RU2638177C1 - Method for determining source of radio emissions coordinate from aircraft - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: method is performed due to the operations for forming the position line of the radio emission source and calculating the coordinates of the point of intersection of the position line with the Earth's surface represented by the ellipsoid.

EFFECT: increasing the accuracy of determining the coordinates of the sources of radio emission at ranges up to an aircraft close to the radio horizon.

4 dwg, 3 tbl

Description

The invention relates to radio engineering and can be used to determine the location of a source of radio emission (IRI) from an aircraft (LA).

One of the elements of the methods for estimating the location of IRI and spatial selection used in passive goniometric systems is the determination of the coordinates of the IRI using two azimuth bearings obtained at two different points in space [1. Melnikov Yu.P. Aerial radio intelligence (methods for evaluating effectiveness). - M .: Radio engineering, 2005 .-- 304 p., P. 148], [2. Melnikov Yu.P., Popov S.V. Radio intelligence. Methods for assessing the effectiveness of the determination of radiation sources. - M .: Radio engineering, 2008 .-- 432 p., P. 11-64].

There is a method of determining the coordinates of a source of radio emission during amplitude-phase direction finding from an aircraft [3. A method for determining the coordinates of a source of radio emissions during amplitude-phase direction finding from an aircraft. Patent RU No. 2432590, IPC G01S 1/08, publ. 10/27/2011, bull. No. 30.], Adopted as a prototype, which includes: receiving radio signals from an onboard direction-finding antenna, performing frequency selection, determining bearing lines in the direction-finding antenna plane, registering and weighting the received data, and forming auxiliary planes orthogonal to the direction-finding antenna plane from the weighting results and passing through each received bearing line, determining the line of position of the source of radio emissions as the line of intersection of each auxiliary plane with the surface Tew earth and computing coordinates radiation source as line intersection point radio source position.

The disadvantage of the prototype method are:

- low accuracy of determining the coordinates of the IRI of the VHF range at ranges to aircraft close to the radio horizon when describing the Earth's surface by a plane [3, p. 7];

- high computational complexity of performing operations to determine the position line of the source of radio emissions as the intersection line of each auxiliary plane with the Earth's surface and to calculate the coordinates of the source of radio emissions as the point of intersection of the position lines of the source of radio emissions when describing the Earth's surface with an ellipsoid.

The high computational complexity of performing the operations of calculating the coordinates of the source of radio emissions as the point of intersection of the lines of position of the source of radio emissions is due to the nonlinearity of this computational problem in the case when the Earth's surface is described by an ellipsoid.

The aim of the invention is to improve the accuracy of determining the coordinates of the IRI VHF range at ranges to aircraft close to the radio horizon, with equivalent required computing costs.

To achieve this goal, a method is proposed for determining the coordinates of a source of radio emissions from an aircraft using two azimuth bearings, including receiving radio signals from an airborne direction-finding antenna, frequency selection, determination of bearing lines in the plane of the direction-finding antenna, recording and weighting the received data, based on the results of weight processing, forming auxiliary planes orthogonal to the direction-finding antenna plane and passing through each received bearing line.

According to the invention, find a straight line of intersection of the auxiliary planes and calculate the coordinates of the source of radio emissions as the point of intersection of the found straight line and the surface of the Earth described by an ellipsoid.

Achievable technical result is to increase the accuracy of determining the coordinates of the IRI VHF range at ranges to aircraft close to the radio horizon.

The indicated technical result is achieved by introducing new operations to form the IRI position line and calculating the coordinates of the intersection point of the position line with the Earth's surface described by an ellipsoid.

In FIG. 1 - coordinate systems used in the description of the method;

In FIG. 2 is a flowchart of operations that implement the proposed method;

In FIG. 3 - conditions under which the estimation of the methodological error in determining the coordinates of the IRI was carried out, associated with the representation of the Earth's surface by a plane;

In FIG. 4 is a structural diagram of a device that implements the proposed method.

The combination of distinguishing features and properties of the proposed method from the literature is not known, therefore, it meets the criteria of novelty and inventive step.

When describing the method, coordinate systems (SK) and their designations are used, which are listed in Table 1 and presented in FIG. 1. The relative position of the SC is described in [3, p. 5] [4. Mashimov M.M. Theoretical Surveying. - M .: Nedra, 1991 .-- 268 p., P. 6].

The method for determining the coordinates of the source of radio emissions from the aircraft on two azimuth bearings is implemented as follows.

