Moving target ambiguity resolution method based on frequency shift correlation

Abstract

The invention belongs to the technical field of radio signal monitoring, and provides a moving target ambiguity resolution method based on frequency shift correlation. The method specifically comprises the following steps: defining a detection parameter'frequency shift 'as a difference value between a fuzzy carrier frequency and a real spectrum center; at two calculation moments, determining a corresponding fuzzy speed in a fuzzy space by using a radiation source fuzzy positioning solution, calculating a fuzzy carrier frequency corresponding to the fuzzy speed, and obtaining a frequency shift [delta] fmoij as a detection parameter based on the fuzzy carrier frequency; calculating a Doppler frequency shift fdij corresponding to each radiation source position and the corresponding carrier frequency at two calculation moments; and respectively calculating each calculation moment, calculating frequency shift correlation values of the frequency shift delta fmoij and the Puller frequency shift fdij, adding the frequency shift correlation values of the two moments to find out a minimum frequency shift correlation value, and taking a time difference positioning solution corresponding to the minimum frequency shift correlation value as a real solution.

Description

Technical Field

[0001] The invention belongs to the technical field of radio signal monitoring and proposes a moving target deambiguation method based on frequency shift correlation. Background Art

[0002] The passive positioning system itself does not emit any signal. It determines the location of the target by intercepting the signal emitted by the radiation source through the monitoring station. It has important application value, especially in large-scale high-precision monitoring and search situations. Among them, the three-station time difference positioning system is a typical technical solution.

[0003] The three-station time difference positioning system has the advantages of large monitoring range and high positioning accuracy. However, with the development of electronic countermeasure technology, the demand for positioning moving targets with high pulse repetition frequency is becoming more and more urgent. In this application context, time difference ambiguity becomes one of the key technical challenges.

[0004] Time difference positioning ambiguity includes two cases:

[0005] 1. The ambiguity of the time difference positioning system itself. From the calculation formula of the time difference positioning equation, it can be seen that the positioning equation has two solutions. The time difference positioning solution process itself will bring about ambiguity problems. The size of the ambiguity area is mainly determined by the deployment of the time difference positioning system monitoring station. For the positioning ambiguity area, it can be eliminated by using known prior information and the actual situation of the station deployment. This ambiguity is not discussed in this patent.

[0006] 2. Long baselines blur the time difference positioning of high repetition frequency radiation sources. If the three time difference measurement stations in the time difference positioning system are represented by A, B, and C respectively, and the distance between the two time difference measurement stations A and B is recorded as d, assuming that there is only one radiation source in the scene, the distance from this radiation source to station A and station B is recorded as d respectively. A , d B , the propagation time to the measuring station is denoted as T A , T B , then d A、 d B If the absolute value of the difference is not greater than d, then the time difference Δt (Δt = T A -T B)'s absolute value |Δt|≤T=d / c (c is the speed of light), T is called the time measurement window of stations A and B. When the radiation source pulse repetition period is greater than T, only one pulse appears in the time measurement window, and the arrival time difference of the pulse is unique at this time. When the radiation source repetition period is less than T, more than two pulses will appear in the time measurement window, forming multiple arrival time differences, that is, time difference ambiguity. Similarly, there is time difference ambiguity between the time difference measurement stations A and C. When pairing the time difference, the time difference between stations A and B and the time difference between stations A and C are combined and paired. Originally, one radiation source corresponding to a unique time difference pair becomes corresponding to multiple time difference pairs. After the positioning is solved, multiple positioning solutions appear, that is, positioning ambiguity occurs. Summary of the invention

[0007] In view of this, the present application proposes a moving target deambiguation method based on frequency shift correlation to address the time difference positioning ambiguity problem of long baseline for high repetition rate radiation sources. This method can accurately remove the ambiguous solution and select the true position of the target.

