RU2805566C1 - Range-difference metering method for determining location of radio emission source under conditions of multipath propagation of radio waves - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention relates to methods for determining the location of a radio emission source (RES), and is intended for use in navigation, direction finding, and location aids for determining the location of RES. The invention is proposed to increase the accuracy of determining the coordinates of RES in three-dimensional space under conditions of multipath propagation of radio waves (MPRP). The claimed method is based on the reception of RES radio signals by each of the receiving points (RP) with known coordinates and measuring the time of arrival of the radio signal. For all possible pairs of RPs, the differences in arrival times of the radio signal from the RES to the RPs of this pair are calculated and the corresponding range differences are calculated from them. A set of intermediate coordinate estimates (ICE) of the RES is formed by determining the ICE using the difference-rangefinder method for various combinations of four RPs. RPs in MPRP conditions are identified. The final estimate of the coordinates of the RES is obtained by calculating the arithmetic mean of the ICE, taking into account the identified RPs in MPRP conditions.

EFFECT: increased accuracy of determining the coordinates of RES in three-dimensional space under conditions of multipath propagation of radio waves (MPRP).

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Description

The invention relates to radio engineering, namely to methods for determining the location of a radio emission source (RES), and is intended for use in navigation, direction finding, and location aids for determining the location of RES.

There is a known method for determining the coordinates of a radio emission source from an aircraft using a triorthogonal loop antenna system according to patent RUS No. 2709607 [1], according to which the following sequence of actions is performed:

receive radio signals from radioactive sources using a triorthogonal loop antenna system (TORAS);

measure the coordinates of the centers and orientation angles of the TORAS at various points in time during the flight of the aircraft;

determine the positions in space of the magnetic field strength vectors at different times;

form auxiliary planes of the RES position;

determine the position lines of the RES as the lines of intersection of each of the auxiliary planes of the RES position with the surface of the Earth;

calculate the coordinates of the RES at the point of intersection of the RES position lines.

The disadvantage of the analogue is the relatively low accuracy of determining the coordinates of the RES in conditions of multipath propagation of radio waves, due to the impossibility of excluding measurements obtained from the wave reflected from various obstacles.

There is a known method for determining the location of a user terminal using two relay satellites according to RUS patent No. 2605457 [2], according to which the following sequence of actions is performed:

determine the distance between the first relay satellite (CP) CP ₁ and the user terminal (UT);

determine the distance between the second SR ₂ and PT;

measure modulus azimuth α _PT of the speed vector of the user terminal and its height h _PT relative to the earth's surface;

calculate Doppler frequency shifts in the UMS first and second narrowband test signals, determined by the radial velocities of the PT relative to CP ₁ and CP ₂ , for which the probable locations of the PT are preliminarily determined taking into account the known coordinates of CP ₁ , CP ₂ and certain parameters

determine at least one of the parameters: radial speed displacement of the first CP ₁ relative to the PT, and/or radial speed movement of the second SR ₂ relative to the PT, taking into account Doppler frequency shifts

calculate latitude ϕ _PT and longitude λ _PT PT.

The disadvantage of the analogue is the relatively low accuracy of determining the coordinates of the RES in conditions of multipath propagation of radio waves, associated with the low accuracy of primary measurements in the presence of re-reflections of radio waves from various objects.

Of the known methods, the closest analogue (prototype) of the proposed method in its technical essence is the difference-range-measuring method for determining the location of a radio emission source in conditions of multipath propagation of radio waves (MPRP) RUS No. 2714303 [3] consisting in the following:

at each of the receiving points (RP) with known coordinates, the IR signal is received and the time of arrival of the signal is measured from it,

for all possible pairs of PPs, the differences in arrival times of signals from the IR to the PP of this pair are calculated and the corresponding range differences are calculated from them,

form a set of intermediate coordinate estimates (IOC) of the IRI by determining the intermediate coordinate estimate for each possible combination of three PP using the difference-rangefinder method,

from the generated estimates, groups are formed, each of which contains at least four IRI QAPs,

for each formed group, the intragroup variance of the IRI SOC is calculated,

identify PPs that are in MRR conditions based on the excess of intragroup variances of the IRI POC of a predetermined threshold,

in the set of IRI QAPs, only those IRI QAPs are left that were obtained without the use of identified PPs located under MRRV conditions,

To obtain the final estimate of the IRE coordinates, the arithmetic mean of the remaining SOCs in the set is calculated.

The disadvantage of the prototype method [3] is the relatively low accuracy of determining the coordinates of the RES, due to the lack of taking into account the height of the RES, as well as the heights of the PP during measurements and calculations.

