RU2285934C2 - Method for one-positional detection of position of decametric transmitters - Google Patents

Abstract

FIELD: radio engineering, possible use for determining position of radio radiation sources in decametric range when using one receiving station.

SUBSTANCE: increased precision of position detection is achieved based on additional information, received as a result of division of beams of multi-beam field of received signal and modeling the process of radio-waves expansion in three-dimensional non-homogeneous ionosphere, thus making it possible to correct deviations of beam trajectories of signal by distance and by direction, considering inclinations of reflective layer of ionosphere, and also to remove ambiguousness of one-positional coordinates measuring by comparing trajectories of selected beams.

EFFECT: increased precision of one-positional determining of position of decametric transmitters.

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Description

The invention relates to radio engineering and can be used to determine the location of radio sources in the DKMV range when using one receiving station.

The achievement of theoretically extreme accuracy of positioning in the DKMV range is limited by significant a priori uncertainty regarding the parameters of the propagation medium of spatial radio waves and the imperfection of the applied methods of processing the received signals.

There is a method of one-position location of DKMV transmitters [1], including coherent reception and synchronous registration of signals for all bases formed by the reference and all the antennas included in the array, restoration based on the recorded signals of the two-dimensional complex angular spectrum, the position of the module maximums which reflects azimuthal α and angular β of the bearing of the transmitter, and the determination of the slant range using the formula R = H / sinβ, where H is the known height of the transmitter.

This method loses its operability in the event of the arrival of an ionospheric wave at the receiving point, since it provides the determination of only the slant range to the radiation source.

A known method of single-position location DKMV transmitters [2]. According to this method:

1. Receive the antenna array of the multipath signal of the transmitter at a given frequency.

2. Synchronously transform the ensemble of received signals into digital signals.

3. Synchronously register digital signals at a given time interval.

4. Determine the azimuthal direction α of the arrival of the radio wave according to the azimuthal signal, which has a component that varies according to the sinusoidal law when the phase of the received signal changes.

5. Measure the amplitude m 'of the sinusoidal component.

6. Generate an amplitude m corresponding to the amplitude m 'when the radio wave propagates over the Earth's surface.

7. The angular β bearing of the received radio signal is measured according to the formula cosβ = m '/ m.

8. Determine the range to the transmitter according to the formula

where h is the height of the ionosphere, r is the radius of the Earth.

The disadvantages of the prototype method include the low accuracy of location, due to:

- the presence of anomalous errors in the measurements of azimuthal (up to 3 degrees) and elevation (up to 30 and more degrees) bearings, due to interference beats of the signals of several rays arising from reflection from the ionosphere, on the one hand, and the lack of spatial resolution of the prototype, on the other ;

- the presence of anomalous errors in the measurements of the azimuthal bearing (up to 5 degrees) and range (up to 20%) associated with the presence of slopes of the reflecting surface (horizontal gradients of the electron concentration of the ionosphere), leading to deviations of the beam path, both in range and direction, s on the one hand, and the lack of a prototype of operations for correcting anomalous deviations, on the other;

- the presence of anomalous errors of one-position range measurement (more than 100%) associated with the ambiguity of measurements due to the multi-hop mechanism of propagation of spatial radio waves due to reflection from the ionosphere, on the one hand, and the prototype's lack of ambiguity removal operations, on the other.

Improving the accuracy of single-position location of radio sources in the DKMV range when using the prototype method can be achieved in several well-known ways [3].

1. Histogram processing or averaging of measurement results to suppress multipath and highlight the dominant beam.

2. Correlation of time-related measurement results, which allows filtering out anomalous errors caused by temporary non-stationarity of the signal and noise emissions.

3. Attraction of additional a priori information about the location of the monitored transmitters, for example, about the impossibility of placing the transmitter on the water surface of the Earth, to eliminate the ambiguity of measurements.

The first way does not radically solve the problem, since it preserves the dependence of achievable accuracy on the number and parameters of the rays of the incident field and requires a very long observation time.

The second way is very effective in the single-beam case, but in the presence of a multi-beam signal can lead to gross measurement errors.

The third way can lead to success only in individual exceptional cases and, as a result, is not very effective in practice.

The technical result of the invention is to improve the accuracy of single-position location DKMV transmitters.

Improving the accuracy of positioning is achieved on the basis of additional information obtained by separating the rays of the multipath field of the received signal and modeling the process of propagation of radio waves in a three-dimensionally inhomogeneous ionosphere, which opened up the possibility of correcting deviations of the ray paths of the signal in range and direction by taking into account the slopes of the reflecting layer of the ionosphere, and also eliminate the ambiguity of on-position coordinate measurement by comparing the trajectories of the selected whose.

