CN108459316B - Echo signal parameter estimation method under multi-path channel - Google Patents

Echo signal parameter estimation method under multi-path channel Download PDF

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CN108459316B
CN108459316B CN201810101748.9A CN201810101748A CN108459316B CN 108459316 B CN108459316 B CN 108459316B CN 201810101748 A CN201810101748 A CN 201810101748A CN 108459316 B CN108459316 B CN 108459316B
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方世良
黄舒夏
韩宁
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Southeast University
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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
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Abstract

The invention discloses an echo signal parameter estimation method under a multi-path channel, which comprises the following steps: (1) designing a copy signal in a matched filter into a transmission signal copy after compression by different Doppler factors; (2) sequentially matching the echo signals under the multi-path channel with the copy signals, and searching the copy signal corresponding to the maximum peak value of the output as the best matching result; (3) and estimating parameters and time domain signals in the path according to the optimal matching result, and subtracting the respective estimated matching result of each path signal from the result under different Doppler factor matching in the parameter estimation of the next path to detect the parameters and the time domain signals in the residual path. The method is more stable, has higher estimation precision, fully utilizes operation resources, and is suitable for various forms of broadband signals.

Description

Echo signal parameter estimation method under multi-path channel
Technical Field
The invention relates to the field of parameter estimation of underwater acoustic echoes, in particular to an echo signal parameter estimation method under a multi-path channel.
Background
The complex time-frequency characteristics of underwater acoustic channels make them one of the most difficult wireless channels to process echo signals. In the underwater acoustic target channel, the relative motion between the target or the sonar causes the doppler effect of the echo signal, and the transmitted signal in most underwater acoustic systems has a broadband characteristic, so the doppler effect at this time cannot be reduced to the shift of the signal frequency, but the compression or broadening of the signal pulse width caused by the doppler coefficient.
Meanwhile, the reflected signals of the underwater acoustic target may have different transmission paths, so that the received echoes are the superposition of a plurality of channel component signals, and the amplitude attenuation, arrival time and compression coefficient of the signals are different. At present, most of multi-path underwater acoustic signal processing methods only consider the Doppler coefficient of the signal component with the largest energy in multi-path signals, ignore the deviation of the Doppler coefficients in other paths, and have the factors of large computation amount, large influence of parameter estimation between adjacent signals and the like, so that a novel and efficient channel parameter estimation method is urgently developed.
In an active sonar signal processing system, matched filtering is a common signal detection and estimation method, copy signals in a matched filter are changed and correlation operation is carried out, and then the copy signal corresponding to the maximum value of a peak value in an output result is the signal form closest to the main components in a received signal. The conventional matched filtering algorithm has a plurality of matched peaks with different amplitudes when detecting multipath signals, which is not favorable for accurate estimation of target parameters. Meanwhile, the matching peak side lobe of the signal component with higher energy may mask the matching result of the adjacent signal component, so that the method needs to be improved and utilized to effectively separate and estimate the parameters of each component of the multipath signal.
Disclosure of Invention
The purpose of the invention is as follows: the invention provides a method for estimating the echo time-shifting frequency structure of an active sonar target under a multi-path channel, aiming at the problems in the prior art, the method allows a transmitted signal to be a broadband signal in different forms, the estimated multi-component signal parameters comprise an amplitude attenuation coefficient and a time delay factor, namely a Doppler coefficient, and the method has certain robustness under the condition of different time-bandwidth products.
The technical scheme is as follows: the echo signal parameter estimation method under the multi-path channel comprises the following steps:
(1) designing a copy signal in a matched filter into a transmission signal copy after compression by different Doppler factors;
(2) sequentially matching the echo signals under the multi-path channel with the copy signals, and searching the copy signal corresponding to the maximum peak value of the output as the best matching result;
(3) and estimating parameters and time domain signals in the path according to the optimal matching result, and subtracting the respective estimated matching result of each path signal from the result under different Doppler factor matching in the parameter estimation of the next path to detect the parameters and the time domain signals in the residual path.
Further, the step (1) specifically comprises:
the copy signal in the matched filter is designed to be:
Figure BDA0001566542660000021
wherein u [ η ]m·n]For transmitting signals, T is the signal pulse width, FS is the sampling rate, ηm＝(c+vm)/(c-vm) Is the Doppler factor, c is the speed of sound propagation in water, vmIs the velocity and v to be verifiedm＝vmin+m·v，[vmin,vmax]Is the radial speed range of the object to be measured, and the speed is positive when the phase-separation motion is carried out,vis the velocity resolution.
