CN109031311B - Bistatic large-scale diversity angle active detection method based on time sliding window processing - Google Patents

Bistatic large-scale diversity angle active detection method based on time sliding window processing Download PDF

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CN109031311B
CN109031311B CN201810519280.5A CN201810519280A CN109031311B CN 109031311 B CN109031311 B CN 109031311B CN 201810519280 A CN201810519280 A CN 201810519280A CN 109031311 B CN109031311 B CN 109031311B
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bistatic
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CN109031311A (en
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雷波
杨益新
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Northwestern Polytechnical 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
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems

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Abstract

The invention relates to a bistatic wide-angle active detection method based on time sliding window processing, which adopts a time window sliding processing method to carry out direct wave suppression processing on signals in a time window and extract target scattered signals, estimates signal time delay and Doppler information, realizes bistatic wide-angle active detection on a target, and effectively avoids the problem of target detection alarm omission caused by signal multipath propagation. The invention obtains obvious effect in application, and compared with the prior art, the invention has the advantages that: through the bistatic wide-angle active detection method based on time sliding window processing, direct waves in bistatic wide-angle detection are effectively suppressed, Doppler and time delay parameter information of a target scattering signal is obtained, and a wide-angle blind area of conventional bistatic detection is overcome.

Description

Bistatic large-scale diversity angle active detection method based on time sliding window processing
Technical Field
The invention belongs to an active detection method for an underwater target under a bistatic large-scale angle, and relates to a bistatic large-scale angle active detection method based on time sliding window processing.
Background
When a target approaches a receiving and transmitting connecting line of the double-base sonar, a large partial angle of bistatic detection is formed, a target scattering signal and a direct wave signal almost reach a receiving unit at the same time, and the direct wave signal is higher than the scattering signal by more than 20dB under the general condition, so that the target scattering signal is submerged by the direct wave, and a detection blind area of the conventional double-base sonar is formed. From the specific processing technology, the suppression of direct wave intensity interference is still the main idea for realizing the active detection of underwater targets under the bistatic wide-angle. At present, for the detection of bistatic blind areas, on one hand, the adaptive cancellation technology is used for restraining direct waves. On the other hand, the transmitted waveform is designed, and the signals in a complex form are adopted to improve the resolution capability of the signals in the time domain and the Doppler domain. But the effect is not obvious, and a large blind area still exists in bistatic large-scale angular positioning detection. In bistatic large-diversity angle detection, direct wave interference causes the increase of the false-alarm probability of target detection.
Disclosure of Invention
Technical problem to be solved
In order to avoid the defects of the prior art, the invention provides a bistatic wide-angle active detection method based on time sliding window processing, which is used for detecting a target when the target passes through a coverage area of the bistatic wide-angle.
Technical scheme
A bistatic macro-diversity active detection method based on time sliding window processing comprises the following processing steps:
step 1: intercepting the received signal by adopting a time window with the same length as the transmitted signal, wherein the signal is expressed as follows:
r[n]＝r(nts),n＝0,1,L,mrQL-1
wherein: n is a sampling point number; m isrThe number of sampling points contained in one carrier frequency period; l is the number of code elements of the transmitted signal; q is the number of the carrier frequency waveforms filled in each code element; t is tsInterval time of sampling points;
the transmitting signal is a pseudo-random sequence phase modulation signal continuously and circularly transmitted by a sound source;
the received signal is a signal received by adopting a single hydrophone or a hydrophone array beam;
step 2: will signal r [ n ]]Is divided into mrQ sequences of length L
Figure GDA0003465621530000021
Wherein: q represents the number of sampling points in each transmitted symbol, m represents the number of transmitted symbols
And step 3: for each sequence zqTransformed as follows to obtain an output sequence sq：
Figure GDA0003465621530000022
Wherein: b denotes a transmitted sequence symbol, k denotes a shift to the symbol,
Figure GDA0003465621530000023
and 4, step 4: will sqIntegrated into a new output sequence sr：
Figure GDA0003465621530000024
Step 5, setting a zero setting threshold: a sequence srThe values with the median value larger than the threshold are all forced to be zero, and the new sequence is recorded as
Figure GDA0003465621530000025
Step 6: will be sequenced
Figure GDA0003465621530000026
Is divided into m againrQ sequences of length L:
Figure GDA0003465621530000027
and 7: to pair
Figure GDA0003465621530000028
The sequence is transformed as follows
Figure GDA0003465621530000029
And 8: handlebar sequence
Figure GDA00034656215300000210
Re-integration into one signal sequence:
Figure GDA00034656215300000211
and step 9: using the transmitted signal as a copy signal, for signals
Figure GDA0003465621530000031
Performing pulse compression, and if a peak value exists on the ambiguity surface, taking the Doppler frequency shift and time delay information as the Doppler frequency shift and time delay of the target scattering signal;
