RU2597007C1 - Phase-difference method of locating navigation object - Google Patents

Abstract

FIELD: navigation.

SUBSTANCE: invention relates to radio navigation and can be used in local navigation systems and networks for controlling movement of mobile objects in local navigation areas.

Method is based on simultaneous radiation by a navigation object during a time interval sufficient for phase measurements, of two high-frequency harmonic signals with frequencies differing by a preset value, reception thereof in multiple reference radio navigation points with known coordinates and generation therefrom of differential frequency signals, transmission of said differential frequency signals to a central processing station, measurement therein of phase differences of differential frequency signals received from different reference radio navigation points, wherein from each differential frequency signal in central processing station, a scaling frequency signal is generated, value of which is n times greater than differential frequency, measuring phase difference of signals of scaling frequency generated for different pairs of reference points, and measurement results of phase differences of signals at differential and scaling frequencies are recalculated considering mutual location of reference radio navigation points and central processing station in coordinates of navigation object.

EFFECT: technical result is high accuracy of determining coordinates of navigation object and wider field of space, in range of which unambiguous determination of coordinates of navigation object is possible without reducing accuracy.

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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 with object transmitters, receiving signals at N spatially separated points, followed by relaying them to a central processing point and measuring delays between the received signals.

Relaying signals to a central processing point is an essential feature 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 a method for determining the location of the navigation object (patent application No. 2014116786 of 04.24.2014, the decision to grant a patent of 05.06.2015).

The method consists in simultaneously emitting by the navigation object two high-frequency harmonic signals with frequencies differing by a predetermined value, receiving them at several reference radio navigation points with known coordinates and generating difference frequency signals from them, transmitting said difference frequency signals to a central processing point, measuring the differences in it phases of difference frequency signals obtained from different reference radio navigation points.

Actions such as the radiation of two high-frequency harmonic signals with frequencies different by a given value from the navigation object, their reception at several reference radio navigation points with known coordinates, the formation of difference frequency signals from them, the transmission of these difference frequency signals to a central processing point, and the measurement of differences the phases of the differential frequency signals obtained from different reference radio navigation points are essential features of the proposed method.

The reason that impedes the provision in the prototype method of the technical result provided by the invention is the low accuracy of determining the coordinates of the navigation object in the service area of the radio navigation system using this method.

The dimensions of this service area in the prototype method are limited by the area of space in which the distances between the navigation object and each of the radio navigation reference points should differ from each other by no more than half the wavelength of the signal with a frequency equal to the frequency difference of the high-frequency signals emitted from the navigation object. Only in this case the coordinates of the navigation object can be uniquely determined.

The technical problem to which the invention is directed is to increase the accuracy of determining the coordinates of the navigation object and expand the area of space within which it is possible to uniquely determine the coordinates of the navigation object without reducing accuracy.

To achieve the specified technical result in a known method for determining the location of a navigation object, which consists in simultaneously emitting two high-frequency harmonic signals with different frequencies by a navigation object, receiving them at several reference radio navigation points with known coordinates and generating differential frequency signals from them, transmitting said differential frequency signals to the central processing point, measuring phase differences of the differential hour signals The signals obtained from different reference radio navigation points from each differential frequency signal at the central processing point additionally generate a scale frequency signal, the value of which is n times greater than the differential frequency, measure the phase differences of the frequency frequency signals generated for different reference points, and the measurement results of the differences the phases of the signals at the difference and scale frequencies are recounted, taking into account the relative position of the reference radio navigation points and the central processing point, to the coordinates of the object and navigation.

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 a rectangular coordinate system 0XY;

- in FIG. 2 - zone of unambiguous determination of the coordinates of the navigation object in relation to these points.

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 _MO and Y _MO , radio navigation support points ORT1, OPT2 and OPT3 located at points with known coordinates X ₁ and Y ₁ , X ₂ and Y ₂ and X ₃ and Y _3, respectively, as well as the central processing point (CPO), the distances from which to the points ORT1, ORT2 and OPT3 are respectively R ₁ , R ₂ and R ₃ . There are also shown the distances D ₁ , D ₂ , D ₃ between the navigation object and the reference radio navigation points.

The signal S _MO (t), which is the sum of two harmonic high-frequency signals with frequencies ω ₁ and ω ₂ , is radiated from the navigation object in the direction of the points OPT1, OPT2 and OPT3:

S _MO (t) = A [cos (ω ₁ t + φ ₁ ) + cos (ω ₂ t + φ ₂ )].

