RU2798776C1 - Method for locating sources of decameter radio emission - Google Patents

Abstract

FIELD: radio direction finding.

SUBSTANCE: invention can be implemented in radio monitoring and radar systems for locating a source of decameter radio emission in frequency, azimuth and elevation of an incoming ionospheric radio wave using data from oblique-backward sounding (OBS) of the ionosphere. The claimed method consists in determining the range to a radio emission source (RES) along the leading edge of the OBS diagnostic signal by correcting the elevation angles of the incoming radio wave calculated from the median ionospheric model for various distances from the reception point in the search sector. To do this, the method includes receiving and measuring the azimuth and elevation angle of the ionospheric radio wave from RES, ionospheric OBS in the direction of the radio wave arrival azimuth, highlighting the leading edge of the OBS signal on the ionogram, determining the maximum applicable frequencies (MAF) of oblique sounding on the range grid along the leading edge of the OBS signal, correcting the predicted angular frequency characteristics of slant propagation on the MAF range grid and determining the range to RES in frequency and elevation and calculating the location coordinates.

EFFECT: improved accuracy of the location of sources of decameter radio emission by the goniometer-range method.

1 cl, 4 dwg, 1 tbl

Description

The invention relates to radio direction finding and can be implemented in radio monitoring and radar systems for locating a source of radio emission (RES) in frequency, azimuth and elevation of an incoming ionospheric radio wave.

The traditional method for determining the coordinates of radio emission sources (RES) is the triangulation method, which assumes the presence of a network of direction-finding points united by a single control system (Patent RU No. 2490661 C1, IPC G01S 1/08 - 20.08.2013, Bull. No. 23). It is based on the simultaneous use of several KB direction finders. For high accuracy of positioning of RRS, a separation between direction finding points of several hundred kilometers is required with the obligatory presence of a communication system between them. The disadvantages of the method include the difference in the conditions for the passage of radio waves on the paths for determining the bearing, up to the absence of radio signal reception, which can lead to errors in determining the coordinates of the RES.

The method of single-point positioning of RES (Patent RU No. 2523650 C2, IPC G01S 5/00 - 20.07.2014, Bull. No. 20) consists in modeling the propagation modes of signals from the range grid, determining the angles of arrival of the phase incursion modes in antenna elements (AE) circular antenna array (AR). Further, these phase incursions are subtracted from the signal from the AE, quadratically detected and averaged over the number of AE AA. The bearing and range to RES is determined by the minimum of averaging results, weighted in proportion to the number of beams. It is proposed to use the VZ station, which determines the heights and critical frequencies of the ionospheric layers or monthly forecasts. The disadvantage of this method is the limited possibility of application - only for single-hop paths with elevation angles of more than 10 degrees, the impossibility of correctly assessing the received signal, that it meets certain conditions and, as a result, the low probability of correct location of the RES.

Closest to the proposed technical solution is a method of locating sources of radio emission (Patent RU No. 94017080 A1, IPC G01S 3/02 - 05/27/1996), in which, in order to improve the accuracy of determining the coordinates of RES, the slant range to RES is additionally measured. To determine the slant range, back-oblique sounding (BIS) of the ionosphere is used at a frequency close to the frequency of the SRI. The delay time of the BIS back reflection pulse from the earth's surface is measured in the region of the location of the RES, received on the differential radiation pattern (DN) of the wide-base antenna-feeder system. The RP is preliminarily set according to the azimuth and elevation angle of the RES radio wave.

This invention is taken as a prototype. The pulse delay is measured along the leading edge on the time base of the BIS signal. The term "slant range" in the prototype is equivalent to the minimum group propagation path R _m signal scattered near the border of the illuminated zone D _m for a given frequency. The range to IRI - D _m is determined by the formula D _m =P _m cosΔ, where Δ is the elevation angle of the incoming radio wave (Fig. 1).

