CN102833016A - Determination method in allusion to homogenous signal time difference under multipath environment - Google Patents

Abstract

The invention relates to a determination method in allusion to homogenous signal time difference under a multipath environment. The determination method comprises the following steps of: establishing a received signal sample, determining residual errors including self-correlation processing and determination of auto-regression parameters and finally determining time difference of two paths of signals through acquiring a cross-correlation spectrum of residual errors of two paths of signals. According to the invention, compared with the prior art that two paths of received homogenous sampled signals are directly cross-correlated, the determination method disclosed by the invention has the characteristics that residual errors of two paths of sampled signals are cross-correlated by an auto-regression method to ensure that related peak shapes are sharp and are still easy to distinguish even though arrival time difference of each signal is shorter, thereby effectively improving the time difference measurement resolution rate and accuracy; and the time difference value measured by the determination method accords with the theoretical value. Therefore, the determination method has the characteristics of being high in resolution ratio of the cross-correlation spectrum of sampled signals under the multipath environment, effectively improving the signal time difference determination accuracy, providing accurate parameters for subsequent positioning of a target signal source and the like.

Description

A kind of assay method that under multi-path environment, is directed against with the source signal time difference

Technical field

The invention belongs to the time difference assay method under the multi-path environment in the electronic information technical field, particularly a kind of under multi-path environment each signal receiver to assay method with time difference of source signal.

Background technology

Along with the develop rapidly of signal arrival time difference location technology, the radio position finding radio directional bearing technology is used widely in the radio monitoring field.AOA (ripple reaches the angle location method), TOA (ripple reaches the time positioning mode), TDOA (ripple reaches the time difference positioning mode) are the cellular system Mobile Location Techniques that development potentiality is arranged at present most.Ripple reaches the time difference or claims that ripple reaches time delay, is meant between the same source signal that different receivers receive in the receiver array because the time difference that the transmission range difference causes.Confirm that the time difference is an important component part of input and parameter extraction in the modern signal processing system, be widely used in fields such as detection, communication, biomedicine and geophysics.

At present, the time difference measurement method is more, and wherein the broad sense cross-correlation method is comparatively classical.This method is passed through following formula to the road signal that receives and another road signal of launching with source signal:

$r_{x_1{x}_2}\left(k\right)=E\left[x_1\left(t\right){x_2}^{*}(t-k)\right]$

Directly carry out cross correlation process; In the formula: x ₁And x ₂Represent that respectively t representes the current time with the two paths of signals of source signal through different paths, t-k representes k chronomere before the current time,

The cross-correlation function of expression two paths of signals, and the desired value computing is asked in E [] expression, ^*The conjugation of expression plural number.By the similarity degree of cross-correlation function waveform comparison two paths of signals, the maximum time offset of similarity is corresponding time delay value.This method since its have that algorithm is simple, amount of calculation is little, be easy to realize, processing gain is high and the advantage that can be applied to the low signal-to-noise ratio environment, the broad sense cross-correlation method has become uses class methods the most widely at present both at home and abroad in confirming time difference information.Since Knapp in 1976 and the paper publishing of Cater, be active research direction in the signal processing field to the exploration of the broad sense cross-correlation method of confirming time delay and relevant parameter about broad sense cross-correlation latency measurement always.When between reference signal and noise, noise and the noise fully during quadrature, this method is the best practice of time delay measurement.But in the actual conditions; Above-mentioned two complete orthogonality conditions are implacable; This moment is in order to solve the mensuration problem of time delay; The broad sense cross-correlation method need be carried out albefaction to the received signal and handled, is that frequency domain weighting is handled, and makes reference signal and the peak shape more sharp-pointed (obviously) that receives signal correction, with the purpose of the stability of the resolution capability that reaches the raising time delay and time delay measurement.But the structure of weighting function needs the concrete statistical information of signal and noise in the broad sense cross-correlation method; Yet in practical engineering application; The statistical information of on-site signal and noise is not often learnt as yet; Can only replace the statistical information that relates in the weighting function with signal and one group of measured value of noise, thereby its actual performance and this method hope that the theoretical effect that obtains has big gap usually.

