RU2519593C2 - Phase direction finder - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: invention can be used in radio interception, radio monitoring at searching of special electronic information intercept devices to determine location of a radio source (RS). A phase direction finder includes three antennae, three receiving paths, three phase detectors, a frequency metre, an interception unit, a combiner, bearing determining unit, and direction determining unit, which are connected to each other in a certain way.

EFFECT: determination of direction at RS and length at relatively small distances.

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Description

The invention relates to the field of radio engineering and can be used in radio intelligence, radio monitoring, when determining the location of special electronic devices for intercepting information (SEUPI).

A known device for determining the position of electromagnetic radiation sources (analogue) see US patent No. 4383301 IPC G01S 5/02, 7/04, containing an antenna array for receiving radiation and generating the corresponding signals, a receiving system for measuring the phase and intensity of each received signal, device signal processing for processing coherent phase and amplitude signals and reproducing directions to the source of received radiation.

A radio direction finder is also known by application No. 1333546, UK, IPC G01S 3/48, 3/10 (analogue), which incorporates an antenna array consisting of several pairs of uniformly spaced antenna elements and a processing device. The signals from each pair of antenna elements are fed to phase discriminators that measure the phase difference. The phases of the signals obtained from the four most distant pairs of antenna elements are converted into four binary codes and averaged by summing. The logic device eliminates the ambiguity and generates a binary signal characterizing the angle of arrival of the electromagnetic wave.

The disadvantage of analogues is that with their help, it is possible to determine only the bearing to the source of radio emission (IRI), while to determine the location (bearing and range), it is necessary to use at least two devices spaced a relatively large distance.

Of the known devices, the closest in technical essence to the claimed (prototype) is a phase direction finder, a diagram of which is shown in Figure 8.1 p. 195 V.A. Cherdyntsev "Radio Engineering Systems". Minsk, “Higher School”, 1988, 369 pp.

The known phase direction finder contains the first and second antennas spaced a certain distance, the first and second receiving paths connected by the inputs to the first and second antennas, respectively, and the first phase detector connected by one input to the output of the first receiving path, the second input to the output of the second receiving path, and the output of the phase detector is the output of the direction finder.

The principle of measuring the angular coordinates of radiation sources or reflection of radio waves in a known direction finder is implemented by comparing the signals received by the antennas in the phase detector, while the voltage at the output of the phase detector is proportional to the angular position of the direction finding object.

The disadvantage of the prototype is the inability to determine the distance to SEPI, because in order to determine the location of the SEPI it is necessary to use at least two points of reception, spaced over considerable distances.

At the same time, the actual task is to determine the location of the SEAPI in one reception point at relatively small ranges.

The analysis shows that this problem can be solved by the goniometric-distance measuring method based on measuring phase shifts in the elements of antenna pairs and forming a narrow report area of the measured parameters (bearing and range) by processing the signal taking into account the sphericity of the wave front and on the basis of crossing and combining procedures.

The problem to be solved by the claimed device is to form a narrow area of the report of the measured parameters (bearing and range) by processing the signal taking into account the sphericity of the wave front and based on the procedures of intersection and association.

The technical result, the achievement of which the invention is directed, is to determine the range to Iran.

The technical result is achieved by the fact that in the known phase direction finder containing the first and second antennas spaced a certain distance, the first and second receiving paths connected by the inputs to the first and second antennas, respectively, and the first phase detector connected by the first input to the output of the first receiving path, and a second antenna, a third receiving path, connected by an input to a third antenna, a second phase detector connected by a single input to the output of the second receiving about the path, and another input with the output of the third receiving path, a third phase detector connected by one input to the output of the first receiving path, and another input with the output of the third receiving path, a frequency meter connected by the input to the output of the second receiving path, the intersection unit connected by one input with the output of the first phase detector, and another input with the output of the second phase detector, the combining unit associated with one input with the output of the first phase detector, and another input with the output of the second phase detector, the unit is determined a bearing, connected by one input to the output of the intersection unit, a second input with the output of the combining unit, and a third input with the output of the third phase detector, a range determination unit connected by one input to the output of the frequency meter, the second input to the output of the intersection unit, and the third input to the output of the unit determination of the bearing, and the outputs of the bearing detection unit and the range determination unit are the outputs of the phase direction finder.