The main disadvantage of the prototype is that in addition to the signals scattered from areas of the earth's surface located near the border of the illuminated zone, the signals reflected from selected objects on the earth's surface and scattering formations in the ionosphere are recorded. This leads to errors in RES location. Another disadvantage is the use of an approximate connection of the minimum group path with the range, which is not applicable for large distances to the RES.

The purpose of the claimed invention is to improve the accuracy of locating sources of decameter radio emission by the goniometer-ranging method due to the fact that the range to the source of radio emission is determined by the leading edge of the diagnostic signal of the reciprocating sloping sounding by adjusting the elevation angles of the incoming radio wave for different distances from the reception point in the search sector.

The essence of the method lies in the fact that the coordinates of the IRI are calculated by measuring the angle of arrival of the radio wave in the azimuth plane (bearing) (ϕ _IRI ) from the IRI, the angle of arrival of the wave in the vertical plane (elevation angle Δ _IRI ), and determining the range to the IRI (D _IRI ) according to oblique-reciprocating sounding of the ionosphere. The range D of _{the IRI} is determined from the range-angular characteristic (DUH) D(Δ), obtained by correcting the predicted elevation angles of the incoming radio wave, calculated from the median ionospheric model for various distances from the receiving point, along the leading edge of the BIS diagnostic signal in the search sector without parameter adaptation ionosphere.

Determining the range to the RES according to the BHZ data includes:

1. Identification of the leading edge of the BIS signal on the ionogram.

2. Determination of the maximum usable frequency (MUF) of the propagation mode on the range grid in the sounding sector.

3. Correction of the angular frequency characteristics (FCR) of oblique propagation on the MUF range grid.

4. Construction of the range-angular characteristic D(Δ) for the radio emission frequency of the source, using the corrected frequency response on the range grid.

5. Determining the distance D _IRI to IRI by elevation angle Δ _IRI and determining the coordinates of IRI by bearing ϕ _IRI and D _IRI .

The essence of the method is illustrated by drawings, which show:

Fig. 1 - Equivalent trajectory of radio wave propagation;

(сплошная линия), дальности до границы освещенной зоны

(штриховая линия) и реальный передний фронт сигнала ВНЗ

(линия с точками);Fig. 2 - Frequency dependences of the minimum group path

(solid line), distances to the border of the illuminated zone

(dashed line) and the real leading edge of the BIS signal

(line with dots);

Fig. 3 - Frequency dependences of the angle of arrival of the radio wave on the range grid;

Fig. 4 - Range-angular characteristic D(Δ) for different frequencies.

где

- МПЧ для максимальной дальности распространения сигнала ВНЗ. Также адиабатическим инвариантом на относительной сетке частот v является отношение Р_m/D_m.Reverse-oblique sounding is carried out in the direction of the azimuth of the arrival of the radio wave from the IRI. As a result of sounding, an ionogram is recorded - a matrix of amplitudes of signals scattered by the earth's surface with coordinates: frequency - group path. The maximum in the amplitude sweep of the BIS signal at frequency f is formed by the signals scattered at the border of the illuminated zone D _m in the focus region where the upper and lower beams of the incident field merge. The maximum delay is close to the minimum propagation delay of the scattered signal, or the minimum group path P _m. The minimum group path Р _m (f) changes slightly with changing ionospheric parameters and is an adiabatic invariant on the relative frequency grid

Where

- MUF for the maximum propagation range of the BHZ signal. Also, the adiabatic invariant on the relative frequency grid v is the ratio Р _m /D _m .

(f) и результатов вторичной обработки данных зондирования - массив моментов прихода рассеянного сигнала со значимой амплитудой

1. The selection of the leading edge of the BIS signal on the ionogram is carried out on the basis of the adiabatic dependence of the minimum group path on the relative frequency grid v using the model frequency dependence

(f) and the results of secondary processing of sounding data - an array of times of arrival of the scattered signal with a significant amplitude

