CN103941267A - Satellite navigation deception interference suppression method combined with denoising and DOA estimation - Google Patents

Abstract

The invention relates to a satellite navigation deception interference suppression method combined with denoising and DOA estimation. The method includes the following sequentially-executed steps that (1), radio-frequency signals received by an array antenna are converted into digital intermediate-frequency signals; (2), an array signal covariance matrix is constructed, and power of noise is estimated to remove a noise component in the covariance matrix; (3), the coming direction of a deception interference source is estimated; (4) deception interference is suppressed. According to the satellite navigation deception interference suppression method combined with denoising and DOA estimation, spatial features of the deception interference are used and combined with a beam forming technology and an interference orthocomplement space projection technology so that the deception interference can be suppressed, satellite signals known to be real and coming direction information of the deception interference are not needed, an inertial navigation auxiliary unit is not needed, and the satellite navigation deception interference suppression method is easy to implement.

Description

The satellite navigation deception formula disturbance restraining method that a kind of combination denoising and DOA estimate

Technical field

The invention belongs to satellite navigation Anti-Jamming Technique field, particularly relate to the satellite navigation deception formula disturbance restraining method that a kind of combination denoising and DOA estimate.

Background technology

Due to GPS (Global Position System) (Global Navigation Satellite System, guide number SS) can provide time/space reference and all real-time dynamic informations relevant to position, thereby be widely applied at aspects such as navigation, time service, precision measurements, therefore guarantee that the security of GPS (Global Position System) is particularly important.But while arriving ground due to GNSS signal, signal power is very faint, so GNSS receiver is very easily interfered.The existence of disturbing will make GNSS receiver cisco unity malfunction, therefore studies GNSS Anti-Jamming Technique and has very important significance.

At present, about the research of GNSS disturbance restraining method, mainly concentrate on briquettability disturbance restraining method, but relatively less to the research of deception formula disturbance restraining method.Different from briquettability interference, deception formula is disturbed and is referred to the jammer transmitting undesired signal identical or similar with real satellite navigation signal, and guiding satellite navigation receiver occurs locating mistake, and required jamming power is little, and disguised strong, interference effect is good.In the last few years, deception formula is disturbed the important threat that becomes gradually satellite navigation system.

In recent years, Chinese scholars is all being found the effective way of disturbing inhibition for deception formula always, for deception formula, disturb the effective ways that suppress to mainly contain receiver-autonomous dependent surveillance (Receiver Autonomous Integrity Monitoring is called for short RAIM) technology and multi-antenna technology at present.Although can detecting and get rid of by deception formula, RAIM technology disturbs the abnormal measured value causing, but RAIM technology is just effective when only there is one or two abnormal measured value, when deception formula disturbs the abnormal measured value causing to be in the great majority, this technology can be got rid of the measured value of actual signal on the contrary.U.S. Rockwell Collins company proposes a kind of method of utilizing array antenna to suppress cheating interference, this method according to receiver the information after to every Satellite Tracking estimate satellite-signal to, and coming of therefrom identifying that deception formula disturbs to, finally in deception formula, disturb and carry out antenna zeroing to direction, to suppress deception formula, disturb, but this method needs the feedback information of receiver, and complex structure, and operand is large.

Summary of the invention

In order to address the above problem, the object of the present invention is to provide a kind of combination denoising of deception formula interference and satellite navigation deception formula disturbance restraining method of DOA estimation that can effectively suppress for satellite navigation.

In order to achieve the above object, the satellite navigation deception formula disturbance restraining method that combination denoising provided by the invention and DOA estimate comprises the following step carrying out in order:

(1) by array antenna received to radiofrequency signal convert digital medium-frequency signal to;

(2) structure array signal covariance matrix, the power of estimating noise, removes the noise contribution in covariance matrix;

(3) estimate deception formula interference source come to;

(4) deception formula is disturbed and suppressed.

In described step (1) by array antenna received to radiofrequency signal convert digital medium-frequency signal to and completed by down conversion module, down conversion module is comprised of low noise radio frequency amplifier, frequency mixer and automatic gain control circuit.