[0008] The technical solution for implementing the present invention is as follows:

[0009] A moving target deambiguation method based on frequency shift correlation, the specific process is:

[0010] The detection parameter "frequency shift" is defined as the difference between the "fuzzy carrier frequency" and the center of the real spectrum;

[0011] At two calculation moments, the corresponding fuzzy speed is determined in the fuzzy space using the fuzzy positioning solution of the radiation source, the fuzzy carrier frequency corresponding to the fuzzy speed is calculated, and the "frequency shift" Δf as the detection parameter is obtained based on the fuzzy carrier frequency moij ;

[0012] At two calculation moments, for each radiation source position E ij And the corresponding carrier frequency f cij Calculate the corresponding Doppler frequency shift f dij ;

[0013] Calculate each calculation moment separately and calculate the frequency shift Δf moij and the Doppler frequency shift f dij The frequency shift correlation value of the two moments is added together to find the minimum frequency shift correlation value, and the time difference positioning solution corresponding to the minimum frequency shift correlation value is the true solution.

[0014] Furthermore, the fuzzy positioning of the radiation source described in the present invention is obtained by using the pulse arrival time to complete pulse pairing and time difference pairing, and based on the ephemeris data, the radiation source is positioned to obtain n fuzzy positions of the radiation source.

[0015] Furthermore, the present invention performs frequency band screening on the time domain intercepted signal, performs frequency domain processing to obtain the spectrum center, and uses one of the spectrum centers as a reference to calculate the fuzzy frequency difference Δf i , based on the fuzzy frequency difference Δf i The fuzzy carrier frequency corresponding to the fuzzy speed is calculated.

[0016] Furthermore, the present invention also calculates the frequency shift correlation values ​​corresponding to n moments, superimposes all the calculated frequency shift correlation values, and finds the minimum frequency shift correlation value after superposition, and the time difference positioning solution corresponding to the minimum frequency shift correlation value is the true solution.

[0017] Beneficial Effects

[0018] Compared with other positioning technologies, the method of the present invention can solve the ambiguity problem of moving targets. Computer simulation experiments show that the present invention can accurately remove the ambiguity solution and select the real position of the target within the frequency difference error range of 0.01 Hz. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a flow chart of defuzzification based on frequency shift correlation.

[0021] Figure 2 Distribution plot of frequency shift correlation values. Specific implementation plan

[0022] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0023] It should be noted that the following embodiments and features in the embodiments may be combined with each other in the absence of conflict; and, based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without making any creative work are within the scope of protection of the present disclosure.

[0024] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein may be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present disclosure, it should be understood by those skilled in the art that an aspect described herein may be implemented independently of any other aspect, and two or more of these aspects may be combined in various ways. For example, any number of aspects described herein may be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein may be used to implement this device and / or practice this method.

[0025] The applicant has analyzed the formation process of time difference positioning ambiguity for long baseline and high repetition frequency radiation source, and it can be known that improving the time difference measurement accuracy will obtain a high-precision ambiguity solution, but the ambiguity solution cannot be eliminated; in order to solve the time difference ambiguity problem in the three-station time difference positioning, the applicant found that there is a correlation between the "frequency shift" parameter in the fuzzy space (the difference between the "fuzzy carrier frequency" and the real spectrum center) and the Doppler frequency shift in the real space, that is, when the frequency shift parameter in the fuzzy space is strongly correlated with the Doppler frequency shift in the real space, it means that the frequency shift in the fuzzy space is the real solution at this time. Therefore, the present invention uses the frequency shift correlation between the fuzzy space and the real space to achieve deambiguation. Using this correlation characteristic, the applicant has designed the following technical solution:

[0026] A moving target deambiguation method based on frequency shift correlation, the specific process is:

[0027] The detection parameter "frequency shift" is defined as the difference between the "fuzzy carrier frequency" and the center of the real spectrum;

[0028] At two calculation moments, the corresponding fuzzy speed is determined in the fuzzy space using the fuzzy positioning solution of the radiation source, the fuzzy carrier frequency corresponding to the fuzzy speed is calculated, and the "frequency shift" Δf as the detection parameter is obtained based on the fuzzy carrier frequency moij ;

[0029] At two calculation moments, for each radiation source position E ij And the corresponding carrier frequency f cij Calculate the corresponding Doppler frequency shift f dij ;

[0030] Calculate each calculation moment separately and calculate the frequency shift Δf moij and the Doppler frequency shift f dij The frequency shift correlation value of the two moments is added together to find the minimum frequency shift correlation value, and the time difference positioning solution corresponding to the minimum frequency shift correlation value is the true solution.