The essence of the invention is to obtain a narrow range of bearing and range taking into account the sphericity of the wave front from the signals of intersection and association, which are formed from the input signals arriving at the antennas, are rigidly connected to this area and the subsequent determination of the distance to the IRI.

The figure 1 presents the structural diagram of the phase direction finder. In figures 2-7 shows the dependence of the amplitudes of the signals from the angle of deviation for various points of the circuit. In figures 8-11 presents statistical indicators of quality and the results of simulation of the direction finder.

The phase direction finder (figure 1) contains the first 1.1, second 1.2 and third 1.3 antennas located on the same line and spaced apart by distance d, the first 2.1, second 2.2 and third 2.3 receiving paths, the first 3.1 and second 3.2 phase detectors, frequency counter 4, third phase detector 3.3, intersection unit 5, combining unit 6, bearing detecting unit 7, range determining unit 8.

The third antenna 1.3, the third receiving path 2.3 and the second phase detector 3.2 make it possible to obtain an additional voltage proportional to the difference at the output of the phase detector. phases between the central and extreme antennas, which is necessary to take into account the sphericity of the wave front when processing signals.

Frequency 4 allows you to determine the frequency of the IRI signal based on a panoramic analysis of the energy spectrum.

The third phase detector 3.3 makes it possible to obtain a voltage proportional to the phase difference between the signals received by the extreme antennas necessary for fixing the bearing to the normal to the base of the antenna system.

The intersection block 5 and the union block 6 allows you to select a narrow reference area of the measured parameters, both for determining the bearing itself and for calculating the distance to the radiation source.

Bearing determination unit 7 provides the output of the IRI bearing signal based on the current value of the angle, measured, for example, from the direction to the North at the moment when the antenna base is normal to the direction to the radiation source.

Ranging unit 8 allows you to calculate the distance to the radiation source using the signal from the output of block 5, which carries information about the range, the measured frequency value from the output of the frequency counter 4 and the bearing signal from the output of the bearing detection unit 7, which is necessary to determine when the IRI is in the direction normals to the base of the antenna system and range calculation.

Range finder direction finder operates as follows.

The simulation was performed for the position of the IRI at an angle β, measured between the direction to the central antenna 1.2 and the direction to the North. Angle scanning is performed with a resolution of one degree

Antenna elements 1.1, 1.2, 1.3, which are taken as elements in the form of an active vibrator-reflector with specific parameters and an analytical task, adopted a harmonic signal unmodulated with fully known parameters, where a random process with a normal distribution of instantaneous values, zero mean and given dispersion. Information on the range and bearing of the IRI is introduced into the initial phase of the input signals relative to the middle antenna. The choice of sampling rate is arbitrary based on minimizing the error in determining the range

The instantaneous values of the received signals at the outputs of the antennas 1.1, 1.2 and 1.3 can be represented as:

Here, n ₁ (t), n ₂ (t), n ₃ (t) are the intrinsic noise of the respective receivers, converted to the inputs; φ ₁ , φ ₂ , φ ₃ - the initial phases of the signals, carrying information about the bearing β and the distance R to the source of radio emission relative to the central antenna; F ₁ , F ₂ , F ₃ - normalized radiation patterns of the respective antennas in the direction θ; U _m1 , U _m2 , U _m3 - signal amplitudes; ω = 2πf is the circular frequency of the signal, where f is its cyclic frequency.

Given that the distance from the central antenna to the radiation source is much larger than the distance between the antennas, the antennas are weakly oriented and equally oriented, we can take the values of the normalized diagrams to be the same F ₁ (θ) = F ₂ (θ) = F ₃ (θ) = F (θ). We can also assume the same signal amplitudes U _m1 = U _m2 = U _m3 = U _m .

In the radio receiving paths 2.1, 2.2, 2.3 of the corresponding channel, the signals are converted and amplified at the radio frequency. In this case, the same condition is the same gain and the same phase-frequency characteristics in the passband. The type of signals at the outputs of the antennas at the time of determining the bearing and range is presented in figure 2 in the coordinates of the amplitude - time.

