CN103152139A - Multi-base sonar space-time channel multiplexing method - Google Patents

Abstract

The invention relates to the field of processing of a sonar signal, and particularly relates to a multi-base sonar space-time channel multiplexing method. The method comprises the following steps of obtaining a space-time code signal modulated in a pseudo random way; distributing independent and mutually orthogonal space-time code groups for transmitting terminals of a multi-base system; encoding the transmitting address and transmitting time of each transmitting signal; copying the related detection on the received signal, and distinguishing whether the detection signal of the corresponding transmitting terminal is contained in the received signal; extracting a time code, and using the space-time signal code of the corresponding base to carry out maximum likelihood decoding; and obtaining the information of the transmitting address and the transmitting time of the detection signal, namely the space-time information. The method has the advantages that the correlation between code elements of the space-time code is reduced, the high-efficiency multiplexing of the multi-base sonar space-time channel is realized by the accurate evaluation of the space-time information of any received signal, the time of the multi-base sonar system is improved, and the utilization rate of frequency bands is improved.

Description

Channel multiplexing method when a kind of many bases sonar is empty

Technical field

The present invention relates to the signal processing field, be specifically related to a kind of many bases sonar channel multiplexing method when empty.

Background technology

Many bases sonar is the sonar system of separating on the R-T unit space, single or multiple sound source emission sound waves, the scatter echo of single or multiple receiving terminal receiving targets, reflection direction, time delay by the measurement target echo are come Directional Finding and Ranging, then come the solving target position by the position relationship between transceiver and sonar positioning equation.According to the R-T unit number, many bases sonar can be divided into multicast, multiple receipts, MIMO several types.That many bases sonar has concurrently is main, the work characteristics of passive sonar, have good concealment, antijamming capability strong, make up flexible configuration, be easy to optimal design, antisubmarine efficient advantages of higher.

Empty time-code is a kind of encoding scheme that is applicable to multiaerial system, and it is in fact that a kind of space-time two-dimensional is processed means.Multiaerial system can be with same primary signal by different transmit antennas, repeatedly do not sending in the same time, thereby created space diversity and time diversity.Empty time-code combines the advantage of space diversity and time diversity, and diversity gain and coding gain are provided simultaneously.The priori of needs channel according to whether, empty time-code can be divided into two classes, and the former comprises hierarchical space-time code, the empty time-code of grid etc., and the latter comprises unitary blank time code and difference empty time-code etc.

Radiocoustic position findings research in present many bases mainly concentrates on based on the known positioning and optimizing algorithm of direction finding, range finding result, as linear least-squares positioning mode, neural net method etc., and the underlying issues such as the channel that may occur when containing the many bases sonars work of multi-section transmitting terminal is disturbed mutually, Channel Sharing only have the minority article to be studied discussion.In European patent " Method for the multistatic detection and locating of a mobile craft through the use of digital broadcasting transmitters " literary composition, the signal that each transmitting terminal of many bases adopts different carrier frequency is proposed, in order to distinguish at receiving terminal, yet for many bases sonar system, band resource is limited, make the method only can be applied in the less situation of transmitting terminal number, this patent also relates to the detectable signal of how differentiating from different x times simultaneously.Many bases of multiple types sonar is in application, receiving terminal reception signal at a time consists of very complicated, be included on the space from different transmitting terminals, in time from direct wave and the target echo of different x times, if can't solve information when receiving signal empty, can't realize range finding, direction finding to target, positioning and optimizing algorithm is not more known where to begin.Therefore the efficient multiplexing of channel in actual applications, should preferentially be realized in many bases.

Summary of the invention

The purpose of this invention is to provide a kind of channel of many bases sonar of avoiding and disturb mutually, channel multiplexing method when realizing that the many bases sonar of many bases Channel Sharing is empty.

