RU2559813C1 - Method of locating navigation object - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: method is based on emitting a high-frequency harmonic signal by a navigation object; receiving said signal at multiple reference radio navigation points with known coordinates, wherein the navigation object additionally emits a second high-frequency harmonic signal differing in frequency from the first signal by a given; at each reference radio navigation points, receiving said signal along with the first signal; generating differential frequency signals from the received signals; transmitting the generated signals to a central receiving station, where the phase difference of the differential frequency signals received from different reference points is measured, and results of said measurements, based on the mutual arrangement of the central receiving station and reference radio navigation points, are converted to coordinates of the navigation object.

EFFECT: high accuracy of locating a navigation object while providing noise-immunity.

2 dwg

Description

The invention relates to radio navigation and can be used in local navigation systems and networks to control the movement of mobile objects in local navigation areas.

Known protected by RF patent No. 2204145, class. G01S 3/46, 2003, a method for determining the coordinates of a radiation source based on the reception of its signal by three antennas forming orthogonal bases.

Such an action as determining the direction to the radiation source is an essential sign of the proposed method.

Also known is protected by a patent of the Russian Federation No. 20133785, class. G01S 13/00, 1994, a method for determining the location of moving objects, which consists in emitting encoded signals by transmitters of objects, receiving signals at N spatially separated points, followed by relaying them to a central receiving point and measuring delays between the received signals.

The relay of signals to the central receiving point is an essential sign of the proposed method.

The reason that impedes the achievement in these analogues, protected by patents of the Russian Federation, of the technical result provided by the invention, is the need to use a rather complex system of uniform time.

The known differential-ranging method for determining the location of mobile objects, which consists in alternately emitting a network of navigation reference points located at points in space with known coordinates, coherent harmonic signals, receiving them on a mobile object, received from each reference object, and calculating the coordinates of the mobile object from them [Bakulev P.A., Sosnovsky A.A. Radar and radio navigation systems. - M .: Radio and communications, 1994, p. 211-214].

The measurement of the phase shifts of the signals and the calculation of the coordinates of the mobile object from them is an essential sign of the proposed method.

The reason that impedes the achievement in this analogue of the technical result provided by the invention is the need to use a high-precision scale of a single time at the navigation object and the difficulty of implementation at large distances between the reference radio navigation points and the navigation object.

The closest in technical essence to the claimed (prototype) is the reversed difference-range-finding method for determining coordinates [Kinkulkin I.E., Rubtsov V.D., Fabrik M.A. Phase method for determining coordinates. - M .: Owls. radio, 1979, p. 10-11, p. 97-100].

The method consists in simultaneously emitting by the navigation object and the transmitter, installed in a fixed point with known coordinates, continuous harmonic high-frequency signals and simultaneously receiving these harmonic signals in several reference radio navigation points.

Such actions as the emission of high-frequency harmonic signals by the navigation object and the reception of radiated harmonic high-frequency signals at reference radio navigation points with known coordinates are essential features of the proposed method.

The reason that impedes the achievement in the prototype method of the technical result provided by the invention is the fact that the coordinates of the fixed transmitter are always determined with some error, which ultimately leads to a decrease in the accuracy of measuring the coordinates of the navigation object.

Another reason that impedes the provision in the prototype method of the technical result provided by the invention is the need for continuous signal emission by a fixed transmitter. This degrades the electromagnetic compatibility of the equipment. There is a need for the simultaneous reception and transmission of two signals with close frequencies, which worsens the conditions for ensuring information security of equipment and facilitates the possibility of suppressing its work by a potential attacker. These circumstances significantly reduce the noise immunity of devices that implement this method.

The technical problem to which the invention is directed is to increase the accuracy of determining the location of the navigation object and the noise immunity of devices that implement the proposed method.

To achieve the specified technical result in the known method of determining the location of the navigation object, which consists in emitting the navigation object of a high-frequency harmonic signal, receiving it at several reference radio navigation points with known coordinates, an additional second high-frequency harmonic signal is different from the navigation object, different in frequency from the first to a given the value at each of these reference radio navigation points receive this signal, like the first, form of the received signals, the difference frequency signals transmit the generated signals to the central receiving point, where the phase difference of the difference frequency signals obtained from different reference points is measured, and the results of these measurements, taking into account the relative position of the central receiving point and reference points, are converted to the coordinates of the navigation object.

The invention is illustrated in the drawing, which shows:

- in FIG. 1 - the relative position of the navigation object and the three reference radio navigation points;

- in FIG. 2 - structure of a differential frequency signal driver.

The method is implemented using three reference radio navigation points with known coordinates and a navigation object.