The technical result of the invention is to increase the accuracy of determining the coordinates of the RES in 3-dimensional space under MRR conditions.

The specified technical result is achieved by the fact that in the known difference-rangefinder method for determining the location of a radioactive source under MRR conditions, which consists in the fact that at each of the PPs with known coordinates the radio signal of the RES is received and, relative to the time of arrival of the radio signal from the RES, the differences are measured for all possible pairs of PPs arrival times of the radio signal from the IR to the PP of this pair and from them the corresponding range differences are calculated, a set of IR QA is formed by determining the QA for various combinations of PP using the difference-rangefinder method, from these estimates groups are formed, each of which contains at least four QA IRI, for each formed group, the intra-group variance of the IRI QAPs is calculated, identification of PPs under MRR conditions is carried out based on whether the intragroup variances of the IRI QAPs exceed a predetermined threshold, after which only those IRI QAPs that are obtained without using the identified PPs are left in the set of IRI QAPs , which are in MRRV conditions, to obtain a final estimate of the coordinates of the IR, the arithmetic mean of the remaining SOCs in the set is calculated, and the PPs are placed in 3-dimensional space. A set of IRI SOCs is formed by determining the SOCs in a 3-dimensional space using the difference-rangefinder method for each possible combination of four PPs that are not located in the same plane. After forming a set of IRI QAPs, groups are formed from these estimates, each of which contains at least four IRI QAPs. For each formed group, the intragroup variance of the IRI SOC is calculated. Identification of PPs under MRR conditions is carried out based on the excess of intragroup variances of the IRI POC of a predetermined threshold. In the set of IRI QAPs, only those IRI QAPs are left that were obtained without the use of identified PPs located under MRRV conditions. To obtain the final estimate of the coordinates of the RES, the arithmetic mean of the remaining SOCs in the set is calculated.

The PP is placed in 3-dimensional space so that the volume of the polyhedron formed by the vertices with points coinciding with the PP is maximum.

Measurements and calculations are performed in the Cartesian coordinate system OXYZ.

Thanks to the specified new set of essential features, including due to the placement of the PP in 3-dimensional space and the formation of a set of IRI QAPs by determining the QAP in 3-dimensional space using a difference-rangefinder method for each possible combination of four PPs, the technical result of the invention is achieved: increased accuracy of determining the coordinates of the RES in 3-dimensional space under MRR conditions. The claimed method is illustrated by drawings, where:

in fig. Figure 1 shows the RES signal s _and (t) and the signals s _i (t), i=1, 2, ..., N, received in the i-th PP;

in fig. Figure 2 shows the IR, geographically distributed PPs and the distances d _i between the IR and the i-th PP in the selected DSK OXYZ;

in fig. Figure 3 shows the IRI, two geographically distributed PPs, the geometric location of points on the plane in the form of a part of a two-sheet hyperboloid of rotation L _ij formed by the difference in distances d _i and d _j in the selected DSC OXYZ;

in fig. Figure 4 shows the geometric influence of the effect of the lack of line of sight on the error in determining the location using the difference-rangefinder method in the selected OXYZ DSC;

in fig. Figure 5 shows an example of intermediate estimates of the coordinates of determining the location of the RES using the difference-rangefinder method when using five PPs in line of sight conditions (LOS, Line Of Sight);

in fig. Figure 6 shows an example of intermediate estimates of the coordinates of determining the location of the RES using the difference-rangefinder method when using five PPs in conditions of no line of sight (NLOS, Non Line Of Sight);

in fig. Figure 7 shows an example of the empirical dependence of the dispersion of coordinate estimates on the signal-to-noise ratio (SNR);

in fig. Figure 8 shows an example of an IRI and six geographically distributed PPs in the selected DSK OXYZ;

in fig. Figure 9 shows an example of the dispersion of IRI SOCs for various groups of PPs in the selected DSC OXYZ;

in fig. 10 shows an example of a functional diagram for implementing the proposed method;

in fig. Figure 11 shows a block diagram of the algorithm for implementing the proposed method.

According to FIG. 10, the functional diagram for implementing the proposed method includes the following series-connected blocks:

- a unit for measuring the time of arrival of a signal at each receiving point and determining its own coordinates of the PP using Global Navigation Satellite Systems (GNSS) modules;

- a block for calculating the difference in the arrival times of the signal from the IR to the PP of this pair and calculating the corresponding range differences;

- a block for generating a set of all possible combinations from four receiving points and calculating a set of intermediate coordinate estimates (IOC) of the IRE using the difference-rangefinder method for each of the generated combinations;

- block of group processing of POC, assessment of intragroup dispersion of POC and identification of PPs under MRR conditions;

- a block for calculating the final estimate of the coordinates of the RES based on the arithmetic mean from a set of intermediate estimates of the coordinates of the RES, taking into account the identified PPs located in MRR conditions.

