RU2674265C1 - Correlation and basic system of location of fixed sources of radio emission with use of unmanned aircraft - Google Patents

Abstract

FIELD: radio engineering and communications.SUBSTANCE: invention relates to the field of radio engineering, namely, to passive radar systems and can be used to quickly determine the coordinates of fixed sources of radio emission, including when their time and frequency signals are not resolved. Technical result of the invention is achieved: by placing a mobile receiving point on an unmanned aerial vehicle; simultaneous direction finding of all interrogated transmitters of interference, their sequential direction finding from several points of space with the joint processing of all bearings.EFFECT: technical result of the invention is to reduce the time to establish the location of each of several sources of radio emission when placed on a large area.1 cl, 7 dwg

Description

The correlation-basic system for locating stationary sources of radio emission using an unmanned aerial vehicle belongs to the field of radio engineering and, specifically, to passive radar systems and is designed to quickly determine the coordinates of stationary sources of radio emission, including when their signals are not resolved in time and frequency.

A known method for determining the coordinates of a source of radio emissions from an aircraft [1]. The disadvantage of this method and, as a consequence of the systems in which it can be implemented, is the inability to determine the coordinates of several sources of radio emission (IRI), the signals of which are not resolved by the receiving equipment according to the frequency and time of reception.

There is a device for searching for IRI type of abandoned interference transmitters (RFP) [2], which allows you to uniquely determine the location of each of several RFPs operating at the same frequency against the background of pulse signals of the radio electronic signals and inform the operator of his position relative to the detected RFP.

The disadvantages of the known device are:

the impossibility of realizing the potential accuracy of measuring the location of the IRI due to restrictions imposed on the trajectory of the search group by the IRI terrain features;

low speed of obtaining information about the location of the IRI due to the foot movement of the search group over rough terrain.

The operation of the known device is as follows.

The device consists of a movable and fixed receiving points connected by a data transmission channel.

Installation and inclusion of a fixed receiving center is carried out, after which a mobile receiving station located next to it is turned on. The mobile receiving station automatically determines its own coordinates and memorizing them, thus, the coordinates of the position of the stationary receiving station are entered into the mobile receiving station. At the same time, reception of the RFP signals by both receiving points is carried out, the received signal is transmitted from the fixed to the mobile receiving point, and the relative signal transmission delay introduced by the data channel is calculated. After that, the operator of the mobile receiving station starts moving to a new position.

The fixed receiving point, being a repeater of the ZPP signals, makes their constant reception and transmission over the communication line to the mobile receiving point. A mobile receiving point, similarly to a stationary receiving point, produces constant reception of STD signals. The received signals may contain interference signals generated by the RFP, as well as pulse signals of the RES, which the RFP creates interference. Both signals (received from a fixed receiving point and received by a mobile receiving point) are fed to a correlation detector that calculates the delay difference of the signals received by the receiving points. At the same time, corrections are made to the calculated difference for the previously measured signal delay introduced by the data channel, and the signal propagation time between receiving points over the communication channel. The last correction is calculated by the difference in the coordinates of the receiving points, taking into account the propagation velocity of the electromagnetic wave.

The measured delay in receiving the RFP signals by receiving points is used to draw lines of the possible position of the RFP (hyperbole).

The number of hyperbolas obtained for the fixed position of the receiving points corresponds to the number of emitting STDs.

Next, the mobile receiving center moves to a new position and the procedure for calculating hyperbolas is repeated. Since the mobile receiving station is equipped with a signal receiver of the satellite radio navigation system (navigation receiver), direction finding can be performed while the mobile receiving station is moving.

A change of position is performed until a sufficient number of hyperbolas has been accumulated to establish the location of the RFP.

To establish the location of one RFP, it is sufficient to have two hyperbolas taken from different positions.

As the closest analogue, the considered device [2] was selected.

The technical result of the invention is to reduce the time it takes to establish the location of each of several IRIs when they are deployed over a large area.

