CN103293518A - Positioning and detection method of radiation source outside broadcast signals - Google Patents

Abstract

The invention provides a positioning and detection method of a radiation source outside broadcast signals. The feature of statistical independence between target echo signals and co-channel interferences is utilized, the co-channel interferences are stripped out, and accordingly the purpose of suppressing the co-channel interferences is achieved. Meanwhile, since correlation between the target echo signals and direct wave signals is low, the direct wave signals can be determined to have the feature of statistical independence approximately. According to the detection method compared with a traditional processing method, adaptive cancellation of main channel signals is omitted, the direct wave signals can also be stripped out, and accordingly saving computation is achieved.

Description

Broadcast singal external radiation source position finding and detection method

Technical field

The present invention relates to the fm broadcast signal treatment technology, be specifically related to strong co-channel interference is suppressed and extracts the technology of echo signal.

Background technology

The bistatic radar technology refers to utilize transmitter and receiver not in the advantage in same place, so as to improve receiving station disguise, obtain bigger target forward direction area, reduce the shadow region to the technology of electromagnetic wave attenuation.Passive radar system based on the external radiation source can utilize common civil signal as irradiation source, active signal of the digital television signal in the daily life, frequency modulation broadcasting FM signal, mobile communication GSM signal, enemy etc. for example, its systematic schematic diagram as shown in Figure 1, radar is to receiving direct wave, the echo of moving target, the direct wave of other common-frequency broadcasting launching tower transmission and the echo of other object reflection that including of signal comes from broadcast emission tower itself, such as the still life echo of various buildings reflections.Therefore, the target echo signal that radar receives in the signal is extremely faint, and is submerged in the various interference.

The tradition externally detection method of radiant source target signal is to receive the direct wave signal with reference channel, and main antenna receives multiple signals, comprising direct wave signal, target echo signal and noise and interference.At first adopt normalization minimum mean-square NLMS algorithm that direct wave is carried out adaptive cancellation with main channel signal and reference channel signal, by airspace filter co-channel interference is suppressed again, adopt time-frequency two-dimensional associated extraction target time delay, Doppler frequency at last.

But bistatic radar in actual applications, the most direct problem just is based on the method how the external radiation source radar system of frequency modulation broadcasting FM signal more effectively suppresses co-channel interference, the co-channel interference signal that particularly ought receive is in antenna main beam, or under the situation about being entered by antenna side lobe, more increased the difficulty of target detection.Since disturb and target echo signal, overlapping in frequency domain, and in the spatial domain, also can't adopt the method for digital beam formation that it is suppressed, so the disposal route of traditional external radiation source radar signal can't satisfy the requirement that detects target echo.

Summary of the invention

Technical matters to be solved by this invention is that the external radiation source radar that is provided at based on frequency modulation broadcasting FM signal exists under the situation of co-channel interference, can effectively peel off the broadcast singal external radiation source position finding and detection method of target and interference.

The present invention solves the problems of the technologies described above the technical scheme that adopts to be, broadcast singal external radiation source position finding and detection method may further comprise the steps:

Step 1: the take over party carries out bandpass sampling to the pending main channel frequency modulation broadcasting FM signal that receives and obtains sample sequence x (t), and t represents sampling instant;

Step 2: the autocorrelation matrix R that asks sample sequence x (t) _x

Step 3: to autocorrelation matrix R _xCarry out svd SVD and obtain R _x=U Λ U ^H, utilize to decompose the diagonal matrix Λ that obtains and the sample sequence x of unitary matrix U (t) carry out linear transformation obtain receiving signal from strong to weak arrangement y (t),

Y (t)=[y wherein ₁(t) y ₂(t) ... y _M(t)] ^T, M is receiving antenna array element number, T representing matrix transposition;

Step 4: the sample sequence y (t) after the linear transformation is asked delay autocorrelation matrix R _y, to the feasible autocorrelation matrix R that postpones of the selection that postpones _yIn each eigenwert do not coincide;

