CN102183741A - Method for realizing high frame rate unambiguous positioning in long baseline asynchronous acoustic positioning system - Google Patents

Abstract

The invention provides a method for realizing high frame rate unambiguous positioning in a long baseline asynchronous acoustic positioning system; a signal is in a combined pulse string form at a signal emitting end; a CW signal and a LFM signal are alternatively used by the combined pulse string so as to reduce interference among pulses without reducing the frame rate since the frequencies of the sequent pulses are different; a processing method of the received signal comprises the following steps: performing the detection, time delay and frequency estimation of a CW pulse and a LFM pulse respectively by using a parallel multi-channel self-adaptive wave trap set and a parallel copy correlator set at a signal receiving end. The frame rate can be improved to 0.1s order by using the combined pulse string signal form so that the positioning system can be greatly improved in comparison with the present mature technology at home and abroad in terms of the track measurement frame rate, the positioning precision, the use reliability and convenience. The corresponding signal processing method can be used for effectively inhibiting the channel string leakage and reducing the influence of the Doppler effect.

Description

Realize that at long baseline asynchronous acoustic positioning system high frame per second do not have the method for fuzzy location

Technical field

What the present invention relates to is a kind of acoustic positioning technique, is specifically related to a kind of high frame per second hydrolocation of distributed buoy array method of non-cooperation high-speed moving object track under water.

Background technology

Be subjected to that underwater acoustic channel narrow bandwidth, signal velocity are slow, the restriction of many unfavorable factors such as many ways, interface and sound ray bending, it is much more difficult than land and aerial target that submarine target is carried out high-precision location navigation.And spatially distributed buoy array acoustic positioning system provides the necessary technology means for submarine target high-precision three-dimensional location.

For cooperative target under water, existing acoustic positioning system adopts synchronous working mode ([1] THOMSON D more, ELSONS.New generation acoustic positioning systems.Oceans ' 02MTS/IEEE, 2002,3:1312-1318), also promptly before each the measurement, the clock of tested sound source (being installed on the moving target) and receiving system need carry out synchronously to the time.Though synchronously to the time can reach very high precision, synchro system is all higher to the stability requirement of sound source and receiving system clock.Limited clock stability not only can cause clock jitter accumulation, also easily because of the external world at random high power pulse disturb and cause clock disturbance deviation, and then influence system accuracy.And the asynchronous working mode do not require sound source and receiving system accurately to the time, in battle array, can reach bearing accuracy ([2] the KOZICK R J that compares favourably with synchro system, SADLER B M.Source localization withdistributed sensor arrays and partial spatial coherence.IEEE Transactions on SignalProcessing, 2004,52 (3): 601-616), thereby the scope of application is more extensive.

For the submarine target of doing high speed, compound movement, positioning system must guarantee that sufficiently high track sampling rate could correct its track of description.But be subjected to range ambiguity ([3] Liang Guolong, Yang Chun, Wang Yan. the applied analysis of the anti-range ambiguity technology of software in the asynchronous underwater acoustic tracking location. applied acoustics, 2005,24 (6): restriction 359-363), its track sampling rate of common positioning system all lower (at second-time), this has limited the tracking power to high-speed target.Will long baseline, two kinds of localization methods combinations of ultra-short baseline ([4] QUAZI A H.An overview on the time delay estimation in active and passive systemsfor target localization.IEEE Trans Acoust Speech SignalProcess, 1981,29 (3): 527-533), can under the prerequisite that does not produce range ambiguity, suitably improve and measure frame per second, but the structure of its single buoy primitive is complicated, and the sea lays reclaims inconvenience.

Summary of the invention

The object of the present invention is to provide a kind of long baseline asynchronous acoustic positioning system that is applied to, can be under the prerequisite that does not produce range ambiguity, that realizes high frame per second track sampling realizes that at long baseline asynchronous acoustic positioning system high frame per second do not have the method for fuzzy location.

The object of the present invention is achieved like this:

At the signal transmitting terminal, signal form is the assembled pulse string; Described assembled pulse string intersects and uses CW and LFM signal, and the frequency difference of front and back pulse, reduces inter-pulse interference under the condition that does not reduce frame per second;

At signal receiving end, disposal route to the received signal is respectively applied for detection, time delay and the Frequency Estimation of CW pulse and LFM pulse for adopting parallel multi-channel adaptive notch filter group and parallel copy correlator bank.

