CN109407078B - Double-adaptive copy correlator method - Google Patents

Double-adaptive copy correlator method Download PDF

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CN109407078B
CN109407078B CN201811009885.6A CN201811009885A CN109407078B CN 109407078 B CN109407078 B CN 109407078B CN 201811009885 A CN201811009885 A CN 201811009885A CN 109407078 B CN109407078 B CN 109407078B
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CN109407078A (en
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王青翠
权恒恒
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715th Research Institute of CSIC
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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
    • G01S7/537—Counter-measures or counter-counter-measures, e.g. jamming, anti-jamming
    • 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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Abstract

The invention discloses a double self-adaptive copy correlator method, which selects a noise signal highly correlated with background noise in a received signal as an input signal of a first-level self-adaptive filtering, uses the received signal as a first-level self-adaptive reference input, performs a first-level self-adaptive algorithm, uses a residual signal of the first-level self-adaptive filtering as a reference signal of a second-level self-adaptive filtering, uses the input signal as an original transmitting signal, performs the second-level self-adaptive filtering, and finally uses the first-level self-adaptive filtering to obtain a noise reduction received signal and a second-level self-adaptive correction reference signal as copy correlation to obtain the output of the double self-adaptive copy correlator. The invention utilizes the double self-adaptive technology to firstly carry out self-adaptive noise elimination on the received signal, improve the signal-to-noise ratio of the received signal, and then adaptively modify the reference signal on the basis of the noise elimination signal, thereby further improving the performance of the copy correlator and having important significance for improving the performance of the copy correlator under the complex environment.

