RU2469349C1 - Method of determining range to object with emitting source of signals with different frequencies - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: method of determining range to an object with an emitting source of signals with different frequencies involves simultaneous reception of not less than two signals with different frequencies and subsequent measurement of the phase of the received signals relative the phase of the signals from a reference generator, characterised by that the measured phase value of each signal is converted to a digital value of the time interval between the signal from the reference generator and the received signal, and distance is calculated using a defined formula using the Chinese remainder theorem.

EFFECT: high accuracy and reliability of determining range in a non-request mode to a radiation source of two more frequencies using one receiving station.

2 dwg

Description

The invention relates to the field of passive radar and can be used in complexes that determine the parameters of the motion by a non-request method, as well as in systems using signals from satellite radio navigation systems (SRNS).

There is a method of determining the distance to the source of radio emission and the speed of approach of the aircraft with it, which consists in the fact that at time t1 receive radio signals from a source of radio emissions (IRI) and measure the angle of rotation of the antenna in the horizontal φ _ag and vertical φ _av planes, according to the accepted the radio signals and the measured values of the angles of rotation of the antenna evaluate the values of the angles of the IRI bearing φ _g , φ _in and the angular velocities of its line of sight ω _g , ω _in the two mentioned planes, according to the estimated values of the angles p the IRI angular velocity and the angular velocities of its line of sight calculate the extrapolated values of the angles of the IRI bearing φ _eg and φ _EV for the next clock cycle of the signals, from the extrapolated values of the angles of the IRI bearing φ _eg and φ _EV and the values of the antenna rotation angles φ _ag and φ _av generate signals for control an antenna for which it is set in the direction of IRI measured pulse repetition frequency f _n received radio signals, and if the pulse repetition frequency Fp received radio signal is low or average, then at time t ₂ = t ₁ + Δt, where Δt - belt measurement processing interval measured values of the angles of rotation of the antenna in the horizontal φag and vertical φav planes, as well as the speed V of the aircraft and then receive radio signals from the emitter, on the received radio signals and the measured antenna rotation angles values evaluated value bearing IRI angles φ _r, φ _in and angular velocities of the line of sight ω _g , ω _in in the respective planes, measure the value of the speed V of the aircraft, calculate the distance D to the IRI according to the formula

Measured values IRI φ _{g of} bearing angles, φ _a, angular velocities boresight ω _z, ω _in and range D give consumers information, and if the received radio signal the pulse repetition frequency Fp is high, the measured maximum Tmax and the minimum Tmin values of the repetition period of pulses received radio signals , as well as the duration of the cycle TC changes the repetition period of these pulses, calculate the distance to the IRI D and the speed of approach with the IRI V _sat according to the formulas

where C is the propagation speed of electromagnetic waves, and the symbol INT means the operation of rounding to the number obtained in curly brackets, the calculated values of the range D and the approach speed V _{sb are} filtered, forming their estimated values of D ^/ and V ^/ sb, the estimated values of the angles of the IRI bearing φ _g , φ _in , angular velocities of the line of sight ω _g , ω _in , range D ^/ and approach speed V ^{/ s} give information to consumers, then the above process is repeated (Russian Federation patent 2251709, IPC G01S 13/42).

The disadvantage of this method is the relative complexity and the need for a time interval for determining the range. However, the most significant drawback is the low accuracy of determination.

As a prototype, a method has been adopted for estimating the current coordinates of a radiation source, which consists in receiving the emitted target signal from each of the M + 1 elements of an equidistant linear antenna array (AR) located relative to each other at a distance of half the wavelength λ0 of the radiation source, amplifying it in each receiving channel , measuring the frequency f of the received signal, generating using phase meters signals proportional to the phase difference of the signals in the central and each of the receiving channels, determining the direction of the signal path γs1, receiving signals proportional to the phase difference Δφ symmetric with respect to the central receiving channels, additionally amplifying these signals into the square of the sequence number of the symmetric channels once, summing the received signals and calculating by the distance formula to the radiation source, pairwise removal from each edge of the AP N / 2 antenna elements, where N is much smaller than M, and they are approximately evenly placed on the longitudinal axis of the AR within the Fresnel zone ix of undeployed elements, where i = 0, 1, ..., (M- N) / 2, determine the range and angular position of the placed elements, calculated from the measured coordinates of the anchor points of the placed elements to the longitudinal axis of the AR and thus determine their serial numbers jn, phased the channels of the n-placed antenna elements, where n = 0, 1 , ..., N / 2, preliminary estimate the distance r1 to the radiation source, taking into account the phase values of the received signal on the remote elements according to the formula

where c is the speed of light;