Here, curve 9 corresponds to U _1.1 (t), 10 to U _1.2 (t) and U _1.3 (t). The signals U ₂ (t) and U ₃ (t) coincide, since they are presented at the time when the antenna base is normal to the direction of the radio source, i.e. φ ₁ = φ3, and the signal amplitude is much larger than the noise level U _m >> n (t).

The temporal shift of the curves indicates the presence of a phase shift between the signals received by the central 1.2 and extreme antennas 1.1 and 1.3 Ф _1.2 = Ф _3.2 ≠ 0, and the “broken” character is about discretization.

Signals (1) and (3) from the outputs of the first 2.1 and third 2.3 receiving paths are fed to the first inputs of phase detectors 3.1 and 3.2, respectively. The signal (2) from the output of the second receiving path 2.2 is a reference signal and is fed to the second inputs of the phase detectors 3.1 and 3.2.

The signals at the outputs of the phase detectors 3.1 and 3.2, respectively, will be:

where Ф _1,2 , Ф _3,2 are phase shifts between the signals received by the central 1.2 and extreme antennas 1.1 and 1.3, respectively.

The signals from the outputs of the first 2.1 and third 2.3 receiving paths are also fed to the first and second inputs of the third phase detector 3.3, the signal at the output of which takes the form similar to (4) and (5):

where Ф _1,3 is the phase shift between the signals received by the extreme antennas 1 and 3.

The signals corresponding to (4), (5) and (6) at the output of the phase detectors 3.1, 3.2, 3.3, are presented in figure 3.

Here, curves 11, 12, 13 represent the signals from the outputs of the phase detectors 3.1, 3.2, and 3.3, respectively. The horizontal axis corresponds to the current angle θ in degrees, the vertical axis corresponds to the normalized amplitude of the signal, proportional to the phase shifts.

The cyclical character caused by the “phase drop” multiple of 2π is characteristic, which can lead to ambiguity in the choice of the parameter measurement region, as well as the behavior of the curves in the vicinity of the bearing point, which ensures the formation of signs of determination of this region.

Attention should be paid to the modulation of the signals by the radiation pattern of the antenna F (θ), which eliminates the ambiguity due to reception on the side lobes.

The following is the process of forming the measurement (reference) area of the parameters and, above all, the bearing. To form a narrow range of reference parameters (bearing and range) and improve the measurement accuracy, an intersection block 5, a combining block 6, and a signal (6) from the output of the third phase detector (block 3.3) are used. Signals (4) and (5), proportional to the phase shifts Ф _1,2 and Ф _3,2 , are fed to the first and second inputs of the intersection block 5, which compares signals (4) and (5) in accordance with the properties of the intersection procedure, highlighting common areas. Block intersection 5 implements the algorithm:

The same signals (4) and (5) are fed simultaneously to the first and second inputs of the combining unit 6, the voltage at the output of which, in accordance with the properties of this procedure, will implement the following algorithm:

The type of signals (7), (8) and (6) is presented in figure 4.

Here, these are curves 14, 15, 13, respectively, in the sector of angles 0-180 °.

The analysis shows that, based on the properties of the procedures used, the union signal (15) “covers” the intersection signal (14) and the inequality U ₆ (θ)> U ₅ (θ) almost always holds except for the region (point), where U ₆ (θ) = U ₅ (θ) and two more points where, due to the cyclic nature of the cosine, this inequality is violated. However, these points during further processing can be excluded from the analysis due to amplitude differences.

To explain the process of forming the measurement region, we consider the behavior of the considered dependencies in the vicinity of the bearing, shown in figures 5, 6.

In figure 5, the plan in the bearing area shows the signals (4) and (5) at the outputs of the phase detectors (blocks 3.1, 3.2), proportional to the phase shifts Ф _1,2 and Ф _3,2 , curves 11 and 12, between the central and extreme antennas , as well as the signal (6) at the output of block 3.3, proportional to the phase shift Ф _1.3 , curve 13, between the extreme antennas. The bearing on the IRI for example is taken equal to 65 °.