In actual application environment; Especially city or interior of building have under the situation than multi-obstacle avoidance; In the air through processes such as the reflection of barrier, refraction, scatterings, often arrive the phenomenon of receiver with different delay with source signal, be called multipath effect through mulitpath.Multipath effect is that signal time delay is determined at unavoidable problem in the practical application.Signal that signal source is launched is through the propagation of mulitpath, promptly after different reflector reflections, successively receive for same transducer, thereby formed mixed signal.Comprise a plurality of same source signal and noises that experience time delay, range coefficient and phase change in this mixed signal; Therefore when time difference that each road signal arrives hour, the waveform that causes each road signal is overlapping, cause that relevant peaks deformation is wide, summit is level and smooth, measure error is big, defectives such as poor accuracy.

Summary of the invention

The objective of the invention is defective to the background technology existence; Improve a kind of assay method that under multi-path environment, is directed against with the source signal time difference of design; Do not improve the time difference measure under the prerequisite of signal processing amount of calculation, improve time delay resolution, and effectively improve signal receiver receives signal time difference mensuration under multi-path environment accuracy; And then purposes such as accurate parameter are provided for the location in echo signal source.

Solution of the present invention is on the basis of background technology broad sense cross-correlation method; To defectives such as the accuracy of its specifying information of desired signal in practical engineering application and measurement result precision deficiencies; The present invention introduce the autoregression method, promptly utilize the stochastic variable linear combination in some moment in early stage to describe after the linear regression method of certain moment stochastic variable, this method is typically expressed as:

$s\left(t\right)=\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{\mathrm{\α}}_{m}s(t-m)+v\left(t\right)$

Wherein s (t) is the signal of time point t, α _mRepresent m rank auto-regressive parameter, s (t-m) is the measuring-signal of preceding m the chronomere of current demand signal, m=1, and 2 ..., M, M are the autoregression exponent numbers, v (t) is a residual error;

Its auto-correlation function r _Vv(k):

$r_{\mathrm{vv}}\left(k\right)=E\left[v\left(t\right)v^{*}(t-k)\right]=\left\{\begin{array}{cc}{\mathrm{\σ}}_v^2,& k=0\\ 0,& k\≠0\end{array}\right.$

Have the sharp-pointed characteristic in white noise coherence spectra peak, in the formula: the desired value computing is asked in E [] expression, ^*The conjugation of expression plural number, t representes the current time, t-k representes k chronomere before the current time,

The variance of expression white noise;

The signal that receives of two receivers is following in the method:

x ₁(t)=s(t-t ₀)+n ₁(t)

$x_2\left(t\right)=\underset{j=1}{\overset{J}{\mathrm{\Σ}}}{g}_{2j}s(t-t_j)+n_2\left(t\right)$

Wherein: x ₁(t) and x ₂(t) be the two-way current demand signal that two receivers are received respectively, t is a current time, n ₁(t), n ₂(t) be that two receivers receive and uncorrelatedly mutually in the signals (to any time t and τ, have

) noise, the signal of s (t) expression signal source emission, t ₀The reception signal of representing first receiver is with respect to the time difference that signal source transmitted, t _jThe signal of propagating along the j paths in the reception signal of second receiver of expression is with respect to the time difference that signal source transmitted, g _2jRepresent the signal amplitude coefficient that the j paths is propagated, j=1,2 ..., J, J are number of path, ∑ is represented summation;

The inventive method is with two-way sampled signal x ₁(t) and x ₂(t) replace with respectively:

Δx ₁(t)=x ₁(t)-α ₁x ₁(t-1)-α ₂x ₁(t-2)

Δx ₂(t)=x ₂(t)-α ₁x ₂(t-1)-α ₂x ₂(t-2)

Wherein: x ₁(t) and x ₂(t) be the current two paths of signals of receiving respectively of two receivers, x ₁(t-1) and x ₂(t-1) be the signal of the previous chronomere of the current demand signal received of two receivers, x ₁(t-2) and x ₂The signal of preceding two chronomeres of the current demand signal of (t-2) receiving for each receiver, α ₁x ₁(t-1)+α ₂x ₁(t-2) and α ₁x ₂(t-1)+α ₂x ₂(t-2) represent the current demand signal linear combination of variant chronomere received signal before respectively; Δ x ₁(t) and Δ x ₂(t) be respectively x in the autoregression method ₁(t) and x ₂(t) residual error;