The object of the present invention is achieved like this:

The present invention includes following steps:

(1) at the empty time-code matrix of transmitting terminal with mutually orthogonal pseudo-random signal modulation full rank, obtain the empty time code signal of pseudorandom modulation;

(2) be that the transmitting terminal of many base systems distributes independent and mutually orthogonal code character when empty, as the code book that transmits of transmitting terminal;

(3) to encoding the emission address and the launch time that transmit each time, and with the form of address code and the timing code signal structure as detectable signal, detectable signal is via the transmitting terminal emission that contains many array elements;

(4) at receiving terminal with energy normalized, do to received signal the copy coherent detection with the transmitting terminal address code, differentiate to receive the detectable signal that whether contains this transmitting terminal in signal;

(5) detectable signal in base detected after, extraction time code, and the signal code book is done maximum likelihood decoding during with this base empty;

(6) according to detecting and decoded result, obtain emission address and the temporal information of detectable signal, information when namely empty.

Empty time-code adopts mutually orthogonal pseudo random sequence as the constellation collection signal of empty time-code

,

Wherein

Be the constellation collection of empty time-code, γ is

In element.Constellation collection element number l 〉=4, constellation concentrate arbitrary element should satisfy γ _mi≠ γ _nj, m ≠ n; I, j=1,2 ... l, γ ≠ γ ^*Or γ ≠-γ.

Empty time-code adopts the pseudo random sequence modulation.

The cross correlation of intersymbol when empty time-code is modulated the reduction sky by more pseudo random sequence or the longer pseudo random sequence of length.

Choose transmitting terminal when empty in code character with the empty time-code of the empty time-code coefficient of total correlation of other transmitting terminals minimums as described address code.

Beneficial effect of the present invention is:

The present invention by empty time-code being adopted the pseudo random sequence modulation, has reduced the cross correlation between each code element of empty time-code, distributes mutually orthogonal code character when empty by giving each many bases transmitting terminal, makes many bases sonar Channel Sharing become possibility.By sonar detection signal in many bases is carried out address, time encoding, realized the detectable signal of many bases receiving terminal resolution from different transmitting terminals, different x times.The accurate estimation of information by to any reception signal empty time the, the efficient multiplexing of channel when having realized many bases sonar empty have improved time, the band efficiency of many bases sonar system.

Description of drawings

Fig. 1 is many bases sonar system schematic diagram;

Fig. 2 is the mimo system schematic diagram;

Fig. 3 is signal emission flow chart;

Fig. 4 is for receiving signal processing flow figure;

Fig. 5 is the detectable signal schematic diagram.

Embodiment

Below in conjunction with accompanying drawing, the present invention is done specific descriptions.

Channel multiplexing method when a kind of many bases provided by the invention sonar is empty comprises transmitting terminal Design of Signal and receiving end signal processing two parts:

Transmitting terminal:

Step 1, with the empty time-code matrix of mutually orthogonal pseudo-random signal modulation full rank, obtain the empty time code signal based on pseudorandom modulation.

Step 2, be that each transmitting terminal of many base systems distributes independently and mutually orthogonal code character when empty, as the code book that transmits of each transmitting terminal.

Step 3, at transmitting terminal to encoding emission address and the launch time of emission each time, and with the form of the address code+timing code signal structure as detectable signal, detectable signal is via the transmitting terminal emission that contains many array elements.

Receiving terminal:

After step 4, energy normalized, do to received signal the copy coherent detection with each transmitting terminal address code, differentiate and receive the detectable signal that whether contains this transmitting terminal in signal.

Step 5, the detectable signal in certain base detected after, extract timing code wherein, and the signal code book is done maximum likelihood (ML) and is decoded during with this base empty.

Step 6, according to detecting and decoded result, obtain emission address and the temporal information of detectable signal, information when namely empty.

Wherein, in step 1, has better orthogonality, each constellation collection of empty time-code between code character when guaranteeing that following each transmitting terminal is empty

Should satisfy following requirement, 1) constellation collection element number l 〉=4,2) each constellation collection guarantees unequal and do not contain element each other, i.e. γ mutually _mi≠ γ _nj, m ≠ n; I, j=1,2 ... l, 3) constellation concentrates arbitrary element to satisfy, γ ≠ γ ^*Or γ ≠-γ.

Wherein, in step 1, for guaranteeing to have orthogonality between empty time-code code element, adopt mutually orthogonal pseudo random sequence as the constellation collection signal of empty time-code.