1. Carry out the reception of radio signals on-board direction-finding antenna.

2. Perform frequency selection.

3. Determine the line of bearings ϕ in the plane of the direction-finding antenna.

4. Spend weight processing of the data.

5. According to the results of weight processing, auxiliary planes are formed, orthogonal to the direction-finding antenna plane and passing through each received bearing line.

6. Find a straight line of intersection of the two auxiliary planes.

7. The coordinates of the IRI are calculated as the intersection point of the found straight line and the surface of the Earth described by an ellipsoid.

To implement paragraph 5, the coordinates of the aircraft at the time of receiving bearings are transferred to a geocentric rectangular coordinate system according to the formulas [4, p. fourteen]

x ^hPSC = (N + H) cosBcosL;

y ^hPSC = (N + H) cosBsinL;

z ^HPSC = ((1-e ² ) N + H) sinB,

where e is the eccentricity of the ellipsoid of the Earth;

N is the radius of curvature of the normal section of the Earth's ellipsoid in the plane of the first vertical;

B, L, H - latitude, longitude and altitude of the aircraft at the time of receiving the bearing.

Then they compose a transition matrix from SSC to NPSC [3, p. 6]

A _{SSK → NPSK} = A ^γ ⋅A ^θ ⋅A ^ψ ,

where And ^γ is the matrix of rotation of the SSC by the angle of heel γ LA around the axis Ox;

A ^θ is the matrix of rotation of the CCK by the pitch angle θ of the aircraft around the axis Oz;

A ^ψ is the matrix of rotation of the SSC on the yaw angle ψ of the aircraft around the axis Oy:

;

;

;

;

.

.

They compose a transition matrix from NPSC to HPSC [4, p. eighteen]:

.

.

Three points for constructing the auxiliary plane are selected in the SSC as follows:

,

,

,

,

,

,

where ϕ is the azimuthal bearing of the IRI.

The transfer of known points for constructing a plane from SSC to GPSC is carried out according to the formula

;

;

;

;

.

.

The position of the auxiliary plane in space is given by the expression [3, p. 7]

Ax + By + Cz + D = 0,

The coefficients A, B, C, D can be found using the following formulas [3, p. 7]:

;

;

;

;

;

;

To implement paragraph 6, they solve a system of equations that defines a straight line as the intersection of two planes in space:

A straight line in space can also be represented parametrically [5, Bugrov Ya.S. Higher mathematics: Textbook. For universities: In 3 vols., T. 1: Elements of linear algebra and analytic geometry. - M .: Drofa, 2004 .-- 288 p., P. 90]:

where v = (ν _x ν _y ν _z ) is the directing vector of the line;

q = (q _x , q _y , q _z ) is an arbitrary point belonging to a line,

λ is a parameter.

In the case where the line is the intersection of two planes,

,

,

where n ₁ and n ₂ are the normals to the intersecting planes,

× is the operation of a vector product.

Then, setting q ₃ = 0 due to the arbitrariness of the point q, from (1) we obtain

;

;

.

.

To implement paragraph 7, a system of equations is determined that determines the intersection point of the found straight line and the Earth's surface, described by an ellipsoid, which has the following form:

where a and b are the major and minor semiaxis of the ellipsoid describing the surface of the Earth.

This system of equations is reduced to one equation with respect to the parameter λ:

and λ ² + bλ + c = 0,

Where

;

;

b = 2b ² (ν _x q _x + ν _y q _y ) +2 a ² ν _z q _z ;

.

.

The resulting equation is a quadratic equation for the parameter λ. Its roots are found by the following formula:

,

,

where D = b ² -4 a s.

и

. Одна из этих точек является ложной в силу неоднозначности операции извлечения корня. Исходя из геометрического смысла, истинным положением ИРИ является та точка, расстояние от которой до ЛА является минимальным. Вторая точка лежит на противоположной от ЛА стороне эллипсоида и не находится в пределах радиогоризонта пеленгаторной антенны. Расстояние между ЛА и предположительными местоположениями ИРИ вычисляется по формуле:Returning to expressions (2), we obtain the coordinates of two points

and

. One of these points is false due to the ambiguity of the root extraction operation. Based on the geometric meaning, the true position of the IRI is that point, the distance from which to the aircraft is minimal. The second point lies on the opposite side of the ellipsoid from the aircraft and is not within the radio horizon of the direction-finding antenna. The distance between the aircraft and the estimated locations of the IRI is calculated by the formula:

, i={1;2}.

, i = {1; 2}.