Description

Double-adaptive copy correlator method
Technical Field
The invention relates to the field of sonar and sonar signal processing, in particular to a double-adaptive copy correlator method.
Background
Sonar is the main means for detecting and identifying targets in water and has wide application in military and civil fields. The active sonar judges the target by receiving the echo reflected by the target after the transmitted signal irradiates and analyzing the strength of the echo signal. The copy correlator is a signal processing method widely adopted by active sonar, and the classical detection theory proves that the copy correlator is the best receiver for detecting known signals in white Gaussian noise background. However, the marine environment is an unreliable time-varying complex channel, and is affected by factors such as sea surface, sea bottom reflection, multipath expansion, medium non-uniformity, random disturbance, and random fluctuation of an interface, and the like, the active sonar receiving signal generates signal distortion, which is represented by signal delay, doppler expansion, and the like, and thus cannot be well matched with the transmitting signal, which causes performance degradation of the replica correlator, and causes a plurality of correlation peaks to appear in the replica correlator due to multipath effect, resulting in performance degradation. Therefore, there is a need to improve the deficiencies of the replica correlator so that it can be adaptive to the environment.
There is proposed an adaptive replica correlator which adaptively extracts information of a channel, corrects a reference signal, and performs replica correlation with a received signal using the adaptive reference signal to improve a processing gain of a receiver. The invention provides a double-adaptive copy correlator on the basis of the adaptive copy correlator, and further improves the performance of the copy correlator.
Disclosure of Invention
The present invention is directed to overcome the deficiencies of the prior art and to provide a dual adaptive replica correlator method.
The purpose of the invention is achieved by the following technical scheme: the double-adaptive copy correlator method mainly comprises the following steps: selecting a noise signal highly correlated with background noise in a received signal as an input signal of a first-level self-adaptive filtering, taking the received signal as a first-level self-adaptive reference input, performing a first-level self-adaptive algorithm, taking a residual signal of the first-level self-adaptive filtering as a reference signal of a second-level self-adaptive filtering, taking the input signal as an original transmitting signal, performing a second-level self-adaptive filtering, and finally performing copy correlation on a noise-reduced received signal obtained by the first-level self-adaptive filtering and a modified reference signal obtained by the second-level self-adaptive filtering to obtain the output of a double-adaptive copy correlator.
The method specifically comprises the following steps:
the method comprises the following steps: selecting as input z for the first stage adaptation a noise signal that is highly correlated with noise in the received signal1(n)；
Step two: using the received signal as a first-stage adaptive reference input d1(n) performing a first-stage adaptive algorithm, wherein parameters such as adaptive step length and filter order are selected according to the amplitude of the input signal to obtain an output of
Figure RE-GDA0001950493000000011
Step three: the residual signal of the first stage adaptive filtering is e1(n)＝d1(n)-y1(n) using the residual signal as a reference signal for next stage adaptation, i.e. d2(n)＝e1(n), if the output signal of the first stage adaptive filtering is the estimation of the noise component in the received signal, the reference signal is used to subtract the output signal to obtain the received signal with part of the noise component eliminated, which is equivalent to improving the signal-to-noise ratio of the received signal;
step four: performing second-stage adaptive filtering, wherein the reference signal is a noise reduction received signal after the first-stage adaptive filtering, the input signal is an original transmitting signal, and adaptive step length, filter parameters and the like can be selected again according to the amplitude of the input signal;
step five: by means of the second stage adaptive filtering, the channel can be estimated adaptively, i.e. the output signal y of the second stage adaptive filtering2(n) is the corrected reference signal;
step six: and performing copy correlation on the noise-reduction receiving signal obtained in the third step and the corrected reference signal obtained in the fifth step to obtain the output of the double-adaptive copy correlator.
The adaptive algorithm adopts LMS and RLS.
The invention has the beneficial effects that:
1. the method is applied to active sonar signal processing, utilizes a double-adaptive technology to perform adaptive noise elimination on a received signal to improve the signal-to-noise ratio of the received signal, and then adaptively corrects a reference signal on the basis of a noise elimination signal to further improve the performance of a copy correlator, thereby having important significance for improving the performance of the copy correlator in a complex environment.
2. The invention only changes the input signal and the reference signal, can repeatedly utilize the self-adaptive technology and is simple and convenient to realize; the self-adaptive noise cancellation is firstly carried out on the received signal to improve the signal-to-noise ratio of the received signal, and then the self-adaptive correction is carried out on the reference signal on the basis of the noise cancellation signal, so that the performance of the replica correlator can be further improved.
Drawings
FIG. 1 is a flow chart of the operation of the present invention.
Fig. 2 is a diagram of a dual adaptive architecture of the present invention.
Fig. 3 is a diagram of the impulse response spectrum of the channel of the present invention.
FIG. 4 is a graph comparing the performance of different algorithms at a signal-to-noise ratio of 0dB according to the present invention.
FIG. 5 is a graph comparing the performance of different algorithms at-20 dB signal-to-noise ratio according to the present invention.
Detailed Description
The invention will be described in detail below with reference to the following drawings:
example (b): as shown in the attached drawings, the double adaptive copy correlator method mainly comprises the following steps:
the method comprises the following steps: selecting as input z for the first stage adaptation a noise signal that is highly correlated with noise in the received signal1(n)；
Step two: using the received signal as a first-stage adaptive reference input d1(n), performing a first-stage adaptive algorithm, wherein the adaptive algorithm can adopt LMS, RLS and the like, parameters such as adaptive step length, filter order and the like are selected according to the amplitude of the input signal to obtain the output of
Figure RE-GDA0001950493000000021
Step three: the residual signal of the first stage adaptive filtering is e1(n)＝d1(n)-y1(n) using the residual signal as a reference signal d adaptive to the next stage2(n)＝e1(n), namely, the output signal of the first stage adaptive filtering is the estimation of the noise component in the received signal, and then the received signal with part of the noise component removed can be obtained by subtracting the output signal from the reference signal, which is equivalent to improving the signal-to-noise ratio of the received signal;
step four: performing second-stage adaptive filtering, wherein the reference signal is a noise reduction received signal after the first-stage adaptive filtering, the input signal is an original transmitting signal, and adaptive step length, filter parameters and the like can be selected again according to the amplitude of the input signal;
step five: by means of the second stage adaptive filtering, the channel can be estimated adaptively, i.e. the output signal y of the second stage adaptive filtering2(n) is the corrected reference signal;
step six: and performing copy correlation on the noise-reduction receiving signal obtained in the third step and the corrected reference signal obtained in the fifth step to obtain the output of the double-adaptive copy correlator.
The specific implementation process of the invention is as follows:
active sonar signal simulation:
the simulation conditions were as follows: the transmitting signal s (T) is a chirp signal, the bandwidth B is 500Hz, the frequency range is 1000-. In order to simulate a complex and variable actual ocean channel, ray acoustic channel software is used for simulating a channel, the sound source distance is 20km, the emission depth is 50m, the receiving depth is 7m, and the sound velocity gradient is a negative sound velocity gradient, so that channel impact response h (t) is obtained, as shown in figure 3. The echo signal after propagation in the channel is the convolution s of the original transmitting signal and the channel response1(t) s (t) h (t), embedding the echo signal in a white gaussian noise with a certain signal-to-noise ratio and a time duration of t 1.5s as a received signal r (t) s1(t)+n(t)。
First stage adaptive filtering:
selecting a noise signal highly correlated with background noise in the received signal as the input signal z for the first stage of adaptive filtering1(t) using the received signal r (t) as the reference signal d for the first stage of adaptive filtering1(t) filtering by using adaptive algorithms such as LMS, RLS and the like, taking the LMS algorithm as an example, the filtering is performed by
Figure RE-GDA0001950493000000031
e1(n)＝d1(n)-y1(n)
w1(n+1)＝w1(n)+2μe1(n)z1(n)
Where μ is a step size parameter that controls stability and convergence rate, and may be selected based on the input signal power.
Output signal y obtained by first-stage adaptive filtering1(n) is an estimate of the noise signal, then e1(n) is the adaptive noise cancelled received signal, which is used as the next stage adaptive reference signal, i.e. d2(n)＝e1(n) improving the signal-to-noise ratio of the received signal by adaptive noise cancellation.
Second stage adaptive filtering:
the input signal of the second stage of adaptive filtering is the original transmitted signal, z2(n) s (n), the reference signal is the noise-reduced received signal after the first stage of adaptive filtering, the adaptive filtering process is repeated, and the filter weight coefficients can adaptively extract the information of the channel, so that the output signal y2(n) match the echo signal, i.e. can be regarded as a modified reference signal.
Double adaptive copy correlation:
and copying and correlating the noise-reduced received signal obtained by the first stage of self-adaptation and the modified reference signal obtained by the second stage of self-adaptation to obtain the output of the double-self-adaptation copying correlator.
The performance of the dual adaptive copy correlator was simulated and compared with the conventional copy correlator and the adaptive correlator, and the performance comparisons of the algorithms at signal-to-noise ratios of 0dB, -20dB are shown in fig. 4 and 5, respectively, where MF represents the conventional copy correlator, AMF represents the adaptive copy correlator, and DAMF represents the dual adaptive copy correlator. It can be seen from the figure that the output of the replica correlator shows multiple peaks due to channel influence, and the adaptive correlator and the dual adaptive correlator both have a single peak. The peak value of the dual adaptive replica-correlator is more pronounced than the adaptive correlator for the same signal-to-noise ratio, and both are more pronounced than the conventional replica-correlator. When the signal-to-noise ratio drops to-20 dB, the conventional replica correlator does not see a significant peak, and the dual adaptive replica correlator still has the most significant output peak.
It should be understood that equivalent substitutions and changes to the technical solution and the inventive concept of the present invention should be made by those skilled in the art to the protection scope of the appended claims.