and (4) sliding the time window, and repeating the steps 2-9 on the next section of signal until the whole received signal is processed.
The carrier frequency of the signal is 500 Hz-20 kHz, the period T of the signal is 0.01 s-20 s, the number L of code elements is 63-8191, and the filling period Q is 1-20.
The received signal is the output signal of a single hydrophone or the output signal of the underwater acoustic sensor array beam.
Advantageous effects
The invention provides a bistatic wide-angle active detection method based on time sliding window processing.
The invention obtains obvious effect in application, and compared with the prior art, the invention has the advantages that: through the bistatic wide-angle active detection method based on time sliding window processing, direct waves in bistatic wide-angle detection are effectively suppressed, Doppler and time delay parameter information of a target scattering signal is obtained, and a wide-angle blind area of conventional bistatic detection is overcome.
Drawings
FIG. 1: forward scatter detection scheme
FIG. 2: time window sliding processing of received signals
FIG. 3: and comparing the detection results of the large separation angle before and after processing. (a) After the direct wave is inhibited; (b) without direct wave suppression
FIG. 4: the target scatter signal obscures the surface section. (a) A Doppler domain; (b) time delay domain
Detailed Description
The invention will now be further described with reference to the following examples and drawings:
the method for extracting the target scattering signal under the bistatic differential angle based on time sliding window processing is characterized by comprising the following steps of: the pseudo-random sequence phase modulation signal is continuously and circularly transmitted by a sound source, and a single hydrophone or a hydrophone array is adopted for receiving. When a target approaches a receiving-transmitting connecting line consisting of a transmitting sound source and a receiving hydrophone, a time sliding window is adopted to intercept signals, direct wave signals are restrained, and time delay and Doppler information of scattered signals are extracted. The number of code elements of the transmitted signal is recorded as L, each code element is filled with Q carrier frequency waveforms, and the number of sampling points contained in one carrier frequency period is recorded as mrThe received signal is processed as follows:
in a first step, the received signal is truncated by a time window of equal length to the transmitted signal, denoted as
r[n]＝r(nts),(n＝0,1,…,mrQL-1)
Second, make r [ n ]]Is divided into mrQ sequences of length L
Figure GDA0003465621530000041
Third step, for each sequence zqTransformed as follows to obtain an output sequence sq
Figure GDA0003465621530000042
The fourth step of mixing sqIntegrated into a new output sequence sr
Figure GDA0003465621530000043
Fifthly, setting a zero threshold and setting the sequence srThe values with the median value larger than the threshold are all forced to be zero, and the new sequence is recorded as
Figure GDA0003465621530000044
The sixth step, the sequence
Figure GDA0003465621530000045
Is divided into m againrQ sequences of length L
Figure GDA0003465621530000046
The seventh step is to
Figure GDA0003465621530000047
Sequence conversion back to the received signal domain
Figure GDA0003465621530000048
Eighth step of sequencing
Figure GDA0003465621530000049
Integrated into a signal sequence
Figure GDA0003465621530000051
A ninth step of comparing the signals with the transmission signal as a copy signal
Figure GDA0003465621530000052
And (4) performing pulse compression, wherein if a peak exists on the ambiguity surface, the Doppler frequency shift and time delay information of the ambiguity surface are the Doppler frequency shift and time delay of the target scattering signal.
And step ten, sliding a time window, and repeating the step two to step nine for the next section of signals until the whole received signal processing is finished.
Simulation verification tests were conducted in a pool laboratory. The geometric layout of the sound source, the target and the receiving end is shown in fig. 1, the transmitting-receiving distance L between the sound source transmitting end and the receiving end is about 11m, the pool depth H is about 7m, and the movable length D of the target is 5 m. The transmitting sound source adopts a flextensional transducer, is distributed at the depth of 2m underwater, and an omnidirectional receiving hydrophone with the same depth as the sound source is arranged at the position 11m away from the sound source. The target was a hollow round sphere of aluminum with a diameter of about 56 cm. Spherical target distance emitting end Lts6m away from the receiving end Ltr5m, at a speed of about 0.26m/s through the transceiving link. Center frequency f of the transmitted signalcThe pseudo-random phase modulation signal is adopted at 2kHz, the symbol length L is 2047, and the number Q of padding waveforms in the unit symbol duration is 4. The total duration of the generated pseudo-random phase modulated signal is 4.09s, corresponding to a signal frequency resolution of 0.24 Hz.
The received signal is sliding processed using a time window of duration 4.09s, as shown in fig. 2. The signal in the time window is processed according to the method provided by the invention, and the result obtained by pulse compression is shown in fig. 3(a), and it can be seen that a bright spot exists on the fuzzy surface at the position where the doppler shift is 0.3Hz and the time delay is 1 ms. The result without the processing of the present invention is shown in fig. 3(b), and it is obvious that at doppler 0Hz, the direct wave at time delay 0s is so strong as to cover the scattering signal of the target. The comparison shows that after the processing, the target large differential scattering signal is obviously detected.
Further extracting the blurred surface in fig. 3(a) to obtain the cut planes along the doppler domain and the delay domain, as shown in fig. 4, it can be seen that the doppler shift parameter and the delay parameter of the target signal are accurately obtained.

