RU2565067C1 - Bearing measurement method and apparatus therefor - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: group of inventions relates to radio direction-finding and can be used to determine the bearing of radio-frequency sources of composite signals in conditions where the antenna is tilted relative to the bearing plane. The result is achieved due to that the inventions are based on the use of a differential-phase method. Said result is achieved due to that a bearing is formed from the phase (α) of a modulating wave. The pitch (θ) and roll (γ) values of the aircraft are used to generate the tilt parameter of the antenna of a radio direction-finder [cos(γ)] relative to the bearing plane and the angle (φ) of the direction of the minor axis of an ellipse, its projection on the bearing plane relative to the heading of the aircraft, which is subtracted from the phase value. The resultant difference is used to generate values of a cosine function {cos(α-φ)} and a sine function {sin(α-φ)}; the sine function is then multiplied by the tilt parameter {cos(γ)·sin(α-φ)}, after which a double arctangent function is calculated. The value of the function is summed with the previously subtracted angular value of the direction of the minor axis of the ellipse (φ) relative to the heading in the bearing plane {atan2[cos(α-φ), cos(γ)·sin(α-φ)]+φ}, wherein the summation result is the desired bearing. A radio direction-finder which realises the method includes an antenna consisting of N dipoles arranged on a circle, a switch, two receivers, a π/2 phase changer, an antenna tilt compensator and a spatial orientation coordinate converter, connected to each other in a certain manner.

EFFECT: high accuracy bearing measurement.

2 cl, 5 dwg

Description

The group of inventions relates to direction finding and can be used to determine the bearing of a source of radio emission (IRI) of complex signals under conditions of the antenna tilting relative to the direction-finding plane.

A known method for determining the bearing, based on the use of the Doppler effect due to phase modulation arising from the circular rotation of the receiving antenna (V. A. Vartanesyan, E. Sh. Goikhman, M. I. Rogatkin. Radio direction finding. - M., Military Publishing, 1966, 248 pp. / § 5.4 /), as a result of which the instantaneous EMF in the antenna can be written as

Here: λ is the wavelength of the direction-finding signal, α is the azimuth to the transmitter, R is the radius of the antenna, and Ωt is the current value of the azimuth of rotation of the antenna. Given this expression, for small values of the phase modulation index 2πR / λ and using a phase detector, it is possible to isolate the oscillations of the modulating frequency Ω, whose phase corresponds to the azimuth α in the IRI.

There is also a device for determining the bearing in this way (Belyaevsky L.S., Novikov V.S., Olyanjuk P.V. Radio navigation basics: A textbook for universities of civil aviation. M: Transport, 1982. - S. 288. Page. 76, Fig. 3.10). The device contains an antenna, which includes a rotating circular dipole (or N switched dipoles and a switch) and a fixed dipole located in the center of the circle, two receivers whose inputs are connected to the corresponding outputs of the antenna (rotating and fixed dipoles), and the outputs are connected to phase detector. The rotation of the antenna (switching dipoles) is carried out synchronously with the reference voltage generator, and the azimuth is determined using a phase meter, the inputs of which are connected to the output of the phase detector and the reference voltage generator.

In this device and this direction finding method, at small R / λ values, the voltage at the output of the phase detector contains mainly the first harmonic of the antenna rotation frequency Ω. At large R / λ values, the shape of the voltage curve is sharply distorted, which leads to errors in determining the direction of the IRI. The potential accuracy of determining the bearing in this method for expressing the standard error (RMS) can be in accordance with (Monakov A.A. Theoretical foundations of radio navigation: Textbook. Manual / SPbGUAP. St. Petersburg, 2002. p. 54, equation 5.27) can be written as

Here q ² is the signal-to-noise ratio, J ₁ (kR) is the Bessel function of the first kind to extract the first harmonic of the argument.

