RU2580933C1 - Method of determining range to radio source - Google Patents

Abstract

FIELD: radio engineering and communications.

SUBSTANCE: invention relates to radio engineering and can be used in radio monitoring systems when solving the problem of determining coordinates of objects concealed-carriers of radio-frequency sources.

EFFECT: technical result is possibility of determining distance to radiation source, mainly stations VHF range of operating outside the horizon, antenna which can be omnidirectional or highly-directional, scanning or fixed.

1 cl, 2 dwg, 1 tbl

Description

The invention relates to radio engineering, namely to passive radar, and can be used in radio monitoring systems when solving the problem of covertly determining the coordinates of objects-carriers of radio emission sources (IRI), mainly VHF stations operating outside the range of the radio horizon.

A known method of passive determination of the distance to the IRI - emitting surveillance radar station (radar) using a direction finder with an additional receiving point [1]. The determination of the range is achieved by measuring the time interval of passage of the beam of the scanning radar antenna along the measuring base formed by the direction finder antenna and the antenna of the additional receiving point. The method is applicable for determining the range to a radar with scanning narrowly oriented antennas, which is its limitation and, to a certain extent, a disadvantage.

Also known is a method [2], which allows one to determine the distance to the IRI with a directional antenna, both scanning and stationary, oriented with its main lobe to the direction finder antenna. The measuring base of the three receiving points carries out the acquisition of the signal amplitude amplitudes proportional to the field strength, according to which the main lobe of the IRI antenna beam is restored in a linear measure. The distance to the IRI is determined by the ratio of the calculated width of the antenna beam of the IRI in linear units to the value of the antenna beam width extracted from the database in an angular radian measure.

Both methods have a common drawback: it is not possible to measure the distance to radiation sources with omnidirectional antennas, which, as is known, have the majority of connected radio stations.

The closest in technical essence to the proposed method should be recognized as the well-known triangulation method, adopted as a prototype. The method is based on measuring directions to the IRI at two receiving centers spaced at a known measuring base, and calculating the distance to the IRI from a known base and measured directions [3, p. 496].

The disadvantages of the prototype method:

- a large and complex hardware, requiring at least two high-precision direction finders;

- a large measuring base, often commensurate with the range to the object due to the limited accuracy of direction finding, determined by the aperture size of the antenna system of the direction finder (especially in the lower part of the VHF range), which limits the applicability of the method on a single moving object-carrier of direction finders;

- the need to have communication channels (radio communications) for transmission to the data processing point of the measurement results of directions.

The aim of the invention is:

- simplification of the hardware;

- reduction of the measuring base to a value acceptable for the equipment carrier object;

- an exception (due to a decrease in the measuring base) of radio channels.

The technical result of the invention is the ability to determine the range to the IRI, operating outside the radio horizon, the antennas of which can be omnidirectional or highly directional, scanning or stationary.

Range determination is based on measuring the so-called coverage angle of the measuring base, i.e. the angle at which the IRI "sees" the measuring base.

To achieve the specified technical result, a method for determining the range to the source of radio emission is proposed, including:

- detection, direction finding and measurement of the carrier frequency of the IRI signal with a direction finder having at least three receiving points, the antennas of which form a linear measuring base of the direction finder and at the same time are part of two correlation radio interferometers (KRI) [4];

- measurement of the angle of coverage, under which the IRI “sees” the CRI base as the algebraic difference of directions in the IRI measured by correlation interferometers;

- Calculation of the distance to the IRI as the ratio of the projection of the CWI base onto the front plane of the signal coming from the IRI to the angle of coverage of the CWI base, expressed in radians.

The technical result is achieved by the fact that in the proposed method for determining the range, the coverage angle at which the IRI “sees” the CRI base is determined by the algebraic difference of the measured directions on the IRI by two radio interferometers spaced in the horizontal plane.

The use of radio interferometers can significantly simplify the hardware by replacing continuous antennas of direction finders with simple (for example, pin) antenna elements that form the measuring base of the CWI, while having high accuracy in measuring the direction to the IRI and a sufficiently small measuring base and, as a result, eliminating the radio channels between the receiving points.

The proposed method is illustrated by drawings.

FIG. 1. The principle of measuring the angle of coverage.

FIG. 2. The structural diagram of the device for determining the range to Iran.

In the drawings, the following notation:

FIG. 1a. Directions to Iran are close to traverse with respect to the base.

FIG. 1b. Directions to Iran differ from traverse ones.

1, 2, 3 - antenna elements of the phase direction finder, 1 and 2 - antenna elements of the first correlation radio interferometer (KRI), 2 and 3 - of the second KRI;

4 - location of Iran;

5, 6 - phase centers of the 1st and 2nd CWI;

l - KRI base;

7, 8 - normal to the CWI bases;

α ₁ and α ₂ are the directions to the IRI, measured by the 2nd 2nd CWI (the positive direction is to the right of the normal, the negative is to the left of the normal to the base);

Δα is the angle of coverage of the CWI base.

FIG. 2.