Core technology content of the present invention is the Waveform Design and the corresponding signal process method of signal.

Signal waveform adopts the assembled pulse string, intersects to use CW and LFM signal, and dissimilar pulse band non-overlapping copies, or band overlapping but chirp rate polarity is opposite.N pulse arranged in the train of impulses, establish Pi (i=0,1 ..., N) be the pulse pattern sequence number.P0 is the CW pulse, P1, P2 ... PN is arrowband LFM pulse.The Doppler shift that utilizes the real-time measurement target high-speed motion of pulse P0 to produce is used for adjusting in real time the reference signal of making relevant treatment with the LFM pulse.Pulse P1, P2 be as pulse subsequence odd even identification code, is used for the spacetime correlation that concentric float intermittent gauging not gets pulse signal information.Can measure frame per second to the 0.1s magnitude not producing range ambiguity and do not increase to improve under the prerequisite of system complexity.

For this kind signal form, adopt parallel multi-channel adaptive notch filter group and parallel copy correlator bank to be respectively applied for the signal processing method of detection, time delay and the Frequency Estimation of CW pulse and LFM pulse, can effectively suppress the influence that the interchannel string leaks and reduce Doppler effect.

In addition, when velocity of sound section such as non-, adopt the means of sound ray correction can obtain more high accuracy depth positioning result.

Description of drawings

Fig. 1 is a buoy array asynchronous underwater acoustic positioning system work situation map;

Fig. 2 is that buoy array asynchronous underwater acoustic positioning system is measured the battle array pie graph;

Fig. 3 is several optional sequential structure of assembled pulse string;

Fig. 4 is the signal processing method block diagram;

Fig. 5 is a parallel multi-channel adaptive notch filter group;

Fig. 6 is parallel copy correlator bank.

Embodiment

Below in conjunction with the drawings and specific embodiments this paper is further described in detail:

1. the formation of positioning system

Shown in Figure 2 as Fig. 1, a basic positioning system is made up of 4 wireless remote control hydrolocation buoys, comprising 2 vertical two nautical receiving set buoys and 2 single nautical receiving set buoys, constitutes the measurement in space battle array of one 6 array element.Utilize between each buoy GPS synchronously to the time, buoy receiver receives from the pulse signal of target sound source emission with asynchronous system, notes the moment that pulse front edge arrives after detecting signal.The terrestrial coordinate position of GPS The real time measure buoy is sent to parameters such as buoy position, signal transmission delay surveying vessel in real time by means of the wireless communication chain and shows the control platform and position and resolve.A basic formation can be carried out the real-time three-dimensional tracking and monitoring to the target in 3km * 3km * 300m scope, increases measurement range as need, can realize the system extension facility by increasing cascade buoy number.

2. signal waveform: assembled pulse string

In underwater acoustic channel, up-and-down boundary can cause the time delay expansion of many ways, and the time delay expansion can reach more than the 300-400ms under the shallow water channel.Interpulse phase mutual interference before and after the time delay expansion of many ways can cause increases the difficulty that detects and estimate.Can reduce this interference though increase pulse distance, system's frame per second is reduced.

A kind of assembled pulse string that adopts among the present invention, intersection is used the pulse signal of different frequency range, and the frequency difference of front and back pulse, can reduce inter-pulse interference under the condition that does not reduce frame per second like this.

Consider that the underwater acoustic channel available band is narrower, the assembled pulse string is designed to form assembled pulse string repetition period 2s by 12 pulses, maximum 7 types of pulse combined.Dissimilar pulse band non-overlapping copies, or band overlapping but chirp rate polarity is opposite.If Pi (i=0,1 ..., 6) and for pulse pattern sequence number .P0 is the CW pulse, P1, P2 ... P6 is arrowband LFM pulse.The Doppler shift that utilizes the real-time measurement target high-speed motion of pulse P0 to produce is so that adjust the reference signal of making relevant treatment with the LFM pulse in real time.Pulse P1, P2 be as pulse subsequence odd even identification code, so that the concentric float intermittent gauging does not get the spacetime correlation of pulse signal information.