There is also a known method of direction finding, also based on the Doppler effect, but due to the mutual phase modulation that occurs when the two receiving antennas rotate in a circular fashion (V.A. Vartanesyan, E.Sh. Goikhman, M.I. Rogatkin. Radio direction finding. - M., Military Publishing House, 1966, 248 pp. / § 5.4 /), which is called differential-phase and is the closest in combination of essential features to the proposed method. According to this method, the phase difference is measured between the voltages removed from two synchronously rotating (switching) with an angular velocity Ω, shifted between each other by an angle β dipoles. In this method, the phase modulation index will be

. $$\Delta \varphi =\frac{\mathrm{four}\pi }{\lambda }R\sin \left(\beta /2\right)$$

.

Devices are also known for determining the bearing by this method (Belyaevsky L.S., Novikov V.S., Olyanyuk P.V. Radio navigation basics: A textbook for universities of civil aviation. M: Transport, 1982. - p. 288. Pages. 80, Fig. 3.12) and (Monakov A.A. Theoretical foundations of radio navigation: Textbook / SPbGUAP. SPb., 2002. 70 pp., Ill. P. 55, Fig. 5.13). The latter is selected as a prototype. The device contains an antenna, which consists of two dipoles rotating around the circumference (or two pairwise switched dipoles using a switch: [1 and 2], [2 and 3], ..., [N-1 and N], [N and 1] , etc.), two receivers whose inputs are connected to the corresponding outputs of the antenna (through a switch to two pairwise switched dipoles), the output of the first receiver is connected to the first input of the phase detector, and the output of the second receiver through the phase shifter to π / 2 is connected to the second input of the phase detector. The rotation of the antenna (switching dipoles) is carried out synchronously with the reference voltage generator, and the azimuth is determined using a phase meter, the inputs of which are connected to the output of the phase detector and the reference voltage generator. The potential accuracy in the differential-phase direction finding method for expressing the standard deviation can be in accordance with (Monakov A.A. Theoretical Foundations of Radio Navigation: Textbook / SPbGUAP. SPb., 2002. 70 pp., Ill. Page 56, equation 5.31) write in form

When using this method and device at the time of determining the bearing, a significant error is made by the position of the antenna relative to the direction-finding plane. This effect is especially pronounced for mobile direction finders that are mounted on the hull of an aircraft (Aircraft). The fact is that for stationary direction finders this effect is not noticeable due to the small deviation of the antenna from the direction-finding plane, because the distance to Iran is incommensurably greater than its height, i.e. deviations from the direction-finding plane. For mobile direction finders mounted on aircraft, this deviation can be very large at the time of the last maneuver.

The cause of errors in determining the bearing associated with the position of the antenna relative to the direction-finding plane can be explained using simple geometric patterns presented in figure 1.

If the antenna, which is a set of dipoles evenly spaced around each other around the circumference, is tilted to the direction-finding plane, then its projection onto this plane will take the form of an ellipse. Depending on the angle of inclination, the ratio between the semiaxes of this ellipse changes, i.e. the greater the slope, the more it becomes “flattened”.

Now, if a plane wave falls from the direction α1 from the IRI, then for a circle at point 1, this direction is perpendicular to the circle. The same direction is perpendicular to the ellipse at point 2, so if a straight line is drawn from point 2 to the center, then it will already make an angle α2 with a vertical reference line. The difference Δα = α2-α1 is the error of the measured bearing value, which depends on the antenna tilt. In addition, it is periodic and also depends on the direction to Iran. Moreover, in the first and third quarters of the ellipse this error is positive, in the second and fourth it is negative, and in directions close to the minor and major axes of the ellipse, it is minimal. If the direction finder antenna deviates from the normal by 40 ° ... 60 °, and this is quite possible for the aircraft on which the antenna is installed, the error can reach 20 ° ... 30 ° or more.

The technical result of the group of inventions is to increase the accuracy of determining the bearing by compensating for errors due to the tilt of the antenna relative to the direction-finding plane.