1, 2, 3 - antenna elements of the phase direction finder, forming a linear measuring base,

- 1, 2 - base of the 1st KRI;

- 2, 3 - base of the 2nd KRI;

4 - receiving-direction finding unit, calculator heading angle 5 and the frequency of the signal IRI 6;

7 - frequency tunable filters;

8 - controlled phase shifters, 8a - moving the CWI electric axis to the left, 8b - to the right;

9 - multipliers of the received signals;

10 - phase discriminators;

11, 12 - outputs of the multipliers 9;

13, 14, 18, 19 - control circuit phase shifters 8;

15, 20 - signals “stop phase shifters”;

16, 17, 21, 22 - readings of phase shifters;

23 - calculator of the angle of coverage of the CWI base;

24 - range calculator to Iran;

25 - Iran range code;

26 - a signal of acknowledgment of reception of a range code;

27 - reset signal to zero phase shifters.

The method of determining the range to Iran is as follows.

1. The signals emitted by the IRI are received by the antenna elements forming the linear measuring base of the direction finder and at the same time included in the 1st and 2nd correlation radio interferometers (KRI).

2. Received signals are detected, direction-finding and measured by their radiation parameters, including the carrier frequency (wavelength).

3. The signals are processed by the 2nd 2nd CWI, each of which determines the direction to the IRI (α ₁ or α ₂ in Fig. 1) as a deviation from the normal to the IRI base, taken with its own sign (plus - to the right, minus - to the left from the normal), which is controlled by phase shifters 8b and 8a, respectively, whose algebraic sum of phase samples characterizes the direction to the IRI (α ₁ or α ₂ ), and the algebraic difference of the sums is taken as a measure of the angle of coverage Δα, under which the IRI “sees” the CRI base.

4. The distance to the IRI is calculated as the ratio of the projection of the base of the radio interferometer on the front plane of the signal coming from the IRI to the angle of coverage of the base of the radio interferometer, expressed in radians.

The device (Fig. 2), which implements the proposed method, contains:

- phase direction finder with antenna elements 1, 2, 3 and receiving-direction finding unit 4;

- 1st and 2nd radio interferometers, each of which includes two antenna elements (1 and 2 for the first, 2 and 3 for the second radio interferometer), two tunable frequency filters 7, two controlled phase shifters 8a and 8b, the multiplier adopted signals 9 and phase discriminator 10;

- calculator of the angle of coverage of the base of the interferometer 23;

- distance calculator to Iran 24.

The phase direction finder is constructed according to the scheme of a two-base interferometer (see [3], p. 300, Fig. 5.66), the IRI signal is detected and its carrier frequency is determined in the frequency domain using the Fourier transform [5].

Antenna elements 1, 2, 3 can be of various types, mainly with vertical polarization, most often used in VHF radio stations.

Multipliers included in the radio interferometers 9, phase discriminators 10 - traditional devices available in the catalogs of HEWLLET PACKARD and ANALOG DEVICES; quadrature phase modulators of the same companies [6], [7], [8] can be used as controlled phase shifters, frequency-tunable filters 7 are described in [9], [10], [11], smooth frequency tuning in them is carried out varactors.

The original structural elements of FIG. 2 - the calculator of the angle of coverage 23 and the calculator of the range 24 - are made in digital form and contain the ADC and the corresponding functional converters.

The output 25 of the device of FIG. 2 represents the range to the IRI in a digital code that is broadcast to the consumer, a signal 26 confirming receipt of the range code is received from the consumer.

The device (Fig. 2) that implements the method of determining the range to Iran, works as follows. The IRI radio signals are received by the antenna elements 1, 2, 3, forming a linear measuring base of the direction finder, and enter the receiving-direction finding unit 4, where they are coherently amplified in a frequency band significantly exceeding the spectral width of a single IRI signal, and after digitization they undergo Fourier transform. The power spectrum of the signal of the reference antenna element (for example, the first) is compared with the detection threshold, and the frequencies at which the IRI signals are detected are stored; directions to the IRI relative to the measuring base are also calculated. From the stored frequencies, the frequency of the IRI is selected, the distance to which it is necessary to determine, the filters 7 of the 1st and 2nd interferometers are tuned to this frequency, and the width of the individual lobe of the radiation pattern of the CWI is calculated in the base angle calculator 23, which determines the maximum unique value of the base angle λ / 2l and the minimum possible unambiguous range to the IRI 2l ² / λ, where λ is the wavelength of the IRI signal, l is the CRI base. The filters 7 tuned to the selected frequency pass the signals of the selected IRI to the phase shifters 8a and 8b, set to zero, and then to the inputs of the multipliers 9. At the output of the multiplier 9, for example, the 1st KRI, voltage 11 arises, corresponding in amplitude and polarity to one or another the beam of the radiation pattern in the direction of the IRI. The voltage 11 is supplied to the receiving-direction finding unit 4 to generate control signals 13 and 14 of the phase shifters 8a and 8b, respectively, as well as to the phase discriminator 10, which detects the transition through zero of the amplitudes of two adjacent cores of the radiation pattern, the phases of which are opposite, and generates a signal " stop of phase shifters ”15, when the steepness of the direction-finding characteristic of the radio interferometer and the accuracy of measuring its direction in the IRI is greatest. Depending on whether the direction in the IRI is found to the left or right of the maximum (or minimum) of the interference lobe of the interferometer radiation pattern, the control of 13 or 14 of the attenuator 8a or 8b is turned on, the attenuator readings monotonically increase, and the output voltage 11 of the multiplier 9 approaches zero until the moment mentioned above is reached transition points through zero, while the control signal is blocked and the samples of the attenuators 16 and 17, characterizing the direction α ₁ (see Fig. 1), measured by the 1st CWI, are transmitted in the calculation base angle of coverage 23.