The technical result is achieved by the fact that in the method of on-off location of the DKMV transmitters, which includes receiving at a given frequency a multipath signal from a transmitter by an array of antennas, synchronously converting an ensemble of signals received by antennas into digital signals and synchronously registering them at a given time interval, according to the invention, signals are extracted from digital signals separate rays of the transmitter signal arrival and restore two-dimensional bearings of each beam according to known algorithms, form a model of the ionosphere corresponding to the frequency and time interval of signal reception, and model signals of the return radiation in the measured directions of arrival of the rays, determine the paths of the reverse multi-hop propagation of model signals and find the coordinates of the points of their arrival on the Earth's surface, which are identified as the coordinates of the alleged points of radiation of the transmitter signal, find coincidence of received points, coincident points combine and find a point whose coordinates are identified as the coordinates transmitted chica.

The operation of the method is illustrated by the following drawings.

Figure 1. - structural diagram of a device for determining the location of DKMV transmitters.

Figure 2. - The operation scheme of the system of single-position location.

The method of on-off location of DKMV transmitters is as follows.

многолучевый сигнал передатчика решеткой антенн. В результате формируется ансамбль сигналов х_n(t), зависящих от времени t, где n=0,...,N - номер антенны.1. Accepted at a given frequency

multipath transmitter signal by antenna array. As a result, an ensemble of signals x _n (t) is formed, depending on time t, where n = 0, ..., N is the antenna number.

2. Synchronously transform the ensemble of signals x _n (t) received by the antennas into digital signals x _n (z), where z is the number of the time reference of the signal.

3. Synchronously register digital signals x _n (z) at a given time interval.

4. From the digital signals x _n (z), the signals of the individual rays of the arrival of the transmitter signal are extracted and the two-dimensional bearings of each beam (azimuth α _q and elevation angle β _q , where q = 1 ... Q is the current beam number) are restored according to well-known algorithms.

где F_t{...} - оператор дискретного Фурье-преобразования по времени, l - номер частотной дискреты, 1≤l≤L, сигналов x_n(z) и формируют амплитудно-фазовое распределение в виде вектораThe selection of signals of individual rays of the signal arrival at the receiving point and the restoration of two-dimensional bearings of each beam is possible using various algorithms [4]. For example, it is possible to use an algorithm that separates beams by Doppler frequency offset. In addition to this algorithm, which requires long samples of the signal, algorithms based on reconstructing the spatial radio image of the source [1] can be used, including high-resolution algorithms that provide separation of correlated signals (signal-rays arising from the reflection of a DKMV transmitter signal from the ionosphere) [4 ]. At the same time, spectral densities are restored

where F _t {...} is the discrete Fourier transform operator in time, l is the number of the frequency discrete, 1≤l≤L, signals x _n (z) and form the amplitude-phase distribution in the form of a vector

- спектральная плотность сигнала, измеряемого на опорной антенне решетки с номером n=0, а ()^* - означает комплексное сопряжение. Сформированный вектор входных данных

используется для итерационной регуляризованной реконструкции угловой зависимости падающего поля в виде комплексного вектора

где А - заданная матрица размером N×М, характеризующая возможные направления прихода сигнала от каждого потенциального источника, М - число угловых положений, соответствующих заданным потенциально возможным направлениям прихода сигналов, γ - параметр регуляризации,

p=0,1,

элемент вектора

ε - малое число.Where

- the spectral density of the signal measured at the reference antenna of the array with number n = 0, and () ^* - means complex conjugation. Formed input vector

used for iterative regularized reconstruction of the angular dependence of the incident field in the form of a complex vector

where A is a given matrix of size N × M characterizing the possible directions of arrival of the signal from each potential source, M is the number of angular positions corresponding to the given potential directions of arrival of signals, γ is the regularization parameter,

p = 0.1

vector element

ε is a small number.

определяют ансамбль двумерных пеленгов

The highs of the reconstructed high-resolution spatial spectrum

define an ensemble of two-dimensional bearings

и временному интервалу приема (время, месяц, год) сигнала передатчика и модельные сигналы обратного излучения в измеренных направлениях

прихода лучей.5. Form the ionosphere model corresponding to the frequency

and the time interval of reception (time, month, year) of the transmitter signal and model feedback signals in the measured directions

the arrival of the rays.