[0031] The present embodiment calculates the frequency shift Δf moijand the Doppler frequency shift f dij The frequency shift correlation value of the two moments is added to find the minimum frequency shift correlation value. For the true solution, the frequency shift has the best correlation with the Doppler frequency shift solution, while the correlation of the fuzzy solution is poor. This feature is used to eliminate the fuzzy solution.

[0032] The implementation method of the method of the present invention is described in detail below with reference to the accompanying drawings (the monitoring platform is a satellite platform).

[0033] The present application embodiment provides a moving target deambiguation method based on frequency shift correlation, and the implementation process is as follows:

[0034] For a radiation source, the signal intercepted by the monitoring station is used to select a certain time to perform time difference positioning processing. Due to the existence of time difference ambiguity, there are multiple corresponding positions in the positioning results. Assuming there are n, use E ij Indicates, where i = 1, 2, respectively represents the first moment and the second moment; j = 1, 2, ... n, represents the position number corresponding to a certain time difference. Only one of these "positions" is a true value, and the rest are false solutions. Perform frequency domain processing on the intercepted signal to obtain its spectrum center, denoted as f cen1 (only 1 value); at another moment, similarly, the corresponding n positioning solutions are obtained, and the center of the spectrum is denoted as f cen2 Using the center frequency of the spectrum, we can get the frequency difference information Δf=f cen1 -f cen2 ; Use the positions (each has n) and time interval information of two moments to pair the positions and obtain the velocities (n), of which n-1 are pseudo-velocities; Substitute the velocity, position, and frequency difference information into the frequency difference equation to obtain the carrier frequency information corresponding to each position (each position has n), denoted as f ci1 , f ci2 , f ci3 , ....f cin , where i = 1, indicating the first moment, and i = 2, indicating the second moment; then for a certain moment, the frequency shift Δf can be obtained moij =f cij -f ceni , where i = 1, 2, represents the corresponding time, j = 1, 2, ... n, represents the corresponding position. At the same time, for each radiation source position E at time i ij , and the corresponding f cij The corresponding Doppler frequency shift f can be calculated dij, the fuzzy position, the corresponding fuzzy speed, fuzzy carrier frequency, Doppler frequency shift and other parameters form the fuzzy space, and the corresponding real position, the corresponding real speed, real carrier frequency, real Doppler frequency shift and other parameters form the signal space. Our research shows that the correlation between the frequency domain and the Doppler frequency shift in the fuzzy space is lower than the correlation between the Doppler frequency shift in the signal space. Based on this, the fuzzy solution is eliminated, and the simulation results show that this method is effective. The specific steps are:

[0035] Read the pulse arrival time at time 1, complete pulse pairing and time difference pairing, read the satellite position and other data from the ephemeris data, complete the radiation source positioning corresponding to time 1, and obtain the n radiation source fuzzy positions E 1j .

[0036] Read the pulse arrival time at time 2, complete pulse pairing and time difference pairing, read the satellite position and other data from the ephemeris data, complete the radiation source positioning corresponding to time 2, and obtain the n radiation source fuzzy positions E 2j ;

[0037] Perform frequency domain analysis on the intercepted data and obtain the spectrum center f cen1 、f cen2 、f cen3 ; Further calculation to obtain the frequency difference information Δf1 = f cen2 -f cen1 , Δf2=f cen3 -f cen1 .