Correlation-base system for the location of fixed sources of radio emission using an unmanned aerial vehicle, containing a fixed point and a mobile receiving point, each of which has an antenna and a location receiver, the mobile receiving point has a navigation receiver, characterized in that the fixed receiving point consists of a transceiver antenna, antenna switch, attenuator, adder, precise synchronization pulse generator, portable personal computer, location receiver ka and the navigation receiver, and the transmitting and receiving antenna is connected to the antenna switch, the output of which is connected to the first input of the adder, the output of the adder is connected to the input of the location receiver, the output of the location receiver is connected to a portable personal computer, the output of the navigation receiver is connected to a portable personal computer, portable a personal computer is connected to the control input of the accurate synchronization pulse generator and the control input of the antenna switch; an accurate synchronization pulse generator is connected to the input of the antenna switch and the input of the attenuator, the output of which is connected to the second input of the adder, the mobile receiving station consists of an unmanned aerial vehicle with a receiving antenna, a location receiver, a microcomputer and a navigation receiver, the antenna being connected to the input of the location receiver, the outputs of the location and navigation receivers are connected to the microcomputer.

The correlation-base system for locating stationary sources of radio emission using an unmanned aerial vehicle is the correlation-base system for passive radar with a moving measuring base, and consists of:

fixed point;

mobile reception center.

The fixed point consists of (Fig. 1):

omnidirectional transceiver antenna (1);

antenna switch (2);

attenuator (3);

an adder (4);

precise synchronization pulse generator (5);

a portable personal computer (6) with specialized software that implements the functions of controlling the equipment of a fixed point and joint processing of information generated by both points;

location receiver (7), which is a wide-range superheterodyne radio receiver with digital output; navigation receiver (8).

A mobile receiving station (Fig. 2) consists of an unmanned aerial vehicle (9) with the following: a receiving antenna (10);

a location receiver (11) similar to a location receiver (7);

a microcomputer (12) with specialized software that implements the control functions of the equipment of a mobile reception center;

navigation receiver (13).

The device allows you to determine the location of fixed IRI located on the earth's surface, conventionally considered flat.

The location of the IRI is made by the difference-ranging method [3, p. 249] after the flight of the UAV (9) and its subsequent landing.

The essence of the differential-ranging method of determining the location is to calculate the line of the possible position of the IRI (second-order curve) corresponding to the constant difference in the time of reception of signals by two and (or) more receiving points.

When using two receiving points with known coordinates, and a known (measured) time difference between the moments of signal reception by receiving points, the possible location of IRI in three-dimensional space is described by one of the two surfaces of a two-sheeted hyperboloid of revolution [4, p. 43]. Surface selection (elimination of measurement ambiguity) is made according to the sign of the measured delay difference. Given the known coordinates of the receiving points and the condition that the source of radio emission is located on the earth's surface, the possible position of the source of radio emission will correspond to the curve formed by the intersection of the hyperboloid by the plane of the earth's surface. Assuming that the earth's surface in the search area can be conditionally approximated by a plane, the curves will be described by second-order equations (hyperbola, ellipse). The locations of the IRI are determined by the intersection of several curves obtained as a result of measurements of the delay in receiving the signal of the IRI by receiving points at various positions in the space of the measuring base. By measuring base is meant a segment connecting a pair of receiving points in space. Changing the position of the measuring base is achieved by moving the movable receiving point. The coordinates of the fixed point and the moving receiving point are determined using the navigation receivers (8) and (13). To determine the location of one IRI requires two to three measurements. One measurement should be understood as a measurement made at a fixed position of the measuring base. To determine the location of each of several IRIs, more measurements are required.

If there are two or more IRIs operating on the same carrier frequency, with a single measurement, differences in the reception times of each of their signals can be obtained. In this case, each difference in reception times will correspond to its own line of position of the IRI.

To accurately measure the delay in receiving a signal by a pair of receiving points, high-precision synchronization of their operation is required, which is achieved by using a synchronizing signal emitted by a fixed point. As a synchronizing signal, pulses with linear frequency modulation with a deviation equal to the passband of location receivers (7) and (11), with a duration of several tens of milliseconds and a repetition period of one second are used.

