; the signal-to-noise ratio of the received signal is A decibels;
the method comprises the following steps:
firstly, setting the scale range of an active target, wherein the scale range of the active target is Len 1 ～Len 2 And M scale values extracted from the range are respectively L i ＝Len 1 +i*(Len 2 -Len 1 ) (M-1), i =0, 1.., M-1, the dimension of the active target to be measured does not exceed the lower boundary Len 1 And an upper bound Len 2 A range of (a); the speed range of the active target is Vel 1 ～Vel 2 Extracting N speed values, each V j ＝Vel 1 +j*(Vel 2 -Vel 1 ) V (N-1), j =0, 1.., N-1, with a speed range of the lower bound Vel 1 To the upper boundary Vel 2 To (c) to (d);
then setting the active targetAnd extracting N speed values from the range; time series X construction sequence X formed by active sonar emission signals i Using the formula: x i ＝x 1i +x 2i In which
Time series X construction sequence X formed by active sonar emission signal i And c is the speed of wave propagation;
will sequence X i I =0, 1., M-1 is subjected to a variable sampling process to obtain a signal corresponding to each velocity V j Copy signal sequence X of ij : sampling rate of f s Is changed into f s c/(c-2V j ) J =0, 1.., N-1. Copy signal generation by simulation software, such as variable sampling by using sample in matlab, internal algorithm involving FIR filter design and rate conversion, and other methods
The sampling interval is from 0 second to
Sampling is carried out within seconds, namely T is set as the pulse width of the signal, then
At a frequency f 0 Taking the single-frequency signal of (1) as an example, the sequence x = sin (2 π f) can be obtained 0 t) wherein F s ＝f s When x is the original copy signal; f s ＝f s c/(c-2V j ) X is the copy signal after variable sampling.
Then, an echo signal sequence R and a copy signal sequence X received by the active sonar are obtained ij Performing matched filtering operation and taking the maximum value Max ij I =0,1, · M-1, j =0,1,. · N-1; this results in a matrix of size mxn:
the mth row and the nth column of the maximum position in the matrix are the positions where the matching peak values are maximum;
using sequence X i Constructing a sequence Y, and performing variable sampling processing on the sequence Y to obtain a copy signal sequence U; sequence Y = Y 1 +Y 2 Wherein, in the step (A),
the sequence Y is subjected to variable sampling processing, namely the sampling rate is changed from f s Is changed to f s c/(c-2V n ) Obtaining a copy signal sequence U;
the echo signal sequence R received by the active target detection system and the copy signal sequence U are subjected to matched filtering operation, so that the signal-to-noise ratio of active target detection can be improved; all the copy signals in the previous stage can be directly stored, and U = X is selected mn As a copy signal, or by regenerating the copy signal and applying it in the previous step, to avoid copying X ij I =0, 1., M-1, j =0, 1., N-1 are all stored, thereby reducing the occupation of storage resources.
The first embodiment is as follows:
assuming that the emission signal of the active sonar is a linear frequency modulation signal, the pulse width is 1 second, the lower limit frequency is 950Hz, the upper limit frequency is 1050Hz, and the sampling frequency f of the active sonar system s 20kHz, and the propagation speed c of sound waves in water is 1500 m/s; the radial speed of the active target is 2 m/s, and the dimension is 100 m; the signal-to-noise ratio of the received signal is-20 dB. The signal-to-noise ratio of active target detection is improved according to the following steps:
(1) Setting the scale range of the active target to be 20-200 m, and sampling at equal intervals in the range to obtain 91 scale values L i = (20 + i × 2) meters, i =0,1, ·,90;
(2) Construction sequence X i ＝x 1i +x 2i Wherein
i =0,1.., 90,x is the sequence of transmitted signals in an active target detection system;
(3) Setting the speed range of the active target to be-15 m/s, and sampling at equal intervals in the range to obtain 61 speed values which are V respectively j = (-15 + j 0.5) m/s, j =0,1, ·,60;
(4) Will sequence X i I =0, 1.., 90 is subjected to a variable sampling process, i.e., the sampling rate is represented by f s Is changed into f s c/(c-2V j ) J =0, 1.., 60, obtained for each speed V j Copy signal X of ij ；
(5) The echo signal sequence R and the copy signal sequence X are combined ij Performing matched filtering operation and taking the maximum value Max ij I =0, 1., 90, j =0, 1., 60, resulting in a matrix size of 91 × 61
(6) Searching a maximum value MAX in a matrix Max to obtain an m-th row and an n-th column of the matrix at the position of the matrix, wherein m and n can change due to the fact that noise in each experiment is not identical;
(7) Construction sequence Y = Y 1 +Y 2 Wherein
And the sequence Y is subjected to variable sampling processing, namely the sampling rate is changed from f s Is changed into f s c/(c-2V n ) Obtaining a copy signal sequence U;
(8) And (4) carrying out matched filtering operation on the echo signal sequence R and the copy signal sequence U in (7). Fig. 2 is a graph comparing the matched filtering results of a transmit signal as a copy signal and the optimized copy signal according to the present invention. As indicated by the circle marks in the figure, after the copy signals are optimally designed, whether echo signals exist or not can be more easily distinguished from the matched filtering results, and the arrival time of the echo signals is obtained; compared with the traditional matched filtering result which takes the emission signal as the copy signal, the detection effect of the active target can be effectively improved.