[0038] Complete the pairing of the radiation source positions at two moments and find the fuzzy velocity corresponding to the radiation source position;

[0039] According to the corresponding speed, radiation source position, satellite position and speed, and frequency difference, substituting into the frequency difference equation, the fuzzy carrier frequency f corresponding to each radiation source position can be obtained. ci1 , f ci2 ; For the fuzzy position solution, the carrier frequency at this time corresponds to a non-existent fuzzy carrier frequency, while for the real position, the carrier frequency at this time corresponds to a real carrier frequency. In short, the obtained carrier frequency includes the carrier frequency in the fuzzy space and the carrier frequency in the real space.

[0040] Then, for a certain moment, the frequency shift Δf can be obtained moij =f cij -f ceni ,This frequency shift associates the fuzzy carrier frequency in the fuzzy space with the spectrum in the real world. For the fuzzy position solution, the frequency shift at this time corresponds to a "fuzzy" frequency shift that does not have any physical meaning, while for the real position, the physical meaning of the "frequency shift" at this time is a real Doppler frequency shift.

[0041] At time i, for each radiation source position Eij And the corresponding carrier frequency f cij The corresponding Doppler frequency shift f can be calculated dij . ; For the fuzzy position solution, f dij is a "fuzzy" value without any physical meaning. For the real position, the "f dij "The corresponding physical meaning is a real Doppler carrier frequency.

[0042] Calculate the frequency shift Δf moij and the Doppler frequency shift f dij The frequency shift correlation value of the two moments is added to find the minimum frequency shift correlation value. Studies have shown that for the true position solution, relative to the fuzzy solution position, the frequency shift Δf moij and the Doppler frequency shift f dij It has better correlation, so the time difference positioning solution corresponding to the minimum frequency shift correlation value is the true solution.

[0043] The embodiment of the present application discovered that the signal correlation of the fuzzy space is weaker than the frequency shift correlation of the signal space, and introduced the characteristics of the fuzzy space and the frequency difference information without using the direction finding information, thus avoiding the limitations of direction finding positioning (the direction finding accuracy is limited. When the distance between the radiation source and the monitoring platform is large enough, its positioning accuracy deteriorates, which is far worse than the time difference positioning accuracy). The judgment criteria of the fuzzy solution based on the frequency shift correlation are proposed, so that the fuzzy solution can be eliminated accurately. Therefore, this scheme solves the problem of deambiguation under the condition of high-frequency moving targets. When using the frequency difference information, the fuzzy space is constructed, and the frequency shift correlation is used as the judgment parameter. From the characteristics of the fuzzy space and the signal space, the difference between the fuzzy value and the true value is determined.

[0044] Example:

[0045] 1. Input parameters

[0046] (1) Satellite parameters

[0047] The satellite positions and velocities at two moments (10s interval) are shown in Tables 1 and 2.

[0048] Table 1 Satellite position and speed at the first moment

[0049]

[0050]

[0051] Table 2 Satellite position and speed at the second moment

[0052] X(km) Y(km) Z(km) Vx(km / s) Vy(km / s) Vz(km / s) Satellite 1 -29256.3 29272.77 -1232.43 -0.07994 -0.07924 0.01424 Satellite 2 -30977.6 29131.44 907.7701 0.003333 0.071282 0.071367 Satellite 3 -29106.4 31008.94 506.7692 0.072278 0.003589 -0.09326

[0053] (2) Radiation source parameters

[0054] The geodetic coordinates of the radiation source are (L1, B1, H1) = (110, 40, 8000),

[0055] (L2, B2, H2) = (110.02, 39.975, 8000) The position (Earth-fixed coordinates) and velocity of the radiation source at two moments (10s interval) are shown in Tables 3 and 4.