Claims (3)

1. A dual adaptive replica correlator method, characterized by: the method mainly comprises the following steps: selecting a noise signal highly correlated with background noise in a received signal as an input signal of a first-level self-adaptive filtering, taking the received signal as a first-level self-adaptive reference input, performing a first-level self-adaptive algorithm, taking a residual signal of the first-level self-adaptive filtering as a reference signal of a second-level self-adaptive filtering, taking the input signal as an original transmitting signal, performing a second-level self-adaptive filtering, and finally performing copy correlation on a noise-reduced received signal obtained by the first-level self-adaptive filtering and a modified reference signal obtained by the second-level self-adaptive filtering to obtain the output of a double-adaptive copy correlator.
2. The dual adaptive copy correlator method of claim 1, wherein: the method specifically comprises the following steps:
the method comprises the following steps: selecting as input z for the first stage adaptation a noise signal that is highly correlated with noise in the received signal1(n)；
Step two: using the received signal as a first-stage adaptive reference input d1(n) performing a first-stage adaptive algorithm, wherein adaptive step length and filter order parameters are selected according to the amplitude of the input signal to obtain an output of
Figure FDA0001784775190000011
Step three: the residual signal of the first stage adaptive filtering is e1(n)＝d1(n)-y1(n) using the residual signal as a reference signal for next stage adaptation, i.e. d2(n)＝e1(n), if the output signal of the first stage adaptive filtering is the estimation of the noise component in the received signal, the reference signal is used to subtract the output signal to obtain the received signal with part of the noise component eliminated, which is equivalent to improving the signal-to-noise ratio of the received signal;
step four: performing second-stage adaptive filtering, wherein the reference signal is a noise reduction received signal after the first-stage adaptive filtering, the input signal is an original transmitting signal, and the adaptive step length and the filter parameter can be reselected according to the amplitude of the input signal;
step five: by means of the second stage adaptive filtering, the channel can be estimated adaptively, i.e. the output signal y of the second stage adaptive filtering2(n) is the corrected reference signal;
step six: and performing copy correlation on the noise-reduction receiving signal obtained in the third step and the corrected reference signal obtained in the fifth step to obtain the output of the double-adaptive copy correlator.
3. The dual adaptive copy correlator method of claim 1 or 2, wherein: the adaptive algorithm adopts LMS and RLS.
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Publication number Priority date Publication date Assignee Title
US4355368A (en) * 1980-10-06 1982-10-19 The United States Of America As Represented By The Secretary Of The Navy Adaptive correlator
CN105871475A (en) * 2016-05-25 2016-08-17 哈尔滨工程大学 Whale-sound-imitating covert underwater sound communication method based on self-adaptive interference cancellation

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