As can be seen from figure 5 at the bearing point there is an equality of the phase shifts Ф _1,2 (curve 11) and Ф _3,2 (curve 12). Moreover, Ф _1,2 ≠ 0 and Ф _3,2 ≠ 0 and depend on the range of R. The value of Ф _1,3 (curve 13) at the bearing point is maximum. The behavior of the dependences of the phase shifts Ф _1,2 , Ф _3,2, and Ф _1,3 in the bearing area makes it advisable to use the detection-measurement algorithm based on the combined use of crossing procedures (5) and combining (6) to highlight a narrow bearing range and range .

Signals (4) and (5), proportional to the phase shifts Ф _1,2 and Ф _3,2 , are fed to the first and second input of the intersection unit 5 and to the first and second input of the combining unit 6.

The figure 6 presents the output signals of the intersection block 5 (curve 14), the combining block 6 (curve 15) and the curve 13 from figure 5 is repeated for comparison — the signal (6) at the output of block 10 is proportional to the phase shift Ф _1.3 between the extreme antennas .

As can be seen from the figures, the intersection block 5 generates a signal with an extremum at the bearing point in the form of a sharpened peak (figure 6, curve 14). The amplitude of this extremum is determined by the distance to the IRI, since this is the point of coincidence of the phase shifts of the signals between the central and extreme antennas. Therefore, the signal (7) from the output of the intersection unit 5 is supplied to the range determination unit 8 to its second input to calculate this range.

On the contrary, the combining unit 6 generates a signal (8) with a flat top (Figure 6, curve 15), which coincides with the intersection signal (7) only at the bearing point and differs significantly outside this point.

Thus, the combined use of crossing and combining procedures makes it possible to single out a narrow reference range of the measured parameters, which means to increase the accuracy of determining the range and bearing.

To separate the hypotheses about a spherical or plane wave front, a signal (6) from the output of the third phase detector 3.3 (curve 13, figure 5, 6) is used, more precisely, the difference between this signal and signal (7) from the output of the intersection unit 5.

With increasing distance to the IRI, the amplitude of the intersection signal (7) at the bearing point increases, tending in the limit to the amplitude of the signal (6) from the output of the third phase detector 3.3. The difference, respectively, decreases. This difference is formed in the bearing determination unit 7 in the form:

where C≥1, a threshold coefficient, the value of which depends on the required quality indicators of detection-measurement.

Thus, the intersection unit 5 fixes the equality of the phase shifts Ф _1,2 and Ф _3,2 in the bearing direction together with the combining unit 6. At the output of the bearing detecting unit 7, a signal of the bearing of the radiation source is generated based on the current value of the angle, measured, for example, from directions to the North. This signal is generated at the moment when the antenna base is normal to the direction to the radiation source when the condition:

The first threshold U _P1 is selected based on the far boundary of the desired field of view in range R _max and a given noise level of the receiver. The second threshold U _P2 is selected in accordance with the near boundary of this zone R _min . The choice of R _min and R _max is associated with an analysis of the dependences of the phase shift on the relative range R / λ for fixed and different relative bases d / λ calculated by the formula:

for given d and λ, taking into account the features of the problem of determining the location of the IRI.

In the study of dependence (11), it can be seen that the non-linear section should be considered as the working section, the boundary of which on the side of large R / λ is determined by the parametric sensitivity of the applied range estimation method, and on the side of small R / λ by physical conditions and the permissible error.

The bearing signal from the output of the bearing detecting unit 7 is fed to the input of the range determining unit 8 at the moment the radiation source is in the normal direction to the base of the antenna system and, at the same time, is fed to the direction finder output as a measured IRI parameter.

To determine the frequency, the signal of the reference channel from the output of the receiving path 2.2 is fed to a frequency meter 4, which determines its frequency by the maximum of the envelope of the signal spectrum (figure 7, curve 16).

From the output of the frequency counter 4, the found value of the frequency F * is supplied to the third input of the ranging unit 8.

The range determination unit 8 calculates the range to the IRI using the signal (7) from the output of the intersection unit 5 carrying information about the range and the measured value of the frequency F * from the output of the frequency counter 4. The calculation is made when the radiation source is in the normal direction to base of the antenna system (in the direction of the bearing θ = β). This moment is determined by the arrival of the bearing signal from the output of the bearing detecting unit 7 to the third input of the ranging unit 8. The range estimate R * is given as a measured parameter. It can be shown that the calculated ratio implemented in block 8 has the form:

where a is the ratio of the distance between the antenna elements to the wavelength.