These signals emit for a period of time sufficient to carry out phase measurements of these signals (these measurements are carried out in the CPU, more on this will be discussed below). These signals have amplitudes A and initial random phases φ ₁ to φ ₂ .

The emitted MO signal is received at the points OPT1, OPT2 and OPT3, remote from the navigation object at distances D ₁ , D ₂ and D _3, respectively. The signals S ₁ (t), S ₂ (t) and S ₃ (t) received at the indicated points have the following form:

where c = 2.9979 · 10 ⁸ m / s is the propagation velocity of radio waves in the atmosphere.

, представляющего собой сумму двух высокочастотных гармонических сигналов с частотами ω₁ и ω₂, формируют сигналы с разностной частотой ω_р=|ω₁-ω₂| (частотой биений):In each of the reference radio navigation points from the received signal s _i (t)

Representing the sum of the two high-frequency harmonic signals with frequencies ω ₁ and ω _2, produce signals at the difference frequency ω _p = | ω ₁ -ω ₂ | (beat frequency):

These signals differ in amplitudes and phases, which are determined by the distances D ₁ , D ₂ and D _3, respectively. The generated differential frequency signals are transmitted through wire channels to the DSP. Thus, the following three signals are received in the CPU:

1) the signal received from ORT1:

where ν is the harmonic signal propagation velocity along the wire channel.

, который обусловлен прохождением расстояния R₁, разделяющего ОРТ1 и ЦПО.It differs from the signal S _OPT1 (t) in amplitude and an additional phase shift

, which is due to the passage of the distance R ₁ separating ORT1 and CPO.

This signal can be represented as follows:

s _C1 (t) = A _C1 cos [ω _p t + ψ ₁ ],

;Where

;

2) the signal received from ORT2:

, который обусловлен прохождением расстояния R₂, разделяющего ОРТ2 и ЦПО.It differs from the signal S _OPT2 (t) in amplitude and an additional phase shift

, which is due to the passage of the distance R ₂ separating ORT2 and CPO.

This signal can also be represented as:

_C2 s (t) = A _C2 Cos [ω _p t + ψ _2]

;Where

;

3) the signal received from OPT3:

, который обусловлен прохождением расстояния R₃, разделяющего OPT3 и ЦПО.It differs from the signal S _OPT3 (t) in amplitude and an additional phase shift

, which is due to the passage of the distance R ₃ separating OPT3 and CPU.

This signal can also be written as:

S _Ц3 (t) = A _Ц3 cos [ω _p t + ψ ₃ ],

Where

The phase difference Δψ ₂₁ = ψ ₂ -ψ _{1 of} signals s _Ц2 (t) and s _Ц1 (t), and the phase difference Δψ ₂₃ = ψ ₂ -ψ _{3 of} signals s _Ц2 (t) and s _Ц3 (t) are measured in the central processing unit:

As follows from these expressions, the phase differences Δψ ₂₁ and Δψ ₂₃ do not depend on the initial phases of the emitted MO signals φ ₁ and φ ₂ .

и

в уравнениях для разностей фаз Δψ₂₁ и Δψ₂₃ представляют собой фазовые набеги сигналов разностной частоты при их распространении из опорных радионавигационных точек к ЦПО. Они не зависят от пространственного положения объекта навигации и полностью определяются лишь расположением ЦПО относительно точек ОРТ1, ОРТ2 и OPT3. Эти величины можно рассчитать заранее.Second terms

and

in the equations for the phase differences Δψ ₂₁ and Δψ ₂₃ are phase incursions of signals of difference frequency during their propagation from the reference radio navigation points to the CPO. They do not depend on the spatial position of the navigation object and are completely determined only by the location of the CPO relative to the points ORT1, ORT2 and OPT3. These values can be calculated in advance.

и

. В результате находят разности фаз сигналов разностной частоты для опорных точек ОРТ2 и ОРТ1, а также ОРТ2 и OPT3 с учетом фазовых набегов. Эти разности фаз используются для вычисления разности дальностей D₂-D₁ и D₂-D₃, которые, в свою очередь, используют для вычисления координат объекта навигации.From the phase differences Δψ ₂₁ and Δψ ₂₃ measured in the CPO, the above-mentioned phase incursions are subtracted

and

. As a result, the phase differences of the difference frequency signals are found for the reference points ORT2 and ORT1, as well as ORT2 and OPT3, taking into account phase incursions. These phase differences are used to calculate the distance difference D ₂ -D ₁ and D ₂ -D ₃ , which, in turn, are used to calculate the coordinates of the navigation object.

