CN103293518B - Positioning and detection method of radiation source outside broadcast signals - Google Patents
Positioning and detection method of radiation source outside broadcast signals Download PDFInfo
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- CN103293518B CN103293518B CN201310206806.1A CN201310206806A CN103293518B CN 103293518 B CN103293518 B CN 103293518B CN 201310206806 A CN201310206806 A CN 201310206806A CN 103293518 B CN103293518 B CN 103293518B
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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
Technical field
The present invention relates to fm broadcast signal treatment technology, be specifically related to suppress strong co-channel interference and extract the technology of echo signal.
Background technology
Bistatic radar technology refers to and utilizes transmitter and receiver not in the advantage in same place, so as to improve receiving station disguise, obtain larger target forward direction area, reduce shadow region to the technology of electromagnetic wave attenuation.Passive Radar System based on external sort algorithm can utilize common civil signal as irradiation source, the active signal etc. of such as, digital television signal in daily life, frequency modulation broadcasting FM signal, mobile communication GSM signal, enemy, its systematic schematic diagram as shown in Figure 1, radar to the echo including direct wave, the echo of moving target, direct wave that other common-frequency broadcasting launching tower sends and other reflections off objects coming from broadcast emission tower itself of Received signal strength, the still life echo of such as various building reflection.Therefore, the target echo signal in radar return signal is extremely faint, and is submerged in various interference.
The detection method of the external radiant source target signal of tradition receives direct-path signal with reference channel, and main antenna receives multiple signals, comprising direct-path signal, target echo signal and Noise and Interference.First adopt normalization minimum mean-square NLMS algorithm to carry out adaptive cancellation to direct wave with main channel signal and reference channel signal, then by airspace filter, co-channel interference is suppressed, finally adopt time-frequency two-dimensional associated extraction target latency, Doppler frequency.
But bistatic radar in actual applications, how the most direct problem is exactly more effectively to the method that co-channel interference suppresses based on the external radiation source radar system of frequency modulation broadcasting FM signal, particularly when the co-channel interference signal received is within antenna main beam, or when being entered by antenna side lobe, further increase the difficulty of target detection.Due to interference and target echo signal, overlapping in a frequency domain, and in spatial domain, the method for digital beam froming also cannot be adopted to suppress it, therefore the disposal route of traditional external illuminators-based radar signal cannot meet the requirement detecting target echo.
Summary of the invention
Technical matters to be solved by this invention is, when the external illuminators-based radar be provided in based on frequency modulation broadcasting FM signal exists co-channel interference, effectively can peel off the broadcast singal non-cooperative location detection method of target and interference.
The present invention is that broadcast singal non-cooperative location detection method, comprises the following steps for solving the problems of the technologies described above adopted technical scheme:
Step 1: take over party carries out bandpass sampling to the pending main channel frequency modulation broadcasting FM signal received and obtains sample sequence x (t), and t represents sampling instant;
Step 2: the autocorrelation matrix R asking sample sequence x (t)
x;
Step 3: to autocorrelation matrix R
xcarry out svd SVD and obtain R
x=U Λ U
h, the diagonal matrix Λ utilizing decomposition to obtain and unitary matrix U carries out linear transformation to sample sequence x (t) and obtains arrangement y (t) of Received signal strength from strong to weak,
wherein y (t)=[y
1(t) y
2(t) ... y
m(t)]
t, M is receiving antenna array element number, T representing matrix transposition;
Step 4: sample sequence y (t) after linear transformation is asked and postpones autocorrelation matrix R
y, make to postpone autocorrelation matrix R to the selection postponed
yin each eigenwert do not coincide;
Step 5: to delay autocorrelation matrix R
ydo SVD decomposition and obtain R
y=W Λ W
h, the unitary matrix W utilizing decomposition to obtain processes signal z (t) after obtaining AF panel process, z (t)=W to sample sequence y (t)
hy (t)=W
hΛ
-1/2u
hx (t), z (t)=[z
1(t) z
2(t) ... z
m(t)]
t;
Step 6: by the 3rd road to M road signal in signal z (t) after AF panel process respectively with the 1st road signal z
1t () is done time-frequency distributions two-dimensional correlation and is obtained corresponding correlation | Ψ
i(τ, f) |,
i=3 ..., M, L are bandpass sampling length, and τ is time delay, f is Doppler shift;
Step 7: respectively in the two-dimensional correlation value that 3 to M each road signal is corresponding | Ψ
i(τ, f) | in search plain peak point, using time delay corresponding for each road signal peak value point and Doppler shift as a useful signal, calculate each road signal to noise ratio (S/N ratio), when having a certain time delay and Doppler shift place signal to noise ratio (S/N ratio) is more than or equal to threshold value, then time delay corresponding for its peak point and Doppler shift are defined as time delay and the Doppler shift of a target, otherwise judge to there is not target in this road signal.