The operation of the method is illustrated in FIG. 1, which shows a mobile navigation object (MO) located at a point with unknown coordinates X and Y, and reference radio navigation points ORT1, ORT2 and ORT3 located at points with known coordinates X ₁ and Y ₁ , X ₂ and Y ₂ and X ₃ and Y ₃ respectively. There are also shown the distances D ₁ , D ₂ , D ₃ between the navigation object and the reference radio navigation points, as well as the direction N to the north.

Using the transmitter of the navigation object, the sum of two harmonic high-frequency signals with frequencies f ₀ and f _{1 is} radiated in the direction of the points ORT1, ORT2 and ORT3:

These signals have amplitudes A and initial random phases φ ₀ and φ ₁ .

These signals are received at points ORT1, ORT2 and ORT3 at distances D ₁ , D ₂ and D _3, respectively, from the navigation object:

where C = 3 · 10 ⁸ m / s is the propagation velocity of radio waves in the atmosphere.

In each of the reference radio navigation points ORT1, ORT2 and ORT3, difference frequency signals are generated.

The structure of the differential frequency signal generator is shown in FIG. 2. It is a series-multiplier and a narrow-band low-pass bandpass filter.

представляющий собой сумму двух высокочастотных гармонических сигналов с частотами f₀ и f₁, поступает на оба входа перемножителя.In each of the reference radio navigation points, the signal

representing the sum of two high-frequency harmonic signals with frequencies f ₀ and f ₁ , is fed to both inputs of the multiplier.

At the output of the multiplier, a sum of dc voltage and four harmonic signals with frequencies 2f ₀ , 2f ₁ and f ₀ + f ₁ and a difference frequency f _p = f ₀ -f ₁ (beat frequency) is formed. All these harmonic signals, with the exception of the signal with a beat frequency, are suppressed by the filter.

The differential frequency signals generated in each of the reference radio navigation points are:

It is easy to see that the signals generated in each of the reference radio navigation points differ in phase, which are determined by the distances D ₁ , D ₂ and D _3, respectively. These signals are transmitted to the central reception center. As such, for example, one of the reference radio navigation points can be used. For definiteness, we assume that the territorially central reception point is located at the point ORT2.

Thus, the following three signals are received at the central reception point:

1) the signal received from ORT1

амплитудой и дополнительным фазовым сдвигом

который обусловлен прохождением расстояния R₂₁, разделяющего ОРТ1 и центральный приемный пункт (в рассматриваемом случае точку ОРТ2).It is different from the signal

amplitude and additional phase shift

which is due to the passage of the distance R ₂₁ separating ORT1 and the central receiving point (in this case, the point ORT2).

This signal can be represented as follows:

Where

2) the signal directly received at the point ORT2 (central receiving point)

In this case, A ₂₂ = A ₂ , and there is no additional phase shift, since the distance between the point OPT2 and the central receiving point is zero.

This signal can also be represented as

Where

3) the signal received from ORT3

This signal can also be written as:

Исправить в этой формуле индекс: было

а надо

!!!Where

Fix index in this formula: was

and it is necessary

!!!

сигналов

и

и разность фаз

сигналов

и

Find the phase difference

signals

and

and phase difference

signals

and

From these expressions it follows that in these differences there are no random phase shifts φ ₀ and φ ₁ .

и

получим окончательные выражения для расчета неизвестных координат объекта навигации разности Δφ₂₁ фаз сигналов разностной частоты, сформированных второй и первой опорными точками, а также для расчета разности Δφ₂₃ фаз сигналов разностной частоты, сформированных второй и третьей опорными точками:Excluding the known phase shifts from the last expressions for Δψ ₂₁ and Δψ ₂₃

and

we obtain the final expressions for calculating the unknown coordinates of the navigation object of the difference Δφ of ₂₁ phases of the difference frequency signals generated by the second and first reference points, as well as to calculate the difference Δφ of ₂₃ phases of the difference frequency signals generated by the second and third reference points:

Thus, the parameter Δφ ₂₁ is the phase difference of the difference frequency signals between the second and first reference points, and the parameter Δφ ₂₃ is between the second and third reference points. The indicated phase differences uniquely correspond to the differences of the ranges D ₂ -D ₁ and D ₂ -D ₃ respectively.

This allows us to conclude that, according to the results of measurements of the parameters Δφ ₂₁ and Δφ ₂₃ , the parameters D ₁ , D ₂ and D ₃ can be calculated - the distances between the navigation object and reference radio navigation points, and therefore the coordinates of the navigation object.

Below is the algorithm for converting the results of measuring the phase difference of the signals of the differential frequency into the coordinates of the navigation object. This algorithm is applicable for local navigation systems when it is permissible to neglect the sphericity of the Earth, and the propagation velocity of radio waves in the coverage area of the navigation system can be considered constant.

The initial data for the calculation are:

- the difference Δφ of ₂₁ phases of the signals of the differential frequency for the first and second radio navigation points;

- the difference Δφ of ₂₃ phases of the signals of the differential frequency for the third and second radio navigation points.