M '= 2max | j _n |;

Δφ _i = φ _i -φ _-i and Δφ _n = φ _n -φ _-n are the phase differences of the i-th and n-th symmetric relative to the Central receiving channels, respectively;

φ _{± i} and φ _{± n} are the phase difference of the signals received by the ± i-th and ± n-th and central antenna elements, respectively;

- база АР, образованной из (М+1) элементов, уточняют вектор координат R_h={r_h,γ_sh} и устраняют неоднозначность определения дальности до источника радиоизлучения на основе алгоритма стохастической аппроксимации

- the base of the AR formed from (M + 1) elements, specify the coordinate vector R _h = {r _h , γ _sh } and eliminate the ambiguity of determining the distance to the source of radio emission based on the stochastic approximation algorithm

R _{h + 1} = R _h -µ {g (R _h ) -g (R _h -ΔR _h )} ΔR _h ,

where µ = const;

среднеквадратическая ошибка (СКО) оценки фазы при h-й итерации поиска вектора R_h;

standard error (RMS) of the phase estimate during the hth iteration of the search for the vector R _h ;

и

- реальное и расчетное значения разности фаз в n-x (i-x) вынесенных (не вынесенных) каналах АР;

and

- real and estimated values of the phase difference in nx (ix) remote (not remote) channels of the AR;

ΔR _h is a random increment of the vector R _h = {r _h , γ _sh } with average values of the parameters r _h and γ _sh equal to r ₁ and γ _s1 , and the ranges of possible values Δ _r1 and 3δ _γs1, respectively;

r _ds = (M ') ² λ _0/2 - radius of the far zone for the three components with AP base L';

q _s is the signal-to-noise ratio (patent of the Russian Federation 2231806, IPC G01S 5/08).

The disadvantages of this method are the relative complexity with insufficiently high accuracy and reliability of determining the range, as well as the presence of a measured base, which is determined by the size of the antenna array.

The technical result of the invention is to increase the accuracy and reliability of determining the range to the radiation source of two or more frequencies using a single receiving station.

The technical result is achieved by the fact that in the method for determining the distance to an object with a radiation source of signals with different frequencies, which consists in simultaneously receiving at least two signals with different frequencies and then measuring the phases of the received signals relative to the phases of the signals of the reference generator, the following new operations are introduced: they convert the measured phase value of each signal in the digital value of the time interval between the signal of the reference oscillator and the received signal, and the distance is calculated according to the formula:

Where

b _s - residual images (interpreted as distance values proportional to the measured phase values);

m _s - comparison modules, by which we mean the wavelengths of the received signals.

Figure 1 presents a diagram of a device explaining the implementation of the proposed method for determining the distance to an object with a radiation source of signals with different frequencies. Figure 2 shows a graphical diagram illustrating a method for determining the range.

To determine the distance to object 1, signals are received at frequencies f ₁ and f ₂ from a radiation source located at object 1. Receiver 2 simultaneously receives signals at frequencies f ₁ and f ₂ . A similar receiver is used to receive signals transmitted at frequencies f ₁ and f ₂ by the GLONASS satellite radio navigation system (SRNS). A possible implementation of the method in the case of receiving signals from a radiation source of more than two frequencies. The received signals are fed to digital phase difference meters (3, 4). The phase difference is measured relative to the phases of the signals of the reference oscillator 5 connected to digital meters (3, 4) of the phase difference, which include meters (6, 7) of time intervals. The outputs of the time intervals meters (6, 7) are connected to the start and stop inputs of the counters 8 and 9, respectively, which count the number of measured frequency pulses coming from the generator 10 during a time equal to the delay time of the received signal relative to the reference one. All the data obtained is sent to the computing device 11, which performs distance calculation using these data using the formula of the Chinese remainder theorem:

for the case of using two comparison modules m ₁ and m ₂ , which use wavelengths λ ₁ and λ ₂ corresponding to the frequencies f ₁ and f _{2 of the} radiation source. The output of the generator 10 pulses of the measured frequency is connected to the combined third inputs of the counters 8 and 9.

To clarify the calculation of the range value using the remainder theorem, the measurements themselves should be interpreted in terms and concepts of the mathematical theory of finite fields.

In this case, the distance between the object 1 (for example, a satellite) and the receiver is the sum of the number of complete cycles plus a fractional cycle multiplied by the wavelength of the measured frequency, for example, the carrier.

The relationship connecting the distance to the object with the phase of the carrier can be written as follows:

where p is the range

λ is the carrier wavelength,

ϕ is the measured phase value,

k is the unknown number of integer wavelengths that fit in the distance to the object.