Implementation of the proposed method in the device shown in Fig. 10 taking into account the flowchart of the algorithm shown in FIG. 11, and also FIG. 1-9 is carried out as follows.

Determination of location using the difference-rangefinding method is carried out on the basis of processing the measured differences in the arrival times of signals (see Fig. 1) received from a radio source I by synchronized geographically distributed N receiving points K ₁ , K ₂ , ..., K _i , ..., K _N ( see Fig. 2).

The signal received by the i-th receiving point can be represented by the expression s _i (t)=α _i s _and (tt _i )+n _i (t), i=1, 2, …, N, where the received signal α _i s( tt _i ) is a delayed copy of the transmitted signal s _and (t) by t _i =d _i /c, weakened by α _i times when propagating over a distance d _i between the source and the i-th receiving point; n _i {t) - noise at the location of the i-th receiving point; c is the speed of light.

The initial data for the proposed difference-rangefinding method are the known coordinates of the PP, obtained by means of GNSS modules, as well as the times of arrival of the signal from the IR measured at each PP. Knowing the arrival times, it is possible to calculate the differences in the arrival times of signals Δt _ij =t _i -t _j , i,j=1, 2, …, N, i≠j, from which the differences in ranges Δd _ij =d _i -d _j =с are calculated ⋅Δt _ij , where d _i is the distance between the RES and the i-th PP (see Fig. 2); d _j is the distance between the IRI and the j-th PP.

Let (x _i , y _i , z _i ) be the coordinates of the i-th PP K _i , (x _j , y _j , z _j ) be the coordinates of the j-th PP K _j , (x ₀ , y ₀ , z ₀ ) - unknown coordinates of the IRE, then d _i and d _j are determined by known formulas [4]

The difference in ranges Δd _ij =d _i -d _j makes it possible to construct part of a two-sheet hyperboloid of rotation L _ij in the selected DSC OXYZ - the geometric locus of points in the plane for which the absolute value of the difference in distances from the IRI I to a pair of points K _i and K _j is constant (see Fig .3).

When determining the location of the RES in 3-dimensional space, it is necessary to find the intersection of at least three two-sheet hyperboloids of revolution, for example, L ₁₂ , L ₁₃ and L ₁₄ , which requires at least four PPs K ₁ , K ₂ , K ₃ , K ₄ .

Let's consider a qualitative example of the influence of the effect of the lack of line of sight NLOS (Non-Line-Of-Sight) in conditions of multipath propagation of radio waves at one of the PPs on the accuracy of determining the location using the difference-rangefinder method (see Fig. 4).

In the presence of LOS (Line-Of-Sight), each measurement of the range difference Δd _ij determines a two-sheet hyperboloid of rotation, and the intersection of at least three two-sheet hyperboloids of rotation determines the location of the IRE. In fig. Figure 4 shows a situation when 4 PPs are involved in determining the location: 3 receiving points K ₁ , K ₂ , K ₄ have line-of-sight LOS measurements; one receiving point K ₃ is covered by an obstacle W from the RES and has NLOS measurements obtained as a result of re-reflection from the reflector V, which leads to an increase in the rangefinder measurement from d ₃ to This error will lead to the fact that when determining the coordinates of the RES using the difference-rangefinder method, instead of the coordinates of point I, the coordinates of point I' will be determined.

In the claimed invention, PPs with no line of sight are identified and then excluded from the process of determining the location of the RES.

In general, the number of PP pairs is determined by the binomial coefficient from n to k, or the number of combinations from n to k.

In each pair of PPs, the difference in signal arrival times Δt _ij can be measured,

from which it is possible to calculate the difference in ranges Δd _ij and construct the corresponding two-sheet hyperboloid of rotation L _ij . If all PPs are in line-of-sight LOS conditions, then the hyperboloids of rotation intersect at one point - the true location of the IRE.

In practice, due to the influence of noise, estimation errors Δd _ij arise, and two-sheet hyperboloids of rotation L _ij deviate from the location point of the RES. However, for most real-life situations these deviations will be small.

As a sign by which it is possible to identify a PP that is in NLOS conditions, it is proposed to use the intragroup dispersion of intermediate estimates of the coordinates of the IRI, the essence of which is convenient to explain with an example. Let's consider a group of five PPs under line-of-sight conditions (LOS, Line Of Sight) (see Fig. 5) and the same group under non-line of sight conditions (NLOS, Non Line Of Sight) (see Fig. 6).