Again the residual error of two paths of signals is directly carried out cross correlation process, that is:

$r_{{\mathrm{\Δx}}_2\left(t\right){\mathrm{\Δx}}_1\left(t\right)}\left(k\right)=E\left[{\mathrm{\Δx}}_2\left(t\right){{\mathrm{\Δx}}_1}^{*}(t-k)\right]$

Wherein:

Expression Δ x ₁(t) with Δ x ₂(t) cross-correlation function between, t representes the current time, and t-k representes the moment of k unit interval before the current time, and the desired value computing is asked in E [] expression, ^*The conjugation of expression plural number.

The present invention utilizes promptly that the residual error coherence spectra satisfies the sharp-pointed characteristic of white Gaussian noise coherence spectra peak value in this method, improves the resolution of time difference measurement thus, thereby realizes its goal of the invention; Thereby the inventive method comprises:

Step 1. is set up the received signal sample: at first confirm two receivers 1,2 that carry out time difference measurement; Receive the signal of same signal source emission when two receivers after, utilize analog-digital converter respectively the analog signal conversion of receiver 1,2 outputs to be data signal; Then the two ways of digital signals after the conversion is carried out synchronized sampling at interval according to the peaked multiple setting-up time of the expection time difference between the two paths of signals, the sample of two-way received signal 1,2;

Confirming of step 2. residual error

2.1. auto-correlation processing: according to background technology step 1 gained 1,2 two-way sampled signals are carried out auto-correlation processing, obtain autocorrelation matrix, again matrix is carried out singular value decomposition, obtain its singular value and corresponding eigenvectors matrix;

2.2. confirm auto-regressive parameter: the step 2.1 gained zero pairing characteristic vector of singular value is carried out normalization handle, thereby obtain each the rank auto-regressive parameter in the autoregression method;

2.3. residual error of obtaining: in normalization gained auto-regressive parameter substitution following formula in the step 2.2:

${\mathrm{\Δx}}_1\left(t\right)=x_1\left(t\right)-\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{\mathrm{\α}}_m{x}_1(t-m)$

${\mathrm{\Δx}}_2\left(t\right)=x_2\left(t\right)-\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{\mathrm{\α}}_m{x}_2(t-m)$

Obtain the residual delta x of two paths of signals 1,2 respectively ₁(t) and Δ x ₂(t), wherein: x ₁(t) signal source of receiving at current time t for first receiver is at time point t-t ₀The same source signal that sends, x ₂(t) be second receiver in same signal source that current time t receives respectively at time point t-t ₁And t-t ₂The mixed signal of the same source signal that sends, α _mRepresent m rank auto-regressive parameter, ∑ is represented summation;

Confirming of step 3. time difference

3.1. obtain the coherence spectra of two paths of signals 1,2 residual errors: the residual error according to gained two paths of signals in the step 2.3 is passed through following formula:

$r_{{\mathrm{\Δx}}_2\left(t\right){\mathrm{\Δx}}_1\left(t\right)}\left(k\right)=E\left[{\mathrm{\Δx}}_2\left(t\right){{\mathrm{\Δx}}_1}^{*}(t-k)\right]$

Carry out cross correlation process, obtain the coherence spectra of the residual error of two paths of signals; Δ x wherein ₁(t) with Δ x ₂(t-k) represent the residual error of two paths of signals 1,2 respectively, t representes the current time, and t-k representes the time of k unit interval before the current time,

Expression Δ x ₁(t) with Δ x ₂(t) cross-correlation function between; The value of the coherence spectra of residual error is determined by following formula:

${\hat{r}}_{{\mathrm{\Δx}}_2\left(t\right){\mathrm{\Δx}}_1\left(t\right)}\left(k\right)=\left\{\begin{array}{cc}\frac{1}{L+k}\underset{t=1}{\overset{L+k}{\mathrm{\Σ}}}{\mathrm{\Δx}}_2\left(t\right){{\mathrm{\Δx}}_1}^{*}(t-k),& -L+1\≤k\≤0\\ \frac{1}{L-k}\underset{t=k+1}{\overset{L}{\mathrm{\Σ}}}{\mathrm{\Δx}}_2\left(t\right){{\mathrm{\Δx}}_1}^{*}(t-k),& L-1\≥k>0\end{array}\right.$

Wherein:

is cross-correlation function

value of residual error; L representes sampling time interval, and ∑ is represented summation;

3.2. confirm the time difference of two paths of signals: the pairing time value of peak-peak is the time difference of two paths of signals in the coherence spectra of step 3.1 gained two-way sampled signal residual error; This time difference is the time difference that two receivers 1,2 are received the signal of same signal source emission.