Structure array signal covariance matrix in described step (2), the power of estimating noise, the method of removing the noise contribution in covariance matrix is that the digital medium-frequency signal that obtains according to step (1) first calculates covariance matrix and obtains the mean value of the elements in a main diagonal of covariance matrix, then the mean value of the elements in a main diagonal of covariance matrix is multiplied by unit matrix, structure diagonal matrix, finally deducts diagonal matrix with covariance matrix and obtains removing the covariance matrix after noise contribution.

Estimate in described step (3) deception formula interference source to method be the corresponding angle in top by search wave beam obtain cheating formula interference source to.

In described step (4) to deception formula disturb the method suppress be according to the estimated deception formula interference source of step (3) to first estimating deception formula interference space, and then calculate the deception formula interference orthogonal complement space; The data that array received is arrived, to disturbing orthogonal complement space projection to suppress interference, are finally got the data after any road projection and send into conventional satellite navigation neceiver.

The satellite navigation deception formula disturbance restraining method that combination denoising provided by the invention and DOA estimate is the space characteristics that utilizes deception formula to disturb, in conjunction with beam-forming technology and interference orthogonal complement space shadow casting technique, realize the inhibition that deception formula is disturbed, do not need coming to information of known true satellite-signal and the interference of deception formula, and without inertial navigation auxiliary unit, realize simple.

Accompanying drawing explanation

Fig. 1 is the satellite navigation deception formula disturbance restraining method process flow diagram that combination denoising provided by the invention and DOA estimate.

Fig. 2 is the noise power estimated in array received data in the inventive method and the comparison diagram of simulator and noise power.

Fig. 3 be in the inventive method, utilize beam-forming technology estimate deception formula interference source come to beam pattern.

Fig. 4 is the array pattern that the inventive method obtains all satellite-signals.

Fig. 5 does not take the inventive method to suppress the result of catching of deception formula interference.

Fig. 6 takes the inventive method to suppress the result of catching of deception formula interference.

Fig. 7 is the two-dimensional search result to PRN1 while not taking the inventive method to suppress the interference of deception formula.

Fig. 8 is the two-dimensional search result to PRN1 while taking the inventive method to suppress the interference of deception formula.

Embodiment

With specific embodiment, the satellite navigation deception formula disturbance restraining method of combination denoising provided by the invention and DOA estimation is elaborated with reference to the accompanying drawings.For convenience's sake, take GPS(Global Positioning System below) uniform line-array that forms of system and N array element is illustrated as example.

As shown in Figure 1, combination denoising provided by the invention and DOA(Direction of arrival, time of arrival) the satellite navigation deception formula disturbance restraining method estimated comprises the following step carrying out in order:

(1) by array antenna received to radiofrequency signal convert digital medium-frequency signal to:

Deceiving jamming is comprised of and transmitting in the same direction the forward signal of many real satellite signals, for jamming target receiver effectively, the power of the forward signal of every real satellite signal is slightly stronger than the power of real satellite signal, and the be superimposed power of the single deceiving jamming that forms of the forward signal of many real satellite signals is higher than the power of single real satellite signal.When single deceiving jamming incides on array, the intermediate-freuqncy signal that GPS receiver antenna battle array receives is:

$x\left(n{T}_s\right)=\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{a}_m{s}_m^a\left(n{T}_s\right)+b{j}^s\left(n{T}_s\right)+n\left(n{T}_s\right)---\left(1\right)$

Wherein, M represents the number of real satellite signal; a _ma (θ _m) write a Chinese character in simplified form, represent the steering vector of m real satellite signal, θ _mrepresent coming to angle of m real satellite signal,

$a_m=a\left({\mathrm{\θ}}_m\right)={\left[\begin{array}{cccc}1& e^{-j\frac{2\mathrm{\π}}{\mathrm{\λ}}d\sin {\mathrm{\θ}}_m}& L& e^{-j(N-1)\frac{2\mathrm{\π}}{\mathrm{\λ}}d\sin {\mathrm{\θ}}_m}\end{array}\right]}^T---\left(2\right)$

B is b (θ _s) write a Chinese character in simplified form, represent the steering vector of deception formula interference source, θ _srepresent coming to angle of deception formula interference source,