Wherein, in step 1, if each transmitting terminal needs that orthogonality is better, code element number is more when empty code character can realize by choosing larger constellation collection or increasing pseudo random sequence length.

Wherein, in step 1, according to the empty time-code matrix dimension of constructing in step 1, with the element number of selecting the constellation collection, can determine required pseudo random sequence number k * l, pseudo random sequence is divided into the k subset as the constellation collection signal of empty time-code.

Wherein, in step 1, pseudo random sequence can be produced by the mode of spread-spectrum signal, and generates required pseudo-random signal according to many bases sonar utilized bandwidth.

Wherein, in step 2, its cross correlation between reception signal corresponding to receiving terminal of the cross correlation of intersymbol during each sky.

Wherein, in step 2, the cross correlation of intersymbol when being mainly the examination sky, therefore, when calculating its reception signal, do not consider the inconsistency of each sub-channels, can think that each subchannel does not produce amplitude fading to signal, ignore simultaneously the impact of the local noise of receiving terminal and transmitting terminal, receiving terminal power influences.

Wherein, in step 2, suppose that transmitting terminal has M array element, receiving terminal has N array element, from i emission array element to j channel gain coefficient h that receives array element _ij=1,1≤i≤M, 1≤j≤N is constant in time T.Note H=(h _ij) _{M * N}

Wherein, in step 2, suppose that i emission array element at the signal that t sends constantly is

x _ti, (t=1,2 ..., T; I=1,2 ..., M), and note X=(x _ti) _{T * M}, receiving signal can be expressed as

In formula, Y=(y _tj) _{T * N}Receive the signal that array element receives constantly at T for N.

Wherein, in step 2, according to l ^k* l ^kTieing up the maximum correlation coefficient of each transmitting terminal that empty time-code cross-correlation matrix and many bases sonar allow intersymbol when empty, is that each transmitting terminal distributes empty time-code as much as possible.

Wherein, in step 3, information when receiving signal empty for obtaining is namely differentiated transmitting terminal and the x time that receives signal,

Carry out appropriate design to transmitting, adopt the form of address code+timing code as the structure of many bases sonar detection signal, be each transmitting terminal when transmitting each time to the transmitting terminal address information and launch time information encode, with its detectable signal as this.

Wherein, in step 3, address code is also used as the synchronous code of detectable signal except playing mark transmitting terminal site information function, is used for coordinating timing code estimated signal time delay.

Wherein, in step 3, choose transmitting terminal when empty separately in code character with the empty time-code of the empty time-code coefficient of total correlation of other transmitting terminals minimums, as the address code of this transmitting terminal.

Wherein, in step 3, set the transmit time interval and length of the cycle, to transmitting by carrying out cyclic ordering launch time, then carry out the temporal information coding.

Wherein, in step 3, length of the cycle should be chosen according to many bases sonar maximum operating range and signal transmission interval, arrives receiving terminal with the target echo that guarantees m n signal that circulates before the direct wave of n signal of m+1 circulation.Aliasing does not occur.

Wherein, in step 4, according to sending-receive equation, the reception signal of empty time-code can be expressed as

$Y=\sqrt{\frac{\mathrm{\ρ}}{M}}\mathrm{XH}+W$

In formula, ρ is the signal to noise ratio on receiving terminal, W=(w _tj) _{T * N}, w _tjIndicate j and receive the local noise that produces on array element when t receives signal constantly, suppose that here noise obedience variance is 1 zero-mean Gaussian Profile.

Wherein, in step 4, will receive signal before detecting and carry out normalization by energy.

Wherein, in step 4, do coherent detection with the reception signal respectively with each local transmitting terminal copy address code.

Wherein, in step 5, after the detectable signal from certain transmitting terminal being detected, extract the timing code of detectable signal, during only with this base empty, the signal code book is ML and is decoded.

Wherein, in step 5, can obtain emission address information and the temporal information of this detectable signal according to copy coherent detection result and ML decoded result.