Above-mentioned two ways of digital signals after the conversion is carried out synchronized sampling at interval according to the peaked multiple setting-up time of the expection time difference between the two paths of signals, its sampling time interval is not less than 10 times of greatest expected time difference between the two paths of signals.

The present invention is owing to the two-way homology sampled signal that background technology is received is directly carried out cross correlation process; Change into and utilize the autoregression method, through the residual error of two-way sampled signal is carried out cross correlation process, even make relevant peak shape sharply hour still be easy to differentiate, thereby effectively improved the resolution and the accuracy of time difference measurement in time difference that each road signal arrives; The time difference value that sampled signal residual error coherence spectra of the present invention is surveyed (demonstration) conforms to theoretical value.Thereby the present invention to have the resolution of gained sampled signal coherence spectra under multi-path environment high, improved the accuracy that the signal time difference measures effectively, can be continue after to the location in echo signal source characteristics such as accurate parameter are provided.

Description of drawings

Fig. 1 measures effect sketch map (broad sense coherence spectra curve chart) for adopting the background technology broad sense cross-correlation method emulation time difference;

Fig. 2 for adopt instantiation mode of the present invention with background technology the same terms time difference mensuration effect sketch map (the coherence spectra curve chart of residual error) down;

The delay of the express time of negative sign (-) shown in the abscissa chronomere among the figure.

Embodiment:

Present embodiment is an example to adopt second order autoregression method, that is:

s(t)＝α ₁s(t-1)+α ₂s(t-2)+v(t)

α ₁, α ₂Represent single order and second order auto-regressive parameter respectively.

Autoregression model stability condition is: α ₂+ α ₁<1 and | α ₂|<1; Adopt the autoregression method to produce the signal s (t) that signal source is sent in this execution mode, single order and second order auto-regressive parameter are respectively α ₁=1.9114 and α ₂=-0.95, residual error v (t) is the white Gauss noise that variance equals 1.

After signal source was sent signal, wherein the signal that receives of first receiver was x ₁(t); Second signal x that receiver receives ₂(t) propagate the mixed signal that forms for the signal of signal source emission through two paths, wherein the corresponding time difference value of peak-peak is second receiver and receives that with respect to first receiver signal source sends the time-delay value of signal in the coherence spectra; Described in background technology, since the existence of multipath effect, x ₂(t) two signals that experienced the same signal source emission of different paths and time delay, different range coefficients have been comprised in; The time delay of receiving the signal of the same signal source emission that arrives through two paths with respect to second receiver of first receiver is respectively t ₁-t ₀, t ₂-t ₀, range coefficient is respectively g ₂₁, g ₂₂

The signal that two receivers receive is following:

x ₁(t)＝s(t-t ₀)+n ₁(t)

x ₂(t)=g ₂₁s(t-t ₁)+g ₂₂s(t-t ₂)+n ₂(t)

Wherein: x ₁(t) signal source of receiving at current time t for first receiver is at time point t-t ₀The same source signal that sends, x ₂(t) be second receiver in same signal source that current time t receives at time point t-t ₁And t-t ₂The mixed signal of the same source signal that sends, n ₁(t), n ₂(t) be respectively two receivers and receive the noise in the signal, the signal of s (t) expression signal source emission, t ₀The time difference when reception signal of representing first receiver transmits with respect to signal source, t ₁The time difference when reception signal of second receiver of expression transmits with respect to signal source, t ₂The multipath time difference when reception signal of second receiver of expression transmits with respect to signal source; T is set in this example ₀=0, t ₁=-20, t ₂=-30, g ₂₁=1, g ₂₂=0.8;