Step 5: to postponing autocorrelation matrix R _yDo the SVD decomposition and obtain R _y=W Λ W ^H, the sample sequence y of unitary matrix W (t) that utilizes decomposition to obtain handles the signal z (t) that obtains disturbing after suppressing to handle, z (t)=W ^HY (t)=W ^HΛ ^-1/2U ^HX (t), z (t)=[z ₁(t) z ₂(t) ... z _M(t)] ^T

Step 6: will disturb among the signal z (t) after suppress handling the 3 the road to M road signal respectively with the 1 road signal z ₁(t) do the time-frequency distributions two-dimensional correlation and obtain corresponding correlation | Ψ _i(τ, f) | _,

I=3 ..., M, L are bandpass sampling length, τ is time delay, f Doppler shift;

Step 7: respectively in the two-dimensional correlation value of 3 to M each road signal correspondence | Ψ _i(τ, f) | in search plain peak point, with the time delay of each road signal peak value point correspondence and Doppler shift as a useful signal, calculate each road signal to noise ratio (S/N ratio), as a certain time delay and Doppler shift place signal to noise ratio (S/N ratio) during more than or equal to threshold value, time delay and the Doppler shift that time delay and the Doppler of its peak point correspondence is defined as a target frequently then, otherwise judge in this road signal and do not have target.

The present invention utilizes target echo signal and co-channel interference to add up independently characteristic, separates co-channel interference, thereby reaches the purpose that co-channel interference is suppressed.Simultaneously, because the correlativity of target echo signal and direct wave signal is less, it also has adds up independently character for thinking of can being similar to, than traditional treatment method, the present invention does not need to carry out adaptive cancellation to receiving main channel signal, also the direct wave signal can be peeled off, thereby play the effect of saving operand.

The invention has the beneficial effects as follows, can play the effect of inhibition to co-channel interference in the same wave beam, and then reach better detection performance.

Description of drawings

Fig. 1 is the system principle synoptic diagram based on location, broadcasting external radiation source.

Fig. 2 is signal processing flow figure of the present invention.

Fig. 3 is classic method signal interference ratio gain diagram.

Fig. 4 is the inventive method signal interference ratio gain diagram.

Fig. 5 is time-frequency two-dimensional correlogram time delay dimension (target decay-60dB, the interference attenuation-20dB) of classic method echo signal.

Fig. 6 is time-frequency two-dimensional correlogram time delay dimension (target decay-60dB, the interference attenuation-20dB) of the inventive method echo signal.

Fig. 7 is time-frequency two-dimensional correlogram frequency dimension (target decay-60dB, the interference attenuation-20dB) of classic method echo signal.

Fig. 8 is time-frequency two-dimensional correlogram frequency dimension (target decay-60dB, the interference attenuation-20dB) of the inventive method echo signal.

Embodiment

Processing signals model of the present invention is as follows:

The FM modulation signal x (t) that array antenna is received carries out modeling, and the present invention is primarily aimed at baseband signal and handles.If the baseband signal (direct wave signal) after the process FM modulation of s (t) expression some broadcasting television towers emission, the angle of arrival is θ _d, through the moving-target reflection, the target echo signal that is received by bistatic radar main channel antenna is $a\left({\mathrm{\&theta;}}_1\right){\mathrm{\&alpha;}}_{1}s(t-{\mathrm{\&tau;}}_1)e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA00003270220200013.png,HDA00003270220200021.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_{1}t},...,a\left({\mathrm{\&theta;}}_M\right){\mathrm{\&alpha;}}_{2}s(t-{\mathrm{\&tau;}}_M)e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA00003270220200013.png,HDA00003270220200021.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_{M}t}$ Number, α wherein ₁..., α _MThe decay of expression target echo, τ ₁... τ _MThe time delay of expression target, f ₁..., f _MThe Doppler frequency of expression target, θ ₁..., θ _MThe angle of arrival of expression target echo signal, a (θ _i)=[1 2 π sin (θ _i) d/ λ ... 2 π sin (θ _i) (N-1) d/ λ] ^T, the expression array antenna received drives vector, wherein d represents antenna distance, λ represents signal wavelength, N represents the bay number, then by array antenna received to signal be:

$x\left(t\right)=a\left({\mathrm{\&theta;}}_d\right)s\left(t\right)+a\left({\mathrm{\&theta;}}_1\right){\mathrm{\&alpha;}}_{1}s(t-{\mathrm{\&tau;}}_1)e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA00003270220200013.png,HDA00003270220200021.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_{1}t},...,a\left({\mathrm{\&theta;}}_M\right){\mathrm{\&alpha;}}_{2}s(t-{\mathrm{\&tau;}}_M)e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA00003270220200013.png,HDA00003270220200021.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_{M}t}+a\left({\mathrm{\&theta;}}_J\right)J\left(t\right)+n\left(t\right)$

A (θ _d) s (t) represents direct wave, $a\left({\mathrm{\&theta;}}_1\right){\mathrm{\&alpha;}}_{1}s(t-{\mathrm{\&tau;}}_1)e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA00003270220200013.png,HDA00003270220200021.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_{1}t},...,a\left({\mathrm{\&theta;}}_M\right){\mathrm{\&alpha;}}_{2}s(t-{\mathrm{\&tau;}}_M)e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA00003270220200013.png,HDA00003270220200021.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_{M}t}$ Be target echo, J (t) expression is by the signal of another broadcasting television tower emission, i.e. co-channel interference signal, θ _JBe that it arrives angle (approaching with certain target angle of arrival), the thermonoise of n (t) expression receiver, then the work that will do of the present invention be to the received signal in the co-channel interference signal suppress and extraction target component.

The technical solution of the present invention implementation step comprises as shown in Figure 2:

Step 1: receiver carries out bandpass sampling to the pending main channel array FM modulation signal that receives, and obtains sample sequence x (t)=[x ₁(t) x ₂(t) ... x _M(t)] ^T, wherein M represents array number, and t represents sampling instant, and sampling length is L.Mix in each road signal of x (t) direct wave is arranged, co-channel interference, noise and target echo signal, T representing matrix transposition.

Step 2: the autocorrelation matrix R that asks sample sequence x (t) _x=E{x (t) x ^H(t) }, if the sampling time, can suppose that then sample sequence is stochastic process stably, asks statistical average can adopt seeking time on average to replace, namely like this in sampling length L $R_x=\frac{1}{L}\underset{t}{\overset{L}{\mathrm{\&Sigma;}}}x\left(t\right)x^H\left(t\right),$ H represents conjugate transpose.

Step 3: to autocorrelation matrix R _xCarry out the SVD decomposition and obtain R _x=U Λ U ^H, the diagonal matrix Λ that the utilization decomposition obtains and the x of unitary matrix U (t) carry out linear transformation and obtain y (t)=Λ ^-1/2U ^HX (t), wherein y (t)=[y ₁(t) y ₂(t) ... y _M(t)] ^T

Step 4: y (t) is asked time-delay autocorrelation matrix R _y=E{y (t) y ^H(t-τ) }, in like manner pot life postpones auto-correlation estimation statistical delay auto-correlation, namely

It is to make R that the selection that postpones τ is required _yIn each eigenwert do not coincide.

Step 5: to postponing autocorrelation matrix R _yDo the SVD decomposition and obtain R _y=W Λ W ^H, then final through disturbing signal z (the t)=W after suppressing to handle ^HΛ ^-1/2U ^HX (t), z (t)=[z ₁(t) z ₂(t) ... z _M(t)] ^TWherein, first via signal is the signal of energy maximum among the vectorial z (t), and the second road signal is energy time big signal, is respectively direct wave signal and undesired signal in this application scene, and the later signal of Third Road is target echo signal.Owing to disturb and most of energy of direct wave all is stripped in the middle of the z (t) the one the second tunnel, the signal after beginning from Third Road can equivalence be regarded as interference is suppressed, and will provide explanation in the emulation.