The figure 8 presents the output signals of the units for determining the range and bearing in polar coordinates, where 17 is the calculated range; 18 - bearing; 19 - location of the radiation source at the intersection of the lines of bearing and range; 20 is a normalized radiation pattern of an antenna element.

To assess the effectiveness of the proposed phase direction finder circuit, it is necessary to determine statistical quality indicators based on simulation.

The study of the circuit operability showed that, when detecting and measuring the frequency and bearing under noise conditions, the most critical is the detection of the bearing. In addition, it is the value of the bearing voltage, which is formed as the intersection of the phase shifts of the receiving channels relative to the reference channel, that is threshold when the viewing range is limited in range to separate hypotheses about the shape of the front of the incoming wave. The same voltage is used as a parameter in the calculated ratio to determine the range. Therefore, due to these circumstances, the following probabilistic indicators are taken as quality indicators:

1. The probability of false alarms (false alarms) when determining the bearing in the conditions of action of only noise _RT ;

2. The probability of correct detection of the bearing P _OB ;

3. The relative measurement error of the range δ _R.

.The considered probabilistic indicators were defined as probabilities in the frequency sense, i.e. as the ratio of the number of positive outcomes n, determined by the counter at the output of the bearing determination unit 7 to the total number of experiments

.

The position of the antenna system was fixed in the direction of the IRI. Accepted signal and noise models are discussed earlier.

Further, figures 9-11 show the characteristics of quality indicators obtained as a result of modeling.

.The smoothed dependence of the probability of false alarm when detecting the bearing on the relative detection threshold is shown in figure 9, curve 21 in the form

.

Here U _then - the value of the first threshold voltage; σ _W - the rms value of the noise at the outputs of the receivers of the processing channels. It is assumed in the model that σ _w1 = σ _w2 = σ _w3 = σ _w . Noises are not correlated.

представлены на фигуре 10. Здесь кривая 22 соответствует Р_ЛТ=10^-2, а кривая 23 - Р_ЛТ=4·10^-2; U_c - амплитуда сигнала на входе канала.The obtained dependence makes it possible to choose the detection threshold U _П1 for implementing relation (10) at a given noise level. The dependence of the probability of correct detection on the signal-to-noise ratio at a fixed threshold (P _LT = const) in the form

are presented in figure 10. Here, curve 22 corresponds to P _LT = 10 ^-2 , and curve 23 - P _LT = 4 · 10 ^-2 ; U _c - the amplitude of the signal at the input of the channel.

As can be seen from the figure, guaranteed detection of the bearing in the proposed scheme is possible with a signal-to-noise ratio of more than five.

The dependence of the relative error in determining the range was determined as:

- среднее значение дальности, найденное по результатам N опытов для каждого фиксированного отношения сигнал/шум на выходе.Here R ₀ is the true value of the range,

- the average value of the range found from the results of N experiments for each fixed signal-to-noise ratio at the output.

This dependence is presented in figure 11, curve 25.

The figure also shows the dependence of the measured range on the signal-to-noise ratio, curve 24. In this case, the vertical axis is graduated in meters. Line 26 corresponds to the true range value.

As follows from figure 11, acceptable values of the relative error of range measurement are achieved when the signal-to-noise ratio is more than ten.

Thus, the simulation results confirm the efficiency, effectiveness and feasibility of the proposed direction finder.

The possibility of practical implementation also follows from the fact that the circuit can be built on typical, well-known and technologically advanced elements. For example:

Antennas 1.1, 1.2, 1.3 - directional, can be selected of various types, depending on the frequency range and the tactical and technical requirements for the direction finder. In the simplest case, antennas of the vibrator-reflector type can be used, as in the example under consideration, as described in [G.Z. Eisenberg, V.G. Yampolsky, O.N. Tereshin. VHF antennas. Part 1. - M. "Communication", 1977], p.188, figure 13.40;