The fixed point implements the functions of generating and emitting accurate synchronization pulses and receiving them, receiving IRI signals, converting the received signals to digital form, and then recording them on a computer storage medium (MNI).

The mobile receiving station implements the functions of receiving accurate synchronization pulses, receiving IRI signals, converting the received signals to digital form, followed by their recording on a removable MINI.

Signals received by the points are processed after the UAV returns (landing) (9). Processing is carried out on a portable personal computer (6) with specialized software that implements the joint processing of information generated by fixed and mobile points. The processed information is entered into a portable personal computer (6) from the MNI extracted from the mobile receiving center.

The result of information processing are the IRI position lines corresponding to the possible IRI position on the earth's surface at fixed moments of the position of the measuring base in space. The Iranian position lines are displayed on the screen of a portable personal computer (6) in a geographical coordinate system. The points of intersection of the lines of position of the IRI are potential places of position of the IRI. The number of IRI and their coordinates are determined visually by the operator.

In FIG. Figure 4 shows the option of displaying the lines of position of the IRI in a rectangular coordinate system, in the presence of three IRI operating at the same frequency. The above display option is built by simulation method with the following initial data:

UAV flight altitude (9) 200 m;

flight path - a circle with a radius of 1 km centered at the location of a fixed receiving point (origin);

the number of measurements - 32 (points of the trajectory at which measurements were taken are indicated by filled circles);

the coordinates of the first IRI: x ₁ = 852 m, y ₁ = 238 m;

coordinates of the second IRI: x ₂ = -156 m, y ₂ = 369 m;

the coordinates of the third IRI: x ₃ = -1039 m, y ₃ = -953 m.

Precise synchronization pulses generated and emitted by a fixed point are designed to measure the delay in receiving IRI signals within the original signal samples. Precise synchronization pulses are emitted by a fixed point at the frequency of the search (work) of the IRI for the possibility of their reception by location receivers (7) and (11) in conjunction with the signals of the IRI.

To ensure reliable detection of accurate synchronization pulses by a mobile receiving point and accurate measurement of the moments of their reception in the correlation processing and indication system, their optimal reception has been implemented, which can significantly increase the ratio of the power of accurate synchronization pulses to the power of IRI signals.

The invention is illustrated by the following drawings:

FIG. 1 is a block diagram of a fixed point.

The numbers indicate:

1 - transceiver antenna;

2 - antenna switch;

3 - attenuator;

4 - adder;

5 - pulse generator accurate synchronization;

6 - portable personal computer;

7 - location receiver;

8 - navigation receiver.

FIG. 2 is a block diagram of a mobile receiving point.

The numbers indicate: 9-UAV;

10 - receiving antenna;

11 - location receiver;

12 - microcomputer;

13 is a navigation receiver.

The dotted line indicates the constructive relationship between the equipment and

UAV.

FIG. 3 - Structure of the system of correlation processing and indication.

The numbers indicate:

6.1 - file with data of a fixed point;

6.2 - data file of the mobile receiving point;

6.3, 6.4 - matched filters;

6.5, 6.6 - quadratic detectors;

6.7, 6.8 - threshold comparison blocks;

6.9 - block accurate time synchronization;

6.10 - digital delay line;

6.11, 6.12 - sampling blocks;

6.13 - correlator;

6.14 - block threshold comparison;

6.15 - calculator of the position lines of the IRI;

6.16 - display unit.

FIG. 4 Option to display the lines of position of the IRI, if there are three

IRI.

The following notation is used in the figure:

• - the position of the mobile receiving point at the time of receiving the samples;

ο is the position of the fixed point;

∇ - the location of the IRI.

FIG. 5 Timing diagrams explaining the operation of a fixed point at the data collection stage.

FIG. 6 Timing diagrams explaining the operation of a portable personal computer of a fixed point at the data processing stage.

FIG. 7 An example of a mutual correlation function (VKF) at the output of a correlator.

The operation of the device is as follows.

The device operation cycle consists of three stages: preparation (deployment + configuration);

data collection;

data processing.