Further, the step (2) specifically comprises:
(2-1) respectively carrying out matched filtering processing on the echo signals and the copy signals under the multipath channel to obtain a matched output result { ym[n]|n∈[0,WL],m＝0,1,...,(vmax-vmin)/vW L, where W L is the processing echo length;
(2-2) assigning the copy signal corresponding to the maximum peak value of the matching output result to sopt1[n]The matching result corresponding to the copy signal is the best matching result.
Further, the step (3) specifically comprises:
(3-1) setting i ═ 1;
(3-2) if i is 1, performing (3-6), if i ∈ [2, N ], performing (3-3), N being the total number of iterations;
(3-3) calculating time domain signal estimation value of i-1 path
Figure BDA0001566542660000022
At each Doppler coefficient ηmMatch output under compression y'm,i[n]|m＝0,1,...,(vmax-vmin)/v}；
(3-4) outputting the matching result ym[n]Subtracting the matching output of the determined i-1 estimated signal components under the compression of the corresponding Doppler coefficient to obtain a residual matching result:
Figure BDA0001566542660000023
(3-5) matching results from the remainder
Figure BDA0001566542660000024
Assigning the copy signal having the largest peak to the result
Figure BDA0001566542660000025
Figure BDA0001566542660000026
The corresponding residual matching result is the best matching result;
(3-6) extracting the amplitude, time delay and Doppler coefficient parameter group of the echo signal of the ith channel:
Figure BDA0001566542660000027
and recovering the time domain signal estimation value of the ith path based on the coefficient group
Figure BDA0001566542660000028
Figure BDA0001566542660000031
Wherein T is the signal pulse width, FS is the sampling rate,
Figure BDA0001566542660000032
as a result of the best match
Figure BDA0001566542660000033
The maximum value of (a) is,
Figure BDA0001566542660000034
is the time coordinate at the maximum value and,
Figure BDA0001566542660000035
is composed of
Figure BDA0001566542660000036
The doppler compression factor of (a);
(3-7) i is equal to i +1, if i is greater than N, the loop is ended, otherwise, the step (3-2) is returned.
Wherein y 'is calculated in the step (3-3)'m,i[n]And then storing, and directly extracting from the storage area when the storage area is used next time.
Has the advantages that: compared with the prior art, the invention has the following remarkable advantages: compared with the prior art, the method considers the estimation method of three parameters of echo amplitude, time delay and Doppler factor in multi-path channel signal processing, is different from the traditional method that only the Doppler factor in a main component path is considered in signal processing, and allows different path components to have different time delay and amplitude and respective Doppler coefficients. At present, some iterative algorithms for processing multi-path channel signals exist, the estimated previous signal components are subtracted from the total echo for analyzing the signal of the next component, and the algorithm for time domain subtraction can seriously affect the subsequent path parameter estimation when the previous signals have deviation. The matched filtering operation result of each time is stored in a storage and enters the operation of next iteration, thereby saving the operation resource.
Drawings
FIG. 1 is a schematic flow diagram of an embodiment of the present invention;
FIG. 2 is a time domain diagram of a received multi-pass signal containing 4 paths;
FIG. 3 is a graph of the first cycle matching output;
FIG. 4 is a graph of the second cycle matching output;
FIG. 5 is a graph of the output of the third round of matching;
FIG. 6 is a graph of the matching output of the fourth cycle.
Detailed Description
The embodiment provides a method for estimating echo signal parameters under a multi-path channel, as shown in fig. 1, including:
(1) the replica signal in the matched filter is designed as a replica of the transmitted signal after being compressed by different Doppler factors.
Wherein the copy signal in the matched filter is designed to:
Figure BDA0001566542660000037
in the formula, u [ ηm·n]For transmitting signals, T is the signal pulse width, FS is the sampling rate, ηm＝(c+vm)/(c-vm) Is the Doppler factor, c is the speed of sound propagation in water, vmIs the velocity and v to be verifiedm＝vmin+m·v，[vmin,vmax]Is the radial speed range of the object to be measured, and the speed is positive when the phase-separation motion is carried out,vis the velocity resolution.