проводят методом «кривых передачи» (Дэвис К. Радиоволны в ионосфере. М.: Мир, 1973. стр. 342-345). Соотношение между частотой f волны, падающей наклонно на ионосферный слой, и частотой эквивалентной вертикальной волны f_v, связаны по закону секанса:Modeling the Minimum Group Path

carried out by the method of "transmission curves" (Davis K. Radio waves in the ionosphere. M.: Mir, 1973. pp. 342-345). The ratio between the frequency f of the wave incident obliquely on the ionospheric layer and the frequency of the equivalent vertical wave f _v are related according to the law of secant:

Unlike a planar waveguide (k=1), the correction factor k due to the sphericity of the Earth depends on the path length. The reference values of the k(D) function for average ionospheric conditions are given in Table 1. 1. The frequency dependence of the effective height of the equivalent wave h'(f _v ) is called VChH.

Based on the geometry of the radio path (Fig. 1), the propagation range of the radio wave emerging at an angle Δ is determined by the expression:

Where

R is the radius of the earth.

The angle of incidence ϕ of the wave is written as:

For a given height-frequency characteristic h'(f _v ) and frequency f defined by expression (1), equation (2) for a fixed range D has two solutions with respect to the exit angle Δ, corresponding to different values of h'(f _v ) - lower and upper rays. The solutions of equation (2) on the range grid determine the range-angular characteristic D(Δ). The minimum in the dependence D(Δ) corresponds to the distance to the border of the illuminated zone D _m . The frequency f for this range, where the upper and lower beams meet, is called the maximum usable radio frequency f _m . The group path of wave propagation by the values h' and Δ is calculated by the formula:

Угловую частотную характеристику Δ^mod(f) для фиксированной дальности D рассчитывают по h'(f_v), используя закон секанса (1), на основе выражений:Based on the calculation of the group path of the lower and upper beams on the range grid, the distance-angular characteristic P(Δ) is determined for a fixed sounding frequency. The minimum in dependence P(Δ) corresponds to the minimum group propagation path P _m . Based on the results of calculating P _m and D _m on the grid of operating frequencies according to the VChH obtained from the median model of the ionosphere, the frequency dependences are determined

The angular frequency response Δ ^mod (f) for a fixed range D is calculated from h'(f _v ) using the law of secant (1), based on the expressions:

пересчитывают на относительную сетку частот

и строят модельную маску относительно

в виде полосы шириной ΔР. Значение ΔР подбирается, исходя из разрешения ионозонда по дальности, порядка 40÷60 км. Для экспериментального набора значений группового пути

определяют возможную область нахождения реальной частоты

соответствующей максимальной дальности скачка. Нижней границей этой области является значение критической частоты слоя в точке излучения. Верхней - частота заведомо больше реальной

(например, предельная частота зондирования). В цикле по частоте, значения (f, P)_k переводят на относительную сетку частот

где

пробегает весь указанный диапазон с некоторым шагом, и подсчитывают число экспериментальных точек, попадающих в модельную маску. По максимуму гистограммы распределения числа экспериментальных точек, попадающих в модельную маску определяют реальную частоту масштабирования

Умножением v на вычисленное значение

прогнозные значения Р_m(v) переносят на частотную шкалу f. В результате, получают масштабированную прогнозную

которую принимают за границу переднего фронта сигнала ВНЗ на ионограмме -

To highlight the leading edge on the ionogram, the characteristic

recalculated to the relative frequency grid

and build a model mask with respect to

in the form of a strip with a width of ΔР. The value of ΔР is selected based on the range resolution of the ionosonde, on the order of 40÷60 km. For an experimental set of group path values

determine the possible location of the real frequency

corresponding to the maximum jump distance. The lower boundary of this region is the value of the critical frequency of the layer at the radiation point. Upper - the frequency is obviously higher than the real one

(for example, the limiting frequency of sounding). In a frequency loop, the (f, P) _k values translate into a relative frequency grid

Where

runs through the entire specified range with a certain step, and count the number of experimental points that fall into the model mask. Based on the maximum histogram of the distribution of the number of experimental points falling into the model mask, the real scaling frequency is determined

Multiplying v by the calculated value

the predicted values of P _m (v) are transferred to the frequency scale f. As a result, a scaled predictive value is obtained.