The coordinates of the true location of the Islamic Republic of Iran are transferred to the GESK and consider the received coordinates (IN _Iran , L _Iran , N _Iran ) the exact coordinates of the location of Iran.

The described operations on the formation of auxiliary planes orthogonal to the direction-finding antenna plane and passing through each bearing line, finding the straight line of intersection of the auxiliary planes, calculating the coordinates of the radio emission source as the intersection point of the found straight line and the Earth's surface, represented by an ellipsoid, are presented in the form of a block diagram on FIG. 2.

Thus, the proposed method has the following distinctive features in the sequence of its implementation from the prototype method, which are presented in table 2.

From the presented table comparing the sequences of implementations of the prototype method and the proposed method, it can be seen that in the proposed method relative to the prototype method, instead of determining the position line of the radio emission source as the intersection line of each auxiliary plane with the Earth's surface and calculating the coordinates of the radio emission source as the intersection of the lines of position of the radio emission source, find a straight line of intersection of the auxiliary planes and calculate the coordinates of the source of radio emissions as the points of intersection of the found straight line and the Earth’s surface, which leads to a positive effect - a reduction in computational costs and increased accuracy in describing the Earth’s surface with an ellipsoid.

Assessment of the methodological error in determining the coordinates of the IRI associated with the representation of the Earth's surface by a plane was carried out for the following conditions (Fig. 3):

- two spatially spaced positions of the aircraft are determined by geodetic elliptic coordinates (WGS-84): 40.0000 ° N 50.0000 ° East 10,000.00 m (point T1) and 39.9764 ° N 57.3408 ° East 10,000.00 m (point T2);

- the plane that defines the model of the Earth is the plane of the local horizon passing through a point on the surface of the earth's ellipsoid with coordinates (WGS-84): 39.9941 ° N 56.1709 ° East 0.00 m (point T3);

- the position of the IRI is given by the coordinates (WGS-84): 42.6992 ° N 55.0000 ° East 0.00 m (point T4);

- the deviation of the planes of bearings of the IRI from points T1 and T2 passing through the corresponding normals of the direction-finding antenna from the planes of bearings of the IRI from the same points passing through the normals in them to the planes of the local horizon is of the order of 7 °;

- distances between points are presented in table 3.

For these conditions, the coordinates (WGS-84) of the intersection point of the bearing planes and the plane defining the Earth model: 42.7224 ° N 54.9902 ° East 7987.10 m (point T5), and its projection onto the earth's ellipsoid: 42.7224 ° N 54.9902 ° East 0.00 m (point T6).

Then, the errors in determining the coordinates of the IRI associated with the representation of the Earth in the form of a plane, defined as the distances between points T4-T5 and T4-T6, respectively, are 8432 m and 2700 m. If the earth ellipsoid is used as a model of the earth's surface, this component of the methodical error is to zero.

Therefore, the proposed method allows, in addition to reducing computational costs, to improve the accuracy of assessing the location of the IRI.

The structural diagram of a device that implements the proposed method is shown in FIG. 4. The IRI signal is fed to the airborne direction-finding antenna 1, then to the receiving device 2. In the receiving device 2, the signal is converted to an intermediate frequency. Then, the converted signal is fed to an analog-to-digital converter 3, which digitizes the signal. The digitized signal is fed to calculator 4, where frequency selection is performed, determination of bearing lines in the direction-finding antenna plane, registration and weight processing of the received data. Then, the calculator 4 implements the operations shown in FIG. 2. Data on the position of the aircraft in space comes from the navigation system of the aircraft 5. The result of the operation of the device is the coordinates of the IRI.

Thus, the proposed method, as well as the prototype method, allows you to determine the location of the IRI. In addition, the comparative evaluation of the effectiveness of the proposed method relative to the prototype method shows an increase in the accuracy of positioning and a reduction in computing costs. An experimental verification of the proposed method confirmed the correctness and sufficiency of technical solutions.

Claims (1)

A method for determining the coordinates of a source of radio emissions from an aircraft from two azimuth bearings, for the implementation of which radio signals are received by an on-board direction-finding antenna, frequency selection is performed, lines of bearings are determined in the direction-finding antenna plane, registration and weighting of the obtained data are carried out, auxiliary planes are formed by weighting results orthogonal planes of the direction-finding antenna and passing through each received bearing line, characterized in that they find a straight line of intersection of the auxiliary planes and calculate the coordinates of the source of radio emissions as the point of intersection of the found straight line and the Earth's surface, represented by an ellipsoid.

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