The specified technical result is achieved by the fact that in the method for determining the bearing of the source of radio emission by the aircraft’s airborne direction finder, the differential-phase method in which the bearing is formed from the phase (α) of the modulating oscillation according to the invention from the angular values of pitch (θ) and roll (γ ) Aircraft form the antenna tilt parameter of the direction finding antenna [cos (γ)] relative to the direction-finding plane and the angle (φ) of the direction of the minor axis of the ellipse, its projection onto the direction-finding plane, relative to the course of the aircraft, which is subtracted from phase, form the values of the cosine functions {cos (α-φ)} and sine {sin (α-φ)}, then the sine function is multiplied by the slope parameter {cos (γ) · sin (α-φ)}, then calculate the double arc tangent function, the value of which is added to the previously subtracted angular value of the direction of the small axis of the ellipse (φ) relative to the course in the direction-finding plane {atan2 [cos (α-φ), cos (γ) · sin (α-φ)] + φ}, and the summation result is the desired bearing.

In the device for implementing the method, the indicated technical result is achieved in that an on-board direction finder containing a series-connected antenna consisting of N dipoles arranged in a circle, a switch and two receivers, a phase shifter at π / 2 and a phase detector, the first input of which is connected to the output the first receiver, and the second, through the phase shifter, to the output of the second receiver, the phase meter and the reference voltage generator, the outputs of which are connected to the control input of the switch and the second input of the phase meter, are the first the input of which is connected to the output of the phase detector, according to the invention, an antenna tilt compensator and a spatial orientation coordinate converter (PKPO) are introduced into it, while the input of the antenna tilt compensator is connected to the phasemeter output, the control inputs are connected to the PKPO outputs, and the output of the antenna tilt compensator is an output direction finder, while the control panel inputs are the control inputs of the direction finder.

It is known that the spatial position of the aircraft relative to the Earth is determined by the pitch (θ), roll (γ) and yaw (Ψ) angles The antenna tilt relative to the measurement plane is determined only by pitch and roll angles:

θ - Pitch, this is the angle between the longitudinal axis of the aircraft and the local horizontal plane. The pitch angle is positive when the longitudinal axis is above the horizontal plane. In FIG. 2 rotation of the axes X → X ′ and Z → Z ′, around the axis Y.

γ - Roll, this is the angle between the transverse axis OZ ″ (aircraft symmetry) and the axis OZ, the normal coordinate system, shifted to a position at which the yaw angle is zero. It is associated with angle β, which in FIG. 2 is defined as the rotation of the axes Z ′ → Z ″ and Y → Y ″, around the axis X ′.

These characteristics on board a modern aircraft are used by the pilot and automation to effectively control them, and are also recorded in the equipment for the purpose of diagnosis and subsequent analysis, i.e. information on the spatial position of the aircraft on board is always present and can be used. To do this, it is enough to form the values from the angular spatial coordinates θ and γ: cos (γ), which determines the ratio of the axes ( a , c) of the ellipse, and the angle φ, which determines the direction of its minor axis relative to the aircraft course, with which error compensation is performed, due to the deviation of the position of the antenna from the direction-finding plane.

In accordance with the cosine theorem for trihedral angles (in Fig. 2 -

cos (β) and cos (γ)),

where cos (Z) is the cosine of the dihedral angle at the edge OZ, and cos (Z ′) is at the edge OZ ′, but since

, а учитывая (5), будем иметь Respectively $$\cos \left(Z\right)=\frac{\cos \left(\beta \right)-\cos \left(\vartheta \right)\cdot \cos \left(\gamma \right)}{\sin \left(\vartheta \right)\cdot \sin \left(\gamma \right)}$$

, and taking into account (5), we will have

According to the claimed method for determining the bearing, the angular coordinates of the aircraft orientation are converted to values that determine the shape of the ellipse, like the projection of a circular antenna onto the direction finding plane, and the direction of its minor axis relative to the aircraft course, which is chosen as a conditionally zero direction relative to which compensation is performed. Then, from the phase value corresponding to the bearing determined with an error due to the inclination of the antenna, the angular direction value of the small axis of the ellipse relative to the course is subtracted, which allows the conditionally zero azimuth position to be combined with this axis, regardless of the position of the IRI and the antenna inclination. After that, the error in determining the bearing relative to the conditionally zero direction is compensated, while the error value also depends on the direction relative to the axes of the ellipse, then the previously subtracted value of this conditionally zero direction is added to the result. By these operations, an accurate determination of the error due to the tilt of the antenna and its compensation are achieved, for this purpose, a compensator for tilting the antenna and the control panel are introduced into the bearing detection device.