Step 6: adopt the time-frequency two-dimensional coherent matched filter to extract time delay and the Doppler frequency parameter of target.The M road signal that step 5 is obtained the 3 the road to M road signal and the 1 road signal z ₁(t) do time-frequency two-dimensional and be correlated with,

I=3 ..., M, (τ f) is time delay and Doppler frequency.When having target, | Ψ _i(τ, f) | can produce a peak point | Ψ _i(τ _d, f _d) |, search peak point after, calculate

Expression removes | Ψ _i(τ _d, f _d) | outer, all | Ψ _i(there are corresponding (τ in τ, f) | average if its value, is then represented target greater than the threshold value that sets in advance _d, f _d) be time delay and the Doppler frequency of target; If its value is less than threshold value, then there is not target in expression.

Embodiment 1

In the present embodiment, adopt respectively two sections statistics independently at random sound signal as modulation signal in order to produce the FM broadcast singal, with this as direct wave signal and co-channel interference in this simulating scenes, carrier frequency is 80kHz, maximum frequency deviation is ± 75kHz, sample frequency is 200kHz, and the sampling time is 1s, postpones to be chosen for a sampling delay.Only contain undesired signal and target echo signal in the mixed signal.Emulation platform operating system is WIN7, adopts MATLAB to compile.The technical scheme that adopts the present invention to propose detects target echo signal.

Jamming power be set be 0dB as a reference.The signal to noise ratio (S/N ratio) ratio of noise (target echo signal with) is set at-30dB, signal interference ratio is set at-70dB, the target angle of arrival is 0 °, target echo disturbs differential seat angle 0～10 ° of variation, the emulation signal interference ratio gains and disturbs the variation of differential seat angle with target, and adopts wave beam formation processing co-channel interference to compare with classic method, wherein, choose weighting scheme and be Chebyshev's weighting, decay to 30dB.The present invention adopts the disposal route simulation result as shown in Figure 4, and classic method as shown in Figure 3.As can be seen from the figure, when the jamming target differential seat angle greater than 1 ° situation under, signal interference ratio gain can reach a bigger value, and along with the jamming target angle increases, reach a comparatively stable value, about 100dB, and the maximum signal interference ratio gain of classic method is about 12dB.

Embodiment 2

In the present embodiment, the FM signal production method is with embodiment 1.The technical scheme that adopts the present invention to propose detects target echo signal.Below provide each simulation parameter of mixed signal, and relatively under different condition classic method and the present invention the detection performance to echo signal of method is proposed, also compared the operand of classic method and institute of the present invention extracting method at last.

Table 1 simulate signal parameter

Signal	Time delay (μ s)	Amplitude fading (dB)	The angle of arrival (°)	Doppler frequency (Hz)
					Main platform direct wave s1	0	0	-50	0
Main platform multipath s2	75	-10	-20	0
					Main platform multipath s3	40	-20	30	0
Lin Tai disturbs s4	0	-10～-30	8	0
					Target echo s5	731.92	-60～-85	5	64.724

The receiving array array number is 12.Additional noise is-50dB to be higher than target echo signal 10dB～35dB.The time-frequency two-dimensional coherent accumulation time is 1s.The DBF(digital beam forms) adopt Chebyshev's weighting, beam area is from-45 ° to 45 °, beam separation is 10 °.Constant false alarm detector adopts the unit to select big constant false alarm detector, and it is 4.5 that CFAR thresholding coefficient is set.Classic method and the present invention are proposed the method performance to be compared as follows:

Table 2 traditional technique in measuring performance table

Table 3 institute of the present invention extracting method detects the performance table

If target time delay, the relevant peak-peak of Doppler frequency place time-frequency two-dimensional are A, except target peak, the average out to B that time-frequency two-dimensional correlogram upper base is made an uproar, the peak-peak discrimination is defined as 10log (A/B) in then upward showing.

Target decays to-60dB, interference attenuation is-condition of 20dB under, classic method and institute of the present invention extracting method comparison diagram such as Fig. 5 are to shown in Figure 8, can tie up from time-frequency two-dimensional correlogram time delay peacekeeping Doppler respectively and observe the contrast target, can find that by contrast the end of classic method time-frequency two-dimensional correlogram makes an uproar higher, target is submerged in wherein, and to make an uproar in the end that the invention provides method time-frequency two-dimensional correlogram less, and target peak-peak discrimination is higher.

