CN103390407B - Based on the direct sound wave method of purification of double-basis unit cepstrum territory reset technique - Google Patents

Abstract

The present invention is to provide a kind of direct sound wave method of purification based on double-basis unit cepstrum territory reset technique.(1) adopt main primitive and receive underwater acoustic channel output signal from primitive double-basis unit, then the signal of each primitive is carried out cepstrum computing respectively, signal and channel are changed into the additive relation in cepstrum territory in the convolution relation of time domain; (2) reset based on double-basis unit cepstrum territory, utilize same or foreign peoples's component decision revision mechanism, the Multi-path interference composition in the main primitive of filtering; (3) the main primitive cepstrum signal of counterweight postpone does inverse Complex Cepstrum Transform, realizes the purification of direct sound wave signal.The advantage applies of the method exists: implementation procedure is without the need to knowing the priori such as channel or signal parameter in advance; To Quick-Change channel condition, high-speed motion node, large Doppler, there is adaptive faculty; Method is simple and easy, condition is loose, direct sound wave refining effect is good.

Description

Based on the direct sound wave method of purification of double-basis unit cepstrum territory reset technique

Technical field

What the present invention relates to is a kind of Underwater acoustic signal processing method, is specifically related to the method that the many ways impact of channel in underwater sound multi-path signals suppresses and direct sound wave is purified.

Background technology

Ocean channel belongs to the random inhomogeneous medium channel in the two interfaces of out-of-flatness, transmit along different paths and arrive acceptance point, various reflected sound and direct sound wave are superimposed mutually, the parameters such as the amplitude of direct sound wave signal, phase place, frequency are caused to distort, increase the difficulty of Underwater acoustic signal processing, also have a strong impact on the performance of underwater sound equipment.Therefore, adopt an effective measure that to realize direct sound wave purifying signal be one of gordian technique of Underwater acoustic signal processing.

According to the theory of ray acoustics, the main cause of direct sound wave signal distortion is the many ways of underwater acoustic channel.At present, conventional anti-many ways technology comprises diversity technique, spread spectrum technic, channel equalization technique and channel error correction coding techniques etc., and this several technology may be used alone, can also be used in combination.Each method suppresses the starting point on many ways different, and first two technology is the correlativity by reducing multi-path signals; Channel equalization technique is the wave form distortion caused by compensate for channel multi-path effect, and channel error correction coding uses the redundant data added in transmitting information to carry out error correction.In recent years, occurred again mirror technology time reversal, it utilizes its space-focusing and time compress characteristic, makes the many ways spread signal received be similar to former transmitting by compressing in time, thus realize the object of direct sound wave purifying signal.

Summary of the invention

The object of the present invention is to provide a kind of respond well, calculate simple, to be applicable to large Doppler and the Quick-Change channel direct sound wave method of purification based on double-basis unit cepstrum territory reset technique.

The object of the present invention is achieved like this:

(1) adopt main primitive and receive underwater acoustic channel output signal from primitive double-basis unit, then the signal of each primitive is carried out cepstrum computing respectively, signal and channel are changed into the additive relation in cepstrum territory in the convolution relation of time domain;

(2) reset based on double-basis unit cepstrum territory, utilize same or foreign peoples's component decision revision mechanism, the Multi-path interference composition in the main primitive of filtering;

(3) the main primitive cepstrum signal of counterweight postpone does inverse Complex Cepstrum Transform, realizes the purification of direct sound wave signal.

Described double-basis unit cepstrum territory resets and is: adopt the master that position is close, receive underwater acoustic channel output signal from two primitives simultaneously, in the signal that they receive, direct sound wave composition is identical, multi_path channel composition is different, that is, in cepstrum territory, after the convolution relation of direct sound wave signal and multi_path channel changes into additive relation, main, high from the similarity of the direct sound wave signal cepstrum component of primitive, be referred to as similar component, the similarity of multi_path channel cepstrum component is then very low, be referred to as foreign peoples's component, by comparison and differentiation master, from the cepstrum of primitive, retain similar component and filtering foreign peoples component.

Described same or foreign peoples's component decision revision mechanism is: using intensity ratio β (n) of the cepstrum of master and slave two primitives as judgement amount, if a threshold range [β ₁, β ₂], then to the cepstrum pointwise decision revision of two primitives, if β (n) ∈ is [β ₁, β ₂] being then judged to similar component, then the cepstrum of main primitive is modified to the average of similar component; Otherwise be judged to foreign peoples's component, then the cepstrum of main primitive is modified to the little value in foreign peoples's component.