принимаемого сигнала, которое необходимо для вычисления показателя преломления изотропной плазмы μ=μ(φ, θ, r):In forming the ionosphere model, the International Reference Model of the Ionosphere IRI-2001 is used [5]. As a result, the spatial distribution of the squared ratio of the plasma electron frequency ƒ _p = ƒ _p (φ, θ, r) in the ionosphere to the working frequency is calculated and stored

the received signal, which is necessary for calculating the refractive index of an isotropic plasma μ = μ (φ, θ, r):

To speed up the calculation procedure, the plasma electron frequency ƒ _p in the ionosphere is predicted on a three-dimensional spatial grid and is approximated by a cubic spline function. The spatial grid pitch in coordinates on the earth's surface does not exceed 500 km, and in the vertical coordinate is 2.5 km. After the approximation procedure, the coefficients of the approximating spline function are stored in the nodes of the spatial grid.

и рабочей частотой

Компоненты единичного вектора

определяются по измеренному азимутальному α и угломестному β пеленгам луча (здесь и далее для упрощения записи индекс номера луча опущен) и в локальной системе координат (начало координат совпадает с точкой расположения пеленгатора (φ₀, θ₀, r₀), ось у направлена на север, ось х - на восток, ось z - вертикально вверх), имеют вид

Переход от локальной системы координат к глобальной декартовой правой системе координат (начало координат связано с центром Земли, ось z проходит через географический север, ось х - через нулевой меридиан) для компонент вектора

осуществляется с помощью матрицы преобразования А:The model signal is described by a single wave vector

and operating frequency

Unit Vector Components

are determined by the measured azimuthal α and elevation β bearings of the beam (hereinafter, to simplify writing, the beam number index is omitted) and in the local coordinate system (the origin coincides with the position of the direction finder (φ ₀ , θ ₀ , r ₀ ), the y axis is directed to north, x-axis - east, z-axis - vertically up), have the form

Transition from the local coordinate system to the global Cartesian right coordinate system (the origin is connected to the center of the Earth, the z axis passes through geographic north, the x axis passes through the zero meridian) for the components of the vector

is carried out using the transformation matrix A:

where the coordinates of the direction finder φ ₀ , θ _{0 are} substituted as spherical coordinates φ and θ.

6. Form the trajectories of the reverse multi-hop propagation of model signals of each beam in the ionosphere. To do this, find the initial values of the spherical coordinates φ, θ, r of the beam, which are assumed to be equal to the coordinates of the point of entry of the beam into the ionosphere φ ₁ , θ ₁ r ₁ , calculated by the formulas:

декартовых координат точки входа луча в ионосферу:

r₀ - радиус Земли, h₀ - начальная высота ионосферы,

- декартовые координаты точки излучения модельного сигнала с поверхности Земли в глобальной декартовой правой системе координат (начало координат связано с центром Земли, ось z проходит через географический север, ось х - через нулевой меридиан). Для первого скачка (i=1) вектор

вычисляется по координатам пеленгатора:where x _1x , x _1y , x _1z are elements of the vector

Cartesian coordinates of the entry point of the beam into the ionosphere:

r ₀ is the radius of the Earth, h ₀ is the initial height of the ionosphere,

- Cartesian coordinates of the point of emission of a model signal from the Earth’s surface in the global Cartesian right-handed coordinate system (the origin is connected to the center of the Earth, the z axis passes through geographic north, the x axis passes through the zero meridian). For the first jump (i = 1), the vector

calculated by the coordinates of the direction finder:

модельного сигнала на входе в ионосферу определяется по вектору

с использованием унитарной матрицы преобразования В глобальной системы координат к сферической:The initial value of the wave vector

the model signal at the entrance to the ionosphere is determined by the vector

using the unitary transformation matrix B of the global coordinate system to spherical:

where the values of φ ₁ , θ _{1 are} substituted as spherical coordinates φ and θ.

To construct the ray path of the model signal, the Cauchy problem for the system of differential equations is numerically solved:

модельного сигнала в ионосфере, φ, θ, r - координаты луча.where k _φ , k _θ , k _r are the values of the elements of the wave vector

model signal in the ionosphere, φ, θ, r - beam coordinates.

, сферические φ₂, θ₂, r₂ и глобальные декартовые координаты точки выхода из

луча модельного сигнала. В качестве значений сферических координат φ₂, θ₂, r₂ и волнового вектора

выбирается решение задачи Коши, полученное на предыдущем этапе, в точке выхода лучевой траектории из ионосферы.Find the wave normal vector at the exit from the ionosphere

, spherical φ ₂ , θ ₂ , r ₂ and global Cartesian coordinates of the exit point from

beam model signal. As the values of the spherical coordinates φ ₂ , θ ₂ , r ₂ and the wave vector

the solution to the Cauchy problem obtained at the previous stage is chosen at the exit point of the ray path from the ionosphere.