At the preparation stage, the equipment is deployed, turned on and configured. Configuration consists in setting the frequency (frequency range) at which the IRI signals are searched and selecting one of the UAV flight programs. The frequency (range of frequencies) is set by entering the set values into the configuration file located on the portable personal computer (6) of the fixed point, then copying it to the PID and transferring the mobile receiving point to the microcomputer (12).

At the data collection stage, data collection programs are launched at receiving points and UAVs are launched. The UAV flies along the trajectory of a given program. Rational is an isotopic trajectory in the form of a circle or a spiral. The height of the trajectory is set to a minimum, provided it is safe. During a UAV flight, digital signals are simultaneously recorded by both points. The operation of digital signal recording equipment at both points is similar.

In addition to the recording procedure performed by both points, in the fixed receiving point for each clock signal from the navigation receiver (8), an accurate synchronization pulse is generated and emitted, which ensures that the exact synchronization pulse gets into the sample recorded by both points.

Timing diagrams explaining the operation of a fixed point at the data collection stage are shown in FIG. 5.

Rough synchronization of digital signal recording processes is performed by the second-second clock signals of the navigation receiver (8). The second-second clock signals of the navigation receiver (8) are shown in the graph ( a ) of FIG. 5. Using the clock signal from the navigation receiver (8), the portable personal computer (6) generates a trigger pulse for the accurate synchronization pulse generator (5) (graph (b) of FIG. 5) a trigger for the accurate synchronization pulse generator (5) and the antenna switch (2) in the "transfer" mode. The accurate synchronization pulse generator (5) generates an accurate synchronization pulse (graph (c) of Fig. 5), which is fed through the antenna switch (2) to the transmit-receive antenna (1). The exact synchronization pulse through the attenuator (3) and the adder (4) enters the location receiver (7). The type of signal at the input of the location receiver (7) is shown in the graph (d) of FIG. 5. From the output of the location receiver (7), the digital signal enters a portable personal computer (6) where a sample of a given volume ((e) of Fig. 5) is selected. The selected sample is written to a file, the name of which is used the current date and time values received from the navigation receiver (8). The current coordinates of the fixed point (longitude, latitude, height) received from the navigation receiver (8) are recorded in the same file.

The operation of the equipment of the mobile receiving point occurs in the following sequence.

Rough synchronization of digital signal recording processes is performed by the second-second clock signals of the navigation receiver (13). The second-second clock signals of the navigation receiver (13) are similar to those shown in the graph ( a ) of FIG. 5. Using the clock signal from the navigation receiver (13), the microcomputer (12) extracts a sample of a given volume from a digital signal from the output of the location receiver (11). The selected sample is written to a file, the name of which is used the current date and time values received from the navigation receiver (13). The current coordinates of the mobile receiving point (longitude, latitude, height) received from the navigation receiver (13) are recorded in the same file.

At the end of the flight program, the UAV lands near a fixed point.

The MNI containing the recorded data is extracted from the microcomputer (12) located on the UAV (9). Data from the PIM is copied to a portable personal computer (6), after which the program for processing them is launched.

At the data processing stage, the lines of position of the IRI are calculated and displayed on the screen of a portable personal computer (6). Data processing is carried out according to an algorithm containing three stages.

At the first stage, a rough time synchronization of the processed data is performed by compiling a list of pairs of files of the same name (recorded simultaneously by two points). Files left without a pair are deleted.

At the second stage, the filtering of the signal sample from each file (6.1) and (6.2) is performed and their mutual exact time synchronization. The type of signals of the initial samples of the mobile receiving station and the fixed station is shown in graphs ( a ) and (b) of FIG. 6. Filtering is performed by matched filters (6.3) and (6.4) in order to extract an exact synchronization pulse from the signal sample. From the output of matched filters, the signals are fed to quadratic detectors (6.5) and (6.6). Examples of signals at the output of quadratic detectors (6.5) and (6.6) are shown in graphs (c) and (d) of FIG. 6. From the outputs of quadratic detectors (6.5) and (6.6), the signals enter the threshold comparison units (6.7) and (6.8), in which they are compared with the threshold value in order to detect accurate synchronization pulses. If a precise synchronization pulse is not detected in at least one of the blocks (6.7) and (6.8), the processing of the current pair of samples stops. Examples of signals at the outputs of blocks (6.5) and (6.6) are shown in graphs (e) and (ƒ) of FIG. 6. In the same graphs, the dotted lines show the threshold values used to detect accurate synchronization pulses. If synchronization pulses are detected in both signals, these signals are sent to the exact time synchronization block (6.9), where the exact time synchronization is performed according to the temporary position of the maximum signal amplitudes exceeding the threshold and the distance between the points. Exact time synchronization is performed by shifting the sample signal of the mobile receiving point by the number of samples of the discrete signal corresponding to the difference in the reception times of the exact synchronization pulse by Δτ points and taking into account the propagation time of the exact synchronization pulse τ _b between points