Claims (2)

1. A bistatic macro-diversity angle active detection method based on time sliding window processing is characterized by comprising the following processing steps:
step 1: intercepting the received signal by adopting a time window with the same length as the transmitted signal, wherein the signal is expressed as:
r[n]＝r(nts),n＝0,1,L,mrQL-1
wherein: n is a sampling point number; m isrThe number of sampling points contained in one carrier frequency period; l is the number of code elements of the transmitted signal; q is the number of the carrier frequency waveforms filled in each code element; t is tsInterval time of sampling points;
the transmitting signal is a pseudo-random sequence phase modulation signal continuously and circularly transmitted by a sound source;
the received signal is a signal received by adopting a single hydrophone or a hydrophone array beam;
step 2: will signal r [ n ]]Is divided into mrQ sequences of length L
Figure FDA0003465621520000011
Wherein: q represents the number of sampling points in each transmitted symbol, m represents the number of transmitted symbols
And step 3: for each sequence zqTransformed as follows to obtain an output sequence sq：
Figure FDA0003465621520000012
Wherein: b denotes the transmitted sequence symbol, k denotes the shift to the symbol,
Figure FDA0003465621520000013
and 4, step 4: will s isqIntegrated into a new output sequence sr：
Figure FDA0003465621520000014
Step 5, setting a zero setting threshold: a sequence srThe values with the median value larger than the threshold are all forced to be zero, and the new sequence is recorded as
Figure FDA0003465621520000015
Step 6: will be sequenced
Figure FDA0003465621520000016
Is divided into m againrQ sequences of length L:
Figure FDA0003465621520000017
and 7: to pair
Figure FDA0003465621520000018
The sequence is transformed as follows
Figure FDA0003465621520000021
And step 8: handle sequence
Figure FDA0003465621520000022
Re-integration into one signal sequence:
Figure FDA0003465621520000023
and step 9: using the transmitted signal as a copy signal, for signals
Figure FDA0003465621520000024
Performing pulse compression, and if a peak value exists on the ambiguity surface, taking the Doppler frequency shift and time delay information of the peak value as the Doppler frequency shift and time delay of the target scattering signal;
and (4) sliding the time window, and repeating the steps 2-9 on the next section of signal until the whole received signal is processed.
2. The bistatic macro-diversity active detection method based on time sliding window processing according to claim 1, characterized in that: the carrier frequency of the signal is 500 Hz-20 kHz, the period T of the signal is 0.01 s-20 s, the number L of code elements is 63-8191, and the filling period Q is 1-20.
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