7. Find the spherical coordinates of the arrival of the beam of the model signal to the Earth's surface (for the first jump i = 1):

декартовых координат точки прихода волны на поверхность Земли в глобальной системе координат:where x _3x , x _3y , x _3z are elements of the vector

Cartesian coordinates of the point of arrival of the wave on the Earth’s surface in the global coordinate system:

Matrix B is calculated at a point with coordinates φ ₂ , θ ₂ .

и

:

, где матрица А и компоненты вектора

после отражения от поверхности Земли определяются с использованием координат

и

полученных на предыдущем скачке.The spherical coordinates of the point of arrival of subsequent jumps in the radial trajectory are determined by repeating steps 5-7 using updated vectors

and

:

where the matrix A and the components of the vector

after reflection from the surface of the earth are determined using the coordinates

and

received at the previous jump.

The found coordinates of the arrival of model signals of all the jumps of each beam are identified as the coordinates of the assumed points of radiation of the transmitter signal.

и двухскачковой

траекторий.Figure 2, as an example, shows the single-hop and double-hop propagation paths of model signals indicating the coordinates (φ ₀ , θ ₀ ) of the receiving station (PS) location point and the coordinates of the points of arrival on the Earth's surface with a single-hop

and two-jump

trajectories.

8. Find the coincidence of the alleged points of radiation.

полученных точек излучения сигнала, соответствующие различным лучам прихода принятого сигнала, и отбирают точки с совпадающими координатами.To do this, compare the coordinates

received signal emission points corresponding to different arrival beams of the received signal, and points with matching coordinates are selected.

соответствующие лучу с односкачковой траекторией, и координаты

соответствующие лучу с двухскачковой траекторией.In the example shown in figure 2, the coordinates are compared

corresponding to a beam with a single-jump path, and coordinates

corresponding to a beam with a two-hop trajectory.

9. Matched points combine and find a point whose coordinates are identified as the coordinates of the transmitter.

Comparison and integration are possible in various ways [3, p. 297, 298]. For example, figure 2 illustrates the possibility of selecting points according to the degree of overlap of the error ellipses or by the belonging of the points of the overlapping region of their error ellipses. Perhaps the application of the principle of the center of mass. For example, for a pair of points identified as putative radiation points, a point is found according to the principle of the center of mass. If the distance from the center of mass to each point is less than a predetermined threshold, then a decision is made on their coincidence and the choice of the center of mass as the location of the transmitter. The threshold value is selected based on the operational accuracy of the coordinate measurement. As a result, several points to be compared (in the example of figure 2, three points are compared) are replaced by one point of the center of mass.

Figure 2 shows the point with the coordinates [φ _RPD , θ _RPD ), which are identified as the coordinates of the transmitter (RPD). In this case, the aforementioned principle of the center of mass was used.

The device in which the proposed method is implemented (Fig. 1) comprises a series-connected antenna system 1, a multi-channel radio receiving device (RPU) 2, a multi-channel analog-to-digital converter (ADC) 3, a computer 4, a block for modeling trajectories and estimating coordinates 5, a block coordinate comparison 6, the control and display unit 7 and the ionosphere model shaper 8. The output of the shaper 8 is connected to the second input of block 5, and the output of block 7 is connected to the second inputs of device 2 and converter 3.

The antenna system 1 contains a reference antenna with the number n = 0 and N antennas with the numbers n = 1 ... N, combined in a grid.

Multichannel RPU 2 is made with a common local oscillator and with a bandwidth of each channel corresponding to the width of the spectrum of the transmitter signal. The common local oscillator provides multi-channel coherent signal reception, which is the main condition for interferometric (holographic) registration of complex transmitter signals.

In addition, RPU 2 provides the connection of a reference antenna (n = 0) instead of all the antennas of the array for periodic calibration of channels using an external signal source in order to eliminate their amplitude-phase non-identity. Calibration by internal signal source is possible. In this case, a noise generator can be used, the output of which can also be connected instead of all antennas for periodic calibration of channels.

Note that it is possible to build a multi-channel RPU 2 according to the principle of a direct gain receiver. The channels of the RPU 2 perform the function of filtering the received signal by frequency and the function of amplifying the filtered signal to a level consistent with the input range of ADC levels.

The shaper of the ionosphere model 8 provides both a long-term forecast of the ionosphere parameters and its correction according to the data received from external systems of vertical or inclined sounding of the ionosphere.

The control and indication unit 7 sets the initial parameters (frequency and reception interval) and synchronizes the operation of the devices in calibration mode and in the main mode.

The device operates as follows.