The group of inventions characterized by the above essential features as of the filing date of the application is not known in the Russian Federation and abroad and meets the requirements of the “novelty” criterion.

The applicant has not identified technical solutions having features that match the sets of distinctive features of the claimed inventions, ensuring the achievement of the claimed technical result, and therefore it can be concluded that the inventions comply with the patentability condition "inventive step".

The inventions can be implemented industrially using well-known technical means, technologies and materials and meet the requirements of the patentability conditions "industrial applicability".

The invention is illustrated by graphic materials, where:

- in FIG. 1 shows the cause of the error in determining the bearing due to the tilt of the antenna, the projection of which onto the direction-finding plane from the circle is converted into an ellipse;

- in FIG. Figure 2 shows the relationship of the direction (φ) of the minor axis of the ellipse and the ratio of its axes ( a , c), determined by the value of cos (γ), with the angular coordinates of the orientation (θ and γ);

- in FIG. 3 shows a structural diagram of an airborne direction finder;

- in FIG. 4 is a diagram of an antenna tilt compensator;

- in FIG. 5 is a diagram of a coordinate orientation coordinate converter.

In a method for determining a bearing according to the invention:

- the angular coordinates of spatial orientation θ - pitch and γ - roll are converted to the value cos (γ), which determines the ratio of the axes ( a , c) of the ellipse, and the angle (φ) of the direction of its minor axis relative to the course;

- then this angle is subtracted from the phase value corresponding to the bearing determined with an error due to the tilt of the antenna;

- using the result obtained, the trigonometric functions cos (α-φ) and sin (α-φ) are calculated, while the second is multiplied by the value cos (γ);

- then, using a pair of these values, the inverse function is calculated - the double arc tangent atan2 [cos (α-φ), cos (γ) · sin (α-φ)], the result of which is the compensation of the bearing error with respect to the small axis of the ellipse;

- the result obtained is summed up with the previously subtracted angle (φ) of the direction of the small axis of the ellipse, after which the bearing value is already determined relative to the initial aircraft course, but without error due to the tilt of the antenna.

An on-board direction finder, the block diagram of which is shown in FIG. 3 includes a series-connected antenna 1, consisting of N dipoles arranged in a circle, a switch 2 and two receivers 3 and 4, as well as a phase shifter 5 on π / 2 and a phase detector 6, the first input of which is connected to the output of the first receiver 3, and the second through the phase shifter 5 to the output of the second receiver 4, as well as the phase meter 7 and the reference voltage generator 8, the outputs of which are connected to the control input of the switch 2 and the second input of the phase meter 7, the first input of which is connected to the output of the phase detector 6.

According to the invention, an antenna tilt compensator (KNA) 9 and a spatial orientation coordinate converter (PKPO) 10 are introduced in the direction finder, while the input of the KPA 9 is connected to the output of the phase meter 7, the control inputs are connected to the outputs of the PKPO 10, and the output of the KPA 9 is the output of the direction finder, the inputs of the control panel 10 are the control inputs of the direction finder.

The method for determining the bearing is implemented by the proposed device as follows.