where Δ _ƒP is the bandwidth of the location receiver;

N _max1 is the number of the maximum element of the sample signal of the fixed point at the output of the quadratic detector (6.5);

N _max2 - number of the maximum sample element of the signal of the mobile receiving point at the output of the quadratic detector (6.6);

- число отсчетов сигнала, пропорциональное времени распространения импульса точной синхронизации между неподвижным пунктом и подвижным приемным пунктом;

- the number of signal samples proportional to the propagation time of the exact synchronization pulse between the fixed point and the moving receiving point;

- размер измерительной базы;

- the size of the measuring base;

x _RFP , y _RFP , z _RFP - coordinates of the mobile receiving point relative to the fixed point in a rectangular coordinate system;

C is the propagation velocity of the electromagnetic wave.

The number of discrete samples m calculated by the exact time synchronization block (6.9) enters the digital delay line (6.10), where it is used to delay the signal from a sample of a fixed point. The delayed signal from the sample of the fixed point from the output of the digital delay line (6.10) and the signal from the sample file of the mobile receiving point (6.2) go to the sampling blocks (6.11) and (6.12) in which the final samples are formed by extracting them from the original ones. The final samples are formed from the part of the initial samples that do not contain samples of the exact synchronization pulse. Examples of final samples at the output of the sampling blocks (6.11) and (6.12) are shown in graphs (e) and (ƒ) of FIG. 6.

At the third stage, the IRI signals are detected and the points of the difference in the moments of their reception are evaluated.

The final samples from the sampling blocks (6.11) and (6.12) enter the correlator (6.13). In the correlator (6.13), the module of the mutual correlation function (VKF) of the final samples is calculated. VKF is calculated by discrete convolution [5, p. 208] final samples in accordance with the expression

where M = 2I-1 is the volume of VKF;

I is the volume of the final sample;

n = 1 ... M-1 - indexation of the VKF samples;

s ₁ - the final sample of the signal received by the fixed point;

s ₂ - the final sample of the signal received by the mobile receiving point.

In FIG. 7, an example of a VKF having two correlation maxima corresponding to two IRIs is shown. Correlation maxima have delays τ _z1 'and τ _z2 '. The dotted line shows the detection threshold of the IRI.

The values of time delays corresponding to the maximums of the VKF exceeding the threshold are calculated in the threshold comparison block (6.14). Estimation of signal delays is made in accordance with the expression

where u _j - numbers of samples VKF, exceeding the detection threshold of IRI;

j = 1, 2, ... are the numbers of the maximums of the VKF exceeding the IRI detection threshold.

The value of the IRI detection threshold is set by the operator processing the data on a portable personal computer (6).

In the IRI position line calculator (6.15), based on the measured delays, the absolute difference in the distances between points and each of the detected IRIs is calculated by the formula

Based on the measured absolute differences of the distances between the points and each of the detected IRI and the coordinates of the points at the time of receiving the samples, the calculation of the position lines of the IRI is performed.

The coordinates of the points belonging to the Iranian position lines are calculated in the following sequence.

The coordinates x ', y', z 'of the points belonging to the lines of the position of the IRI on the plane rotated by the angles α and β relative to the axes are calculated. y and z, respectively. The y axis is directed north, the z axis is up, the x axis is east.