The dispersion of the IRI POC group can be quantitatively assessed using the intragroup dispersion D=((r ₁₂₃₄ ) ² +(r ₁₂₃₅ ) ² +(r ₁₂₄₅ ) ² +(r ₁₃₄₅ ) ² +(r ₂₃₄₅ ) ² )/5, where r ₁₂₃₄ , r ₁₂₃₅ , r ₁₂₄₅ , r ₁₃₄₅ , r ₂₃₄₅ - removals, respectively, of the POC M ₁₂₃₄ , M ₁₂₃₅ , M ₁₂₄₅ , M ₁₃₄₅ , M ₂₃₄₅ from the average coordinates M _av = (x _cp , y _cp , z _cp ) of a group of five PP .

If all PPs are in line-of-sight LOS conditions, then the spread of the IR SOC will be small, due only to the influence of noise (see Fig. 5). If some PPs are in conditions where there is no direct visibility of the NLOS, then the scatter of the SOC of the IRI will be large, due to both the influence of noise and the deviation of the two-sheet hyperboloids of rotation from the IRI (see Fig. 6).

To identify receiving points located in conditions of lack of line of sight (multipath propagation of radio waves), it is proposed to compare the intragroup dispersion D with a certain empirical threshold D _pores .

If the variance D exceeds the threshold D>D _pop , then in a group of four PPs one or more receiving points are in NLOS conditions.

If the variance does not exceed the threshold D≤D _pop , then all PP groups are in LOS conditions. To obtain the empirical threshold D _pop, it is possible to use the previously obtained empirical dependence of the dispersion of the coordinate estimate on the signal-to-noise ratio SNR (see Fig. 7).

Having only five PPs, the proposed method can only establish the fact that there is no line of sight at one or more PPs.

To identify which specific PPs are under NLOS conditions, more than five PPs are needed. Let's explain this with an example. Let there be six PPs (N=6) (see Fig. 8). From six PPs, six groups of five PPs can be made S _5/6 ={F ₁₂₃₄₅ , F ₁₂₃₄₆ , F ₁₂₃₅₆ , F ₁₂₄₅₆ , F ₁₃₄₅₆ , F ₂₃₄₅₆ }, F _ijkmg ={K _i , K _j , K _k , K _m , K _g }, i≠j≠k≠m≠g, where F _ijkmg is a group of five PPs K _i ., K _j , K _k , K _m and K _g .

For each group, you can obtain four IRI SOCs and find their intragroup variance. Let again, under NLOS conditions, K ₂ , then the groups F ₁₂₃₄₅ , F ₁₂₃₄₆ , F ₁₂₃₅₆ , F ₁₂₄₅₆ , F ₂₃₄₅₆ will have a large within-group variance, since they include K ₂ , and the group F ₁₃₄₅₆ will have a small within-group variance, since it does not include K ₂ (see Fig. 9).

Therefore, to identify PPs located in NLOS (multipath propagation of radio waves) conditions, it is necessary to determine which receiving points are repeated in all groups with intragroup dispersion exceeding a given threshold. After this, in all groups it is necessary to remove from processing all IRI QAPs that were obtained using the identified PPs. The final estimate of the coordinates of the IRE can be found by averaging the remaining POK of the IRE, for example, by calculating their arithmetic mean.

Taking into account these features, to implement the claimed invention, the following sequence of actions is sequentially performed:

- place a plurality of signal receiving points in 3-dimensional space; in these PPs they receive a signal from the IR and measure the time of arrival of the measured signal, as well as determine their own coordinates, for example, through GNSS modules, which also solve the problem of local synchronization of geographically distributed PPs;

- from the entire set of PPs, all possible pairs of PPs are made; for each pair of PPs, the difference in the arrival time of the signal from the IR to the PP of this pair is measured; from the measured difference in the arrival time of the signal from the RES in each pair, the difference in distances from the RES to the receiving points of this pair is calculated;

- from the entire set of PPs, all possible combinations of four receiving points are formed; for each combination of four receiving points, the coordinates of the RES in 3-dimensional space are found using the difference-rangefinder method, which are taken as an intermediate estimate of the coordinates of the RES; thus forming a set of POK IRI.