[0056] Table 3 The position of the radiation source at two times

[0057] x(m) y(m) z(m) First Moment -1675500.576 4603399.998 4083127.873 Second Moment -1677718.82 4604492.999 4080998.377

[0058] Table 4 Speed ​​of radiation source

[0059] vx(m / s) vy(m / s) vz(m / s) -221.824 109.3001 -212.95

[0060] (3) Error parameters

[0061] Altitude error = 1000m; Satellite error = 0; Spectrum center error = 0; Time difference error = 0; Frequency difference error = -0.01Hz~0.01Hz

[0062] (4) Carrier frequency

[0063] Carrier frequency = 3 GHz

[0064] (5)PRF

[0065] PRF=20KHz

[0066] (6) Time difference parameters

[0067] The time difference pairs are calculated using the radiation source and the satellite position, and several groups of fuzzy time difference pairs are set. For the convenience of simulation, this example uses 9 pairs of time difference pairs as an example. The time difference pairs at two moments are shown in Table 5 and Table 6.

[0068] Table 5 Time difference of the first moment

[0069] Real Time Difference-PRT Real time difference Real time difference + PRT tao12 0.003154893 0.003204893 0.003254893 tao13 0.002816798 0.002866798 0.002916798

[0070] Table 6 Second time difference

[0071] Real Time Difference-PRT Real time difference Real time difference + PRT tao12 0.003156277 0.003206277 0.003256277 tao13 0.002815673 0.002865673 0.002915673

[0072] (7) Spectrum center and frequency difference

[0073] The spectrum center f at two moments is calculated using the satellite position and velocity in Tables 1 and 2, the target position and velocity in Tables 3 and 4, and the set carrier frequency parameters. cen1 and f cen2 (measured value in engineering applications) and frequency difference Δf. As shown in Table 7 and Table 8.

[0074] Table 7 Spectral center at two moments

[0075] Spectrum center 1(Hz) Spectrum center 2(Hz) Spectrum center 3 (Hz) First Moment 3000002616.11 3000002200.61 3000002953.27 Second Moment 3000002615.70 3000002200.60 3000002953.36

[0076] Table 8 Frequency difference between two moments

[0077] Frequency difference 1(Hz) Frequency difference 2(Hz) First Moment -415.5003653 337.16 Second Moment -415.099133 337.66

[0078] 2. Time difference positioning solution

[0079] The time difference positioning is performed using the time difference pair. The time difference positioning result of the two moments is E 1j and E 2j As shown in Table 9 and Table 10.

[0080] Table 9 Time difference positioning solution at the first moment

[0081] x(m) y(m) z(m) 1 -1388201.612 4404347.658 4397703.538 2 -1772475.616 4428894.506 4232964.035 3 -2120649.838 4425641.861 4074331.909 4 -1291003.432 4580271.95 4245990.516 5 -1676712.177 4604482.424 4082957.976 6 -2026505.606 4601409.116 3925806.837 7 -1181451.468 4744581.533 4095800.125 8 -1569962.939 4769493.4 3934253.662 9 -1922363.016 4767318.469 3778425.294

[0082] Table 10 Time difference positioning solution at the second moment

[0083] x(m) y(m) z(m) 1 -1390586.898 4405816.671 4395492.828 2 -1774476.937 4429966.914 4231016.024 3 -2122368.464 4426400.508 4072624.038 4 -1293619.041 4581766.386 4243597.515 5 -1678929.521 4605574.669 4080828.693 6 -2028428.663 4602183.132 3923918.644 7 -1184307.044 4746106.993 4093224.615 8 -1572401.784 4770607.718 3931943.533 9 -1924493.595 4768108.182 3776357.583

[0084] 3. Speed ​​Solution

[0085] Using the above positioning positions and time intervals, the speed can be solved as shown in Table 11.