The sequential structure of train of impulses can be chosen 3 kinds of structures as shown in Figure 3 respectively.These sequential structures all can improve frame per second 12 times, and the track sampling period is reduced to 0.166ms.And the required independent channel number minimum (only needing 5) of structure 1 wherein, but anti-multi-path capability is poor slightly than structure 2 and structure 3.More abundant and many ways time delay is expanded when serious when channel width, the pulse train structure can be changed to be structure 2 or structure 3, wherein many ways expansion that structure 3 can anti-second-time.

3. signal processing algorithm

For the signal waveform of mentioning in 2, the corresponding signal process method as shown in Figure 4.For the CW signal, the first step is to use parallel multi-channel adaptive notch filter group to handle the signal that receives, and second step was to use instantaneous frequency variance detecting device to be used for detection, time delay and the Frequency Estimation of CW pulse.For the LFM signal, this process also comprises two steps: the first step is to use the copy correlator bank to handle the signal that receives, and second step was LFM pulse and the due in thereof that search exists in the output of copy correlator bank.Simultaneously, the reference sample of copy correlator is revised in real time according to the CW pulsed frequency side-play amount that sef-adapting filter records, and can avoid because Doppler effect makes the LFM due in of measurement deviation occur.

(1) detection of CW pulse, time delay and Frequency Estimation

Say in principle, only utilize the single pass adaptive notch filter can be Single Frequency C W pulse signal P ₀Detect and parameter estimation.But LFM pulse signal P ₁, P ₂... P ₆Though with P ₀Frequency band is not overlapping, and when the LFM signal intensity was big, the string of The Sideband Spectrum component leaked the envelope big rise and fall that still can make notch filter output, causes false-alarm easily.The single channel adaptive notch filter is set up a plurality of trap passages, the centre frequency of the corresponding several LFM pulse signals of difference, constitute parallel multi-channel adaptive notch filter group, then can remove the interference that the LFM pulse causes, avoid envelope fluctuation, and then significantly improve the detectability and the Frequency Estimation precision of CW pulse signal.

Parallel multi-channel adaptive notch filter group is formed in parallel by a plurality of single-frequency notch filters, as shown in Figure 5.The orthogonal reference input on each road can be expressed as:

$\left\{\begin{array}{c}{x}_{\mathrm{ci}}\left(k\right)=A\cos \left({\mathrm{\ω}}_{i}k\right),\\ x_{\mathrm{si}}\left(k\right)=A\sin \left({\mathrm{\ω}}_{i}k\right).\end{array}\right.$ i＝0，2，...N. (1)

In the formula: frequencies omega _iBe pulse signal P _iCentre frequency.

After the filtering output of each passage adds up, ask difference to obtain residual error, be used for adjusting each and just hand power over wanted signal.

The adaptive iteration process is:

u _si(k+1)＝u _si(k)+με(k)sin(ω _ik) (2)

u _ci(k+1)＝u _ci(k)+με(k)cos(ω _ik) (3)

$\mathrm{\ϵ}\left(k\right)=d\left(k\right)-\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{y}_i\left(k\right)---\left(4\right)$

y _i(k)＝u _si(k)sin(ω _ik)+u _ci(k)cos(ω _ik) (5)

Wherein: u _Si(k) and u _Ci(k) for just handing power over, μ is a step-length, and ε (k) is a residual error, and d (k) is a desired output, y _i(k) be actual output.The envelope of CW signal and frequency can utilize weights to calculate after sef-adapting filter reaches stable state:

${\hat{A}}^2=\frac{1}{N}\underset{k=n}{\overset{k=n+N-1}{\mathrm{\Σ}}}[u_{s0}^2\left(k\right)+u_{c0}^2\left(k\right)]---\left(6\right)$

$\widehat{\mathrm{\ω}}={\mathrm{\ω}}_0-\frac{1}{N}\underset{k=n}{\overset{k=n+N-1}{\mathrm{\Σ}}}[{\mathrm{tg}}^{-1}\frac{u_{s0}\left(k\right)}{u_{c0}\left(k\right)}-{\mathrm{tg}}^{-1}\frac{u_{s0}(k-1)}{u_{c0}(k-1)}]---\left(7\right)$

(2) detection of LFM pulse and time delay are estimated

The detection and the time delay that adopt parallel copy correlator bank to be used for hyperchannel LFM pulse are estimated.Usually the copy correlator with the sample that transmits as the reference signal.And there are interference such as Doppler, many ways in the signal that nautical receiving set receives toward contact except that additive white noise, is difficult to realize the real coupling of reference signal and input signal.In addition, the CW pulse signal also may be gone here and there and be drained to adjacent frequency band, makes the LFM input in the frequency band false-alarm occur.At the problems referred to above, in the copy correlator design, taked counter-measure respectively.