An unambiguous determination of the coordinates of the navigation object is possible only in that region of space for which the phase differences Δψ ₂₁ and Δψ _{23 of the} signals of the difference frequency do not go beyond the interval [-π / 2 ÷ π / 2]. This condition is satisfied if, within the specified space region, the distances from any of its points to any of the reference radio navigation points differ by no more than half the wavelength λ _{p of the} signal of the difference frequency ω _p . The region of space for which this condition is satisfied is bounded by the quadrilateral ABEF, the sides of which are the position lines AB, EF, BE, and AF (Fig. 2), the equations of which have the following form:

для линии AF и

для линии BE, а параметр L₂ равен

для линии АВ и

для линии EF.where the parameter L ₁ is equal

for the AF line and

for line BE, and parameter L ₂ is

for line AB and

for line EF.

To expand the region of unambiguous determination of coordinates, it is necessary to increase the value of λ _p and, therefore, to reduce the value of the difference frequency ω _p . It should be noted that this way of expanding the region of unambiguous determination of coordinates leads to a decrease in the accuracy of determination of coordinates.

In order to prevent a decrease in the accuracy of determining the coordinates in the proposed method for signals received by the central processing unit from different pairs of ORTs, phase measurements are carried out at two frequencies - on the differential ω _p and on the scale ω _m , which is n times (approximately an order of magnitude) higher than the difference. To do this, the signals s _Ts1 (t) ÷ s _Ts3 (t) received in the DSP are multiplied by frequency by a factor of n, resulting in an additional three more signals with a scale frequency of ω _m .

In this case, direct phase measurements are unambiguous only at the difference frequency ω _p , and at the scale frequency ω _{m the} results of direct phase measurements are ambiguous. To calculate the coordinates of the navigation object, the actual phase differences Δψ ^{Φ of the} signals at the scale frequency ω _{m are used} for two different ORTs, which are calculated based on the results of phase measurements as follows:

и

- разности фаз сигналов, измеренные в ЦПО на частотах ω_м и ω_р;Where

and

- phase differences of the signals measured in the DPC at frequencies ω _m and ω _r ;

int (x) is the integer part of the argument x.

на частоте ω_р.The value of k is an integer number of periods of the signal with a frequency of ω _m , which fits into the time interval corresponding to the measured phase difference

at a frequency ω _p .

The values of the coefficients k and the actual phase differences Δψ ^Φ are found for each pair of ORT.

Below is the algorithm for converting the results of phase measurements 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:

сигналов, измеренная в ЦПО на частоте ω_р для радионавигационных точек ОРТ1 и ОРТ2;- phase difference

signals measured at a frequency ω ATEC _p for the navigation points and OPT2 ORT1;

сигналов, измеренная в ЦПО на частоте ω_р для радионавигационных точек ОРТ2 и OPT3;- phase difference

signals measured in the CPO at a frequency of ω _r for the radio navigation points ORT2 and OPT3;

сигналов, измеренная в ЦПО на частоте ω_м для радионавигационных точек ОРТ1 и ОРТ2;- phase difference

signals measured in the CPO at a frequency of ω _m for the radio navigation points ORT1 and ORT2;

сигналов, измеренная в ЦПО на частоте ω_м для радионавигационных точек ОРТ2 и OPT3.- phase difference

signals measured in the DPC at a frequency of ω _m for the radio navigation points ORT2 and OPT3.

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

- the value of the first high frequency ω ₁ ;

- the value of the second high frequency ω ₂ ,

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

- the propagation speed of the radio signal through the wired channel ν;

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

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

- the distances R ₁ , R ₂ and R ₃ between the CPO and ORT1, ORT2 and OPT3, respectively;

- coefficient n of excess of the scale frequency over the differential.

The calculation procedure is as follows.