A similar process occurs in the 2nd KRI, when the signal 12 of its multiplier 9 generates control signals 18 and 19 of the phase shifters 8a and 8b, and the phase discriminator 10, upon reaching the zero transition, generates a signal “stop phase shifters” 20, and the samples of phase shifters 21 and 22 , characterizing the direction of the IRI α ₂ (see Fig. 1), are translated into the calculator of the angle of coverage of the base 23. The calculator of the angle of coverage of the base 23 performs the following operations:

- calculation of the algebraic difference in the samples of the 1st and 2nd CWI, taking into account the fact that the minus sign for the samples of the phase shifters 8a and the plus sign for the attenuators 8b;

- verification: the difference in readings should not be more than 180 °, i.e. the angle of coverage of the base should be no more than the width of a separate lobe of the bottom of the KRI;

- calculation of the angle of coverage of the base Δα by the formula:

,

,

where λ is the wavelength of the IRI signal;

l - measuring base of CWI;

Δ is the algebraic difference in the samples of the phase shifters,

and gives the code of the angle of coverage Δα in the range calculator 24. Range calculator 24 determines the distance to the IRI by the formula:

,

,

where KU is the direction to Iran (course angle of Iran) relative to the measuring base of the direction finder;

Δα is the angle of coverage of the CWI base, radian.

The range code 25 from the output of the range calculator 24 is transmitted to the consumer and after receiving from the consumer a confirmation of receipt 26 in the receiving-direction finding unit 4, the transition to the next of the stored carrier frequencies of the IRI is carried out, and the process is repeated.

The attainability of the technical result of the invention is confirmed by calculations of passive range measurement for the following conditions (see table):

- the device is located on a ship with a length of at least 200 m;

- base of the radio interferometer l = 100 m;

- wavelength IRI λ = 1 m;

- range to Iran 80 km;

- course angle IRI KU = 70 °;

.- signal-to-noise ratio at the receiving location

.

Thus, due to the introduction of operations:

- measuring the angle of coverage at which the IRI “sees” the CRI base as the algebraic difference of directions in the IRI measured by correlation interferometers (CRI);

- calculating the distance to the IRI as the ratio of the projection of the CWI base onto the front plane of the signal coming from the IRI to the angle of coverage of the CWI base, expressed in radians,

it is possible to solve the problem with the achievement of the technical result.

Information sources

1. RF patent No. 2444748 dated 02.02.2010

2. RF patent No. 2444749 from 07/26/2010

3. Theoretical Foundations of Radar, ed. POISON. Shirman. - M., Soviet Radio, 1970.

4. W. Christiansen, I. Hegbom. Radio telescopes. - M., Mir, 1972.

5. Drogalin V.V. etc. Algorithms for estimating the angular coordinates of the IRI, based on spectral analysis methods. // Successes of modern radio electronics. 1988, No. 2, p. 3-17.

6. Designer's Reference Manual, Analog Devices, Inc., 1996.

7. Hewlett Packard. Communications Components Designer's Cattalog, 1997.

8. Designer's Guide, Hittite Microwave Corporation, 2004.

9. D.P. Andreev et al. Mechanically tunable microwave devices and filters. M., Communication, 1973.

10. A.S. USSR No. 168814, B.I., 1965, No. 5, p. 55.

11. A.S. USSR No. 208046, B.I., 1968, No. 3, p. 54.

Claims (1)

A method for determining the distance to a source of radio emission (IRI), including the detection, direction finding and measurement of the carrier frequency of an IRI signal with a phase direction finder having at least three receiving points, the antennas of which form a linear measuring base of the direction finder and are simultaneously part of the 1st and 2nd correlation radio interferometers (KRI), each of which contains a signal multiplier, two adjustable phase shifters and a phase discriminator, characterized in that the phase shifters of the 1st KRI carry out zero crossing through readings of the 1st phase discriminator, while fixing the algebraic sum of the samples of the phase shifters, which characterizes the direction to the IRI relative to the normal to the base of the 1st CRF, phase shifters of the 2nd CRF carry out the zero reading of the second phase discriminator, fixing the algebraic sum of the samples phase shifters, which characterizes the direction of the IRI relative to the normal to the base of the 2nd GWI, calculate the algebraic difference of the mentioned sums of samples and take it as a measure of the angle of coverage at which the IRI "sees" the GWI base, while It is proportional to the angle of coverage and inversely proportional to the sector of unambiguity of the Raman radiation pattern, and the range to the IRI is calculated as the ratio of the projection of the Raman base on the front plane of the signal coming from the IRI to the angle of coverage of the radiated Raman base.

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