и обеспечивается запуск АЦП 3 и формирователя 8.On the control signal from block 7, the RPU 2 is tuned to the reception frequency

and provides the launch of the ADC 3 and the shaper 8.

в полосе приема, соответствующей ширине спектра частот принимаемого сигнала. В результате формируется ансамбль сигналов x_n(t), зависящих от времени t, где n=0,...,N - номер антенны.The multipath transmitter signal is received by an array of N + 1 antennas and an (N + 1) -channel RPU 2 at a given frequency

in the reception band corresponding to the width of the frequency spectrum of the received signal. As a result, an ensemble of signals x _n (t) is formed, depending on time t, where n = 0, ..., N is the antenna number.

The received signals x _n (t) are synchronously converted by the (N + 1) -channel ADC 3 into digital signals x _n (z), where z is the number of the time reference of the signal.

In the calculator 4, digital signals x _n (z) are recorded at a given time interval. From digital signals x _n (z), the signals of individual rays of the arrival of the transmitter signal are extracted and the two-dimensional bearings of each beam are restored (azimuth α _q and elevation angle β _q , where q = 1 ... Q is the current beam number) according to known algorithms. At the output of calculator 4, an ensemble of two-dimensional bearings is formed

прихода лучей. С использованием модели ионосферы, получаемой в формирователе 8 с привязкой к частоте

и времени приема (время, месяц, год), строятся траектории обратного многоскачкового распространения модельных сигналов каждого луча в ионосфере. Кроме того, в блоке 5 определяются сферические координаты прихода модельных сигналов всех скачков каждого луча на поверхность Земли, которые идентифицируются как координаты предполагаемых точек излучения сигнала передатчика.In block 5, model feedback signals are generated in the measured directions

the arrival of the rays. Using a model of the ionosphere obtained in the shaper 8 with reference to the frequency

and reception time (time, month, year), the trajectories of the reverse multi-hop propagation of model signals of each beam in the ionosphere are built. In addition, in block 5, the spherical coordinates of the arrival of model signals of all the jumps of each ray to the Earth's surface are determined, which are identified as the coordinates of the assumed emission points of the transmitter signal.

In block 6, the coordinates of the received signal emission points corresponding to different arrival beams of the received signal are compared, and points with matching coordinates are selected. Matched points are combined and a point is found whose coordinates are identified as the coordinates of the transmitter. Comparison and combination are carried out in accordance with paragraph 9 on page 10 of the description.

In block 7, to increase the information content, the location of the transmitter on the cartographic background is displayed.

Improving the accuracy of single-position location of the DKMV transmitters is achieved by additional information obtained by dividing the multipath field of the received signal and simulating the process of propagation of radio waves in a three-dimensionally inhomogeneous ionosphere.

This provides:

- reducing the likelihood of anomalous errors in location measurements due to interference beats of the signals of several beams;

- elimination of anomalous positioning errors caused by the deviation of the beam path, both in range and direction due to the slopes of the reflecting layer of the ionosphere;

- solving the problem of unambiguous determination of the location of DKMV transmitters when using only one receiving station (direction finder-range finder).

INFORMATION SOURCES

1. patent RU No. 2158002, class. 7 G 01 S 3/14, 5/04, 2000

2. JP patent No. 4-29030, class. G 01 S 3/48, 11/02, 1993

3. Shirman Y.D., Manzhos V.N. The theory and technique of processing radar information against the background of interference. - M .: Radio and communications, 1981. - 416 p.

4. Shevchenko V.N. Estimation of the angular position of sources of coherent signals based on regularization methods // Radio Engineering. - 2003. - No. 9. - C.3-10.

5. Bilitza D. Ionospheric Models for Radio Propagation Studies // The review of radio science 1999-2002 / Ed. W. Ross Stone, IEEE Press. 2002. PP.625-679.

Claims (1)

Method for single-position location of decameter transmitters, including receiving at a given frequency a multipath transmitter signal by an array of antennas, synchronously converting an ensemble of signals received by antennas into digital signals and registering them synchronously at a predetermined time interval, characterized in that the signals of the individual beams of the transmitter signal arrive from digital signals and determine the two-dimensional bearings of the arrival of each ray, form a model of the ionosphere corresponding to the frequency and time the signal reception interval, and the model signals of the return radiation in the measured directions of arrival of the rays in the ionosphere, determine the trajectories of the reverse multi-hop propagation of model signals in the ionosphere and find the coordinates of the points of their arrival on the Earth's surface, which are identified as the coordinates of the assumed points of radiation of the transmitter signal, find the coincidence of the received points , coincident points combine and find a point whose coordinates are identified as the coordinates of the transmitter.

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