1. The difference and scale frequencies ω _p = | ω ₁ -ω ₂ | _m and ω = n · ω _p.

2. The values are calculated

3. Calculate the difference between the actual phases of the signals for pairs of points OPT2-ORT1 and OPT2-OPT3 at frequency ω _m:

4. The navigation problem is solved - the coordinates of the navigation object are determined:

a) 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 OPT3 of the radio navigation aids in accordance with FIG. one;

b) ΔD ₂₁ and ΔD ₂₃ are normalized according to the lengths of the baselines, and the parameter γ is calculated:

c) constant parameters are determined:

α = α ₂₁ -α ₂₃ ; b = γΔd ₂₃ -Δd ₂₁ ,

и базовой линией R₂₁;where α ₂₁ is the angle between the axis

and a baseline of R ₂₁ ;

и базовой линией R₂₃;α ₂₃ - the angle between the axis

and a baseline of R ₂₃ ;

d) by any of the numerical iterative methods, the equation for calculating the angle β ₂₃ between the base line R ₂₃ and the direction to the navigation object is solved:

cos (α-β ₂₃ ) -γcosβ ₂₃ = b;

d) the distance D ₂ from the point ORT2 to the navigation object is calculated

f) the coordinates of the navigation object are calculated in the local rectangular coordinate system, 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

The fact that the proposed method uses a scale frequency ω _m , and phase measurements are performed at two frequencies, allows us to conclude that the proposed method can significantly expand the area of space in which it is possible to uniquely determine the coordinates of the navigation object, compared to the prototype and at the same time degrade the accuracy of their measurement.

In the proposed method, for such an extension, it is sufficient to choose the frequency ω _p sufficiently low, and the coefficient n of excess of the scale frequency over the difference frequency rather high.

For the example of FIG. Figure 2 shows two shaded areas of space bounded by quadrangles ABEF and GNMK, respectively, in which an unambiguous determination of the coordinates of the navigation object is possible. The ABEF quadrangle corresponds to a beat frequency that is approximately five times smaller than the GNMK quadrangle.

In the prototype method, the beat frequency is selected sufficiently low, for example, equal to ω _p , to ensure the uniqueness of phase (and, accordingly, coordinate) measurements in the entire service area of the radio navigation system. This circumstance does not allow, with limited accuracy of phase measurements, to obtain high accuracy in determining the coordinates of the navigation object.

In the proposed method, phase measurements are carried out not only at a frequency ω _p , but also at a frequency ω _m , which is n times (about an order of magnitude) higher than ω _p , while measurements at a frequency ω _p are used only to eliminate the ambiguity of phase measurements, and the final phase measurements are carried out precisely at a higher frequency ω _m , as a result of which, with the same relative error of the phase measurements, the absolute error decreases n times.

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 the local navigation system 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, in which it is possible to change the frequency by applying the corresponding digital codes to the control inputs and which allow generating two highly stable harmonic signals with a frequency spacing of (0.1-100) MHz, as a reference oscillator, a thermally stabilized quartz oscillator type NT3225SA.

To receive harmonic signals at reference radio navigation points, you can use integrated microwave amplifiers - microcircuit type SPF5122Z. As a node for generating the differential frequency signal, you can use a mixer on the BFP620 transistor, the load of which is a low-pass filter with a cut-off frequency of 10 MHz.

The transmission of difference frequency signals from the reference radio navigation points to the central receiving point can be realized via wired channels, or via radio channels with frequency separation.

The amplitude of the signals received at the central processing center is normalized by amplitude limiting the received differential frequency signals using AD8309 logarithmic amplifiers.

Frequency multiplication ω _p can be realized by hard amplitude limitation of a harmonic signal with frequency ω _p followed by frequency filtering of the required harmonic or based on phase locked loop schemes in which a harmonic signal with frequency ω _p is used as a reference signal.

The measurement of the phase difference of the signals of the difference frequency in the Central receiving point can be implemented using a phase detector on the chip SYPD-1.

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 in the construction of local navigation systems 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, on the sorting hills of railway stations, for the automated control of agricultural machines).

Claims (1)

A phase-difference method for determining the location of a navigation object, which consists in simultaneously emitting two high-frequency harmonic signals with different frequencies by a navigation object, receiving them at several reference radio navigation points with known coordinates and generating differential frequency signals from them, and transmitting the indicated difference frequency signals to a central point processing, measuring in it the phase differences of the differential frequency signals obtained from different reference radio navigation of points, characterized in that from each difference frequency signal at a central processing point, a scale frequency signal is additionally generated, the value of which is n times greater than the difference frequency, the phase differences of the scale frequency signals generated for different pairs of reference points are measured, and the results of measurements of phase differences signals at the difference and scale frequencies are recounted taking into account the relative position of the reference radio navigation points and the central processing point to the coordinates of the navigation object.

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