The receiving paths 2.1, 2.2, 2.3 - can be built according to the standard scheme of radio communication or radar receivers with an output at an intermediate frequency as described in [M.K. Belkin, V.T. Belinsky, Yu.L. Mazor et al. A guide to the educational design of receiving amplifying devices. K., "Higher School", 1988.] p. 405, figure 14.4;

Phase detectors 3.1, 3.2, 3.3 - can be implemented as balanced phase detectors described in [M.K. Belkin, V.T. Belinsky, Yu.L. Mazor et al. A guide to the educational design of receiving amplifying devices. K., "Higher School", 1988] p. 252, figure 9.31c;

Frequency 4 - can be implemented according to the scheme of an electronically counted frequency counter as described in [V.P. Bobrovsky, V.I. Kostenko, V.M. Mikhalenko et al. Handbook of circuitry for an amateur. Ed. V.P. Borovsky. - K: Tekhnika, 1989] p. 388, figure 18.6;

Intersection block 5, union block 6 - can be built on the basis of adders, subtracting devices and module computing devices [Gordienko V.I., Dubrovsky S.E., Ryumshin R.I., Fenev D.V. Universal multifunctional structural element of information processing systems. / Electronics / Izv. Universities, No. 3, 1998]. Adders and subtractors, on the basis of which the intersection and combining unit is implemented, can be performed according to the usual scheme of amplifiers with two inputs or with direct and inverse inputs as described in [A.G. Alekseenko. The use of precision analog integrated circuits. - M., Radio and communications 1981] p.77, figure 3.2. Module computing devices can be implemented according to the scheme of a half-wave rectifier on operational amplifiers as described in [V.P. Bobrovsky, V.I. Kostenko, V.M. Mikhailenko et al. Handbook of circuitry for a radio amateur. Ed. V.P. Bobrovsky. - K: Tekhnika, 1989] p. 241, figure 12.4;

Bearing determination unit 7 - a logical device that performs the comparison operation with a threshold voltage, can be implemented using comparators based on operational amplifiers according to the scheme described in [A.P. Golubkov, A.D. Dalmatov, A.P. Lukoshkin et al. Design of radar receiving devices. Ed. M.A. Sokolova. - M., Higher. Shk., 1984] p. 141, figure 1.36;

The range determination unit 8 is a computing device that performs the simplest mathematical transformations that can be implemented according to the schemes described in [A.P. Golubkov, A.D. Dalmatov, A.P. Lukoshkin et al. Design of radar receiving devices. Ed. M.A. Sokolova. - M., Higher. Shk., 1984] p. 28-43 (figures 1.7., 1.10., 1.11., 1.35.);

Analysis of known technical solutions in the field of principles and devices of phase direction finding shows that the claimed invention, due to the essential features that determined the way to achieve a technical result, does not follow for a specialist explicitly from the prior art and meets the requirement of "inventive step".

In addition, the applicant has not found an analogue characterized by features identical to all the essential features of the claimed invention. The definition from the list of analogues of the prototype, as the closest in the totality of the features of the analogue, allowed us to identify distinctive features that are significant in relation to the technical result in the claimed object, which allows us to consider the claimed invention satisfying the criterion of "inventive novelty".

Claims (1)

A phase direction finder containing the first and second antennas spaced a certain distance, the first and second receiving paths connected by the inputs to the first and second antennas, respectively, and the first phase detector connected by the first input to the output of the first receiving path, and the second input to the output of the second receiving path characterized in that a third antenna, a third receiving path connected by an input to the third antenna, a second phase detector connected by one input to the output of the second receiving path, and the other input with the output of the third receiving path, the third phase detector connected by one input to the output of the first receiving path, and the other input by the output of the third receiving path, the frequency meter connected by the input to the output of the second receiving path, the intersection unit connected by one input to the output of the first phase detector, and another input with the output of the second phase detector, a combining unit connected by one input to the output of the first phase detector, and by another input with the output of the second phase detector, the bearing detection unit, connected by one it has an input with the output of the intersection unit, a second input with the output of the combining unit, and a third input with the output of the third phase detector, a range determination unit connected by one input to the output of the frequency meter, a second input with the output of the intersection unit, and a third input with the output of the bearing detection unit, and the outputs of the bearing detection unit and the range determination unit are the outputs of the phase direction finder.

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