Claims (7)
1. A method for improving the signal-to-noise ratio of active target detection uses an active sonar to emit an acoustic signal into water, the signal meets an active target to generate an echo signal when being transmitted in the water, and the emitted signal is selected to be a linear frequency modulation signal or a hyperbolic frequency modulation signal, which is characterized in that: the pulse width of the transmitted signal is T seconds, and the lower limit frequency is f 1 Hertz at an upper frequency limit of f 2 Hertz, the sampling frequency of the active sonar system is f s Hertz, the propagation speed of sound waves in water is c m/s; the radial speed of the active target is v m/s, and the scale is l m; the signal-to-noise ratio of the received signal is A decibels;
the method comprises the following steps:
firstly, setting a scale range of an active target, and extracting M scale values in the scale range of the active target; then setting a speed range of the active target, and extracting N speed values from the range; time series X constructed sequence X formed by active sonar emission signal i (ii) a Will sequence X i Performing variable sampling processing to obtain a copy signal sequence X corresponding to each speed ij (ii) a Then, the active sonar transmits the echo signal sequence R and copy signal sequence X received after the emission signal ij Performing matched filtering operation and taking the maximum value to obtain a matrix with the size of M multiplied by N; the mth row and the nth column of the maximum value position in the matrix are the positions where the matching peak values are maximum; using the sequence X i Constructing a sequence Y, and carrying out variable sampling processing on the sequence Y to obtain a copy signal sequence U; and matching and filtering the echo signal sequence R and the copy signal sequence U received by the active target detection system, so that the signal-to-noise ratio of the active target detection can be improved.
2. The method of claim 1 for improving signal-to-noise ratio of active target detection, wherein: the scale range of the active target is Len 1 ～Len 2 And M scale values extracted from the range are respectively L i ＝Len 1 +i*(Len 2 -Len 1 ) (M-1), i =0, 1.., M-1, the dimension of the active target to be measured does not exceed the lower boundary Len 1 And an upper bound Len 2 A range of (d); the speed range of the active target is Vel 1 ～Vel 2 Extracting N speed values, each V j ＝Vel 1 +j*(Vel 2 -Vel 1 ) V (N-1), j =0, 1.., N-1, with a speed range of the lower bound Vel 1 To the upper boundary Vel 2 In between.
3. The method of claim 1, wherein the formula is used to: x i ＝x 1i +x 2i Wherein
Time series X construction sequence X formed by active sonar emission signal i And c is the speed of wave propagation.
4. The method of claim 1 for improving signal-to-noise ratio of active target detection, wherein: sequence X i I =0, 1.., M-1 is subjected to a variable sampling process to obtain a signal corresponding to each velocity V j Copy signal sequence X of ij : sampling rate of f s Is changed into f s c/(c-2V j )，j＝0,1,...,N-1。
5. The method of claim 1 for improving the signal-to-noise ratio of active target detection, wherein: an echo signal sequence R and a copy signal sequence X received by the active sonar ij Performing matched filtering operation and taking the maximum value Max ij I =0,1, · M-1, j =0,1,. · N-1; this results in a matrix of size mxn:
6. according to the rightThe method for improving the signal-to-noise ratio of active target detection according to claim 1, characterized in that: sequence Y = Y 1 +Y 2 Wherein, in the step (A),
the sequence Y is subjected to variable sampling processing, namely the sampling rate is changed from f s Is changed into f s c/(c-2V n ) And obtaining a copy signal sequence U.
7. The method of claim 5, wherein the step of improving the signal-to-noise ratio of active target detection comprises: all copy signals in the previous period can be stored and directly selected to be U = X mn As a copy signal, or the sequence Y is subjected to a variable sampling process to regenerate the copy signal and applied to avoid the need to apply X ij I =0, 1., M-1, j =0, 1., N-1 are all stored, thereby reducing the occupation of storage resources.
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