The present invention utilizes the characteristic of target echo signal and co-channel interference statistical iteration, separates co-channel interference, thus reaches the object suppressed co-channel interference.Simultaneously, because the correlativity of target echo signal and direct-path signal is less, what can be similar to thinks that it also has the character of statistical iteration, comparatively traditional treatment method, the present invention does not need to carry out adaptive cancellation to reception main channel signal, also direct-path signal can be peeled off, thus serve the effect of saving operand.
The invention has the beneficial effects as follows, the effect of suppression can be played to co-channel interference in same wave beam, and then reach better detection perform.
Accompanying drawing explanation
Fig. 1 is the system principle schematic diagram based on broadcast non-cooperative location.
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, interference attenuation-20dB) of classic method echo signal.
Fig. 6 is time-frequency two-dimensional correlogram time delay dimension (target decay-60dB, interference attenuation-20dB) of the inventive method echo signal.
Fig. 7 is time-frequency two-dimensional correlogram frequency dimension (target decay-60dB, interference attenuation-20dB) of classic method echo signal.
Fig. 8 is time-frequency two-dimensional correlogram frequency dimension (target decay-60dB, interference attenuation-20dB) of the inventive method echo signal.
Embodiment
Processing signals model of the present invention is as follows:
FM modulation signal x (t) that pair array antenna receives carries out modeling, and the present invention processes mainly for baseband signal.If s (t) represents the baseband signal (direct-path signal) after FM modulation that some broadcasting television towers are launched, the angle of arrival is θ
d, through moving-target reflection, the target echo signal received by bistatic radar main channel antenna is a (θ
1) α
1s (t-τ
1) e
-j2 π f1t..., a (θ
m) α
2s (t-τ
m) e
-j2 π fMtnumber, wherein α
1..., α
mrepresent the decay of target echo, τ
1... τ
mrepresent the time delay of target, f
1..., f
mrepresent the Doppler frequency of target, θ
1..., θ
mrepresent the angle of arrival of target echo signal, a (θ
i)=[1 2 π sin (θ
i) d/ λ ... 2 π sin (θ
i) (N-1) d/ λ]
t, represent array antenna received drive vector, wherein d represents antenna distance, and λ represents signal wavelength, and N represents bay number, then by array antenna received to signal be: x (t)=a (θ
d) s (t)+a (θ
1) α
1s (t-τ
1) e
-j2 π f1t..., a (θ
m) α
2s (t-τ
m) e
-j2 π fMt+ a (θ
j) J (t)+n (t) a (θ
d) s (t) represents direct wave, a (θ
1) α
1s (t-τ
1) e
-j2 π f1t..., a (θ
m) α
2s (t-τ
m) e
-j2 π fMtfor target echo, J (t) represents the signal launched by another broadcasting television tower, i.e. co-channel interference signal, θ
jfor its angle of arrival (close with certain target angle of arrival), n (t) represents the thermonoise of receiver, then the work that the present invention will do is that middle co-channel interference signal suppresses to the received signal, and extracts target component.
