Radiation source passive positioning method based on multi-point received signal strength

Abstract

The invention discloses a radiation source passive positioning method based on multi-point received signal strength, and belongs to the technical field of passive positioning. The method comprises the following steps: acquiring signal intensity received by a single motion platform at N moments or N point positions of a plurality of platforms and corresponding platform positions, constructing a coarse grid at a central value of the receiving platform position, calculating a distance from each grid point to the receiving platform position, calculating a corresponding theoretical attenuation value according to a signal propagation model, and calculating the signal intensity according to the theoretical attenuation value. The difference between the received signal strength and the predicted theoretical attenuation value of the grid point is calculated, the standard deviation of the signal strength difference is calculated to construct a cost function, and the position corresponding to the maximum value of the cost function of each point on the two-dimensional grid is searched to obtain a rough estimation position; and further constructing a fine grid around the roughly estimated position, and obtaining the position of the radiation source by using the method. The method does not need to estimate a real emission signal intensity value, and can eliminate the influence caused by the inaccurate estimation of the real power of the radiation source as much as possible.

Description

Technical Field

[0001] The present invention relates to the technical field of passive positioning, and in particular to a method for estimating the position of a radiation source by measuring the signal strength of a non-cooperative radiation source received at multiple points. Background Art

[0002] Passive positioning systems estimate the location of non-cooperative radiators, such as communication stations, interference sources, and black broadcasts, by passively receiving their radio signals and measuring their parameters. This is crucial for electronic reconnaissance, spectrum monitoring, and situational awareness. Common passive positioning techniques include direction-finding cross-location, time-difference positioning, time-frequency difference positioning, and signal strength (amplitude) positioning. Received Signal Strength (RSS) positioning requires only a single receiving channel for positioning, offers simple hardware and low cost, and holds broad application prospects in electromagnetic spectrum monitoring.

[0003] After searching, a Chinese patent (patent publication number CN103945529B) proposed a wireless sensor network positioning method based on RSS, which transforms the grid-based target signal positioning problem into a compressed sensing problem, and uses the compressed sensing method and geometric multilateration to locate the target signal. A Chinese patent (patent publication number CN116669178A) proposed a radio positioning method based on signal strength distribution similarity, which selects several signal source positioning points with calculated signal strength similarity in a preliminarily determined signal source area, and selects the signal source positioning point corresponding to the minimum signal strength similarity as the positioning position of the signal source. A Chinese patent (patent publication number CN19342412A) proposed an indoor positioning method, system, device and medium based on a signal three-dimensional fingerprint library, which scans the indoor space area and records the motion data of the scanning device and the signal data of each signal transmitter; and performs three-dimensional mapping of the target area to realize positioning calculation.

[0004] However, in practical applications, the actual effect of the above-mentioned existing methods is affected by multipath fading during signal propagation and amplitude measurement errors in the measurement process. Moreover, it is difficult to have prior knowledge when locating the actual non-cooperative radiation source, and it is impossible to obtain its possible area, possible point position and its actual transmission signal strength value. Therefore, the above-mentioned method is limited in practical application, resulting in poor positioning effect, or requiring advance modeling and data collection training for the area, which results in high costs and prices. Therefore, how to estimate the position of the radiation source by multi-point measurement of the received ground non-cooperative radiation source signal strength (RSS) by omnidirectional receiving antennas at multiple times or multiple different platform positions on a single moving platform (typically a drone, manned aircraft, car, ship, etc.) is a technical problem to be solved. Summary of the Invention

[0005] The present invention aims to provide a passive positioning method for radiation sources based on multi-point received signal strength, which solves the problem that existing non-cooperative radiation source positioning methods have poor effects in practical applications.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows: a passive positioning method for a radiation source based on multi-point received signal strength comprises the following steps:

[0007] S1. Obtain the radiation source signal strength measured at N different locations and the latitude and longitude of the signal receiving end;