which is taken beyond the boundary of the leading edge of the BIS signal on the ionogram -

определяют прогнозную МПЧ мода распространения

и вычисляют отношение

(Фиг. 2). Далее, на переднем фронте

определяется частота

для которой групповой путь равен значению

2. Determination of the MUF propagation mode on the range grid in the sounding sector is carried out as follows. For a given range D ₀ using the dependence

determine the predictive MUF propagation mode

and calculate the ratio

(Fig. 2). Next, on the front line

frequency is determined

for which the group path is equal to the value

Реальную УЧХ восстанавливают из прогнозных характеристик Δ^mod(β) умножением β на

Таким образом, УЧХ для радиотрассы заданной длины D₀ есть масштабированная прогнозная УЧХ с коэффициентом

3. The correction of the angular frequency characteristics (UHF) of the oblique propagation on the range grid according to the MUF is carried out as follows. According to the predictive VChH, the dependence Δ ^mod (β) is calculated for the range D ₀ on the relative frequency grid

The real FRF is recovered from the predictive characteristics Δ ^mod (β) by multiplying β by

Thus, the FRF for a radio path of a given length D ₀ is a scaled predictive FRF with a coefficient

4. The construction of the range - angular characteristics D(A) for the frequency of the radio emission of the source is carried out according to the corrected FFC of the signals of oblique propagation on the range grid (Fig. 3 and Fig. 4).

5. Determination of the range D _IRI to IRI in elevation Δ _IRI is carried out according to the corrected range - angular characteristic D (Δ) for the frequency of the radio emission of the source. IRI location coordinates are calculated by bearing ϕ _IRI and D _IRI .

The advantages of the proposed method of RES location in comparison with known methods are:

- improving the accuracy of determining the range to RES using the BIS data in the positioning sector;

- lack of adaptation of the ionospheric parameters to correct the predicted range-angular characteristics of the incoming radio wave;

- the possibility of using simplified, technically feasible algorithms for calculating the propagation characteristics of decameter radio waves.

Claims (1)

A method for locating sources of radio emission by the goniometric-ranging method in the decameter range of radio waves, including measuring the slant range to the source of radio emission using reciprocating sounding (BIS) of the ionosphere, characterized in that the range to the source of radio emission is determined by the leading edge of the diagnostic signal of reciprocating sounding, the selection of which on the ionogram is carried out on the basis of the adiabatic dependence of the minimum group path P _m on the relative frequency grid ν using the model frequency dependence of the minimum group path

and the results of secondary processing of sounding data - an array of moments of arrival of a scattered signal with a significant amplitude

, resulting in a scaled predictive frequency dependence of the minimum group path

which is taken beyond the boundary of the leading edge of the BIS signal on the ionogram

then, for a given range of the radio path D ₀ , the maximum applicable frequency of the propagation mode on the range grid in the sounding sector is determined using the dependence

, determining the predicted maximum usable propagation mode frequency

and calculating the ratio

, using which at the leading edge of the BIS signal on the ionogram

determine the frequency

for which the group path is equal to the value

, which is taken as the maximum applicable frequency of the propagation mode, after which the angular frequency characteristics (FCR) Δ ^mod (f) of the slant propagation on the range grid are corrected according to the found maximum applicable frequency

calculating from the predictive height-frequency characteristic the dependence Δ ^mod (β) for the distance D ₀ on the relative frequency grid

at the same time, the real FRF is restored from the predictive characteristics Δ ^mod (β) by multiplying β by

then, the distance-angular characteristic D(Δ) is plotted for the frequency of the radio emission of the source, using the obtained corrected FFC of oblique propagation signals on the range grid, the distance D _of the radio emission source to the sources of radio emission is determined by the elevation angle Δ _RES is carried out according to the corrected range-angular characteristic D(Δ) for the frequency of the radio emission of the source, and the coordinates of the location of the sources of radio emission are calculated by the bearing ϕ _{of the IRI} from the IRI, the elevation angle Δ _IRI and a certain range to the IRI D _IRI .

Images