Advantage of the present invention shows: the thought that (1) the present invention adopts double-basis unit cepstrum territory to reset, without the need to knowing the priori such as channel or signal parameter in advance; (2) for conventional adaptive equalization, the time reversal direct sound wave purification technique such as mirror, the present invention is without the need to Time Created or detection sequence, therefore the direct sound wave be applicable under Quick-Change channel condition is purified, and has adaptive faculty to high-speed motion node, large Doppler.(3) the present invention adopts with (different) class component decision revision mechanism, takes full advantage of the difference of similarity between direct sound wave signal and multi_path channel between primitive, can effective filtering Multi-path interference, and trickle to effect of signals, and method is simple and easy, and loosely, refining effect is good for condition.

Accompanying drawing explanation

Fig. 1 is (direct sound wave) time domain waveform that transmits.

The channel output signal time domain waveform that Fig. 2 (a)-Fig. 2 (b) receives for master and slave primitive, Fig. 2 (a) is the channel output signal time domain waveform that main primitive receives; Fig. 2 (b) is the channel output signal time domain waveform received from primitive.

Fig. 3 is the direct sound wave method of purification process flow diagram based on double-basis unit cepstrum territory reset technique.

The channel output signal cepstrum domain waveform that Fig. 4 (a)-Fig. 4 (b) receives for master and slave primitive, Fig. 4 (a) is the channel output signal cepstrum domain waveform that main primitive receives; Fig. 4 (b) is the channel output signal cepstrum domain waveform received from primitive.

Fig. 5 is the cepstrum signal waveform of the main primitive after over-reset.

Fig. 6 (a)-Fig. 6 (b) is the ping after purification and error time domain waveform, and Fig. 6 (a) is the ping time domain waveform after purifying; Fig. 6 (b) is purification error time domain waveform.

Embodiment

The present invention includes following basic step:

(1) adopt double-basis unit (be called main primitive and from primitive) to receive underwater acoustic channel output signal, then the signal of each primitive is carried out cepstrum computing respectively, signal and channel are changed into the additive relation in cepstrum territory in the convolution relation of time domain.

(2) reset thought based on double-basis unit cepstrum territory, utilize with (different) class component decision revision mechanism, the Multi-path interference composition in the main primitive of filtering.

(3) the main primitive cepstrum signal of counterweight postpone does inverse Complex Cepstrum Transform, realizes the purification of direct sound wave signal.

Core content of the present invention is that double-basis unit cepstrum territory resets thought, its basic thought is: adopt close master and slave two primitives in position to receive underwater acoustic channel output signal simultaneously, in the signal that they receive, direct sound wave composition is identical, and multi_path channel composition is different.That is, in cepstrum territory, after the convolution relation of direct sound wave signal and multi_path channel changes into additive relation, the similarity of the direct sound wave signal cepstrum component of master and slave primitive is high, be referred to as similar component, the similarity of multi_path channel cepstrum component is then very low, is referred to as foreign peoples's component.Utilize this feature, by comparison and the cepstrum differentiating master and slave primitive, retain similar component and filtering foreign peoples component, the impact of many ways can be suppressed, realize the purification of direct sound wave signal.

Of the present invention with (different) class component decision revision mechanism, its basic thought is: using intensity ratio β (n) of the cepstrum of master and slave two primitives as judgement amount, if a threshold range [β ₁, β ₂], then to the cepstrum pointwise decision revision of two primitives.If β (n) ∈ is [β ₁, β ₂] being then judged to similar component, then the cepstrum of main primitive is modified to the average of similar component; Otherwise be judged to foreign peoples's component, then the cepstrum of main primitive is modified to the little value in foreign peoples's component.

Below in conjunction with the drawings and specific embodiments, the present invention is further described in detail:

Implementation condition: transmit (direct sound wave) is for exponent e ^-8tthe single frequency sinusoidal signal of weighting, f ₀=1kHz, signal length 0.2s, its time domain waveform as shown in Figure 1.Sound source position (50,0,100), dark 200 meters of sea.Velocity of sound c=1468.35 meter per second.Main primitive position (0,50,50) m, from primitive position (110,60,50) m, the time domain waveform of the channel output signal that they receive as shown in Figure 2.