Technical solution of the present invention implementation step as shown in Figure 2, comprising:
Step 1: receiver carries out bandpass sampling to the pending main channel array FM modulation signal received, 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) and have direct wave, co-channel interference, noise and target echo signal, T representing matrix transposition.
Step 2: the autocorrelation matrix R asking sample sequence x (t)
x=E{x (t) x
h(t) }, if the sampling time is comparatively, then can suppose that sample sequence is stable stochastic process in sampling length L, ask statistical average that seeking time can be adopted on average to replace like this, namely
H represents conjugate transpose.
Step 3: to autocorrelation matrix R
xcarry out SVD decomposition and obtain R
x=U Λ U
h, the diagonal matrix Λ utilizing decomposition to obtain and unitary matrix U carries out linear transformation to x (t) and obtains y (t)=Λ
-1/2u
hx (t), wherein y (t)=[y
1(t) y
2(t) ... y
m(t)]
t.
Step 4: time delay autocorrelation matrix R is asked to y (t)
y=E{y (t) y
h(t-τ) }, in like manner pot life postpones autocorrelation estimation statistical delay auto-correlation, namely
the selection postponing τ is required it is make R
yin each eigenwert do not coincide.
Step 5: to delay autocorrelation matrix R
ydo SVD decomposition and obtain R
y=W Λ W
h, then signal z (the t)=W after AF panel process is eventually passed through
hΛ
-1/2u
hx (t), z (t)=[z
1(t) z
2(t) ... z
m(t)]
t.Wherein, first via signal is the maximum signal of energy in vectorial z (t), and the second road signal is the signal that energy is time large, is respectively direct-path signal and undesired signal in this application scene, and the later signal in the 3rd tunnel is target echo signal.Because interference and most of energy of direct wave are all stripped in the middle of z (t) the one the second tunnel, the signal after from the 3rd tunnel equivalence can be regarded as and suppress interference, will provide explanation in emulation.
Step 6: adopt time-frequency two-dimensional coherent matched filter to extract time delay and the Doppler frequency parameter of target.3rd tunnel of M road signal step 5 obtained is to M road signal and the 1st road signal z
1t () is done time-frequency two-dimensional and is correlated with,
i=3 ..., M, (τ, f) is time delay and Doppler frequency.When there is target, | Ψ
i(τ, f) | a peak point can be produced | Ψ
i(τ
d, f
d) |, after searching peak point, calculate
expression removes | Ψ
i(τ
d, f
d) | outer, all | Ψ
i(τ, f) | average, if its value is greater than the threshold value pre-set, then represent that target exists, corresponding (τ
d, f
d) be time delay and the Doppler frequency of target; If its value is less than threshold value, then represent to there is not target.
Embodiment 1
In the present embodiment, adopt the stochastic audio signal of two sections of statistical iteration respectively as modulation signal in order to produce FM broadcast singal, in this, as the direct-path signal in this simulating scenes and co-channel interference, 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 containing undesired signal and target echo signal in mixed signal.Emulation platform operating system is WIN7, adopts MATLAB to compile.The technical scheme adopting the present invention to propose detects target echo signal.
Arrange jamming power be 0dB as a reference.Signal to noise ratio (S/N ratio) (ratio of target echo signal and noise) is set as-30dB, signal interference ratio is set as-70dB, the target angle of arrival is 0 °, target echo interference differential seat angle is 0 ~ 10 ° of change, the gain of emulation signal interference ratio with the change of target jamming differential seat angle, and adopts Wave beam forming process co-channel interference to contrast with classic method, wherein, choose weighting scheme for Chebyshev's weighting, decay to 30dB.The present invention adopts 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 jamming target differential seat angle is greater than 1 °, signal interference ratio gain can reach a larger value, and along with the increase of jamming target angle, 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, FM signal production method is with embodiment 1.The technical scheme adopting the present invention to propose detects target echo signal.
Below provide each simulation parameter of mixed signal, and the detection perform to echo signal of classic method and put forward the methods of the present invention more at different conditions, finally also compares the operand of classic method and institute of the present invention extracting method.