[0008] S2. Obtain the receiving position of the signal receiving end when all signals are received, and obtain the center point of all the receiving positions;

[0009] S3. Draw a uniform two-dimensional grid with 1 grid point at the center point within a first distance range;

[0010] S4. Calculate the distance r between each grid point in the two-dimensional grid and the signal receiving end at each moment i,n ,According to the signal propagation model, the predicted distance attenuation value is obtained;

[0011] S5. Calculate the difference between the measured signal strength and the predicted range attenuation value of each grid point;

[0012] S6. Based on the standard deviation of the signal strength difference obtained in step S5, a cost function is constructed, and the location of the maximum value of the cost function in all two-dimensional grids is searched as a rough estimate point of the radiation source position;

[0013] S7. Draw a uniform two-dimensional grid with the roughly estimated point of the radiation source position as the center point and the second distance range, and repeat S4-S6 to obtain the precisely estimated point of the radiation source position, wherein the second distance range is smaller than the first distance range.

[0014] The technical principle and effect of this scheme: This scheme first roughly estimates the approximate position of the radiation source through a coarse grid, and then uses a fine grid with this as the center to accurately estimate the position of the radiation source, which can reduce the amount of calculation while maintaining a high positioning accuracy.

[0015] Furthermore, the calculation of the distance attenuation value in step S4 needs to be based on the distance value r between each grid point in the two-dimensional grid and the signal receiving end at each moment. i,n The logarithmic path attenuation coefficient of the signal propagation model is calculated using the following formula:

[0016] L i,n =-10ηlog 10 r i,n ;

[0017] Where i = 1, …, I is the grid point number, n = 1, …, N is the collection point number, and η is the logarithmic path attenuation coefficient, which ranges from 2.0 to 6.0. The typical value is 2.0 for direct line-of-sight propagation between air and ground. For other scenarios, such as mountainous and urban environments, reference is made to relevant wireless propagation model literature.

[0018] Furthermore, in step S5, the difference between the measured signal strength and the predicted signal distance attenuation value of each grid point is calculated. The specific calculation formula is as follows:

[0019] D i,n =P n -L i,n

[0020] Furthermore, the cost function constructed by the standard deviation in step S6 is as follows:

[0021]

[0022] Furthermore, the first distance range is the maximum distance at which a signal may be received, and the second distance range is typically one tenth of the first distance range.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention adopts the standard deviation calculation method of the difference between the predicted signal distance attenuation value and the measured signal strength, rather than directly constructing the cost function through the signal strength difference. There is no need to estimate the actual transmitted signal strength value, which can minimize the impact of inaccurate estimation of the true power of the radiation source.

[0025] (2) This scheme adopts a two-level grid search method, that is, the coarse grid roughly locates and then guides the fine grid to finely locate, so that the radiation source position can be searched globally within a large coverage area. At the same time, the problem of large computational complexity caused by dense grid search is reduced, and there is no need for a priori area and possible point locations of the radiation source.

[0026] (3) This scheme takes into account the impact of all signal strength measurements on the positioning of the radiation source, avoiding the possible inaccurate positioning caused by discarding a large amount of measured signal strength data, and improving the accuracy of positioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the total signal strength acquisition process of the single motion platform passive positioning method based on received signal strength of the present invention;

[0028] Figure 2 This is a technical flow chart of the passive positioning of a single moving platform based on received signal strength in the present invention;

[0029] Figure 3 This is a diagram showing the motion trajectory of the signal receiving end and the geometric position of the radiation source in the case shown in this embodiment;

[0030] Figure 4 This is a graph showing the relationship between the distance between the signal receiving end and the radiation source, and the power of the received signal including noise versus time, as shown in the example of this embodiment;

[0031] Figure 5 is a cost function graph corresponding to the two-dimensional grid in step S3 of this embodiment;

[0032] Figure 6 It is the cost function graph corresponding to the two-dimensional grid in step S7 in this embodiment. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0034] Example