(2) And sequentially matching the echo signals and the copy signals under the multi-path channel, and searching the copy signal corresponding to the maximum peak value as the best matching result. The method specifically comprises the following steps:
(2-1) respectively carrying out matched filtering processing on the echo signals and the copy signals under the multipath channel to obtain a matched output result { ym[n]|n∈[0,WL],m＝0,1,...,(vmax-vmin)/vW L, where W L is the processing echo length;
(2-2) assigning the copy signal corresponding to the maximum peak value of the matching output result to
Figure BDA0001566542660000041
The matching result corresponding to the copy signal is the best matching result.
(3) And estimating parameters and time domain signals in the path according to the optimal matching result, and subtracting the respective estimated matching result of each path signal from the result under different Doppler factor matching in the parameter estimation of the next path to detect the parameters and the time domain signals in the residual path. The method specifically comprises the following steps:
(3-1) setting i ═ 1;
(3-2) if i is 1, performing (3-6), if i ∈ [2, N ], performing (3-3), N being the total number of iterations;
(3-3) calculating time domain signal estimation value of i-1 path
Figure BDA0001566542660000042
At each Doppler coefficient ηmMatch output under compression y'm,i[n]|m＝0,1,...,(vmax-vmin)/v}；
(3-4) outputting the matching result ym[n]Subtracting the matching output of the determined i-1 estimated signal components under the compression of the corresponding Doppler coefficient to obtain a residual matching result:
Figure BDA0001566542660000043
(3-5) matching results from the remainder
Figure BDA0001566542660000044
Assigning the copy signal having the largest peak to the result
Figure BDA0001566542660000045
Figure BDA0001566542660000046
The corresponding residual matching result is the best matching result;
(3-6) extracting the amplitude, time delay and Doppler coefficient parameter group of the echo signal of the ith channel:
Figure BDA0001566542660000047
and recovering the time domain signal estimation value of the ith path based on the coefficient group
Figure BDA0001566542660000048
Figure BDA0001566542660000049
Wherein T is the signal pulse width and FS is the samplingThe sample rate of the sample is measured,
Figure BDA00015665426600000410
as a result of the best match
Figure BDA00015665426600000411
The maximum value of (a) is,
Figure BDA00015665426600000412
is the time coordinate at the maximum value and,
Figure BDA00015665426600000413
is composed of
Figure BDA00015665426600000414
The doppler compression factor of (a);
(3-7) i is equal to i +1, if i is greater than N, the loop is ended, otherwise, the step (3-2) is returned.
Wherein y 'is calculated in the step (3-3)'m,i[n]And then storing, and directly extracting from the storage area when the storage area is used next time.
The following simulation verification of the present embodiment is performed by using MAT L AB software to set parameters of transmission chirp signal (L FM) with pulse width T of 2s and frequency range fL＝1200Hz，fH1800Hz, 600Hz, 1500m/s sound velocity c, 6000Hz sampling rate FS, 5dB signal-to-noise ratio, and 4 paths in the simulation with 5 · FS. processing window length W L, the target echo is:
Figure BDA0001566542660000051
wherein the content of the first and second substances,
Figure BDA0001566542660000052
the time domain diagram of the echo is shown in fig. 2, and the theoretical set values of the signal component parameters in 4 channels are as follows:
i Ai τi/FS η i
1 1 2.0002 1.0067
2 0.8725 2.0317 1.0066
3 0.5937 2.0108 1.0067
4 0.5037 2.0722 1.0065
setting the radial velocity range of the target to [ -10,10]m/s, resolutionv0.2m/s, then v m1,2, 101, 0.2, m ═ 10+ m. Designing copy signals s in corresponding matched filters respectivelym1,2, 101. Respectively carrying out matched filtering processing on the echo signal and each copy signal to obtain a matched output result ym[n]，m＝1,2,...,101，n∈[0,WL]Taking the copy signal having the largest peak as
Figure BDA0001566542660000053
The matching output at this time is the best matching result. And entering a loop algorithm, wherein the loop time i is 1.