$b=b\left({\mathrm{\θ}}_s\right)={\left[\begin{array}{cccc}1& e^{-j\frac{2\mathrm{\π}}{\mathrm{\λ}}d\sin {\mathrm{\θ}}_s}& L& e^{-j(N-1)\frac{2\mathrm{\π}}{\mathrm{\λ}}d\sin {\mathrm{\θ}}_s}\end{array}\right]}^T---\left(3\right)$

λ in formula (2) and formula (3) represents satellite-signal wavelength, and d represents array element distance.N (nT _s) be additive white Gaussian noise, suppose that noise is independent, uncorrelated with the interference of deception formula with actual signal, T _sfor sampling interval. (nT _s) m real satellite navigation signals of expression, j ^s(nT _s) represent that the satellite navigation signals sum of many forwardings, subscript a and s indicate respectively actual signal and deception formula to disturb.Wherein:

$s_m^a\left(n{T}_s\right)=\sqrt{p_m^a}{D}_m^a(n{T}_s-{\mathrm{\τ}}_m^a)c_m^a(n{T}_s-{\mathrm{\τ}}_m^a)e^{j{\mathrm{\φ}}_m^a+j2\mathrm{\π}{f}_m^{\′a}n{T}_s}---\left(4\right)$

$j^s\left(n{T}_s\right)=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}\sqrt{p_l^s}{D}_l^s(n{T}_s-{\mathrm{\τ}}_l^s)c_l^s(n{T}_s-{\mathrm{\τ}}_l^s)e^{j{\mathrm{\φ}}_l^s+j2\mathrm{\π}{f}_l^{\′s}n{T}_s}---\left(5\right)$

φ, f ', p and τ represent respectively to receive phase place, Doppler frequency, power and the code time delay of signal.D (nT _s) and c (nT _s) represent respectively navigation message and C/A code.Because deceiving jamming includes the forward signal of many real satellite signals, the L in formula (5) represents the satellite-signal number of the forwarding that cheating interference source comprises.

(2) structure array signal covariance matrix, the power of estimating noise, remove the noise contribution in covariance matrix:

First calculate the covariance matrix that receives signal, that is:

$R=E\left\{x\left(n{T}_s\right)x^H\left(n{T}_s\right)\right\}=\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{p}_m^a{a}_m{a}_m^H+\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{p}_l^{s}b{b}^H+{\mathrm{\σ}}^{2}I---\left(6\right)$

Wherein, σ ²represent noise power.

Then the power of noise in estimate covariance matrix.The power of actual signal is conventionally than the low 20dB of noise level left and right, and the power that deception formula is disturbed is a little more than the power of actual signal, conventional beam-forming technology cannot be from covariance matrix direct estimation coming of going out that deception formula disturbs to, need to from sample covariance matrix R, noise contribution be removed just can estimate deception formula interference source come to.Due to noise Gaussian distributed and separate, noise contribution in covariance matrix can be expressed as the product of noise power and unit matrix, mainly concentrate on the elements in a main diagonal of covariance matrix, therefore from covariance matrix, deduct a unit matrix very approaching with noise power level, can remove the noise contribution in covariance matrix.Because the power of noise is far longer than the power of actual signal and the power that deception formula is disturbed, the power level of unit matrix can be determined by the mean value ζ of the main diagonal element of covariance matrix, that is:

ζ=tr.(R)/N （7）

Removing noise contribution covariance matrix is afterwards designated as

$\tilde{R}=R-\mathrm{\ζI}---\left(8\right)$

(3) estimate deception formula interference source come to:

The sample covariance matrix of removing after noise power is carried out to wave beam formation, and by the position at search top determine deception formula interference source to

${\widehat{\mathrm{\θ}}}_s=\underset{\mathrm{\θ}}{\max \arg }{h}^H\left(\mathrm{\θ}\right)\tilde{R}h\left(\mathrm{\θ}\right)---\left(9\right)$

Wherein, the steering vector that h (θ) is even linear array.