The flow process of the specific embodiment of the invention is following:

Step 1. is set up and is received sample of signal:

The maximum that the receiver 1,2 that two of choosing are carried out time difference measurement receives the expection time difference between the signal, two paths of signals of same signal source emission is 30 chronomeres; The theoretical time difference of present embodiment is 20 chronomeres; After receiver 1,2 carries out analog-to-digital conversion respectively to the received signal; Present embodiment adopts the expection time difference peaked 100 times (i.e. 3000 chronomeres) to set sampling time interval, carry out synchronized sampling, gets the sample of two-way received signal 1,2;

Confirming of step 2. residual error

2.1. auto-correlation processing:

Two groups of sampled signals to receiver receives are carried out the auto-correlation computation processing respectively, obtain corresponding autocorrelation matrix:

$R=\underset{t=4}{\overset{L}{\mathrm{\&Sigma;}}}{\left[\begin{array}{c}{x}_1(t-1)\\ x_1(t-2)\\ x_1(t-3)\end{array}\right]}^{*}\left[\begin{array}{ccc}{x}_1\left(t\right)& x_1(t-1)& x_1(t-2)\end{array}\right]$

Wherein: x ₁(t), t=1,2 ..., L representes the sampled signal of first receiver, and L representes sampling time interval, and for reducing amount of calculation, sampling time interval is elected peaked 100 times of the expection time difference as, and L=3000 in this execution mode, ∑ represent summation;

2.2. confirm auto-regressive parameter:

Through the autocorrelation matrix that obtains in the step 2.1, utilize residual sum noise signal self Gaussian distribution and separate characteristic between the two, obtain following formula:

$\left[\begin{array}{ccc}1& -{{\mathrm{\&alpha;}}_1}^{*}& -{{\mathrm{\&alpha;}}_2}^{*}\end{array}\right]R\left[\begin{array}{c}1\\ -{\mathrm{\&alpha;}}_1\\ -{\mathrm{\&alpha;}}_2\end{array}\right]=0$

Based on following Singular Value Decomposition Using theorem: for any order is m * n rank matrix A of r, all exists (to descend) triangular matrix R (L) on unitary matrice U, V and the r rank, makes $A=\mathrm{<figure-callout\; id="0"\; label="U\; R"\; filenames="HDA00002033437300011.png,HDA00002033437300012.png"\; state="\{\{state\}\}">U</figure-callout>}\left(\begin{array}{c}R\end{array}\right)\left(\begin{array}{cc}& 0\\ 0& 0\end{array}\right)V$ Or $A=\mathrm{<figure-callout\; id="0"\; label="U"\; filenames="HDA00002033437300011.png,HDA00002033437300012.png"\; state="\{\{state\}\}">U</figure-callout>}\left(\begin{array}{cc}0& 0\\ 0& L\end{array}\right)V;$ Matrix R is carried out singular value decomposition:

R=USV

In this execution mode:

$U=\left[\begin{array}{ccc}-0.0666& 0.9168& 0.3938\\ -0.4978& 0.3115& -0.8094\\ -0.8647& -0.2499& 0.4356\end{array}\right],$ $S=\left[\begin{array}{ccc}18750.7& 0& 0\\ 0& 16285.5& 0\\ 0& 0& 29.8\end{array}\right],$ $V=\left[\begin{array}{ccc}0.8988& -0.0642& 0.4336\\ 0.4198& 0.4106& -0.8094\\ -0.1261& 0.9096& 0.3960\end{array}\right];$

The auto-regressive parameter vector is included in the corresponding singular vector [1-α] of zero singular value of matrix R ^TIn, α=[α wherein ₁α ₂], α ₁, α ₂Represent single order and second order auto-regressive parameter value respectively; Choose the most approaching zero singular value 29.8 pairing characteristic vectors [0.4336-0.8094 0.3960] in this execution mode ^T, in order to satisfy parameter setting in the autoregression method, to carry out obtaining auto-regressive parameter vector [1-α] after normalization is handled ^T=[1-1.8665 0.9131] ^T, wherein α=[1.8665-0.9131] is auto-regressive parameter;

2.3. the residual error of obtaining:

Single order and second order auto-regressive parameter α with step 2.2. gained ₁=1.8665, α ₂In=-0.9131 substitution residual error expression formula as follows:

Δx ₁(t)=x ₁(t)-α ₁x ₁(t-1)-α ₂x ₁(t-2)

Δx ₂(t)=x ₂(t)-α ₁x ₂(t-1)-α ₂x ₂(t-2)

Wherein, x ₁(t) and x ₂(t) be the sampled signal of two receivers, x ₁(t-1) and x ₂(t-1) be the measuring-signal of the previous chronomere of two receiver current time t, x ₁(t-2) and x ₂(t-2) be the measuring-signal of preceding two chronomeres of two receiver current demand signals, Δ x ₁(t) and Δ x ₂(t) be the residual error of two paths of signals 1,2;

Confirming of step 3. time difference

3.1. obtain the coherence spectra of the residual error of two paths of signals 1,2:

To Δ x ₂(t), Δ x ₁(t) carry out computing cross-correlation, utilize the separate character of receiver noise can get following formula:

$r_{{\mathrm{\&Delta;x}}_2\left(t\right){\mathrm{\&Delta;x}}_1\left(t\right)}\left(k\right)=E\left[{\mathrm{\&Delta;x}}_2\left(t\right){{\mathrm{\&Delta;x}}_1}^{*}(t-k)\right]$

$=E[g_{21}v(t-t_1)+g_{22}v(t-t_2)+n_2(t-k)-{\mathrm{\&alpha;}}_1{n}_2(t-1)-{\mathrm{\&alpha;}}_2{n}_2(t-2)){(t-k-t_0)}^{*}]$

$=g_{21}E\left[v(t-t_1)v^{*}(t-k-t_0)\right]+g_{22}E\left[v(t-t_2)v{(t-k-t_0)}^{*}\right]$

$=g_{21}{r}_{\mathrm{vv}}(k-(t_1-t_0))+g_{22}{r}_{\mathrm{vv}}(k-(t_2-t_0))$

Wherein: r _Vv(k)=Ev (t) v ^*(t-k)] auto-correlation function of expression v (t),

Promptly represent Δ x ₂(t), Δ x ₁(t) the residual error coherence spectra between; The value of the coherence spectra of residual error is:

${\hat{r}}_{{\mathrm{\&Delta;x}}_2\left(t\right){\mathrm{\&Delta;x}}_1\left(k\right)}\left(k\right)=\left\{\begin{array}{cc}\frac{1}{L+k}\underset{t=1}{\overset{L+k}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;x}}_2\left(t\right){{\mathrm{\&Delta;x}}_1}^{*}(t-k),& -L+1\&le;k\&le;0\\ \frac{1}{L-k}\underset{t=k+1}{\overset{L}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;x}}_2\left(t\right){{\mathrm{\&Delta;x}}_1}^{*}(t-k),& L-1\&GreaterEqual;k>0\end{array}\right.$

Wherein

is the estimated value of the cross-correlation function

of residual error; L representes sampling time interval, and ∑ is represented summation.

3.2. confirm the time difference of two paths of signals: receiver 1,2 receives the signal of same signal source emission, and two paths of signals pairing time of largest peaks in the residual error coherence spectra is the time difference of two-way with source signal; This time difference is the time difference that two receivers 1,2 are received the signal of same signal source emission;

Fig. 1 measures design sketch for adopting the basic cross-correlation method of background technology that the time difference between the two paths of signals is carried out emulation under the same conditions; Fig. 2 is this execution mode the time difference between the two paths of signals is carried out emulation mensuration design sketch

As can be seen from the figure: the broad sense coherence spectra curve chart that adopts background technology broad sense cross-correlation method to obtain among Fig. 1; The spectrum peak broad (summit is more level and smooth) of broad sense coherence spectra, the accuracy that maximal peak point is confirmed are relatively poor, and-20 chronomeres that the corresponding time difference value of peak-peak is about-24 chronomeres, deviation theory value reach 4 chronomeres; And the corresponding time difference value of peak-peak is-20 chronomeres in the coherence spectra of this execution mode of Fig. 2 residual error, and its time difference value of surveying conforms to theoretical value.