The emulated data that provides by table 2 and table 3 can illustrate that method proposed by the invention is having strong co-channel interference, and echo signal and interference are in same wave beam, exist under the strongly disturbing situation and can both effectively detect echo signal, and extract time delay, the Doppler frequency parameter of target, the validity that the present invention suggests plans has been described.Because it is relevant that classic method and institute of the present invention extracting method all will be used time-frequency two-dimensional, so relatively calculated amount only need compare the operand of time-frequency two-dimensional before relevant, establishing the receiving array element number of array is M, and umber of beats is N soon, and the wave beam number is L, and then comparative result is as follows:

Table 4 classic method computing scale

Table 5 institute of the present invention extracting method computing scale

By above calculating contrast as can be seen, institute of the present invention extracting method has a certain amount of reducing than the operand of classic method.And this method does not need to use reference antenna collimation arrived wave signal, has saved the cost of hardware to a certain extent.

Claims (4)

1. broadcast singal external radiation source position finding and detection method is characterized in that, may further comprise the steps:

Step 1: the take over party carries out bandpass sampling to the pending main channel frequency modulation broadcasting FM signal that receives and obtains sample sequence x (t), and t represents sampling instant;

Step 2: the autocorrelation matrix R that asks sample sequence x (t) _x

Step 3: to autocorrelation matrix R _xCarry out svd SVD and obtain R _x=U Λ U ^H, utilize to decompose the diagonal matrix Λ that obtains and the sample sequence x of unitary matrix U (t) carry out linear transformation obtain receiving signal from strong to weak arrangement y (t), Y (t)=[y wherein ₁(t) y ₂(t) ... y _M(t)] ^T, M is receiving antenna array element number, T representing matrix transposition;

Step 4: the sample sequence y (t) after the linear transformation is asked delay autocorrelation matrix R _y, to the feasible autocorrelation matrix R that postpones of the selection that postpones _yIn each eigenwert do not coincide;

Step 5: to postponing autocorrelation matrix R _yDo the SVD decomposition and obtain R _y=W Λ W ^H, utilize the signal z (t) that decomposes after the sample sequence y of unitary matrix W (t) that obtains advances to transform to disturb the inhibition processing, z (t)=W ^HY (t)=W ^HΛ ^-1/2U ^HX (t), z (t)=[z ₁(t) z ₂(t) ... z _M(t)] ^T

Step 6: will disturb among the signal z (t) after suppress handling the 3 the road to M road signal respectively with the 1 road signal z ₁(t) do the time-frequency distributions two-dimensional correlation and obtain corresponding correlation | Ψ _i(τ, f) |,

I=3 ..., M, L are bandpass sampling length, τ is time delay, f Doppler shift;

Step 7: respectively in the two-dimensional correlation value of 3 to M each road signal correspondence | Ψ _i(τ, f) | in search plain peak point, with the time delay of each road signal peak value point correspondence and Doppler shift as a useful signal, calculate each road signal to noise ratio (S/N ratio), as a certain road signal to noise ratio (S/N ratio) during more than or equal to threshold value, time delay and the Doppler shift that time delay and the Doppler of its peak point correspondence is defined as a target frequently then, otherwise judge in this road signal and do not have target.

2. broadcast singal external radiation source position finding and detection method according to claim 1 is characterized in that autocorrelation matrix R _xComputing method be: R _x=E{x (t) x ^H(t) }, E{} represents to average, and H represents conjugate transpose;

Postpone autocorrelation matrix R _yComputing method be: R _y=E{y (t) y ^H(t-τ) }.

3. broadcast singal external radiation source position finding and detection method according to claim 1 is characterized in that autocorrelation matrix R _xComputing method be:

H represents conjugate transpose;

Postpone autocorrelation matrix R _yComputing method be

4. as broadcast singal external radiation source position finding and detection method as described in the claim 1,2 or 3, it is characterized in that the method for calculating each road signal to noise ratio (S/N ratio) in the step 7 is:

| Ψ _i(τ _d, f _d) | be the two-dimensional correlation value on the i road | Ψ _i(τ, f) | peak point,

Represent to remove on the signal of i road | Ψ _i(τ _d, f _d) | outer, all | Ψ _i(τ, f) | average.

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