Doppler effect can make the peak of the relevant output of copy produce skew, and peak value reduces, and then influence detects performance and time difference method.So in the signal waveform design, except that the higher LFM signal of time difference method, also increased CW pulse P ₀It not only can be used as pulse when surveying, and its frequency also can provide the size of Doppler frequency deviation, and the foundation as revising copy correlator reference signal frequency makes reference signal and received signal have identical Doppler frequency deviation.This not only can improve time difference method, also helps to improve the relevant treatment effect.

With respect to the water surface, water-bed medium often has bigger sound absorption, and buoy is nearer apart from the water surface simultaneously, and the reflected sound influence of other approach is less, disturbs so water surface primary event is topmost many ways, and other reflected sound can put aside.General water-surface reflection coefficient approaches-1, so the copy correlation peak of water-reflected sound is born, and the copy correlation peak of direct sound wave is positive, as long as thereby select positive maximum peak when selecting at the peak, corresponding signal just should be the direct sound wave pulse, disturbs thereby can effectively reject reflected sound.

For reducing the influence of CW pulse, in parallel copy correlator bank, increased the correlator passage (copy correlator 0) of CW pulse to the LFM input.Each road correlator output is carried out peakedness ratio after the peak choosing, if the passage of peak value maximum is a copy correlator 0, then leak for string; If the peak value maximum is that other passage and peak value are higher than the relevant peaks detection threshold, judge that then this pulse is effective, recording impulse type and time delay.

Parallel copy correlator bank as shown in Figure 6.

Claims (4)

1. realize that at long baseline asynchronous acoustic positioning system high frame per second do not have the method for fuzzy location for one kind, it is characterized in that:

At the signal transmitting terminal, signal form is the assembled pulse string; Described assembled pulse string intersects and uses CW and LFM signal, and the frequency difference of front and back pulse, reduces inter-pulse interference under the condition that does not reduce frame per second;

At signal receiving end, disposal route to the received signal is respectively applied for detection, time delay and the Frequency Estimation of CW pulse and LFM pulse for adopting parallel multi-channel adaptive notch filter group and parallel copy correlator bank.

2. according to claim 1ly realize that at long baseline asynchronous acoustic positioning system high frame per second do not have the method for fuzzy location, it is characterized in that: described assembled pulse string forms assembled pulse string repetition period 2s by 12 pulses, maximum 7 types of pulse combined; Dissimilar pulse band non-overlapping copies, or band overlapping but chirp rate polarity is opposite; Pi is pulse pattern sequence number, i=0 wherein, 1 ..., 6, P0 is the CW pulse, P1, P2 ... P6 is arrowband LFM pulse, and the Doppler shift that utilizes the real-time measurement target high-speed motion of pulse P0 to produce is adjusted the reference signal of making relevant treatment with the LFM pulse in real time; Pulse P1, P2 are as pulse subsequence odd even identification code;

3. according to claim 1 and 2ly realize that at long baseline asynchronous acoustic positioning system high frame per second do not have the method for fuzzy location, it is characterized in that described disposal route to the received signal is:

For the CW signal, the first step is to use parallel multi-channel adaptive notch filter group to handle the signal that receives, and second step was to use instantaneous frequency variance detecting device to be used for detection, time delay and the Frequency Estimation of CW pulse; For the LFM signal, this process also comprises two steps: the first step is to use the copy correlator bank to handle the signal that receives, and second step was LFM pulse and the due in thereof that search exists in the output of copy correlator bank; Simultaneously, the reference sample of copy correlator is revised in real time according to the CW pulsed frequency side-play amount that sef-adapting filter records.

4. according to claim 3ly realize that at long baseline asynchronous acoustic positioning system high frame per second do not have the method for fuzzy location, it is characterized in that: in the detection of CW pulse, time delay and the Frequency Estimation, the single channel adaptive notch filter is set up a plurality of trap passages, the centre frequency of corresponding several LFM pulse signals constitutes parallel multi-channel adaptive notch filter group respectively.

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