Below in conjunction with accompanying drawing, channel multiplexing method when illustrating a kind of many bases provided by the invention sonar sky.

according to one embodiment of present invention, Fig. 1 is two receipts type many bases sonar system schematic diagrames, and in figure, A, B are respectively two transmitting terminals of many bases sonar system, and C is receiving terminal, and T represents target, and transmitting terminal A, B continue outside emission detection signal.

Fig. 2 is the mimo system schematic diagram.In the present embodiment, transmitting terminal emission array element number M=4, receiving terminal receives array element number N=1.

Fig. 3 is many bases sonar system transmitting terminal signal emission flow chart.According to the present embodiment, the detectable signal design is as follows with the emission flow process:

The full rank quasi-orthogonal space time-code of structure 4*4 is supposed G ₁(x ₁, x ₂) be the Alamouti code, order

$G_q(x_1,x_2,x_3,x_4)=\left[\begin{array}{cc}{G}_1(x_1,x_2)& G_1(x_3,x_4)\\ G_1(x_3,x_4)& G_1(x_1,x_2)\end{array}\right]$

It expansion is had

$G_q(x_1,x_2,x_3,x_4)=\left[\begin{array}{cccc}{x}_1& x_2& x_3& x_4\\ {-x}_2^{*}& x_1^{*}& {-x}_4^{*}& x_3^{*}\\ x_3& x_4& x_1& x_2\\ {-x}_4^{*}& x_3^{*}& {-x}_2^{*}& x_1^{*}\end{array}\right]$

For guaranteeing empty time-code full rank, and have weak cross correlation, make here

For further reducing the cross correlation of empty time-code, order

So that,

The cross correlation of intersymbol when reducing sky, the present invention adopts pseudo random sequence as modulation means.The present embodiment needs 4*4=16 pseudo random sequence altogether.

Be the mutually orthogonal independently pseudo random sequence combination of each constellation collection structure.Here use the pseudo random sequence on 16 7 rank of spread spectrum structure, and it is expanded on the sonar system used band of many bases, obtain corresponding pseudo-random signal.In this example, many bases sonar used band is chosen as 6-8kHz.16 pseudo-random signals etc. are given

, as the modulation signal of empty time-code.

Allow (x ₁, x ₂, x ₃, x ₄) get time

, bring G into _q(x ₁, x ₂, x ₃, x ₄), can generate 256 different empty time-code matrixes.As want to make and obtain more empty time-code matrix, make sonar each transmitting terminal in many bases, back obtain more empty time-code, can increase the constellation collection, as make constellation concentrate containing element number and be increased to 8, and construct the pseudo random sequence of respective number, can generate 4096 empty time-codes.

Investigate the corresponding signal correlation that receives of each sky time-code.Because the emphasis of investigating is the correlation between the corresponding reception signal of each sky time-code, so locate not consider the inconsistency of any channel and the impact of amplitude fading thereof, do not consider transmitting power, the impact of power to received signal of transmitting-receiving array element number here yet.

Order is from i emission array element to j channel gain coefficient h that receives array element _ij=1,1≤i≤M, 1≤j≤N, note H=(h _ij) _{M * N}, and order

Suppose that the pseudo-random signal that i emission array element sends constantly at t is x _ti, (t=1,2 ..., T; I=1,2 ..., M), and note X=(x _ti) _{T * M}, receiving signal can be expressed as

$Y=\sqrt{\frac{\mathrm{\ρ}}{M}}\mathrm{XH}$

Known parameters has been brought into

$Y=1\×\left[\begin{array}{cccc}{x}_1& x_2& x_3& x_4\\ {-x}_2^{*}& x_1^{*}& {-x}_4^{*}& x_3^{*}\\ x_3& x_4& x_1& x_2\\ {-x}_4^{*}& x_3^{*}& {-x}_2^{*}& x_1^{*}\end{array}\right]\×\left[\begin{array}{c}1\\ 1\\ 1\\ 1\end{array}\right]$

Can be calculated

$Y=\left[\begin{array}{c}\left(x_1\right)+\left(x_2\right)+\left(x_3\right)+\left(x_4\right)\\ \left({-x}_2^{*}\right)+\left(x_1^{*}\right)+\left({-x}_4^{*}\right)+\left(x_3^{*}\right)\\ \left(x_1\right)+\left(x_2\right)+\left(x_3\right)+\left(x_4\right)\\ \left({-x}_2^{*}\right)+\left(x_1^{*}\right)+\left({-x}_4^{*}\right)+\left(x_3^{*}\right)\end{array}\right]$

256 corresponding 256 of empty time-code matrixes receive signal.The cross correlation that receives between signal is the cross correlation of empty time-code, the mutual property of intersymbol when hereinafter directly address is for sky.