Table 1 simulate signal parameter
| Signal | Time delay (μ s) | Amplitude fading (dB) | The angle of arrival (°) | Doppler frequency (Hz) |
| Main direct wave s1 | 0 | 0 | -50 | 0 |
| Main multipath s2 | 75 | -10 | -20 | 0 |
| Main 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 |
Receiving array array number is 12.Additional noise is-50dB, higher than target echo signal 10dB ~ 35dB.The time-frequency two-dimensional coherent accumulation time is 1s.DBF (digital beam froming) adopts Chebyshev's weighting, and beam area is from-45 ° to 45 °, and beam separation is 10 °.Constant false alarm detector adopts unit to select large constant false alarm detector, and arranging CFAR threshold coefficient is 4.5.To classic method and put forward the methods Performance comparision of the present invention as follows:
Table 2 traditional technique in measuring performance table
Table 3 institute of the present invention extracting method detection perform table
If target latency, Doppler frequency place time-frequency two-dimensional are correlated with, peak-peak is A, and except target peak, the average out to B that time-frequency two-dimensional correlogram upper base is made an uproar, then in upper table, peak-peak discrimination is defined as 10log (A/B).
Target decays to-60dB, interference attenuation is under the condition of-20dB, classic method and institute of the present invention extracting method comparison diagram are as shown in Fig. 5 to Fig. 8, can tie up from time-frequency two-dimensional correlogram time delay peacekeeping Doppler respectively and observe contrast target, can be found by contrast, the end of classic method time-frequency two-dimensional correlogram, makes an uproar higher, and target is submerged in wherein, and the end that the invention provides method time-frequency two-dimensional correlogram makes an uproar less, and target maximum peak region calibration is higher.
The emulated data provided 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 within same wave beam, effectively echo signal can be detected under there is strongly disturbing situation, and extract time delay, the Doppler frequency parameter of target, describe the validity that the present invention suggests plans.
Due to classic method and institute of the present invention extracting method, all will to use time-frequency two-dimensional relevant, thus compare calculated amount only need compare time-frequency two-dimensional be correlated with before operand, if receiving array element number of array is M, fast umber of beats is N, and wave beam number is L, then comparative result is as follows:
Table 4 classic method computing scale
Table 5 institute of the present invention extracting method computing scale
Can find out by calculating contrast above, institute of the present invention extracting method has a certain amount of reduction than the operand of classic method.And this method does not need to use reference antenna collimation arrived wave signal, saves the cost of hardware to a certain extent.
Claims (4)
1. broadcast singal non-cooperative location detection method, is characterized in that, comprises the following steps:
Step 1: take over party carries out bandpass sampling to the pending main channel fm broadcast signal received and obtains sample sequence x (t), and t represents sampling instant;
Step 2: the autocorrelation matrix R asking sample sequence x (t)
x;
Step 3: to autocorrelation matrix R
xcarry out svd and obtain R
x=U Λ U
h, the diagonal matrix Λ utilizing decomposition to obtain and unitary matrix U carries out linear transformation to sample sequence x (t) and obtains arrangement y (t) of Received signal strength from strong to weak,
wherein y (t)=[y
1(t) y
2(t) ... y
m(t)]
t, M is receiving antenna array element number, T representing matrix transposition;
Step 4: sample sequence y (t) after linear transformation is asked and postpones autocorrelation matrix R
y, make to postpone autocorrelation matrix R to the selection postponed
yin each eigenwert do not coincide;
Step 5: to delay autocorrelation matrix R
yr is obtained as svd
y=W Λ W
h, the unitary matrix W utilizing decomposition to obtain transforms to signal z (t) after AF panel process to sample sequence y (t), 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: by the 3rd road to M road signal in signal z (t) after AF panel process respectively with the 1st road signal z
1t () is done time-frequency distributions two-dimensional correlation and is obtained corresponding correlation | Ψ
i(τ, f) |,
i=3 ..., M, L are bandpass sampling length, and τ is time delay, f is Doppler shift;
Step 7: respectively in the two-dimensional correlation value that 3 to M each road signal is corresponding | Ψ
i(τ, f) | middle search peak point, using time delay corresponding for each road signal peak value point and Doppler shift as a useful signal, calculate each road signal to noise ratio (S/N ratio), when there being a certain road signal to noise ratio (S/N ratio) to be more than or equal to threshold value, then time delay corresponding for its peak point and Doppler shift are defined as time delay and the Doppler shift of a target, otherwise judge to there is not target in this road signal.