(4) deception formula is disturbed and is suppressed:

Coming to, the steering vector structure deception formula interference space P being disturbed by deception formula of the deception formula interference source of estimating according to beamforming algorithm:

$P=h\left({\widehat{\mathrm{\θ}}}_s\right)[h^H\left({\widehat{\mathrm{\θ}}}_s\right)h\left({\widehat{\mathrm{\θ}}}_s\right){]}^{-1}{h}^H\left({\widehat{\mathrm{\θ}}}_s\right)---\left(10\right)$

According to Theory of Projections, just can find the orthogonal intersection cast shadow matrix of deception formula interference space, by receiving signal and being projected in, in the orthogonal complement space of cheating interference, eliminate deception formula and disturb.The orthogonal intersection cast shadow matrix that can be obtained the interference of deception formula by formula (10) is:

$P_{\⊥}=I-h\left({\widehat{\mathrm{\θ}}}_s\right)[h^H\left({\widehat{\mathrm{\θ}}}_s\right)h\left({\widehat{\mathrm{\θ}}}_s\right){]}^{-1}{h}^H\left({\widehat{\mathrm{\θ}}}_s\right)---\left(11\right)$

To deception formula, disturb orthogonal complement space projection to carry out projection array received signal.The data of disturbing without deception formula after projection are:

$\begin{array}{c}y\left(n{T}_s\right)=P_{\⊥}x\left(n{T}_s\right)=P_{\⊥}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{a}_m{s}_m^a\left(n{T}_s\right)+P_{\⊥}b{j}^s\left(n{T}_s\right)+P_{\⊥}n\left(n{T}_s\right)\\ \≈P_{\⊥}\underset{m=1}{\overset{N_a}{\mathrm{\Σ}}}{a}_m{s}_m^a\left(n{T}_s\right)+P_{\⊥}n\left(n{T}_s\right)\end{array}---\left(12\right)$

In formula (12), deception formula disturbs the derivation of inhibition part as follows:

$P_{\⊥}b=b-h\left({\widehat{\mathrm{\θ}}}_s\right){\left[h^H\left({\widehat{\mathrm{\θ}}}_s\right)h\left({\widehat{\mathrm{\θ}}}_s\right)\right]}^{-1}{h}^H\left({\widehat{\mathrm{\θ}}}_s\right)b=b-\mathrm{\ρh}\left({\widehat{\mathrm{\θ}}}_s\right)---\left(13\right)$

Wherein, if it is enough accurate to estimate, so normalized correlation coefficient ρ ≈ 1, i.e. P _⊥b ≈ 0.

Finally get the data after any road projection and send into conventional satellite navigation neceiver.

Fig. 2 adopts the noise power estimated in array received data in the inventive method and the comparison diagram of simulator and noise power.In the present embodiment, noise power σ ²=-120dBW.In Fig. 2, solid black lines represents noise power level, and broken line represents the noise power level that the present invention is estimated, and the noise power that the inventive method is estimated as can be seen from Figure 2 and the noise power level of setting approach.

Fig. 3 be in the inventive method, utilize beam-forming technology estimate deception formula interference source come to beam pattern.In the present embodiment, antenna array is ten yuan of even linear arrays, four gps satellite signal PRN1, PRN3, PRN22, PRN25 is respectively from 0 °, 50 ° ,-25 °, 55 ° of directions incide on array, a deception formula interference source (comprises four gps satellite signal PRN1, PRN2, PRN3, the forward signal of PRN14) from 35 ° of directions, incide array, in Fig. 3 black dotted lines represent cheating interference source come to, solid black lines represents real satellite direction of signal.The inventive method can be in cheating interference source be come to forming beam peak as can be seen from Figure 3, can estimate exactly deception formula disturb to.

Fig. 4 is the array pattern that the inventive method obtains all satellite-signals.In the present embodiment, antenna array is 10 yuan of even linear arrays, four gps satellite signal PRN1, PRN3, PRN22, PRN25 is respectively from 0 °, 50 °,-25 °, 55 ° of directions incide on array, and a deception formula interference source (comprises four gps satellite signal PRN1, PRN2, PRN3, the forward signal of PRN14) from 35 ° of directions, incide array.In Fig. 4 black dotted lines represent cheating interference source come to.The inventive method only forms very dark zero falling in deception formula interference source direction as can be seen from Figure 4, disturb, and in other direction, gain is more smooth, can guarantee passing through of real satellite signal thereby suppress deception formula.