[0086] Table 11 Second time difference positioning solution

[0087] <![CDATA[v x ]]> <![CDATA[v y ]]> <![CDATA[v z ]]> 1 -238.5285765 146.9012568 -221.0710423 2 -200.1320583 107.2407282 -194.8010711 3 -171.8625519 75.86473738 -170.787139 4 -261.5608714 149.4436408 -239.3001302 5 -221.7343275 109.2244774 -212.9283203 6 -192.3057281 77.40162795 -188.8192513 7 -285.5576088 152.5460651 -257.5510131 8 -243.8845609 111.4317622 -231.0129294 9 -213.0579805 78.971237 -206.7710412

[0088] 4. Carrier frequency calculation

[0089] Using the satellite positions and data in Tables 1 and 2, and the target positions and velocities in Tables 9 and 10,

[0090] The frequency difference value in Table 8 can be used to calculate the carrier frequency value f at two times ci1 , f ci2 .

[0091] 5. Frequency shift Frequency shift Δf mo1j calculate

[0092] The frequency shift Δf can be calculated by combining the spectrum center in Table 7 with the carrier frequency value calculated above. mo1j =f c1j -f cen1 .

[0093] 6. Doppler shift calculation

[0094] Using the satellite positions and data in Tables 1 and 2, the time difference positioning solutions in Tables 9 and 10, and the carrier frequency values ​​calculated above, the time difference positioning solutions to the corresponding 9 groups of Doppler shifts f can be calculated. d1j .

[0095] VII. Correlation calculation of two frequency shifts and fuzzy solution elimination

[0096] Calculate the frequency shift Δf at two moments respectively mo1j and Doppler frequency shift f d1j The frequency shift correlation value (i.e., correlation) is calculated, and then the minimum value of the frequency shift correlation values ​​corresponding to the 9 time difference positioning solutions is found. The time difference positioning solution corresponding to the minimum frequency shift correlation value is the true solution.

[0097] Under different frequency difference errors, the distribution diagram of frequency shift correlation value is as follows: Figure 2 As shown in the figure, it can be seen that when the frequency difference error is within the range of [-0.01Hz, 0.01Hz], the minimum frequency shift correlation value is always in the 5th group, that is, when the frequency difference error is within this range, the true value position can always be correctly judged.

[0098] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A moving target deambiguation method based on frequency shift correlation, characterized in that: The specific process is: The detection parameter "frequency shift" is defined as the difference between the fuzzy carrier frequency and the center of the real spectrum; At two calculation moments, the corresponding fuzzy velocity is determined in the fuzzy space using the fuzzy positioning solution of the radiation source, the fuzzy carrier frequency corresponding to the fuzzy velocity is calculated, and the "frequency shift" Δf as the detection parameter is obtained based on the fuzzy carrier frequency moij ; At two calculation moments, the corresponding Doppler frequency shift f is calculated for each radiation source position and the corresponding carrier frequency. dij ; Calculate each calculation moment separately and calculate the frequency shift Δf moij and the Doppler frequency shift f dij The frequency shift correlation value of the two moments is added together to find the minimum frequency shift correlation value, and the time difference positioning solution corresponding to the minimum frequency shift correlation value is the true solution.

2. The moving target deambiguation method based on frequency shift correlation according to claim 1, characterized in that: The fuzzy positioning of the radiation source is obtained by using the pulse arrival time to complete pulse pairing and time difference pairing, and based on the ephemeris data, the radiation source is positioned to obtain n fuzzy positions of the radiation source.

3. The moving target deambiguation method based on frequency shift correlation according to claim 1, characterized in that: After filtering the frequency band of the intercepted signal in the time domain, the spectrum center is obtained after frequency domain processing. Taking one of the spectrum centers as a reference, the fuzzy frequency difference Δf is calculated respectively. i , based on the fuzzy frequency difference Δf i The fuzzy carrier frequency corresponding to the fuzzy speed is calculated.

4. The moving target deambiguation method based on frequency shift correlation according to claim 1, characterized in that: The frequency shift correlation values ​​corresponding to n moments are also calculated, all the calculated frequency shift correlation values ​​are superimposed, and the minimum frequency shift correlation value after superposition is found. The time difference positioning solution corresponding to the minimum frequency shift correlation value is the true solution.

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