- from a set of QAPs, all possible groups of four QAPs are made;

- for each group, the intragroup dispersion of the IRI POK is calculated;

- the calculated intragroup dispersion of the IRI SOC of each group is compared with a given empirical threshold; they believe that the excess of the intragroup dispersion of a given threshold means the presence in this group of PPs who are in conditions of MRR;

- for each group in which the intragroup dispersion exceeded the threshold, the PP included in its composition are remembered; identified PPs under MRRV conditions include those PPs that are repeated in all groups with intragroup dispersion exceeding a given threshold;

- from the set of IRI QAPs, QAPs that were obtained using identified PPs located under MRRV conditions are excluded;

- calculate the final estimate of the coordinates of the irI in 3-dimensional space based on the updated set of QAPs of the IRI, taking into account the excluded QOCs obtained using the identified PPs located in the MRR conditions.

Simulation modeling of the claimed method for determining the location of RES in special Matlab software [5] showed an increase in the accuracy of measuring the coordinates of the source of radio emissions compared to the prototype method by 10...20% (depending on the relative position of the RES and PP), when solving the problem of estimating the location of the RES by the only measured signal under conditions of multipath propagation of radio waves, which indicates the possibility of achieving the specified technical result.

INFORMATION SOURCES

1. Bogdanovsky S.V., Dedovskaya E.G., Sevidov V.V., Simonov A.N., Fokin G.A. A method for determining the coordinates of a radio emission source from an aircraft using a triorthogonal loop antenna system. Patent No. 2709607. IPC G01S 5/04 (2006.01). Bull. No. 35 dated 12/19/19. Application No. 2019100254 dated 01/09/2019.

2. Volkov R.V., Sayapin V.N., Sevidov V.V. A method for determining the location of a user terminal using two relay satellites. Patent No. 2605457. IPC G01S 5/00 (2006.01). Bull. No. 35 dated 12/20/16. Application No. 2015139916 dated 09/18/15

3. Borisov E.G., Fokin G.A., Simonov A.N., Sevidov V.V. Difference-rangefinder method for determining the location of a radio emission source in conditions of multipath propagation of radio waves. Patent No. 2714303. IPC G01S 5/06 (2006.01). Bull. No. 5 from 02.14.20. Application No. 2019115359 dated May 20, 2019.

4. Anufriev A.A., Bogdanovsky S.V., Sevidov V.V., Chirkin P.M., Shipunov V.A. Iterative Newton-Raphson algorithm in the difference-range coordinate system. Journal "Scientific Thought". T. 8. No. 2(32). - Cherepovets: ChVVIURE, 2019. pp. 72-78.

5. Sevidov V.V. A program for assessing the accuracy of a difference-range-measuring coordinateometry system that implements the Newton-Raphson iterative method. Computer program. Certificate of registration of a computer program 2022669149, 10/17/2022. Application No. 2022668341 dated 10.10.2022.

Claims (3)

1. A difference-range-measuring method for determining the location of a source of radio emission (ER) in conditions of multipath propagation of radio waves (MRW), which consists in the fact that at each of the receiving points (RP) with known coordinates they receive a radio signal of the IRE and relative to the time of arrival of the radio signal from the IRE for all possible pairs of PPs, the differences in the arrival times of the radio signal from the IR to the PP of this pair are measured and the corresponding range differences are calculated from them, a set of intermediate estimates of the coordinates (IOC) of the IR is formed by determining the difference-rangefinder method for various combinations of PPs, from these estimates they form groups, each of which contains at least four IRI QAPs, for each formed group the intragroup dispersion of IRI QAPs is calculated, identification of PPs under MRR conditions is carried out based on whether the intragroup variances of IRI QAPs exceed a predetermined threshold, after which only those IRI QAPs are left in the set of IRI QAPs RES, which are obtained without the use of identified PPs located in MRRV conditions, to obtain a final estimate of the coordinates of the RES, the arithmetic mean of the remaining QOCs in the set is calculated, characterized in that the PPs are placed in 3-dimensional space, and the set of RF QOCs is formed by determining the difference-rangefinder using the POC method in 3-dimensional space for each possible combination of four PPs that are not located in the same plane, after forming a set of POC IRIs, groups are formed from these estimates, each of which contains at least four POC IRIs; for each formed group, the intragroup variance is calculated QAP IRI, identification of PPs under MRRV conditions is carried out on the basis that intragroup variances of QAP IRI exceed a predetermined threshold, after which only those QAP IRIs that are obtained without using the identified PPs under MRRV conditions are left in the set of QAP IRIs, and to obtain of the final estimate of the IRE coordinates, the arithmetic mean of the remaining SOCs in the set is calculated. 2. The method according to claim 1, characterized in that the PP is placed in 3-dimensional space so that the volume of the polyhedron formed by the vertices with points coinciding with the PP is maximum. 3. The method according to claim 1, characterized in that measurements and calculations are performed in the Cartesian coordinate system OXYZ.

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