Calculate the cross correlation of empty time-code between in twos, obtain the cross-correlation matrix of sky time-code.

Maximum cross correlation coefficient r between the different transmitting terminals that allow according to many bases sonar transmit selects two groups of mutually orthogonal empty time-codes (cross correlation of intersymbol is not done restriction during sky on the same group) as two transmitting terminals code element that transmits separately.In this example, for each transmitting terminal distributes 6 empty time-codes.

Two groups of orthogonal space time-codes that note is chosen are

Y _A＝{Y _A1,Y _A2,…,Y _Ak};Y _B＝{Y _B1,Y _B2,…,Y _Bk};

Have＜Y according to above-mentioned requirements _Ai, Y _Bj〉＜r, 1≤i, j≤k, r=0.3 in this example, k=6.

Fig. 4 is for receiving signal processing flow figure, and Fig. 5 is the detectable signal structural representation.Detectable signal is comprised of address code and timing code two parts.Address code is made of an empty time-code, plays the site information and the synchronous effect that detects that indicate detectable signal, and timing code is comprised of one or more empty time-codes, is used for representing the temporal information that this transmits.When selecting each transmitting terminal empty in code character, with the empty time-code of the empty time-code coefficient of total correlation of other transmitting terminals minimums address code as this transmitting terminal detectable signal.

Investigate

$\min (\underset{j=1}{\overset{k}{\mathrm{\&Sigma;}}}<Y_{\mathrm{Ai}},Y_{\mathrm{Bj}}>),1\&le;i\&le;k$

Satisfy the Y of following formula _AiNamely as the address code of this transmitting terminal, be designated as Y _{A_loc}In like manner can try to achieve the address code Y of another transmitting terminal _Bi, be designated as Y _{B_loc}For the more many base systems of transmitting terminal number, as four transmitting terminal situations, analogy solves in the following way

$\min (\underset{j=1}{\overset{k}{\mathrm{\&Sigma;}}}<Y_{\mathrm{Ai}},Y_{\mathrm{Bj}}>+\underset{j=1}{\overset{k}{\mathrm{\&Sigma;}}}<Y_{\mathrm{Ai}},Y_{\mathrm{Cj}}>+\underset{j=1}{\overset{k}{\mathrm{\&Sigma;}}}<Y_{\mathrm{Ai}},Y_{\mathrm{Dj}}>),1\&le;i\&le;k$

Carry out time encoding to transmitting and mainly contain two kinds of thinkings, the one, absolute time coding, the 2nd, code for relative time.Absolute time coding is about to the absolute moment, the time, minute, second, be converted into information coding; Code for relative time is to transmit by Fixed Time Interval at transmitting terminal, and does cyclic ordering to transmitting.Many bases sonar need to lean on estimate the target location relative time delay of target echo, and therefore, many bases sonar need to be known the absolute transmission moment of signal.Many bases sonar more wishes to reduce the length that transmits, and improve tranmitting frequency, and the amount of information that code for relative time takies is less, so to many bases sonar system, the code for relative time mode is more suitable.

By many bases sonar operating distance and sending and receiving end distance farthest, can determine that adjacent twice emitting signal arrives the maximum time difference of receiving terminal (comprising with direct wave and two kinds of forms of target echo), divided by Transmission Time Interval, just can determine cyclic ordering length.In this example, length of the cycle is 30.

In this example, timing code is made of two empty time-codes, can represent k ²=36 different time informations are applicable to length of the cycle less than 36 situation.

The blank time slot of filling between code element should be according under the sonar maximum operating range of many bases, and the maximum delay of issuable many ways expansion decides.