The coordinates of the points x ', y', z 'are found as the real roots of the quadratic equation

,

Where

,

x 'is the abscissa;

y 'is the ordinate;

z '= bx' + ay '- applicate.

The solution of equation (5) is made for the ordinate y 'given in the range corresponding to the IRI search zone relative to the position of the fixed point, with a fixed step.

The calculation of the rotation angles of the coordinate system

β = arctan ( a ⋅cos α + b⋅sin α).

The spatial coordinate system is rotated with the calculated coordinates of the points x ', y', z 'by the angles α, β and -α relative to the axes y, z and y, respectively.

After the coordinate system is rotated, the implicates of all the points belonging to the IRI position lines become equal to zero. The coordinates of the points belonging to the Iranian position line have two x and y coordinates.

The calculated lines of position of the IRI, in the form of the set of coordinates of the points of the plane, enter the display unit (6.16), where the coordinates of the lines of position of the IRI are converted from rectangular to the geographical coordinate system.

The indication of the IRI position lines is made by the display unit (6.16). In addition to the position lines of the IRI, the display unit (6.16) on the screen of the portable personal computer (6) displays the position of the fixed item.

The second and third stages of the data processing algorithm are repeated for each pair of files selected in the first stage.

The correlation processing and indication system is implemented in the form of specialized portable personal computer software (6).

The option of displaying the lines of position of the IRI in a rectangular coordinate system, in the presence of three IRI operating at the same frequency, is shown in Fig.4. With a sufficient number of lines of position of the IRI, areas of their intense intersection are visible. These areas correspond to the location of Iran. The remaining single intersections of the Iranian position lines are statistically independent (random).

Placing a mobile receiving point on the UAV allows for less time to take measurements on the territory of the IRI search, thereby reducing the time it takes to establish the position of each IRI. Thus, the claimed technical result is achieved.

Literature

1. Patent for invention No. 2619915.

2. Patent for invention No. 2620607.

3. Kupriyanov A.I. Electronic warfare. - M.: "University Book", 2013.

4. Handbook of mathematics for engineers and students of technical colleges. Bronstein I.N., Semendyaev K.A. - M.: “Science”, Main Edition of the Physics and Mathematics Literature, 1981.

5. R. Lyons. Digital signal processing. Per. from English - M .: Binom-Press LLC, 2006.

Claims (1)

Correlation-base system for the location of stationary sources of radio emission (IRI) using an unmanned aerial vehicle (UAV), containing a fixed point and a mobile receiving point, characterized in that the fixed point consists of a transceiver antenna, antenna switch, attenuator, adder, pulse generator precise synchronization, a portable personal computer, a location receiver and a navigation receiver, the receiving and transmitting antenna being connected to the antenna switch, the output connected to the first input of the adder, the output of the adder is connected to the input of the location receiver, the output of the location receiver is connected to a portable personal computer, the output of the navigation receiver is connected to a portable personal computer, the portable personal computer is connected to the control input of the accurate clock pulse generator and the control input of the antenna switch, the output of the accurate synchronization pulse generator is connected to the input of the antenna switch and the input of the attenuator, the output which is connected to the second input of the adder, the mobile receiving station consists of a UAV with a receiving antenna, a location receiver, a microcomputer and a navigation receiver placed on it, the antenna connected to the input of the location receiver, the output of the location receiver connected to the microcomputer, the output of the navigation receiver connected to the microcomputer, moreover, the navigation receiver of the fixed point is designed to determine the coordinates of the fixed point, the navigation receiver of the moving receiving point This is designed to determine the coordinates of the mobile receiving point, while the fixed point implements the functions of generating and emitting accurate synchronization pulses and receiving them, receiving IRI signals, converting the received signals to digital form, followed by their recording on a machine storage medium (MNI), a mobile receiving point implements the functions of receiving accurate synchronization pulses, receiving IRI signals, converting the received signals to digital form with their subsequent recording to a removable MINI, joint processing of signals als, taken fixed point and moving a receiving point is made on the portable PC after the fixed point UAV landing, the information generated on the movable infeed station, is entered in the portable personal computer with a fixed point PIM extracted from the moving receiver points.

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