2. broadcast singal non-cooperative location detection method as claimed in claim 1, is characterized in that, autocorrelation matrix R
xcomputing method be: R
x=E{x (t) x
h(t) }, E{} represents and averages, and H represents conjugate transpose;
Postpone autocorrelation matrix R
ycomputing method be: R
y=E{y (t) y
h(t-τ) }.
3. broadcast singal non-cooperative location detection method as claimed in claim 1, is characterized in that, autocorrelation matrix R
xcomputing method be:
h represents conjugate transpose;
Postpone autocorrelation matrix R
ycomputing method be:
4. broadcast singal non-cooperative location detection method as described in any one of claim 1-3, is characterized in that, the method calculating each road signal to noise ratio (S/N ratio) in step 7 is:
| Ψ
i(τ
d, f
d) | be the two-dimensional correlation value on the i-th tunnel | Ψ
i(τ, f) | peak point,
represent and the i-th road signal remove | Ψ
i(τ
d, f
d) | outer, all | Ψ
i(τ, f) | average.
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| CN104656065A (en) * | 2015-01-29 | 2015-05-27 | 河海大学 | Method for restraining sparse adaptive direct wave and noise wave of passive bistatic radar |
| CN105487072A (en) * | 2015-12-29 | 2016-04-13 | 武汉工程大学 | Method and system of joint location based on T2/R time difference and Doppler shift |
| CN106199546B (en) * | 2016-06-30 | 2019-01-11 | 西安电子科技大学 | Direct-path signal method of purification based on external illuminators-based radar |
| CN106199547B (en) * | 2016-06-30 | 2019-01-11 | 西安电子科技大学 | Weak target detection method at a slow speed based on external illuminators-based radar |
| CN106597409B (en) * | 2016-12-19 | 2019-02-12 | 电子科技大学 | A kind of delay-Doppler frequency displacement extracting method based on external illuminators-based radar |
| CN108287341A (en) * | 2017-12-15 | 2018-07-17 | 空间防务技术（深圳）有限公司 | A kind of Low Altitude Target Detection method and its system, electronic equipment |
| CN108680910B (en) * | 2018-05-15 | 2021-09-28 | 河海大学 | Frequency modulation broadcast external radiation source radar target detection method based on waveform cognition |
| CN114624649B (en) * | 2022-03-11 | 2024-03-19 | 北京理工大学 | Method for positioning airborne passive synthetic aperture radiation source insensitive to residual frequency offset |
| CN116819430B (en) * | 2023-06-30 | 2024-03-15 | 中国人民解放军军事科学院***工程研究院 | Direction finding method for same-frequency signal under strong radiation source background |
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| US5414729A (en) * | 1992-01-24 | 1995-05-09 | Novatel Communications Ltd. | Pseudorandom noise ranging receiver which compensates for multipath distortion by making use of multiple correlator time delay spacing |
| US6661371B2 (en) * | 2002-04-30 | 2003-12-09 | Motorola, Inc. | Oscillator frequency correction in GPS signal acquisition |
| CN101718860B (en) * | 2009-11-27 | 2012-01-11 | 电子科技大学 | Non-cooperative target radio positioning method with unknown signal wave type |
| CN101799542B (en) * | 2010-01-08 | 2012-06-20 | 西安电子科技大学 | Passive coherent location radar direction finding system based on Adcock antenna and direction finding method thereof |
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