A fundamentally new approach for determining the range in non-request mode can be implemented using the mathematical apparatus of the theory of finite fields [2, 3]. But for this it is necessary to use the following proposed model of interpretation of mathematical and physical terms and concepts that form the basis of the theory of finite fields [2, 3] and the theory of radio engineering measurements [1].

When measuring at several frequencies, the measurement model can be represented in terms of the mathematical theory of finite fields (TCH). In this case, phase measurements are represented by residual images, and wavelengths are perceived as comparison modules.

The well-known recovery algorithms that make it possible to carry out the inverse transition from the modular representation of the calculation result to the traditional positional one are based on the Chinese remainder theorem [2, 3].

The Chinese remainder theorem states that any non-negative number x that does not exceed the product value of all the comparison modules m ₁ × m ₂ × .... × m _n can be uniquely restored if its residues from these modules are known.

A mathematical model for determining x based on residues b ₁ , b ₂ , ..., b _n and its analogue for processing radio engineering measurements based on measured phases δr ₁ , δr ₂ , ..., δr _n

When presenting measurement results based on TCH For radio engineering measurements based on CTI (phase measurements) x - measurement result r is the distance to the radiation object bi remnant images δr _i - measured phase values m _i - comparison modules λm _i - wavelengths Traditional Comparison System Comparison system in the proposed physical and mathematical interpretation x≡b ₁ (mod m ₁ ) r≡δr ₁ (mod λm ₁ ) x≡b ₂ (mod m ₂ ) r≡δr ₂ (mod λm ₂ ) ... ... x≡b _n (mod m _n ) r≡δr _n (modλm _n )

The solution to this problem can be illustrated by a specific example, when three frequencies are emitted.

If the radiation occurs at the frequencies L1, L2, L5, then the wavelengths are 19, 24 and 25 cm.

The task is posed as follows. It is required to find x satisfying the comparison system:

x≡b ₁ (mod m ₁ ),

x≡b ₂ (mod m ₂ ),

x≡b ₃ (mod m ₃ )

with the following values of the comparison modules m ₁ = 19, m ₂ = 24,

m ₃ = 25 and residues b ₁ = 9, b ₂ = 16, b ₃ = 0.

Using the formula of the Chinese remainder theorem, we obtain

1) M ₁ = m ₂ × m ₃ = 600; 600 × M ^′ ₁ ≡1 (mod 19), M ^′ ₁ = 7;

2) M ₂ = m ₁ × m ₃ = 475; 475 × M ^′ ₂ ≡1 (mod 24), M ^′ ₂ = 19;

3) M ₃ = m ₁ × m ₂ = 456; 456 × M ^' ₃ ≡1 (mod 25), M ^' ₃ = 21;

X = 9 × 600 × 7 + 16 × 475 × 19 + 0 × 456 × 21 = 182200≡11200 (mod 11400).

As a result of calculations, it was found that the range to the radiation object is 11,200 conventional units. If pseudorange data expressed in meters are aligned with the results of phase measurements, then the final value of X, taking into account the disclosure of uncertainty, is 11,200 meters.

This technique can be extended to a larger number of modules (wavelengths).

As a result, we obtain the following positive effect.

1. To directly determine the range in non-request mode, one autonomous operating receiver is sufficient.

2. Signals are received on an omnidirectional antenna, so there is no need to determine the bearing on the radiation object.

3. The range is determined by simultaneous measurements of the phase difference of the received signals and the reference generator.

4. The accuracy of range measurement in non-request mode approaches the accuracy of interrogation systems.

List of sources of information

1. Theoretical foundations of radar. / Ed. V.E.Dulevich. - M: Soviet Radio, 1978, p.217-220.

2. Liddle R., Niederreiter G. Finite Fields. In 2 volumes. Per from English. - M .: Mir, 1988 .-- 882 p.

3. Kukushkin S.S. Theory of finite fields and computer science. T.1., M.: Ministry of Defense of Russia, 2003 .-- 278 p.

Claims (1)

A method for determining the distance to an object with a radiation source of signals with different frequencies, which consists in simultaneously receiving at least two signals with different frequencies and then measuring the phases of the received signals relative to the phases of the signals of the reference generator, characterized in that they convert the measured phase value of each signal into a digital value the time interval between the signal of the reference generator and the received signal, and the distance is calculated by the formula:

Where

b _s - residual images (interpreted as distance values proportional to the measured phase values);
m _s - comparison modules, by which we mean the wavelengths of the received signals.

Images