[0035] As attached Figure 1 As shown, suppose there is a radiation source located at X t In order to obtain the location information of the radiation source in the radiation signal, the signal receiving end of this embodiment adopts an omnidirectional receiving antenna and its receiver mounted on a single moving receiving device (typically a drone, manned aircraft, car, ship, etc.) or multiple fixed devices at different locations. Assume that the radiation source signal strength P measured by the receiver mounted on the platform is obtained during the movement of a single moving receiving device or at N different locations. n (typical unit is dBm), n = 1, ..., N, and record the latitude and longitude position X of the signal receiving end at this time n =[B n ,L n ,H n ] T , where B n is latitude, L n is longitude, H n is the height, the superscript "T" represents the matrix transposition, and n=1, ..., N. After obtaining these data, the method of the present invention can be used to calculate the position of the radiation source.

[0036] As attached Figure 2 As shown, the passive positioning method of the radiation source based on the multi-point received signal strength includes the following steps:

[0037] S1. Obtain the signal strength P of multiple radiation sources in a certain frequency band (or frequency point) through the signal receiving end n, n=1,…,N, and record the latitude and longitude high position X of the signal receiving end at this time n =[B n ,L n ,H n ] T , where B n is latitude, L n is longitude, H n is the height, the superscript “T” represents the matrix transpose, n=1,…,N.

[0038] S2. Obtain the position X of the signal receiving end at the time when the signal receiving end detects the corresponding signal. n , n=1,…,N, and the center point of all signal receiving end positions is calculated using the following formula:

[0039]

[0040] S3, the first distance range R is near the center point of all signal receiving end positions. max Construct a uniform two-dimensional grid (i.e., a coarse grid), which is represented as follows:

[0041]

[0042] S4. Calculate each grid point X in the two-dimensional grid i The distance value r to the signal receiving end at each moment i,n ,i==1,…,I,n=1,…,N.

[0043] The above distance values require calculation of the corresponding distance attenuation value based on a signal propagation model (such as the free-space propagation model, ITU-R P.1546 model, Okumura-Hata model, or Egli model). The specific formula is as follows:

[0044] L i,n =-10ηlog 10 r i,n ;

[0045] Where i = 1, …, I is the grid point number, n = 1, …, N is the collection point number, and η is the logarithmic path attenuation coefficient, which is between 2.0 and 6.0 (the typical value is 2.0 for direct-view free-space propagation in open space. For other scenarios, such as mountainous and urban environments, refer to relevant wireless propagation model literature).

[0046] S5. Calculate the difference between the measured signal strength and the signal distance attenuation value of the predicted signal strength at each grid point. The specific calculation formula is as follows:

[0047] D i,n =P n -Li,n ,i==1,…,I,n=1,…,N.

[0048] S6. Calculate the standard deviation of the signal strength difference in step S5 and construct a cost function:

[0049]

[0050] At the same time, search for the location with the maximum value of the cost function in the two-dimensional grid as the rough estimate of the radiation source location:

[0051]

[0052] S7, roughly estimate the radiation source position in step S6 As the center point, again with the second distance range R' max Construct a two-dimensional grid (i.e., a fine grid), R′ max <R max The second distance range is one tenth of the first distance range (the typical search range is the search step of the two-dimensional grid in step S3), and the radiation source position can be accurately estimated by repeating steps S4-S6. And it serves as the output result of the final positioning.

[0053] Case display:

[0054] The motion trajectory of the signal receiving end and the geometric position of the radiation source of the present invention are shown in the figure below: Figure 3 To illustrate the positioning effect of the present invention, assume that the signal receiving end starts from the latitude and longitude [28.2221°N, 112.9844°E], at an altitude of 150m, flies northeast at a speed of 20m / s and a heading of 45°, and then turns southeast and flies at a heading of 135° after reaching a certain point. Assume that the actual position of the radiation source is at [28.2211°N, 112.9894°E]( Figure 3 The radiated power at 1 meter is -17 dBm (the "☆" point in the middle) and at an altitude of 50 meters. Assume the signal receiver measures the signal strength once per second for the entire 200-second motion, with a 1 dB error.