Extracting the amplitude, time delay and Doppler coefficient parameter group of the 1 st path signal:
Figure BDA0001566542660000054
recovering the time domain signal of the 1 st component
Figure BDA0001566542660000055
And entering loop iteration to finally obtain 4 groups of parameters:
Figure BDA0001566542660000056
FIGS. 3 to 6 are the matched filtering results in the 1 st to 4 th loop algorithms, respectively, each graph is obtained by subtracting the component with the maximum energy of the current signal from the previous graph, and the signals of each path are sequentially searched in an iterative manner and the signal parameters are extracted, so that
Figure BDA0001566542660000061
Calculating the estimation error, and obtaining an error result table as follows:
Figure BDA0001566542660000062
the conclusion can be drawn from the experimental data processing result, and the multi-path signal parameter estimation method of the method can accurately estimate the specific parameters of different propagation paths under the condition of limited time bandwidth product.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims (4)

1. A method for estimating echo signal parameters under a multi-path channel is characterized by comprising the following steps:
(1) designing a copy signal in a matched filter into a transmission signal copy after compression by different Doppler factors;
(2) sequentially matching the echo signals under the multi-path channel with the copy signals, and searching the copy signal corresponding to the maximum peak value of the output as the best matching result;
(3) estimating parameters and time domain signals in the path according to the optimal matching result, and in the parameter estimation of the next path, subtracting the respective matching result of each path signal estimated previously from the result under the matching of different Doppler factors to detect the parameters and the time domain signals in the remaining path, wherein the step specifically comprises the following steps:
(3-1) setting i ═ 1;
(3-2) if i is 1, performing (3-6), if i ∈ [2, N ], performing (3-3), N being the total number of iterations;
(3-3) calculating time domain signal estimation value of i-1 path
Figure FDA0002479739890000011
At each Doppler coefficient ηmMatch output under compression y'm,i[n]|m＝0,1,...,(vmax-vmin)/v}，[vmin,vmax]Is the radial speed range of the object to be measured, and the speed is positive when the phase-separation motion is carried out,vis the velocity resolution;
(3-4) outputting the matching result ym[n]Subtracting the matching output of the determined i-1 estimated signal components under the compression of the corresponding Doppler coefficient to obtain a residual matching result:
Figure FDA0002479739890000012
(3-5) matching results from the remainder
Figure FDA0002479739890000013
Assigning the copy signal having the largest peak to the result
Figure FDA0002479739890000014
Figure FDA0002479739890000015
The corresponding residual matching result is the best matching result;
(3-6) extracting the amplitude, time delay and Doppler coefficient parameter group of the echo signal of the ith channel:
Figure FDA0002479739890000016
and recovering the time domain signal estimation value of the ith path based on the coefficient group
Figure FDA0002479739890000017
Figure FDA0002479739890000018
Wherein T is the signal pulse width, FS is the sampling rate,
Figure FDA0002479739890000019
as a result of the best match
Figure FDA00024797398900000110
The maximum value of (a) is,
Figure FDA00024797398900000111
is the time coordinate at the maximum value and,
Figure FDA00024797398900000112
is composed of
Figure FDA00024797398900000113
The doppler compression factor of (a);
(3-7) i is equal to i +1, if i is greater than N, the loop is ended, otherwise, the step (3-2) is returned.
2. The method according to claim 1, wherein the method further comprises: the step (1) specifically comprises the following steps:
the copy signal in the matched filter is designed to be:
Figure FDA0002479739890000021
wherein u [ η ]m·n]For transmitting signals, T is the signal pulse width, FS is the sampling rate, ηm＝(c+vm)/(c-vm) Is the Doppler factor, c is the speed of sound propagation in water, vmIs the velocity and v to be verifiedm＝vmin+m·v，[vmin,vmax]Is the radial speed range of the object to be measured, and the speed is positive when the phase-separation motion is carried out,vis the velocity resolution.
3. The method according to claim 1, wherein the method further comprises: the step (2) specifically comprises the following steps:
(2-1) respectively carrying out matched filtering processing on the echo signals and the copy signals under the multipath channel to obtain a matched output result { ym[n]|n∈[0,WL],m＝0,1,...,(vmax-vmin)/vW L, where W L is the processing echo length;
(2-2) assigning the copy signal corresponding to the maximum peak value of the matching output result to
Figure FDA0002479739890000022
The matching result corresponding to the copy signal is the best matching result.
4. The method according to claim 3, wherein the method further comprises: y 'is calculated in the step (3-3)'m,i[n]And then storing, and directly extracting from the storage area when the storage area is used next time.
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