Fig. 5 does not take the inventive method to suppress the result of catching of deception formula interference, in Fig. 5, horizontal ordinate represents gps satellite No. PRN, and ordinate represents the normalized factor of catching, and it is defined as the ratio of normalized correlation peak maximal value and correlation peak second largest value in receiver acquisition part.In the present embodiment, antenna array is 10 yuan of even linear arrays, four gps satellite signal PRN1, PRN3, PRN22, PRN25 is respectively from 0 °, 50 °,-25 °, 55 ° of directions incide on array, and a deception formula interference source (comprises four gps satellite signal PRN1, PRN2, PRN3, the forward signal of PRN14) from 35 ° of directions, incide array.If being the normalized factor of catching, detection threshold equals 0.2.Receiver acquisition, to six satellites, wherein includes deception satellite as can be seen from Figure 5.

Fig. 6 takes the inventive method to suppress the result of catching of deception formula interference, and the coordinate axis implication of Fig. 6 is the same with Fig. 5, and detection threshold is also identical.In the present embodiment, antenna array is 10 yuan of even linear arrays, four gps satellite signal PRN1, PRN3, PRN22, PRN25 is respectively from 0 °, 50 °,-25 °, 55 ° of directions incide on array, and a deception formula interference source (comprises four gps satellite signal PRN1, PRN2, PRN3, the forward signal of PRN14) from 35 ° of directions, incide array.This method successfully curbs the interference of deception formula as can be seen from Figure 6, and receiver only captures real satellite.

Fig. 7 is the two-dimensional search result of PRN1 while not taking the inventive method to suppress the interference of deception formula, can obviously observe the correlation peak that exists real satellite signal and deception formula to disturb.

Fig. 8 is the two-dimensional search result of PRN1 while taking the inventive method to suppress the interference of deception formula, and after can finding out that adopting the inventive method to suppress deception formula disturbs, the correlation peak that deception formula is disturbed is effectively suppressed.

Claims (5)

1. in conjunction with a satellite navigation deception formula disturbance restraining method for denoising and DOA estimation, it is characterized in that: described inhibition method comprises the following step carrying out in order:

(1) by array antenna received to radiofrequency signal convert digital medium-frequency signal to;

(2) structure array signal covariance matrix, the power of estimating noise, removes the noise contribution in covariance matrix;

(3) estimate deception formula interference source come to;

(4) deception formula is disturbed and suppressed.

2. the satellite navigation deception formula disturbance restraining method that combination denoising according to claim 1 and DOA estimate, it is characterized in that: in described step (1) by array antenna received to radiofrequency signal convert digital medium-frequency signal to and completed by down conversion module, down conversion module is comprised of low noise radio frequency amplifier, frequency mixer and automatic gain control circuit.

3. the satellite navigation deception formula disturbance restraining method that combination denoising according to claim 1 and DOA estimate, it is characterized in that: structure array signal covariance matrix in described step (2), the power of estimating noise, the method of removing the noise contribution in covariance matrix is that the digital medium-frequency signal that obtains according to step (1) first calculates covariance matrix and obtains the mean value of the elements in a main diagonal of covariance matrix, then the mean value of the elements in a main diagonal of covariance matrix is multiplied by unit matrix, structure diagonal matrix, finally with covariance matrix, deduct diagonal matrix and obtain removing the covariance matrix after noise contribution.

4. the satellite navigation deception formula disturbance restraining method that combination denoising according to claim 1 and DOA estimate, is characterized in that: in described step (3), estimate deception formula interference source to method be the corresponding angle in top by search wave beam obtain cheating formula interference source next to.

5. the satellite navigation deception formula disturbance restraining method that combination denoising according to claim 1 and DOA estimate, it is characterized in that: in described step (4) to deception formula disturb the method suppress be according to the estimated deception formula interference source of step (3) to first estimating deception formula interference space, and then calculate the deception formula interference orthogonal complement space; The data that array received is arrived, to disturbing orthogonal complement space projection to suppress interference, are finally got the data after any road projection and send into conventional satellite navigation neceiver.