Under the influence of the electromagnetic field, which is created by the direction-finding IRI, signals are formed on the dipoles of the antenna 1, the phase value of which depends on the direction of the IRI and the tilt of the antenna of the airborne direction finder. These signals, switched by the switch 2, through the receivers 3 and 4, as well as the phase shifter 5, are fed to the inputs of the phase detector 6, where a low-frequency harmonic corresponding to the modulation frequency determined by the switching of the dipoles, which is fed to the first input of the phasemeter 7, is released. Simultaneously with the reference voltage generator 8, the control signals are supplied to switch 2 and the second input of the phasemeter 7. At the output of the phasemeter, a phase value is generated corresponding to the direction to the IRI, offset from the error due to the tilt of the antenna, which arrives at KNA 9. At the same time, angular orientation values θ — pitch and γ — roll of the aircraft, on which the direction finder antenna is mounted, are received at PKPO 10 and converted to values that determine the parameters of the ellipse and the orientation of its minor axis relative to the course of the aircraft. From the output of the control panel 10, these values are sent to the corresponding control inputs of the KNA 9, where the angular value of the direction of the small axis of the ellipse is subtracted from the phase value determined taking into account the antenna tilt. This allows you to determine the magnitude of the error, which depends on the parameters of the ellipse and the direction of the IRI relative to its minor axis, combined with a conditionally zero direction. This error is excluded from the phase value relative to the conditionally zero direction, and after that the result is added to the previously subtracted angular direction of the small axis of the ellipse, which is the true direction to the IRI. In determining the error, and after its elimination, the angular value of the direction of the small axis of the ellipse is subtracted first, and then the same value is summed. In addition, the dependence of this error on the movement along the ellipse arc changes smoothly, therefore, the inaccuracy in determining the direction of the small axis of the ellipse has little effect on the result of compensation for errors due to the tilt of the antenna.

This method of determining the bearing of a source of radio emission (IRI) of complex signals under conditions of the antenna tilting relative to the direction-finding plane is confirmed by simulation results.

и $${\alpha }_2^{\text{'}}={\mathrm{247,68}}^{\circ }$$

соответственно, а после компенсации ошибок получили $${\alpha }_1^{"}={\mathrm{120,73}}^{\circ }$$

и $${\alpha }_2^{"}={\mathrm{239,86}}^{\circ }$$

- значения, близкие к истинным направлениям.During the simulation, the heel angles γ = 0 ° and the pitch θ = 45 ° were set, and the true position of the IRI was set in the directions α ₁ = 120 ° and α ₂ = 240 °, corresponding to the second and third quarters. With this in mind, their directions were determined $${\alpha }_{\mathrm{one}}^{\text{'}\text{'}}={112.8}^{\circ }$$

and $${\alpha }_2^{\text{'}\text{'}}={247.68}^{\circ }$$

respectively, and after compensation for errors received $${\alpha }_{\mathrm{one}}^{"}={120.73}^{\circ }$$

and $${\mathrm{<figure-callout\; id="2"\; label="\alpha "\; filenames="00000014.png"\; state="\{\{state\}\}">\alpha </figure-callout>}}_2^{"}={239.86}^{\circ }$$

- values close to true directions.

Claims (2)

1. The method of determining the bearing of the source of radio emissions by the aircraft’s airborne direction finder by the differential-phase method, in which the bearing is formed from the phase (α) of the modulating oscillation, characterized in that the parameter is formed from the angular pitch (θ) and roll (γ) of the aircraft the angle of the direction finder antenna [cos (γ)] relative to the direction-finding plane and the angle (φ) of the direction of the small axis of the ellipse, its projection onto the direction-finding plane, relative to the aircraft course, which is subtracted from the phase value, from this difference the values of functions cosine {cos (α-φ)} and sine {sin (α-φ)}, then the sine function is multiplied by the slope parameter {cos (γ) · sin (α-φ)}, after which the double arc tangent function is calculated, the value of which summarize with the previously subtracted angular value of the direction of the small axis of the ellipse (φ) relative to the course in the direction-finding plane {atan2 [cos (α-φ), cos (γ) · sin (α-φ)] + φ}, while the summation result is the desired bearing. 2. An on-board direction finder containing a series-connected antenna consisting of N dipoles arranged in a circle, a switch and two receivers, a phase shifter at π / 2 and a phase detector, the first input of which is connected to the output of the first receiver, and the second through the phase shifter to the output the second receiver, a phase meter and a reference voltage generator, the outputs of which are connected to the control input of the switch and the second input of the phase meter, the first input of which is connected to the output of the phase detector, characterized in that antenna tilt compensator and spatial orientation of the coordinate converter (PKPO), the antenna tilt compensator input connected to the output of the phase meter, control inputs connected to outputs PKPO and antenna tilt compensator output is the output of the direction finder, the PKPO inputs are the control inputs finder.

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