In addition, the following constants are used in the calculation:

- the value of the first high frequency f ₀ ;

- the value of the second high frequency f ₁ ;

- the propagation velocity of radio waves in the atmosphere C;

- the distance between the first and second reference radio navigation points R ₂₁ ;

- the distance between the third and second reference radio navigation points R ₂₃ .

The calculation procedure is as follows.

1. The differences of distances from the navigation object to the reference points are calculated

Here D ₁ , D ₂ , D ₃ are the distances from the navigation object (MO) to the first ORT1, second ORT2 and third ORT3 of the radio navigation aids in accordance with FIG. one.

2. The values ΔD ₂₁ and ΔD _{23 are} normalized by the lengths of the baselines and the parameter γ is calculated:

3. The constant parameters are determined:

where α ₂₁ is the angle between the north direction and the baseline R ₂₁ ;

α ₂₃ - the angle between the north direction and the base line R ₂₃ .

4. An equation is compiled to calculate the angle β ₂₃ between the base line R ₂₃ and the direction of the navigation object:

This equation is solved for the angle β ₂₃ by any of the iterative numerical methods, for example by halving the interval.

5. The coordinates of the navigation object in the local rectangular coordinate system are calculated, the origin of which is at the point ORT2:

If necessary, the coordinates of the navigation object are converted to the original rectangular coordinate system;

Thus, the proposed method eliminates the inherent method of the prototype component of the error in determining the coordinates of the stationary transmitter of the second harmonic high-frequency signal. In the proposed method, this transmitter is not used, but the same transmitter is used as for the first harmonic signal. Therefore, the accuracy of the measurement of coordinates in the proposed method is significantly higher than in the prototype.

In addition, in the proposed method there is no need for continuous radiation of the second harmonic signal, since it can be emitted only at time intervals sufficient to measure the phase difference of the signals of the difference frequency. This time does not exceed fractions of a millisecond. The short radiation time of the signal makes it difficult to detect, and therefore suppression by a potential adversary. This significantly increases the noise immunity of the equipment that implements the method, compared with the prototype.

The technical implementation of the method does not cause difficulties. As an example of implementation, we consider the implementation of the proposed method for constructing a local navigation system for controlling traffic in high-risk areas where high-precision location of high-speed moving objects is required: on critical sections of their movement paths (for example, when approaching switch points on railway tracks, near steep closed turns of highways). For the implementation of the system, a frequency range of 1200-1400 MHz can be selected. The coverage area of a local navigation can be several hundred meters.

The formation of two harmonic signals (primary and secondary) at the navigation object can be implemented on the basis of two frequency synthesizers synchronized by a common reference oscillator and adder. As frequency synthesizers, for example, ADF4360-5 type microcircuits can be used, which make it possible to form two highly stable harmonic signals with a frequency spacing of (0.1-100) MHz, as a reference oscillator - a NT3225SA thermally stabilized crystal oscillator.

To receive harmonic signals at the navigation reference points, you can use integrated microwave amplifiers - microcircuits of the SPF5122Z type, to logarise the received signals by amplitude, the AD8309 logarithmic amplifier, and a mixer on a BFP620 transistor whose load is a low-pass filter with a frequency slice equal to the difference frequency. The transmission of difference frequency signals from the navigation reference points to the central receiving point can be realized either via wired channels (at small distances between the reference navigation points and the central receiving point - about 100 m), or via radio channels with frequency separation (for more significant distances between reference navigation points and a central receiving point).

The separation of the phase difference of the signals of the difference frequency in the Central receiving point is based on a phase detector (for example, on a SYPD-1 chip or the like).

Analog signals from the output of the phase detector are fed through analog-to-digital converters to the input ports of the STM type microprocessor, which implements the solution of the navigation problem according to the above algorithm.

The method may find application for constructing a local navigation system for controlling traffic in high-risk areas where high-precision location of high-speed moving objects is required, on critical sections of their movement paths (for example, when approaching switch points on railway tracks, near sharp closed turns highways).

Claims (1)

A method for determining the location of a navigation object, which consists in emitting a high-frequency harmonic signal by the navigation object, receiving it at several reference radio navigation points with known coordinates, characterized in that the second high-frequency harmonic signal, different in frequency from the first by a predetermined value, is radiated from the navigation object each of the reference radio navigation points receive this signal, along with the first, form the difference frequency signals from the received signals, the generated signals are transmitted to the central receiving point, where the phase difference of the difference frequency signals obtained from different reference points is measured, while the second high-frequency signal is emitted simultaneously with the first and only for time intervals sufficient to measure the phase difference of the difference frequency signals, and the measurement results differential frequency signals, taking into account the relative position of the central receiving point and reference radio navigation points, are converted to the coordinates of the navigation object.

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