According to empty time-code send-receive equation, obtain receiving terminal and receive signal and be

$Y=\sqrt{\frac{\mathrm{\&rho;}}{M}}\mathrm{XH}+W$

In formula, W=(w _tj) _{T * N}, w _ijIndicate j and receive the local noise that produces on array element when t receives signal constantly, suppose that here noise obedience variance is 1 zero-mean Gaussian Profile.

Utilize each transmitting terminal address code of local copy to do coherent detection with the reception signal.

At first will receive signal and carry out energy normalized,

$Y=\frac{Y}{E\left[{\left|Y\right|}^2\right]}$

Again examination receive the base the maximum dry that requires make an uproar than the time, local copy address code Y _{A_loc}With contain Y _BThe correlated results of noise signal, false alarm probability is as requested set the detection threshold of base A, in like manner can try to achieve the detection threshold of base B.

At receiving terminal, use simultaneously local copy signal Y _{A_loc}And Y _{B_loc}Do to received signal the copy coherent detection.When the correlated results of a certain copy address code surpasses thresholding, think to receive detectable signal from this transmitting terminal, according to copy address code and the relevant peaks estimation time delay that receives signal, play the effect of time synchronized simultaneously.By the result of back, from receive signal, extract two empty time-codes that contain temporal information, and it is carried out the ML decoding.The ML decoding of empty time-code can be converted into following problem,

ζ={ S ₁, S ₂..., S _LIt is the set of empty time-code.As long as S _iIn the substitution following formula, choose minimum, can realize decoding.In the present invention, after the detectable signal that detects from certain transmitting terminal, choose the signal code book Y of this transmitting terminal _AOr Y _BIn empty time-code carry out ML decoding, the expression formula of therefore decoding can further arrange and be

The information during detectable signal that can obtain to receive by address code, timing code empty, namely realized receiving terminal differentiate on the space from different transmitting terminals, on the time from the detectable signal of different x times, thereby channel multiplexing problem when having realized many bases sonar empty.

Claims (5)

1. channel multiplexing method when base sonar more than a kind is empty is characterized in that, comprises the steps:

(1) at the empty time-code matrix of transmitting terminal with mutually orthogonal pseudo-random signal modulation full rank, obtain the empty time code signal of pseudorandom modulation;

(2) be that the transmitting terminal of many base systems distributes independent and mutually orthogonal code character when empty, as the code book that transmits of transmitting terminal;

(3) to encoding the emission address and the launch time that transmit each time, and with the form of address code and the timing code signal structure as detectable signal, detectable signal is via the transmitting terminal emission that contains many array elements;

(4) at receiving terminal with energy normalized, do to received signal the copy coherent detection with the transmitting terminal address code, differentiate to receive the detectable signal that whether contains this transmitting terminal in signal;

(5) detectable signal in base detected after, extraction time code, and the signal code book is done maximum likelihood decoding during with this base empty;

(6) according to detecting and decoded result, obtain emission address and the temporal information of detectable signal, information when namely empty.

2. channel multiplexing method when a kind of many bases according to claim 1 sonar is empty is characterized in that: described empty time-code adopts mutually orthogonal pseudo random sequence as the constellation collection signal of empty time-code

, wherein

Be the constellation collection of empty time-code, γ is In element.Constellation collection element number l 〉=4, constellation concentrate arbitrary element should satisfy γ _mi≠ γ _nj, m ≠ n; I, j=1,2 ... l, γ ≠ γ ^*Or γ ≠-γ.

3. channel multiplexing method when a kind of many bases according to claim 1 and 2 sonar is empty is characterized in that: described empty time-code adopts the pseudo random sequence modulation.

4. channel multiplexing method when a kind of many bases according to claim 3 sonar is empty is characterized in that: described empty time-code is modulated the cross correlation that reduces intersymbol when empty by more pseudo random sequence or the longer pseudo random sequence of length.

5. channel multiplexing method when a kind of many bases according to claim 4 sonar is empty is characterized in that: choose transmitting terminal when empty in code character with the empty time-code of the empty time-code coefficient of total correlation of other transmitting terminals minimums as described address code.

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