[0055] When using the passive positioning method of this embodiment for positioning, it is assumed that the coarse grid search range is 6km, the grid search step is 100m, and the assumed radiation source prior elevation is 100m; the fine grid range is 100m, and the grid search step is 2m. Finally, the passive positioning method can be used to search for the radiation source position value [28.2210°N, 112.9895°E]( Figure 3 The positioning error is calculated to be 10.9657 meters, indicating that the method of the present invention can accurately achieve high-precision positioning by utilizing multi-point signal strength.

[0056] The relationship between the distance between the signal receiving end and the radiation source and the power of the noise-containing received signal over time is shown in the following figure: Figure 4 As shown in the figure, in this embodiment, the distance between the signal receiving end and the radiation source varies from about 500m to 2000m. Due to the presence of noise in the signal strength measurement, the measured signal strength fluctuates between -70dBm and -85dBm.

[0057] The coarse grid cost function diagram of the present invention is as follows: Figure 5 As shown in the figure, there are two peaks around the radiation source within the entire 6km×6km range, indicating that the mapping from radiation source position to signal strength is highly nonlinear and that other methods are prone to falling into local minima. However, this passive positioning method can accurately estimate the radiation source position.

[0058] The two-dimensional grid cost function diagram of step S7 in the present invention is as follows: Figure 6 As shown in the figure, since the coarse grid is 100m, the positioning accuracy within 100m cannot be guaranteed. Therefore, a fine grid search is performed within the range of ±100m around the peak value found by the coarse grid search. This can further improve the positioning accuracy of the radiation source and thus obtain a more accurate radiation source position estimate.

[0059] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A passive positioning method for radiation sources based on multi-point received signal strength, characterized in that: The steps include: S1. Obtain the radiation source signal strength measured at N different locations and the latitude and longitude of the signal receiving end; S2. Obtain the receiving position of the signal receiving end when all signals are received, and calculate the center point of all receiving positions; S3. Draw a uniform two-dimensional grid with 1 grid point at the center point in a first distance range. S4. Calculate the distance r between each grid point in the two-dimensional grid and the signal receiving end at each moment i,n ,According to the signal propagation model, the predicted distance attenuation value is obtained; S5. Calculate the difference between the measured signal strength and the range attenuation value predicted by the grid point; S6. Based on the standard deviation of the signal strength difference obtained in step S5, a cost function is constructed, and the location of the maximum value of the cost function in the two-dimensional grid is searched as a rough estimate point of the radiation source position; S7. Draw a uniform two-dimensional grid with the roughly estimated point of the radiation source position as the center point and the second distance range, and repeat S4-S6 to obtain the precisely estimated point of the radiation source position, wherein the second distance range is smaller than the first distance range.

2. The method for passively locating a radiation source based on multi-point received signal strength according to claim 1, wherein: The calculation of the distance attenuation value in step S4 is based on the distance value r between each grid point in the two-dimensional grid and the signal receiving end at each moment. i,n The logarithmic path attenuation coefficient of the signal propagation model is calculated using the following formula: L i,n =-10ηlog 10 r i,n ; Where i = 1, …, I is the grid point number, n = 1, …, N is the collection point number, and η is the logarithmic path attenuation coefficient, which ranges from 2.0 to 6.

0. The typical value is 2.0 for direct line-of-sight propagation between air and ground. For other scenarios, such as mountainous and urban environments, reference is made to relevant wireless propagation model literature.

3. The method for passively locating a radiation source based on multi-point received signal strength according to claim 1, wherein: The standard deviation cost function of step S6 is constructed as follows:

4. The method for passively locating a radiation source based on multi-point received signal strength according to claim 1, wherein: The first distance range is the maximum distance at which a signal may be received, and the second distance range is typically one tenth of the first distance range.

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