For above-mentioned condition, provide the direct sound wave purification step of this specific embodiment, refer to Fig. 3:

1, the signal of each primitive is carried out cepstrum computing respectively, signal and channel are changed into additive relation in the convolution relation of time domain, that is:

$\hat{x}\left(n\right)=F^{-1}\left[\ln \left(X\left(e^{\mathrm{j\ω}}\right)\right)\right]---\left(1\right)$

Wherein, the cepstrum of Received signal strength x (n), signal X (e ^{j ω}) be the Fourier transform of x (n), F ^-1[ ] represents inverse fourier transform.Cepstrum domain waveform after conversion as shown in Figure 4.

2, reset thought based on double-basis unit cepstrum territory, utilize with (different) class component decision revision mechanism, the Multi-path interference composition in the main primitive of filtering.

If the cepstrum of master and slave primitive is respectively

First, their intensity ratio is calculated

$\mathrm{\β}\left(n\right)=\left|{\hat{x}}_z\left(n\right)\right|/\left|{\hat{x}}_c\left(n\right)\right|---\left(2\right)$

Then, using β (n) as judgement amount, carry out with (different) class component decision revision.If threshold range [β ₁, β ₂]=[0.5,2], decision revision criterion is: if β (n) ∈ is [β ₁, β ₂] be then similar component, then the cepstrum of main primitive is modified to the average of similar component, otherwise is foreign peoples's component, then the cepstrum of main primitive is modified to the little value in foreign peoples's component, namely

${{\hat{x}}^{\′}}_z\left(n\right)=\left\{\begin{array}{cc}({\hat{x}}_z\left(n\right)+{\hat{x}}_z\left(n\right))/2& \mathrm{\β}\left(n\right)\∈[{\mathrm{\β}}_1,{\mathrm{\β}}_2]\\ \min ({\hat{x}}_z\left(n\right),{\hat{x}}_c\left(n\right))& \mathrm{else}\end{array}---\left(3\right)\right.$

Wherein, for the cepstrum signal of the main primitive after over-reset, result as shown in Figure 5.

3, the main primitive cepstrum signal of counterweight postpone does inverse Complex Cepstrum Transform, obtains the direct sound wave signal x'(n after purifying), that is:

$x^{\′}\left(n\right)=F^{-1}\left[\exp \left({{\hat{x}}_z}^{\′}\left(n\right)\right)\right]---\left(4\right)$

Wherein, exp () represents exponent arithmetic, F ^-1[ ] represents inverse fourier transform.Ping after purification and error are as shown in Figure 6.

Finally it should be noted that, above embodiment is only in order to describe technical scheme of the present invention instead of to limit this technical method, the present invention can extend in application other amendment, change, application and embodiment, and therefore think that all such amendments, change, application, embodiment are all in spirit of the present invention and teachings.

Claims (2)

1., based on a direct sound wave method of purification for double-basis unit cepstrum territory reset technique, it is characterized in that:

(1) adopt main primitive and receive underwater acoustic channel output signal from primitive double-basis unit, then the signal of each primitive is carried out cepstrum computing respectively, signal and channel are changed into the additive relation in cepstrum territory in the convolution relation of time domain;

(2) reset based on double-basis unit cepstrum territory, utilize same or foreign peoples's component decision revision mechanism, the Multi-path interference composition in the main primitive of filtering; Described same or foreign peoples's component decision revision mechanism is: using intensity ratio β (n) of the cepstrum of master and slave two primitives as judgement amount, if a threshold range [β ₁, β ₂], then to the cepstrum pointwise decision revision of two primitives, if β (n) ∈ is [β ₁, β ₂] being then judged to similar component, then the cepstrum of main primitive is modified to the average of similar component; Otherwise be judged to foreign peoples's component, then the cepstrum of main primitive is modified to the little value in foreign peoples's component;

(3) the main primitive cepstrum signal of counterweight postpone does inverse Complex Cepstrum Transform, realizes the purification of direct sound wave signal.

2. the direct sound wave method of purification based on double-basis unit cepstrum territory reset technique according to claim 1, it is characterized in that described double-basis unit cepstrum territory resets is: adopt the master that position is close, receive underwater acoustic channel output signal from two primitives simultaneously, in the signal that they receive, direct sound wave composition is identical, multi_path channel composition is different, that is, in cepstrum territory, after the convolution relation of direct sound wave signal and multi_path channel changes into additive relation, main, high from the similarity of the direct sound wave signal cepstrum component of primitive, be referred to as similar component, the similarity of multi_path channel cepstrum component is then very low, be referred to as foreign peoples's component, by comparison and differentiation master, from the cepstrum of primitive, retain similar component and filtering foreign peoples component.