Claims (2)

1. One kind under multi-path environment to the assay method of the source signal time difference, comprising:

   Step 1. is set up the received signal sample: at first confirm two receivers 1,2 that carry out time difference measurement; Receive the signal of same signal source emission when two receivers after, utilize analog-digital converter respectively the analog signal conversion of receiver 1,2 outputs to be data signal; Then the two ways of digital signals after the conversion is carried out synchronized sampling at interval according to the peaked multiple setting-up time of the expection time difference between the two paths of signals, the sample of two-way received signal 1,2;

   Confirming of step 2. residual error

   2.1. auto-correlation processing: according to background technology step 1 gained 1,2 two-way sampled signals are carried out auto-correlation processing, obtain autocorrelation matrix, again matrix is carried out singular value decomposition, obtain its singular value and corresponding eigenvectors matrix;

   2.2. confirm auto-regressive parameter: the step 2.1 gained zero pairing characteristic vector of singular value is carried out normalization handle, thereby obtain each the rank auto-regressive parameter in the autoregression method;

   2.3. residual error of obtaining: in normalization gained auto-regressive parameter substitution following formula in the step 2.2:

   ${\mathrm{\&Delta;x}}_1\left(t\right)=x_1\left(t\right)-\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_m{x}_1(t-m)$

   ${\mathrm{\&Delta;x}}_2\left(t\right)=x_2\left(t\right)-\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_m{x}_2(t-m)$

   Obtain the residual delta x of two paths of signals 1,2 respectively ₁(t) and Δ x ₂(t), wherein: x ₁(t) signal source of receiving at current time t for first receiver is at time point t-t ₀The same source signal that sends, x ₂(t) be second receiver in same signal source that current time t receives respectively at time point t-t ₁And t-t ₂The mixed signal of the same source signal that sends, α _mRepresent m rank auto-regressive parameter, ∑ is represented summation;

   Confirming of step 3. time difference

   3.1. obtain the coherence spectra of two paths of signals 1,2 residual errors: the residual error according to gained two paths of signals in the step 2.3 is passed through following formula:

   $r_{{\mathrm{\&Delta;x}}_2\left(t\right){\mathrm{\&Delta;x}}_1\left(t\right)}\left(k\right)=E\left[{\mathrm{\&Delta;x}}_2\left(t\right){{\mathrm{\&Delta;x}}_1}^{*}(t-k)\right]$

   Carry out cross correlation process, obtain the coherence spectra of the residual error of two paths of signals; Δ x wherein ₁(t) with Δ x ₂(t-k) represent the residual error of two paths of signals 1,2 respectively, t representes the current time, and t-k representes the time of k unit interval before the current time,

   

   Expression Δ x ₁(t) with Δ x ₂(t) cross-correlation function between; The value of the coherence spectra of residual error is determined by following formula:

   ${\hat{r}}_{{\mathrm{\&Delta;x}}_2\left(t\right){\mathrm{\&Delta;x}}_1\left(t\right)}\left(k\right)=\left\{\begin{array}{cc}\frac{1}{L+k}\underset{t=1}{\overset{L+k}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;x}}_2\left(t\right){{\mathrm{\&Delta;x}}_1}^{*}(t-k),& -L+1\&le;k\&le;0\\ \frac{1}{L-k}\underset{t=k+1}{\overset{L}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;x}}_2\left(t\right){{\mathrm{\&Delta;x}}_1}^{*}(t-k),& L-1\&GreaterEqual;k>0\end{array}\right.$

   Wherein: is cross-correlation function

   

   value of residual error; L representes sampling time interval, and ∑ is represented summation;

   3.2. confirm the time difference of two paths of signals: the pairing time value of peak-peak is the time difference of two paths of signals in the coherence spectra of step 3.1 gained two-way sampled signal residual error; This time difference is the time difference that two receivers 1,2 are received the signal of same signal source emission.
2. 2. by the said assay method that under multi-path environment, is directed against with the source signal time difference of claim 1; It is characterized in that described in the step 1 carrying out synchronized sampling at interval according to the peaked multiple setting-up time of the expection time difference between the two paths of signals, its sampling time interval is not less than 10 times of greatest expected time difference between the two paths of signals.

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